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Fixed Wing Fighter Aircraft
Flight Performance
Part I
SOLO HERMELIN
Updated: 04.12.12
28.02.15
1
http://www.solohermelin.com
Table of Content
SOLO
Fixed Wing Aircraft Flight Performance
2
Introduction to Fixed Wing Aircraft Performance
Earth Atmosphere
Aerodynamics
Mach Number
Shock & Expansion Waves
Reynolds Number and Boundary Layer
Knudsen Number
Flight Instruments
Aerodynamic Forces
Aerodynamic Drag
Lift and Drag Forces
Wing Parameters
Specific Stabilizer/Tail Configurations
Table of Content (continue – 1)
SOLO
3
Specific Energy
Aircraft Propulsion Systems
Aircraft Propellers
Aircraft Turbo Engines
Afterburner
Thrust Reversal Operation
Aircraft Propulsion Summary
Vertical Take off and Landing - VTOL
Engine Control System
Aircraft Flight Control
Aircraft Equations of Motion
Aerodynamic Forces (Vectorial)
Three Degrees of Freedom Model in Earth Atmosphere
Comparison of Fighter Aircraft Propulsion Systems
Fixed Wing Fighter Aircraft Flight Performance
Table of Content (continue – 2)
SOLO
Fixed Wing Fighter Aircraft Flight Performance
4
Parameters defining Aircraft Performance
Takeoff (no VSTOL capabilities)
Landing (no VSTOL capabilities)
Climbing Aircraft Performance
Gliding Flight
Level Flight
Steady Climb (V, γ = constant)
Optimum Climbing Trajectories using Energy State
Approximation (ESA)
Minimum Fuel-to- Climb Trajectories using Energy State
Approximation (ESA)
Maximum Range during Glide using Energy State
Approximation (ESA)
Aircraft Turn Performance
Maneuvering Envelope, V – n Diagram
F
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Table of Content (continue – 3)
SOLO
Fixed Wing Fighter Aircraft Flight Performance
5
Air-to-Air Combat
Energy–Maneuverability Theory
Supermaneuverability
Constraint Analysis
Aircraft Combat Performance Comparison
References
F
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SOLO
This Presentation is about Fixed Wing Aircraft Flight Performance.
The Fixed Wing Aircraft are
•Commercial/Transport Aircraft (Passenger and/or Cargo)
•Fighter Aircraft
Fixed Wing Fighter Aircraft Flight Performance
Return to Table of Content
7
Percent composition of dry atmosphere, by volume
ppmv: parts per million by volume
Gas Volume
Nitrogen (N2) 78.084%
Oxygen (O2) 20.946%
Argon (Ar) 0.9340%
Carbon dioxide (CO2) 365 ppmv
Neon (Ne) 18.18 ppmv
Helium (He) 5.24 ppmv
Methane (CH4) 1.745 ppmv
Krypton (Kr) 1.14 ppmv
Hydrogen (H2) 0.55 ppmv
Not included in above dry atmosphere:
Water vapor (highly variable) typically 1%
Gas Volume
nitrous oxide 0.5 ppmv
xenon 0.09 ppmv
ozone
0.0 to 0.07 ppmv (0.0 to 0.02
ppmv in winter)
nitrogen dioxide 0.02 ppmv
iodine 0.01 ppmv
carbon monoxide trace
ammonia trace
•The mean molecular mass of air is 28.97 g/mol.
Minor components of air not listed above include:
Composition of Earth's atmosphere. The lower pie
represents the trace gases which together compose
0.039% of the atmosphere. Values normalized for
illustration. The numbers are from a variety of
years (mainly 1987, with CO2 and methane from
2009) and do not represent any single source
Earth AtmosphereSOLO
8
Earth AtmosphereSOLO
The basic variables representing the thermodynamics state of the gas are the Density, ρ,
Temperature, T and Pressure, p.
SOLO
9
The Density, ρ, is defined as the mass, m, per unit volume, v, and has units of kg/m3
.
v
m
v ∆
∆
=
→∆ 0
limρ
The Temperature, T, with units in degrees Kelvin ( ͦ K). Is a measure of the average kinetic
energy of gas particles.
The Pressure, p, exerted by a gas on a solid surface is defined as the rate of change of normal
momentum of the gas particles striking per unit area.
It has units of N/m2
. Other pressure units are millibar (mbar), Pascal (Pa), millimeter of mercury
height (mHg)
S
f
p n
S ∆
∆
=
→∆ 0
lim
kPamNbar 100/101 25
==
( ) mmHginHgkPamkNmbar 00.7609213.29/325.10125.1013 2
===
The Atmospheric Pressure at Sea Level is:
Earth Atmosphere
10
Physical Foundations of Atmospheric Model
The Atmospheric Model contains the values of
Density, Temperature and Pressure as function
of Altitude.
Atmospheric Equilibrium (Barometric) Equation
In figure we see an atmospheric
element under equilibrium under
pressure and gravitational forces
( )[ ] 0=⋅+−+⋅⋅⋅− APdPPHdAg gρ
or
( ) gg HdHgPd ⋅⋅=− ρ
In addition, we assume the atmosphere to be a thermodynamic fluid. At altitude
bellow 100 km we assume the Equation of an Ideal Gas
where
V – is the volume of the gas
N – is the number of moles in the volume V
m – the mass of gas in the volume V
R* - Universal gas constant
TRNVP ⋅⋅=⋅ *
V
m
M
m
N == ρ&
MTRP /*
⋅⋅= ρ
Earth AtmosphereSOLO
( ) mmHginHgkPamkNmbar 00.7609213.29/325.10125.1013 2
===
Earth AtmosphereSOLO
We must make a distinction between:
- Kinetic Temperature (T): measures the molecular kinetic energy
and for all practical purposes is identical to thermometer
measurements at low altitudes.
- Molecular Temperature (TM): assumes (not true) that the
Molecular Weight at any altitude (M) remains constant and is
given by sea-level value (M0)
SOLO
12
T
M
M
TM ⋅= 0
To simplify the computation let introduce:
- Geopotential Altitude H
- Geometric Altitude Hg
Newton Gravitational Law implies: ( )
2
0 







+
⋅=
gE
E
g
HR
R
gHg
The Barometric Equation is ( ) gg HdHgPd ⋅⋅=− ρ
The Geopotential Equation is defined as HdgPd ⋅⋅=− 0ρ
This means that g
gE
E
g Hd
HR
R
Hd
g
g
Hd ⋅








+
=⋅=
2
0
Integrating we obtain g
gE
E
H
HR
R
H ⋅








+
=
Earth Atmosphere
13
Atmospheric Constants
Definition Symbol Value Units
Sea-level pressure P0 1.013250 x 105
N/m2
Sea-level temperature T0 288.15 ͦ K
Sea-level density ρ0 1.225 kg/m3
Avogadro’s Number Na 6.0220978 x 1023
/kg-mole
Universal Gas Constant R* 8.31432 x 103
J/kg-mole -ͦ K
Gas constant (air) Ra=R*/M0 287.0 J/kg--ͦ
K
Adiabatic polytropic constant γ 1.405
Sea-level molecular weight M0 28.96643
Sea-level gravity acceleration g0 9.80665 m/s2
Radius of Earth (Equator) Re 6.3781 x 106
m
Thermal Constant β 1.458 x 10-6
Kg/(m-s-ͦ K1/2)
Sutherland’s Constant S 110.4 ͦ K
Collision diameter σ 3.65 x 10-10
m
Earth AtmosphereSOLO
14
Physical Foundations of Atmospheric Model
Atmospheric Equilibrium Equation
HdgPd ⋅⋅=− 0ρ
At altitude bellow 100 km we assume t6he Equation
of an Ideal Gas
TRMTRP a
MRR
a
aa
⋅⋅=⋅⋅=
=
ρρ
/
*
*
/
Hd
TR
g
P
Pd
a
⋅=− 0
Combining those two equations we obtain
Assume that T = T (H), i.e. function of Geopotential Altitude only.
The Standard Model defines the variation of T with altitude based on experimental data.
The 1976 Standard Model for altitudes between 0.0 to 86.0 km is divided in 7 layers. In each
layer dT/d H = Lapse-rate is constant.
Earth AtmosphereSOLO
15
Layer
Index
Geopotential
Altitude Z,
km
Geometric
Altitude Z;
km
Molecular
Temperature T,
ͦ K
0 0.0 0.0 288.150
1 11.0 11.0102 216.650
2 20.0 20.0631 216.650
3 32.0 32.1619 228.650
4 47.0 47.3501 270.650
5 51.0 51.4125 270.650
6 71.0 71.8020 214.650
7 84.8420 86.0 186.946
1976 Standard Atmosphere : Seven-Layer Atmosphere
Lapse Rate
Lh;
ͦ K/km
-6.3
0.0
+1.0
+2.8
0.0
-2.8
-2.0
Earth AtmosphereSOLO
16
Physical Foundations of Atmospheric Model
• Troposphere (0.0 km to 11.0 km).
We have ρ (6.7 km)/ρ (0) = 1/e=0.3679, meaning that 63% of the atmosphere
lies below an altitude of 6.7 km.
( )
Hd
HLTR
g
Hd
TR
g
P
Pd
aa
⋅
⋅+
=⋅=−
0
00
kmKLHLTT /3.60

−=⋅+=
Integrating this equation we obtain
( )∫∫ ⋅
⋅+
=−
H
a
P
P
Hd
HLTR
g
P
PdS
S 0 0
0 1
0
( )
0
00
lnln
0
T
HLT
RL
g
P
P
aS
S ⋅+
⋅
⋅
−=
Hence
aRL
g
SS H
T
L
PP
⋅
−






⋅+⋅=
0
0
0
1
and










−








⋅=
⋅
1
0
0
0
g
RL
S
S
a
P
P
L
T
H
Earth AtmosphereSOLO
Stratosphere
Troposphere
17
Physical Foundations of Atmospheric Model
Hd
TR
g
P
Pd
Ta
⋅=− *
0
Integrating this equation we obtain
( )T
TaS
S
HH
TR
g
P
P
T
−⋅
⋅
−= *
0
ln
Hence
( )T
Ta
T
HH
TR
g
SS ePP
−⋅
⋅
−
⋅=
*
0
and
S
STTa
T
P
P
g
TR
HH ln
0
*
⋅
⋅
+=
∫∫ =−
H
HTa
P
P T
S
TS
Hd
TR
g
P
Pd
*
0
• Stratosphere Region (HT=11.0 km to 20.0 km).
Temperature T = 216.65 ͦ K = TT* is constant (isothermal layer), PST=22632
Pa
Earth AtmosphereSOLO
Stratosphere
Troposphere
18
Physical Foundations of Atmospheric Model
( )[ ] Hd
HHLTR
g
Hd
TR
g
P
Pd
SSTaa
⋅
−⋅+⋅
=⋅=− *
00
( ) ( ) PaPHPkmKLHHLTT SSSSSST 5474.9,/0.1
*
===−⋅−= 
Integrating this equation we obtain
( )[ ]∫∫ ⋅
−⋅+
=−
H
H SSTa
P
P S
S
SS
Hd
HHLTR
g
P
Pd
*
0 1
( )[ ]
*
*
0
lnln
T
ST
aSSS
S
T
HHLT
RL
g
P
P −⋅+
⋅
⋅
=
Hence ( )
aRL
g
S
T
S
SSS HH
T
L
PP
⋅
−








−⋅+⋅=
0
*
1
and










−





⋅+=
⋅
1
0
* g
RL
SS
S
S
T
S
aS
P
P
L
T
HH
Stratosphere Region (HS=20.0 km to 32.0 km).
Stratosphere
Troposphere
Earth AtmosphereSOLO
19
1962 Standard Atmosphere from 86 km to 700 km
Layer Index Geometric
Altitude
km
Molecular
Temperature
,
K
Kinetic
Temperature
K
Molecular
Weight
Lapse
Rate
K/km
7 86.0 186.946 186.946 28.9644 +1.6481
8 100.0 210.65 210.02 28.88 +5.0
9 110.0 260.65 257.00 28.56 +10.0
10 120.0 360.65 349.49 28.08 +20.0
11 150.0 960.65 892.79 26.92 +15.0
12 160.0 1110.65 1022.20 26.66 +10.0
13 170.0 1210.65 1103.40 26.49 +7.0
14 190.0 1350.65 1205.40 25.85 +5.0
15 230.0 1550.65 132230 24.70 +4.0
16 300.0 1830.65 1432.10 22.65 +3.3
17 400.0 2160.65 1487.40 19.94 +2.6
18 500.0 2420.65 1506.10 16.84 +1.7
19 600.0 2590.65 1506.10 16.84 +1.1
20 700.0 2700.65 1507.60 16.70
Earth AtmosphereSOLO
20
1976 Standard Atmosphere from 86 km to 1000 km
Geometric Altitude Range: from 86.0 km to 91.0 km (index 7 – 8)
78
/0.0
TT
kmK
Zd
Td
=
= 
Geometric Altitude Range: from 91.0 km to 110.0 km (index 8 – 9)
2/12
8
2
8
2/12
8
1
1
−













 −
−




 −
⋅−=













 −
−⋅+=
a
ZZ
a
ZZ
a
A
Zd
Td
a
ZZ
ATT C
kma
KA
KTC
9429.19
3232.76
1902.263
−=
−=
=


Geometric Altitude Range: from 110.0 km to 120.0 km (index 9 – 10)
( )
kmK
Zd
Td
ZZLTT Z
/0.12
99

+=
−⋅+=
Geometric Altitude Range: from 120.0 km to 1000.0 km (index 10 – 11)
( ) ( )
( )
( ) 





+
+
⋅−=






+
+
⋅−⋅=
⋅−⋅−−=
∞
∞∞
ZR
ZR
ZZ
kmK
ZR
ZR
TT
Zd
Td
TTTT
E
E
E
E
10
10
10
10
10
/
exp
ξ
λ
ξλ

KT
kmR
km
E

1000
10356766.6
/01875.0
3
=
×=
=
∞
λ
Earth AtmosphereSOLO
21
Sea Level Values
Pressure p0 = 101,325 N/m2
Density ρ0 = 1.225 kg/m3
Temperature = 288.15 ͦ K (15 ͦ C)
Acceleration of gravity g0 = 9.807 m/sec2
Speed of Sound a0 = 340.294 m/sec
Earth AtmosphereSOLO
Return to Table of Content
SOLO
Atmosphere
Continuum Flow
Low-density and
Free-molecular Flow
Viscous Flow Inviscid Flow
Incompressible Flow
Compressible Flow
Subsonic
Flow
Transonic
Flow
Supersonic
Flow
Hypersonic
Flow
AERODYNAMICS
Fixed Wing Aircraft Flight Performance
AERODYNAMICS
23
SOLO
Dimensionless Equations
Dimensionless Field Equations
(C.M.): ( ) 0
~~~~
=⋅∇+ u
t

ρ
∂
ρ∂
( ) ( )u
R
u
R
pG
F
uu
t
u
eer
~~~~1
3
4~~~~1~~~~1~~~
~
~
~
2


⋅∇∇+×∇×∇−∇−=







∇⋅+ µµρ
∂
∂
ρ(C.L.M.):
( ) ( )Tk
PRt
Q
uG
F
u
t
p
Hu
t
H
rer
∇⋅∇−+⋅+⋅⋅∇+=







∇⋅+
∂
∂ 11
~
~
~~~1~~~
~
~~~~
~
~
~
2
∂
∂
ρτ
∂
∂
ρ

(C.E.):
Reynolds:
0
000
µ
ρ lU
Re = Prandtl:
0
0
k
C
P p
r
µ
= Froude:
0
0
gl
U
Fr =
0/~ ρρρ = 0/
~
Uuu = gGG /
~
= ( )2
00/~ Upp ρ=
0/
~
lUtt =
2
0/
~
UCTT p=( )2
00/~ Uρττ =
2
0/
~
UHH =
2
0/
~
Uhh =
2
0/~ Uee = ( )2
00/~ Uqq ρ= ( )2
/
~
UQQ =
∇=∇ 0
~
l
0/~ ρρρ = 0/
~
Uuu = gGG /
~
= ( )2
00/~ Upp ρ=
0/
~
lUtt =
2
0/
~
UCTT p=( )2
00/~ Uρττ =
2
0/
~
UHH =
2
0/
~
Uhh =
2
0/~ Uee = ( )2
00/~ Uqq ρ= ( )2
/
~
UQQ =
∇=∇ 0
~
l
0/~ µµµ =
0/
~
kkk =
Dimensionless Variables are:
Reference Quantities: ρ0(density), U0(velocity), l0 (length), g (gravity), μ0 (viscosity),
k0 (Fourier Constant), λ0 (mean free path)
0/
~
λλλ =
Knudsen
l
Kn
0
0
:
λ
=
AERODYNAMICS
Return to Table of Content
24
SOLO
Mach Number
Mach number (M or Ma) / is a dimensionless quantity representing
the ratio of speed of an object moving through a fluid and the local
speed of sound.
• M is the Mach number,
• U0 is the velocity of the source relative to the medium, and
• a0 is the speed of sound
Mach:
0
0
a
U
M =
The Mach number is named after Austrian physicist and philosopher
Ernst Mach, a designation proposed by aeronautical engineer Jakob
Ackeret.
Ernst Mach
(1838–1916)
Jakob Ackeret
(1898–1981)
m
Tk
Mo
TR
a Bγγ
==0
• R is the Universal gas constant, (in SI, 8.314 47215 J K−1
mol−1
), [M1
L2
T−2
θ−1
'mol'−1
]
• γ is the rate of specific heat constants Cp/Cv and is dimensionless
γair = 1.4.
• T is the thermodynamic temperature [θ1
]
• Mo is the molar mass, [M1
'mol'−1
]
• m is the molecular mass, [M1
]
AERODYNAMICS
25
SOLO
Mach Number – Flow Regimes
Regime Mach mph km/h m/s General plane characteristics
Subsonic <0.8 <610 <980 <270
Most often propeller-driven and commercial turbofan aircraft with
high aspect-ratio (slender) wings, and rounded features like the
nose and leading edges.
Transonic 0.8-1.2
610-
915
980-1,470 270-410
Transonic aircraft nearly always have swept wings, delaying drag-
divergence, and often feature design adhering to the principles of
the Whitcomb Area rule.
Supersonic 1.2–5.0
915-
3,840
1,470–
6,150
410–1,710
Aircraft designed to fly at supersonic speeds show large differences
in their aerodynamic design because of the radical differences in the
behavior of flows above Mach 1. Sharp edges, thin airfoil-sections,
and all-moving tailplane/canards are common. Modern combat
aircraft must compromise in order to maintain low-speed handling;
"true" supersonic designs include the F-104 Starfighter, SR-71
Blackbird and BAC/Aérospatiale Concorde.
Hypersonic 5.0–10.0
3,840–
7,680
6,150–
12,300
1,710–
3,415
Cooled nickel-titanium skin; highly integrated (due to domination
of interference effects: non-linear behaviour means that
superposition of results for separate components is invalid), small
wings, such as those on the X-51A Waverider
High-
hypersonic
10.0–25.0
7,680–
16,250
12,300–
30,740
3,415–
8,465
Thermal control becomes a dominant design consideration.
Structure must either be designed to operate hot, or be protected by
special silicate tiles or similar. Chemically reacting flow can also
cause corrosion of the vehicle's skin, with free-atomic oxygen
featuring in very high-speed flows. Hypersonic designs are often
forced into blunt configurations because of the aerodynamic heating
rising with a reduced radius of curvature.
Re-entry
speeds
>25.0
>16,25
0
>30,740 >8,465 Ablative heat shield; small or no wings; blunt shape
AERODYNAMICS
26
SOLO
Different Regimes of Flow
Mach Number – Flow Regimes
AERODYNAMICS
Return to Table of Content
27
SOLO
- when the source moves at subsonic velocity V < a, it will stay inside the
family of spherical sound waves.
a
V
M
M
=





= −
&
1
sin 1
µ
Disturbances in a fluid propagate by molecular collision, at the sped of sound a,
along a spherical surface centered at the disturbances source position.
The source of disturbances moves with the velocity V.
- when the source moves at supersonic velocity V > a, it will stay outside the
family of spherical sound waves. These wave fronts form a disturbance
envelope given by two lines tangent to the family of spherical sound waves.
Those lines are called Mach waves, and form an angle μ with the disturbance
source velocity:
SHOCK & EXPANSION WAVES
AERODYNAMICS
28
SOLO
SHOCK & EXPANSION WAVES
M < 1
M = 1
M > 1
Mach Waves
AERODYNAMICS
29
SOLO
When a supersonic flow encounters a boundary the following will happen:
When a flow encounters a boundary it must satisfy the boundary conditions,
meaning that the flow must be parallel to the surface at the boundary.
- when the supersonic flow, in order to remain parallel to the boundary surface,
must “turn into itself” a Oblique Shock will occur. After the shock wave the
pressure, temperature and density will increase.
The Mach number of the flow will decrease after the shock wave.
SHOCK & EXPANSION WAVES
- when the supersonic flow, in order to remain parallel to the boundary surface,
must “turn away from itself” an Expansion wave will occur. In this case the
pressure, temperature and density will decrease.
The Mach number of the flow will increase after the expansion wave.
Return to Table of Content
AERODYNAMICS
30
SHOCK WAVES
SOLO
A shock wave occurs when a supersonic flow decelerates in response to a sharp
increase in pressure (supersonic compression) or when a supersonic flow encounters
a sudden, compressive change in direction (the presence of an obstacle).
For the flow conditions where the gas is a continuum, the shock wave is a narrow region
(on the order of several molecular mean free paths thick, ~ 6 x 10-6
cm) across which is
an almost instantaneous change in the values of the flow parameters.
Shock Wave Definition (from John J. Bertin/ Michael L. Smith,
“Aerodynamics for Engineers”, Prentice Hall, 1979, pp.254-255)
When the shock wave is normal to the streamlines it is called a Normal Shock Wave,
otherwise it is an Oblique Shock Wave.
The difference between a shock wave and a Mach wave is that:
- A Mach wave represents a surface across which some derivative of the flow variables
(such as the thermodynamic properties of the fluid and the flow velocity) may be
discontinuous while the variables themselves are continuous. For this reason we call
it a weak shock.
- A shock wave represents a surface across which the thermodynamic properties and the
flow velocity are essentially discontinuous. For this reason it is called a strong shock.
AERODYNAMICS
31
Movement of Shocks with Increasing Mach Number
<<<<<<< MMMMMMMM
SOLO AERODYNAMICS
Return to Table of Content
32
where
ρ0 = air density
U0 = true speed
l 0= characteristic length
μ0 = absolute (dynamic) viscosity
υ0 = kinematic viscosity
NumberReynolds:Re
0
00
0
000
0
0
0
υµ
ρ ρ
µ
υ
lUlU
=
==
Osborne Reynolds
(1842 –1912)
It was observed by Reynolds in 1884 that a Fluid Flow changes from Laminar to
Turbulent at approximately the same value of the dimensionless ratio (ρ V l/ μ) where l is
the Characteristic Length for the object in the Flow. This ratio is called the Reynolds
number, and is the governing parameter for Viscous Flow.
Reynolds Number and Boundary Layer
SOLO 1884AERODYNAMICS
33
Boundary Layer
SOLO
1904AERODYNAMICS
Ludwig Prandtl
(1875 – 1953)
In 1904 at the Third Mathematical Congress, held at
Heidelberg, Germany, Ludwig Prandtl (29 years old) introduced
the concept of Boundary Layer.
He theorized that the fluid friction was the cause of the fluid
adjacent to surface to stick to surface – no slip condition, zero
local velocity, at the surface – and the frictional effects were
experienced only in the boundary layer a thin region near the
surface. Outside the boundary layer the flow may be considered
as inviscid (frictionless) flow.
In the Boundary Layer on can calculate the
•Boundary Layer width
•Dynamic friction coefficient μ
•Friction Drag Coefficient CDf
34
The flow within the Boundary Layer can be of two types:
•The first one is Laminar Flow, consists of layers of flow sliding one over other in a
regular fashion without mixing.
•The second one is called Turbulent Flow and consists of particles of flow that
moves in a random and irregular fashion with no clear individual path, In
specifying the velocity profile within a Boundary Layer, one must look at the
mean velocity distribution measured over a long period of time.
There is usually a transition region between this two types of Boundary-Layer Flow
SOLO
AERODYNAMICS
35
Normalized Velocity profiles within a Boundary-Layer, comparison between
Laminar and Turbulent Flow.
SOLO
AERODYNAMICS
Boundary-Layer
36
Flow Characteristics around a Cylindrical Body
as a Function of Reynolds Number (Viscosity)
AERODYNAMICS
SOLO
Return to Table of Content
37
SOLO
Knudsen number (Kn) is a dimensionless number defined as the
ratio of the molecular mean free path length to a representative
physical length scale. This length scale could be, for example, the
radius of the body in a fluid. The number is named after Danish
physicist Martin Knudsen.
Knudsen
l
Kn
0
0
:
λ
= Martin Knudsen
(1871–1949).
For a Boltzmann gas, the mean free path may be readily calculated as:
• kB is the Boltzmann constant (1.3806504(24) × 10−23
J/K in SI units), [M1
L2
T−2
θ−1
]
p
TkB
20
2 σπ
λ =
• T is the thermodynamic temperature [θ1
]
λ0 = mean free path [L1
]
Knudsen Number
l0 = representative physical length scale [L1
].
• σ is the particle hard shell diameter, [L1
]
• p is the total pressure, [M1
L−1
T−2
].
See “Kinetic Theory of Gases” Presentation
For particle dynamics in the atmosphere and assuming standard atmosphere pressure i.e.
25 °C and 1 atm, we have λ0 ≈ 8x10-8
m.
AERODYNAMICS
38
SOLO
Martin Knudsen
(1871–1949).
Knudsen Number (continue – 1)
Relationship to Mach and Reynolds numbers
Dynamic viscosity,
Average molecule speed (from Maxwell–Boltzmann distribution),
thus the mean free path,
where
• kB is the Boltzmann constant (1.3806504(24) × 10−23
J/K in SI units), [M1
L2
T−2
θ−1
]
• T is the thermodynamic temperature [θ1
]
• ĉ is the average molecular speed from the Maxwell–Boltzmann distribution, [L1
T−1
]
• μ is the dynamic viscosity, [M1
L−1
T−1
]
• m is the molecular mass, [M1
]
• ρ is the density, [M1
L−3
].
0
2
1
λρµ c=
m
Tk
c B
π
8
=
Tk
m
B2
0
π
ρ
µ
λ =
AERODYNAMICS
39
SOLO
Martin Knudsen
(1871–1949).
Knudsen Number (continue – 2)
Relationship to Mach and Reynolds numbers (continue – 1)
The dimensionless Reynolds number can be written:
Dividing the Mach number by the Reynolds number,
and by multiplying by
yields the Knudsen number.
The Mach, Reynolds and Knudsen numbers are therefore related by:
Reynolds:Re
0
000
µ
ρ lU
=
Tk
m
lmTklallU
aUM
BB
γρ
µ
γρ
µ
ρ
µ
µρ 00
0
00
0
000
0
0000
00
//
/
Re
====
Kn
Tk
m
lTk
m
l BB
==
22 00
0
00
0 π
ρ
µπγ
γρ
µ
2Re
πγM
Kn =
AERODYNAMICS
40
SOLO
Knudsen Number (continue – 3)
Relationship to Mach and Reynolds numbers (continue –2)
According to the Knudsen Number the Gas Flow can be divided in three regions:
1.Free Molecular Flow (Kn >> 1): M/Re > 3
molecule-interface interaction negligible between incident and reflected particles
2.Transition (from molecular to continuum flow) regime: 3 > M/Re and
M/(Re)1/2
> 0.01 (Re >> 1). Both intermolecular and molecule-surface collision are
important.
3.Continuum Flow (Kn << 1): 0.01 > M/(Re)1/2
. Dominated by intermolecular
collisions.
2Re
πγM
Kn =
AERODYNAMICS
SOLO
Knudsen Number (continue – 4)
Inviscid
Limit Free
Molecular
LimitKnudsen Number
Boltzman Equation
Collisionless
Boltzman
Equation
Discrete
Particle
model
Euler
Equation
Navier-Stokes
Equation
Continuum
model
Conservation Equation
do not form a closed set
Validity of conventional mathematical models as a function of local
Knudsen Number
A higher Knudsen Number indicates larger mean free path λ, or the particular nature
of the Fluid, meaning that Boltzmann Equations must be employed.
Lower Knudsen Number means small free path, i.e. the flow acts as a continuum,
and Navier-Stokes Equations must be used.
Knudsen
l
Kn
0
0
:
λ
=
AERODYNAMICS
Return to Table of Content
42
The true airspeed (TAS; also KTAS, for knots true airspeed) of an aircraft is
the speed of the aircraft relative to the air mass in which it is flying.
True Airspeed
TAS can be calculated as a function of Mach number and static air temperature:
where
a0 is the speed of sound at standard sea level (661.47 knots)
M is Mach number,
T is static air temperature in kelvin,
T0 is the temperature at standard sea level (288.15ºK)
0
0
T
T
MaTAS =
qc is impact pressure
P is static pressure








−





+= 11
5 7
2
0
0
P
q
T
T
aTAS c
Flight Instruments
SOLO
Flight Instruments
SOLO
44
Flight Instruments
Airspeed Indicators
2
2
1
vpp StatTotal ⋅+= ρ
The airspeed directly given by the differential pressure is called
Indicated Airspeed (IAS). This indication is subject to positioning errors of the pitot
and static probes, airplane altitude and instrument systematic defects.
The airspeed corrected for those errors is called Calibrated Airspeed (CAS).
Depending on altitude, the critic airspeeds for maneuver, flap operation etc. change
because the aerodynamic forces are function of air density. An equivalent airspeed
VE (EAS) is defined as follows:
0ρ
ρ
VVE =
V – True Airspeed
ρ – Air Density
ρ0 – Air Density at Sea Level
45
http://jim-quinn8.blogspot.co.il/2012_03_01_archive.html
Flight Instruments
46http://flysafe.raa.asn.au/groundschool/CAS_EAS.html
Calibrated Airspeed (CAS)
Flight Instruments
47
True Airspeed (TAS) and Calibrated Airspeed (CAS) Relationship
with Varying Altitude and Temperature
Flight Instruments
48
TAS and CAS Relationship with Varying Altitude and Temperature (continue)
Flight Instruments
49
Mach Number vs TAS Variation with Altitude
Flight Instruments
50
Density Altitude Chart
Flight Instruments
51
http://digital.library.unt.edu/ark:/67531/metadc62400/m1/9/
Flight Instruments
Return to Table of Content
52
SOLO
Aerodynamic Forces
( )[ ]∫∫ +−= ∞
WS
A dstfnppF

11
ntonormalplanonVofprojectiont
dstonormaln
ˆˆ
ˆ

−
−
( )
airflowingthebyweatedsurfaceVehicleS
SsurfacetheonmNstressforcefrictionf
Ssurfacetheondifferencepressurepp
W
W
W
−
−
−−∞
)/( 2
Aerodynamic Forces acting on a
Vehicle Surface SW.
AERODYNAMICS
53
SOLO
( )






−
−
=
L
D
F
W
A

VelocitytoNormalForceLiftL
VelocitytooppositeForceDragD
−
−
L
D
CSVL
CSVD
2
2
2
1
2
1
ρ
ρ
=
= ( )
( ) tCoefficienLiftRMC
tCoefficienDragRMC
eL
eD
−
−
βα
βα
,,,
,,,
anglesideslipandattackofangle
viscositydynamic
lengthsticcharacteril
soundofspeedHa
numberReynoldslVR
BodytoRelativeVelocityFlowV
numberMachaVM
e
−
−
−
−
−=
−
−=
βα
µ
µρ
,
)(
/
/
AERODYNAMICS
( )
V
W
A nLVDF 11 −−=

Aerodynamic Forces
Lift and Drag Forces
54
SOLO
( )
( )∫∫
∫∫
⋅+⋅−=
⋅+⋅−=
W
W
S
VfVpL
S
fpD
dsntCnnC
S
C
dsVtCVnC
S
C
1ˆ1ˆ
1
1ˆ1ˆ
1
Wf
Wp
Ssurfacetheontcoefficienfriction
V
f
C
Ssurfacetheontcoefficienpressure
V
pp
C
−=
−
−
= ∞
2/
2/
2
2
ρ
ρ
ntonormalplanonVofprojectiont
dstonormaln
ˆˆ
ˆ

−
−
Aerodynamic Forces
CD – Drag Coefficient
CL – Lift Coefficient
AERODYNAMICS
( )
[ ] [ ]( )∫
∫
∞∞
=
−−−=
−=′
Edge
Trailing
Edge
Leading
sideuppersidelower
cos
Edge
Trailing
Edge
Leading
sideuppersidelower
pp
cospcosp
dxpp
dsL
sdxd
USLS
θ
θθ
Divide left and right sides of the first equation by cV 2
2
1
∞ρ
∫












−
−
−
=
′
∞
∞
∞
∞
∞
Edge
Trailing
Edge
Leading
upperlower
c
x
d
V
pp
V
pp
cV
L
222
2
1
2
1
2
1
ρρρ
We get:
Relationship between Lift and Pressure on Airfoil
Lower
Surface
Upper
Surface
( )∫ −=−
Edge
Trailing
Edge
Leading
sideuppersidelower sinpsinp dsD USLS θθ
Lift – Aerodynamic component normal to V
Drag – Aerodynamic component opposite to V
SOLO AERODYNAMICS
Aerodynamic Forces
From the previous slide,
∫












−
−
−
=
′
∞
∞
∞
∞
∞
Edge
Trailing
Edge
Leading
upperlower
c
x
d
V
pp
V
pp
cV
L
222
2
1
2
1
2
1
ρρρ
The left side was previously defined as the sectional lift coefficient Cl.
The pressure coefficient is defined as:
2
2
1
∞
∞−
=
V
pp
Cp
ρ
Thus,
( )∫ −=
edge
Trailing
edge
Leading
upperplowerpl
c
x
dCCC ,,
Lower
Surface
Upper
Surface
Relationship between Lift and Pressure on Airfoil (continue – 1)
SOLO AERODYNAMICS
Aerodynamic Forces
57
SOLO
Velocity Field
Sum of the elementary Forces on the Body
Lift as the Sum of the elementary Forces on the Body
AERODYNAMICS
Aerodynamic Forces
58
SOLO
Lift and Drag Coefficients
AERODYNAMICS
Subsonic Speeds
np
α−
Upper
xd
yd
∞U
Upper
xd
yd
∞p∞p α
  0,,
2
0 2
0
D
TurbulentforMore
LaminarforLess
dragFriction
fD
TurbulentforLess
LaminarforMore
dragPressure
pDD
stall
a
L
CCCC
aC
=+=
<==
=
αααπα
π
Subsonic Incompressible Flow (ρ∞ = const.) about Wings of Finite Span (AR < ∞)
Subsonic Incompressible Flow (ρ∞ = const.) about Wings of Infinite Span (AR → ∞)
 ( ) 





−=−=
ARe
C
C L
i
a
L
π
απααπ 22
0
ARe
C
be
SC
V
w L
SbAR
Li
i
ππ
α
/
2
2
=
===
α
π
α
π
ARe
a
a
ARe
CL
0
0
1
2
1
2
+
=
+
=
ARe
C
C L
Di
π
2
=
   AR
C
CCCCC L
D
drag
induced
D
drag
friction
fD
drag
pressure
pDD i
π
2
0,, +=++=
e – span efficiency factor
Aerodynamic Forces
Return to Table of Content
59
SOLO
http://www.dept.aoe.vt.edu/~mason/Mason_f/CAtxtChap5.pdf
Drag Breakdown Possibilities (internal flow neglected)
AERODYNAMICS
Aerodynamic Drag
60
AERODYNAMICS
Drag Variation with Mach Number
SOLO
Aerodynamic Drag
61
Stengel, Aircraft Flight Dynamics, Princeton, MAE 331, Lecture 2
SOLO AERODYNAMICS
Aerodynamic Drag
62N.X. Vinh, “Flight Mechanics of High-Performance Aircraft”, Cambridge University
Press, 1993
α =0 – corresponds to CL=0.
α0 – minimize CD.
α1 – minimize the ratio CD/CL
1/2
.
α2 – minimize the ratio CD/CL
2/3
.
α*
– minimize the ratio CD/CL.
α3 – minimize the ratio CD/CL
3/2
.
αmax – maximum CL.
A Realistic Drag Polar
SOLO AERODYNAMICS
Aerodynamic Drag
63N.X. Vinh, “Flight Mechanics of High-Performance Aircraft”, Cambridge University
Press, 1993
Parabolic Drag Polar of a typical High Subsonic Aircraft
at different Mach Numbers
SOLO AERODYNAMICS
Aerodynamic Drag
64N.X. Vinh, “Flight Mechanics of High-Performance Aircraft”, Cambridge University
Press, 1993
Variation of CD0 (M) for a supersonic
aircraft
Variation of aerodynamic characteristic
for a typical subsonic transport aircraft
Variation of aerodynamic characteristic
for a typical supersonic fighter aircraft
SOLO AERODYNAMICS
Aerodynamic Drag
65
Movement of Shocks with Increasing Mach Number
The Mach Number at witch M=1 appears
on the Airfoil Upper Surface is called the
Critical Mach Number for this Airfoil.
The Critical Mach Number can be
calculated as follows. Assuming an
isentropic flow through the flow-field we
have
( )1/
2
2
2
1
1
2
1
1
−
∞
∞












−
+
−
+
=
γγ
γ
γ
A
A
M
M
p
p
p∞, M∞ - Pressure and Mach Number upstream the Airfoil
pA, MA- Pressure and Mach Number at a point A on the Airfoil
Critical Mach Number
The Pressure Coefficient Cp is computed using
( )












−












−
+
−
+
=





−=
−
∞
∞∞∞
1
2
1
1
2
1
1
2
1
2
1/
2
2
γγ
γ
γ
γγ
A
A
pA
M
M
Mp
p
M
C
Definition of Critical Mach
Number.
Point A is the location of
minimum pressure on the
top surface of the Airfoil.
SOLO AERODYNAMICS
66
Movement of Shocks with Increasing Mach Number
Critical Mach Number
This relation gives a unique relation between the upstream values of p∞, M∞ and the
respective values pA, MA at a point A on the Airfoil.
Assume that point A is the point of minimum pressure, therefore maximum velocity,
on the Airfoil and that this maximum velocity corresponds to MA = 1. Then by
definition M∞ = Mcr .
( )












−












−
+
−
+
=





−=
−
∞
∞∞∞
1
2
1
1
2
1
1
2
1
2
1/
2
2
γγ
γ
γ
γγ
A
A
pA
M
M
Mp
p
M
C
( )












−












−
+
−
+
=
−
1
2
1
1
2
1
1
2
1/
2
γγ
γ
γ
γ
cr
cr
p
M
M
C cr
2
0
1 ∞−
=
M
C
C
p
p
( )












−












−
+
−
+
=
−
1
2
1
1
2
1
1
2
1/
2
γγ
γ
γ
γ
cr
cr
p
M
M
C cr
2
0
1 ∞−
=
M
C
C
p
p
To find the Mcr we need on other equation describing
Cp at subsonic speeds. We can use the
Prandtl-Glauert Correction
or the Karman-Tsien Rule or
Laiton’s Rule
SOLO AERODYNAMICS
67
Movement of Shocks with Increasing Mach Number
Critical Mach Number
AirfoilThickAirfoilMediumAirfoilThin
AirfoilThickAirfoilMediumAirfoilThin
crcrcr
ppp
MMM
CCC
>>
<< 000
The point of minimum pressure, therefore maximum velocity, does not correspond
to the point of maximum thickness of the Airfoil. This is because the point of
minimum pressure is defined by the specific shape of the Airfoil and not by a local
property.
The Critical Mach Number is a function of
the thickness of the Airfoil.
For the thin Airfoil the Cp0 is smaller in
magnitude and because the disturbance in the
Flow is smaller. Because of this the Critical
Mach Number of the thin Airfoil is greater
SOLO AERODYNAMICS
68
Movement of Shocks with Increasing Mach Number
Drag Divergence Mach Number
The Drag at small Mach number, due to
Profile Drag with Induced Drag =0 (αi = 0)
is constant (points a, b, and c) until
M∞ = Mcr (point c). As the velocity
increase above Mcr (point d), a finite
region of supersonic flow (Weak Shock
boundary)appears on the Airfoil.
The Mach Number in this bubble of
supersonic flow is slightly above Mach 1,
typically 1.02 to 1.05. If M∞ increases more,
We encounter a point, e, at which is a sudden increase in Drag. The Value of M∞ at
which the sudden increase in Drag starts is defined as the Drag-divergence Mach
Number, Mdrag-divergence < 1. At this point Shock Waves appear on the Airfoil. The
Shock Waves are dissipative phenomena extracting energy (Drag) from the kinetic
energy of the Airfoil. In addition the sharp increase of the pressure across the
Shock Wave create a strong adverse pressure gradient, causing the Flow to
separate
From the Airfoil Surface creating Drag increase. Beyond the Drag-divergence
Mach Number, the Drag Coefficient becomes very large, increasing by a factor of
10 or more. As M∞ approaches unity (point f) the Flow on both the top and the
SOLO AERODYNAMICS
69
Summary of Airfoil Drag
The Drag of an Airfoil can be described as the sum of three contributions:
iwpf DDDDD +++=
where
D – Total Drag of the Airfoil
Df – Skin Friction Drag
Dp – Pressure Drag due to Flow Separation
Dw – Wave Drag (present only at Transonic and Supersonic Speeds; zero for
Subsonic Speeds below the Drag-divergence Mach Number)
Di – Induced Drag
In terms of the Drag Coefficients, we can write:
iDwDpDfDD CCCCC ,,,, +++=
The Sum:
pDfD CC ,, + Profile Drag Coefficient
SOLO AERODYNAMICS
Aerodynamic Drag
70
SOLO
http://www.dept.aoe.vt.edu/~mason/Mason_f/CAtxtChap5.pdf
Categorization of Drag
AERODYNAMICS
Aerodynamic Drag
71
Relative Drag Force as a Function of Reynolds Number (Viscosity)
AERODYNAMICS
Drag CD0 due to
Flow Separation
SOLO
Aerodynamic Drag
72
Relative Drag Force as a Function of Reynolds Number (Viscosity)
AERODYNAMICS
Drag due to Viscosity:
1.Skin Friction
2.Flow Separation
(Drop in pressure
behind body)
∫∫
∫∫








⋅+⋅
−
−=








⋅+⋅−=
∧∧
∞
∧∧
W
W
S
S
fpD
ds
w
t
V
f
w
n
V
pp
S
ds
w
tC
w
nC
S
C
xx
xx
11
11
ˆ
2/
ˆ
2/
1
ˆˆ
1
22
ρρ
SOLO
Aerodynamic Drag
73
Effect of Mach Number on the Drag Coefficient for a given Angle of Attack (AOA)
and on the Lift Coefficient
AERODYNAMICS
Summary of Mach Effect on Drag and Lift
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74
Wing Parameters
Airfoil: The cross-sectional shape obtained by the
intersection of the wing with the perpendicular plane
1. Wing Area, S, is the plan surface of the wing.
2. Wing Span, b, is measured tip to tip.
3. Wing average chord, c, is the geometric average. The product of the span and
the average chord is the wing area (b x c = S).
4. Aspect Ratio, AR, is defined as:
( )∫−
=
2/
2/
b
b
dyycS
( )
b
S
dyyc
b
c
b
b
== ∫−
2/
2/
1
S
b
AR
2
=
AERODYNAMICSSOLO
75
Wing Parameters (Continue)
5. The root chord, , is the chord at the wing centerline, and the tip chord,
is the chord at the tip.
6. Taper ratio,
7. Sweep Angle,
is the angle between the line of 25 percent chord and the perpendicular
to root chord.
8. Mean aerodynamic chord,
rc
Λ
r
t
c
c
=λ
tc
λ
( )[ ]∫−
=
2/
2/
21~
b
b
dyyc
S
c
c~
AERODYNAMICSSOLO
76
Wing Parameters (Continue)
AERODYNAMICS
Illustration of Wing Geometry
Planform, xy plane
Dihedral (V form),
yz plane
Profile, twist
xz plane
Geometric Designation of Wings
of various planform
Swept-back
Wing
Delta
Wing
Elliptic
Wing
SOLO
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77
Wing Design Parameters
•Planform
- Aspect Ratio
- Sweep
- Taper
- Shape at Tip
- Shape at Root
•Chord Section
- Airfoils
- Twist
•Movable Surfaces
- Leading and Trailing-Edge Devices
- Ailerons
- Spoilers
•Interfaces
- Fuselage
- Powerplants
- Dihedral Angle
AERODYNAMICSSOLO
Return to Table of Content
SOLO
78
Aircraft Flight Control
Specific Stabilizer/Tail Configurations
Tailplane
Fuselage mounted Cruciform T-tail Flying tailplane
The tailplane comprises the tail-mounted fixed horizontal stabilizer and movable elevator.
Besides its planform, it is characterized by:
• Number of tail planes - from 0 (tailless or canard) to 3 (Roe triplane)
• Location of tailplane - mounted high, mid or low on the fuselage, fin or tail
booms.
• Fixed stabilizer and movable elevator surfaces, or a single combined stabilator or
(all) flying tail.[1]
(General Dynamics F-111)
Some locations have been given special names:
• Cruciform: mid-mounted on the fin (Hawker Sea Hawk, Sud Aviation Caravelle)
• T-tail: high-mounted on the fin (Gloster Javelin, Boeing 727)
Sud Aviation Caravelle
Gloster Javelin
SOLO
79
Aircraft Flight Control
Specific Stabilizer/Tail Configurations
Tailplane
Some locations have been given special names:
• V-tail: (sometimes called a Butterfly tail)
• Twin tail: specific type of vertical stabilizer arrangement found on the empennage of
some aircraft.
• Twin-boom tail: has two longitudinal booms fixed to the main wing on either side of
the center line.
The V-tail of a Belgian Air
Force Fouga Magister
de Havilland Vampire
T11, Twin-Boom Tail
A twin-tailed B-25 Mitchell
Return to Table of Content
80
SOLO Aircraft Propulsion Systems
Classification of Engine Concepts , mostly used in Aviation
81
Run This
http://lyle.smu.edu/propulsion/Pages/propeller.htm
In small aircraft, the propeller is normally powered by a
piston engine as shown above. In larger vessels like
nuclear submarines, the propeller may be powered by a
nuclear power plant. The basic operation of a propeller
propulsion system is described in the interactive animation
below. Use the arrows to step through descriptions of the
different components.
SOLO Propeller Propulsion
82
SOLO
The Rotating Parts of Jet Engine
Compressor
Shaft
Turbojet animation
Turbine
Air Breathing Jet Engines
Run This
83
http://lyle.smu.edu/propulsion/Pages/variations.htm
Run This
A turbofan still has all the main components of a turbojet, but a fan and surrounding duct are added to the
front as shown in the animation below. A fan is basically a propeller with a lot of blades specially designed
to spin very quickly. Its function is essentially identical to a propeller, namely, the blades accelerate the
oncoming air flow to create thrust. In a turbofan, however, the fan is driven by turbines in the attached
turbojet engine, rather than by an internal combustion engine. Use the arrows in the interactive animation
below to step through descriptions of the different components and obtain more detailed information about
their operation.
Turbofan
84
SOLO
Animation of a 2-spool, high-bypass turbofan.
A. Low pressure spool
B. High pressure spool
C. Stationary components
1. Nacelle
2. Fan
3. Low pressure compressor
4. High pressure compressor
5. Combustion chamber
6. High pressure turbine
7. Low pressure turbine
8. Core nozzle
9. Fan nozzle
Turbofan
Air Breathing Jet Engines
Run This
85
SOLO
Turboprop
A turboprop engine is a type of turbine engine which
drives an aircraft propeller using a reduction gear.
The gas turbine is designed specifically for this
application, with almost all of its output being used to
drive the propeller. The engine's exhaust gases contain
little energy compared to a jet engine and play only a
minor role in the propulsion of the aircraft.
The propeller is coupled to the turbine through a
reduction gear that converts the high RPM, low torque
output to low RPM, high torque. The propeller itself is
normally a constant speed (variable pitch) type similar to
that used with larger reciprocating aircraft engines.
Turboprop engines are generally used on small subsonic
aircraft, but some aircraft outfitted with turboprops have
cruising speeds in excess of 500 kt (926 km/h, 575 mph).
Large military and civil aircraft, such as the Lockheed L-
188 Electra and the Tupolev Tu-95, have also used
turboprop power. The Airbus A400M is powered by four
Europrop TP400 engines, which are the third most
powerful turboprop engines ever produced, after the
Kuznetsov NK-12 and Progress D-27.
Air Breathing Jet Engines
Run This
86http://lyle.smu.edu/propulsion/Pages/variations.htm
Turboprop Engines: A turboprop engine is basically a propeller driven by a turbojet.
Alternatively, it can be viewed as a very large bypass ratio turbofan. It is not exactly a
turbofan because there is no shroud or "duct" surrounding the propeller and the propeller
does not spin as fast as a fan. The basic components of a turboprop are illustrated in the
interactive animation below. Use the arrows to step through descriptions of the different
components.
A turboprop engine enjoys the high efficiency of a propeller, owing to the large bypass ratio it
provides. In fact, nearly all of the thrust generated by a turboprop is from the propeller. A
turboprop also enjoys the high power-to-weight ratio of turbojet engines, resulting in a
powerful compact propulsion system.
Run This
Return to Table of Content
SOLO Air Breathing Jet Engines
87
SOLO Aircraft Propulsion System
Aircraft propellers or airscrews[1]
convert rotary motion from
piston engines, turboprops or electric motors to provide
propulsive force. They may be fixed or variable pitch.
Aircraft Propellers
Diesel Engine
developed in the GAP
program. Credit:
NASA
The simplest theory describing the operation of the propeller,
assumes that the rotating propeller can be approximated by a
thin Actuator Disk producing a uniform change in the velocity
of the air stream passing across it.
Actuator Disk (One-Dimensional Momentum) Theory
88
SOLO Propeller Aerodynamics
Actuator Disk
2
11
2
22
2
1
2
1
VpVp ρρ +=+
2
44
2
33
2
1
2
1
VpVp ρρ +=+
Bernoulli’s equations on each side of the Disk:
Far from the Disk we have the same ambient
pressure, hence: 41 pp =
Therefore ( )2
1
2
423
2
1
VVpp −=− ρ
Conservation of Mass through the Propeller Disk
pp AVAVm 320 ρρ == 32 VV =
Conservation of Energy on both sides of the
Propeller Disk
Actuator Disk (One-Dimensional Momentum) Theory
89
SOLO Propeller Aerodynamics
Actuator Disk
( )2
1
2
423
2
1
VVpp −=− ρ
The Thrust provided by the Propeller Disk is
given by:
( ) ( )143140 VVAVVVmT p −=−= ρ
where
- Fluid mass flow [kg/sec] through DiskpAVm 30 ρ=
ρ – Flow density [kg/m3
]
Ap – Disk area [m2
]
The Thrust also equals the Force on the Disk Surface due to Pressure jump:
( ) ( ) pp AVVAppT 2
1
2
423
2
1
−=−= ρ
From the two expressions of Thrust we obtain
( ) ( )2
1
2
4143
2
1
VVVVV −=− ( )413
2
1
VVV +=
Conservation of Momentum
Actuator Disk (One-Dimensional Momentum) Theory
SOLO Propeller Aerodynamics
Model of the Flow through Propeller
according to the Actuator Disk Concept
( )
( ) ppp
pp
VA
mVVVAT
v2v
v20143
⋅+=
=−=
∞ρ
ρ 
We found
Let compute vs as function of other parameters
0
2
vv
2
=−+ ∞
p
pp
A
T
V
ρ
0
222
v
2
>+





+−= ∞∞
p
p
A
TVV
ρ
This solution corresponds to a
Propeller, where Energy is added
to the Flow.
Actuator Disk (One-Dimensional Momentum) Theory
Ideal Power Consumed by the Rotor
( )
( )
( )








+





+=
⋅=+=
+=
−+=
−=
∞∞
∞
∞
∞∞
p
p
pp
p
A
TVV
T
DiskatVelocityFlowThrustVT
Vm
VmVm
InFlowEnergyOutFlowEnergyP
ρ222
___v
vv2
2
1
v2
2
1
2
0
2
0
2
0


SOLO Propeller Aerodynamics
The Efficiency of an Ideal Propeller
This is called the idea1 efficiency of a propeller, which represents the upper limit
of the efficiency that cannot be exceeded whatever the shape of the propeller.
( ) ( )aaVDVAT
Va
ppp
p
+=⋅+= ∞
=
∞
∞
1
2
vv2 22
/v:
ρ
π
ρ
( ) aVV
V
VT
VT
PowerOutput
PowerInput Va
ppp
P
p
+
=
+
=
+
=
+⋅
⋅
==
∞=
∞∞
∞
∞
∞
1
1
/v1
1
vv
/v:
η
( ) p
P
P
C
JDV
P
aa 323
2
3
122
1
1
πρπη
η
==+=
−
∞
( ) ( ) aaVDVTP p
232
1
2
v +=+= ∞∞ ρ
π
( ) T
P
P
C
JDV
T
aa 2222
122
1
1
πρπη
η
==+=
−
∞
where
Actuator Disk (One-Dimensional Momentum) Theory
( )
.:
.:
:
42
53
2/
2
CoeffThrust
Dn
T
C
CoeffPower
Dn
P
C
RatioAdvance
R
V
Dn
V
J
T
p
n
RD
ρ
ρ
ππ
=
=
Ω
== ∞
Ω=
=
∞
SOLO Propeller Aerodynamics
The Efficiency of an Ideal Propeller ( )
.:
.:
:
42
53
2/
2
CoeffThrust
Dn
T
C
CoeffPower
Dn
P
C
RatioAdvance
R
V
Dn
V
J
T
p
n
RD
ρ
ρ
ππ
=
=
Ω
== ∞
Ω=
=
∞
E.Torenbeek, H.Wittenberg, “Flight Physics – Essentials of Aeronauical Disciplines and Technology, with
Historical Notes”, Springer, 2009
Typical Propeller Diagram
Actuator Disk (One-Dimensional Momentum) Theory
T
P
P
C
J 22
121
πη
η
=
−
p
P
P
C
J 33
121
πη
η
=
−
JV
Dn
P
VT
C
C P
p
T η
==
∞
∞
SOLO Propeller Aerodynamics
The Efficiency of an Ideal Propeller
E.Torenbeek, H.Wittenberg, “Flight Physics – Essentials of Aeronauical Disciplines and Technology, with
Historical Notes”, Springer, 2009
Propeller Efficiency and Advance Ratio for various flight speeds.
The Blade Pitch β is given. The change in Efficiency is due to the
change in Angle-of-Attack (due to change in Velocity V∞ or Ω),
Actuator Disk (Momentum) Theory
J
C
C
p
T
P =η
( )
.:
.:
:
42
53
2/
2
CoeffThrust
Dn
T
C
CoeffPower
Dn
P
C
RatioAdvance
R
V
Dn
V
J
T
p
n
RD
ρ
ρ
ππ
=
=
Ω
== ∞
Ω=
=
∞
94
AERODYNAMICS
Asselin, M., “Introduction to Aircraft Performance”, AIAA Education Series, 1997
Actuator Disk (Momentum) Theory
SOLO
( )
RatioAdvance
R
V
Dn
V
J
n
RD Ω
== ∞
Ω=
=
∞ ππ2/
2
:
We can see that by varying
the Propeller Pitch β we
can operate at maximum
efficiency ηmax.
95
SOLO Propeller Aerodynamics
E. Torenbeek, H. Wittenberg, “Flight Physics, Essentials of Aeronautical Disciplines and
Technology, with Historical Notes”, Springer, 2009, § 5.9, “Propeller Performance”, pg. 236
Propeller Blade Geometry
Variation of Angles and Velocities along a Propeller Blade
Propeller Blade have a variation of
•Twist β
•Chord c
•Thickness t
r
V
Ω
=φtan
From the Propeller Blade Geometry
– advance angleϕ [rad]
V – air velocity [m/sec], normal to rotation plane
V = V∞ + v
Ω – rotation rate [rad/sec]
r – rotation radii [m] of blade section element
φβα −=
α – angle of attack [rad] of the section element (between section chord and resultant velocity)
β – angle [rad] between section chord and rotation plane
Blade Element Theory.
96
SOLO Propeller Aerodynamics
( ) ( )2222
v++Ω=+= ∞VrUUV pTres
Given a Propeller Blade Element at a distance r from
the Hub, the Resultant Velocity is given by
We have
( ) ( ) ( )
( ) ( ) ( )αραρ
αραρ
DDres
LLres
CcrVCcVDd
CcrVCcVLd
22222
22222
2
1
2
1
2
1
2
1
Ω+==
Ω+==
∞
∞
Section Lift, normal to Vres
Section Drag, opposite to Vres
Simplified view of the forces on a Propeller
Blade Element
c – chord of Propeller Blade Element
CL – Lift Coefficient of Propeller Blade Element
CD – Drag Coefficient of Propeller Blade Element
The resultant forces Normal (d T) and in the Disk Plane (d Fx) are











 −
=





Dd
Ld
Fd
Td
x φφ
φφ
cossin
sincos
Blade Element Theory.
The Aerodynamic Moment and Power of the Propeller Blade Element are
QdFdrFdUPd
FdrQd
xxT
x
Ω=⋅Ω==
⋅=
97
SOLO Propeller Aerodynamics
The net force acting on the blades are the summation
of the forces acting upon the individual elements.
We must multiply by the number of blades B of the
Rotor.
We have
Blade Element Theory.
( ) ( ) ( ) ( ) ( )( )
( ) ( ) ( ) ( ) ( )( )
( ) ( ) ( ) ( ) ( )( )∫∫
∫∫
∫∫
=
=
∞
=
=
=
=
∞
=
=
=
=
∞
=
=
+Ω+Ω=⋅Ω=
+Ω+=⋅=
−Ω+==
Rr
r
DL
Rr
r
x
Rr
r
DL
Rr
r
x
Rr
r
DL
Rr
r
rdrCrCrrVBcFdrBP
rdrCrCrrVBcFdrBQ
rdrCrCrVBcTdBT
0
222
0
0
222
0
0
222
0
cossin
2
1
cossin
2
1
sincos
2
1
φαφαρ
φαφαρ
φαφαρ
( )
r
V
r
Ω
+
= ∞ v
tanφ ( ) ( ) ( )rrr φβα −=
The Thrust, Aerodynamic Moment and Power of the Propeller (B blades) are
The β (r) must be twisted to have the function α (r) optimal at each section r for given V∞
and Ω. If V∞ changes by rotating the Propeller around it’s axis (Pitch) we change β (r) to
optimize again α (r).
98
SOLO Propeller Aerodynamics
Blade Element Theory.
42
22
242
53
32
253
2
2
4
:
4
:
:
D
T
Dn
T
C
R
P
Dn
P
C
RatioAdvance
R
V
Dn
V
J
n
RD
T
n
RD
p
n
RD
Ω
==
Ω
==
Ω
==
Ω
=
=
Ω
=
=
∞
Ω
=
=
∞
ρ
π
ρ
ρ
π
ρ
π
π
π
π

( ) ( ) ( ) ( )( )∫
=
=
∞






−





+
Ω
=
Ω
=
Rr
r
DLT
R
r
drCrC
R
r
R
V
R
cB
R
T
C
0
2
2
2
22
22
42
2
sincos
84
φαφαπ
π
π
π
ρ
π
σ

( ) ( ) ( ) ( )( )∫
=
=
∞






+





+
Ω
=
Ω
=
Rr
r
DLP
R
r
drCrC
R
r
R
rV
R
Bc
R
P
C
0
2
2
2
2
22
53
3
cossin
84
φαφαππ
π
π
π
ρ
π
σ
We have
or
Let use the definitions:
( )
Solidity
R
cB
R
RcB
DiskSurface
ElementsBladeSurface
==
==
π
π
σ 2
:
( ) ( ) ( ) ( ) ( )( )∫
=
=
=
−+=
1
0
222
/
sincos
8
x
x
DL
Rrx
T xdxCxCxJC φαφαπσ
π
Thrust Coefficient
( ) ( ) ( ) ( ) ( )( )∫
=
=
=
++=
1
0
222
/
cossin
8
x
x
DL
Rrx
P xdxCxCxxJC φαφαππσ
π Power Coefficient
99
SOLO Propeller Aerodynamics
Blade Element Theory.
42
22
242
53
32
253
2
2
4
:
4
:
:
D
T
Dn
T
C
R
P
Dn
P
C
RatioAdvance
R
V
Dn
V
J
n
RD
T
n
RD
p
n
RD
Ω
==
Ω
==
Ω
==
Ω
=
=
Ω
=
=
∞
Ω
=
=
∞
ρ
π
ρ
ρ
π
ρ
π
π
π
π
Characteristic Curves of a Propeller
Propeller Efficiency.
J
C
C
Dn
V
C
C
CDn
VCDn
P
VT
P
T
P
T
P
T
==== ∞∞∞
53
42
ρ
ρ
η
100
SOLO Propeller Aerodynamics
Fuel Consumption
For
VTPP ppA ⋅⋅=⋅= ηηThe Available Power is
ηp – propulsive efficiency
For a given throttle setting, a regular piston engine,
that aspire atmospheric air, produces power that is
almost constant with velocity but decreases as the
altitude increases (air density decreases).
VTP ⋅=
Propeller Propulsion
The fuel mass flow is proportional to engine power P
pApp PcPcWf η/==−= 
cp – power specific fuel consumption
VPT /=
The engine power is



=





=
restratosphe
etropospher
x
P
P
x
1
75.0
00 ρ
ρ
101
H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35
Asselin, M., “Introduction to Aircraft
Aerodynamics”, AIAA Education Series, 1997
Return to Table of Content
102
Most jet engines are Turbofans and some are
Turbojets which use gas turbines to give high pressure
ratios and are able to get high efficiency, but a few use
simple ram effect or pulse combustion to give
compression.
Most commercial aircraft possess turbofans, these
have an enlarged air compressor which permit them to
generate most of their thrust from air which bypasses
the combustion chamber.
AIR BREATHING JET ENGINESSOLO
Operation of Aircraft Turbojet EngineAircraft Turbo Engines
The turboprop engine : Turboprop engine derives its
propulsion by the conversion of the majority of gas
stream energy into mechanical power to drive the
compressor , accessories , and the propeller load. The
shaft on which the turbine is mounted drives the
propeller through the propeller reduction gear system .
Approximately 90% of thrust comes from propeller and
about only 10% comes from exhaust gas.
The turbofan engine : Turbofan engine has a duct
enclosed fan mounted at the front of the engine and driven
either mechanically at the same speed as the compressor ,
or by an independent turbine located to the rear of the
compressor drive turbine . The fan air can exit separately
from the primary engine air , or it can be ducted back to
mix with the primary's air at the rear . Approximately more
than 75% of thrust comes from fan and less than 25%
comes from exhaust gas.
103
Propulsion Force = Thrust
SOLO
The net Thrust ( T ) of a Turbojet is given by
where:
ṁ air  = the mass rate of air flow through the engine
ṁ fuel  = the mass rate of fuel flow entering the engine
Ue = the velocity of the jet (the exhaust plume)
U0 = the velocity of the air intake = the true airspeed of the aircraft
(ṁ air  + ṁ fuel  )Ue = the nozzle gross thrust (FG)
ṁ air  U0 = the ram drag of the intake air
Aircraft Propulsion System
( )[ ] ( ) airfueleeeair mmfAppUUfmTHRUST  /:1 00 =−+−+==T
Jet Engines Thrust Force
Introduction to Air Breathing Jet Engines
00 ,Up
0A
eA
ee Up ,
104
Turbojet
SOLO
Thrust Computation for Air Breathing Engines
( ) ( )
    
  
DRAGFRICTION
A
WA
DRAGPRESURE
A
WA
THRUST
eeeeex
WW
AdAdppAppAUAUF ∫∫∫∫ −−−−+−= θτθρρ cossin000
2
00
2
00000 & mAUmmAU feee
 =+= ρρUsing C.M.
( ) ( ) 00000
2
00
2
UmUmmAppAUAUTHRUST efeeeee
 −+=−+−= ρρ
or
we obtain
( )[ ] ( ) 0000 /:1 mmfAppUUfmTHRUST feee
 =−+−+==T
and ( )
    
DRAGFRICTION
A
WA
DRAGPRESURE
A
WA
WW
AdAdppDRAGD ∫∫∫∫ +−== θτθ cossin0
00 ,Up
0A
eA
ee Up ,
Air Breathing Jet Engines
Pressure force
Friction force
Wetted Surface
Aerodynamic Forces on Wetted Surfaces
105
Turbojet
SOLO
Thrust Computation for Air Breathing Engines (continue – 1)
since
and
00 ,Up
0A
eA
ee Up ,
( ) 0
00000
00
00
/:111 mmf
A
A
p
p
U
U
f
Ap
Um
Ap
f
eee


=





−+





−+=
T
2
0
2
0
00
002
0
0
2
00
0
2
00
00
2
000
00
00
MM
TR
TR
M
p
a
p
U
Ap
UA
Ap
Um
γ
ρ
γρρρρ
=====

( ) 0
000
2
0
00
/:111 mmf
A
A
p
p
U
U
fM
Ap
f
eee
=





−+





−+= γ
T
000
2
00
0
00
000000 MApaM
TR
Ap
aUAam γρ ===
( ) 0
0000
0
00000
/:1
1
11
1
mmf
A
A
p
p
MU
U
fM
ApMam
f
eee


=





−





+





−+=





=
γγ
TT
Air Breathing Jet Engines
106
Turbojet
SOLO
Thrust Computation for Air Breathing Engines (continue – 2)
00 ,Up
0A
eA
ee Up ,
000
0
00
00 11
:
ApMg
a
famg
a
m
m
gmWeightFuelBurned
ForceThrust
I
ff
sp
TTT






====
γ


Specific Impulse
0000
11
ApMfa
gIsp T






=
γ
Specific Fuel Consumption (SFC)
spIg
f
ThrustofPound
HourperBurnedFuelofPound
S
1
: ====
0
f
mT/T
m


Air Breathing Jet Engines
107
Air Breathing Jet Engines
PRESSURE
Compressor
Pressure
Rise
Turbine
Pressure
Drop
(Turbojet)
Heat Added in
Combustion Chambers
by burning mfuel mass
TOTAL TEMPERATURE
mfuel_1
mfuel_2
mfuel_3
mfuel_1 >mfuel_2>mfuel_3
Pressure corresponding to
mfuel_1 and Thrust1
Pressure corresponding to
mfuel_2 and Thrust2
Pressure corresponding to
mfuel_3 and Thrust3A
B1
B2
B3
C1
D1
C2
D2
C3
D3
Thrust1 >Thrust2>Thrust3
E
108
Air Breathing Jet Engines
PRESSURE
Compressor
Pressure
Rise
Turbine
Pressure
Drop
(Turbojet)
Heat Added in
Combustion Chambers
by burning mfuel mass
TOTAL TEMPERATURE
Pressure corresponding to
mfuel and ThrustA
B
C
D1
F
E
Additional Turbine
Pressure Drop
in Turboprop
109
( )[ ] ( ) 0000 /:1 mmfAppUUfm feee
 =−+−+=T
00 ,Up
0A
eA
ee Up ,
Aircraft Propulsion SystemSOLO
0000 UAm ρ=
The change in altitude (air density) will affect the thrust as follows
As U0 increases Ue doesn’t change (at the first order), since the value of Ue depends more of the
internal compression and combustion processes inside the engine than on the U0. Therefore Ue – U0
will decrease. Since increase in U0 increases ṁ0 , the Thrust T will remain, at first order, constant.
0UwithconstantelyapproximatisT
..LSS.L. ρ
ρ
=
T
T
Sensitivity of Thrust and Specific Fuel Consumption with
Velocity and Altitude for a Jet Engine
J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999
The Specific Fuel Consumption increases with Mach at subsonic velocity (see Figure next slide)
11 00 <+= MMkTSFC
The Specific Fuel Consumption is constant with altitude at subsonic velocity (see Figure next slide)
altitudewithconstantisTSFC
110
Typical results for the variation of Thrust and Thrust Specific Fuel Consumption with
Subsonic Mach number for a Turbojet
J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999
Aircraft Propulsion SystemSOLO
Sensitivity of Thrust and Specific Fuel Consumption with
Velocity and Altitude for a Jet Engine
111
Typical results for the variation of Thrust
and Thrust Specific Fuel Consumption
with Supersonic Mach number for a
Turbojet
J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999
Aircraft Propulsion SystemSOLO
Sensitivity of Thrust and Specific Fuel Consumption with
Velocity and Altitude for a Jet Engine
Supersonic Conditions
1
2
2
1
1
−





 −
+=
γ
γ
γ
M
p
p
static
total
Ptotal is the pressure entering the
Compressor from the Diffuser,
that further increases the
pressure and therefore the exit
Velocity Ue and the Thrust.
From the Figure we obtain that
for the specific aircraft the
Supersonic Thrust is given by
( )118.11 0
1
−+=
=
M
MT
T
..LSS.L. ρ
ρ
=
T
T
The Specific Fuel Consumption is constant with Mach at supersonic velocity (see Figure)
The Specific Fuel Consumption is constant with altitude at supersonic velocity (see Figure)
altitudewithconstantisTSFC
10 >MMachwithconstantisTSFC
112
H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35
Turbojet Performance
Aircraft Propulsion SystemSOLO
Return to Table of Content
113
SOLO
Thrust Augmentation – Reheat in an Afterburner
Aircraft Propulsion System
To achieve Take-Off from a Short Runway a Fighter Aircraft needs additional Thrust. This is also necessary in
Dogfight Combat to increase Aircraft Maneuverability.
A very effective and widely used method to increase Thrust is by Reheat or Afterburning which enables Thrust
to be increased by 50 percent. The technology of Reheat is possible because the hot gas after passing the Turbine,
still contains enough oxygen to allow a Second Combustion given additional Fuel is Injected. (Only part of the
air is discharged by the Compressor is used for Combustion, the greater part is used for Cooling).
The Afterburner is a Tube-like structure attached to the Gas Generator immediately
behind the Turbine. The forward part is designed as a Diffuser (increasing cross-
section) which decrease flow velocity from Mach 0.5 to 0.2. It consists of the following
four components:
- Flame Tube
- Fuel Injection System
- Flame Holder Assembly (prevent Flame for being carried away)
- Variable Geometry Exhaust Nozzle
Afterburner
114
SOLO
Ideal Turbojet Engine with Afterburner
Pressure-Volume Diagram Temperature-Entropy
Diagram
Ideal Turbojet with Afterburner
eA
ee Up ,
00 ,Up
0A
Air Breathing Jet Engines
Typical afterburning jet pipe equipment.
Afterburner
Return to Table of Content
115
Thrust Reversal Operation
(Used during Landing)
Aircraft Propulsion SystemSOLO
Return to Table of Content
116
Typical results for the variation of Thrust and Thrust Specific Fuel Consumption with
Subsonic Mach number for Turbojet
J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999
Aircraft Propulsion SystemSOLO
Altitude variation
T/T0 = ρ/ρ0
Velocity variation
1.Subsonic: T is constantwithV’
2. Supersonic: T/Tm=1=1+1.18 (M’-1)
Velocity variation
1. Subsonic: TSFC= 1.0+k M’
2. Supersonic: TSFCis constant’
Altitude variation
SFCis constantwith Altitude
Specificfuel
Consumption
Power
PA =T V’
Turbojet
Engine
Aircraft Propulsion Summary
117
Altitude variation
T/T0=(ρ/ρ0 )m
Velocity variation
1High bypassratio:T/TV=0=AM’
-n
2.Lowbypassratio:TfirstincreaseswithM’
then decreasesathigh supersonicM’
Velocity variation
1.High Bypassct =B(1.0+kM’ )
2.LowBypass:ct graduatelyincreaseswithvelocity
Altitude variation
ct isconstantwith Altitude
Specificfuel
Consumption
Power
PA =TV’
Turbofan
Engine
J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999, pg.186
Aircraft Propulsion Summary
Aircraft Propulsion SystemSOLO
118
Velocityvariation
PA isconstantwithM’
Altitude variation
PA/PA,0 =(ρ/ρ0)m
Velocityvariation
CA isconstantwithV’
Altitude variation
CA isconstantwithAltitude
Specificfuel
Consumption
Power
PA=(TP+Tj)V’
PA=hpr PS+Tj V’
PA=hpr Pes
Turboprop
Engine
J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999, pg.186
Aircraft Propulsion
Summary
Block Diagram
Aircraft Propulsion SystemSOLO
Aircraft Propulsion Summary
119
Altitude variation
1. P/P0 = ρ/ρ0
2. (slightly more accurate) P/P0 =1.132 ρ/ρ0-0.132
Velocity variation
Shaft Power P constant with V’
Velocity variation
SFC is constant with V’
Altitude variation
SFC is constant with Altitude
Altitude variation
T/T0 = ρ/ρ0
Velocity variation
1.Subsonic: T is constant with V’
2. Supersonic: T/Tm=1=1+1.18 (M’-1)
Velocity variation
1. Subsonic: TSFC = 1.0+k M’
2. Supersonic: TSFC is constant’
Altitude variation
SFC is constant with Altitude
Altitude variation
T/T0 =( ρ/ρ0 )m
Velocity variation
1High bypass ratio: T/TV=0=A M’
-n
2. Low bypass ratio: T first increases with M’
then decreases at high supersonic M’
Velocity variation
1. High Bypass ct = B (1.0+k M’ )
2.Low Bypass: ct graduately increases with velocity
Altitude variation
c t is constant with Altitude
Velocity variation
PA is constant with M’
Altitude variation
PA/PA,0 = (ρ/ρ0)m
Velocity variation
CA is constant with V’
Altitude variation
CA is constant with Altitude
Specific fuel
Consumption
Specific fuel
Consumption
Specific fuel
Consumption
Specific fuel
Consumption
Power
PA =T V’
Power
PA =T V’
Power
PA = hpr P
hpr = f (J)
J = V’/(N D)
Power
PA =(TP+Tj) V’
PA = hpr PS+Tj V’
PA = hpr Pes
Reciprocating Engine/
Propeller Combination
Turbojet
Engine
Turbofan
Engine
Turboprop
Engine
Propulsion Systems
J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999, pg.186
Aircraft Propulsion
Summary
Block Diagram
Aircraft Propulsion SystemSOLO
120
Air Breathing Jet Engines
0m
T
Aircraft Propulsion Summary
SOLO
121
Air Breathing Jet Engines
Aircraft Propulsion Summary
SOLO
122
Air Breathing Jet Engines
Aircraft Propulsion Summary
SOLO
123
SOLO
Propulsive Efficiency Characteristics of Turboprop, Turbofan and Turbojet Engines
Air Breathing Jet Engines
Return to Table of Content
Propulsive Efficiency Summary
124Stengel, MAE331, Lecture 6
Thrust of a Propeller-
Driven Aircraft
• With constant r.p.m., variable-pitch propeller
where
ηp - propeller efficiency
ηI - ideal propulsive efficiency
ηnet-max ≈ 0.85 – 0.9
Efficiency decrease with airspeed
Engine power decreases with altitude
- Proportional with air density w/o supercharger
V
P
V
P
T
engine
net
engine
Ip ηηη ==
Variation of Thrust and Power of a Propeller-Driven Aircraft with True Airspeed
Aircraft Propulsion Summary
SOLO Aircraft Propulsion System
125
Thrust as a function of airspeed for different Propulsion Systems
Aircraft Propulsion Summary
SOLO Aircraft Propulsion System
126
Stengel, MAE331, Lecture 6
Thrust of a
Turbojet
Engine
( )








−





+−





−





−
= 11
11
2/1
00
0
c
t
c
t
t
VmT
τθ
θ
τ
θ
θ
θ
θ
fuelair mmm  +=
( )
heatsspecificofratio
p
p
ambient
stag
=





=
−
γθ
γγ
,
/1
0






=
etemperaturambientfreestream
etemperaturinletturbine
0θ






=
etemperaturinletcompressor
etemperaturoutletcompressor
cτ
• Little change in thrust with airspeed below Mcrit
• Decrease with increasing altitude
where
Variation of Thrust and Power of a Turbojet Engine with True Airspeed
SOLO Aircraft Propulsion System
127
Stengel, MAE331, Lecture 6
John D. Anderson, Jr., “Introduction to Flight”, McGraw Hill, 1978, § 6.4, pg. 217
B. N. Pamadi, “Performance, Stability, Dynamics and Control of Aircraft”, AIAA
SOLO Aircraft Propulsion System
128
Power and Thrust
• Propeller
• Turbojet
• Throttle Effect
airspeedoftindependenSVCVTPPower T ≈=•== 3
2
1
ρ
airspeedoftindependenSVCTThrust T ≈== 2
2
1
ρ
10
2
1 2
max max
≤≤== TSVTCTTT T δρδδ
Specific Fuel Consumption, SFC = cP or cT
• Propeller aircraft
• Jet aircraft
[ ]
[ ]






→
→
=
−=
−=
lbf
slb
or
kN
skg
c
HP
slb
or
kW
skg
c
weightfuelw
where
thrusttoalproportionTcw
powertoalproportionPcw
T
P
f
Tf
Pf
//
//
SOLO Aircraft Propulsion System
Return to Table of Content
129Dr. Carlo Kopp, Air Power Australia,
Sukhoi Su-34 Fullback, Russia's New Heavy Strike Fighter
Comparison of Fighter Aircraft Propulsion Systems
SOLO
130
Comparison of Fighter Aircraft Propulsion Systems
SOLO
131
Comparison of Fighter Aircraft Propulsion Systems
SOLO
132M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring”
Comparison of Fighter Aircraft Propulsion Systems
SOLO
133M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring”
Comparison of Fighter Aircraft Propulsion Systems
SOLO
134M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring”
Comparison of Fighter Aircraft Propulsion Systems
SOLO
135M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring”
Comparison of Fighter Aircraft Propulsion Systems
SOLO
136M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring”
Return to Table of Content
Comparison of Fighter Aircraft Propulsion Systems
SOLO
137
SOLO Aircraft Propulsion System
VTOL - Vertical Take off and Landing capability
The advantages of vertical take off and landing VTOL are quite obvious.
Conventional aircraft have to operate from a small number of airports with
long runways. VTOL aircraft can take off and land vertically from much
smaller areas.
STOL - Short takeoff and landing
These aircraft using thrust vectoring to decrease the distance needed for
takeoff and landing but don’t have enough thrust vectoring capability to
perform a vertical take off or landing.
VSTOL - An aircraft that can perform either vertical or short takeoff and landings
STOVL - Short takeoff and vertical land.
An aircraft that has insufficient lift for vertical flight at takeoff weight but
can land vertically at landing weight.
TVC - Thrust Vector Control
Vertical Take off and Landing - VTOL
138
SOLO
Vertical Take off and Landing - VTOL
139M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring”
140
Lockheed_Martin_F-35_Lightning_II STOVL
The Unique F-35
Fighter Plane, Movie
USP 3” part F35
Joint Strike Fighter ENG,
Movie
SOLO Aircraft Propulsion System
Thrust vectoring nozzle
of the F135-PW-600
STOVL variant
Return to Table of Content
141
Aircraft Propulsion System
SOLO
Engine Control System
Engine Control System
Basic Inputs and Outputs
Engine Control System
Input Signals:
• Throttle Position (Pilot Control)
• Air Data (from Air Data Computer)
Airspeed and Altitude
• Total Temperature (at the Engine
Face)
• Engine Rotation Speed
• Engine Temperature
• Nozzle Position
• Fuel Flow
• Internal Pressure Ratio at different Stages of the Engine
Output Signals
• Fuel Flow Control
• Air Flow Control
142
Aircraft Propulsion SystemSOLO
The Fighter Aircraft Propulsion Systems Consists of:
- One or Two Jet Engines
- The Fuel Tanks (Internal and External) and Pipes.
- Engines Control Systems
* Throttles
* Engine Control Displays
Engine Control Systems – Basic Inputs and Outputs
143
Aircraft Propulsion SystemSOLO
A Simple Engine Control Systems :
Pilot in the Loop
A Simple Limited Authority
Engine Control Systems
TGT – Turbine Gas Temperature
NH – Speed of Rotation of Engine Shaft
Tt - Total Temperature
FCU – Fuel Control Unit
Engine Control System
144
Aircraft Propulsion SystemSOLO
A Simple Engine Control Systems :
Pilot in the Loop
A Simple Limited Authority
Engine Control Systems
Engine Control Systems :
with NH and TGT exceedance warning
Full Authority Engine Control Systems
With Electrical Throttle Signaling :
Engine Control System Return to Table of Content
145
Aircraft Flight ControlSOLO
146
center stickailerons
elevators
rudder
Aircraft Flight Control
Generally, the primary cockpit flight controls are arranged as follows:
a control yoke (also known as a control column), center stick or side-stick (the
latter two also colloquially known as a control or B joystick), governs the
aircraft's roll and pitch by moving the A ailerons (or activating wing warping
on some very early aircraft designs) when turned or deflected left and right,
and moves the C elevators when moved backwards or forwards
rudder pedals, or the earlier, pre-1919 "rudder bar", to control yaw, which move
the D rudder; left foot forward will move the rudder left for instance.
throttle controls to control engine speed or thrust for powered aircraft.
SOLO
147
Stick
Stick
Rudder
Pedals
Aircraft Flight ControlSOLO
148
The effect of left rudder pressure Four common types of flaps
Leading edge high lift devices
The stabilator is a one-piece horizontal tail surface that
pivots up and down about a central hinge point.
Aircraft Flight ControlSOLO
SOLO
149
Flight Control
Aircraft Flight Control
SOLO
150
Aerodynamics of Flight
Aircraft Flight Control
Return to Table of Content
SOLO
-Aerodynamic Forces
( ) ( ) ( )
( ) ( ) BTBT
VTrTT
nMqNxMqA
nMqLVMqDMqA
1,,1,,
1,,1,,,,
αα
ααα
+−=
+−=

( )MqD T ,,α -Drag Force
( )MqN T ,,α -Normal Force
Mq T ,,α -Dynamic Pressure, Total Angle of Attack, Mach Number
( ) ( )
( ) ( )MCSVhD
MCSVhL
TD
q
r
TL
q
r
,
2
1
,
2
1
2
2
αρ
αρ


=
=
Aerodynamic Forces (Vectorial)
( )MqA T ,,α -Axial Drag Force
( )MqL T ,,α -Lift Force
( ) ( )
( ) ( )MCSVhA
MCSVhN
TA
q
r
TN
q
r
,
2
1
,
2
1
2
2
αρ
αρ


=
=




+=
−=
TBTBV
TBTBr
nxn
nxV
αα
αα
cos1sin11
sin1cos11




−=
+=
TVTrB
TVTrB
nVn
nVx
αα
αα
cos1sin11
sin1cos11
Aircraft Equations of Motion
SOLO
-Aerodynamic Forces
( ) ( ) ( )
( ) ( ) BTBT
VTrTT
nMqNxMqA
nMqLVMqDMqA
1,,1,,
1,,1,,,,
αα
ααα
+−=
+−=

are coplanar( )01,11,1 ≠TVBrB nnandVx α
( ) ( )
T
rBT
rB
rBrB
rB
rB
BB
Vx
Vx
VxVx
Vx
Vx
xn
α
α
sin
11cos
11
1111
11
11
11
−
=
×
−•
=
×
×
×=
( ) ( )
T
rTB
rB
rrBB
rB
rB
rV
Vx
Vx
VVxx
Vx
Vx
Vn
α
α
sin
1cos1
11
1111
11
11
11
−
=
×
•−
=
×
×
×=




+=
−=
TBTBV
TBTBr
nxn
nxV
αα
αα
cos1sin11
sin1cos11




+−=
+=
TVTrB
TVTrB
nVn
nVx
αα
αα
cos1sin11
sin1cos11
Aerodynamic Forces (Vectorial)
Aircraft Equations of Motion
SOLO
-Aerodynamic Forces
( ) ( ) ( )
( ) ( ) BTBT
VTrTT
nMqNxMqA
nMqLVMqDMqA
1,,1,,
1,,1,,,,
αα
ααα
+−=
+−=

( ) ( )
( ) ( )MCSVhD
MCSVhL
TD
q
r
TL
q
r
,
2
1
,
2
1
2
2
αρ
αρ


=
=
( ) ( )
( )
( ) ( )MCSVhA
MCSVhN
TA
q
r
MC
TN
q
r
TN
,
2
1
,
2
1
2
2
αρ
αρ
αα



=
=
( ) ( ) ( ) ( )[ ]
( ) ( ) ( )[ ]
( ) ( ) ( )[ ]
MAXT
VTTNTTAr
rTTNTTAr
VTLrTDT
nMCMCSVh
VMCMCSVh
nMCVMCSVhMqA
αα
ααααρ
ααααρ
ααρα
≤
++
+−=
+−=
1cos,sin,
2
1
1sin,cos,
2
1
1,1,
2
1
,,
2
2
2

Aerodynamic Forces (Vectorial)
Aircraft Equations of Motion
154
SOLO
Drag ,Lift Coefficients as functions of Angle of Attack
Drag Polar
Drag Polar
Aircraft Equations of Motion
02/28/15 155
SOLO
By changing αT from 0 to αMAX, and rotating around
by σ (from 0 to σMAX) we obtain a Surface of Revolution
Σq (CA,CN) which defines the Achievable Aerodynamic
Forces for the given dynamic pressure q.
rV1
( )
( )
VzVyV
MAXT
soundr
r
windr
nnn
hVVM
VShq
vRVV
1sin1cos1
/
2
1 2
σσ
αα
ρ
+=
≤
=
=
−×Ω−=

( ) ( ) ( )
( ) ( ) VTLrTD
VTrTT
nMCqVMCq
nMqLVMqDMqA
1,1,
1,,1,,,,
αα
ααα
+−=
+−=

( ) ( )
T
rTB
rB
rrBB
rB
rB
rV
Vx
Vx
VVxx
Vx
Vx
Vn
α
α
sin
1cos1
11
1111
11
11
11
−
=
×
⋅−
=
×
×
×=
( )σα,A

V

α
MAXα
( )DL CC ,Σ
σ
MAXσ
( ) ( )αα
2
0 LDD CkCC +=
D
σcosL
σsinL
σ
MAXσ
L
L
Aerodynamic Forces (Vectorial)
Aircraft Equations of Motion
02/28/15 156
SOLO
We can see that for αT = 0
( ) ( )
( )
( )
( )


MA
Ar
MD
DT
TT
MCqVMCqMqA
,0
0
,0
0 1,0,
==
−=−==
αα
α
( ) ( )Rg
m
T
V
m
MCq
V r
D 


++−= 10
and since for αT = 0
the aerodynamic forces will
decrease the velocity.
We can see that for αT ≠ 0, the deceleration
due to aerodynamics will only increase.
( ) ( ) ( )[ ] ( ) ( )MqDMCqMCMCqMqD TATTNTAT ,0,sincos,0, ==>+=≠ ααααα α
The most Energy Effective Trajectory is one with αT = 0.
( )
( )
VzVyV
MAXT
soundr
r
windr
nnn
hVVM
VShq
vRVV
1sin1cos1
/
2
1 2
σσ
αα
ρ
+=
≤
=
=
−×Ω−=

( ) ( )
T
rTB
rB
rrBB
rB
rB
rV
Vx
Vx
VVxx
Vx
Vx
Vn
α
α
sin
1cos1
11
1111
11
11
11
−
=
×
⋅−
=
×
×
×=
( ) ( ) ( )
( ) ( ) VTLrTD
VTrTT
nMCqVMCq
nMqLVMqDMqA
1,1,
1,,1,,,,
αα
ααα
+−=
+−=

Aerodynamic Forces (Vectorial)
Aircraft Equations of Motion
Return to Table of Content
02/28/15 157
SOLO
Specific Energy
( ) ( )RgTA
m
V

++=
1
( ) ( ) ( ) VTrTT nMqLVMqDMqA 1,,1,,,, ααα +−=

By Integrating this Equation we obtain:
( ) ( )∫∫ +⋅=








⋅−
⋅
=−
t
t
t
t
dtTAV
gm
dt
g
Rg
V
g
VV
EE
00 000
0
1 
( ) ( ) ( )∫∫∫∫ ∫ +⋅=⋅
−
−
−
=⋅−
⋅
=








⋅−
⋅
=−
t
t
R
R dRR
E
R
R
t
t
V
V
dtTAV
gm
RdR
Rgg
VV
Rd
g
Rg
g
VdV
dt
g
Rg
V
g
VV
EE
0000 0
0
3
00
2
0
2
0000
0
11
2


 





µ
Define Specific Energy Derivative:
( ) ( )TAV
mg
Rg
V
g
VV
E

 +⋅=⋅−
⋅
=
1
:
00
2
0
0 :
R
g Eµ
=
( )∫ +⋅=







−−





−=





−−
−
=−
t
t
EEE
dtTAV
gmRgg
V
Rgg
V
RRgg
VV
EE
0 0000
2
0
00
2
000
2
0
2
0
1
22
11
2
µµµ
Aircraft Equations of Motion
02/28/15 158
SOLO
Specific Energy (continue – 1)
( ) ( )∫∫ +⋅=








⋅−
⋅
=−
t
t
t
t
dtTAV
gm
dt
g
Rg
V
g
VV
EE
00 000
0
1 
0
2
0
2
00 20 0
g
VV
g
VdV
dt
g
VV
t
t
V
V
−
=
⋅
=
⋅
∫ ∫



( ) ( )
( )
( ) 0
3
0
3
2
0
02
0
2
2
2
0
3
2
0
00
0
0
0
0
00
3
2
0
0
00
3
2
21 hhhh
R
hhhd
R
h
Rd
R
R
RdR
R
R
Rd
g
Rg
dt
g
Rg
V
Rhh
h
hRR
Rh
R
R
dRRRdRR
R
R
R
Rg
R
g
R
R
t
t
RddtV
E
E
−≈−−−=







−≈
=⋅=⋅−=





⋅−
<<+=
<<
=⋅
−=
=
=
∫
∫∫∫∫






µ
µ
( ) ( ) ( )[ ]∫∫ −⋅=+⋅
t
t
T
t
t
dtMqDTTV
gm
V
dtTAV
gm 00
,,11
1
00
α

Specific Kinetic Energy
Specific Potential Energy
( ) ( )[ ]∫ −⋅=







+−





+=−
t
t
T dtMqDTTV
gm
V
h
g
V
h
g
V
EE
0
,,11
22 0
0
0
2
0
0
2
0 α
Specific Energy Gain due to Thrust
and Loss due to Aerodynamic Drag
( )011 >⋅ TVif
Aircraft Equations of Motion
Return to Table of Content
SOLO
( ) ( )
( ) ( ) ( ) ( )
( ) ( )






≥==−=
≥+×Ω=−=++=
===
min00
min00
00
/
1
mmtmmtmcTm
VVvRtVRpATTRgTA
m
V
RtRRtRVR
ffvacuum
fwindaevacuum
ff



Equations of Motion (State Equations): . ( ) ( ) fttttuxftx ≤≤= 0,,, π
Controls: ( ) fttttu ≤≤0
VectorThrustT
ForcescAerodynamiA
−
−


Three Degrees of Freedom Model in Earth Atmosphere
160
SOLO Aircraft Equations of Motion
161
SOLO
• Rotation Matrix from Earth to Wind Coordinates
[ ] [ ] [ ]321 χγσ=W
EC
where
σ – Roll Angle
γ – Elevation Angle of the Trajectory
χ – Azimuth Angle of the Trajectory
Force Equation:
amgmTFA

=++
where:
• Aerodynamic Forces (Lift L and Drag D)
( )










−
−
=
L
D
F
W
A 0

• Thrust T ( )










=
α
α
sin
0
cos
T
T
T W

• Gravitation acceleration
( ) ( )




















−









 −










−
==
g
cs
sc
cs
sc
cs
scgCg EW
E
W
0
0
100
0
0
0
010
0
0
0
001
χχ
χχ
γγ
γγ
σσ
σσ
( )
g
cc
cs
s
g W









−
=
γσ
γσ
γ

α
T
V
L
D
Bx
Wx
Bz
Wz
Wy
By
Flat Earth Three Degrees of Freedom Aircraft Equations
162
SOLO
α
T
V
L
D
Bx
Wx
Bz
Wz
Wy
By
• Aircraft Acceleration
( )
( )
( ) ( )WW
W
W
VVa

×+=
→
ω
where:
( )










=
0
0
V
V W

and
( )










=
→
0
0
V
V
W


( )








































−+



















 −
+




















−
=










=
χ
χχ
χχ
γ
γγ
γγσ
σσ
σσω




0
0
100
0
0
0
0
0
010
0
0
0
0
0
001
cs
sc
cs
sc
cs
sc
r
q
p
W
W
W
W
or ( )










+−
+
−
=










=
γσχσγ
γσχσγ
γχσ
ω
ccs
csc
s
r
q
p
W
W
W
W




therefore
( )
( )
( ) ( )
( )
( ) 









+−
+−=










−
=×+=
→
γσχσγ
γσχσγω
cscV
ccsV
V
qV
rV
V
VVa
W
W
WW
W
W




Flat Earth Three Degrees of Freedom Aircraft Equations
163
SOLO
α
T
V
L
D
Bx
Wx
Bz
Wz
Wy
By
• Aircraft Acceleration
Flat Earth Three Degrees of Freedom Aircraft Equations
From the Force equation we obtain:
( )
( )
( ) ( ) ( ) ( )
( ) ( )WWW
A
WW
W
W
gTF
m
VVa

++=×+=
→
1
ω
or
( )
( ) ( )




++−=+−=−
=+−=
−−=
γσαγσχσγ
γσγσχσγ
γα
ccgmLTcscVqV
csgccsVrV
sgmDTV
W
W
/sin
/)cos(



from which we obtain:






−
+
=
=
γσ
α
γσ
coscos
sin
cossin
V
g
Vm
LT
q
V
g
r
W
W
164
SOLO
α
T
V
L
D
Bx
Wx
Bz
Wz
Wy
By
• Aircraft Acceleration
Flat Earth Three Degrees of Freedom Aircraft Equations
From the Force equation we obtain:
( )
( )
( ) ( ) ( ) ( )
( ) ( )WWW
A
WW
W
W
gTF
m
VVa

++=×+=
→
1
ω
or
( )
( ) ( ) σ
σ
σ
σ
γσαγσχσγ
γσγσχσγ
γα
s
c
c
s
ccgmLTcscVqV
csgccsVrV
sgmDTV
W
W
−−
−





++−=+−=−
=+−=
−−=
/sin
/)cos(



from which we obtain:
( )
( )




+=
−+=
−−=
msLTcV
cgmcLTV
sgmDTV
/sin
/sin
/)cos(
σαγχ
γσαγ
γα



Define the Load Factor
gm
LT
n
+
=
αsin
:
165
SOLO
α
T
V
L
D
Bx
Wx
Bz
Wz
Wy
By
• Velocity Equation
Flat Earth Three Degrees of Freedom Aircraft Equations
( ) ( )










==










=
0
0
V
CVC
h
y
x
V E
W
WE
W
E

























−










−








 −
=










0
0
0
0
001
0
010
0
100
0
0 V
cs
sc
cs
sc
cs
sc
h
y
x
σσ
σσ
γγ
γγ
χχ
χχ








=
=
=
γ
χγ
χγ
sVh
scVy
ccVx



or
• Energy per unit mass E
g
V
hE
2
:
2
+=
Let differentiate this equation:
( )
W
VDT
W
DT
g
g
V
V
g
VV
hEps
−
=











−
−
+=+==
α
γ
α
γ
cos
sin
cos
sin:


Return to Table of Content
166
SOLO
Flat Earth Three Degrees of Freedom Aircraft Equations
We have
Aircraft Thrust( ) 10, ≤≤= ηη VhTT MAX
( ) ( ) soundofspeedhaNumberMachMhaVM === &/
( ) ( )MSCVhL L ,
2
1 2
αρ= Aircraft Lift
( ) ( )LD CMSCVhD ,
2
1 2
ρ= Aircraft Drag
( ) ( )
ARe
k
CkMCCMC
iDC
LDLD
π
1
,
2
0
=
+=
 Parabolic Drag Polar
gm
LT
n
+
=
αsin
' Total Load Number
( ) 0/
0
hh
eh −
= ρρ Air Density as Function of Height
gm
L
n = Load Factor
167
SOLO
Constraints:
State Constraints
• Minimum Altitude Limit
minhh ≥
• Maximum dynamic pressure limit
( ) ( )hVVorqVhq MAXMAX ≤≤= 2
2
1
ρ
• Maximum Mach Number limit
( ) MAXM
ha
V
≤
Aerodynamic or heat limitation
Three Degrees of Freedom Model in Earth Atmosphere
168
SOLO
Constraints:
• Maximum Load Factor
( )
MAXn
W
VhL
n ≤=
,
• Maximum Roll Angle
MAXMAX σσσ ≤≤−
• Maximum Lift Coefficient or Maximum Angle of Attack
( ) ( ) ( )VhorMCMC STALLMAXLL ,, _ ααα ≤≤
( )
( )
( ) ( ) ( ) LSTALL
LMAXL
nVh
W
VhC
VSh
W
VhC
VShn ==≤ ,
,
2
1,
2
1 2_2
αρρ α
Control Constraints (continue): ( ) fttttuU ≤≤≤ 00,
Three Degrees of Freedom Model in Earth Atmosphere
02/28/15
169
SOLO
Control Constraints: ( ) fttttuU ≤≤≤ 00,
• Thrust Controls options are:
Thrust Direction
Thrust Magnitude
( ) throttableVhTT rMAX 10, ≤≤= ηη
Deflector Nozzle
Thrust Reversal Operation
F-35 Propulsion
If no Thrust Vector Control (No TVC)
BxT 11 =
1cos111 max ≤≤•≤− TBxT δ
If Thrust Vector Control (TVC)
Three Degrees of Freedom Model in Earth Atmosphere
02/28/15 170
( ) ( )
( ) ( ) ( )( )
( )
( ) ( ) ( )( )
( )
( ) ( )( ) ( ) ( )
γ
χ
γ
χγ
χγσ
γ
α
σ
γ
βα
χ
χγγ
χγσ
α
σ
βα
γ
χγγ
γ
βα
χγ
χγ
γ
cos
sincossin
cos
sincoscostan2
tansincossin
cos
sin
cos
cos
sincos
cossinsincoscoscos
coscos2coscos
sin
sin
sincos
sinsincoscossincos
sin
coscos
sincos
cos
coscos
cos
sin
*
2
*
2
2
*
V
a
LatLat
V
R
LatLat
Lat
R
V
Vm
LT
Vm
CT
V
a
LatLatLat
V
R
Lat
V
g
R
V
Vm
LT
Vm
CT
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SOLO Three Degrees of Freedom Model in Earth Atmosphere
02/28/15 171
(b) Spherical, Non-Rotating Earth (Ω = 0)
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SOLO Three Degrees of Freedom Model in Earth Atmosphere
02/28/15 172
σ
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SOLO Three Degrees of Freedom Model in Earth Atmosphere
02/28/15
173
(a) Spherical, Rotating Earth (Ω ≠ 0)
(b) Spherical, Non-Rotating Earth (Ω = 0)
(c) Flat Earth
0→Ω
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Vm
LT
Vm
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g
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m
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SOLO
∞→R
Three Degrees of Freedom Model in Earth Atmosphere
Return to Table of Content
174
References
SOLO
Miele, A., “Flight Mechanics , Theory of Flight Paths, Vol I”, Addison Wesley,
1962
Aircraft Flight Performance
J.D. Anderson, Jr., “Introduction to Flight”, McGraw Hill, 1978, Ch. 6, “Elements
of Airplane Performance”
A. Filippone, “Flight Performance of Fixed and Rotary Wing Aircraft”,
Elsevier, 2006
M. Saarlas, “Aircraft Performance”, John Wiley & Sons, 2007
Stengel, MAE 331, Aircraft Flight Dynamics, Princeton University
J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999
N.X. Vinh, “Flight Mechanics of High-Performance Aircraft”,
Cambridge University Press, 1993
F.O. Smetana, “Flight Vehicle Performance and Aerodynamic
Control”, AIAA Education Series, 2001
L. George, J.F. Vernet, “La Mécanique du Vol, Performances des
Avions et des Engines”, Librairie Polytechnique Ch. Béranger, 1960
L.J. Clancy, “Aerodynamics”, Pitman International Text, 1975
175
Brandt, “Introduction to Aerodynamics – A Design Perspective”, Ch. 5 ,
Performance and Constraint Analysis
SOLO
Aircraft Flight Performance
J.D. Mattingly, W.H. Heiser, D.T. Pratt, “Aircraft Engine Design”, 2nd
Ed., AIAA
Education Series, 2002
Prof. Earll Murman, “Introduction to Aircraft Performance and Static Stability”,
September 18, 2003
Naval Air Training Command, “Air Combat Maneuvering”, CNATRA P-1289
(Rev. 08-09)
Patrick Le Blaye, “Agility: Definitions, Basic Concepts, History”, ONERA
Randal K. Liefer, John Valasek, David P. Eggold, “Fighter Aircraft Metrics,
Research , and Test”, Phase I Report, KU-FRL-831-2
References (continue – 1)
B. N. Pamadi, “Performance, Stability, Dynamics, and Control of Airplanes”,
AIAA Educational Series, 1998, Ch. 2 , Aircraft Performance
L.E. Miller, P.G. Koch, “Aircraft Flight Performance”, July 1978, AD-A018 547,
AFFDL-TR-75-89
176
Courtland_D._Perkins,_Robert_E._Hage, “Airplane Performance Stability and
Control”, John Wiley & Sons, 1949
SOLO
Asselin, M., “Introduction to Aircraft Aerodynamics”, AIAA Education Series, 1997
Aircraft Flight Performance
References (continue – 2)
Donald R. Crawford, “A Practical Guide to Airplane Performance and Design”,
Crawford Aviation, 1981
Francis J. Hale, “ Introduction to aircraft performance, Selection and
Design”, John Wiley & Sons, 1984
J. Russell, ‘Performance and Stability of Aircraft“, Butterworth-Heinemann, 1996
Jan Roskam, C. T. Lan, “Airplane Aerodynamics and Performance”,
DARcorporation, 1997
Nono Le Rouje, “Performances of light aircraft”, AIAA, 1999
Peter J. Swatton, “Aircraft performance theory for Pilots”, Blackwell Science,
2000
S. K. Ojha, “Flight Performance of Aircraft “, AIAA, 1995
W. Austyn Mair, David L._Birdsall, “Aircraft Performance”,
Cambridge University Press, 1992
177
SOLO
E.S. Rutowski, “Energy Approach to the General Aircraft Performance Problem”, Journal of
the Aeronautical Sciences, March 1954, pp. 187-195
Aircraft Flight Performance
References (continue – 3)
A.E. Bryson, Jr., “Applications of Optimal Control Theory in Aerospace Engineering”,
Journal of Spacecraft and Rockets, Vol. 4, No.5, May 1967, pp. 553
W.C. Hoffman, A.E. Bryson, Jr., “A Study of Techniques for Real-Time, On-Line Optimum
Flight Path Control”, Aerospace System Inc., ASI-TR-73-21, January 1973, AD 758799
A.E. Bryson, Jr., “A Study of Techniques for Real-Time, On-Line Optimum Flight Path
Control. Algorithms for Three-Dimensional Minimum-Time Flight Paths with Two State
Variables”, AD-A008 985, December 1974
M.G. Parsons, A.E. Bryson, Jr., W.C. Hoffman, “Long-Range Energy-State
Maneuvers for Minimum Time to Specified Terminal Conditions”, Journal of
Optimization Theory and Applications, Vol.17, No. 5-6, Dec 1975, pp. 447-463
A.E. Bryson, Jr., M.N, Desai, W.C. Hoffman, “Energy-State Approximation in Performance
Optimization of Supersonic Aircraft”, Journal of Aircraft, Vol.6, No. 6, Nov-Dec 1969, pp.
481-488
178
SOLO
Aircraft Flight Performance
References (continue – 4)
Solo Hermelin Presentations http://www.solohermelin.com
• Aerodynamics Folder
• Propulsion Folder
• Aircraft Systems Folder
Return to Table of Content
179
SOLO
Technion
Israeli Institute of Technology
1964 – 1968 BSc EE
1968 – 1971 MSc EE
Israeli Air Force
1970 – 1974
RAFAEL
Israeli Armament Development Authority
1974 –
Stanford University
1983 – 1986 PhD AA
180
181
182M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring”
Comparison Tables
183M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring”
Return to Table of Content
SOLO
184
Aircraft Avionics
185
Ray Whitford, “Design for Air Combat”
R.W. Pratt, Ed., “Flight Control Systems, Practical issues in design and implementation”,
AIAA Publication, 2000
SOLO
SOLO
188
H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35
189
H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35
190
H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35
191
H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35
192http://www.worldaffairsboard.com/military-aviation/62863-comparing-fighter-performance-same-
generations-important-factor-war-2.html
SOLO
193
Aircraft Flight Performance
Drag
SOLO
194
Aircraft Flight Performance
Drag
SOLO
195
Aircraft Flight Performance
Drag
196
http://indiandefence.com/threads/comparing-modern-western-fighters.41124/page-16
197
http://selair.selkirk.bc.ca/training/aerodynamics/range_jet.htm
198
http://defence.pk/threads/design-characteristics-of-canard-non-canard-fighters.178592/
199
http://defence.pk/threads/design-characteristics-of-canard-non-canard-fighters.178592/
200
201http://www.ausairpower.net/jsf.html
202http://www.ilbe.com/index.php?
document_srl=2330174362&mid=military&page=406&sort_index=readed_count&order_type=
203

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13 fixed wing fighter aircraft- flight performance - i

  • 1. Fixed Wing Fighter Aircraft Flight Performance Part I SOLO HERMELIN Updated: 04.12.12 28.02.15 1 http://www.solohermelin.com
  • 2. Table of Content SOLO Fixed Wing Aircraft Flight Performance 2 Introduction to Fixed Wing Aircraft Performance Earth Atmosphere Aerodynamics Mach Number Shock & Expansion Waves Reynolds Number and Boundary Layer Knudsen Number Flight Instruments Aerodynamic Forces Aerodynamic Drag Lift and Drag Forces Wing Parameters Specific Stabilizer/Tail Configurations
  • 3. Table of Content (continue – 1) SOLO 3 Specific Energy Aircraft Propulsion Systems Aircraft Propellers Aircraft Turbo Engines Afterburner Thrust Reversal Operation Aircraft Propulsion Summary Vertical Take off and Landing - VTOL Engine Control System Aircraft Flight Control Aircraft Equations of Motion Aerodynamic Forces (Vectorial) Three Degrees of Freedom Model in Earth Atmosphere Comparison of Fighter Aircraft Propulsion Systems Fixed Wing Fighter Aircraft Flight Performance
  • 4. Table of Content (continue – 2) SOLO Fixed Wing Fighter Aircraft Flight Performance 4 Parameters defining Aircraft Performance Takeoff (no VSTOL capabilities) Landing (no VSTOL capabilities) Climbing Aircraft Performance Gliding Flight Level Flight Steady Climb (V, γ = constant) Optimum Climbing Trajectories using Energy State Approximation (ESA) Minimum Fuel-to- Climb Trajectories using Energy State Approximation (ESA) Maximum Range during Glide using Energy State Approximation (ESA) Aircraft Turn Performance Maneuvering Envelope, V – n Diagram F i x e d W i n g P a r t I I
  • 5. Table of Content (continue – 3) SOLO Fixed Wing Fighter Aircraft Flight Performance 5 Air-to-Air Combat Energy–Maneuverability Theory Supermaneuverability Constraint Analysis Aircraft Combat Performance Comparison References F i x e d W i n g P a r t I I
  • 6. SOLO This Presentation is about Fixed Wing Aircraft Flight Performance. The Fixed Wing Aircraft are •Commercial/Transport Aircraft (Passenger and/or Cargo) •Fighter Aircraft Fixed Wing Fighter Aircraft Flight Performance Return to Table of Content
  • 7. 7 Percent composition of dry atmosphere, by volume ppmv: parts per million by volume Gas Volume Nitrogen (N2) 78.084% Oxygen (O2) 20.946% Argon (Ar) 0.9340% Carbon dioxide (CO2) 365 ppmv Neon (Ne) 18.18 ppmv Helium (He) 5.24 ppmv Methane (CH4) 1.745 ppmv Krypton (Kr) 1.14 ppmv Hydrogen (H2) 0.55 ppmv Not included in above dry atmosphere: Water vapor (highly variable) typically 1% Gas Volume nitrous oxide 0.5 ppmv xenon 0.09 ppmv ozone 0.0 to 0.07 ppmv (0.0 to 0.02 ppmv in winter) nitrogen dioxide 0.02 ppmv iodine 0.01 ppmv carbon monoxide trace ammonia trace •The mean molecular mass of air is 28.97 g/mol. Minor components of air not listed above include: Composition of Earth's atmosphere. The lower pie represents the trace gases which together compose 0.039% of the atmosphere. Values normalized for illustration. The numbers are from a variety of years (mainly 1987, with CO2 and methane from 2009) and do not represent any single source Earth AtmosphereSOLO
  • 9. The basic variables representing the thermodynamics state of the gas are the Density, ρ, Temperature, T and Pressure, p. SOLO 9 The Density, ρ, is defined as the mass, m, per unit volume, v, and has units of kg/m3 . v m v ∆ ∆ = →∆ 0 limρ The Temperature, T, with units in degrees Kelvin ( ͦ K). Is a measure of the average kinetic energy of gas particles. The Pressure, p, exerted by a gas on a solid surface is defined as the rate of change of normal momentum of the gas particles striking per unit area. It has units of N/m2 . Other pressure units are millibar (mbar), Pascal (Pa), millimeter of mercury height (mHg) S f p n S ∆ ∆ = →∆ 0 lim kPamNbar 100/101 25 == ( ) mmHginHgkPamkNmbar 00.7609213.29/325.10125.1013 2 === The Atmospheric Pressure at Sea Level is: Earth Atmosphere
  • 10. 10 Physical Foundations of Atmospheric Model The Atmospheric Model contains the values of Density, Temperature and Pressure as function of Altitude. Atmospheric Equilibrium (Barometric) Equation In figure we see an atmospheric element under equilibrium under pressure and gravitational forces ( )[ ] 0=⋅+−+⋅⋅⋅− APdPPHdAg gρ or ( ) gg HdHgPd ⋅⋅=− ρ In addition, we assume the atmosphere to be a thermodynamic fluid. At altitude bellow 100 km we assume the Equation of an Ideal Gas where V – is the volume of the gas N – is the number of moles in the volume V m – the mass of gas in the volume V R* - Universal gas constant TRNVP ⋅⋅=⋅ * V m M m N == ρ& MTRP /* ⋅⋅= ρ Earth AtmosphereSOLO
  • 11. ( ) mmHginHgkPamkNmbar 00.7609213.29/325.10125.1013 2 === Earth AtmosphereSOLO
  • 12. We must make a distinction between: - Kinetic Temperature (T): measures the molecular kinetic energy and for all practical purposes is identical to thermometer measurements at low altitudes. - Molecular Temperature (TM): assumes (not true) that the Molecular Weight at any altitude (M) remains constant and is given by sea-level value (M0) SOLO 12 T M M TM ⋅= 0 To simplify the computation let introduce: - Geopotential Altitude H - Geometric Altitude Hg Newton Gravitational Law implies: ( ) 2 0         + ⋅= gE E g HR R gHg The Barometric Equation is ( ) gg HdHgPd ⋅⋅=− ρ The Geopotential Equation is defined as HdgPd ⋅⋅=− 0ρ This means that g gE E g Hd HR R Hd g g Hd ⋅         + =⋅= 2 0 Integrating we obtain g gE E H HR R H ⋅         + = Earth Atmosphere
  • 13. 13 Atmospheric Constants Definition Symbol Value Units Sea-level pressure P0 1.013250 x 105 N/m2 Sea-level temperature T0 288.15 ͦ K Sea-level density ρ0 1.225 kg/m3 Avogadro’s Number Na 6.0220978 x 1023 /kg-mole Universal Gas Constant R* 8.31432 x 103 J/kg-mole -ͦ K Gas constant (air) Ra=R*/M0 287.0 J/kg--ͦ K Adiabatic polytropic constant γ 1.405 Sea-level molecular weight M0 28.96643 Sea-level gravity acceleration g0 9.80665 m/s2 Radius of Earth (Equator) Re 6.3781 x 106 m Thermal Constant β 1.458 x 10-6 Kg/(m-s-ͦ K1/2) Sutherland’s Constant S 110.4 ͦ K Collision diameter σ 3.65 x 10-10 m Earth AtmosphereSOLO
  • 14. 14 Physical Foundations of Atmospheric Model Atmospheric Equilibrium Equation HdgPd ⋅⋅=− 0ρ At altitude bellow 100 km we assume t6he Equation of an Ideal Gas TRMTRP a MRR a aa ⋅⋅=⋅⋅= = ρρ / * * / Hd TR g P Pd a ⋅=− 0 Combining those two equations we obtain Assume that T = T (H), i.e. function of Geopotential Altitude only. The Standard Model defines the variation of T with altitude based on experimental data. The 1976 Standard Model for altitudes between 0.0 to 86.0 km is divided in 7 layers. In each layer dT/d H = Lapse-rate is constant. Earth AtmosphereSOLO
  • 15. 15 Layer Index Geopotential Altitude Z, km Geometric Altitude Z; km Molecular Temperature T, ͦ K 0 0.0 0.0 288.150 1 11.0 11.0102 216.650 2 20.0 20.0631 216.650 3 32.0 32.1619 228.650 4 47.0 47.3501 270.650 5 51.0 51.4125 270.650 6 71.0 71.8020 214.650 7 84.8420 86.0 186.946 1976 Standard Atmosphere : Seven-Layer Atmosphere Lapse Rate Lh; ͦ K/km -6.3 0.0 +1.0 +2.8 0.0 -2.8 -2.0 Earth AtmosphereSOLO
  • 16. 16 Physical Foundations of Atmospheric Model • Troposphere (0.0 km to 11.0 km). We have ρ (6.7 km)/ρ (0) = 1/e=0.3679, meaning that 63% of the atmosphere lies below an altitude of 6.7 km. ( ) Hd HLTR g Hd TR g P Pd aa ⋅ ⋅+ =⋅=− 0 00 kmKLHLTT /3.60  −=⋅+= Integrating this equation we obtain ( )∫∫ ⋅ ⋅+ =− H a P P Hd HLTR g P PdS S 0 0 0 1 0 ( ) 0 00 lnln 0 T HLT RL g P P aS S ⋅+ ⋅ ⋅ −= Hence aRL g SS H T L PP ⋅ −       ⋅+⋅= 0 0 0 1 and           −         ⋅= ⋅ 1 0 0 0 g RL S S a P P L T H Earth AtmosphereSOLO Stratosphere Troposphere
  • 17. 17 Physical Foundations of Atmospheric Model Hd TR g P Pd Ta ⋅=− * 0 Integrating this equation we obtain ( )T TaS S HH TR g P P T −⋅ ⋅ −= * 0 ln Hence ( )T Ta T HH TR g SS ePP −⋅ ⋅ − ⋅= * 0 and S STTa T P P g TR HH ln 0 * ⋅ ⋅ += ∫∫ =− H HTa P P T S TS Hd TR g P Pd * 0 • Stratosphere Region (HT=11.0 km to 20.0 km). Temperature T = 216.65 ͦ K = TT* is constant (isothermal layer), PST=22632 Pa Earth AtmosphereSOLO Stratosphere Troposphere
  • 18. 18 Physical Foundations of Atmospheric Model ( )[ ] Hd HHLTR g Hd TR g P Pd SSTaa ⋅ −⋅+⋅ =⋅=− * 00 ( ) ( ) PaPHPkmKLHHLTT SSSSSST 5474.9,/0.1 * ===−⋅−=  Integrating this equation we obtain ( )[ ]∫∫ ⋅ −⋅+ =− H H SSTa P P S S SS Hd HHLTR g P Pd * 0 1 ( )[ ] * * 0 lnln T ST aSSS S T HHLT RL g P P −⋅+ ⋅ ⋅ = Hence ( ) aRL g S T S SSS HH T L PP ⋅ −         −⋅+⋅= 0 * 1 and           −      ⋅+= ⋅ 1 0 * g RL SS S S T S aS P P L T HH Stratosphere Region (HS=20.0 km to 32.0 km). Stratosphere Troposphere Earth AtmosphereSOLO
  • 19. 19 1962 Standard Atmosphere from 86 km to 700 km Layer Index Geometric Altitude km Molecular Temperature , K Kinetic Temperature K Molecular Weight Lapse Rate K/km 7 86.0 186.946 186.946 28.9644 +1.6481 8 100.0 210.65 210.02 28.88 +5.0 9 110.0 260.65 257.00 28.56 +10.0 10 120.0 360.65 349.49 28.08 +20.0 11 150.0 960.65 892.79 26.92 +15.0 12 160.0 1110.65 1022.20 26.66 +10.0 13 170.0 1210.65 1103.40 26.49 +7.0 14 190.0 1350.65 1205.40 25.85 +5.0 15 230.0 1550.65 132230 24.70 +4.0 16 300.0 1830.65 1432.10 22.65 +3.3 17 400.0 2160.65 1487.40 19.94 +2.6 18 500.0 2420.65 1506.10 16.84 +1.7 19 600.0 2590.65 1506.10 16.84 +1.1 20 700.0 2700.65 1507.60 16.70 Earth AtmosphereSOLO
  • 20. 20 1976 Standard Atmosphere from 86 km to 1000 km Geometric Altitude Range: from 86.0 km to 91.0 km (index 7 – 8) 78 /0.0 TT kmK Zd Td = =  Geometric Altitude Range: from 91.0 km to 110.0 km (index 8 – 9) 2/12 8 2 8 2/12 8 1 1 −               − −      − ⋅−=               − −⋅+= a ZZ a ZZ a A Zd Td a ZZ ATT C kma KA KTC 9429.19 3232.76 1902.263 −= −= =   Geometric Altitude Range: from 110.0 km to 120.0 km (index 9 – 10) ( ) kmK Zd Td ZZLTT Z /0.12 99  += −⋅+= Geometric Altitude Range: from 120.0 km to 1000.0 km (index 10 – 11) ( ) ( ) ( ) ( )       + + ⋅−=       + + ⋅−⋅= ⋅−⋅−−= ∞ ∞∞ ZR ZR ZZ kmK ZR ZR TT Zd Td TTTT E E E E 10 10 10 10 10 / exp ξ λ ξλ  KT kmR km E  1000 10356766.6 /01875.0 3 = ×= = ∞ λ Earth AtmosphereSOLO
  • 21. 21 Sea Level Values Pressure p0 = 101,325 N/m2 Density ρ0 = 1.225 kg/m3 Temperature = 288.15 ͦ K (15 ͦ C) Acceleration of gravity g0 = 9.807 m/sec2 Speed of Sound a0 = 340.294 m/sec Earth AtmosphereSOLO Return to Table of Content
  • 22. SOLO Atmosphere Continuum Flow Low-density and Free-molecular Flow Viscous Flow Inviscid Flow Incompressible Flow Compressible Flow Subsonic Flow Transonic Flow Supersonic Flow Hypersonic Flow AERODYNAMICS Fixed Wing Aircraft Flight Performance AERODYNAMICS
  • 23. 23 SOLO Dimensionless Equations Dimensionless Field Equations (C.M.): ( ) 0 ~~~~ =⋅∇+ u t  ρ ∂ ρ∂ ( ) ( )u R u R pG F uu t u eer ~~~~1 3 4~~~~1~~~~1~~~ ~ ~ ~ 2   ⋅∇∇+×∇×∇−∇−=        ∇⋅+ µµρ ∂ ∂ ρ(C.L.M.): ( ) ( )Tk PRt Q uG F u t p Hu t H rer ∇⋅∇−+⋅+⋅⋅∇+=        ∇⋅+ ∂ ∂ 11 ~ ~ ~~~1~~~ ~ ~~~~ ~ ~ ~ 2 ∂ ∂ ρτ ∂ ∂ ρ  (C.E.): Reynolds: 0 000 µ ρ lU Re = Prandtl: 0 0 k C P p r µ = Froude: 0 0 gl U Fr = 0/~ ρρρ = 0/ ~ Uuu = gGG / ~ = ( )2 00/~ Upp ρ= 0/ ~ lUtt = 2 0/ ~ UCTT p=( )2 00/~ Uρττ = 2 0/ ~ UHH = 2 0/ ~ Uhh = 2 0/~ Uee = ( )2 00/~ Uqq ρ= ( )2 / ~ UQQ = ∇=∇ 0 ~ l 0/~ ρρρ = 0/ ~ Uuu = gGG / ~ = ( )2 00/~ Upp ρ= 0/ ~ lUtt = 2 0/ ~ UCTT p=( )2 00/~ Uρττ = 2 0/ ~ UHH = 2 0/ ~ Uhh = 2 0/~ Uee = ( )2 00/~ Uqq ρ= ( )2 / ~ UQQ = ∇=∇ 0 ~ l 0/~ µµµ = 0/ ~ kkk = Dimensionless Variables are: Reference Quantities: ρ0(density), U0(velocity), l0 (length), g (gravity), μ0 (viscosity), k0 (Fourier Constant), λ0 (mean free path) 0/ ~ λλλ = Knudsen l Kn 0 0 : λ = AERODYNAMICS Return to Table of Content
  • 24. 24 SOLO Mach Number Mach number (M or Ma) / is a dimensionless quantity representing the ratio of speed of an object moving through a fluid and the local speed of sound. • M is the Mach number, • U0 is the velocity of the source relative to the medium, and • a0 is the speed of sound Mach: 0 0 a U M = The Mach number is named after Austrian physicist and philosopher Ernst Mach, a designation proposed by aeronautical engineer Jakob Ackeret. Ernst Mach (1838–1916) Jakob Ackeret (1898–1981) m Tk Mo TR a Bγγ ==0 • R is the Universal gas constant, (in SI, 8.314 47215 J K−1 mol−1 ), [M1 L2 T−2 θ−1 'mol'−1 ] • γ is the rate of specific heat constants Cp/Cv and is dimensionless γair = 1.4. • T is the thermodynamic temperature [θ1 ] • Mo is the molar mass, [M1 'mol'−1 ] • m is the molecular mass, [M1 ] AERODYNAMICS
  • 25. 25 SOLO Mach Number – Flow Regimes Regime Mach mph km/h m/s General plane characteristics Subsonic <0.8 <610 <980 <270 Most often propeller-driven and commercial turbofan aircraft with high aspect-ratio (slender) wings, and rounded features like the nose and leading edges. Transonic 0.8-1.2 610- 915 980-1,470 270-410 Transonic aircraft nearly always have swept wings, delaying drag- divergence, and often feature design adhering to the principles of the Whitcomb Area rule. Supersonic 1.2–5.0 915- 3,840 1,470– 6,150 410–1,710 Aircraft designed to fly at supersonic speeds show large differences in their aerodynamic design because of the radical differences in the behavior of flows above Mach 1. Sharp edges, thin airfoil-sections, and all-moving tailplane/canards are common. Modern combat aircraft must compromise in order to maintain low-speed handling; "true" supersonic designs include the F-104 Starfighter, SR-71 Blackbird and BAC/Aérospatiale Concorde. Hypersonic 5.0–10.0 3,840– 7,680 6,150– 12,300 1,710– 3,415 Cooled nickel-titanium skin; highly integrated (due to domination of interference effects: non-linear behaviour means that superposition of results for separate components is invalid), small wings, such as those on the X-51A Waverider High- hypersonic 10.0–25.0 7,680– 16,250 12,300– 30,740 3,415– 8,465 Thermal control becomes a dominant design consideration. Structure must either be designed to operate hot, or be protected by special silicate tiles or similar. Chemically reacting flow can also cause corrosion of the vehicle's skin, with free-atomic oxygen featuring in very high-speed flows. Hypersonic designs are often forced into blunt configurations because of the aerodynamic heating rising with a reduced radius of curvature. Re-entry speeds >25.0 >16,25 0 >30,740 >8,465 Ablative heat shield; small or no wings; blunt shape AERODYNAMICS
  • 26. 26 SOLO Different Regimes of Flow Mach Number – Flow Regimes AERODYNAMICS Return to Table of Content
  • 27. 27 SOLO - when the source moves at subsonic velocity V < a, it will stay inside the family of spherical sound waves. a V M M =      = − & 1 sin 1 µ Disturbances in a fluid propagate by molecular collision, at the sped of sound a, along a spherical surface centered at the disturbances source position. The source of disturbances moves with the velocity V. - when the source moves at supersonic velocity V > a, it will stay outside the family of spherical sound waves. These wave fronts form a disturbance envelope given by two lines tangent to the family of spherical sound waves. Those lines are called Mach waves, and form an angle μ with the disturbance source velocity: SHOCK & EXPANSION WAVES AERODYNAMICS
  • 28. 28 SOLO SHOCK & EXPANSION WAVES M < 1 M = 1 M > 1 Mach Waves AERODYNAMICS
  • 29. 29 SOLO When a supersonic flow encounters a boundary the following will happen: When a flow encounters a boundary it must satisfy the boundary conditions, meaning that the flow must be parallel to the surface at the boundary. - when the supersonic flow, in order to remain parallel to the boundary surface, must “turn into itself” a Oblique Shock will occur. After the shock wave the pressure, temperature and density will increase. The Mach number of the flow will decrease after the shock wave. SHOCK & EXPANSION WAVES - when the supersonic flow, in order to remain parallel to the boundary surface, must “turn away from itself” an Expansion wave will occur. In this case the pressure, temperature and density will decrease. The Mach number of the flow will increase after the expansion wave. Return to Table of Content AERODYNAMICS
  • 30. 30 SHOCK WAVES SOLO A shock wave occurs when a supersonic flow decelerates in response to a sharp increase in pressure (supersonic compression) or when a supersonic flow encounters a sudden, compressive change in direction (the presence of an obstacle). For the flow conditions where the gas is a continuum, the shock wave is a narrow region (on the order of several molecular mean free paths thick, ~ 6 x 10-6 cm) across which is an almost instantaneous change in the values of the flow parameters. Shock Wave Definition (from John J. Bertin/ Michael L. Smith, “Aerodynamics for Engineers”, Prentice Hall, 1979, pp.254-255) When the shock wave is normal to the streamlines it is called a Normal Shock Wave, otherwise it is an Oblique Shock Wave. The difference between a shock wave and a Mach wave is that: - A Mach wave represents a surface across which some derivative of the flow variables (such as the thermodynamic properties of the fluid and the flow velocity) may be discontinuous while the variables themselves are continuous. For this reason we call it a weak shock. - A shock wave represents a surface across which the thermodynamic properties and the flow velocity are essentially discontinuous. For this reason it is called a strong shock. AERODYNAMICS
  • 31. 31 Movement of Shocks with Increasing Mach Number <<<<<<< MMMMMMMM SOLO AERODYNAMICS Return to Table of Content
  • 32. 32 where ρ0 = air density U0 = true speed l 0= characteristic length μ0 = absolute (dynamic) viscosity υ0 = kinematic viscosity NumberReynolds:Re 0 00 0 000 0 0 0 υµ ρ ρ µ υ lUlU = == Osborne Reynolds (1842 –1912) It was observed by Reynolds in 1884 that a Fluid Flow changes from Laminar to Turbulent at approximately the same value of the dimensionless ratio (ρ V l/ μ) where l is the Characteristic Length for the object in the Flow. This ratio is called the Reynolds number, and is the governing parameter for Viscous Flow. Reynolds Number and Boundary Layer SOLO 1884AERODYNAMICS
  • 33. 33 Boundary Layer SOLO 1904AERODYNAMICS Ludwig Prandtl (1875 – 1953) In 1904 at the Third Mathematical Congress, held at Heidelberg, Germany, Ludwig Prandtl (29 years old) introduced the concept of Boundary Layer. He theorized that the fluid friction was the cause of the fluid adjacent to surface to stick to surface – no slip condition, zero local velocity, at the surface – and the frictional effects were experienced only in the boundary layer a thin region near the surface. Outside the boundary layer the flow may be considered as inviscid (frictionless) flow. In the Boundary Layer on can calculate the •Boundary Layer width •Dynamic friction coefficient μ •Friction Drag Coefficient CDf
  • 34. 34 The flow within the Boundary Layer can be of two types: •The first one is Laminar Flow, consists of layers of flow sliding one over other in a regular fashion without mixing. •The second one is called Turbulent Flow and consists of particles of flow that moves in a random and irregular fashion with no clear individual path, In specifying the velocity profile within a Boundary Layer, one must look at the mean velocity distribution measured over a long period of time. There is usually a transition region between this two types of Boundary-Layer Flow SOLO AERODYNAMICS
  • 35. 35 Normalized Velocity profiles within a Boundary-Layer, comparison between Laminar and Turbulent Flow. SOLO AERODYNAMICS Boundary-Layer
  • 36. 36 Flow Characteristics around a Cylindrical Body as a Function of Reynolds Number (Viscosity) AERODYNAMICS SOLO Return to Table of Content
  • 37. 37 SOLO Knudsen number (Kn) is a dimensionless number defined as the ratio of the molecular mean free path length to a representative physical length scale. This length scale could be, for example, the radius of the body in a fluid. The number is named after Danish physicist Martin Knudsen. Knudsen l Kn 0 0 : λ = Martin Knudsen (1871–1949). For a Boltzmann gas, the mean free path may be readily calculated as: • kB is the Boltzmann constant (1.3806504(24) × 10−23 J/K in SI units), [M1 L2 T−2 θ−1 ] p TkB 20 2 σπ λ = • T is the thermodynamic temperature [θ1 ] λ0 = mean free path [L1 ] Knudsen Number l0 = representative physical length scale [L1 ]. • σ is the particle hard shell diameter, [L1 ] • p is the total pressure, [M1 L−1 T−2 ]. See “Kinetic Theory of Gases” Presentation For particle dynamics in the atmosphere and assuming standard atmosphere pressure i.e. 25 °C and 1 atm, we have λ0 ≈ 8x10-8 m. AERODYNAMICS
  • 38. 38 SOLO Martin Knudsen (1871–1949). Knudsen Number (continue – 1) Relationship to Mach and Reynolds numbers Dynamic viscosity, Average molecule speed (from Maxwell–Boltzmann distribution), thus the mean free path, where • kB is the Boltzmann constant (1.3806504(24) × 10−23 J/K in SI units), [M1 L2 T−2 θ−1 ] • T is the thermodynamic temperature [θ1 ] • ĉ is the average molecular speed from the Maxwell–Boltzmann distribution, [L1 T−1 ] • μ is the dynamic viscosity, [M1 L−1 T−1 ] • m is the molecular mass, [M1 ] • ρ is the density, [M1 L−3 ]. 0 2 1 λρµ c= m Tk c B π 8 = Tk m B2 0 π ρ µ λ = AERODYNAMICS
  • 39. 39 SOLO Martin Knudsen (1871–1949). Knudsen Number (continue – 2) Relationship to Mach and Reynolds numbers (continue – 1) The dimensionless Reynolds number can be written: Dividing the Mach number by the Reynolds number, and by multiplying by yields the Knudsen number. The Mach, Reynolds and Knudsen numbers are therefore related by: Reynolds:Re 0 000 µ ρ lU = Tk m lmTklallU aUM BB γρ µ γρ µ ρ µ µρ 00 0 00 0 000 0 0000 00 // / Re ==== Kn Tk m lTk m l BB == 22 00 0 00 0 π ρ µπγ γρ µ 2Re πγM Kn = AERODYNAMICS
  • 40. 40 SOLO Knudsen Number (continue – 3) Relationship to Mach and Reynolds numbers (continue –2) According to the Knudsen Number the Gas Flow can be divided in three regions: 1.Free Molecular Flow (Kn >> 1): M/Re > 3 molecule-interface interaction negligible between incident and reflected particles 2.Transition (from molecular to continuum flow) regime: 3 > M/Re and M/(Re)1/2 > 0.01 (Re >> 1). Both intermolecular and molecule-surface collision are important. 3.Continuum Flow (Kn << 1): 0.01 > M/(Re)1/2 . Dominated by intermolecular collisions. 2Re πγM Kn = AERODYNAMICS
  • 41. SOLO Knudsen Number (continue – 4) Inviscid Limit Free Molecular LimitKnudsen Number Boltzman Equation Collisionless Boltzman Equation Discrete Particle model Euler Equation Navier-Stokes Equation Continuum model Conservation Equation do not form a closed set Validity of conventional mathematical models as a function of local Knudsen Number A higher Knudsen Number indicates larger mean free path λ, or the particular nature of the Fluid, meaning that Boltzmann Equations must be employed. Lower Knudsen Number means small free path, i.e. the flow acts as a continuum, and Navier-Stokes Equations must be used. Knudsen l Kn 0 0 : λ = AERODYNAMICS Return to Table of Content
  • 42. 42 The true airspeed (TAS; also KTAS, for knots true airspeed) of an aircraft is the speed of the aircraft relative to the air mass in which it is flying. True Airspeed TAS can be calculated as a function of Mach number and static air temperature: where a0 is the speed of sound at standard sea level (661.47 knots) M is Mach number, T is static air temperature in kelvin, T0 is the temperature at standard sea level (288.15ºK) 0 0 T T MaTAS = qc is impact pressure P is static pressure         −      += 11 5 7 2 0 0 P q T T aTAS c Flight Instruments
  • 44. SOLO 44 Flight Instruments Airspeed Indicators 2 2 1 vpp StatTotal ⋅+= ρ The airspeed directly given by the differential pressure is called Indicated Airspeed (IAS). This indication is subject to positioning errors of the pitot and static probes, airplane altitude and instrument systematic defects. The airspeed corrected for those errors is called Calibrated Airspeed (CAS). Depending on altitude, the critic airspeeds for maneuver, flap operation etc. change because the aerodynamic forces are function of air density. An equivalent airspeed VE (EAS) is defined as follows: 0ρ ρ VVE = V – True Airspeed ρ – Air Density ρ0 – Air Density at Sea Level
  • 47. 47 True Airspeed (TAS) and Calibrated Airspeed (CAS) Relationship with Varying Altitude and Temperature Flight Instruments
  • 48. 48 TAS and CAS Relationship with Varying Altitude and Temperature (continue) Flight Instruments
  • 49. 49 Mach Number vs TAS Variation with Altitude Flight Instruments
  • 52. 52 SOLO Aerodynamic Forces ( )[ ]∫∫ +−= ∞ WS A dstfnppF  11 ntonormalplanonVofprojectiont dstonormaln ˆˆ ˆ  − − ( ) airflowingthebyweatedsurfaceVehicleS SsurfacetheonmNstressforcefrictionf Ssurfacetheondifferencepressurepp W W W − − −−∞ )/( 2 Aerodynamic Forces acting on a Vehicle Surface SW. AERODYNAMICS
  • 53. 53 SOLO ( )       − − = L D F W A  VelocitytoNormalForceLiftL VelocitytooppositeForceDragD − − L D CSVL CSVD 2 2 2 1 2 1 ρ ρ = = ( ) ( ) tCoefficienLiftRMC tCoefficienDragRMC eL eD − − βα βα ,,, ,,, anglesideslipandattackofangle viscositydynamic lengthsticcharacteril soundofspeedHa numberReynoldslVR BodytoRelativeVelocityFlowV numberMachaVM e − − − − −= − −= βα µ µρ , )( / / AERODYNAMICS ( ) V W A nLVDF 11 −−=  Aerodynamic Forces Lift and Drag Forces
  • 54. 54 SOLO ( ) ( )∫∫ ∫∫ ⋅+⋅−= ⋅+⋅−= W W S VfVpL S fpD dsntCnnC S C dsVtCVnC S C 1ˆ1ˆ 1 1ˆ1ˆ 1 Wf Wp Ssurfacetheontcoefficienfriction V f C Ssurfacetheontcoefficienpressure V pp C −= − − = ∞ 2/ 2/ 2 2 ρ ρ ntonormalplanonVofprojectiont dstonormaln ˆˆ ˆ  − − Aerodynamic Forces CD – Drag Coefficient CL – Lift Coefficient AERODYNAMICS
  • 55. ( ) [ ] [ ]( )∫ ∫ ∞∞ = −−−= −=′ Edge Trailing Edge Leading sideuppersidelower cos Edge Trailing Edge Leading sideuppersidelower pp cospcosp dxpp dsL sdxd USLS θ θθ Divide left and right sides of the first equation by cV 2 2 1 ∞ρ ∫             − − − = ′ ∞ ∞ ∞ ∞ ∞ Edge Trailing Edge Leading upperlower c x d V pp V pp cV L 222 2 1 2 1 2 1 ρρρ We get: Relationship between Lift and Pressure on Airfoil Lower Surface Upper Surface ( )∫ −=− Edge Trailing Edge Leading sideuppersidelower sinpsinp dsD USLS θθ Lift – Aerodynamic component normal to V Drag – Aerodynamic component opposite to V SOLO AERODYNAMICS Aerodynamic Forces
  • 56. From the previous slide, ∫             − − − = ′ ∞ ∞ ∞ ∞ ∞ Edge Trailing Edge Leading upperlower c x d V pp V pp cV L 222 2 1 2 1 2 1 ρρρ The left side was previously defined as the sectional lift coefficient Cl. The pressure coefficient is defined as: 2 2 1 ∞ ∞− = V pp Cp ρ Thus, ( )∫ −= edge Trailing edge Leading upperplowerpl c x dCCC ,, Lower Surface Upper Surface Relationship between Lift and Pressure on Airfoil (continue – 1) SOLO AERODYNAMICS Aerodynamic Forces
  • 57. 57 SOLO Velocity Field Sum of the elementary Forces on the Body Lift as the Sum of the elementary Forces on the Body AERODYNAMICS Aerodynamic Forces
  • 58. 58 SOLO Lift and Drag Coefficients AERODYNAMICS Subsonic Speeds np α− Upper xd yd ∞U Upper xd yd ∞p∞p α   0,, 2 0 2 0 D TurbulentforMore LaminarforLess dragFriction fD TurbulentforLess LaminarforMore dragPressure pDD stall a L CCCC aC =+= <== = αααπα π Subsonic Incompressible Flow (ρ∞ = const.) about Wings of Finite Span (AR < ∞) Subsonic Incompressible Flow (ρ∞ = const.) about Wings of Infinite Span (AR → ∞)  ( )       −=−= ARe C C L i a L π απααπ 22 0 ARe C be SC V w L SbAR Li i ππ α / 2 2 = === α π α π ARe a a ARe CL 0 0 1 2 1 2 + = + = ARe C C L Di π 2 =    AR C CCCCC L D drag induced D drag friction fD drag pressure pDD i π 2 0,, +=++= e – span efficiency factor Aerodynamic Forces Return to Table of Content
  • 60. 60 AERODYNAMICS Drag Variation with Mach Number SOLO Aerodynamic Drag
  • 61. 61 Stengel, Aircraft Flight Dynamics, Princeton, MAE 331, Lecture 2 SOLO AERODYNAMICS Aerodynamic Drag
  • 62. 62N.X. Vinh, “Flight Mechanics of High-Performance Aircraft”, Cambridge University Press, 1993 α =0 – corresponds to CL=0. α0 – minimize CD. α1 – minimize the ratio CD/CL 1/2 . α2 – minimize the ratio CD/CL 2/3 . α* – minimize the ratio CD/CL. α3 – minimize the ratio CD/CL 3/2 . αmax – maximum CL. A Realistic Drag Polar SOLO AERODYNAMICS Aerodynamic Drag
  • 63. 63N.X. Vinh, “Flight Mechanics of High-Performance Aircraft”, Cambridge University Press, 1993 Parabolic Drag Polar of a typical High Subsonic Aircraft at different Mach Numbers SOLO AERODYNAMICS Aerodynamic Drag
  • 64. 64N.X. Vinh, “Flight Mechanics of High-Performance Aircraft”, Cambridge University Press, 1993 Variation of CD0 (M) for a supersonic aircraft Variation of aerodynamic characteristic for a typical subsonic transport aircraft Variation of aerodynamic characteristic for a typical supersonic fighter aircraft SOLO AERODYNAMICS Aerodynamic Drag
  • 65. 65 Movement of Shocks with Increasing Mach Number The Mach Number at witch M=1 appears on the Airfoil Upper Surface is called the Critical Mach Number for this Airfoil. The Critical Mach Number can be calculated as follows. Assuming an isentropic flow through the flow-field we have ( )1/ 2 2 2 1 1 2 1 1 − ∞ ∞             − + − + = γγ γ γ A A M M p p p∞, M∞ - Pressure and Mach Number upstream the Airfoil pA, MA- Pressure and Mach Number at a point A on the Airfoil Critical Mach Number The Pressure Coefficient Cp is computed using ( )             −             − + − + =      −= − ∞ ∞∞∞ 1 2 1 1 2 1 1 2 1 2 1/ 2 2 γγ γ γ γγ A A pA M M Mp p M C Definition of Critical Mach Number. Point A is the location of minimum pressure on the top surface of the Airfoil. SOLO AERODYNAMICS
  • 66. 66 Movement of Shocks with Increasing Mach Number Critical Mach Number This relation gives a unique relation between the upstream values of p∞, M∞ and the respective values pA, MA at a point A on the Airfoil. Assume that point A is the point of minimum pressure, therefore maximum velocity, on the Airfoil and that this maximum velocity corresponds to MA = 1. Then by definition M∞ = Mcr . ( )             −             − + − + =      −= − ∞ ∞∞∞ 1 2 1 1 2 1 1 2 1 2 1/ 2 2 γγ γ γ γγ A A pA M M Mp p M C ( )             −             − + − + = − 1 2 1 1 2 1 1 2 1/ 2 γγ γ γ γ cr cr p M M C cr 2 0 1 ∞− = M C C p p ( )             −             − + − + = − 1 2 1 1 2 1 1 2 1/ 2 γγ γ γ γ cr cr p M M C cr 2 0 1 ∞− = M C C p p To find the Mcr we need on other equation describing Cp at subsonic speeds. We can use the Prandtl-Glauert Correction or the Karman-Tsien Rule or Laiton’s Rule SOLO AERODYNAMICS
  • 67. 67 Movement of Shocks with Increasing Mach Number Critical Mach Number AirfoilThickAirfoilMediumAirfoilThin AirfoilThickAirfoilMediumAirfoilThin crcrcr ppp MMM CCC >> << 000 The point of minimum pressure, therefore maximum velocity, does not correspond to the point of maximum thickness of the Airfoil. This is because the point of minimum pressure is defined by the specific shape of the Airfoil and not by a local property. The Critical Mach Number is a function of the thickness of the Airfoil. For the thin Airfoil the Cp0 is smaller in magnitude and because the disturbance in the Flow is smaller. Because of this the Critical Mach Number of the thin Airfoil is greater SOLO AERODYNAMICS
  • 68. 68 Movement of Shocks with Increasing Mach Number Drag Divergence Mach Number The Drag at small Mach number, due to Profile Drag with Induced Drag =0 (αi = 0) is constant (points a, b, and c) until M∞ = Mcr (point c). As the velocity increase above Mcr (point d), a finite region of supersonic flow (Weak Shock boundary)appears on the Airfoil. The Mach Number in this bubble of supersonic flow is slightly above Mach 1, typically 1.02 to 1.05. If M∞ increases more, We encounter a point, e, at which is a sudden increase in Drag. The Value of M∞ at which the sudden increase in Drag starts is defined as the Drag-divergence Mach Number, Mdrag-divergence < 1. At this point Shock Waves appear on the Airfoil. The Shock Waves are dissipative phenomena extracting energy (Drag) from the kinetic energy of the Airfoil. In addition the sharp increase of the pressure across the Shock Wave create a strong adverse pressure gradient, causing the Flow to separate From the Airfoil Surface creating Drag increase. Beyond the Drag-divergence Mach Number, the Drag Coefficient becomes very large, increasing by a factor of 10 or more. As M∞ approaches unity (point f) the Flow on both the top and the SOLO AERODYNAMICS
  • 69. 69 Summary of Airfoil Drag The Drag of an Airfoil can be described as the sum of three contributions: iwpf DDDDD +++= where D – Total Drag of the Airfoil Df – Skin Friction Drag Dp – Pressure Drag due to Flow Separation Dw – Wave Drag (present only at Transonic and Supersonic Speeds; zero for Subsonic Speeds below the Drag-divergence Mach Number) Di – Induced Drag In terms of the Drag Coefficients, we can write: iDwDpDfDD CCCCC ,,,, +++= The Sum: pDfD CC ,, + Profile Drag Coefficient SOLO AERODYNAMICS Aerodynamic Drag
  • 71. 71 Relative Drag Force as a Function of Reynolds Number (Viscosity) AERODYNAMICS Drag CD0 due to Flow Separation SOLO Aerodynamic Drag
  • 72. 72 Relative Drag Force as a Function of Reynolds Number (Viscosity) AERODYNAMICS Drag due to Viscosity: 1.Skin Friction 2.Flow Separation (Drop in pressure behind body) ∫∫ ∫∫         ⋅+⋅ − −=         ⋅+⋅−= ∧∧ ∞ ∧∧ W W S S fpD ds w t V f w n V pp S ds w tC w nC S C xx xx 11 11 ˆ 2/ ˆ 2/ 1 ˆˆ 1 22 ρρ SOLO Aerodynamic Drag
  • 73. 73 Effect of Mach Number on the Drag Coefficient for a given Angle of Attack (AOA) and on the Lift Coefficient AERODYNAMICS Summary of Mach Effect on Drag and Lift Return to Table of Content
  • 74. 74 Wing Parameters Airfoil: The cross-sectional shape obtained by the intersection of the wing with the perpendicular plane 1. Wing Area, S, is the plan surface of the wing. 2. Wing Span, b, is measured tip to tip. 3. Wing average chord, c, is the geometric average. The product of the span and the average chord is the wing area (b x c = S). 4. Aspect Ratio, AR, is defined as: ( )∫− = 2/ 2/ b b dyycS ( ) b S dyyc b c b b == ∫− 2/ 2/ 1 S b AR 2 = AERODYNAMICSSOLO
  • 75. 75 Wing Parameters (Continue) 5. The root chord, , is the chord at the wing centerline, and the tip chord, is the chord at the tip. 6. Taper ratio, 7. Sweep Angle, is the angle between the line of 25 percent chord and the perpendicular to root chord. 8. Mean aerodynamic chord, rc Λ r t c c =λ tc λ ( )[ ]∫− = 2/ 2/ 21~ b b dyyc S c c~ AERODYNAMICSSOLO
  • 76. 76 Wing Parameters (Continue) AERODYNAMICS Illustration of Wing Geometry Planform, xy plane Dihedral (V form), yz plane Profile, twist xz plane Geometric Designation of Wings of various planform Swept-back Wing Delta Wing Elliptic Wing SOLO Return to Table of Content
  • 77. 77 Wing Design Parameters •Planform - Aspect Ratio - Sweep - Taper - Shape at Tip - Shape at Root •Chord Section - Airfoils - Twist •Movable Surfaces - Leading and Trailing-Edge Devices - Ailerons - Spoilers •Interfaces - Fuselage - Powerplants - Dihedral Angle AERODYNAMICSSOLO Return to Table of Content
  • 78. SOLO 78 Aircraft Flight Control Specific Stabilizer/Tail Configurations Tailplane Fuselage mounted Cruciform T-tail Flying tailplane The tailplane comprises the tail-mounted fixed horizontal stabilizer and movable elevator. Besides its planform, it is characterized by: • Number of tail planes - from 0 (tailless or canard) to 3 (Roe triplane) • Location of tailplane - mounted high, mid or low on the fuselage, fin or tail booms. • Fixed stabilizer and movable elevator surfaces, or a single combined stabilator or (all) flying tail.[1] (General Dynamics F-111) Some locations have been given special names: • Cruciform: mid-mounted on the fin (Hawker Sea Hawk, Sud Aviation Caravelle) • T-tail: high-mounted on the fin (Gloster Javelin, Boeing 727) Sud Aviation Caravelle Gloster Javelin
  • 79. SOLO 79 Aircraft Flight Control Specific Stabilizer/Tail Configurations Tailplane Some locations have been given special names: • V-tail: (sometimes called a Butterfly tail) • Twin tail: specific type of vertical stabilizer arrangement found on the empennage of some aircraft. • Twin-boom tail: has two longitudinal booms fixed to the main wing on either side of the center line. The V-tail of a Belgian Air Force Fouga Magister de Havilland Vampire T11, Twin-Boom Tail A twin-tailed B-25 Mitchell Return to Table of Content
  • 80. 80 SOLO Aircraft Propulsion Systems Classification of Engine Concepts , mostly used in Aviation
  • 81. 81 Run This http://lyle.smu.edu/propulsion/Pages/propeller.htm In small aircraft, the propeller is normally powered by a piston engine as shown above. In larger vessels like nuclear submarines, the propeller may be powered by a nuclear power plant. The basic operation of a propeller propulsion system is described in the interactive animation below. Use the arrows to step through descriptions of the different components. SOLO Propeller Propulsion
  • 82. 82 SOLO The Rotating Parts of Jet Engine Compressor Shaft Turbojet animation Turbine Air Breathing Jet Engines Run This
  • 83. 83 http://lyle.smu.edu/propulsion/Pages/variations.htm Run This A turbofan still has all the main components of a turbojet, but a fan and surrounding duct are added to the front as shown in the animation below. A fan is basically a propeller with a lot of blades specially designed to spin very quickly. Its function is essentially identical to a propeller, namely, the blades accelerate the oncoming air flow to create thrust. In a turbofan, however, the fan is driven by turbines in the attached turbojet engine, rather than by an internal combustion engine. Use the arrows in the interactive animation below to step through descriptions of the different components and obtain more detailed information about their operation. Turbofan
  • 84. 84 SOLO Animation of a 2-spool, high-bypass turbofan. A. Low pressure spool B. High pressure spool C. Stationary components 1. Nacelle 2. Fan 3. Low pressure compressor 4. High pressure compressor 5. Combustion chamber 6. High pressure turbine 7. Low pressure turbine 8. Core nozzle 9. Fan nozzle Turbofan Air Breathing Jet Engines Run This
  • 85. 85 SOLO Turboprop A turboprop engine is a type of turbine engine which drives an aircraft propeller using a reduction gear. The gas turbine is designed specifically for this application, with almost all of its output being used to drive the propeller. The engine's exhaust gases contain little energy compared to a jet engine and play only a minor role in the propulsion of the aircraft. The propeller is coupled to the turbine through a reduction gear that converts the high RPM, low torque output to low RPM, high torque. The propeller itself is normally a constant speed (variable pitch) type similar to that used with larger reciprocating aircraft engines. Turboprop engines are generally used on small subsonic aircraft, but some aircraft outfitted with turboprops have cruising speeds in excess of 500 kt (926 km/h, 575 mph). Large military and civil aircraft, such as the Lockheed L- 188 Electra and the Tupolev Tu-95, have also used turboprop power. The Airbus A400M is powered by four Europrop TP400 engines, which are the third most powerful turboprop engines ever produced, after the Kuznetsov NK-12 and Progress D-27. Air Breathing Jet Engines Run This
  • 86. 86http://lyle.smu.edu/propulsion/Pages/variations.htm Turboprop Engines: A turboprop engine is basically a propeller driven by a turbojet. Alternatively, it can be viewed as a very large bypass ratio turbofan. It is not exactly a turbofan because there is no shroud or "duct" surrounding the propeller and the propeller does not spin as fast as a fan. The basic components of a turboprop are illustrated in the interactive animation below. Use the arrows to step through descriptions of the different components. A turboprop engine enjoys the high efficiency of a propeller, owing to the large bypass ratio it provides. In fact, nearly all of the thrust generated by a turboprop is from the propeller. A turboprop also enjoys the high power-to-weight ratio of turbojet engines, resulting in a powerful compact propulsion system. Run This Return to Table of Content SOLO Air Breathing Jet Engines
  • 87. 87 SOLO Aircraft Propulsion System Aircraft propellers or airscrews[1] convert rotary motion from piston engines, turboprops or electric motors to provide propulsive force. They may be fixed or variable pitch. Aircraft Propellers Diesel Engine developed in the GAP program. Credit: NASA The simplest theory describing the operation of the propeller, assumes that the rotating propeller can be approximated by a thin Actuator Disk producing a uniform change in the velocity of the air stream passing across it. Actuator Disk (One-Dimensional Momentum) Theory
  • 88. 88 SOLO Propeller Aerodynamics Actuator Disk 2 11 2 22 2 1 2 1 VpVp ρρ +=+ 2 44 2 33 2 1 2 1 VpVp ρρ +=+ Bernoulli’s equations on each side of the Disk: Far from the Disk we have the same ambient pressure, hence: 41 pp = Therefore ( )2 1 2 423 2 1 VVpp −=− ρ Conservation of Mass through the Propeller Disk pp AVAVm 320 ρρ == 32 VV = Conservation of Energy on both sides of the Propeller Disk Actuator Disk (One-Dimensional Momentum) Theory
  • 89. 89 SOLO Propeller Aerodynamics Actuator Disk ( )2 1 2 423 2 1 VVpp −=− ρ The Thrust provided by the Propeller Disk is given by: ( ) ( )143140 VVAVVVmT p −=−= ρ where - Fluid mass flow [kg/sec] through DiskpAVm 30 ρ= ρ – Flow density [kg/m3 ] Ap – Disk area [m2 ] The Thrust also equals the Force on the Disk Surface due to Pressure jump: ( ) ( ) pp AVVAppT 2 1 2 423 2 1 −=−= ρ From the two expressions of Thrust we obtain ( ) ( )2 1 2 4143 2 1 VVVVV −=− ( )413 2 1 VVV += Conservation of Momentum Actuator Disk (One-Dimensional Momentum) Theory
  • 90. SOLO Propeller Aerodynamics Model of the Flow through Propeller according to the Actuator Disk Concept ( ) ( ) ppp pp VA mVVVAT v2v v20143 ⋅+= =−= ∞ρ ρ  We found Let compute vs as function of other parameters 0 2 vv 2 =−+ ∞ p pp A T V ρ 0 222 v 2 >+      +−= ∞∞ p p A TVV ρ This solution corresponds to a Propeller, where Energy is added to the Flow. Actuator Disk (One-Dimensional Momentum) Theory Ideal Power Consumed by the Rotor ( ) ( ) ( )         +      += ⋅=+= += −+= −= ∞∞ ∞ ∞ ∞∞ p p pp p A TVV T DiskatVelocityFlowThrustVT Vm VmVm InFlowEnergyOutFlowEnergyP ρ222 ___v vv2 2 1 v2 2 1 2 0 2 0 2 0  
  • 91. SOLO Propeller Aerodynamics The Efficiency of an Ideal Propeller This is called the idea1 efficiency of a propeller, which represents the upper limit of the efficiency that cannot be exceeded whatever the shape of the propeller. ( ) ( )aaVDVAT Va ppp p +=⋅+= ∞ = ∞ ∞ 1 2 vv2 22 /v: ρ π ρ ( ) aVV V VT VT PowerOutput PowerInput Va ppp P p + = + = + = +⋅ ⋅ == ∞= ∞∞ ∞ ∞ ∞ 1 1 /v1 1 vv /v: η ( ) p P P C JDV P aa 323 2 3 122 1 1 πρπη η ==+= − ∞ ( ) ( ) aaVDVTP p 232 1 2 v +=+= ∞∞ ρ π ( ) T P P C JDV T aa 2222 122 1 1 πρπη η ==+= − ∞ where Actuator Disk (One-Dimensional Momentum) Theory ( ) .: .: : 42 53 2/ 2 CoeffThrust Dn T C CoeffPower Dn P C RatioAdvance R V Dn V J T p n RD ρ ρ ππ = = Ω == ∞ Ω= = ∞
  • 92. SOLO Propeller Aerodynamics The Efficiency of an Ideal Propeller ( ) .: .: : 42 53 2/ 2 CoeffThrust Dn T C CoeffPower Dn P C RatioAdvance R V Dn V J T p n RD ρ ρ ππ = = Ω == ∞ Ω= = ∞ E.Torenbeek, H.Wittenberg, “Flight Physics – Essentials of Aeronauical Disciplines and Technology, with Historical Notes”, Springer, 2009 Typical Propeller Diagram Actuator Disk (One-Dimensional Momentum) Theory T P P C J 22 121 πη η = − p P P C J 33 121 πη η = − JV Dn P VT C C P p T η == ∞ ∞
  • 93. SOLO Propeller Aerodynamics The Efficiency of an Ideal Propeller E.Torenbeek, H.Wittenberg, “Flight Physics – Essentials of Aeronauical Disciplines and Technology, with Historical Notes”, Springer, 2009 Propeller Efficiency and Advance Ratio for various flight speeds. The Blade Pitch β is given. The change in Efficiency is due to the change in Angle-of-Attack (due to change in Velocity V∞ or Ω), Actuator Disk (Momentum) Theory J C C p T P =η ( ) .: .: : 42 53 2/ 2 CoeffThrust Dn T C CoeffPower Dn P C RatioAdvance R V Dn V J T p n RD ρ ρ ππ = = Ω == ∞ Ω= = ∞
  • 94. 94 AERODYNAMICS Asselin, M., “Introduction to Aircraft Performance”, AIAA Education Series, 1997 Actuator Disk (Momentum) Theory SOLO ( ) RatioAdvance R V Dn V J n RD Ω == ∞ Ω= = ∞ ππ2/ 2 : We can see that by varying the Propeller Pitch β we can operate at maximum efficiency ηmax.
  • 95. 95 SOLO Propeller Aerodynamics E. Torenbeek, H. Wittenberg, “Flight Physics, Essentials of Aeronautical Disciplines and Technology, with Historical Notes”, Springer, 2009, § 5.9, “Propeller Performance”, pg. 236 Propeller Blade Geometry Variation of Angles and Velocities along a Propeller Blade Propeller Blade have a variation of •Twist β •Chord c •Thickness t r V Ω =φtan From the Propeller Blade Geometry – advance angleϕ [rad] V – air velocity [m/sec], normal to rotation plane V = V∞ + v Ω – rotation rate [rad/sec] r – rotation radii [m] of blade section element φβα −= α – angle of attack [rad] of the section element (between section chord and resultant velocity) β – angle [rad] between section chord and rotation plane Blade Element Theory.
  • 96. 96 SOLO Propeller Aerodynamics ( ) ( )2222 v++Ω=+= ∞VrUUV pTres Given a Propeller Blade Element at a distance r from the Hub, the Resultant Velocity is given by We have ( ) ( ) ( ) ( ) ( ) ( )αραρ αραρ DDres LLres CcrVCcVDd CcrVCcVLd 22222 22222 2 1 2 1 2 1 2 1 Ω+== Ω+== ∞ ∞ Section Lift, normal to Vres Section Drag, opposite to Vres Simplified view of the forces on a Propeller Blade Element c – chord of Propeller Blade Element CL – Lift Coefficient of Propeller Blade Element CD – Drag Coefficient of Propeller Blade Element The resultant forces Normal (d T) and in the Disk Plane (d Fx) are             − =      Dd Ld Fd Td x φφ φφ cossin sincos Blade Element Theory. The Aerodynamic Moment and Power of the Propeller Blade Element are QdFdrFdUPd FdrQd xxT x Ω=⋅Ω== ⋅=
  • 97. 97 SOLO Propeller Aerodynamics The net force acting on the blades are the summation of the forces acting upon the individual elements. We must multiply by the number of blades B of the Rotor. We have Blade Element Theory. ( ) ( ) ( ) ( ) ( )( ) ( ) ( ) ( ) ( ) ( )( ) ( ) ( ) ( ) ( ) ( )( )∫∫ ∫∫ ∫∫ = = ∞ = = = = ∞ = = = = ∞ = = +Ω+Ω=⋅Ω= +Ω+=⋅= −Ω+== Rr r DL Rr r x Rr r DL Rr r x Rr r DL Rr r rdrCrCrrVBcFdrBP rdrCrCrrVBcFdrBQ rdrCrCrVBcTdBT 0 222 0 0 222 0 0 222 0 cossin 2 1 cossin 2 1 sincos 2 1 φαφαρ φαφαρ φαφαρ ( ) r V r Ω + = ∞ v tanφ ( ) ( ) ( )rrr φβα −= The Thrust, Aerodynamic Moment and Power of the Propeller (B blades) are The β (r) must be twisted to have the function α (r) optimal at each section r for given V∞ and Ω. If V∞ changes by rotating the Propeller around it’s axis (Pitch) we change β (r) to optimize again α (r).
  • 98. 98 SOLO Propeller Aerodynamics Blade Element Theory. 42 22 242 53 32 253 2 2 4 : 4 : : D T Dn T C R P Dn P C RatioAdvance R V Dn V J n RD T n RD p n RD Ω == Ω == Ω == Ω = = Ω = = ∞ Ω = = ∞ ρ π ρ ρ π ρ π π π π  ( ) ( ) ( ) ( )( )∫ = = ∞       −      + Ω = Ω = Rr r DLT R r drCrC R r R V R cB R T C 0 2 2 2 22 22 42 2 sincos 84 φαφαπ π π π ρ π σ  ( ) ( ) ( ) ( )( )∫ = = ∞       +      + Ω = Ω = Rr r DLP R r drCrC R r R rV R Bc R P C 0 2 2 2 2 22 53 3 cossin 84 φαφαππ π π π ρ π σ We have or Let use the definitions: ( ) Solidity R cB R RcB DiskSurface ElementsBladeSurface == == π π σ 2 : ( ) ( ) ( ) ( ) ( )( )∫ = = = −+= 1 0 222 / sincos 8 x x DL Rrx T xdxCxCxJC φαφαπσ π Thrust Coefficient ( ) ( ) ( ) ( ) ( )( )∫ = = = ++= 1 0 222 / cossin 8 x x DL Rrx P xdxCxCxxJC φαφαππσ π Power Coefficient
  • 99. 99 SOLO Propeller Aerodynamics Blade Element Theory. 42 22 242 53 32 253 2 2 4 : 4 : : D T Dn T C R P Dn P C RatioAdvance R V Dn V J n RD T n RD p n RD Ω == Ω == Ω == Ω = = Ω = = ∞ Ω = = ∞ ρ π ρ ρ π ρ π π π π Characteristic Curves of a Propeller Propeller Efficiency. J C C Dn V C C CDn VCDn P VT P T P T P T ==== ∞∞∞ 53 42 ρ ρ η
  • 100. 100 SOLO Propeller Aerodynamics Fuel Consumption For VTPP ppA ⋅⋅=⋅= ηηThe Available Power is ηp – propulsive efficiency For a given throttle setting, a regular piston engine, that aspire atmospheric air, produces power that is almost constant with velocity but decreases as the altitude increases (air density decreases). VTP ⋅= Propeller Propulsion The fuel mass flow is proportional to engine power P pApp PcPcWf η/==−=  cp – power specific fuel consumption VPT /= The engine power is    =      = restratosphe etropospher x P P x 1 75.0 00 ρ ρ
  • 101. 101 H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35 Asselin, M., “Introduction to Aircraft Aerodynamics”, AIAA Education Series, 1997 Return to Table of Content
  • 102. 102 Most jet engines are Turbofans and some are Turbojets which use gas turbines to give high pressure ratios and are able to get high efficiency, but a few use simple ram effect or pulse combustion to give compression. Most commercial aircraft possess turbofans, these have an enlarged air compressor which permit them to generate most of their thrust from air which bypasses the combustion chamber. AIR BREATHING JET ENGINESSOLO Operation of Aircraft Turbojet EngineAircraft Turbo Engines The turboprop engine : Turboprop engine derives its propulsion by the conversion of the majority of gas stream energy into mechanical power to drive the compressor , accessories , and the propeller load. The shaft on which the turbine is mounted drives the propeller through the propeller reduction gear system . Approximately 90% of thrust comes from propeller and about only 10% comes from exhaust gas. The turbofan engine : Turbofan engine has a duct enclosed fan mounted at the front of the engine and driven either mechanically at the same speed as the compressor , or by an independent turbine located to the rear of the compressor drive turbine . The fan air can exit separately from the primary engine air , or it can be ducted back to mix with the primary's air at the rear . Approximately more than 75% of thrust comes from fan and less than 25% comes from exhaust gas.
  • 103. 103 Propulsion Force = Thrust SOLO The net Thrust ( T ) of a Turbojet is given by where: ṁ air  = the mass rate of air flow through the engine ṁ fuel  = the mass rate of fuel flow entering the engine Ue = the velocity of the jet (the exhaust plume) U0 = the velocity of the air intake = the true airspeed of the aircraft (ṁ air  + ṁ fuel  )Ue = the nozzle gross thrust (FG) ṁ air  U0 = the ram drag of the intake air Aircraft Propulsion System ( )[ ] ( ) airfueleeeair mmfAppUUfmTHRUST  /:1 00 =−+−+==T Jet Engines Thrust Force Introduction to Air Breathing Jet Engines 00 ,Up 0A eA ee Up ,
  • 104. 104 Turbojet SOLO Thrust Computation for Air Breathing Engines ( ) ( )         DRAGFRICTION A WA DRAGPRESURE A WA THRUST eeeeex WW AdAdppAppAUAUF ∫∫∫∫ −−−−+−= θτθρρ cossin000 2 00 2 00000 & mAUmmAU feee  =+= ρρUsing C.M. ( ) ( ) 00000 2 00 2 UmUmmAppAUAUTHRUST efeeeee  −+=−+−= ρρ or we obtain ( )[ ] ( ) 0000 /:1 mmfAppUUfmTHRUST feee  =−+−+==T and ( )      DRAGFRICTION A WA DRAGPRESURE A WA WW AdAdppDRAGD ∫∫∫∫ +−== θτθ cossin0 00 ,Up 0A eA ee Up , Air Breathing Jet Engines Pressure force Friction force Wetted Surface Aerodynamic Forces on Wetted Surfaces
  • 105. 105 Turbojet SOLO Thrust Computation for Air Breathing Engines (continue – 1) since and 00 ,Up 0A eA ee Up , ( ) 0 00000 00 00 /:111 mmf A A p p U U f Ap Um Ap f eee   =      −+      −+= T 2 0 2 0 00 002 0 0 2 00 0 2 00 00 2 000 00 00 MM TR TR M p a p U Ap UA Ap Um γ ρ γρρρρ =====  ( ) 0 000 2 0 00 /:111 mmf A A p p U U fM Ap f eee =      −+      −+= γ T 000 2 00 0 00 000000 MApaM TR Ap aUAam γρ === ( ) 0 0000 0 00000 /:1 1 11 1 mmf A A p p MU U fM ApMam f eee   =      −      +      −+=      = γγ TT Air Breathing Jet Engines
  • 106. 106 Turbojet SOLO Thrust Computation for Air Breathing Engines (continue – 2) 00 ,Up 0A eA ee Up , 000 0 00 00 11 : ApMg a famg a m m gmWeightFuelBurned ForceThrust I ff sp TTT       ==== γ   Specific Impulse 0000 11 ApMfa gIsp T       = γ Specific Fuel Consumption (SFC) spIg f ThrustofPound HourperBurnedFuelofPound S 1 : ==== 0 f mT/T m   Air Breathing Jet Engines
  • 107. 107 Air Breathing Jet Engines PRESSURE Compressor Pressure Rise Turbine Pressure Drop (Turbojet) Heat Added in Combustion Chambers by burning mfuel mass TOTAL TEMPERATURE mfuel_1 mfuel_2 mfuel_3 mfuel_1 >mfuel_2>mfuel_3 Pressure corresponding to mfuel_1 and Thrust1 Pressure corresponding to mfuel_2 and Thrust2 Pressure corresponding to mfuel_3 and Thrust3A B1 B2 B3 C1 D1 C2 D2 C3 D3 Thrust1 >Thrust2>Thrust3 E
  • 108. 108 Air Breathing Jet Engines PRESSURE Compressor Pressure Rise Turbine Pressure Drop (Turbojet) Heat Added in Combustion Chambers by burning mfuel mass TOTAL TEMPERATURE Pressure corresponding to mfuel and ThrustA B C D1 F E Additional Turbine Pressure Drop in Turboprop
  • 109. 109 ( )[ ] ( ) 0000 /:1 mmfAppUUfm feee  =−+−+=T 00 ,Up 0A eA ee Up , Aircraft Propulsion SystemSOLO 0000 UAm ρ= The change in altitude (air density) will affect the thrust as follows As U0 increases Ue doesn’t change (at the first order), since the value of Ue depends more of the internal compression and combustion processes inside the engine than on the U0. Therefore Ue – U0 will decrease. Since increase in U0 increases ṁ0 , the Thrust T will remain, at first order, constant. 0UwithconstantelyapproximatisT ..LSS.L. ρ ρ = T T Sensitivity of Thrust and Specific Fuel Consumption with Velocity and Altitude for a Jet Engine J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999 The Specific Fuel Consumption increases with Mach at subsonic velocity (see Figure next slide) 11 00 <+= MMkTSFC The Specific Fuel Consumption is constant with altitude at subsonic velocity (see Figure next slide) altitudewithconstantisTSFC
  • 110. 110 Typical results for the variation of Thrust and Thrust Specific Fuel Consumption with Subsonic Mach number for a Turbojet J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999 Aircraft Propulsion SystemSOLO Sensitivity of Thrust and Specific Fuel Consumption with Velocity and Altitude for a Jet Engine
  • 111. 111 Typical results for the variation of Thrust and Thrust Specific Fuel Consumption with Supersonic Mach number for a Turbojet J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999 Aircraft Propulsion SystemSOLO Sensitivity of Thrust and Specific Fuel Consumption with Velocity and Altitude for a Jet Engine Supersonic Conditions 1 2 2 1 1 −       − += γ γ γ M p p static total Ptotal is the pressure entering the Compressor from the Diffuser, that further increases the pressure and therefore the exit Velocity Ue and the Thrust. From the Figure we obtain that for the specific aircraft the Supersonic Thrust is given by ( )118.11 0 1 −+= = M MT T ..LSS.L. ρ ρ = T T The Specific Fuel Consumption is constant with Mach at supersonic velocity (see Figure) The Specific Fuel Consumption is constant with altitude at supersonic velocity (see Figure) altitudewithconstantisTSFC 10 >MMachwithconstantisTSFC
  • 112. 112 H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35 Turbojet Performance Aircraft Propulsion SystemSOLO Return to Table of Content
  • 113. 113 SOLO Thrust Augmentation – Reheat in an Afterburner Aircraft Propulsion System To achieve Take-Off from a Short Runway a Fighter Aircraft needs additional Thrust. This is also necessary in Dogfight Combat to increase Aircraft Maneuverability. A very effective and widely used method to increase Thrust is by Reheat or Afterburning which enables Thrust to be increased by 50 percent. The technology of Reheat is possible because the hot gas after passing the Turbine, still contains enough oxygen to allow a Second Combustion given additional Fuel is Injected. (Only part of the air is discharged by the Compressor is used for Combustion, the greater part is used for Cooling). The Afterburner is a Tube-like structure attached to the Gas Generator immediately behind the Turbine. The forward part is designed as a Diffuser (increasing cross- section) which decrease flow velocity from Mach 0.5 to 0.2. It consists of the following four components: - Flame Tube - Fuel Injection System - Flame Holder Assembly (prevent Flame for being carried away) - Variable Geometry Exhaust Nozzle Afterburner
  • 114. 114 SOLO Ideal Turbojet Engine with Afterburner Pressure-Volume Diagram Temperature-Entropy Diagram Ideal Turbojet with Afterburner eA ee Up , 00 ,Up 0A Air Breathing Jet Engines Typical afterburning jet pipe equipment. Afterburner Return to Table of Content
  • 115. 115 Thrust Reversal Operation (Used during Landing) Aircraft Propulsion SystemSOLO Return to Table of Content
  • 116. 116 Typical results for the variation of Thrust and Thrust Specific Fuel Consumption with Subsonic Mach number for Turbojet J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999 Aircraft Propulsion SystemSOLO Altitude variation T/T0 = ρ/ρ0 Velocity variation 1.Subsonic: T is constantwithV’ 2. Supersonic: T/Tm=1=1+1.18 (M’-1) Velocity variation 1. Subsonic: TSFC= 1.0+k M’ 2. Supersonic: TSFCis constant’ Altitude variation SFCis constantwith Altitude Specificfuel Consumption Power PA =T V’ Turbojet Engine Aircraft Propulsion Summary
  • 117. 117 Altitude variation T/T0=(ρ/ρ0 )m Velocity variation 1High bypassratio:T/TV=0=AM’ -n 2.Lowbypassratio:TfirstincreaseswithM’ then decreasesathigh supersonicM’ Velocity variation 1.High Bypassct =B(1.0+kM’ ) 2.LowBypass:ct graduatelyincreaseswithvelocity Altitude variation ct isconstantwith Altitude Specificfuel Consumption Power PA =TV’ Turbofan Engine J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999, pg.186 Aircraft Propulsion Summary Aircraft Propulsion SystemSOLO
  • 118. 118 Velocityvariation PA isconstantwithM’ Altitude variation PA/PA,0 =(ρ/ρ0)m Velocityvariation CA isconstantwithV’ Altitude variation CA isconstantwithAltitude Specificfuel Consumption Power PA=(TP+Tj)V’ PA=hpr PS+Tj V’ PA=hpr Pes Turboprop Engine J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999, pg.186 Aircraft Propulsion Summary Block Diagram Aircraft Propulsion SystemSOLO Aircraft Propulsion Summary
  • 119. 119 Altitude variation 1. P/P0 = ρ/ρ0 2. (slightly more accurate) P/P0 =1.132 ρ/ρ0-0.132 Velocity variation Shaft Power P constant with V’ Velocity variation SFC is constant with V’ Altitude variation SFC is constant with Altitude Altitude variation T/T0 = ρ/ρ0 Velocity variation 1.Subsonic: T is constant with V’ 2. Supersonic: T/Tm=1=1+1.18 (M’-1) Velocity variation 1. Subsonic: TSFC = 1.0+k M’ 2. Supersonic: TSFC is constant’ Altitude variation SFC is constant with Altitude Altitude variation T/T0 =( ρ/ρ0 )m Velocity variation 1High bypass ratio: T/TV=0=A M’ -n 2. Low bypass ratio: T first increases with M’ then decreases at high supersonic M’ Velocity variation 1. High Bypass ct = B (1.0+k M’ ) 2.Low Bypass: ct graduately increases with velocity Altitude variation c t is constant with Altitude Velocity variation PA is constant with M’ Altitude variation PA/PA,0 = (ρ/ρ0)m Velocity variation CA is constant with V’ Altitude variation CA is constant with Altitude Specific fuel Consumption Specific fuel Consumption Specific fuel Consumption Specific fuel Consumption Power PA =T V’ Power PA =T V’ Power PA = hpr P hpr = f (J) J = V’/(N D) Power PA =(TP+Tj) V’ PA = hpr PS+Tj V’ PA = hpr Pes Reciprocating Engine/ Propeller Combination Turbojet Engine Turbofan Engine Turboprop Engine Propulsion Systems J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999, pg.186 Aircraft Propulsion Summary Block Diagram Aircraft Propulsion SystemSOLO
  • 120. 120 Air Breathing Jet Engines 0m T Aircraft Propulsion Summary SOLO
  • 121. 121 Air Breathing Jet Engines Aircraft Propulsion Summary SOLO
  • 122. 122 Air Breathing Jet Engines Aircraft Propulsion Summary SOLO
  • 123. 123 SOLO Propulsive Efficiency Characteristics of Turboprop, Turbofan and Turbojet Engines Air Breathing Jet Engines Return to Table of Content Propulsive Efficiency Summary
  • 124. 124Stengel, MAE331, Lecture 6 Thrust of a Propeller- Driven Aircraft • With constant r.p.m., variable-pitch propeller where ηp - propeller efficiency ηI - ideal propulsive efficiency ηnet-max ≈ 0.85 – 0.9 Efficiency decrease with airspeed Engine power decreases with altitude - Proportional with air density w/o supercharger V P V P T engine net engine Ip ηηη == Variation of Thrust and Power of a Propeller-Driven Aircraft with True Airspeed Aircraft Propulsion Summary SOLO Aircraft Propulsion System
  • 125. 125 Thrust as a function of airspeed for different Propulsion Systems Aircraft Propulsion Summary SOLO Aircraft Propulsion System
  • 126. 126 Stengel, MAE331, Lecture 6 Thrust of a Turbojet Engine ( )         −      +−      −      − = 11 11 2/1 00 0 c t c t t VmT τθ θ τ θ θ θ θ fuelair mmm  += ( ) heatsspecificofratio p p ambient stag =      = − γθ γγ , /1 0       = etemperaturambientfreestream etemperaturinletturbine 0θ       = etemperaturinletcompressor etemperaturoutletcompressor cτ • Little change in thrust with airspeed below Mcrit • Decrease with increasing altitude where Variation of Thrust and Power of a Turbojet Engine with True Airspeed SOLO Aircraft Propulsion System
  • 127. 127 Stengel, MAE331, Lecture 6 John D. Anderson, Jr., “Introduction to Flight”, McGraw Hill, 1978, § 6.4, pg. 217 B. N. Pamadi, “Performance, Stability, Dynamics and Control of Aircraft”, AIAA SOLO Aircraft Propulsion System
  • 128. 128 Power and Thrust • Propeller • Turbojet • Throttle Effect airspeedoftindependenSVCVTPPower T ≈=•== 3 2 1 ρ airspeedoftindependenSVCTThrust T ≈== 2 2 1 ρ 10 2 1 2 max max ≤≤== TSVTCTTT T δρδδ Specific Fuel Consumption, SFC = cP or cT • Propeller aircraft • Jet aircraft [ ] [ ]       → → = −= −= lbf slb or kN skg c HP slb or kW skg c weightfuelw where thrusttoalproportionTcw powertoalproportionPcw T P f Tf Pf // // SOLO Aircraft Propulsion System Return to Table of Content
  • 129. 129Dr. Carlo Kopp, Air Power Australia, Sukhoi Su-34 Fullback, Russia's New Heavy Strike Fighter Comparison of Fighter Aircraft Propulsion Systems SOLO
  • 130. 130 Comparison of Fighter Aircraft Propulsion Systems SOLO
  • 131. 131 Comparison of Fighter Aircraft Propulsion Systems SOLO
  • 132. 132M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring” Comparison of Fighter Aircraft Propulsion Systems SOLO
  • 133. 133M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring” Comparison of Fighter Aircraft Propulsion Systems SOLO
  • 134. 134M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring” Comparison of Fighter Aircraft Propulsion Systems SOLO
  • 135. 135M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring” Comparison of Fighter Aircraft Propulsion Systems SOLO
  • 136. 136M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring” Return to Table of Content Comparison of Fighter Aircraft Propulsion Systems SOLO
  • 137. 137 SOLO Aircraft Propulsion System VTOL - Vertical Take off and Landing capability The advantages of vertical take off and landing VTOL are quite obvious. Conventional aircraft have to operate from a small number of airports with long runways. VTOL aircraft can take off and land vertically from much smaller areas. STOL - Short takeoff and landing These aircraft using thrust vectoring to decrease the distance needed for takeoff and landing but don’t have enough thrust vectoring capability to perform a vertical take off or landing. VSTOL - An aircraft that can perform either vertical or short takeoff and landings STOVL - Short takeoff and vertical land. An aircraft that has insufficient lift for vertical flight at takeoff weight but can land vertically at landing weight. TVC - Thrust Vector Control Vertical Take off and Landing - VTOL
  • 138. 138 SOLO Vertical Take off and Landing - VTOL
  • 139. 139M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring”
  • 140. 140 Lockheed_Martin_F-35_Lightning_II STOVL The Unique F-35 Fighter Plane, Movie USP 3” part F35 Joint Strike Fighter ENG, Movie SOLO Aircraft Propulsion System Thrust vectoring nozzle of the F135-PW-600 STOVL variant Return to Table of Content
  • 141. 141 Aircraft Propulsion System SOLO Engine Control System Engine Control System Basic Inputs and Outputs Engine Control System Input Signals: • Throttle Position (Pilot Control) • Air Data (from Air Data Computer) Airspeed and Altitude • Total Temperature (at the Engine Face) • Engine Rotation Speed • Engine Temperature • Nozzle Position • Fuel Flow • Internal Pressure Ratio at different Stages of the Engine Output Signals • Fuel Flow Control • Air Flow Control
  • 142. 142 Aircraft Propulsion SystemSOLO The Fighter Aircraft Propulsion Systems Consists of: - One or Two Jet Engines - The Fuel Tanks (Internal and External) and Pipes. - Engines Control Systems * Throttles * Engine Control Displays Engine Control Systems – Basic Inputs and Outputs
  • 143. 143 Aircraft Propulsion SystemSOLO A Simple Engine Control Systems : Pilot in the Loop A Simple Limited Authority Engine Control Systems TGT – Turbine Gas Temperature NH – Speed of Rotation of Engine Shaft Tt - Total Temperature FCU – Fuel Control Unit Engine Control System
  • 144. 144 Aircraft Propulsion SystemSOLO A Simple Engine Control Systems : Pilot in the Loop A Simple Limited Authority Engine Control Systems Engine Control Systems : with NH and TGT exceedance warning Full Authority Engine Control Systems With Electrical Throttle Signaling : Engine Control System Return to Table of Content
  • 146. 146 center stickailerons elevators rudder Aircraft Flight Control Generally, the primary cockpit flight controls are arranged as follows: a control yoke (also known as a control column), center stick or side-stick (the latter two also colloquially known as a control or B joystick), governs the aircraft's roll and pitch by moving the A ailerons (or activating wing warping on some very early aircraft designs) when turned or deflected left and right, and moves the C elevators when moved backwards or forwards rudder pedals, or the earlier, pre-1919 "rudder bar", to control yaw, which move the D rudder; left foot forward will move the rudder left for instance. throttle controls to control engine speed or thrust for powered aircraft. SOLO
  • 148. 148 The effect of left rudder pressure Four common types of flaps Leading edge high lift devices The stabilator is a one-piece horizontal tail surface that pivots up and down about a central hinge point. Aircraft Flight ControlSOLO
  • 150. SOLO 150 Aerodynamics of Flight Aircraft Flight Control Return to Table of Content
  • 151. SOLO -Aerodynamic Forces ( ) ( ) ( ) ( ) ( ) BTBT VTrTT nMqNxMqA nMqLVMqDMqA 1,,1,, 1,,1,,,, αα ααα +−= +−=  ( )MqD T ,,α -Drag Force ( )MqN T ,,α -Normal Force Mq T ,,α -Dynamic Pressure, Total Angle of Attack, Mach Number ( ) ( ) ( ) ( )MCSVhD MCSVhL TD q r TL q r , 2 1 , 2 1 2 2 αρ αρ   = = Aerodynamic Forces (Vectorial) ( )MqA T ,,α -Axial Drag Force ( )MqL T ,,α -Lift Force ( ) ( ) ( ) ( )MCSVhA MCSVhN TA q r TN q r , 2 1 , 2 1 2 2 αρ αρ   = =     += −= TBTBV TBTBr nxn nxV αα αα cos1sin11 sin1cos11     −= += TVTrB TVTrB nVn nVx αα αα cos1sin11 sin1cos11 Aircraft Equations of Motion
  • 152. SOLO -Aerodynamic Forces ( ) ( ) ( ) ( ) ( ) BTBT VTrTT nMqNxMqA nMqLVMqDMqA 1,,1,, 1,,1,,,, αα ααα +−= +−=  are coplanar( )01,11,1 ≠TVBrB nnandVx α ( ) ( ) T rBT rB rBrB rB rB BB Vx Vx VxVx Vx Vx xn α α sin 11cos 11 1111 11 11 11 − = × −• = × × ×= ( ) ( ) T rTB rB rrBB rB rB rV Vx Vx VVxx Vx Vx Vn α α sin 1cos1 11 1111 11 11 11 − = × •− = × × ×=     += −= TBTBV TBTBr nxn nxV αα αα cos1sin11 sin1cos11     +−= += TVTrB TVTrB nVn nVx αα αα cos1sin11 sin1cos11 Aerodynamic Forces (Vectorial) Aircraft Equations of Motion
  • 153. SOLO -Aerodynamic Forces ( ) ( ) ( ) ( ) ( ) BTBT VTrTT nMqNxMqA nMqLVMqDMqA 1,,1,, 1,,1,,,, αα ααα +−= +−=  ( ) ( ) ( ) ( )MCSVhD MCSVhL TD q r TL q r , 2 1 , 2 1 2 2 αρ αρ   = = ( ) ( ) ( ) ( ) ( )MCSVhA MCSVhN TA q r MC TN q r TN , 2 1 , 2 1 2 2 αρ αρ αα    = = ( ) ( ) ( ) ( )[ ] ( ) ( ) ( )[ ] ( ) ( ) ( )[ ] MAXT VTTNTTAr rTTNTTAr VTLrTDT nMCMCSVh VMCMCSVh nMCVMCSVhMqA αα ααααρ ααααρ ααρα ≤ ++ +−= +−= 1cos,sin, 2 1 1sin,cos, 2 1 1,1, 2 1 ,, 2 2 2  Aerodynamic Forces (Vectorial) Aircraft Equations of Motion
  • 154. 154 SOLO Drag ,Lift Coefficients as functions of Angle of Attack Drag Polar Drag Polar Aircraft Equations of Motion
  • 155. 02/28/15 155 SOLO By changing αT from 0 to αMAX, and rotating around by σ (from 0 to σMAX) we obtain a Surface of Revolution Σq (CA,CN) which defines the Achievable Aerodynamic Forces for the given dynamic pressure q. rV1 ( ) ( ) VzVyV MAXT soundr r windr nnn hVVM VShq vRVV 1sin1cos1 / 2 1 2 σσ αα ρ += ≤ = = −×Ω−=  ( ) ( ) ( ) ( ) ( ) VTLrTD VTrTT nMCqVMCq nMqLVMqDMqA 1,1, 1,,1,,,, αα ααα +−= +−=  ( ) ( ) T rTB rB rrBB rB rB rV Vx Vx VVxx Vx Vx Vn α α sin 1cos1 11 1111 11 11 11 − = × ⋅− = × × ×= ( )σα,A  V  α MAXα ( )DL CC ,Σ σ MAXσ ( ) ( )αα 2 0 LDD CkCC += D σcosL σsinL σ MAXσ L L Aerodynamic Forces (Vectorial) Aircraft Equations of Motion
  • 156. 02/28/15 156 SOLO We can see that for αT = 0 ( ) ( ) ( ) ( ) ( )   MA Ar MD DT TT MCqVMCqMqA ,0 0 ,0 0 1,0, == −=−== αα α ( ) ( )Rg m T V m MCq V r D    ++−= 10 and since for αT = 0 the aerodynamic forces will decrease the velocity. We can see that for αT ≠ 0, the deceleration due to aerodynamics will only increase. ( ) ( ) ( )[ ] ( ) ( )MqDMCqMCMCqMqD TATTNTAT ,0,sincos,0, ==>+=≠ ααααα α The most Energy Effective Trajectory is one with αT = 0. ( ) ( ) VzVyV MAXT soundr r windr nnn hVVM VShq vRVV 1sin1cos1 / 2 1 2 σσ αα ρ += ≤ = = −×Ω−=  ( ) ( ) T rTB rB rrBB rB rB rV Vx Vx VVxx Vx Vx Vn α α sin 1cos1 11 1111 11 11 11 − = × ⋅− = × × ×= ( ) ( ) ( ) ( ) ( ) VTLrTD VTrTT nMCqVMCq nMqLVMqDMqA 1,1, 1,,1,,,, αα ααα +−= +−=  Aerodynamic Forces (Vectorial) Aircraft Equations of Motion Return to Table of Content
  • 157. 02/28/15 157 SOLO Specific Energy ( ) ( )RgTA m V  ++= 1 ( ) ( ) ( ) VTrTT nMqLVMqDMqA 1,,1,,,, ααα +−=  By Integrating this Equation we obtain: ( ) ( )∫∫ +⋅=         ⋅− ⋅ =− t t t t dtTAV gm dt g Rg V g VV EE 00 000 0 1  ( ) ( ) ( )∫∫∫∫ ∫ +⋅=⋅ − − − =⋅− ⋅ =         ⋅− ⋅ =− t t R R dRR E R R t t V V dtTAV gm RdR Rgg VV Rd g Rg g VdV dt g Rg V g VV EE 0000 0 0 3 00 2 0 2 0000 0 11 2          µ Define Specific Energy Derivative: ( ) ( )TAV mg Rg V g VV E   +⋅=⋅− ⋅ = 1 : 00 2 0 0 : R g Eµ = ( )∫ +⋅=        −−      −=      −− − =− t t EEE dtTAV gmRgg V Rgg V RRgg VV EE 0 0000 2 0 00 2 000 2 0 2 0 1 22 11 2 µµµ Aircraft Equations of Motion
  • 158. 02/28/15 158 SOLO Specific Energy (continue – 1) ( ) ( )∫∫ +⋅=         ⋅− ⋅ =− t t t t dtTAV gm dt g Rg V g VV EE 00 000 0 1  0 2 0 2 00 20 0 g VV g VdV dt g VV t t V V − = ⋅ = ⋅ ∫ ∫    ( ) ( ) ( ) ( ) 0 3 0 3 2 0 02 0 2 2 2 0 3 2 0 00 0 0 0 0 00 3 2 0 0 00 3 2 21 hhhh R hhhd R h Rd R R RdR R R Rd g Rg dt g Rg V Rhh h hRR Rh R R dRRRdRR R R R Rg R g R R t t RddtV E E −≈−−−=        −≈ =⋅=⋅−=      ⋅− <<+= << =⋅ −= = = ∫ ∫∫∫∫       µ µ ( ) ( ) ( )[ ]∫∫ −⋅=+⋅ t t T t t dtMqDTTV gm V dtTAV gm 00 ,,11 1 00 α  Specific Kinetic Energy Specific Potential Energy ( ) ( )[ ]∫ −⋅=        +−      +=− t t T dtMqDTTV gm V h g V h g V EE 0 ,,11 22 0 0 0 2 0 0 2 0 α Specific Energy Gain due to Thrust and Loss due to Aerodynamic Drag ( )011 >⋅ TVif Aircraft Equations of Motion Return to Table of Content
  • 159. SOLO ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )       ≥==−= ≥+×Ω=−=++= === min00 min00 00 / 1 mmtmmtmcTm VVvRtVRpATTRgTA m V RtRRtRVR ffvacuum fwindaevacuum ff    Equations of Motion (State Equations): . ( ) ( ) fttttuxftx ≤≤= 0,,, π Controls: ( ) fttttu ≤≤0 VectorThrustT ForcescAerodynamiA − −   Three Degrees of Freedom Model in Earth Atmosphere
  • 161. 161 SOLO • Rotation Matrix from Earth to Wind Coordinates [ ] [ ] [ ]321 χγσ=W EC where σ – Roll Angle γ – Elevation Angle of the Trajectory χ – Azimuth Angle of the Trajectory Force Equation: amgmTFA  =++ where: • Aerodynamic Forces (Lift L and Drag D) ( )           − − = L D F W A 0  • Thrust T ( )           = α α sin 0 cos T T T W  • Gravitation acceleration ( ) ( )                     −           −           − == g cs sc cs sc cs scgCg EW E W 0 0 100 0 0 0 010 0 0 0 001 χχ χχ γγ γγ σσ σσ ( ) g cc cs s g W          − = γσ γσ γ  α T V L D Bx Wx Bz Wz Wy By Flat Earth Three Degrees of Freedom Aircraft Equations
  • 162. 162 SOLO α T V L D Bx Wx Bz Wz Wy By • Aircraft Acceleration ( ) ( ) ( ) ( )WW W W VVa  ×+= → ω where: ( )           = 0 0 V V W  and ( )           = → 0 0 V V W   ( )                                         −+                     − +                     − =           = χ χχ χχ γ γγ γγσ σσ σσω     0 0 100 0 0 0 0 0 010 0 0 0 0 0 001 cs sc cs sc cs sc r q p W W W W or ( )           +− + − =           = γσχσγ γσχσγ γχσ ω ccs csc s r q p W W W W     therefore ( ) ( ) ( ) ( ) ( ) ( )           +− +−=           − =×+= → γσχσγ γσχσγω cscV ccsV V qV rV V VVa W W WW W W     Flat Earth Three Degrees of Freedom Aircraft Equations
  • 163. 163 SOLO α T V L D Bx Wx Bz Wz Wy By • Aircraft Acceleration Flat Earth Three Degrees of Freedom Aircraft Equations From the Force equation we obtain: ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )WWW A WW W W gTF m VVa  ++=×+= → 1 ω or ( ) ( ) ( )     ++−=+−=− =+−= −−= γσαγσχσγ γσγσχσγ γα ccgmLTcscVqV csgccsVrV sgmDTV W W /sin /)cos(    from which we obtain:       − + = = γσ α γσ coscos sin cossin V g Vm LT q V g r W W
  • 164. 164 SOLO α T V L D Bx Wx Bz Wz Wy By • Aircraft Acceleration Flat Earth Three Degrees of Freedom Aircraft Equations From the Force equation we obtain: ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )WWW A WW W W gTF m VVa  ++=×+= → 1 ω or ( ) ( ) ( ) σ σ σ σ γσαγσχσγ γσγσχσγ γα s c c s ccgmLTcscVqV csgccsVrV sgmDTV W W −− −      ++−=+−=− =+−= −−= /sin /)cos(    from which we obtain: ( ) ( )     += −+= −−= msLTcV cgmcLTV sgmDTV /sin /sin /)cos( σαγχ γσαγ γα    Define the Load Factor gm LT n + = αsin :
  • 165. 165 SOLO α T V L D Bx Wx Bz Wz Wy By • Velocity Equation Flat Earth Three Degrees of Freedom Aircraft Equations ( ) ( )           ==           = 0 0 V CVC h y x V E W WE W E                          −           −          − =           0 0 0 0 001 0 010 0 100 0 0 V cs sc cs sc cs sc h y x σσ σσ γγ γγ χχ χχ         = = = γ χγ χγ sVh scVy ccVx    or • Energy per unit mass E g V hE 2 : 2 += Let differentiate this equation: ( ) W VDT W DT g g V V g VV hEps − =            − − +=+== α γ α γ cos sin cos sin:   Return to Table of Content
  • 166. 166 SOLO Flat Earth Three Degrees of Freedom Aircraft Equations We have Aircraft Thrust( ) 10, ≤≤= ηη VhTT MAX ( ) ( ) soundofspeedhaNumberMachMhaVM === &/ ( ) ( )MSCVhL L , 2 1 2 αρ= Aircraft Lift ( ) ( )LD CMSCVhD , 2 1 2 ρ= Aircraft Drag ( ) ( ) ARe k CkMCCMC iDC LDLD π 1 , 2 0 = +=  Parabolic Drag Polar gm LT n + = αsin ' Total Load Number ( ) 0/ 0 hh eh − = ρρ Air Density as Function of Height gm L n = Load Factor
  • 167. 167 SOLO Constraints: State Constraints • Minimum Altitude Limit minhh ≥ • Maximum dynamic pressure limit ( ) ( )hVVorqVhq MAXMAX ≤≤= 2 2 1 ρ • Maximum Mach Number limit ( ) MAXM ha V ≤ Aerodynamic or heat limitation Three Degrees of Freedom Model in Earth Atmosphere
  • 168. 168 SOLO Constraints: • Maximum Load Factor ( ) MAXn W VhL n ≤= , • Maximum Roll Angle MAXMAX σσσ ≤≤− • Maximum Lift Coefficient or Maximum Angle of Attack ( ) ( ) ( )VhorMCMC STALLMAXLL ,, _ ααα ≤≤ ( ) ( ) ( ) ( ) ( ) LSTALL LMAXL nVh W VhC VSh W VhC VShn ==≤ , , 2 1, 2 1 2_2 αρρ α Control Constraints (continue): ( ) fttttuU ≤≤≤ 00, Three Degrees of Freedom Model in Earth Atmosphere
  • 169. 02/28/15 169 SOLO Control Constraints: ( ) fttttuU ≤≤≤ 00, • Thrust Controls options are: Thrust Direction Thrust Magnitude ( ) throttableVhTT rMAX 10, ≤≤= ηη Deflector Nozzle Thrust Reversal Operation F-35 Propulsion If no Thrust Vector Control (No TVC) BxT 11 = 1cos111 max ≤≤•≤− TBxT δ If Thrust Vector Control (TVC) Three Degrees of Freedom Model in Earth Atmosphere
  • 170. 02/28/15 170 ( ) ( ) ( ) ( ) ( )( ) ( ) ( ) ( ) ( )( ) ( ) ( ) ( )( ) ( ) ( ) γ χ γ χγ χγσ γ α σ γ βα χ χγγ χγσ α σ βα γ χγγ γ βα χγ χγ γ cos sincossin cos sincoscostan2 tansincossin cos sin cos cos sincos cossinsincoscoscos coscos2coscos sin sin sincos sinsincoscossincos sin coscos sincos cos coscos cos sin * 2 * 2 2 * V a LatLat V R LatLat Lat R V Vm LT Vm CT V a LatLatLat V R Lat V g R V Vm LT Vm CT LatLatLatR ag m DT V R V R V td Latd LatR V LatR V td Longd V td Rd yWW zWW xWW E N − Ω +−Ω− − + + + −= −+ Ω + Ω+      −+ + + + = −Ω+ −− − = == == =    (a) Spherical, Rotating Earth (Ω ≠ 0) SOLO Three Degrees of Freedom Model in Earth Atmosphere
  • 171. 02/28/15 171 (b) Spherical, Non-Rotating Earth (Ω = 0) ( ) ( ) ( )Lat R V Vm LT Vm CT V g R V Vm LT Vm CT ag m DT V R V R V td Latd LatR V LatR V td Longd V td Rd xWW E N tansincossin cos sin cos cos sincos coscos sin sin sincos sin coscos sincos cos coscos cos sin * χγσ γ α σ γ βα χ γσ α σ βα γ γ βα χγ χγ γ − + + + −=       −+ + + + = −− − = == == =    SOLO Three Degrees of Freedom Model in Earth Atmosphere
  • 173. 02/28/15 173 (a) Spherical, Rotating Earth (Ω ≠ 0) (b) Spherical, Non-Rotating Earth (Ω = 0) (c) Flat Earth 0→Ω ( ) ( ) ( ) ( ) ( )( ) ( ) ( ) ( ) ( )( ) ( ) ( ) ( )( ) ( ) ( ) χ γ χγ χγσ γ α σ γ βα χ χγγ χγσ α σ βα γ χγγ γ βα χγ χγ γ sincossin cos sincoscostan2 tansincossin cos sin cos cos sincos cossinsincoscoscos coscos2coscos sin sin sincos sinsincoscossincos sin coscos sincos cos coscos cos sin 2 2 2 * LatLat V R LatLat Lat R V Vm LT Vm CT LatLatLat V R Lat V g R V Vm LT Vm CT LatLatLatR ag m DT V R V R V td Latd LatR V LatR V td Longd V td Rd xWW E N Ω + −Ω− − + + + −= + Ω + Ω+      −+ + + + = −Ω+ −− − = == == =    ( ) ( ) ( )Lat R V Vm LT Vm CT V g R V Vm LT Vm CT ag m DT V R V R V td Latd LatR V LatR V td Longd V td Rd xWW E N tansincossin cos sin cos cos sincos coscos sin sin sincos sin coscos sincos cos coscos cos sin * χγσ γ α σ γ βα χ γσ α σ βα γ γ βα χγ χγ γ − + + + −=       −+ + + + = −− − = == == =    σ γ α σ γ βα χ γσ α σ βα γ γ βα γ ξγ ξγ sin cos sin cos cos sincos coscos sin sin sincos sin coscos sin sincos coscos Vm LT Vm CT V g Vm LT Vm CT g m DT V Vz Vy Vx E E E + + + −= − + + + = − − = = = =       SOLO ∞→R Three Degrees of Freedom Model in Earth Atmosphere Return to Table of Content
  • 174. 174 References SOLO Miele, A., “Flight Mechanics , Theory of Flight Paths, Vol I”, Addison Wesley, 1962 Aircraft Flight Performance J.D. Anderson, Jr., “Introduction to Flight”, McGraw Hill, 1978, Ch. 6, “Elements of Airplane Performance” A. Filippone, “Flight Performance of Fixed and Rotary Wing Aircraft”, Elsevier, 2006 M. Saarlas, “Aircraft Performance”, John Wiley & Sons, 2007 Stengel, MAE 331, Aircraft Flight Dynamics, Princeton University J.D. Anderson, Jr., “Aircraft Performance and Design”, McGraw Hill, 1999 N.X. Vinh, “Flight Mechanics of High-Performance Aircraft”, Cambridge University Press, 1993 F.O. Smetana, “Flight Vehicle Performance and Aerodynamic Control”, AIAA Education Series, 2001 L. George, J.F. Vernet, “La Mécanique du Vol, Performances des Avions et des Engines”, Librairie Polytechnique Ch. Béranger, 1960 L.J. Clancy, “Aerodynamics”, Pitman International Text, 1975
  • 175. 175 Brandt, “Introduction to Aerodynamics – A Design Perspective”, Ch. 5 , Performance and Constraint Analysis SOLO Aircraft Flight Performance J.D. Mattingly, W.H. Heiser, D.T. Pratt, “Aircraft Engine Design”, 2nd Ed., AIAA Education Series, 2002 Prof. Earll Murman, “Introduction to Aircraft Performance and Static Stability”, September 18, 2003 Naval Air Training Command, “Air Combat Maneuvering”, CNATRA P-1289 (Rev. 08-09) Patrick Le Blaye, “Agility: Definitions, Basic Concepts, History”, ONERA Randal K. Liefer, John Valasek, David P. Eggold, “Fighter Aircraft Metrics, Research , and Test”, Phase I Report, KU-FRL-831-2 References (continue – 1) B. N. Pamadi, “Performance, Stability, Dynamics, and Control of Airplanes”, AIAA Educational Series, 1998, Ch. 2 , Aircraft Performance L.E. Miller, P.G. Koch, “Aircraft Flight Performance”, July 1978, AD-A018 547, AFFDL-TR-75-89
  • 176. 176 Courtland_D._Perkins,_Robert_E._Hage, “Airplane Performance Stability and Control”, John Wiley & Sons, 1949 SOLO Asselin, M., “Introduction to Aircraft Aerodynamics”, AIAA Education Series, 1997 Aircraft Flight Performance References (continue – 2) Donald R. Crawford, “A Practical Guide to Airplane Performance and Design”, Crawford Aviation, 1981 Francis J. Hale, “ Introduction to aircraft performance, Selection and Design”, John Wiley & Sons, 1984 J. Russell, ‘Performance and Stability of Aircraft“, Butterworth-Heinemann, 1996 Jan Roskam, C. T. Lan, “Airplane Aerodynamics and Performance”, DARcorporation, 1997 Nono Le Rouje, “Performances of light aircraft”, AIAA, 1999 Peter J. Swatton, “Aircraft performance theory for Pilots”, Blackwell Science, 2000 S. K. Ojha, “Flight Performance of Aircraft “, AIAA, 1995 W. Austyn Mair, David L._Birdsall, “Aircraft Performance”, Cambridge University Press, 1992
  • 177. 177 SOLO E.S. Rutowski, “Energy Approach to the General Aircraft Performance Problem”, Journal of the Aeronautical Sciences, March 1954, pp. 187-195 Aircraft Flight Performance References (continue – 3) A.E. Bryson, Jr., “Applications of Optimal Control Theory in Aerospace Engineering”, Journal of Spacecraft and Rockets, Vol. 4, No.5, May 1967, pp. 553 W.C. Hoffman, A.E. Bryson, Jr., “A Study of Techniques for Real-Time, On-Line Optimum Flight Path Control”, Aerospace System Inc., ASI-TR-73-21, January 1973, AD 758799 A.E. Bryson, Jr., “A Study of Techniques for Real-Time, On-Line Optimum Flight Path Control. Algorithms for Three-Dimensional Minimum-Time Flight Paths with Two State Variables”, AD-A008 985, December 1974 M.G. Parsons, A.E. Bryson, Jr., W.C. Hoffman, “Long-Range Energy-State Maneuvers for Minimum Time to Specified Terminal Conditions”, Journal of Optimization Theory and Applications, Vol.17, No. 5-6, Dec 1975, pp. 447-463 A.E. Bryson, Jr., M.N, Desai, W.C. Hoffman, “Energy-State Approximation in Performance Optimization of Supersonic Aircraft”, Journal of Aircraft, Vol.6, No. 6, Nov-Dec 1969, pp. 481-488
  • 178. 178 SOLO Aircraft Flight Performance References (continue – 4) Solo Hermelin Presentations http://www.solohermelin.com • Aerodynamics Folder • Propulsion Folder • Aircraft Systems Folder Return to Table of Content
  • 179. 179 SOLO Technion Israeli Institute of Technology 1964 – 1968 BSc EE 1968 – 1971 MSc EE Israeli Air Force 1970 – 1974 RAFAEL Israeli Armament Development Authority 1974 – Stanford University 1983 – 1986 PhD AA
  • 180. 180
  • 181. 181
  • 182. 182M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring” Comparison Tables
  • 183. 183M. Corcoran, T. Matthewson, N. W. Lee, S. H. Wong, “Thrust Vectoring” Return to Table of Content
  • 185. 185 Ray Whitford, “Design for Air Combat” R.W. Pratt, Ed., “Flight Control Systems, Practical issues in design and implementation”, AIAA Publication, 2000
  • 186. SOLO
  • 187. SOLO
  • 188. 188 H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35
  • 189. 189 H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35
  • 190. 190 H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35
  • 191. 191 H.H. Hurt, Jr., “Aerodynamics for Naval Aviators “,NAVAIR 00=80T-80 1-1-1965, pg. 35
  • 200. 200
  • 203. 203

Editor's Notes

  1. J.D. Anderson, Jr, “Fundamentals of Aerodynamics”, McGraw-Hill, 3th Ed., 1984, 1991, 2001
  2. http://en.wikipedia.org/wiki/Earth%27s_atmosphere
  3. “Introduction to the Aerodynamics of Flight”, NASA History Office, SP-367, Talay, 1975
  4. Frank J, Regan, Satya M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993
  5. Frank J, Regan, Satya M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993
  6. Frank J, Regan, Satya M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993
  7. R.P.G. Collinson, “Introduction to Avionics”, Chapman &amp; Hall, Inc., 1996, 1997, 1998 Frank J, Regan, Satya M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993
  8. Frank J, Regan, Satya M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993
  9. R.P.G. Collinson, “Introduction to Avionics”, Chapman &amp; Hall, Inc., 1996, 1997, 1998 Frank J, Regan, Satya M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993
  10. R.P.G. Collinson, “Introduction to Avionics”, Chapman &amp; Hall, Inc., 1996, 1997, 1998 Frank J, Regan, Satya M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993
  11. R.P.G. Collinson, “Introduction to Avionics”, Chapman &amp; Hall, Inc., 1996, 1997, 1998 Frank J, Regan, Satya M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993
  12. Frank J, Regan, Satya M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993
  13. Frank J, Regan, Satya M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993
  14. “Introduction to the Aerodynamics of Flight”, NASA History Office, SP-367, Talay, 1975
  15. J.D. Anderson, Jr, “Fundamentals of Aerodynamics”, McGraw-Hill, 3th Ed., 1984, 1991, 2001
  16. http://en.wikipedia.org/wiki/Mach_number
  17. http://en.wikipedia.org/wiki/Mach_number
  18. J.D. Anderson, Jr, “Fundamentals of Aerodynamics”, McGraw-Hill, 3th Ed., 1984, 1991, 2001
  19. “Introduction to the Aerodynamics of Flight”, NASA History Office, SP-367, Talay, 1975
  20. J.D. Anderson Jr., “Ludwig Prandtl ‘s Boundary Layer”, Physics Today, December 2005, http://www.aps.org/units/dfd/resources/upload/prandtl_vol58no12p42_48.pdf
  21. Asselin, M., “Introduction to Aircraft Performance”, AIAA Education Series, 1997
  22. Asselin, M., “Introduction to Aircraft Performance”, AIAA Education Series, 1997
  23. http://en.wikipedia.org/wiki/Knudsen_number Angelo Miele, “Flight Mechanics, Volume 1, Theory of Flight Paths”, Addison Wesley, 1962, pg. 71 F.J. Regan, S.M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993, Ch.11 “Flowfield Description” J.D. Anderson, Jr., “Hypersonic and High Temperature Gas Dynamics”, McGraw-Hill, 1989, pp. 473-476
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  26. F.J. Regan, S.M. Anandakrishnan, “Dynamics of Atmospheric Re-Entry”, AIAA Education Series, 1993, Ch.11 “Flowfield Description”
  27. J.D. Anderson, Jr., “Hypersonic and High Temperature Gas Dynamics”, McGraw-Hill, 1989, pg.22
  28. http://en.wikipedia.org/wiki/True_airspeed
  29. Chapter 7 Flight Instruments http://www.gov/library/manuals/aviation/pilot_handbook/media/PHAK%20-%20Chapter%2007.pdf
  30. “Aerodynamics for Naval Aviators “,00=80T-80 1-1-1965
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