Aerodynamic forces

1. 7/13/2023 1
Aerodynamics Preliminary Design Review

2. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
2
Objectives
Concept selection & constraint analysis review
Preliminary selection of airfoil, geometry, & aircraft layout
- Airfoil
- Aspect Ratios
- Taper
- Sweep
- Span
- Chord
- Wing & tail location
Preliminary aerodynamic analysis
- Whole Aircraft CL & CD
- Cruise a & drag estimates

3. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
3
Constraint analysis
Constraint analysis review
- Turn rate constraint is correct
- Design constrained by turn rate for high turn speeds (Vturn = Vloiter)
- Design constrained by Ground Roll & Climb rate for lower turn speeds (Vturn = 20 ft/s)
- Vturn = 25 ft/s for constraint analysis

4. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
4
Constraint Analysis
Original Constraint Diagram Modified Constraint Diagram
- Modified constraint allows for an increased power loading
- Smaller propulsion system required to meet requirements (P30=0.422Hp P25=0.182Hp)

5. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
5
Airfoil, Geometry, & Layout Selection
Airfoil Selection
- 25 Airfoils considered
- Compared airfoils using:
- Clmax, Cla
- Drag Polar (design point of W/S=0.58)
- CL= (1/q)(W/S) = 0.55 ~ Cl
- Manufacturing & structural considerations (thickness & trailing edge shape)
- Current analysis uses same airfoil for both wings
- Selig S1210 airfoil selected
- L/Dmax = 74.5
- Clmax = 1.82
- Cdmin = 0.0138
- Max Thickness = 12.1%
Selig S1210

6. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
6
Airfoil, Geometry, & Layout Selection
Cl vs. a
- Selig S1210 shows large Clmax advantage over other airfoils studied
- Cla approximately the same for all airfoils
Non-Selig Cl vs. Alpha
-1
-0.5
0
0.5
1
1.5
2
-10 -5 0 5 10 15 20
Alpha (deg)
Cl
Selig Cl vs. Alpha
-1
-0.5
0
0.5
1
1.5
2
-10 -5 0 5 10 15 20
Alpha (deg)
Cl
Selig S1210

7. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
7
Airfoil, Geometry, & Layout Selection
- S1210 has higher Cdmin
- However the L/Dmax is the highest of all considered airfoils
Cl vs. Cd
Non-Selig Cl vs. Cd
-1
-0.5
0
0.5
1
1.5
2
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05
Cd
Cl
Selig Cl vs. Cd
-1
-0.5
0
0.5
1
1.5
2
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05
Cd
Cl
Selig S1210

8. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
8
Concept, Airfoil, Geometry, & Layout Selection
Tandem wing concept chosen
- Slight increase in required analysis
- Concept has good overall characteristics for mission
- No major problems with concept
- Added market value due to unique design
Geometry Selection
- Geometries selected using historical data & trends from Raymer
- SAE, ICAS, & industry papers on tandem wing & canard configurations used for tandem
wing sizing properties
Aspect Ratio, AR
- Feistel, et al, SAE paper shows that the forward wing should be at a higher aspect ratio
than the rear wing to allow the front wing to stall first
- Aspect ratios chosen from historical data and structural concerns
- ARFW = 8 ARRW = 7
- Detailed analysis of configuration may change AR

9. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
9
Airfoil, Geometry, & Layout Selection
Sweep (1/4 chord), L
- No sweep is desirable for low speed flight, cruise, and takeoff & landing (Raymer, pg. 61)
Taper Ratio, l
- Historical data and trends from Raymer used to choose taper ratio
- Taper ratio required to approximate elliptical lift distribution (Raymer, pg. 64)
- Wing sweep effects on taper ratio were also taken into account (Raymer, pg. 65)
- Taper ratio for both wings = 0.45
- Taper ratio may not be used depending on construction technique and material choice
Span & Chord, b & c
- Span and chord calculated using design area, aspect ratio, and area ratio
- bwing = (Swing * ARwing)2
- cavg,wing = Swing / bwing
Wing b (ft) c (in)
Front 5.94 8.91
Rear 5.56 9.53

10. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
10
Airfoil, Geometry, & Layout Selection
Dihedral
- Dihedral chosen using estimates in Raymer for high wing (pg. 68)
- 3o Dihedral chosen for both wings
Wing Separation / Location
- Feistel, et al, SAE paper shows that the front and rear wing should be separated
vertically and horizontally as much as possible (Vsep ~ 0.5*cavg Xsep as large as possible)
- Vsep = 6 in
- Xsep = 4 ft
Vertical Tail Sizing & Location
- Tail sized using historical data (previous AAE 451 classes)
- Will be updated with Stability & Control calculations
b (ft) 1.4
c (in) 9
Vertical Tail

11. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
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Geometry & 3 View
Front Rear
Wing Wing
Area (ft2
) 4.42 4.42
AR 8 7
Sweep (deg) 0 0
Taper Ratio 0.45 0.45
Span (ft) 5.94 5.56
Chord - avg (in) 8.91 9.53
Chord - root (in) 12.3 13.14
Chord - tip (in) 5.53 5.92
Dihedral (deg) 2 2

12. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
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Geometry & 3 View

13. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
13
Geometry & 3 View

14. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
14
Aerodynamic Analysis
Lift
 
max
2
2
tan
1
AR
4
AR
2
2
t
e
L




 Brandt, 4.15








AR
3
.
57
1
e
c
c
C
l
l
L

a
a
a
Brandt, 4.14












 











b
z
l
c
C h
h
avg
L
1
7
3
10
AR
21
0.725
l
a
 a
Brandt, 4.21
S
S
C
C t
L
L t











a

a
a
1 Brandt, 4.22
  a
a
a L
L
L C
C
C 


aircraft
whole Brandt, 4.25 (Wings only)
 
0
max
max 

 L
L
L C
C a
a
a Brandt, 4.17

15. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
15
Aerodynamic Analysis
Drag
75
.
0

e Raymer, to approximate elliptical loading
    65
.
0
2
58
.
2
10 M
144
.
0
1
Re
log
455
.
0


f
C Raymer, 12.27 (For urbulent flow)
 
 
 
28
.
0
0.18
4
cos
M
34
.
1
100
x
0.6
1
FF m
m c
t
c
t
c
L






















 Raymer, 12.30 (Wings & VT only)
0
.
1

FW
Q Raymer, page 346
2
.
1

RW
Q
0
.
1

W
Q
 
 
c
t
S
S osed
wet 52
.
0
977
.
1
exp 
 Raymer, 7.11

16. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
16
Aerodynamic Analysis
**************** Front Wing Summary ****************
Front Wing Area (ft2) = 4.42
Front Wing Span (ft) = 5.94
Front Wing Average Chord (in) = 8.91
Front Wing Root Chord (in) = 12.30
Front Wing Tip Chord (in) = 5.53
Front Wing Spanwise Efficiency = 0.89
Front Wing 3D CLalpha (1/deg) = 0.0718
------------------------------------------------------
***************** Rear Wing Summary *****************
Rear Wing Area (ft^2) = 4.42
Rear Wing Span (ft) = 5.56
Rear Wing Average Chord (in) = 9.53
Rear Wing Root Chord (in) = 13.14
Rear Wing Tip Chord (in) = 5.92
Rear Wing Spanwise Efficiency = 0.88
Rear Wing Standalone 3D CLalpha (1/deg) = 0.0698
Rear Wing Downwash effect = 0.0956
Rear Wing 3D CLalpha (1/deg) = 0.0631
-------------------------------------------------------
*************** Whole Aircraft Summary ***************
Whole Aircraft 3D CLalpha (1/deg) = 0.1349
Whole Aircraft CLmaxTO = 2.29
Whole Aircraft 3D CD = 0.0380

17. 7/13/2023 Phoenix Aerospace
AAE 451 – Fall 2001
17
Airfoil, Geometry, & Layout Selection
- The larger the Cla, the greater the losses due to 3-Dimensional effects
- Cla for compared airfoils was constant, thus not a large driver of airfoil selection
Cl losses due to 3D effects
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Cla
%
2D
(C
La
/C
la
)
AR = 8
AR = 10
AR = 12