Like this presentation? Why not share!

# Tsl Thrust to Weight ratio and Aspect Ratio

## on Oct 20, 2010

• 1,618 views

### Views

Total Views
1,618
Views on SlideShare
1,618
Embed Views
0

Likes
0
32
0

No embeds

### Report content

• Comment goes here.
Are you sure you want to

## Tsl Thrust to Weight ratio and Aspect RatioPresentation Transcript

• TSL_Oct2010
Thrust to weight Ratioand Aspect Ratio
NguyễnAnhTuấn
Naval Architecture and Marine Engineering tuanshipland@gmail.com
(+84) (0) 944 113 787
• T/W Ratio
T/W ratio estimates:
Part of the takeoff distance
Rate of climb
Maximum velocity
http://www.centennialofflight.gov/essay/Theories_of_Flight/Performance_Class2/TH25G1.htm
• Takeoff distance = sg+ sa = 2500 ft
According eq. [6.95] (see [1]), Ground Roll sg
For Flap
Plain Flap deflection 20ofor takeoff (see table 5.3 [1])
Section maximum lift coeffient∆(cl)max of45o flap deflection is 0.9 (see Fig.5.28, [1])
∆(cl)max= 0.9 (20/45) ~ 0.5 (For linear changes)
For the whole of wing, average (cl)max= 1.7 + 0.5 = 2.2

Raymer, Ref [25] of [1]
3D- effect of the finite aspectratio
=
Flight path angle
= 50 ft : obstacle height
Airborn distance
Takeoff distance = sg+ sa = 2500 ft
Velocity of airplane
Gross takeoff weight = 5,158lb
The liftoff velocity
Requirement powerPA =
Shaft brake power
Note: 550ft.lb/s = 1hp
Power of the takeoff constraint ≥ 119 hp
• P
PR = PA
T/W ratio
and Aspect ratio
Effects
T/W
V∞

Wo
sg
sa
𝜃𝑂𝐵

R
Vstall
VLO
T/W
W/S
(Cl)max
(cl)max
• Maximum Rate of climb (R/C)max = 1000ft/min = 16.67 ft/s at sea level
Single-engine general aviation airplanes
The ratio of wetted area to the wing referenece area Swet/Sref= 4 (See fig. 2.54, [1])
The skin –friction coefficent (for early jet fighters) Cfe = 0.0043 corressponds to Reynolds number Re = 107 (See fig 2.55, [1])
• The zero-lift drag coefficient (the zero-lift parasite drag coefficient)
The drag polar for airplane
The drag due to lift (downwash and so on)
The span efficiency factor to account for a nonelliptical lift distribution along the span of the wing e
The coefficient
=
= 0.075
Based on data from famous existing airplanes, estimating a reasonable first approximation for maximum of Lift to Drag ratio for 4-6 peoples aircraft (See p.403 [1])
A reasonable estimate The Oswald efficiency eo for a low-wing general aircrafts is 0.6 (See p.415 [1])
=7.07
• Maximum rate of climb for a propeller-driven airplane
Shaft Brake Power for the constraint of rate of climb
W/S
K
Wo
Aspect Ratio
• Themaximum velocity V∞ = Vmax = 250 mi/h = 366.7 ft/h at midcruise weight and level flight 20,000ft
In level flight T=D

The weight at maximum velocity is less than the weight at takeoff stage
The midcruise weight WMC
Estimating the weight fraction
• Gross takeoff weight = 5,158lb
For a propeller-driven aircraft, we use power to weight ratio
For a jet aircraft, we use thrust to weight ratio
T/W and P/W are same mean
• Thank you!
• References
[1] John D. Anderson, Jr. 1999. Aircraft Performance and Design. McGraw-Hill
[2] E. L. Houghton and N. B. Carruthers. 1986. Aerodynamics for Engineering Students. 3rd edition. Thomson Press