1. D & C PDR #1 AAE451 – Team 3 November 4, 2003
Brian Chesko
Brian Hronchek
Ted Light
Doug Mousseau
Brent Robbins
Emil Tchilian

2. Conventional Tail – NACA 0012
Aircraft Walk Around
Wing Span = 14 ft
A/C Length = 10 ft
Conventional Tail – NACA 0012
Pusher
Low wing – Clark Y
Tricycle Gear

3. Introduction Dihedral angle Determine tail boom length
With boom length, find rotation angle
Determine horizontal stabilizer size
Is this realistic?
Determine vertical tail size
Calculate static margin based on sizing
Future Work

4. 5° dihedral is a good compromise
Dihedral Angle
Recommendations
Survey of Roskam data on homebuilt & agricultural low-wing aircraft: ~5°
McCombs “Wing and Tail Dihedral…”
RC w/ailerons (for max maneuverability, low wing): 0-2° EVD (Equivalent V-Dihedral ≈ dihedral)
Free Flight Scale model low wing: 3-8° EVD
5° dihedral is a good compromise

5. Tail Boom Length Trade Study
Used to determine optimum (lightest weight) tail boom length
Goal: minimize weight of tail system (boom, horizontal tail, vertical tail) based on location of tail

6. Tail Boom Length Trade Study
Assumed rectangular boom cross section based on maximum bending stress
Horizontal and vertical tail size determined based on 1st order tail sizing
Multiplied boom and tail volumes by respective density to get weight

7. Tail Boom Length Trade Study
Logic
Tail moment needed for stability
Moment = distance x force
Tail boom length increases Boom Weight Increases
Tail Weight Decreases
Tail boom length decreases Boom Weight Decreases
Tail Weight Increases
Assumptions
Boom Material: Bass Wood
Boom Geometry: Solid Rectangular Cross Section
Tail Construction: Foam Core / Fiberglass Shell

8. Tail Boom Length Trade Study
Optimum tail boom length gives a total aircraft length of ~14.1 ft
Aircraft Length Limit: 10 feet
Based on transportability constraint
If length is greater than 10 ft, A/C will be difficult to transport in a conventional vehicle
Weight gain: ~0.5 lbf

9. Tail Boom Length Trade Study

10. That’s great, what about rotation angle?
~12o of available rotation
12 degrees of rotation based on:
Gear height of 1.0 foot
Rear gear located below rear spar (60% of the chord of main wing)
Is 12o enough? Not sure yet. Looking into it.

11. Class 2 Tail Sizing
More Analytical than Initial Estimates from Class 1 method
Use different Horizontal and Vertical Tail Areas to calculate valuable characteristics of aircraft
Compare to Class 1 estimates for both Tail Sizes: Sh
8.8 ft2 Sv
3.5 ft2

12. Class 2 Horizontal Tail Sizing
Horizontal Tail important factor of Longitudinal Stability Equations for aircraft
Calculate Center of Gravity and Aerodynamic Center of aircraft for a range of Horizontal Tail Area values
Center of Gravity of Aircraft
Weight of Horizontal Tail changes with area
Note: 0.44 lbs/ft2 based on aircraft sizing code

13. Class 2 Horizontal Tail Sizing
Aerodynamic Center as a function of Horizontal Tail Area
Desired Static Margin
Roskam Eq 11.1
Raymer Fig 16.12

14. Horizontal Tail X-Plot
Compares Area of Horizontal Tail to Position of Center of Gravity in Respect to Aerodynamic Center
Best Position

15. Horizontal Tail Sizing
CGAC/ACAC analysis does not cover full breadth of operating envelope
Use Takeoff Rotation to analyze Horizontal Tail potential to rapidly increase angle of aircraft on runway

16. Horizontal Tail Sizing
This sizing based on angular acceleration during take-off rotation
Ref. Roskam 421 book, pg
Variable defintiions found in above reference

17. Horizontal Tail Sizing
values for different values of Horizontal Tail Area at instant time of rotation
Wheel-Ground Friction Coefficient
For lighter airplanes:
Long Grass
Concrete
For our concrete runway:

18. Horizontal Tail Sizing
Need to iterate between both methods
Use results for Horizontal Tail area from Takeoff rotation method to find a new Center of Gravity and Aerodynamic center
Use new CG and AC values for aircraft in Takeoff rotation problem
Results used for Vertical Tail Analysis:

19. Class 2 Vertical Tail Sizing
Vertical Tail sized from Coefficient of Yaw Moment due to Sideslip
Roskam Eq 11.8
Vol 2
Due to Wing and Fuselage:
Roskam Eq 10.42
Vol 6

20. Class 2 Vertical Tail Sizing
Overall level of directional stability must be
To meet coefficient value

21. Does Tail Size Make Sense?
Need to compare calculated horizontal tail size to historical data
Use Tail Volume Coefficient method to check
> Homebuilt value of 0.50
< Homebuilt value of 0.04

22. C.G. and A.C. of Aircraft Aerodynamic Center Center of Gravity
Center of gravity of aircraft is 3.5 feet behind the nose
Aerodynamic center is 4.0 feet behind the nose
Static margin ~ 0.17

23. Quick 3-View

24. Future Work Control surface sizing Continue working with Predator code
Many constants already estimated, still need to verify some
Look into advantages / disadvantages of moving horizontal tail into prop wash
Stall characteristics?
Necessary rotation angle

25. That’s a fine looking airplane!
Questions?
That’s a fine looking airplane!
That’s pimp Dad!
Airplane not to scale
Ref.

26. Source: McCombs, William F. “Wing and Tail Dihedral for Models.”
Dihedral Angle
EVD = A + kB
A = 0°
k = f(x/(b/2)) = 0.98
B = EVD / k ≈ EVD
A=0° B X CL
Source: McCombs, William F. “Wing and Tail Dihedral for Models.”