Aircraft Tail Design Optimization Study

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

2. 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 • Is this realistic? • Calculate static margin based on sizing • Future Work

4. 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:

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 288-290 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. Questions? That’s a fine looking airplane! That’s pimp Dad! Airplane not to scale Ref. http://roger.ecn.purdue.edu/~andrisan/Miscellaneous/Isle_Royale/IsleRoyale1/IsleRoyale1.html

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