1. Structures PDR #2 AAE451 – Team 3 December 2, 2003
Brian Chesko
Brian Hronchek
Ted Light
Doug Mousseau
Brent Robbins
Emil Tchilian

2. Introduction Walk Around Landing Gear Placement Landing Gear Design
Landing Gear Analysis
Updated Weight Assessment

3. Aircraft Walk Around Wing Span = 14.4 ft Wing Chord = 2.9 ft
A/C Length = 10 ft
T-Tail – NACA 0012
Pusher
Internal Pod
Tricycle Gear
Low wing – Clark Y

4. Landing Gear Placement (I)
θ = tipback angle =
Landing gear placement based on
guidelines found in Raymer

5. Landing Gear Placement (II)
γ = overturn angle =
Landing gear placement based on
guidelines found in Raymer

6. Landing Gear Design Safe and Strong Easy to Construct
Aluminum for structure
Rubber bungee to absorb energy
Do not break airplane if gear fails
Easy to Construct
Weldable (the aluminum, not the bungee)
Easily Obtainable

7. Rear Gear Design

8. Easily Obtainable Square Tubing
Ref.

9. Buckling of Rear Gear Load L Load For Rear Gear: L ~ 15.3 in
Ref. Gere pg. 763 L
Where L = Length (in)
E = Young’s Modulus (psi)
I = Moment of Inertia (in4)
A = Cross Sectional Area (in2)
Load
Assumptions:
Pinned-Pinned Column
1st Mode Buckling
No Eccentricity
For Rear Gear:
L ~ 15.3 in

10. Compressive Failure of Rear Gear
Load L
Ref. MIL-HDBK-5H: 3-255
Where Load = (Weight)(S.F.)(Gloading)
A = Cross Sectional Area (in2)
Load
Assumptions:
Weight = 53 lbf
Gloading = 10
S.F. = 1.5
Aluminum 6061-T6
No Buckling

11. Smallest easily obtainable tubing: 1” x 1” x 0.062”
Stress on Rear Gear
Smallest easily obtainable tubing: 1” x 1” x 0.062”
t=0.062”
t=0.125”

12. Great, what about the bungee?
Consider worst reasonable landing situation
Moving at (1.1)Vstall
5 feet above ground
Aircraft falls out of the sky
Can the bungee absorb the energy associated with this landing?

13. Great, what about the bungee?
Assumptions:
Weight = 53 lbf
Vstall = 30 ft/sec
Altitude = 5 ft
Don’t want x to exceed 3 inches (beyond initial stretch) on landing

14. What Spring Constant is Needed?
Required k ~ 3.75 lbf/in
1/k ~ in/lbf

15. What is the Spring Constant?
Relaxed Length ~18 inches

16. Front Gear Design Aluminum Bolt Nylon Bolt Front Gear
Provides pivot for gear (does not break)
Nylon Bolt
Breaks during hard landing
Front Gear
Designed not to break
Designed not to bend

17. How Big is the Bolt? Diameter of nylon bolt = 0.5 in Load Reaction
Ref. Gere pg 900
Load
If load = (Weight)(S.F.)(Gloading) = 795 lbf
Reaction = 1770 lbf (instantaneous)
Need cross sectional area of bolt to be in2
Diameter of nylon bolt = 0.5 in
Reaction
Assumptions:
Weight = 53 lbf
Gloading = 10
S.F. = 1.5
3.1”
6.9”

18. Updated Weight Estimate

19. Questions?