Aircraft Design: A Systems Engineering Approach, M. Sadraey, Wiley, 2012 Chapter 9 Landing Gear Design Figures cg strut wheel Main gear Height (H) Wheel base (B) cg Height (H) Wheel track (T) Figure 9.1. Landing gear primary parameters 1
Identify and prioritize landing gear design requirements Select landing gear configuration Select fixed or retractable Determine landing gear height Determine the distance between main gear to the aircraft center of gravity Determine wheel base Determine wheel track Determine load on each gear Is this landing gear satisfying the design requirements? No Yes Design/determine landing gear mechanical subsystems/parameters such as tires selection, retraction system, strut diameter, Castoring-wheel, shock absorber Optimization Figure 9.2. Landing gear design flowchart 2
Bottom view Side view 1. Single main 2. Bicycle 3. Quadricycle Bottom view Side view 4. Tricycle 5. Tail-gear 6. Multi-bogey 7. Releasable rail 8. Skid Figure 9.3. Landing gear types 3
1. Glider PZL-Bielsko SZD-48 Jantar Standard 3 with bicycle landing gear (Courtesy of Miloslav Storoska) 4
2. Douglas C-47A Skytrain (Courtesy of Jenny Coffey) 5
3. Transport aircraft McDonnell Douglas MD-88 with tricycle landing gear (Courtesy of Anne Deus) 4. Bomber aircraft B-52 Stratofortress with quadricycle landing gear is using parachute during a landing operation (Courtesy of Antony Osborne) 6
5. Transport aircraft Boeing 747 with multi-bogey landing gear (Courtesy of Anne Deus) Figure 9.4. Five example aircraft with various landing gear configurations 7
Aircraft or launcher Figure 9.5. Missile attachment 3-10 deg Tip float Waterline Deadrise Deadrise angle Spray strip a. Front-view CG Chine centroid b. Side-view Figure 9.6. Sea-plane landing provision geometry Waterline 8
Figure 9.7. Amphibious aircraft Canadian Vickers PBV-1A Canso (Courtesy of Jenny Coffey) 9
Figure 9.8. A pilot during running to launch himself off the top of a hill aboard a hang glider (Courtesy of Christopher Huber) 10
1. Van's RV-7 (Courtesy of Jenny Coffey) 11
2. Ilyushin IL-18 (Courtesy of A J Best) 12
3. Vickers VC10 (Courtesy of A J Best) 13
4. McDonnell Douglas C-17A Globemaster (Courtesy of Anne Deus) Figure 9.9. Example aircraft for landing gear attachments 14
Figure 9.10. Aircraft Jindivik releases landing gear after take-off (Courtesy of http://www.militaryimages.net) 15
1. Fuselage podded (front-view) 2. In the wing (top-view) 3. In the fuselage (side-view) Figure 9.11. Landing gear storage bay 16
1. Dassault Mirage 2000 with retractable landing gear (Courtesy of Jenny Coffey) 17
2. Robin DR-400-120 Dauphin with faired fixed landing gear (Courtesy of Jenny Coffey) 18
3. Hawker Siddeley Nimrod with retractable landing gear (Courtesy of Antony Osborne) 19
4. Gippsland GA-8 Airvan with unfaired fixed landing gear (Courtesy of Jenny Coffey) Figure 9.12. Four aircraft with various landing gear 20
H LG H LG 1. LG is attached to the fuselage (solid spring) 2. Main gear is attached to the wing H LG H LG 3. LG is attached to the fuselage (with outriggers) 4.Main gear is attached to the nacelle H LG H LG 5. LG is attached to the fuselage (rubber bungee) 6. LG is attached into the fuselage (no strut) Figure 9.13. Landing gear height in various aircraft configurations 21
1. Take-off rotation ground clearance of Airbus A330 (Courtesy of Anne Deus) 22
2. Take-off rotation ground clearance of McDonnell Douglas F-15C Eagle (Courtesy of Antony Osborne) 23
TO B A clearance 3. Geometry of Take-off rotation ground clearance Figure 9.14. Take-off rotation and rear fuselage clearance C H f B C C TO A H C Fuselage O Runway Figure 9.15. Examination of rear fuselage clearance during take-off rotation 5 m 1 m Figure 9.16. Figure for Example 9.1 24
cg cg W A o ½ F m F n T ½ F m F n B n W B Figure 9.17. Wheel load geometry F m B m x Ground z Bm min Bn max Bn min Bm max cg for cg aft H cg F n Nose wheel B F m Main wheel o Figure 9.18. Wheel load geometry 25
H cg cg cg H cg ot ot Y ot Wheel track Y ot ot based on top-view ot based on front-view Figure 9.19. Overturn angle cg V cg F C H cg W ot F C R T Y ot 1. Top-view Front-view Figure 9.20. An aircraft in a ground turn and overturn contributing factors 26
F W F W CA Cross wind cg CA W H C Cross wind O T 1. Top-view Front-view Figure 9.21. An aircraft in a ground turn and overturn contributing factors Y ot A S cg Centroid H C Figure 9.22. Aircraft side area and its centroid 27
y F x y max W T l 1. Aircraft structure 2. Beam with two simple supports Figure 9.23. The aircraft structure at front view may be modeled as a beam with two simple supports tb Vertical Vertical tf TO cg cg h cg fi 1. Aircraft with tricycle landing gear 2. Aircraft with tail-wheel landing gear Figure 9.24. Tipback angle, tipforward angle and take-off rotation 28
x- Ref. line X mg L wf Xac h V R Xac wf Mo wf T ma D Z cg Z T F f Z D L h X cg W Main gear x z z-ref. line Figure 9.25. Forces and moments during take-off rotation 0.24C 0.2C 12 m 2 m cg ac wf 2.4 m T ac h 3 m D C Figure 9.26. Aircraft in Example 9.7 29
Wheel Tire D t Figure 9.27. Tire geometry W t 1. Solid spring 2. Oleo shock strut Figure 9.28. Landing gear with shock absorber 30
Rake angle Trail Figure 9.29. Steering wheel geometry Fuselage Figure 9.30. Landing gear retraction subsystem 31
D 1.2 m 11.6 m 21 m 27 m cg 4 m Figure 9.31. Aircraft in Example 9.8 32
cg 1.9 m 2.966 m 1.9 m 1.2 m 3.1 m Figure 9.32. Prop clearance x mg cg for h cg Figure 9.33. Main gear and forward cg 33
1.9 m B 7.081 m Fuselage upsweep point C C TO A H C Fuselage Figure 9.34. Examination of rear fuselage clearance during take-off rotation T/2 cg Fuselage 30 o Wing 3.1 m Figure 9.35. Wheel track (front view) 34
cg D H cg E1 ot D1 Y ot Nose gear A E cg D Y ot C F Main gear 1. Aircraft top view 2. Top view (main gear and nose gear) Figure 9.36. Calculation of the overturn angle for the aircraft in Example 9.8 35
1.916 m 1.827 m cg for cg aft 2.966 m 12.775 m 1. Wheel base, landing gear height, and main gear to cg cg cg 2.966 m 1.2 m 3.58 m 2. Wheel track, clearance, and wheel height Figure 9.37. The aircraft in Example 9.8 with the designed landing gear (figure not scaled) 36
1.3 m 12 m Figure 9.38. Figure for problem 5 12 m 2 m cg ac wf 2.4 m T ac h 3 m D Figure 9.39. Aircraft in problem 17 37
cg 1.6 m D 15 m 24 m 35 m Figure 9.40. Aircraft in problem 19 cg D 2.2 m 1.4 m 20 m 32 m 48 m Figure 9.41. Aircraft in Problem 20 38