1. LANDING GEAR SHOCK ABSORBER DESIGN
CONCORDIA UNIVERSITY
MECH 7501, SUMMER 2009
Presented to :
Professor DR. S.V. HOA
Presented by :
Maruf Khondker (L) ID :
A.K.M Lutful kabir ID :
Amen Younes ID :
Md Shelimuzzaman ID :
Shafiul Islam ID :

2. OUTLINES Introduction Configuration Design and Analysis
Finite Element Analysis (FEA)
Material Selection and Manufacturing
Weight Estimation and Comparison.
Conclusion.
45 Second Video

3. INTRODUCTION
Landing gear is a critical part & has significant effect on aircraft performance.
The basic function is to support aircraft, absorb & dissipate impact kinetic energy.
Early build airplanes conventionally used metal skids as landing gear .
It is able to supports the airplane weight but is not able to absorb the landing shock.
Oleo Pneumatic shock absorber is selected for high efficiency as they can absorb & remove vertical kinetic energy simultaneously.
Composites are being increasingly used due to weight saving ,reduction in fabrication cost, specific stiffness & strength properties.

4. Small size civilian air craft
Aircraft Choosing
Beech craft Model 99.
Small size civilian air craft
Crew
One
Capacity
15 passengers
Length
44 ft 6¾ in (13.58 m)
Wingspan
45 ft 10½ in (13.98 m)
Height
14 ft 4⅓ in (4.37 m)
Empty weight
5,533 Ib (2,515 kg)
Loaded weight
10,400 Ib
Max takeoff weight
11,300 Ib (4,727 kg)
Power plant
Pratt & Whitney PT6A-20, -27

5. Hawker 850 XP Luxurious & Mid-size airplane
Aircraft Choosing
Hawker 850 XP.
Hawker 850 XP Luxurious & Mid-size airplane
Crew
Two
Capacity
8 to 15 passengers
Length
51 ft 2 in (15.60 m)
Wingspan
54 ft 4 in (16.56 m)
Height
18 ft 1 in (5.51 m)
Empty weight
15,670 Ib (7,108 kg)
Max Landing weight
23,350 Ib (10,591 kg)
Max takeoff weight
28,000 Ib (12,701 kg)
Power plant
Honeywell TFE731 – 5BR

6. Shock Absorber dimension calculations
Shock absorber choosing.
Type: Oleo-pneumatic shock absorber
Reason:
High efficiency.
absorb and remove vertical kinetic energy simultaneously.

7. Shock Absorber dimension calculations
Landing gear Load distribution

8. Shock Absorber dimension calculations
Main shock strut calculations:
Stroke calculation.
Piston outside diameter.
Inside cylinder diameter.
Total cylinder length.

9. Beech craft Model 99 Hawker 850 XP
Shock Absorber dimension calculations
Result of Dimension Calculations
Beech craft Model 99
Item
Nose landing gear
Main landing gear
Load at fully compressed position, Ib
3,420
9,125
Piston outside diameter, in
1.7
2.7
Cylinder inside diameter, in
1.95
3.15
Total stroke, in 12
Total cylinder length, in
16.6 20
Hawker 850 XP
Item
Nose landing gear
Main landing gear
Load at fully compressed position, Ib
7,980
22,800
Piston outside diameter, in
2.6
4.4
Cylinder inside diameter, in
2.9
4.9
Total stroke, in 8
Total cylinder length, in
15.15 20

10. STRESS ANALYSIS AND LAMINATE DESIGN
Methodology:
Netting theory.
Classical Lamination Theory (Layer by layer analysis.)

11. STRESS ANALYSIS AND LAMINATE DESIGN
Procedure:
Lay-up sequence choosing.
Strain in the laminate.
Off-axis & On-axis stress for each ply.
Hill-Tsai Criterion.
Evaluation

12. STRESS ANALYSIS AND LAMINATE DESIGN
Results

13. STRESS ANALYSIS AND LAMINATE DESIGN

14. STRESS ANALYSIS AND LAMINATE DESIGN

15. STRESS ANALYSIS AND LAMINATE DESIGN
Summary of Analysis

16. MATERIAL SELECTION
Different material has different properties. That are needed for various applications require the material should be chosen according to the choice of a given application.
Depending on a selection of a material, the design, processing, cost, quality and performance of the product change
Material selection is important to redesign an existing product for better performance, lower cost, increased reliability, decreased weight, etc

17. MATERIAL SELECTION
Material should be selected such that it can store the greatest elastic potential energy per unit volume without failure .
Component Specification
Shock resistance of landing
Resist the vibrations during the flight
Thermal requirements: -60°C<T<60 °C
Withstand water, humidity
Surface has to resist the impact during the landing
Smooth surface

18. MATERIAL SELECTION Reinforcement system Carbon fibers (UHM)
high strength and stiffness (E = 500 GPa)
tolerance to high temperatures and corrosion
low weight
expensive
Glass fiber ( R glass)
High strength
Medium stiffness (86 GPa)
Corrosion resistance
Fatigue resistance
Low cost w.r.t carbon fiber
Matrix system
Epoxy:
good mechanical properties (E = 4.5 GPa)
humidity resistance
adhere very well to reinforcement fibers

19. COMMON MATERIAL USED IN LANDING GEAR
Aircraft materials are of high specific strength, and corrosion-resistant alloys
Steel : provides low volume (as size is important) and high strength, can be made corrosion resistant. But the disadvantage is the weight of the steel. Most common landing gear steels are 4130, 4340, 4330V and 300M.
Aluminum alloys are lighter weight in combination with high specific strength . But this alloy is very prone to stress concentration T736 are being used in the landing gear for its better strength and stress-corrosion immunity.
titanium alloys , light weight and reduced corrosion susceptibility. Example Boeing’s 777 are using main gear structures that are mainly forged from the titanium alloy Ti-10V-2Fe-3Al from the mid-1990s.
Magnesium was used previously for the landing gear wheels, but now it is discarded due to the fire hazard and susceptibility to corrosion.

20. MATERIAL APPLICATIONS IN LANDING GEAR
Steel
Bogies,pistons,braces,links,switch brakets, plug, axle, shaft, spring, plate, clamp, sleeve, arm(tube), pin, bushing,
Aluminum
arm, collar, shimm, wheel, adapter assembly
Titanium
Main landing gear structure
Magnesium
No use right now due to fire hazard
Aluminum Bronze
Extremely used for upper and lower shock strut bearings
Beryllium
Brake heat sink material and bushing material
Composite material
Aircraft wheels, main landing gear parts including outer cylinder, pistons, side braces, torque arms, trailing arms, springs, wing panels, stabilizers and control surfaces

21. SCHEMATIC OF LANDING GEAR

26. Bonding Length Calculated 37 mm Considered in Design 40 mm
BONDING LENGTH CALCULATION
Consider : 3000 N-m
Bonding Length Calculated 37 mm
Considered in Design 40 mm

27. MANUFACTURING PROCESS
We selected the Fiber placement technology for manufacture of the cylindrical part of the landing gear. The fiber placement technology allows the fiber placement at any angle in conformance with the local load conditions.
Parts like drag brace, torque links are made by Resin Transfer moulding because it can be done at moderate pressure consequently reduces the cost.

28. FEA

29. Max Hoop Stress 1085 Mpa > Rupture = FAIL
FINITE ELEMENT ANALYSIS 1 (METAL LINER ONLY)
Max Hoop Stress Mpa > Rupture = FAIL
Metal Liner Standard Steel Gauge 25( 1 mm )
Pressure 3000 PSI (20.68 MPA)
Max Hoop Stress 1085 Mpa
Max Axial Stress 117 Mpa
Max Radial Stress 83.5 Mpa

30. Max Hoop Stress 986 Mpa << Rupture = OK
FINITE ELEMENT ANALYSIS 2 (HYBRID : COMPOSITE + METAL LINER)
Pressure 3000 PSI (20.68 MPA)
Max Hoop Stress 986 Mpa << Rupture = OK
Max Displacement mm

31. Max Hoop Stress 2301 Mpa ≈ Rupture = FAIL
FINITE ELEMENT ANALYSIS 3 (HYBRID : COMPOSITE + METAL LINER)
Pressure 7000 PSI (48 MPA)
Max Hoop Stress Mpa ≈ Rupture = FAIL
Max Displacement mm

32. Max Hoop Stress 949 Mpa ≈ Rupture = FAIL
FINITE ELEMENT ANALYSIS 3 ( METAL only – PISTON MADE OF FULL METAL )
Pressure 7000 PSI (20.48 MPA)
Max Hoop Stress 949 MPa
Max Hoop Stress Mpa ≈ Rupture = FAIL
Max Displacement mm

33. Max Hoop Stress 307 Mpa << Rupture = OK
FINITE ELEMENT ANALYSIS 4 ( METAL only – PISTON MADE OF FULL METAL )
Pressure 3000 PSI (20.64 MPA)
Max Hoop Stress Mpa << Rupture = OK
Max Displacement mm

34. SUMMARY OF FINITE ELEMENT ANALYSIS
Material
Wall Thickness (mm)
Pressure (Psi)
Max Hoop Stress (Mpa)
Rupture (Mpa)
Max Displacement (mm)
Metal Liner 1
3000
1085
1000
2.25
Composite + Metal 5
986
2500
0.247
7000
2301
0.576
Metal Only
307
0.104

35. WEIGHT REDUCTION CYLINDER (Steel + Composite) 42.75 %
MANUAL CALCULATION
CONSIDER FULLY METAL Kg
METAL LINER Kg
COMPOSITE
3.949 Kg
COMPOSITE Kg
% of weight reduction = ( – )/ =
42.75 %
CALCULATION USING CATIA
Bottom Torque Link (Steel + Composite)
Upper Torque Link (Steel + Composite)
40 %
47 %
57 %

36. CONCLUSION ADVANTAGES: LESS WIGHT. CORROSIVE RESISTANCE. NO RUST .
DISADVANTAGE
HIGH COST.
LOW PRODUCTION RATE.
DEFLECTION HIGHER THAN METAL.

37. 45 Second Video