# Aircraft Design Questions and Answers – Landing Gear – Shock Absorbers

This set of Aircraft Design Multiple Choice Questions & Answers (MCQs) focuses on “Landing Gear – Shock Absorbers”.

1. What is the function of the undercarriage?
a) To absorb the shock during landing
b) To provide lift
c) To increase lift at landing
d) To carry cargo at airport

Explanation: Undercarriage should absorb the shock or impact during landing and make ride smooth during taxiing. Lift is primarily generated by wings. Lift can be increased by high lift devices. Cargo container is used to carry cargo.

2. A typical glider will solely rely on tires for shock absorption.
a) True
b) False

Explanation: Typically, tires can provide some shock absorbing characteristics by deflection. Gliders or sail planes are built with rigid axles typically. Hence, they solely rely upon the tires for shock absorption. Hence, the correct answer will be true.

3. Which of the following is an example of a shock absorber?
a) Solid spring shock arrangement
b) Lift curve slope
c) Flap
d) Elevator

Explanation: Solid spring shock arrangement is an example of shock absorber. Lift curve slope is defined as change in lift by change in alpha. Flap is secondary control surface.

4. Which of the following is correct?
a) Solid spring shock absorber is heavier than the other types
b) Lift to drag ratio is always unity
c) Weight at takeoff is same as weight at landing
d) Thrust is same as drag always

Explanation: Solid spring shock absorber is heavier than the other types Lift to drag is not necessarily be unit always. Typically, a good design will have lift to drag ratio more than 1. During flight weight decreases and as a result takeoff weight and weight during landing will not be same.

5. Which of the following is correct?
a) The solid spring year deflects with some lateral motion
b) Lift is always same as weight
c) Drag polar shows lift variation with velocity

Explanation: Some lateral motion can be observed when we deflect solid spring. Lift is same as weight during cruise. Drag polar does not show lift variation with velocity. Thrust loading is ratio of Thrust and weight which cannot be same as lift.

6. Which type of shock absorber is most widely used nowadays?
a) Oleo
b) Signal beam type
c) Aurora beam type
d) Longerons type always

Explanation: Oleo type shock absorber is widely used shock absorber. Longerons are structural elements of the aircraft. They are straight and heavy. They are lesser in number and opposes the bending.

7. Following diagram represents ____________

a) simple oleo schematic
b) drag polar
c) wheel base distance only
d) wheel track only

Explanation: A typical oleo mechanism is shown in the diagram. Simple oleo system has been illustrated in the figure. Drag polar is graphical representation of drag characteristics. Wheel track and base distance are related to wheel terminology not to shock absorber.

8. Stroke of a shock absorber is defined as _________
a) required deflection of the shock absorbing system
b) lift required at takeoff
c) length of crank shaft of engine
d) piston distance travelled inside engine

Explanation: Stroke of absorber can be defined as the required deflection of the shock absorbing system. Stroke of the shock absorber depends upon number of factors such as shock absorbing material etc. Lift required at takeoff will be more than its weight.

9. If an aircraft has sink speed at touchdown as 9 ft/s then, find the stroke in inches approximately.
a) 9 in
b) 19 in
c) 1 in
d) 2 in

Explanation: Given, sink speed = 9 fps.
Required stroke in inch = vertical or sink speed = 9 inch.

10. If a tire has diameter of 18 in and rolling radius of 6 in then, what will be the approximate value of stroke of the tire?
a) 3 in
b) 4 in
c) 5 in
d) 8 in

Explanation: Stroke = (diameter/2) – rolling radius
= (18/2) – 6
= 9 – 6 = 3 in.

11. Determine the gear load factor if landing weight is 250 unit and average total load during deflection is 550 unit.
a) 2.2
b) 4
c) 4.5
d) 8.9

Explanation: Load factor is given by,
= 550/250 = 2.2.

12. An oleo is used as shock absorber in an aircraft. Determine at which external diameter we should design oleo if load on the oleo is 100 pounds.
a) 0.4 unit
b) 0.9 unit
c) 2.9 unit
d) 3.4 unit

Explanation: Diameter of oleo d = 0.04*(length of oleo)0.5
= 0.04*(100)0.5
= 0.4 unit.

13. If an aircraft has gear load factor of 3 and average total load during deflection is 180 unit then, find how much weight is carried during landing.
a) 60 unit
b) 10 unit
c) 100 unit
d) 283 unit

Explanation: Weight during landing W = load L / gear load factor
= 180/3 = 60 unit.

14. If piston diameter of an oleo system is given by 20 unit then, find the approximate value of typical external diameter of the same oleo system.
a) 26 unit
b) 10 unit
c) 50 unit
d) 200 unit

Explanation: Approximate value of external diameter can be given by,
D = piston diameter + 0.3* piston diameter
= 20 + 0.3*20 = 26 unit.

15. Stroke depends on ___________
a) vertical velocity at touchdown
b) vertical velocity at climb
c) rate of climb
d) lift by wing at cruise

Explanation: Stroke is defined as the amount of deflection required by shock absorbing system. Deflection required by shock absorber depends upon number of parameters. For example, vertical velocity at touchdown is one of the important factor affecting the stroke of the shock absorber. Lift at cruise will be same as weight at cruise.

Sanfoundry Global Education & Learning Series – Aircraft Design.

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