This set of Aircraft Design Multiple Choice Questions & Answers (MCQs) focuses on “Loads Categories”.

1. Almost all the forces acting on aircraft can be categorized as _____
a) body or surface forces
b) body forces only
c) only as surface force
d) neither body nor surface force

Explanation: Typically, all aircraft forces are categorized as body forces or surface forces. Body forces are those forces which are acting through volume of the body. Typical example of body force is force due to gravity. Surface force is acting through surface of an object such as shear force.

2. What are the ground loads?
a) Loads acting due to aircraft motion on ground
d) Lift and drag

Explanation: Loads that are acting due to aircraft motion on the ground is termed as ground loads. Air loads and gust loads are loads acting during the flight phase. Lift and drag are Aerodynamic forces acting on the aircraft. Lift is responsible for lifting the aircraft and drag is a resistive force.

3. Air loads are loads typically experienced by an aircraft during flight in air.
a) True
b) False

Explanation: Air loads are defined as those loads which are acting on the aircraft during flight in the air. Air loads may include maneuver, gust, buffet, control deflection etc.

4. Which of the following is an example of air load?
a) Gust
b) Taxi
c) Wheel stress
d) Landing

Explanation: Gust is primarily experienced during flight phase of an aircraft. Gust is experienced during flight in air. Hence, gust is an example of air load. Landing, taxi etc. are examples of the ground loads.

5. The largest load that is expected to be experienced by aircraft is called __________
b) normal stress
c) normal strain
d) shear stress

Explanation: Limit load is the largest load that is expected to be experienced by aircraft. Shear force will produce shear stress. Stress is force per unit area and strain is defined as change in dimensions divided by original dimension.
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6. Design load is defined as ________
a) the Highest possible load that structure is designed to withstand without braking
b) the highest normal stress when strain is only quarter
c) the lowest load that structure has to withstand
d) lift and drag only

Explanation: Design load is the highest possible load that structure is designed to withstand without braking. The aircraft structure is always designed in order to withstand higher loads than the limit loads. Some factor of safety or safety margin is always used. Design load is also termed as the ultimate load.

7. Which of the following is correct?
a) Factor of safety is provided to improve safety of an aircraft
b) Lift is always same as weight
c) Weight is never same as lift
d) Thrust required is same as weight always

Explanation: The factor of safety is used in order to increase safety of the aircraft. Lift is not always same as the aircraft weight. Weight will be same as the lift during cruise. Thrust required is not always same as the weight.

8. If my factor of safety is 2 and design load of my aircraft is 1000N then, at which value of ultimate load my aircraft can withstand without breaking?
a) 2KN
b) 9N
c) 1208KN
d) 1.208KN

Explanation: Ultimate load without breaking = factor of safety * design load = 2*1000 = 2KN.

9. Which of the following is not categorized as powerplant load?
a) Taxing
b) Thrust
c) Torque
d) Duct pressure

Explanation: Taxing is not an example of power plant load. Powerplant load may include Thrust, torque, duct pressure, vibration etc. Thrust is propulsive force produced by the powerplant of an aircraft.

10. Loads during takeoff and landing will be equal in magnitude.
a) True
b) False

Explanation: Loads will be of different magnitude and of different kinds. During landing, landing gear are used to withstand the impact loads at the time of touchdown. However, at takeoff they do not experience such impact loads. Hence, magnitude of the loads will be different.

11. Choose an appropriate incorrect option.
a) At any given time, an aircraft can only experience any one type of load
b) At cruise, lift will be same as weight
c) Aerodynamic centre is located at quarter chord point for typical subsonic a/c
d) Lift is an example of Aerodynamic force

Explanation: At any given time, aircraft can experience the number of different types of loads. For example, at cruise aircraft experiences airloads, powerplant load etc. At cruise, lift and weight will be equal. Lift is an Aerodynamic force.

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