# Aircraft Design Questions and Answers – Thrust Weight Ratio-1

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This set of Aircraft Design Multiple Choice Questions & Answers (MCQs) focuses on “Thrust Weight Ratio-1”.

1. A/C with higher thrust to weight ratio can accelerate more quickly.
a) True
b) False

Explanation: Thrust to weight ratio is an important parameter. This ratio can affect the performance of an aircraft. Higher thrust to weight ratio represents more thrust for given weight. Hence, more quick acceleration, more maximum speed etc. can be achieved through higher values of thrust to weight ratio.

a) Yes
b) No
c) Both are same
d) Are not related to each other

a) higher maximum speed
b) lowest maximum speed
c) lowest climb
d) lowest acceleration

Explanation: Thrust loading is nothing but a ratio. It is the ratio of aircraft thrust to the weight of the aircraft. Higher thrust loading means higher thrust for given weight. This will improve maximum speed of an aircraft.

4. Thrust to weight ratio of all the aircrafts is same.
a) True
b) False

Explanation: Different type of aircrafts will have different requirements. Weight of different aircraft will be based on mission requirements. Thrust produced by engine will be different for all aircraft. Hence, thrust loading is not same for all the aircraft.

a) fuel burns with each mission phase
b) fuel is not burned at all
c) will not change
d) lofting is changed

Explanation: Thrust loading is generally measured based on take-off conditions. At each phase of mission profile weight will vary. Fuel burns throughout the flight which varies aircraft weight and which changes thrust loading as well.

a) greater or equal to one
b) same as lift of propeller
c) always be zero
d) equal to drag always

Explanation: Power loading for propeller driven aircraft is an important parameter representing the relation between power and weight. Power loading will always be greater than one and in much idle case it will be one. It cannot be zero. Lift and drag are forces.

7. Power loading of a prop driven aircraft is defined as _________
a) weight of aircraft to the horsepower by prop engine
b) weight of aircraft into the horsepower by prop engine
c) horsepower by prop engine
d) weight of aircraft

Explanation: Power loading will be defined as the ratio of weight of the aircraft to the power; typically horsepower produced by prop engine. It will impact on acceleration, climb, maximum speed etc. In general, it varies from 10-20.

8. Determine the corrections or otherwise of the following assertion [A] and reason [R]:
Reason[R]: Power loading of prop aircraft is ratio of power to the weight of the aircraft.
a) Both [A] and [R] are true and [R] is the correct reason for [A]
b) Both [A] and [R] are true but [R] is not the correct reason for [A]
c) Both [A] and [R] are false
d) [A] is false but [R] is true

Explanation: Power loading of prop aircraft is the ratio of weight of aircraft to the power produced by engine. Hence, [R] is false. Aerobatic aircrafts will require more power to perform different maneuvers. Hence, typical value of power loading will be around 4-7. Hence, [A] is also false.

9. Which of the following is correct for horsepower (hp) to the weight ratio?
a) T/W = (550*η / V) * (hp/W)
b) T/W = (550*η / V)
c) T/W = (550*η / V) + (hp/W)
d) T/W = (550*η / V) – (hp/W)

Explanation: Power is defined as thrust into velocity. Propeller will be operating with some finite value of propeller efficiency ƞ. 550 we multiply as to make units similar both the side.
T/W = (550*η / V)*(hp/W)

a) static sea-level conditions, take-off requirement etc
b) only Lift
c) only static sea-level conditions
d) only landing conditions

Explanation: When designer speaks for a thrust loading it generally refers to the value which has been calculated for standard day conditions, static sea-level conditions, take-off performance etc. Different phases incorporate different values of thrust loading. Hence, a designer typically converts them to take-off conditions.

11. A jet fighter aircraft is flying with maximum Mach number of 2.0. What will be the thrust loading of the fighter?
a) 0.57
b) 0.64
c) 2.5
d) 2.0

Explanation: Given, Jet fighter with max Mach number M = 2.0
T/W0 = a*Mc
For a jet fighter a=0.514, c=0.141
Hence, T/W0 = 0.514*2.00.141 = 0.566 = 0.57.

a) 846.15/V
b) 846.15
c) 650
d) 6.5

Since propeller is idle, propeller efficiency ƞ=1. Here, velocity is not mentioned so we will substitute it as V.
T.L. = T/W = (550*η / V)*(hp/W)
Hence, power loading W/hp = PL = 550*η / (T.L.*V) = 550/(V*0.65) = 846.15/V.

13. If a turboprop is cruising with 2275kg of weight, then determine power loading. Given power = 190hp.
a) 12
b) 5
c) 10
d) 25

Explanation: Given, weight at cruise W = 2275kg, power = 190hp.

14. An aircraft is cruising with lift coefficient of 2.5 and thrust loading of 0.6. Find drag coefficient of the aircraft.
a) 1.5
b) 2.5
c) 2.6
d) 2.59

Explanation: Given, lift coefficient CL = 2.5, thrust loading T/W = 0.6.
T/W = CD / CL
0.6 = CD / 2.5
CD = 0.6*2.5 = 1.5.

15. Following graph represents _____ a) thrust lapse at cruise
b) power lapse at cruise
c) temperature lapse rate
d) temperature variation 