- Aircraft Design

W_f / W₀ = 1 + (W_x / W₀)

W_f / W₀ = 1 – (W_x / W₀)

W_f / W₀ = 1 + (W_x / W₀)

W_f / W₀ = 1 / (W_x / W₀)

Correct Answer :

Recently Updated in Aircraft Design Questions

Following diagram is showing mission profile with different phases with mission segment fuel fraction as shown. If crew weight is 150kg, payload of 600kg and empty fraction of 0.495. Determine gross weight of the aircraft.

4431lb

38910lb

4430kg

39810kg

Correct Answer : Option (C) : 4430kg

Explaination : Given crew weight = 150kg, payload weight = 600kg
Fuel weight fraction W_f / W₀ = 1.06[1 – W_x/W₀],
Now from fuel fraction method,
W_x / W₀ = multiplication of each phase fraction
= 0.975*0.98*0.96*0.8*0.96*0.97
= 0.6833
Now,
W_f / W₀ = 1.06 * [1 – (W_x / W₀)] = 0.3357
Empty weight fraction W_e / W₀ = 0.481
Gross weight of aircraft is,
W₀ = W_crew + W_payload + W_fuel + W_empty
By re-arranging,
W₀ = W_crew + W_payload / [1 – (W_f/ W₀) – (W_e / W₀)]
= 150 + 600 / [1-0.3357-0.495] = 4430kg

Total take-off gross weight depends on _____

independent

fuel consumption only

fuel, crew, payload and empty weight

only on aerodynamic efficiency

Correct Answer : Option (C) : fuel, crew, payload and empty weight

Explanation : Total take-off gross weight is nothing but the sum of all the possible aspects of an aircraft. Hence, it will depend on fuel weight, crew and payload weight and also on empty weight.

An aircraft has Crew and payload of 180kg. It has empty weight fraction of 0.48 and fuel weight is 0.7 times empty weight. What will be the gross weight of aircraft?

215kg

950kg

1000lb

2157lb

Correct Answer : Option (D) : 2157lb

Explanation : Given crew and payload = 180kg,
Empty weight fraction W_e / W₀ = 0.48
Fuel weight is 0.7 times empty weight.
Hence, W_f = 0.7*W_e
Hence, W_f / W₀ = 0.7*W_e / W₀ = 0.7*0.48 = 0.336
Gross weight of aircraft is,
W₀ = W_crew + W_payload + W_fuel + W_empty
By re-arranging,
W₀ = W_crew + W_payload / [1 – (W_f/ W₀) – (W_e / W₀)]
= 180 / [1-0.336-0.48] = 978.26kg = 2157.06lb.