Aircraft Design MCQ – Conceptual Sketch Sizing – Fuel-Fraction Estimation-1
1 - Question
Aircraft fuel weight does not include reserved fuel fraction.
Explanation: The total fuel carried by aircraft consists of usable fuel and reserved fuel. Useable fuel is provided for completing a particular mission. Reserved fuel is for an emergency.
2 - Question
Total fuel weight of aircraft is ______
a) mission fuel only
b) sum of mission fuel, reserve fuel and trapped fuel
c) sum of trapped and mission fuel
d) reserved fuel only
Explanation: The fuel weight of aircraft is sum of useable mission fuel, reserved fuel and trapped fuel. Mission fuel is the actual useable fuel for the respective mission. Trapped fuel is unusable fuel which has been trapped in supply lines or which cannot be used.
3 - Question
Choose the correct statement based on fuel weight.
a) Fuel required is solely based on mission profile
b) Fuel weight is independent of SFC of engine
c) The required amount of the fuel for mission depends on aerodynamics, SFC, mission itself etc
d) Fuel requirement is not affected by any factors
Explanation: Total aircraft fuel requirement does not solely depend on mission profile. Fuel weight for mission depends on number of factors such as mission profile, aerodynamics, SFC of engine etc.
4 - Question
Is it mandatory for Aircraft to carry reserved fuel?
c) Depends upon the type of aircraft
d) Depends upon manufacture
Explanation: Every aircraft has to carry reserved fuel as an additional weight. Reserved fuel is provided in case of an emergency. During rejected take-off reserved fuel can be used to perform loiter as well.
5 - Question
The typical method for determining fuel weight used is called as _____
a) fuel-fraction method
b) fuel-invert method
c) fuel interpolation
d) fuel fraction mining
Explanation: Fuel- fraction method is a simple method for estimating fuel fraction of the aircraft. It is the most commonly used method due to the simplicity of calculations.
6 - Question
What is the working principle of ‘fuel-fraction’ method?
a) Division of mission profile into number of phases and finding individual phase fuel fraction
b) Division of mission profile into 3 phases only
c) Calculating fuel fraction for each stage
d) Assuming any value for fuel fraction
Explanation: The fuel fraction method is mostly used method for fuel weight fraction. This is very simple method in which we divide whole mission profile into number of mission phases. After that we calculate individual mission segment weight fraction. And based on which we determine approximated fuel weight.
7 - Question
In A/C, we provide reserve fuel for _____
a) loiter maneuver
b) weight reduction
c) to increase weight
d) there is no provision for it
Explanation: Every aircraft has a particular mission profile to follow. Fuel requirement are based on it. In some cases, aircraft need to loiter for more time. If some additional fuel is nor provided then, in such cases aircraft will not be able to perform any additional loiter. Hence, for such cases and also for emergencies we provide reserved fuel.
8 - Question
According to FAA, general aviation aircraft requires reserved fuel in terms of _____
a) additional cruise fuel of half hour
b) additional climb fuel
c) no provision is mentioned in FAA
d) additional taxi-way fuel of three hours
Explanation: For a typical aircraft, it is mandatory to carry reserved fuel. This reserved fuel can be utilized at the time of emergency. According to FAA regulation, for general aviation category we need to provide additional cruise fuel so that it can be used to improve endurance by half hour.
9 - Question
Determine the corrections or otherwise of the following Assertion [A] and reason [R]: Assertion [A]: Total fuel volume of aircraft is divided into mission or used fuel, reserve fuel and trapped fuel. Reason[R]: Depending on type of aircraft, fuel fraction for each category will be different.
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) [A] is true but [R] is false
d) [A] is false but [R] is true
Explanation: The total fuel of aircraft can be seen as sum of mission fuel, reserved fuel and trapped fuel. Each fuel has specific definition. Mission fuel or useable fuel is actual available fuel to complete mission profile. Trapped fuel is that fuel that cannot be used. Fuel fraction for each category will be different for different aircrafts as their mission profile, aerodynamics etc. will be different.
10 - Question
An airliner with take-off gross weight of 2100kg is cruising with fuel weight fraction of 0.280. Then, what will be the weight of fuel (Wf)?
Explanation: Given, Aircraft take-off gross weight W0 = 2100kg, Fuel weight fraction = Wf/W0 = 0.28 Hence, fuel weight Wf = (Wf/W0) * W0 = 0.28*2100 = 588kg.
11 - Question
A prop-driven aircraft having fuel weight of 650kg. Now, aircraft is taxing on runway, after which it has fuel fraction of 0.975. Determine fuel used during taxing of aircraft, if W0 = 5000kg.
Explanation: Given, Aircraft take-off gross weight W0 = 5000kg, Fuel weight fraction after taxi = Wtaxi/W0 = 0.975 Here, there is no provision of reserved fuel is mentioned. So, we are neglecting reserve fuel fraction. Now, from fuel fraction method, Used fuel weight fraction is Wf /W0 = 1 – (Wtaxi/W0) = 1 – 0.975 = 0.025 Hence, fuel used during taxing mission = Wf = W0 * 0.025 = 125kg.
12 - Question
A jet transport aircraft has fuel storage of 1200kg. It has completed taxi phase and preparing for take-off. At the end of the taxing, it has fuel fraction of 0.98. Determine how much fuel is available after taxing. Given take-off gross weight is 9000kg.
Explanation: Given, Aircraft take-off gross weight W0 = 9000kg, Fuel storage = 1200kg Fuel weight fraction after taxi = Wtaxi/W0 = 0.98 Here, there is no provision of reserved fuel is mentioned so, we are neglecting reserve fuel fraction. Now, from fuel fraction method, Used fuel weight fraction is Wf / W0 = 1 – (Wtaxi/W0) = 1 – 0.98 = 0.02 Hence, fuel used during taxing mission = Wf = W0 * 0.02 = 180kg. Now, remaining fuel weight = fuel storage – fuel used during taxi = 1200 – 180 = 1020kg.