Aircraft Performance Questions and Answers – Range and Endurance for Aircraft with Thrust Producing Engines

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This set of Aircraft Performance Interview Questions and Answers for Experienced people focuses on “Range and Endurance for Aircraft with Thrust Producing Engines”.

1. What is specific fuel consumption?
a) It is the fuel flow rate per unit distance
b) It is the fuel flow rate per unit thrust
c) It is the fuel flow rate per unit time
d) It is the mass flow rate per unit thrust

Explanation: The specific thrust is defined as the fuel flow rate per unit thrust produced by the aircraft. The units of specific thrust are kg/N hr. The expression for specific fuel consumption is given by C=$$\frac{Q_f}{F_N}$$ where Qf is fuel mass flow and FN is thrust produced by the aircraft.

2. There are ___________ fuel flow laws.
a) one
b) two
c) three
d) four

Explanation: There are three fuel flow laws. They are:
i. C=C1, here specific fuel consumption is constant
ii. C=C2θ1/2Mn , here it considers temperature and effects of mach number
iii. C=C3+C4M and C=C5+C6FN, here the assumptions are taken for empirical fuel flow data.

3. What is the significance of first fuel flow law?
a) Specific fuel consumption is not considered
b) Considers temperature and effects of mach number
c) Assumptions are taken for empirical fuel flow data
d) Specific fuel consumption is constant

Explanation: The significance of first fuel flow law is that the specific fuel consumption is constant. The significance of second fuel flow law is that it considers temperature and effects of mach number. The significance of third fuel flow law is that assumptions are taken for empirical fuel flow data.

4. What is the significance of second fuel flow law?
a) specific fuel consumption is not considered
b) considers temperature and effects of mach number
c) assumptions are taken for empirical fuel flow data
d) specific fuel consumption is constant

Explanation: The significance of first fuel flow law is that the specific fuel consumption is constant. The significance of second fuel flow law is that it considers temperature and effects of mach number. The significance of third fuel flow law is that assumptions are taken for empirical fuel flow data.

5. What is the significance of third fuel flow law?
a) Specific fuel consumption is not considered
b) Considers temperature and effects of mach number
c) Assumptions are taken for empirical fuel flow data
d) Specific fuel consumption is constant

Explanation: The significance of first fuel flow law is that the specific fuel consumption is constant. The significance of second fuel flow law is that it considers temperature and effects of mach number. The significance of third fuel flow law is that assumptions are taken for empirical fuel flow data.

6. The second fuel flow law is used in the turbojet or turbofan.
a) True
b) False

Explanation: The significance of first fuel flow law is that the specific fuel consumption is constant. The significance of second fuel flow law is that it considers temperature and effects of mach number. The significance of third fuel flow law is that assumptions are taken for empirical fuel flow data. The second fuel flow law is used in the turbojet or turbofan. Also it takes in account the temperature and effects of mach number.

7. What is meant by fuel ratio?
a) ratio of initial fuel of aircraft to that of final weight of aircraft
b) ratio of final fuel of aircraft to that of initial weight of aircraft
c) ratio of initial weight of aircraft to that of final weight of aircraft
d) ratio of final weight of aircraft to that of initial weight of aircraft

Explanation: The fuel ratio is the ratio of initial weight of aircraft to that of final weight of aircraft. It is denoted by ω. The equation is given by ω=$$\frac{W_i}{W_f}$$ where Wi is initial weight of aircraft and Wf is final weight of aircraft.

8. Which of the following is the correct equation?
a) SAR=$$\frac{C}{V}\frac{L}{D}\frac{1}{W}$$
b) SE=$$\frac{C}{V}\frac{L}{D}\frac{1}{W}$$
c) SAR=$$\frac{V}{C}\frac{L}{D}\frac{1}{W}$$
d) SAR=$$\frac{1}{C}\frac{L}{D}\frac{1}{W}$$

Explanation: The equation for specific air range is given by SAR=$$\frac{V}{C}\frac{L}{D}\frac{1}{W}$$ where V is true airspeed, C is specific fuel consumption, L is lift, W is weight. The significance of first fuel flow law is that the specific fuel consumption is constant.

9. There are two fuel flow laws. They are:
i. C=C1, here specific fuel consumption is constant
ii. C=C3+C4M, here it considers temperature and effects of mach number
a) True
b) False

Explanation: There are three fuel flow laws. They are:
i. C=C1, here specific fuel consumption is constant
ii. C=C2θ1/2Mn , here it considers temperature and effects of mach number
iii. C=C3+C4M and C=C5+C6FN, here the assumptions are taken for empirical fuel flow data.

10. What is the fuel ratio of aircraft when initial and final weight are 385560kg and 15560kg?
a) 34.78
b) 24.78
c) 56.76
d) 45.65

Explanation: The answer is 24.78. Given Wi is 385560kg and Wf is 15560kg. From the formula ω=$$\frac{W_i}{W_f}$$
On substituting the values ω=$$\frac{385560}{15560}$$