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

View Answer

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 Q

_{f}is fuel mass flow and F

_{N}is thrust produced by the aircraft.

2. There are ___________ fuel flow laws.

a) one

b) two

c) three

d) four

View Answer

Explanation: There are three fuel flow laws. They are:

i. C=C

_{1}, here specific fuel consumption is constant

ii. C=C

_{2}θ

^{1/2}M

^{n}, here it considers temperature and effects of mach number

iii. C=C

_{3}+C

_{4}M and C=C

_{5}+C

_{6}F

_{N}, 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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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 W

_{i}is initial weight of aircraft and W

_{f}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=\(\frac{1}{C}\frac{L}{D}\frac{1}{W}\)

View Answer

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=C_{1}, here specific fuel consumption is constant

ii. C=C_{3}+C_{4}M, here it considers temperature and effects of mach number

a) True

b) False

View Answer

Explanation: There are three fuel flow laws. They are:

i. C=C

_{1}, here specific fuel consumption is constant

ii. C=C

_{2}θ

^{1/2}M

^{n}, here it considers temperature and effects of mach number

iii. C=C

_{3}+C

_{4}M and C=C

_{5}+C

_{6}F

_{N}, 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

View Answer

Explanation: The answer is 24.78. Given W

_{i}is 385560kg and W

_{f}is 15560kg. From the formula ω=\(\frac{W_i}{W_f}\)

On substituting the values ω=\(\frac{385560}{15560}\)

ω=24.78.

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