This set of Aircraft Performance Multiple Choice Questions & Answers (MCQs) focuses on “Climb and Descent Performance with Thrust-Producing Engines”.

1. Which of the following is the correct thrust balancing equation for thrust producing engines?

a) F_{N}+D=Wsinγ_{2}+mV̇

b) F_{N}-D=Wsinγ_{2}+mV̇

c) F_{N}-D=Wsinγ_{2}-mV̇

d) F_{N}+D=Wsinγ_{2}-mV̇

View Answer

Explanation: The correct thrust balancing equation for thrust producing engines is given by the equation F

_{N}-D=Wsinγ

_{2}+mV̇ where F

_{N}is the normal force acting on the aircraft, γ is the angle at which the force is acting on the aircraft, D is drag produced, W is weight of the aircraft, m is mass and V̇ is velocity.

2. Which of the following is the correct lift balancing equation for thrust producing engines?

a) L=Wcosγ_{2}

b) L=Wsinγ_{2}

c) L=\(\frac{cos\gamma _2}{W}\)

d) L=\(\frac{sin\gamma_2}{W}\)

View Answer

Explanation: The correct lift balancing equation for thrust producing engines is given by the equation L=Wcosγ

_{2}where L is lift, W is weight and γ is the angle at which the force is acting on the aircraft.

3. What should be the value of thrust- to-weight ratio for a normal take-off so that the acceleration associated with the rate of climb is neglected?

a) 0.1

b) 0.2

c) 0.3

d) 0.4

View Answer

Explanation: 0.3 must be the value of thrust- to-weight ratio for a normal take-off so that the acceleration associated with the rate of climb is neglected. This way the climb can be assumed with constant airspeed and mach number.

4. The best gradient of climb is attained at the time of maximum drag speed of the aircraft.

a) True

b) False

View Answer

Explanation: The best gradient of climb is attained at the time of minimum drag speed of the aircraft. The best gradient of climb is attained generally at the airspeed ‘u’ of 1. The gradient of climb is given by E

_{max}sinγ

_{2}=τ-\(\frac{1}{2}\)[u

^{2}+u

^{-2}].

5. The best rate of climb occurs when the excess thrust power is minimum than drag power.

a) True

b) False

View Answer

Explanation: The best rate of climb occurs when the excess thrust power (F

_{N}V) is maximum than the drag power (DV). As the ideal power increases linearly with true airspeed the best gradient of climb is predicted to be at an airspeed greater than minimum drag speed.

6. The best gradient of climb is predicted to be at an airspeed greater than minimum drag speed.

a) True

b) False

View Answer

Explanation: The best rate of climb occurs when the excess thrust power (F

_{N}V) is maximum than the drag power (DV). As the ideal power increases linearly with true airspeed the best gradient of climb is predicted to be at an airspeed greater than minimum drag speed.

7. What is the relation between thrust power and true airspeed?

a) Thrust power increases with increase in true airspeed

b) Thrust power decreases with increase in true airspeed

c) Thrust power increases with decrease in true airspeed

d) Thrust power is independent of true airspeed

View Answer

Explanation: Thrust power increases with increase in true airspeed.The best rate of climb occurs when the excess thrust power (F

_{N}V) is maximum than the drag power (DV). As the ideal power increases linearly with true airspeed the best gradient of climb is predicted to be at an airspeed greater than minimum drag speed.

8. In which of the following the maximum rate of climb occurs?

a) It occurs when difference in thrust power and drag power is minimum

b) It occurs when difference in thrust power and drag power is maximum

c) It occurs when difference in thrust power is minimum

d) It occurs when difference in drag power is minimum

View Answer

Explanation: The maximum rate of climb occurs when the difference in thrust power and drag power is maximum. The rate of climb is a function of excess thrust power.The best rate of climb occurs when the excess thrust power (F

_{N}V) is maximum than the drag power (DV).

9. Which of the following is the correct climb gradient equation?

a) τ-\(\frac{1}{2}\)[u^{2}+u^{-2}]=E_{max}sinγ_{2}

b) τ+\(\frac{1}{2}\)[u^{2}+u^{-2}]=E_{max}sinγ_{2}

c) τ+\(\frac{1}{2}\)[u^{2}+u^{-2}]=E_{max}

d) τ-\(\frac{1}{2}\)[u^{2}+u^{-2}]=E_{max}

View Answer

Explanation: The correct climb gradient equation is given by the equation τ-\(\frac{1}{2}\)[u

^{2}+u

^{-2}]=E

_{max}sinγ

_{2}where τ is dimensionless thrust, u is airspeed, E

_{max}is endurance and γ is the angle at which the force is acting on the aircraft.

10. At what airspeed does maximum gradient of climb occurs?

a) 1

b) 2

c) 3

d) 4

View Answer

Explanation: The maximum gradient of climb occurs at airspeed (u) =1. There occurs negative values for sinγ

_{2}of τ and u when the flight is descending. The climb gradient equation is given by the equation τ-\(\frac{1}{2}\)[u

^{2}+u

^{-2}]=E

_{max}sinγ

_{2}.

11. Which of the following is the correct rate of climb equation?

a) τu-\(\frac{1}{2}\)[u^{3}+u^{-1}]=E_{max}v

b) τ-\(\frac{1}{2}\)[u^{2}+u^{-2}]=E_{max}sinγ_{2}

c) τ+\(\frac{1}{2}\)[u^{2}+u^{-2}]=E_{max}sinγ_{2}

d) τu-\(\frac{1}{2}\)[u^{3}+u^{-1}]=E_{max}v

View Answer

Explanation: The correct rate of climb equation is given by τu-\(\frac{1}{2}\)[u

^{3}+u

^{-1}]=E

_{max}v where τ is dimensionless thrust, u is airspeed, E

_{max}is endurance and γ is the angle at which the force is acting on the aircraft.

12. What is the correct formula for dimensionless rate of climb?

a) ν=\(\frac{dH/dt}{V_{md}}\)

b) v=\(\frac{V_{md}}{dH/dt}\)

c) v=\(\frac{-V_{md}}{dH/dt}\)

d) v=\(\frac{-dH/dt}{V_{md}}\)

View Answer

Explanation: The correct formula for dimensionless rate of climb is given by the formula v=\(\frac{dH/dt}{V_{md}}\) where v the dimensionless rate of climb is and dH/dt is vertical velocity and V

_{md}is velocity. The vertical velocity dH/dt is given in feet/min.

13. The minimum sink rate is attained by flying at a relative airspeed of u/\(\sqrt[4]{3}\).

a) True

b) False

View Answer

Explanation: The minimum sink rate is attained by flying at a relative airspeed of u/\(\sqrt[4]{3}\). At this airspeed the minimum power speed of aircraft is attained. Flying at this speed will maximize the time of gliding flight.

14. What is the benefit of flying at minimum power speed?

a) Increases gliding flight time

b) Decreases gliding flight time

c) Does not change the gliding flight time

d) Decreases the aircraft performance

View Answer

Explanation: The benefit of flying at minimum power speed is increase in gliding flight time. The minimum sink rate is attained by flying at a relative airspeed of u/\(\sqrt[4]{3}\). At this airspeed the minimum power speed of aircraft is attained. Flying at this speed will maximize the time of gliding flight.

15. What is the value that maintains minimum power speed of the aircraft?

a) u/\(\sqrt[4]{3}\)

b) u/\(\sqrt[3]{3}\)

c) u^{2}/\(\sqrt[4]{3}\)

d) u^{2}/\(\sqrt[3]{3}\)

View Answer

Explanation: The minimum sink rate is attained by flying at a relative airspeed of u/\(\sqrt[4]{3}\). At this airspeed the minimum power speed of aircraft is attained. Flying at this speed will maximize the time of gliding flight.

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