This set of Aircraft Performance Multiple Choice Questions & Answers (MCQs) focuses on “Climb and Descent Performance with Power-Producing Engines”.
1. The propulsive force developed by the engine-propeller combination is given by _______
a) \(\frac{\eta V}{P}\)
b) \(\frac{\eta P}{V}\)
c) \(\frac{P}{V}\)
d) \(\frac{VP}{\eta}\)
View Answer
Explanation: The propulsive force developed by the engine-propeller combination is given by \(\frac{\eta P}{V}\) where η is propeller efficiency, P is power and V is velocity. The equation of power-producing engine is written as \(\frac{\eta P}{V}\)-D=Wsinγ2.
2. The gradient of climb is given by _____________
a) \(\Big[\frac{\eta P}{V}-W\Big]\frac{1}{D}\)=sinγ2
b) \(\Big[\frac{\eta P}{V}+D\Big]\frac{1}{W}\)=sinγ2
c) \(\Big[\frac{\eta P}{V}-D\Big]\frac{1}{W}\)=sinγ2
d) \(\Big[\frac{\eta P}{V}+W\Big]\frac{1}{D}\)=sinγ2
View Answer
Explanation: The gradient of climb is given by \(\Big[\frac{\eta P}{V}-D\Big]\frac{1}{W}\)=sinγ2 where η is propeller efficiency, P is power, V is velocity, D is drag and γ is the angle at which the force is acting on the aircraft. The value of gradient of climb is more when the propulsive force is maximum.
3. The rate of climb is given by _____________
a) [ηP+DV]\(\frac{1}{W}\)=\(\frac{dH}{dt}\)
b) [ηP-DV]\(\frac{1}{W}\)=\(\frac{dH}{dt}\)
c) [ηP+DV]W=\(\frac{dH}{dt}\)
d) [ηP-DV]W=\(\frac{dH}{dt}\)
View Answer
Explanation: The rate of climb is given by [ηP-DV]\(\frac{1}{W}\)=\(\frac{dH}{dt}\) where η is propeller efficiency, P is power, V is velocity, D is drag and W is weight and dH/dt is vertical velocity. The rate of climb is maximum when power speed is minimum.
4. What is the relation between climb rate and power speed?
a) Climb rate increases at minimum power drag
b) Climb rate decreases at minimum power drag
c) Climb rate is independent of minimum power drag
d) Climb rate increases at maximum power drag
View Answer
Explanation: Climb rate is maximum at minimum power drag. The rate of climb is given by [ηP-DV]\(\frac{1}{W}\)=\(\frac{dH}{dt}\) where η is propeller efficiency, P is power, V is velocity, D is drag and W is weight and dH/dt is vertical velocity.
5.The relative airspeed for maximum gradient of climb is a function of engine power.
a) True
b) False
View Answer
Explanation: The relative airspeed for maximum gradient of climb is a function of engine power. The best climb gradient is given by u4+λu-1=0 where u is airspeed and λ is dimensionless power.
6. What is the value of λ in gliding flight flying at minimum drag speed?
a) 3
b) 2
c) 1
d) 0
View Answer
Explanation: In gliding flight the value of dimensionless power (λ) is zero (0) and the shallow glide angle is given by flying at the minimum drag speed. As the power increase the airspeed for maximum climb gradient decreases.
7. What is the relation betweenpower and airspeed for climb gradient?
a) Power increases with increase in airspeed
b) Power decreases with increase in airspeed
c) Power increases with decrease in airspeed
d) Power is unaffected by the airspeed
View Answer
Explanation: The relation between power and airspeed for climb gradient is that the power increases with decrease in airspeed for maximum climb gradient. The best climb gradient is attained by flying at airspeeds less than the minimum power speeds.
8. The best climb gradient is attained by flying at airspeeds less than the minimum power speeds.
a) True
b) False
View Answer
Explanation: The relation between power and airspeed for climb gradient is that the power increases with decrease in airspeed for maximum climb gradient. The best climb gradient is attained by flying at airspeeds less than the minimum power speeds.
9. What is the value that maintains maximum rate and minimum power speed of the aircraft?
a) 1/\(\sqrt[4]{3}\)
b) 1/\(\sqrt[3]{3}\)
c) u2/\(\sqrt[4]{3}\)
d) u2/\(\sqrt[3]{3}\)
View Answer
Explanation: At the maximum rate i.e. dv/du=0 the value of u=1/\(\sqrt[4]{3}\) which is the minimum power speed. The rate of climb is given by λ-\(\frac{1}{2}\)[u3+u-1]=Emaxv where λ is dimensionless power, u is airspeed and Emax is endurance.
10. At what rate does the minimum sink rate occur in a gliding flight?
a) It occurs at minimum power speed
b) It occurs at maximum power speed
c) It occurs at minimum airspeed
d) It occurs at maximum airspeed
View Answer
Explanation: The minimum sink rate occur in a gliding flight at minimum power speed. The rate of climb is given by λ-\(\frac{1}{2}\)[u3+u-1]=Emaxv where λ is dimensionless power, u is airspeed and Emax is endurance.
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