Propulsive efficiency is defined as _________

A)
aerodynamic efficiency
B)
ratio of obtained thrust power to energy expanded
C)
thrust used by compressed energy
D)
lift required to thrust required at each segment

Correct Answer :   ratio of obtained thrust power to energy expanded

Explanation : Propulsive efficiency is defined as the ratio of obtained thrust power to the energy expanded. Aerodynamic efficiency is defined as lift to drag ratio. Aerodynamic efficiency is primarily consideration of aerodynamic design.

Recently Updated in Aircraft Design Questions
Determine the propeller efficiency if propeller velocity is 300ft/s and thrust of 1320 lb. Given bhp is 800.
A)
0.03%
B)
0.09%
C)
0.895%
D)
90%

Correct Answer : Option (D) :   90%

Explanation : Propeller efficiency = (thrust*velocity) / (bhp*550) = 1320*300/ (550*800) = 0.9 = 0.9*100 % = 90%.

Determine the required thrust coefficient to produce thrust of 1000N. Given diameter is 1.2m and n=22 rps.
A)
0.1
B)
0.32
C)
0.489
D)
0.813

Correct Answer : Option (D) :   0.813

Explanation : Thrust coefficient = Thrust / (density*diameter4*rps2) = 1000 / (1.225*1.24*222) = 0.813.

If a propeller has bhp of 700 and diameter as 1.2 ft. and rotating with 20 rps then, determine power coefficient. Consider sea level density.
A)
1.8
B)
15.8
C)
30.2
D)
40

Correct Answer : Option (B) :   15.8

Explanation : Power coefficient = 550*bhp / (density*diameter5*rps3)
= 550*700 / (1.225*1.25*203) = 15.8.

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