A subsonic flight has actual inlet pressure recovery of 0.975. Estimate the thrust loss by this subsonic engine.

A)
2.5%
B)
3.37%
C)
11.22%
D)
56%

Correct Answer :   3.37%

Explanation : Given, subsonic Aircraft, actual inlet pressure recovery = 0.975.
Thrust loss can be approximated as follows,
% Thrust loss = C*(reference pressure recovery – actual inlet pressure recovery)*100
Since, C is not given we will consider it as 1.35. 1.35 is a typical value of C for subsonic aircraft.
Hence,
% Thrust loss = 1.35*(1-.975)*100 = 3.37%.

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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