A piston engine has bhp of 600 at sea level. Now, if engine is operating at an altitude where density ratio is 0.816 then, find the value bhp at that altitude.

A)
37
B)
89
C)
100
D)
289

Correct Answer :   37

Explanation : Given, sea level bhp, p1 = 600, density ratio d = 0.816
Now, bhp at an altitude = p1*(d – ((1-d)/7.55))
= 600*(0.814-((1-0.814)/7.55))
= 600*(0.814-(0.1836/7.55)
= 600*0.0616 = 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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