At low subsonic speed, we should select _________

Aeronautical & Aerospace Engineering : Aircraft Design - Quiz(MCQ)

turboprop always

always use ram jet

low bypass Turbofan engine

subsonic speed cannot be achieved

Correct Answer : low bypass Turbofan engine

Explanation : At low subsonic speed, low bypass Turbofan engine should be adopted among the given options. Turboprop has speed limitation due to propeller. Ram jet engine cannot be used at low subsonic speed as ram jet will require assistance to achieve adequate design condition. Ramjet can be used for speeds above Mach 2.8.

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.

0.03%

0.09%

0.895%

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.

0.1

0.32

0.489

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.

1.8

15.8

30.2

Correct Answer : Option (B) : 15.8

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