How does humidity affect a helicopter's power required?
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A
Moisture in the air makes it more dense, so less power is required to maintain the same amount of lift, given the reduced drag from the blades lower angles of attack.
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B
Moisture in the air makes it less dense, so more power is required to maintain the same amount of lift and combat the extra drag from the blades greater angles of attack.
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C
Moisture in the air makes it warmer, so less carburretor heat is required, which allows for more fuel in the mixture.
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D
Moisture in the air makes it more dense, so more power is required to get through the extra resistance.
Helicopter's performance in all phases of flight depends on:
- Air density (Temperature, Altitude, Humidity)
- Wind conditions
Water vapour is important because it is invisible, and affects the humidity ratio of the air. Adding water vapour reduces air density because its molecular weight is lower. So, as humidity increases, the air density reduces. This causes the thrust and therefore the power output or performance to decrease at all phases of flight.
As a result, more pitch angle and angle of attack are required to produce the same amount of lift, thus the rotor drag and induced drag increase. Therefore, more power is required to maintain the same amount of lift.
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Pakistan1
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