PURPOSE: To provide a helicopter which can utilize a ram pressure effect effectively at the time of low speed forward flying or hovering.

CONSTITUTION: An engine 2 is installed facing upwards in the longitudinal direction of a fuselage or in the vertical direction of the fuselage and an air inlet 4 for engine is made movable. It is thus possible to utilize a ram pressure effect at the time of low speed forward flying or hovering for improved performance of rising limit and so forth of a helicopter by changing the air inlet direction so as to comply with the flow velocity of air around the air inlet 4 according to forward flying speed and changing the shape of the air inlet 4 according to air turbulence.