Compound helicopter

A compound helicopter comprising:

• a body;
• a first main wing extending from the body toward a right side in a proceeding direction of the body;
• a second main wing extending from the body toward a left side in the proceeding direction of the body;
• a main rotor disposed at an upper side of the body;
• a first propeller that is disposed at the first main wing and generates positive thrust when the proceeding direction is regarded as positive, and the first propeller can also generate negative thrust;
• and
• a second propeller that is disposed at the second main wing and generates positive thrust and negative thrust, wherein
• specifications of the first propeller are different from specifications of the second propeller, wherein:
• the first propeller includes a first propeller blade that is a propeller blade whose rotation axis extends in a direction parallel to an aircraft axis direction;
• the second propeller includes a second propeller blade that is a propeller blade whose rotation axis extends in a direction parallel to the aircraft axis direction;
• the first propeller blade includes a washout angle corresponding to a change in an angle of attack from a base end of the first propeller blade to a tip thereof;
• the second propeller blade includes a washout angle corresponding to a change in an angle of attack from a base end of the second propeller blade to a tip thereof;
• and
• the washout angle of the second propeller blade is smaller than the washout angle of the first propeller blade;
• a lower limit of the washout angle of the second propeller blade is a value at which a sum of required horsepower of rotating the first propeller blade to generate thrust for forward flight and required horsepower of rotating the second propeller blade to generate thrust for the forward flight coincides with a propeller horsepower upper limit;
• and
• an upper limit of the washout angle of the second propeller blade is a value at which a sum of required horsepower of rotating the first propeller blade to generate thrust for hovering and required horsepower of rotating the second propeller blade to generate thrust for the hovering coincides with the propeller horsepower upper limit.