Effect On Helicopter Performance Of Modifications In Profile Drag Characteristics Of Rotor Blade Airfoil Sections

Effect on Helicopter Performance of Modifications in Profile-drag Characteristics of Rotor-blade Airfoil Sections

Summary: Performance calculations are presented for a typical helicopter rotor in which three types of airfoil section were successively used. The types represented are the rough conventional, the smooth conventional, and the laminar-flow or low-drag sections as developed for helicopter use. The performance items covered are rotor thrust for fixed power in hovering, range and endurance at cruising speed, and power required at a relatively high forward speed. Contours showing the conditions of operation encountered by the blade section and weighting curves showing the relative importance of the various section angles of attack for specified flight conditions are included as an aid in the interpretation of the results. The calculations indicated that the use of a smooth conventional section will result in marked performance gains throughout the flight range. Definite, though smaller, additional gains in take-off weight and in range and endurance may be realized by the use of a low-drag section. At high forward speeds or at moderate forward speeds and high loadings, however, losses are indicated for the low-drag sections in contrast with the smooth conventional sections. It is demonstrated that, if these losses are to be avoided, the low-drag sections must be designed to avoid the extreme rise in drag coefficient at the higher angles of attack which is characteristic of the low-drag sections now available for use in helicopters.

Considerations of Methods of Improving Helicopter Efficiency

NASA Technical Note