The Effect of Solidity on Propeller Normal Force

Propeller normal force is a major contributor to pitch and yaw stability on propeller driven aircraft. While it is well-known that propeller normal force is a function of the number of blades, there are no published data for the high numbers of blades that are used in the new designs such as the GE UDF and Pratt-Whitney-Allison 578-DX.

This paper presents the results of a test conducted in the NASA Langley 14- by 22-Foot Subsonic Tunnel using a sting-mounted counterrotation propeller and nacelle. The configurations tested were combinations of 0, 4, and 8 blades per hub. Tests were conducted for blade angle settings of 31.34°, 36.34°, and 41.34° over an angle-of-attack range from −10° to 90° and over a range of advance ratios from .8 to 1.4. The results show that propeller normal force varies with both solidity and angle of attack.