A test of a full‐scale four‐bladed helicopter rotor was conducted in the NASA Ames Research Center 40‐ by 80‐Fool Wind Tunnel to investigate performance, acoustics, and loads characteristics of a rotor with various tip planforms. The rotor system employed
four interchangeable tip shapes; rectangular, tapered, swept rectangular and swept tapered planforms over the outer 4.5% radius. The investigation covered an advance ratio range of 0.2 to 0.375 and advancing tip Mach number range of 0.72 up to 0.97. The effect of tip geometry on performance
is shown in terms of respective power characteristics at various lift levels for a range of propulsive farces. On a power basis, the best overall tip geometry was the swept tapered configuration. The effects of tip geometry on control loads are shown primarily on the basis of one‐half
peak‐to‐peak loads. However, at the higher advance ratio. the presence of substantial high‐frequency harmonic loading is noted and found to be significantly influenced by blade tip planform. The swept‐tapered tip was found to lessen control loads for the high advancing
tip Mach number condition. Tip taper and sweep both were found to have a beneficial effect on the acoustic signature, with the swept‐tapered tip being the quietest of the four shapes tested.
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Document Type: Research Article
Ames Research Center, NASA Moffett Field, California
Publication date: 1979-10-01
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