Propeller Selection From Aerodynamic Considerations

A theoretical analysis is preeented of the performance of propellers extending to high values of V)nDo At high values of V~nll the analysis shows the propeller " efficiency to be crltloalIT dependentOn the distribution of the load along the radius.A method of calculating the pitch distributions cf optimum propellers IS explained.Charts aro preeented that faailltate tho melootion of the most efficient propellers ever a wide range of operating oonditionw.It is noted that experimental data in the range of high values of V/nD fcr the purpose of eatab-Ilehing the optimum load distribution are essentially laoklng.~or high-speed airplanem, high vsluee of V/nD are required in order to avoid advert!e compressibility effeatst -Theoretical calculations cf propeller effiolenolea at high values of VlnD for propellers designed to operhte at low values of V/nD agreo with the experimental efflcienctoa obta%nod.Calculations for the came propellers when the pitch distribution was adjusted to give the Goldstoln leadlng along the blade show materially higher eff~oiencles and indicate that a ma~or var~able for the peakoffiolenoy oondlt~on at high values bf V{nD .---