Blade Stall During Take‐off: The Importance of Airscrew Reduction Gearing and the Effect of Solidity Ratio Available to Purchase

TO facilitate airscrew performance calculations an entirely new series of charts have been developed embodying wider use than hitherto of the term solidity ratio. These charts are applicable to airscrews with any number of blades. Whilst the number of blades is incorporated in the solidity ratio no further inclusion has been made of their tip speed effect on the interference velocity through the actuator disc. This effect has been investigated by Lock in conjunction with tip speed losses, but it was felt that its inclusion did not justify the added complication to the charts. In fact it makes their simple presentation impossible. The effect, however, can be incorporated with a correction factor to the power input to the airscrew. This factor is not dealt with in detail in this article and would form the subject‐matter of a separate work.