NEARLY all the aircraft propellers used by both the Army and the Navy are of the detachable-blade type. The Navy has found it necessary to make its own designs and to furnish the propeller manufacturers with finished detail drawings. The author lists the sources from which data can be obtained and shows a chart from which can be found a diameter and setting of a pair of detachable blades that will give reasonably good performance for nearly any horsepower, revolutions per minute and airspeed commonly used with the direct-drive type of propeller.
Discrepancies between model tests and wind-tunnel tests are cited, and the author then considers the subject theoretically. Substitute propellers are next considered, and also the strength of propellers. The author gives empirical formulas for maximum fiber-stress and explanations of them, describes the whirl-test for strength, discusses the necessity for the use of gearing, and enumerates the considerations that apply to variable-pitch propellers.