Controllable and Automatic Aircraft Propellers 320036
THE DEMAND for a successful controllable or automatic propeller is greater today than ever. Such a propeller will enable commercial aircraft to take off safely with greater loads, and it may enable multi-engine airplanes that cannot now maintain altitude with one engine dead to do so with a safe margin of power. For military aircraft it means increased rate of climb and increased speed at altitude, especially with supercharged engines.
To obviate confusion in nomenclature, the authors give definitions of adjustable, controllable and automatic propellers.
Distinction is drawn between the needs of different classes of airplane for different types of changeable-pitch propellers.
Many propellers falling within the several classes have been designed but few are in use. Cost, weight and complication are obstacles to their commercial success.
Several problems still confront the designer in this field, the chief one being that of obtaining material that is sufficiently light and strong. A number of designs have been worked into full-size propellers.
That interest in this type of equipment is far from dormant is evident from the fact that the Army Air Corps is now following the development of eight distinct types. The authors illustrate and describe a number of such propellers that have been tested by the Materiel Division, one of which was evolved by the Engineering Division and is used by the Air Corps.