THIS paper presents the results of coordinated research by The Pratt & Whitney Aircraft Co. (engines), the Chance Vought Corp. (airplanes), and the U.A.T. Research Division, all subsidiaries of the United Aircraft & Transport Corp. These studies were directed toward improving the performance of airplanes through reducing the drag of radial air-cooled powerplant installations as nearly as possible to the minimum necessary for adequate cooling.
The studies were supported by a considerable amount of experimental data. Extensive wind-tunnel tests provided quantitative measurements of airflow and drag for many combinations of baffles and cowling, and throughout the whole work simultaneous flight-tests checked results and contributed to the final conclusions. The successive stages of baffle development, as well as the experiments with various sizes and shapes of cowling, are discussed. The optimum combination ultimately found is described in detail.
The results of the studies show that much can be done to improve the arrangements now in general use. The use of the best type of baffle developed during the study, together with cowling designed in accordance with limitations determined during the course of the research, showed marked improvement in both aerodynamic performance and cooling over those of conventional arrangements, as is evident from the data and discussion presented.
The paper also points out the desirability of controlled cooling to compensate for variations in temperature and operating conditions, comparable to the use of a retractable radiator. The development of an entirely new type of adjustable cowl which successfully accomplishes this important objective is explained. Finally, mention is made of a few of the more important changes in powerplant installation which are made desirable by the use of the new baffling and cowling system.