May 112011

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In 1947, at the request of the Bureau of Aeronautics (BuAer), Chance Vought Aircraft conducted a comprehensive design study of long range carrier based fighters. The purpose of the study was to determine the airplane performance, size and optimum arrangement with various available power plants, including turbojet, turboprop and reciprocating engines. The effect of reducing the radius requirement from the selected radius of 1,200 nautical miles was also determined as well as the effect of variation in cruising altitude. The results of the study were presented in CVA Report No. 7549, titled “Design Report — Long Range Carrier Based Escort Fighter Design Study.” This study showed that truly long range fighters could be designed for carrier operations at sizes no greater than contemporary carrier types such as the F7F and the AD-1.

Concurrent with this study, Chance Vought was also making very preliminary design studies for carrier based attack or strike airplanes. As the work progressed, the possibility of designing an airplane able to perform both missions was brought under consideration. The desirability of having an airplane which could perform more than one type of mission was obvious. However, there was some doubt whether a satisfactory airplane would result if it were designed initially for more than one type of mission. Experience and history had shown that in every case the airplane which had been designed to be an “all purpose airplane” had been found unsuitable for any purpose. The airplanes which had been able to satisfactorily fulfill more than one type of mission had been developed from a basic highly successful single purpose design by suitable modifications at a later date. Experience seemed to indicate that an airplane which was able to successfully perform a variety of missions had been first an inherently satisfactory design for the fulfillment of its basic mission. Such was the case of the F4U Corsair which was originally designed purely as a fighter, but which had been highly successful not only as a fighter, but as a VBF bomber and rocket attack airplane through subsequent continuing modification and development.

As the study work progressed, the desirability of supplying an advanced airplane to the fleet which would perform the various missions of the Corsair was kept in mind. It was felt that the fleet would probably have a real need for a “work-horse” airplane, if a thoroughly satisfactory one could be supplied. Vought’s desire in this connection was, of course, tempered by their knowledge of the facts mentioned in the previous paragraph, namely that no successful “multi-purpose” airplane had ever been designed as such originally. However, as Vought examined the situation more closely, it became apparent that the basic conditions were quite different from what they had been in the past and that it was possible to provide for two types of missions without significantly compromising the design of the airplane or adversely affecting its potential performance. This was possible in this instance where it had not been in the past, primarily because the fuel quantity required was much greater than was the case several years prior, due to the greater radii of action desired and the higher fuel consumption of more powerful modern engines. Since the outgoing fuel for the long range escort fighter mission was carried externally it could readily be replaced in part or in whole by bombs, with corresponding reduction in radius. Since the external fuel quantity required was so great, a substantial and adequate bomb load could be carried.

As the above general discussion indicates, Vought found it possible to present for consideration an airplane which performed both a long range fighter and a moderate range attack mission without significant compromise in size or performance over an airplane designed purely to perform the long range fighter mission. This airplane, which was designated by Chance Vought as the V-358, was a twin engine airplane powered by Pratt & Whitney PT-2 turboprop engines, as studies had shown that the PT-2 engine offered the optimum compromise between size and performance for the missions considered. The purpose of the proposal was not only to describe and discuss the airplane arrangement, but also to invite comment on the selection of basic characteristics which were subject to choice in arriving at the optimum airplane, as well as on the assumptions made and specification requirements used. Among the choices to be made were the basic radius of action and airplane size, the crew arrangement, and whether the airplane should be designed basically as a VF or as a VA airplane. The effects of the possible choices on the airplane characteristics such as size and performance are discussed below.

Power Plant

There were strict physical limitations imposed on the weight and size of carrier based aircraft by shipboard elevators, hangar deck clearance and general handling requirements aboard ship. Because of these limitations the optimum engine was one which not only provided good high speed performance but also had a minimum weight of engine plus fuel, giving the smallest airplane for a given radius of action. The long range escort fighter study showed quite conclusively that the turboprop engine offered the lowest power plant plus fuel weight for the radii of action under consideration and therefore offered an optimum compromise between the conflicting requirements of fuel economy, take-off and high speed. Other power plants, such as the reciprocating engine and the turbojet, had less suitable characteristics in this connection, either for the attack mission or for the basic long range fighter mission as reference to CVA Report No. 7549 showed. Although an airplane powered by two “hypothetical” turbojet engines in the long range fighter design study appeared to offer attractive performance, it must be emphasized that the power plant data used for this engine was extremely preliminary and undoubtedly quite optimistic within the time span under consideration, and therefore not comparable. The Pratt & Whitney PT-2 turboprop engine was selected as giving the optimum compromise between size and performance of the available turboprop engines that fit the power requirements of a dual purpose attack fighter. The major advantages of the PT-2 engine were its favorable ratio of jet thrust to shaft power, use of single rather than dual rotation propellers, better intake duct configuration than other turboprop engines considered, and the fact that the engine was optimal for a clean, light nacelle installation.

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