Figure 1 - Republic P-47D-40 Thunderbolt During World War II, the United Ending Harry Tope of Mt. Pleasant, Michigan. States introduced four new fighter de- signs produced by four separate man- TEST AIRCRAFT ufacturers: the Republic P-47 Thunder- bolt, the Vought F4U/FG-1D Corsair, the Republic P-47D-40 Thunderbolt the Grumman F6F Hellcat, and the The aircraft is shown in Figure 1. Se- North American P-51 Mustang. rial number 45-49181. Powered by Pratt These fighter designs introduced in & Whitney R-2800-59 engine with Cur- the early 1940s have become legen- Argument tiss Electric four-bladed, constant dary. Many Army Air Corps, Navy and speed propeller. The aircraft and induc- Marine pilots became aces at their con- tion system had been modified by re- trols. Much has been written, and even By John M. Ellis III moval of the exhaust-driven tur- more said, concerning the exploits of Kal-Aero, Inc. bocharger with engine exhaust being these famous aircraft. Today, more than 5605 Portage Rd. routed through the former wastegate. 45 years since these aircraft entered Kalamazoo Municipal Airport The 100 gallon auxiliary fuel tank had combat squadrons, the facts and myths Kalamazoo, Ml 49002 been disconnected and only the main of their capabilities are blurred together fuel tank, 270 gallons, was usable. The as memories fade and the few remain- and test aircraft was equipped with one ing examples of these former warriors stores pylon mounted under each wing. are preserved by museums and avia- Christopher A. Wheal It is one of five P-47s believed to be in tion enthusiasts. Flight time on these Veda, Inc. flyable condition in the United States. aircraft is usually limited to public air 300 Exploration show exhibitions and, in deference to Lexington Park, MD 20653 Goodyear FG-1D Corsair the aging airframes and scarcity of en- The aircraft is shown in Figure 2. gines and parts (not to mention their Bureau number 92509. Powered by cost), they are normally operated well Photos Courtesy Kalamazoo Aviation Pratt & Whitney R-2800-8 engine with within their original design limits. History Museum and Harry Tope Hamilton Standard Hydromatic three- "Ending the Argument" documents bladed, constant speed propeller. With the results of a limited flight test pro- tually raised more questions than it the exception of modern communica- gram which was designed to compare, answered. tion and navigation equipment, the air- as far as possible on equal footing, the The P-47D Thunderbolt, FG-1D Cor- craft is unmodified from its original man- performance and flying qualities of sair and the F6F-5 Hellcat used in the ufactured condition. The Corsair also these four historic World War II fighter program were borrowed from the had one stores pylon under each wing. aircraft. Unfortunately, the title we Kalamazoo Aviation History Museum, It is one of approximately 25 Corsairs chose for the paper turned out to be the "Air Zoo", of Kalamazoo, Michigan. of different models which exist in flyable rather ambitious as the test program ac- The P-51D Mustang was on loan from condition in the United States. SPORT AVIATION 47 Grumman F6F-5 Hellcat Rolls Royce V-1650-9 Merlin engine at approximately 2,000 BHP. The varied The aircraft is shown in Figure 3. with Hamilton Standard Hydromatic dash numbers refer to minor differences Bureau number 79683. Powered by four-bladed, constant speed propel- such as accessory position and car- Pratt & Whitney R-2800-10 engine with ler. Major modifications include the re- buretor type. The Merlin engine in the moval of a 65 gallon fuel tank located Hamilton Standard Hydromatic three- P-51 was rated 1490 BHP. bladed, constant speed propeller. With behind the cockpit and installation of a the exception of modem communica- passenger jumpseat. Modern com- MISSION BACKGROUND tion and navigation equipment, the air- munication and navigation equipment Although all designed as fighters, craft is unmodified from its original man- had been fitted as with the other aircraft there were in fact considerable differ- ufactured condition. It is one of five in the test program. Approximately 125 ences in the ways the four aircraft were Hellcats in flyable condition known to flyable P-51 aircraft are believed to employed in combat. In addition, follow- exist. exist. ing a trend which has persisted to this day, they were all sooner or later used North American P-51D Mustang ENGINE PERFORMANCE in the air-to-ground role, though to The aircraft is shown in Figure 4. Se- The R-1800 engines in the test air- greatly different extents. rial number 45-11586. Powered by craft were virtually identical and all rated The two Army Air Corps fighters, the Figure 5 - Engine Cooling Switches 48 JUNE 1990 Figure 6 - FG-1D Wing Lock P-47 and P-51, are best known as long continuous settings. Superchargers nose. In addition, sitting above or be- range bomber escorts. While their final were limited to "low blower" ranges hind a large straight wing creates a combat scenarios would have been which restricted the investigation to al- further blind area in a direction which practically indistinguishable from those titudes between the surface and 10,000 could well be critical in combat with the of the F6F and FG-1D (apart from the ft. MSL. Unfortunately, this limitation opposition coming up to meet you from opposition being Me. 109s and FW precluded an evaluation of the aircraft below. Rather than describe every fault 190s rather than Kates and Zeroes), an at typical "bomber escort" altitudes. All in detail, we shall pick out some of the important distinction lies in the fact that of the aircraft had permissible CG best and worst features. by the time battle was joined, the Thun- ranges of five and one half to eight in- P-47 - The massive size of the P-47 derbolt and Mustang pilots had already ches. The P-47 was tested at a CG is misleading. In fact, it had the most been in the air for several hours. Thus range very close to the forward limit, cramped and uncomfortable cockpit of the levels of noise, vibration and com- the F6F at one third aft, the P-51 at all four aircraft. The rudder pedals were fort in the cockpit environment, while exactly mid CG and the FG-1D at three adjustable for reach and the seat for never unimportant, assumed particular quarters aft. height (as were all the aircraft), but the significance in ensuring that the pilot ar- maximum available seat back to pedal rived comparatively fresh and ready for distance was only 41 inches which cor- the fight. A tired and cramped pilot COCKPIT EVALUATION responds to a 20th percentile leg length. whose head is buzzing from a noisy en- The cockpits were all essentially typ- Longer legged pilots were condemned gine is not likely to fight as effectively ical of 1940's vintage tailwheel aircraft, to suffer without thigh support, which as one who has spent the previous which is to say they had some major was uncomfortable enough during three hours or so in a comfortable seat ergonomic shortcomings. Important these short duration test flights and in a quiet cockpit. These considerations controls were often positioned with little would certainly have been hard to en- must be put in the context of the primi- regard to whether the pilot could see, dure on a long range bomber escort tive radios and indifferent sound attenu- reach or operate them without consider- mission. The tops of the pedals could ation qualities of 1940s helmets. able effort. Each of the aircraft posses- be folded down to allow the pilot to put sed fields of view which on the ground his feet on them but even that brought were limited chiefly by the precise ex- scant relief. TEST ENVELOPE AND LIMITATION tent of the area ahead blocked by the The control switches for the oil cooler Recognizing the age of the aircraft in engine and forward fuselage. The need flaps, intercooler flaps and canopy were the test program, it was agreed that for constant S-turns to avoid hitting clustered under the canopy rail at the structural loads would not exceed 6g. things while taxiing was part of the pilot's left shoulder (Figure 5), almost Military power was permitted for takeoff charm of flying these aircraft. In all impossible to see and very hard to iden- and climb to 10,000 ft. MSL consistent cases the field of view improved consid- tify.The cooler control switches in par- with manifold pressure limitations ap- erably from the moment the tail was ticular were arranged one on top of the propriate for operating on 100LL fuel. raised during the takeoff roll; but even other, operated in the same sense, and The non-availability of higher octane in flight the forward fuselage and engine were difficult to tell apart by feel. Inad- fuel reduced the maximum allowable continued to present a serious obstruc- vertently operating the canopy switch in manifold pressure by approximately tion to forward and downward vision flight would be immediately obvious but four inches for the three aircraft pow- and must have caused considerable dif- operating the wrong cooler switch ered by Pratt & Whitney R-2800 en- ficulties in shooting at large deflection would not and, if followed by a hectic gines. The Rolls Royce Merlin 1650 in angles or in air-to-ground aiming with a period at high power, could lead to en- the P-51 D was unaffected. For all other depressed sight-line when the target gine damage before being detected.