Warbird Digest has received the August/September, 2021 report from Chuck Cravens concerning the restoration of the Dakota Territory Air Museum’s P-47D Thunderbolt 42-27609 at AirCorps Aviation in Bemidji, Minnesota. We thought our readers would be very interested to see how the project has progressed since our last article on this important project. So without further ado, here it goes!
Update
The team focused on some of the more complex skin sections for the control surfaces and wing fillets this month. The electrical system and radios also received their share of attention.
Complex Skin Forming
The P-47 has some unusually formed skin sections that join with a seam which has numerous, curved indentations. Where the skins overlap in those areas, joggles must be formed in the sheet metal so that the skin surface remains smooth.
Wing Fillets
Instruments and Radio
Aaron continues to complete the restoration of the aircraft systems, including the radios and instruments, as the P-47’s completion date gets closer.
Electrical System
A restoration milestone arrived this month; Aaron powered up the Thunderbolt’s electrical system for the first time!
Internal Fuselage Systems
The electrical circuits weren’t the only system to receive attention this month. The fuel system plumbing and the antenna relay were installed in the upper rear fuselage.
Pratt&Whitney R-2800 Double Wasp
Those superlatives are opinions and are open to disagreement, of course, but what isn’t debatable is that a great variety of significant, WWII-era fighters and medium bombers used the R-2800. In fact, the Double Wasp powered more different US aircraft types in WWII than any other engine!
The most well-known types to use this powerplant include the Vought F4U Corsair, Martin B-26 Marauder and PBM Mariner, Grumman F6F Hellcat, F7F Tigercat, F8F Bearcat, Curtiss C-46 Commando, Northrop P-61 Black Widow, Lockheed PV-1 Ventura and PV-2 Harpoon, Douglas A-26 Invader, and, of course, the P-47 Thunderbolt.
A total of 125,334 R-2800 engines were produced between 1939 and 1960, with 114,073 of those completed between 1941 and 1945.2
Production of the big double row radial continued after 1945. The Martin 404, Convair CV 240 and 340, Fairchild C-123 Provider, and the Douglas DC-6 all used the R-2800.
The design for what became the Double Wasp began in 1936. The original concept displaced just 2,600 cubic inches, but upon learning that Wright Aeronautical was developing a double row radial of 2,600 cubic inch displacement, Pratt & Whitney increased their design’s displacement up to 2,804 cubic inches by adding just over 11 cubic inches to each cylinder.
Heat dissipation proved to be one of the major challenges which the engineers had to tackle in making the R-2800, America’s first double-row, 18-cylinder engine, successful. Pratt&Whitney solved the problem by using aluminum cooling muffs with numerous very thin, cooling fins shrunk around the chrome molybdenum cylinder forgings.
A prime example regarding the collective commitment of American industry in supporting the Allied war effort was the fact that so many U.S. companies, including fierce competitors such as Ford, Chevrolet and General Motors, were willing to build R-2800s as subcontractors to Pratt & Whitney.
1 Graham White, Allied Aircraft Piston Engines, Society of Automotive Engineers, Inc, 1995, page 222
2 Graham White, Allied Aircraft Piston Engines, Society of Automotive Engineers, Inc, 1995, page 260
There were more than 40 variants of the R-2800; the version which the P-47D-23RA used was the R-2800-59. Supplied with an improved General Electric C-23 turbosupercharger, the ‘dash 59’ could supply 2,000 hp at takeoff and up to 2,300 hp War Emergency Power in combat, with the use of water injection. Later, C-series variants of the engine (which M and N model P-47s employed) could attain up to 2,500 hp.
During WWII, R-2800s became renowned for surviving damage which would have crippled any other engine. P-47 pilots could come back from missions with their R-2800’s down on power, but still running. It wasn’t until they landed that they found out that one or even two cylinders had been shot out, but the trusty Pratt & Whitney had brought them safely home anyway.
And that’s all for this month. We wish to thank AirCorps Aviation, Chuck Cravens for making this report possible! We look forwards to bringing more restoration reports on progress with this rare machine in the coming months. Be safe, and be well
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