Pratt & Whitney R4360

By Pam Mickelson

As you walk into the museum the R4360 could be one of the most impressive sites you'll see.  The engine towers above most displays -- only matching the height of the United 727 cockpit. The R4360 at the museum is on loan from Melvin & Judy Vavra of Elk Point, SD.

The Pratt & Whitney R4360 Wasp Major (as it is known) was a large radial piston aircraft engine designed and built during World War II.  It was the last of the Pratt & Whitney Wasp family and the culmination of its maker's piston engine technology, however, the war was over before it could power airplanes into combat.

The R4360 is a 28-cylinder, 56 spark plug, four-row air-cooled radial engine.  Each row of pistons was slightly offset from the previous, forming a semi-helical arrangement to facilitate efficient airflow cooling inspiring the engine's "corncob" nickname.  Although reliable in flight, the Wasp Major was maintenance-intensive.  Improper starting technique could foul all 56 spark plugs.

The Wasp Major engine was developed near the end of World War II to power the Boeing B-50, an improved version of the successful B-29 Superfortress.  The B-50 had four R4360 engines. 

 The R4360 is an air-cooled radial engine that produces a maximum of 3,500 hp and weighs approximately 3,500 pounds (1,575 kg). R4360s have been used to power various post-WWII USAF bombers, cargo/transports and aerial tankers, including the B-36 bomber, the B-35 Flying Wing, the C-74 Globemaster, the C-97 Stratofreighter, the Consolidated XC-99, the C-119 Flying Boxcar and the C-124 Globemaster II aircraft. The passing of the KC-97 and C-97 series aircraft from Air Force inventory in the late 1970s marked the closing of the era of both the large piston engine and the turbo-supercharger within the USAF.

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