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Posted 3/3/2015 Printable Fact Sheet
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Lockheed EC-121D
DAYTON, Ohio -- Lockheed EC-121D Constellation at the National Museum of the United States Air Force. (U.S. Air Force photo)
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The EC-121, originally designated RC-121, was a radar-picket version of the U.S. Air Force's C-121 passenger airplane. The EC-121 provided early warning by detecting and tracking enemy aircraft with the electronic gear in the large radomes above and below its fuselage.

The Air Force ordered 82 EC-121s between 1951 and 1955, 72 of which were EC-121Ds. The EC-121 entered service with the Air Defense Command in 1953, flying patrols off the U.S. coasts as an aerial extension of the Distant Early Warning (DEW) Line. EC-121s remained in service until they were replaced by more capable E-3 Sentry AWACS (Airborne Warning And Control System). The last EC-121 was retired from the U.S. Air Force Reserve in 1978.

In Southeast Asia, these unarmed radar aircraft aided in downing enemy planes, directed U.S. aircraft to aerial refueling tankers, and guided rescue planes to downed pilots. The aircraft on display was nicknamed Triple Nickel because of its serial number (53-555). On Oct. 24, 1967, over the Gulf of Tonkin, it guided a U.S. fighter into position to destroy a MiG-21. This action marked the first time a weapons controller aboard an airborne radar aircraft had ever directed a successful attack on an enemy plane. Triple Nickel came to the museum in 1971.

Engines: Four Wright R-3350s of 3,400 hp each 
Crew: Varied, but usually 17
Maximum speed: 290 mph
Cruising speed: 240 mph
Range: 4,000 miles
Ceiling: 18,000 ft.
Span: 126 ft. 2 in.
Length: 116 ft. 2 in.
Height: 27 ft.
Weight: 145,000 lbs. 

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