Did you know the JT9D engine's problems were tested by…

Did you know the JT9D engine's problems were tested by mounting it on a B-52?

Short answer

The B-52E was the flying test bed on which the JT9D made its first flight, in June 1968. The problems, however, showed up in the 747's flight trials: engine stalls from abrupt throttle movements and turbine casing distortion.

Published: November 4, 2026 · Updated: November 4, 2026 · Edited by Above Ten Thousand · Editorial policy

Did you know the JT9D engine's problems were tested by mounting it on a B-52?

Lufthansa Boeing 747-400 departing BostonFoto: 4300streetcar (CC BY 4.0)

A B-52E as a flying test bed

The JT9D program began in September 1965, and the first engine was tested in December 1966. The first test was run on a stand in East Hartford, Connecticut, and the engine's first flight came in June 1968, mounted on a Boeing B-52E that served as a flying test bed. The JT9D-3, the first certified version of the engine, weighed 8,470 lb (3,840 kg) and produced 43,500 lbf (193 kN) of thrust.

The problems in the 747's trials

The 747's flight test program was hampered by problems with its JT9D engines. Among the difficulties were engine stalls caused by abrupt throttle movements and turbine casing distortion after little time in service. These problems delayed 747 deliveries by several months: up to 20 aircraft sat idle at the Everett plant awaiting engine installation.

Certification and commercial career

The JT9D was the first high-bypass engine to power a wide-body commercial aircraft. It received FAA certification in May 1969 and entered service in January 1970 on the Boeing 747. Production ceased in 1990, replaced by the new PW4000.