The single XB-29G was modified from B-29B-55-BA, S/N 44-84043. All armament was removed and engine test stations and instrumentation were installed. The bomb bay was used to house prototype jet engines for in-flight testing.
The jet engines were extended into the air stream for testing and retracted for takeoffs and landings. Tested engines included the Allison J35 and General Electric J47 and J73.