The QU-22 was a Beech 36/A36 Bonanza modified during the Vietnam War to be an electronic monitoring signal relay aircraft, developed under the project name “Pave Eagle” for the United States Air Force.
An AiResearch turbocharged, reduction-geared Continental GTSIO-520-G engine was used to reduce its noise signature, much like the later Army-Lockheed YO-3A.
These aircraft were intended to be used as unmanned drones to monitor seismic and acoustic sensors dropped along the Ho Chi Minh Trail in Laos and report troop and supply movements.
When the project was put into operation in 1968, however, the aircraft were all flown by pilots of the 554th Reconnaissance Squadron Detachment 1, call sign “Vampire”.
A separate operation “Compass Flag” monitored the General Directorate of Rear Services along the Ho Chi Minh Trail linking to the 6908th security squadron.
Six YQU-22A prototypes (modifications of the Beech 33 Debonair) were combat-tested in 1968, and two were lost during operations, with a civilian test pilot killed.
Twenty-seven QU-22Bs were modified, 13 in 1969 and 14 in 1970, with six lost in combat.
Two Air Force pilots were killed in action.
All of the losses were due to engine failures or effects of turbulence.
A large cowl bump above the spinner was faired in for an AC current generator, and higher weight set of Baron wings and spars were used to handle the 236-US-gallon (890 l) fuel load.