Tuesday, April 22, 2008

McDonnell GAM-72 / ADM-20 Quail

As the Cold War began to develop in the 1950s the US Air Force began to look for new ways to protect their bombers as they overflew the Soviet Union. Height was no longer a defence against the new generation of interceptors and missiles (both ground and air launched). The USAF began to develop decoy missiles that would confuse the enemy air defences. McDonnell pitched a design for a decoy missile that could be carried in a bomber's bomb bay with it's wings folded and then launched when needed. The idea being bombers would carry these decoys along with their weapon load and launch the decoys to confuse enemy air defences. Given more targets it was then hoped that more bombers would be able to penetrate the air defences. In 1956 they were awarded a contract to develop Weapon System 122A of which the GAM-72 Green Quail decoy was a part.

ADM-20 Quail as preserved at the USAF Museum

The GAM-72 Green Quail (later ADM-20 Quail) was a small (for a Cold War aircraft anyway being 3.88m long and having a wingspan of 1.65m) fibre-glass UAV powered by a J85 turbojet. It had a range of 716km and could fly at Mach 0.9.

Pretending to be a B-52

How then could a small drone pretend to be a huge manned bomber? To be effective the Quail had to appear exactly the same as a B-52 would on the enemy's radar. A combination of radar reflectors, chaff, infra-red emitters and electronic repeaters was used to give the Quail as close a signature as possible to the B-52. The design of the Quail with it's slab sides and multiple vertical flying surfaces also contributed to it's radar cross section. (Its kind of ironic that in the days of stealth aircraft here is one that was designed to be exactly the opposite!)

But the Quail not only had to look like a B-52, it had to act like one too. It's performance had to be close or identical to the bomber. The GAM-72 was programmed on the ground before a mission and could fly for up to nearly an hour, changing direction twice in that time and speed also. Later on the GAM-72 was modified to operate at lower altitudes, a barometric altimeter being used to avoid it slamming into the ground. The GAM-72 is an early example of a cruise missile though it never carried a weapon payload.

Service life

In the early 60s the ADM-20 (as it was re designated in 1963) was built in the hundreds. It went fully operational in 1962 and stayed in service until 1978 (it did remain on the USAF books until 1989) though by the early 1970s it was considered obsolete. Improvements in radar technology meant the Quail was no longer considered effective as a decoy. In an exercise in the early 1970s radar operators were able to tell the difference between the Quail and a real target 21 times out of 23. The Commander of Strategic Air Command is said to have written that the Quail was at least better than nothing!

A major reason for the Quail's obsolescence though was the fact that nuclear bombers no longer needed to overfly their targets but could fire "stand off" missiles from some way off. The Quail was, however, the most successful decoy missile fielded by the USAF in the Cold War.

Quail with a B-52 (from Boeing Multimedia Library)

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