In the 1960s the US Army were growing sick of dependence on inappropriate USAF aircraft for the close support mission. Aircraft like the Republic F-105 Thunderchief were simply too fast and too vulnerable to support troops on the ground effectively. Instead the US Army wanted the versatility and forward-basing possibilities of a vertical take-off platform with the ability to hover. To excel in the tough close support role the type would need to be heavily armed and armoured. This need was expressed formally as the Advanced Aerial Fire Support System or AAFSS.
Convair, a company famed for its adventurous designs, responded to the Army’s AAFSS requirement with typical ambition. Drawing on their experience with the tail-sitting XFY-1 ‘Pogo’ they proposed a two man ‘ring’ (or annular) wing ducted-fan design quite unlike anything else in service, though somewhat similar to the experimental SNECMA C.540 Coléoptère. The concept was bizarre in appearance but Convair believed it was the perfect configuration for an aircraft combining a helicopter’s unusual abilities with some of the offensive features of a military ground vehicle. One of the greatest challenges was creating a cockpit that tilted so the pilot was not facing the sky in the take-off/landing and landed support parts of its mission. This necessitated a complex hinged forward fuselage giving the type its distinctly ‘Transformer’-like looks.
Two co-axially mounted contra-rotated rotors were to be powered by either Pratt & Whitney’s JFTD12 or Lycoming’s LTC4B-11 (GE’s T64 and Allison’s T56 were also assessed as candidates). The duct would generate more thrust from the engine than would the open rotors of a conventional helicopter design, which was a good thing as it was expected to weigh in at around 21,000 Ib (9526kg) fully-loaded.
Armament for this monstrous machine would include a central turret with a XM-140 30-mm automatic cannon with 1,000 rounds or a launcher for 500 (!) WASP rockets and two remotely-controlled light machine-gun turrets with 12,000 rounds of ammunition or a XM-75 grenade launchers with 500 rounds. Addition to this already awe-inspiring arsenal were four hard points on the nacelles which could carry Shellelagh or BGM-71 TOW missiles, or even the M40 ‘106-mm ‘ recoilless gun! The weapons could be fired during any part of the flight profile (note the ‘hover firing’ position). The steel armour would be impervious to 12.7-mm rounds, but there was little or no provision for defences or countermeasures against surface-to-air missiles.
The risky Model 49 lost the AAFSS contest to the remarkable Lockheed AH-56A Cheyenne which was in turn cancelled. The thirty year journey to produce an indigenous fire support aircraft for the US Army eventually led to today’s widely feared AH-64 Apache.