History
Following the cancellation of the AH-56 Cheyenne the US Army sought an aircraft to fill an anti-armor attack role. The Army wanted an aircraft better than the AH-1 Cobra in firepower, performance and range. It would have the maneuverability to fly nap-of-the-earth (NoE) missions. On 17 August 1972, the Army initiated the Advanced Attack Helicopter (AAH) program. AAH sought an attack helicopter based on combat experience in Vietnam, with a lower top speed of 145 knots (269 km/h) and twin engines for improved survivability. To this end, the US Army issued a Request For Proposals (RFP) for an Advanced Attack Helicopter (AAH) in 15 November 1972. The AAH requirements for reliability, survivability and life cycle costs were very similar to the UTTAS requirements.
The Army specified that the AAH was to be powered by twin General Electric T700 turboshaft engines that produce 1,500 shp (1,120 kW) each. The T700 was the same powerplant fit specified for a new Army utility helicopter competition that would be won by the UH-60 Black Hawk. The AAH would be armed with a 30 millimeter cannon and 16 TOW anti-tank missiles. The missile armament specification was later modified to include an alternate load of 16 laser-guided AGM-114 Hellfire anti-tank missiles. Hellfire was then in development and promised greater range and lethality than TOW.
Proposals were submitted by five manufacturers: Bell, Boeing-Vertol (teamed with Grumman), Hughes Aircraft, Lockheed, and Sikorsky. In June 1973, Bell and Hughes Aircraft's Toolco Aircraft Division (later Hughes Helicopters) were selected as finalists, and were each awarded contracts for the construction of two prototype aircraft. This began the phase 1 of the competition.
Each company built two prototype helicopters for a flight test program. Bell's Model 409/YAH-63A prototype featured a three-wheel landing gear in a tricycle arrangement, and placed pilot in the front of cockpit instead of the usual rear seat to help with nap of earth flying. Hughes' Model 77/YAH-64A prototype featured a three-wheel landing gear with the third gear at its tail. Its cockpit placed the pilot in the rear seat.
Faced with a flight deadline of the end of September, Hughes' YAH-64 first flew on 30 September 1975, while Bell's YAH-63 first flew on 1 October. The second YAH-64's first flight was on 22 November, and second YAH-63 flew on 21 December 1975. The first YAH-63 crashed in June 1976, but a static test prototype was brought up to flight standard and, along with the second prototype, entered the flyoff against Hughes' YAH-64s.
The Army put all four helicopters through demanding program of flight testing during 1976. The Army flyoff began in June of that year.
A separate competition was conducted for the sensor and targeting suite for the AAH, with Martin Marietta and Northrop submitting proposals in November 1976.
During the prototype evaluation, the Army changed the AAH primary antitank weapon from the proven TOW wire-guided missile to the new Hellfire laser-guided missile, with over twice the effective range. This was risky because Hellfire had not even been flown at the time, with the initial development contract with Rockwell International signed in October 1976.
Read more about this topic: Advanced Attack Helicopter
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