The Bell Model 409/YAH-63 was an experimental attack helicopter for the Advanced Attack Helicopter (AAH) competition. Hughes' Model 77/YAH-64, later developed into the AH-64 Apache, was selected over Bell's entry.
Design and development
During the mid-1960s, United States Army initiated the Advanced Aerial Fire Support System (AAFSS) program to develop the Lockheed AH-56 Cheyenne for the anti-tank gunship role. The U.S. Army pursued the AH-1G HueyCobra as an "interim type" for the "jungle fighting" role. However the Army's broader concern was the task of protecting Western Europe from the legions of Warsaw Pact armor to the east.
In 1972, the Army conducted an evaluation between the Bell Model 309 KingCobra, the Lockheed Cheyenne and Sikorsky S-67 in a competitive fly-off, beginning in the spring of 1972 and was completed in July. In August, somewhat to everyone's shock, the Army rejected all three.
Difficulties delayed the AH-56 Cheyenne development. The Army canceled the Cheyenne program in August 1972. Controversy over the Cheyenne's role in combat, as well as the political climate regarding military acquisition programs, had caused the Army to amend the service's attack helicopter requirements in favor of a simpler and more survivable conventional helicopter.
 Bell 409
The 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. To this end, the U.S. Army issued a request for proposals (RFP) for an Advanced Attack Helicopter (AAH) in 1972.
The Army specified that the AAH was to be powered by twin General Electric T700 turboshaft engines with 1,500 shp (1,120 kW ) each, the same powerplant fit specified for a new Army utility helicopter competition that would be won by the Sikorsky S-70 Black Hawk. The AAH would be armed with a 30 millimeter cannon and sixteen 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.
Bell, Boeing-Vertol (teamed with Grumman), Hughes, Lockheed, and Sikorsky all submitted proposals for the AAH program. In June 1973, Bell and Hughes were selected as finalists, and were each awarded contracts for the construction of two prototype aircraft.
The Bell entry, the Model 409 (YAH-63), was by no means "just another Cobra design", though it leveraged Cobra technology where possible. Although it had what had become by then the typical configuration for a helicopter gunship, with a sharklike fuselage, tandem crew seating, and stub wings for armament, the YAH-63 was largely a new machine.
Distinctive features included wheeled tricycle landing gear; flat canopy window plates; an unusual "tee" tail; a large ventral fin; and a three-barreled GE XM-188 30 millimeter cannon. One less noticeable feature was that the pilot occupied the front seat instead of the back, the reverse of the AH-1's arrangement. This was felt to be more prudent since the YAH-63 was intended to fly "in the treetops", or what is more formally called "nap of earth (NOE)" operations, and the pilot needed to have a clear view of the surroundings. The YAH-63's rotor mast could be lowered and the landing gear could kneel to reduce height for transport.
The first prototype of the YAH-63 (serial 73-22246) made its initial flight on 1 October 1975. This rotorcraft crashed in June 1976, but a static test prototype was brought up to flight standard and, along with the second prototype (73-22247), entered the flyoff against the Hughes entry, the Model 77 (YAH-64).
The YAH-64 was selected in December 1976, and developed into the production AH-64 Apache version. The Army felt the YAH-63's two-blade rotor was more vulnerable to damage than the Apache's four-bladed rotor, and the service did not like the YAH-63's tricycle landing gear scheme, feeling it was less stable than the Apache's "taildragger" configuration. Some observers also suspected the Army did not want to divert Bell from AH-1 production. Bell would use its experience with the T700 engine to develop the AH-1T+ design and later AH-1W equipped with the engine.
* United States : United States Army
 Specifications (YAH-63)
Data from The International Directory of Military Aircraft, 2002-2003
* Crew: 2: one pilot, one CPG (co-pilot/gunner)
* Length: 44 ft 7 in (13.6 m)
* Rotor diameter: 48 ft (14.6 m)
* Height: 13 ft 5 in (4.1 m)
* Disc area: 530.83 ft² (168.1 m²
* Empty weight: 6,600 lb (2,993 kg)
* Max takeoff weight: 14,750 lb (4,500 kg)
* Powerplant: 2× General Electric T700 turboshaft, 1,680 shp (1,300 kW) each
* Maximum speed: 170 knots (210 mph, 338 km/h)
* Range: 317 nmi (365 mi, 587 km)
* Service ceiling: 12,200 ft (3,720 m)
* Rate of climb: 1,620 ft/min (8.2 m/s)
* XM188 Gatling gun 3-barreled 30 mm cannon
* 2.75 mm (70 mm) rockets: 14 rockets mounted in M or M launchers
* TOW Missiles: 4 or 8 missiles mounted in two-missile launchers on each hardpoint