Many factors played a role in the demise of the Cheyenne. Monetarily, funding for such an advanced project proved a huge undertaking and worsened by the fact that technologically advanced systems of today were yesterday's relics tomorrow. Originally, it was estimated that each individual Cheyenne would cost tax payers just $500,000 USD. This later ballooned to a projected $5,000,000 USD per unit by project's end. An advanced system like this was also open to many-a-project delay but in many ways this was an accepted part of the program considering its reach - though under McNamara's initiative, there was little room for delay. The US Army used its worry about the main rotor oscillation deficiency to begin distancing itself from the project. They also noted issues with the Cheyenne's performance as a due to rising weights. The US Air Force also tried have the AH-56 cancelled outright when fulfilling the requirements to its A-X Close-Support Program (this eventually producing the fantastic Fairchild A-10 Thunderbolt II). Quite possible throughout the entire project, the US Army was essentially way in over its head in uncharted territory, not knowing how to deal with the political angle of procurement with the Pentagon. For Lockheed's part, their early promises for the AH-56 to the US Army did them no favors in curtailing the level of expectancy for the AH-56 program.
The program in whole was cancelled on August 9th, 1972. Despite this, the US Army continued evaluating the seventh Cheyenne up until March of 1973. Number seven was unceremoniously shipped back to Lockheed on the top of a flatbed semi truck. Only seven of the 11 Cheyenne airframes survived the programs development.
Cheyenne Walk-Around
Externally, the AH-56 held a distinct and unique appearance to anything that had flown before it. The two crewmen were seated in a tandem cockpit arrangement with the pilot in the rear placement and the gunner in the forward placement. Visibility out of the canopy was excellent and supplied plenty of headroom, with views obstructed by only some thin framing on the canopy glass. The fuselage itself was slender in shape and highly contoured to bring out the most aerodynamic qualities of the design - this would, after all, be a fighter lampooning as a helicopter. Side fuselage sponsons contained the main landing gears, allowing for a semi-retraction of each system. To each side sponsons the swept-back wings sporting some dihefral were added. The engine was fitted behind the cockpit and fed by small intakes to either side of the main rotor mast and the single exhaust system facing aft. An additional set of intakes were also set flush along each side of the fuselage. The pilot had the option of which set of intakes to use based on operating conditions. Cable cutters consisted of one dorsal (behind the pilot's cockpit) and one ventral assembly. The Cheyenne was one of the first aircraft to be fitted with an integrated avionics system consisting of a communications, navigation and weapons suite.
The four-bladed main rotor sat low on the design and provided the primary lift source of the aircraft as well as its cyclic control while the flight control system maintained the rotor's pitch. The main rotor was powered by a Kelsey-Hayes transmission system and rotated via the main rotor mast in a counter-clockwise fashion.
The empennage added to the unique appearance of the AH-56, this made up of a straight fuselage extension component containing the drive shaft for the two tail rotors. The anti-torque four-bladed rotor sat on the extreme edge of the horizontal stabilizer (jutting out to the portside) and rotated clockwise with straight blades. The Hamilton-Standard three-bladed "pusher" rotor faced aft and it was this "pusher" propeller system that afforded the Cheyenne its top-flight performance capabilities - no other helicopter system of the time would have matched it. The pusher rotor received power from the main transmission system and was fed via the running shaft in the empennage to a gearbox located in the tail. This rotor system rotated counter-clockwise. Both the anti-torque and the pusher system were driven by the same drive train and gearbox. The pitch of the pusher system was controlled by either crewmember (pilot controls were redundant in both cockpits) through a twist grip located on the collective lever. The Cheyenne held three internal self-sealing fuel tanks of 300-, 78- and 60-gallons.
Cheyenne sported a downward vertical tail fin to which a single-wheeled semi-retractable tail landing gear was affixed. The undercarriage - including tail wheel - were all retractable to an extent with the main landing gears semi-recessed backwards under each side sponson and the tail wheel disappearing into the vertical tail fin. It is interesting to note that the undercarriage was implemented in such a way that, when fully extended with the aircraft at rest, the Cheyenne's posture was essentially level. In contrast, the AH-65 Apache sits with its forward fuselage angled upwards.
The Cheyenne was powered by a single powerplant, this being from a General Electric family of turboshaft engines. One of the earlier engines was a T64-GE-16 originally rated at 3,425 shaft horsepower. This was later increased to 3,925 shaft horsepower with improvements to the gearbox and rotor components allowing for more power and better efficiency. By the time of the ninth prototype Cheyenne, the T64-GE-716 was in use delivering an impressive 4,275 shaft horsepower.
The Cockpits
The gunner was seated in the forward position of the tandem-seat arrangement. His position was dominated by the large pedestal holding the weapons sight and controls. Along with the periscope sight, the pedestal was also home to a right-sided pistol grip. His instrument panel consisted of traditional and conventional dials, tape-style gauges and large map display plotter. To the gunners left was the collective while the cyclic was in a stowed position to his right - this redundancy allowed the gunner to take over piloting duties as necessary. The gunner's seat was integrated into the fire control system - a system that turned his seat horizontally in unison with the direction of the turret. It is interesting to note that early forms of the Cheyenne left this forward cockpit area incomplete as the weapon system had yet to be added. Access to this cockpit was standardized to the starboard side, this via a hinged entry door.
The pilot was afforded a higher position overlooking the gunner's cockpit and the view beyond. In some ways this position was a more "simplified" arrangement in terms of not having the gunner's pedestal system. The a main instrument panel was dotted by various gauges, dials and system readouts. Between the pilots knees were the cyclic control column as well as the map display plotter. Above the map display were the weapon controls. The collective stick was to his left while to his right along the forward panel displayed the Cheyenne's caution light grid. Access to this cockpit was standardized to the starboard side in late Cheyennes, this also via a hinged entry door and in place of the sliding canopy available in early models. In all, the Cheyenne's pilot and gunner were treated to good vision and clean lines from within the cockpit.
The Weapons Suite
As an attack helicopter, the AH-56 shined in terms of her munitions capabilities. The Cheyenne showcased six total hardpoints - two under each wing and an additional two at under-fuselage positions, just inboard of the sponsons. Each wing held an outboard and inboard pylon position to which mission parameters could allow for the mixing and matching of variable weapons loads. The outboard pylons could be fitted with a 450-gallon drop tank or a 2.75-inch FFAR rocket pod (1 x 7-shot or 1 x 19-shot pod) each. The inboard pylons could also make use of a 450-gallon drop tank, a 2.75-inch FFAR rocket pod ( 1 x 19-shot pod) or 3 x TOW anti-tank missiles (for a total of 6 x TOW launchers). The portside under-fuselage hardpoint could carry an additional 300-gallon drop tank but the starboard side could not. The official US Army flight manual also showed that each hardpoint position could singularly carry up to 2,000 pounds in stores. Outboard wing pylons could also make use of a triple adapter rack for carrying up to 3 x 2.75-inch FFAR 19-shot rocket pods per pylon, giving the Cheyenne a more formidable appearance than she already exhibited.
While external munitions were optional and could be mixed and matched as needed, the Cheyenne maintained standard fixed armament as well. The nose could serve as a platform for mounting the XM-129 40mm air-cooled automatic grenade launcher or the XM-196 7.62mm minigun. For the grenade launcher installation, the Cheyenne could carry up to 780 x 40mm anti-personnel grenades and fire them off at a rate of 350 projectiles per minute. If using the minigun armament, the count topped off at 11,750 rounds of 7.62mm ammunition with a maximum rate-of-fire of 6,000 rounds per minute (though this was adjustable by the gunner in 750, 1,500 and 3,000 intervals as well.
Design of the Cheyenne made interesting use of a powered belly-mounted turret system to compliment the nose armament. The weapon fitted to this system was the XM-140 30mm cannon with 2,010 rounds of ammunition and a rate-of-fire up to 450 rounds-per-minute. This powered turret was fitted under the fuselage. As the Cheyenne featured a retractable undercarriage, it made sense to supply the platform with an under-fuselage turret system like this to take full advantage of the available fire arc against ground-based targets. This turret had access to a 200-degree sideways and +26/-60 degrees up/down fire arc meaning that no potential ground target would have been safe from the AH-56.
Conclusion
Despite the loss of the Cheyenne as a viable US Army weapon, the results garnered from the development and testing of its various systems played a major role in the success of the follow-up Hughes AH-64 Apache tank-killing system. In addition, it was reported that many of the Cheyenne's existing issues were solved - or on the verge of being solved - by the time the axe fell on her. Despite her image of a grand Cold War folly, we can still call upon our imaginations as to what a system like the AH-56 could have done on the battlefields with all of the benefits of a helicopter with the performance an airplane. Even today the Cheyenne would have bested its closest rotary-wing rivals on performance alone. One can only imagine adding the AH-64's tank-killing prowess to the AH-56 design.
As American involvement in the Vietnam War dwindled down and many-a-lesson now learned by the US Army, a new competition emerged under the Advanced Attack Helicopter (AAH) name on August 17th, 1972. This gave birth to the YAH-64 by Hughes, eventually to become the AH-64 Apache. Though not a direct descendant of the Cheyenne (nor a replacement for that matter), she no doubt took into account many of the qualities that made the Cheyenne so breath taking a concept -except her top-flight speed that is. The Apache did, however, essentially replace the Bell AH-1 Cobra proving just how cyclical history can be. And the Apache, unlike the Cheyenne, was a helicopter through and through.
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