“Unlocking the Untold Legacy: The AH-56 Cheyenne, a Trailblazer of Attack Helicopters with Futuristic Innovation and Impact on Military Aviation History!”
Step back in time to witness the rise of the world’s most advanced attack helicopter, the Lockheed AH-56 Cheyenne, which dazzled with revolutionary features ahead of its era. Despite its untimely fate, this groundbreaking marvel influenced close air support and attack helicopter design, securing a special place in military aviation history.
Among its captivating features was an awe-inspiring gunner’s seat that swiveled a full 360 degrees, reminiscent of thrilling Star Wars space battles. Over half a century later, its legacy lives on, forever etched into the annals of innovation.
Unfolding against the backdrop of the Vietnam War, the Cheyenne was born out of a pressing need for a U.S. Army attack helicopter. Witness how its journey intertwines with the legendary Bell UH-1 Iroquois, better known as “Hueys,” and the ingenious improvisation of weapon systems on the battlefield.
Embark on a remarkable journey through history, where ambition and technological brilliance collide, paving the way for a new era of aerial combat prowess. Join us as we delve into the legacy of the Cheyenne program, where its influence continues to soar, resonating through the corridors of military strategy and innovation.
In response to the escalating Vietnam War and the evident requirement for a well-armed multi-mission attack helicopter, the U.S. Army initiated the Advanced Aerial Fire Support System (AAFSS) in 1964 to develop and procure a new attack helicopter. In 1965, Lockheed emerged as the winner of the AAFSS program contract, leading to the order of 10 prototypes of their proposed attack helicopter. The Army designated this helicopter as the AH-56A, affectionately named the Cheyenne.
Setting itself apart from other helicopters of its time, the Cheyenne showcased exceptional aerodynamic features. Powered by an almost 4,000-horsepower turbine engine and equipped with a pusher propeller on the tail boom, it achieved a remarkable 224-mile-per-hour cruise speed and could dash at an impressive 240 miles per hour. Its 26.7-foot fixed wings, in conjunction with the pusher propeller, effectively relieved much of the aerodynamic load from its rigid main rotor. This unique thrust mechanism allowed the Cheyenne to accelerate and decelerate rapidly, without requiring nose-up or nose-down pitching, unlike standard helicopters. Additionally, the Cheyenne displayed the capability to pitch its nose up or down while hovering, without any forward or backward motion.
According to Bob Mitchell, the curator of the U.S. Army Aviation Museum, the Cheyenne’s combination of aerodynamic features provided it with a crucial advantage over other attack helicopters of its time. In a 2018 interview for an official Army story on the AH-56, Mitchell emphasized that during gunship operations, particularly when executing diving fire, speed built up rapidly, leaving only a few seconds to acquire, engage, and initiate recovery. However, the Cheyenne offered a distinctive solution – the pilot could enter the dive and then utilize reverse thrust on the pusher to significantly slow down the aircraft, allowing precise targeting, firing, and a prompt recovery. Mitchell described this capability as making it a “beautiful gunship.”
The Cheyenne’s ability to distribute fire during its attack runs extended even further than that.
The Cheyenne featured a two-seat tandem cockpit arrangement, positioning the pilot at the rear and equipping the front seat with an advanced fire control suite for the gunner. Undoubtedly, one of the most remarkable aspects of the Cheyenne was its ingenious gunner’s seat and control station.
Resembling the gun turrets found on World War II bombers and akin to the swiveling gunner seats seen in the Millennium Falcon from Star Wars, the Cheyenne’s gunner’s seat, sighting system, and firing controls boasted a complete 360-degree rotation capability. This extraordinary design allowed the gunner to align himself with the direction of fire, even enabling him to face entirely to the rear when necessary.
With the assistance of a periscope sight, the gunner could precisely aim the 30mm XM140 cannon housed in the belly turret, granting the helicopter a remarkable 360-degree direct fire capability. This groundbreaking feature significantly broadened the scope of potential attack runs for a helicopter of its time, thus enhancing the overall tactical flexibility of the aircraft.
Equipped with a cutting-edge helmet-mounted display (HMD), the pilot could autonomously aim the helicopter’s nose-mounted turret, heralding a remarkable technological advancement. This forward turret had the versatility to house either a 7.62mm Minigun or a 40mm M129 grenade launcher.
Apart from the turrets, the Cheyenne boasted six hardpoints on its stub wings, offering the capability to mount pods loaded with 2.75-inch rockets, wire-guided BGM-71 TOW antitank missiles, external fuel tanks, and various other stores. The fire control system of the Cheyenne incorporated cutting-edge technology, including doppler radar and a laser range finder, which were considered highly advanced for their era.
The Cheyenne’s avionics systems encompassed numerous groundbreaking elements. With an automatic flight control system and multiple radar systems, all linked to an advanced digital “Computer Central Complex” (CCC), the AH-56 achieved secure operations at low altitudes. At the core of this technological prowess was the Cheyenne’s AN/APQ-118 terrain-following radar system, crafted by Norden, which offered both manual terrain-following (MTF) and automatic terrain-following (ATF) modes for optimal performance.
According to a 1971 study of the Cheyenne’s radar system published in the Journal of the American Helicopter Society, the computing suite in the AH-56 combined what were then cutting-edge avionics, including a forward-looking radar (terrain-following radar, or TFR), an automatic flight control system (AFCS), a vertical situation display (VSD), and a plan position display (PPD), enabling “safe, low altitude penetration of territories under IFR and night conditions.” Other sensor capabilities, including infrared and electronic support measures, as well as datalink systems, could help the unique helicopter act in an advanced scout and forward fire support director role.
In 1967, the Cheyenne embarked on its flight testing phase, which included a remarkable demonstration at Van Nuys Airport. Spectators were in awe as the Cheyenne showcased its ability to “bow” to the crowd by lowering its nose while hovering in place. The testing journey continued until March 1969, when an unexpected rotor vibration occurred during a flight test of the third Cheyenne prototype. Tragically, the vibrations caused the rotor to collide with the aircraft’s canopy and tail boom, resulting in the instant loss of pilot David A. Beil.
In the aftermath of this devastating crash, the Army promptly issued Lockheed a Cure Notice, signifying that the contractor had failed to meet its requirements. Two months later, the service terminated its Cheyenne production contract with Lockheed.
After languishing in bureaucratic purgatory for several years, the Cheyenne program faced its official cancellation by the Army in 1972. Shortly thereafter, the Army initiated the Advanced Attack Helicopter (AAH) program, which ultimately led to the development of the AH-64 Apache.
As mentioned earlier, the AH-56’s cancellation had multiple reasons. However, according to the “Abridged History of Army Attack Helicopter Program” prepared by the Office of the Assistant Vice Chief of Staff of the Army (OAVCSA), program management issues rather than inherent flaws in the helicopter itself were also significant contributors. One particular concern was Lockheed’s perceived lack of “adequate helicopter experience.” Although Lockheed did not pursue further helicopter development, the modern-day Lockheed Martin Corporation now engages in helicopter development through its subsidiary, Sikorsky.
Moreover, the Cheyenne faced challenges due to its transitional period between analog and digital avionics. As the Army terminated the AH-56 program, digital avionics emerged, offering lighter, faster, more reliable, and more precise systems with superior night and all-weather capabilities. The cost of transitioning the AH-56 to these advanced systems played a role in its cancellation. Simultaneously, the simpler Bell Cobra, developed alongside the Cheyenne as a low-risk alternative, appeared as a more economical and readily available choice. Its shared engine, transmission, and rotor system with the Bell UH-1 Iroquois variants already in service added to its appeal.
Among the 10 AH-56 prototypes constructed by Lockheed, four have endured to this day. Exhibited at the Army Aviation Museum in Fort Rucker, Alabama, one is showcased in Fort Polk, Louisiana, and another in Kentucky’s Fort Campbell.
Many of the features found on the Cheyenne would later show up on other aircraft. For instance, by the time the Boeing AH-64 Apache entered service in 1986, helmet-mounted targeting displays were standard, although with far more capabilities than Cheyenne’s system had. The Apache also integrated the digital sensor and cockpit technologies that the AH-56 was just too early to incorporate.
As for swiveling gunner’s seats and sighting systems, just making the sensors themselves swivel, as well as the gun turret, and projecting the video feed in front of the pilot’s eye and on cockpit screens was a far more attractive option that was largely made possible by technological progress during the 1970s.
Though the Cheyenne never formally entered service, its influence on future attack helicopter designs and its role in paving the way for an advanced close air support aircraft concept cannot be overstated. U.S. Army Aviation Museum curator Bob Mitchell highlighted this impact in his 2018 interview, asserting that the Cheyenne played a crucial role in the inception of the A-10 program.
Describing the Cheyenne as the “father” of the A-10, Mitchell emphasized that the A-10 Thunderbolt, specifically designed for close air support, owes its existence to the Cheyenne’s legacy. The Cheyenne’s groundbreaking high-speed, compound helicopter configuration has found new life in the Sikorsky S-97 Raider, which holds potential as the Army’s next scout helicopter. Moreover, Sikorsky’s X-2 technology has led to the development of the SB-1 Defiant, competing to become a vital component of the Army’s Future Vertical Lift program, showcasing resemblances to the AH-56. Boeing, too, explored incorporating Cheyenne-like features into a major refresh of their Apache helicopter, highlighting the enduring influence of the Cheyenne’s design.
Though the Cheyenne’s ambitious nature led to certain technological dead-ends, such as the gunner’s rotating seat, it undeniably achieved remarkable advancements and should be commemorated for its significant contributions to the evolution of attack helicopter concepts.
