Before the unfortunate demise of RAH-66 Comanche, there was AH-56 Cheyenne, and the latter was the epitome of “in the wrong place at the wrong time,” as the aircraft’s rigid-rotor design concept was obviously way ahead of its time.

Dawn of Close Air Support

It was the mid-1960s, and Lockheed had just presented a novelty aircraft concept to the U.S. Army under the Advanced Aerial Fire Support System (AAFSS) program that would eventually become the service’s first dedicated attack helicopter.

According to Bob Mitchell, curator of the Army Aviation Museum, the AH-56 Cheyenne featured designs from “the rigid rotor system,” which was present in Lockheed’s previous aircraft—the CL-475 (1959) and the XH-51 (1962). The manufacturing company equipped the AH-56 Cheyenne with a four-bladed rotor system, subsequently configuring it into a compound helicopter with low-mounted wings and a tail-mounted thrusting propeller powered by a General Electric T64 turboshaft engine. Consequently, the aircraft was mapped out to have a high-speed capability so it could catch up and provide escort for the Army’s utility helicopters.

The design was approved, and by 1966, Lockheed received a contract detailing to supply ten prototypes of the futuristic AH-56 Cheyenne to the U.S. Army. By mid-1967, the company began its first official flight test using the second AH-56 (s/n 66-8827). However, engineers uncovered issues on the earliest prototype and decided against proceeding to flight testing to resolve those problems.

“It’s an enormous aircraft and it was capable of great speeds—that was one of the main reasons (the Army) wanted the program,” said Mitchell. “(The Cheyenne) had a set of aerodynamic wings on it, so the faster the aircraft went, the more the rotor loads were reduced.”

Ahead of its Time

If it arose today, the AH-56 Cheyenne would probably receive tons of recognition and praise for its impressive features. It boasts over 54 ft in length and more than 13 ft in height—quite a size considering its predecessor, XH-51, was just about 40 ft in length and over 8 ft in height. AH-56 Cheyenne also weigh much heavier than the XH-51, almost tripling its empty weight of more than 12,215 lbs (5,541 kg).

The aircraft had an outstanding cruising speed of 195 knots and a maximum speed of 212 knots, slightly higher compared to today’s AH -64 Apache, which only has a cruising speed of 158 knots and a top speed of 197 knots.

AH-64 Apache AH-56 Cheyenne
A side-by-side comparison of an AH-64 Apache (left) and AH-56 Cheyenne (right). (Image source: Boeing, Wikimedia Commons)

“It was a spectacular concept, and it’s an aircraft that still to this day is way ahead of its time,” said the museum curator.

Other notable features of the AH-56 Cheyenne include a pusher propeller in its tail rotor that increases its maneuverability, especially during high-risk situations, and its contemporary fire control systems.

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“One of the key factors in gunship operations—certainly when conducting diving fire—is that your speed builds exponentially, so you only have a couple of seconds to acquire, engage then start your recovery,” Mitchell explained. “On the Cheyenne, the pilot could enter his dive, then reverse thrust on the pusher to slow the aircraft down considerably, allowing him to fixate on the target, fire, and then start his recovery. For that reason, alone it was a beautiful gunship.”

But The World Wasn’t Ready, Yet

Nevertheless, the aircraft wasn’t without its faults. As mentioned, the earlier prototype of AH-56 Cheyenne encountered problems that consequently delayed its maiden flight test. However, the project’s major setback happened in March 1969, when the rotor system of prototype no. 3 (s/n 66-8828) hit the fuselage, resulting in a fatal crash that instantly killed its pilot. After that, several technical problems and unsatisfactory progress began taking over the project, pushing the Army to issue a cure notice to Lockheed in April 1969.

This was the 1960s, though, and resources weren’t yet that bountiful. Plus, the production timeline delays and increasing technical issues on the AH-56 Cheyenne weren’t helping. By May 1969, the Army terminated the production contract of the project, except for the development contract that would allow Lockheed to continue exploring the concept and, perhaps, resolve persisting problems. The project was able to produce prototype no. 10 (s/n 66-8835) by September that year. Still, the increasing costs, the political tension between the Army and the Air Force tugging over “we’re in charge of close air support missions.” The emergence of other capable yet less costly helicopters had ultimately killed the program.

“This was the late 1960s and the cost per aircraft (was in the millions), so when (Bell) came out with the Cobra, which was a fraction of the cost, they couldn’t justify it,” Mitchell said, adding that since the Bell’s UH-1 Iroquois (Huey) and AH-1 Cobra essentially share identical parts, repairs wouldn’t be a problem. “That was probably the biggest factor that killed the program.”

Despite not having seen the light of day, the AH-56 Cheyenne wasn’t really a total flop. Its concept, design, and even airframe have moved along with the passing years and made it into today’s technology. Without the Cheyenne program, projects like the A-10 Thunderbolt and other close air support programs wouldn’t exist.

(H/T: U.S. Army)