On September 21, 1967, test pilot Don Segner lifted a strange machine off the Van Nuys, California runway. It had a main rotor, a tail rotor, small stubby wings, and — most peculiarly — a giant pusher propeller at the very back. It was the Lockheed AH-56A Cheyenne, and within a year it would fly at 244 mph in level flight. For context, the AH-64 Apache — the Army's current attack helicopter, designed after the Cheyenne was killed — maxes out at 158 mph. The Cheyenne, in 1968, was 55% faster than the machine that replaced it.

The Cheyenne won the Army's Advanced Aerial Fire Support System (AAFSS) competition in November 1965, beating a Sikorsky proposal. Lockheed — better known for airliners and spy planes than helicopters — leaned on radical thinking pioneered by engineer Irv Culver on the earlier CL-475: a rigid rotor with a gyroscopic control system mounted above the hub. Instead of hinges flapping to compensate for asymmetric lift, the gyro processed forces directly through the swashplate. Combined with a General Electric T64 turboshaft driving both the rotor and a rear pusher prop through a common gearbox, plus small wings to offload the rotor at high speed, the aircraft was the world's first practical compound helicopter attack platform.

The capabilities were genuinely alien for 1967:

• Speed: 244 mph achieved (design target 253 mph)
• Ferry range: 2,000+ miles
• Combat radius: 460 miles with full weapons load
• Nose turret: 30mm cannon slaved to a helmet-mounted sight that tracked wherever the gunner looked — decades before Apache pilots had this
• Belly turret: Independently pointing 40mm grenade launcher
• Sensors: Terrain-following radar, night vision, laser rangefinder
• Hardpoints: Six TOW missiles or 2.75-inch rocket pods on wing pylons

Ten prototypes were built. Then it fell apart. On March 12, 1969, prototype #3 experienced a divergent 1/2P rotor oscillation during high-speed testing and destroyed itself, killing test pilot David Beil. The gyro-control system had a resonance mode nobody had modeled correctly. Lockheed grounded the fleet and spent 18 months redesigning the control system with a "control gyro" configuration that fixed the problem — engineers later confirmed the fix worked.

But politics had turned. Vietnam was winding down. The Army's Cheyenne program office had earned a reputation for cost overruns (unit price ballooned from $1.4M to $3.5M). The Air Force actively lobbied against it, arguing fixed-wing A-X (which became the A-10) should own close air support. On May 9, 1972, Secretary of the Army Robert Froehlke cancelled the program. The follow-on Advanced Attack Helicopter (AAH) program deliberately dropped the compound configuration, chose a conservative conventional rotorcraft, and produced the Apache — slower, shorter-legged, but "safe."

Why revive it now? The Cheyenne's core insight — that a compound configuration with rotor offloading beats a pure helicopter at any speed above 180 knots — has been vindicated. Sikorsky's X2 demonstrator (2010) hit 288 mph. The S-97 Raider and SB>1 Defiant both use coaxial rotors with pusher props — direct descendants of the Cheyenne's philosophy. Modern composite rotor blades, fly-by-wire flight controls, and active vibration cancellation eliminate every failure mode that killed prototype #3 in 1969. Computational fluid dynamics can model rotor-pusher interaction in hours, not years of flight test. The gyro-control resonance that killed Dave Beil would be caught in simulation before metal was cut.

The Army's Future Attack Reconnaissance Aircraft (FARA) competition — which selected the Bell 360 Invictus before being cancelled in February 2024 — was, essentially, an attempt to build a Cheyenne with 55 years of technology bolted on. The problem was solved in 1968. We just threw away the solution.