In October 1952, at Culver City, California, a machine that looked like a derrick married to a bus lifted off the ground. The Hughes XH-17 had a two-bladed main rotor 130 feet in diameter — still the largest rotor ever flown on a helicopter, 73 years later. It was 53 feet tall. It used the front wheels from a B-25 bomber and the rear wheels from a C-54 transport because nothing else was strong enough. And it had no transmission.

That last detail is the interesting one.

The tip-jet principle. Conventional helicopters drive the rotor from a central shaft, which means the fuselage wants to spin the opposite direction (hence the tail rotor). Kellett engineers Andrew Stefan and Bernard Lindenbaum, working under a 1946 Air Force contract later transferred to Hughes Aircraft, threw that out entirely. Two General Electric 7E-TG-1 turbojets bled compressed air through ducts running up the rotor mast, out along the inside of each hollow blade, and into combustion chambers at the blade tips where fuel was injected and burned. The rotor was, in effect, a 130-foot ramjet pinwheel. No torque on the fuselage. No tail rotor needed (a small one was fitted for yaw control only).

What it could do. First flight 23 October 1952, pilot Gale Moore. It demonstrated lifting 10,284 pounds — at a time when the standard heavy-lift helicopter, the Sikorsky H-19, could manage about 2,000. The design payload was 15 tons, intended for retrieving downed aircraft and moving artillery in Korea. The XH-28 follow-on, on paper, would have lifted 27 tons.

Why it died. Three reasons, none of them fundamental:

• Fuel consumption was catastrophic. Tip-jets are thermodynamically lousy — you're running an open-cycle combustor at the worst possible radius. Range was about 40 miles.
• Vibration. A 130-foot two-blade rotor produces enormous 2-per-rev forces. Hughes flight-tested it only to 50 hours before fatigue cracks appeared in the rotor hub.
• The Army got Sikorsky instead. The H-37 Mojave (1956) delivered useful heavy lift with conventional engineering and acceptable economics. Program canceled December 1955. The single prototype sat outdoors at Culver City until 1958, then scrapped.

Why this deserves a second look in 2026. The fuel-burn problem was a 1950s problem. Modern alternatives have appeared that the original engineers couldn't have used:

• Electric tip-drive. Replace the combustors with brushless electric motors at the blade tips, powered by a slip ring at the hub from a turboelectric generator or batteries. You keep the no-torque, no-transmission architecture — which eliminates the single most failure-prone, weight-intensive component on any helicopter — without the SFC penalty. Several papers since 2019 (notably from DLR Braunschweig) have modeled this for heavy-lift VTOL.
• Composite rotors. The XH-17 used welded steel and aluminum. Carbon-fiber/titanium hybrid blades at that diameter would weigh roughly one-third and survive the 2-per-rev loads.
• The mission came back. Outsized cargo VTOL — wind turbine nacelles (often 80+ tons), modular nuclear reactor segments, disaster-area bridge sections — is precisely what nothing in the current fleet does. The CH-53K caps at 18 tons. A modernized tip-drive heavy lifter sits in the empty space above it.

Hughes was solving the right problem with the wrong energy source. The architecture was sound; the combustor was the bug, not the feature.