Modern-Aviation

The XH-17 also featured tip-jet-driven rotors. But this point, any similarity with Hiller’s rather dainty helicopter ends, as the XH-17 was a massive beast. Starting life as a rotor test rig under the auspices of the Kellett Aircraft Corporation, the XH-17 ducted bleed air from the compressor sections of two GE J35 jet engines.

After travelling 65 feet to the ends of the oversized rotor blades, fuel was added to the airflow and ignited, producing four distinct jet plumes in the trailing edge…and a noise signature like an AC/DC concert, complaints being received from eight miles away.

Facing financial issues, Kellett sold the XH-17 and their interest to the Hughes Aircraft Company. The first intentional flight took place, in 1952, when the XH-17 bounced wildly up and down. After some tinkering, Hughes managed to resolve the control issues, and the XH-17 entered an intensive 10-hour test programme, at which point the rotor’s fatigue life was used up.

Although there was a proposal for a four-bladed production version of the XH-17, the XH-28, the Army eventually decided not to pursue it. There was presumably not a massive requirement to move tanks across the battlefield at 80mph while being heard by everyone for many miles around.