Hunting Percival P.74


The P.74 was intended as a demonstrator for a new type of helicopter. It worked on the tip-jet principle, but unlike the Hiller Hornet with its individual ramjets, the P.74 had a gas generator under the cabin floor which fed compressed air through triple ducts to the three-bladed rotor, each blade of which had triple ejector ducts.

Months of testing in a static rig showed up many problems with the power system, which refused to develop full power and maximum gas flow. Finally these problems were fixed and a first flight attempted. Despite the efforts of two pilots on the very stiff controls, the P.74 resolutely refused to fly. One engineer associated with the project says that a consultant designer used the wrong formula for calculating lift. All the figutes added up but the P.74 went nowhere. Actually it was ordered to be towed across the airfield out of sight, and that is about the last anyone heard of it.

Jim Winchester "The World's Worst Aircraft", 2005

Hunting Percival P.74

In 1951, a Helicopter Division was formed by Hunting Percival and design work commenced on a medium-sized helicopter designated P.74. This machine had a teardrop-shaped fuselage with the two-seat cockpit in the nose and a large cabin running the full length of the fuselage. Beneath the cabin floor was a Napier Oryx gas generator which fed compressed air to the tips of the three rotor blades. The prototype was completed in the spring of 1956, carrying the military serial number XK889. Ground testing commenced but the Oryx engine was insufficiently powerful and the P.74 failed to fly. It was planned to fit a more powerful Rolls-Royce RB.108 turbine, but the rationalisation of the heli-copter industry later that year resulted in the P.74 project being cancelled.

R.Simpson "Airlife's Helicopter and Rotorcraft", 1998

Technical data for P.74

Engine: 2 x Napier "Oryx" rated 560êÂò each, rotor diameter: 16.77ì, take-off weight: 3518êã, cruising speed: 178êì/÷, ceiling: 8530ì, range: 530êì