Percival P.74: Difference between revisions

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The '''Percival P.74''' (later '''Hunting Percival P.74''') was a [[United Kingdom|British]] experimental [[helicopter]] designed in the 1950s that was based on the use of [[Helicopter#Tip jetsjet|tip-jet]] powered [[Helicopter rotor|rotors]]. Although innovative, the tip-rotor concept literally failed to get off the ground in the P.74, doomed by its inadequate power source. Rather than being modified, the P.74 was ignominiously towed off the airfield and scrapped.<ref>Winchester 2005, p. 230.</ref>

In 1951, a Helicopter Division was formed by [[Hunting Aircraft|Percival Aircraft Company]] formed a helicopter division, and began design work commenced on a medium-sized helicopter designated P.74. TheThey helicopterdesigned wasthe designedhelicopter to meet [[List of Air Ministry Specifications|Air Ministry Specification]] EH.125D issued in May 1952 for an experimental helicopter to test jet driven rotors. This experimental helicopter had a teardrop-shaped fuselage with a two-seat cockpit in the nose and a large cabin runningthat ran the full length of the fuselage. Beneath the cabin floor were, two [[Napier & Son|Napier]] [[Napier Oryx|Oryx gas generators]] which fed compressed air to the tips of the three rotor blades through triple ejector ducts. The rotor blades used [[ailerons]] on the trailing edges with [[Pitch (flight)|pitch]] control achieved by a [[screw jack]]. The unusual engine location necessitatedrequired that exhaust pipes comingpass through the cabin wall between the rows of seats,. creatingThis ancreated unenviable amount ofexcessive dinnoise and heat for the intended passengers.

The lack of a gearbox and the simplified coupling of rotor coupling to the aircraft meant that the design could employ a tilting [[Helicopter rotor|rotor hub]], couldand bedid usednot andneed [[drag hinges were not neededhinge]]s.<ref name="Flight 1955"/> The low torque coupling at the mast meant that very little was needed in the form of lateral control. The P.74 rotor was expected to be quieter in operation than tip jets, following tests with a Derwent engine powered rotor. The stainless-steel rotors were thick in cross section to allow foraccommodate the necessary ducting to the tips. andThey also were [[Feathering (propeller)#Feathering|non-feathering]], - as a resultso ailerons were fitted to the blades.

The P.74 prototype (designated the [[Hunting Aircraft|Hunting Percival]] P.74 after the company name change wasits institutedname in 1954) was completed in the spring of 1956, and given the [[United Kingdom military aircraft serials|military serial number]] ''XK889''. The final product looked decidedly ungainly, with thea large bulbous fuselage taperingthat tapered to a tiny "tailcone" that featuredwith an equally tiny tail rotor (deemed sufficient for control since there was no torque from the tip-rotors). The undercarriage consisted of four wheels on splayed-out stubs with the front two wheels being [[Caster|castoring]] for the front two wheels. The large capacity of the P.74 was to show the possible commercial aspect.<ref name="Flight 1955">Flight 1955</ref>

A larger commercial variant, the 10-passenger Percival P.105, with stub wing mounted engines either side of the rotor mast was envisaged, and the P.74 was expected to offer information into the necessary ducting required hence the engine was mounted underneath the fuselage with ducts running up through the cabin.<ref name="Flight 1955"/>

[[ImageFile:Percival p-74 2.jpg|thumb|right|Hunting Percival P.74 c. 1956]]

Ground testing in a static rig commenced in 1956, but the Oryx engines failed to develop full power and maximum gas flow. Even with modifications to the power units, the first flight was aborted when the P.74 failed to fly. This may have been providential as there were no escape provisions for the two pilots.<ref name= "Winchester">Winchester 2005, p. 231.</ref> The only entrance door was located at the rear on the port side. The primary test pilot was famously quoted as saying the hapless P.74 had, "...the cockpit, flying controls and engine controls... designed without any input from a pilot."<ref name= "Winchester">Winchester 2005, p. 231.</ref>

ItThe wasdesigners planned to fit a more powerful [[Rolls-Royce RB108]] turbine, and a further development of a ten10-passenger (P.105)<ref name= "Winchester"/> variant was on the "drawing boards" when the rationalisationnationalisation of the helicopter industry later that year resulted in the P.74 project being cancelled and the prototype scrapped.

==Specifications (P.74 as designed)==

* [[Fairey Jet Gyrodyne]] (jet tipped rotor driven at takeoff and landing only)

* [[Fairey Rotodyne]]

[[Category:1950s British helicopters 1950–1959]]