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<!-- This article is a part of [[Wikipedia:WikiProject Aircraft]]. Please see [[Wikipedia:WikiProject Aircraft/page content]] for recommended layout. -->
{{Use dmy dates|date=January 2017}}
{|{{Infobox Aircraft Begin
{{Use British English|date=January 2017}}
{{Infobox aircraft
|name=P.74
|image= File:Percival p-74.jpg
|caption= Hunting Percival P.74 being readied for flight testing c. 1956
}}{{Infobox Aircraft Type
|type=[[Helicopter]]
|manufacturer=[[Hunting Aircraft|Percival Aircraft Company]]
|designer=
|national originnational_origin=United Kingdom
|first_flight=
|first flight=
|introduction=
|introduced=
|status=Cancelled 1956
|primary_user=
|primary user=
|produced=
|number builtnumber_built=1
|unit cost=
|developed fromdeveloped_from =
|variants with their own articles=
}}
 
|}
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 [[Tip jet|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>
{{TOC limit|limit=2}}
 
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In 1951, [[Hunting Aircraft|Percival Aircraft Company]] formed a helicopter division, and began design work on a medium-sized helicopter designated P.74. They designed the helicopter 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 that ran the full length of the fuselage. Beneath the cabin floor, two [[Napier & Son|Napier]] [[Napier Oryx|Oryx gas generators]] 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 required that exhaust pipes pass through the cabin wall between the rows of seats. This created excessive noise and heat for intended passengers.
 
The lack of a gearbox and the simplified rotor coupling to the aircraft meant that the design could employ a tilting [[Helicopter rotor|rotor hub]], and did not need [[drag hinge]]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 accommodate the necessary ducting to the tips. They also were [http://en.wikipedia.org/wiki/Feathering_[Feathering (propeller)#Feathering|non-feathering]], so ailerons were fitted to the blades.
 
The P.74 prototype (designated the [[Hunting Aircraft|Hunting Percival]] P.74 after the company change its name 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 a large bulbous fuselage that tapered to a tiny "tailcone" with 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 [[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>
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==Testing and evaluation==
[[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>
 
The designers planned to fit a more powerful [[Rolls-Royce RB108]] turbine, and a further development of a 10-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.
 
==Variants==
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:Proposed improved variant of the P.74 with a [[Rolls-Royce RB108]] engine and redesigned rotor system, not built.
 
==Specifications (P.74 as designed)==
{{Aircraft specs
{{aircraft specifications|
|ref=Flight<ref name=flight231255>{{cite journal|title=Hunting Percival P.74 Research Test Vehicle Approaches the Flight Stage: a New Helicopter Philosophy|journal=Flight|date=23 December 1955|pages=939–942|url=https://www.flightglobal.com/FlightPDFArchive/1955/1955%20-%201819.PDF|accessdate=21 September 2015}}</ref> |prime units?=imp
<!-- if you do not understand how to use this template, please ask at [[Wikipedia talk:WikiProject Aircraft]] -->
<!--
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General characteristics
|plane or copter?=copter
-->
|jet or prop?=prop
|genhide=
<!-- Now, fill out the specs. Please include units where appropriate (main comes first, alt in parentheses). If an item doesn't apply, like capacity, leave it blank. For additional lines, end your alt units with )</li> and start a new, fully-formatted line with <li> -->
|ref=''The Illustrated Encyclopedia of Helicopters''<ref>Apostolo 1984, p. 123.</ref>
|crew= 2
|capacity= 8 passengers in two rows
|length main=
|length alt=
|span main= 53 ft
|span alt= 15.76 m
|height main=
|height alt=
|area main=
|area alt=
|empty weight main=
|empty weight alt=
|loaded weight main=7,750 lb
|loaded weight alt= 3,515 kg
|max takeoff weight main= lb
|max takeoff weight alt= kg
|engine (prop)=[[Napier Oryx]] NOr. 1
|type of prop= [[gas generator]]
|number of props= 2
|power main= 754 "ghp" [[Horsepower#Shaft horsepower|shp]]
|power alt= 563 kW
|max speed main= 110 mph (intended)
|max speed alt= 177 km/h
|range main=329 miles
|range alt=530 km
|ceiling main=27,985 ft
|ceiling alt=8,530 m
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|crew=2
|capacity= 8 passengers
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|swept m=<!-- swing-wings -->
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|volume m3=<!-- lighter-than-air -->
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|empty weight kg=
|empty weight lb=
|empty weight note=
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|gross weight lb=
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|max takeoff weight lb=7750
|max takeoff weight note=
|fuel capacity={{convert|170|impgal|l USgal|abbr=on}}
|lift kg=<!-- lighter-than-air -->
|lift lb=<!-- lighter-than-air -->
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|more general=
<!--
Powerplant
-->
|eng1 number=2
|eng1 name=[[Napier NOr.1 Oryx]]
|eng1 type=single-shaft turbine gas generators
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|eng1 hp=750
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|eng3 number=
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|rot number=1
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|rot dia ft=55
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<!--
Performance
-->
|perfhide=
 
|max speed kmh=
|max speed mph=110
|max speed kts=
|max speed note=
|max speed mach=<!-- supersonic aircraft -->
|cruise speed kmh=178
|cruise speed mph=
|cruise speed kts=
|cruise speed note=
|stall speed kmh=
|stall speed mph=
|stall speed kts=
|stall speed note=
|never exceed speed kmh=
|never exceed speed mph=
|never exceed speed kts=
|never exceed speed note=
|minimum control speed kmh=
|minimum control speed mph=
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|range km=530
|range miles=
|range nmi=
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|combat range km=
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|ceiling ft=27,985
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|disk loading kg/m2=
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<!--
Armament
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|armament=<!-- add bulletted list here or if you want to use the following
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|guns=
|bombs=
|rockets=
|missiles=
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|hardpoint capacity=
|hardpoint rockets=
|hardpoint missiles=
|hardpoint bombs=
|hardpoint other=
 
|avionics=
}}
 
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|related=
|similar aircraft=
* [[Fairey Jet Gyrodyne]] (jet tipped rotor driven at takeoff and landing only)
* [[YH-32 Hornet|Hiller YH-32 Hornet]]
*[[Fiat 7002]]
*[[Hiller YH-32 Hornet]]
|see also=
* [[Fairey Rotodyne]]
 
}}
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===Bibliography===
{{Refbegin}}
* Apostolo, Giorgio. ''The Illustrated Encyclopedia of Helicopters''. New York: Bonanza Books, 1984. {{ISBN |0-517-439352}}.
* [http://www.flightglobal.com/pdfarchive/view/1955/1955%20-%201815.html "Hunting Percival P.74: Research Test Vehicle Approaches the Flight Stage: a New Helicopter Philosophy." (PDF)] ''Flight'' via ''flightglobal archive'', 1955.
* Winchester, Jim. ''The World's Worst Aircraft: From Pioneering Failures to Multimillion Dollar Disasters''. London: Amber Books Ltd., 2005. {{ISBN |1-904687-34-2}}.
{{Refend}}
 
== External links ==
* [http://avia.russian.ee/helicopters_eng/percival_p-74.php Hunting Percival P.74 1956]
 
{{Hunting Percival aircraft}}
{{Aviation lists}}
 
{{Aero specs missing}}
 
[[Category:Hunting Percival aircraft|P.74]]
[[Category:1950s British experimental aircraft 1950–1959]]
[[Category:Military helicopters]]
[[Category:1950s British helicopters 1950–1959]]
[[Category:Tipjet-powered helicopters]]
[[Category:Unflown aircraft]]
[[Category:Twin-turbine helicopters]]
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