proprotor

On several aerial vehicles such as the AgustaWestland AW609 and V-22 Osprey, a pair of three-bladed proprotors have been used.Croft, John. [http://www.airspacemag.com/military-aviation/osprey.html "Tilters."] {{Webarchive|url=https://web.archive.org/web/20080725043315/http://www.airspacemag.com/military-aviation/osprey.html |date=2008-07-25}} [http://www.airspacemag.com/military-aviation/tilters-21162862/?all Alternate link]Air & Space/Smithsonian, 1 September 2007. Accessed on 6 May 2015. Both the proprotors and engines are mounted on load-bearing rotatable pylon at the wingtips, allowing the proprotors to be positioned at various angles. In the case of the AW609's, while flown in helicopter mode, the proprotors can be positioned between a 75- and 95-degree angle from the horizontal, with 87 degrees being the typical selection for hovering vertically; and in aeroplane mode, the proprotors are rotated forward and locked in position at a zero-degree angle, spinning at 84% RPM.{{cite news |url=http://www.verticalmag.com/news/article/Flying-the-AW609:-a-preview |title=Flying the AW609: A Preview |work=Vertical |first=Elan |last=Head |date=20 January 2014 |accessdate=20 January 2014}} STOL rolling-takeoff and landing capability is achieved by having the nacelles tilted forward up to 45°.[http://www.bellhelicopter.com/MungoBlobs/126/268/V-22%20Guidebook%202013_update_PREVIEW_LR2.pdf "V-22 Osprey Guidebook, 2013/2014."] {{webarchive |url=https://web.archive.org/web/20141020133122/http://www.bellhelicopter.com/MungoBlobs/126/268/V-22%20Guidebook%202013_update_PREVIEW_LR2.pdf |date=October 20, 2014}} Bell-Boeing, 2013. Retrieved: 6 February 2014. [https://web.archive.org/web/20141020133122/http://www.bellhelicopter.com/MungoBlobs/126/268/V-22%20Guidebook%202013_update_PREVIEW_LR2.pdf Archived] in 2014.Chavanne, Bettina H. [http://www.aviationweek.com/aw/generic/story_generic.jsp?channel=defense&id=news/awst/2010/01/11/AW_01_11_2010_p44-193636.xml&headline=USMC%20V-22%20Osprey%20Finds%20Groove%20In%20Afghanistan "USMC V-22 Osprey Finds Groove In Afghanistan."]{{dead link|date=February 2018 |bot=InternetArchiveBot |fix-attempted=yes}} Aviation Week, 12 January 2010. Retrieved: 23 June 2010.

Typically, flight control software would perform much of the complex transition between the distinct helicopter and aeroplane modes; while automated systems are usually provided to inform crews on the optimal tilt angle and air speed to pursue.{{cite news |url=http://www.aviationtoday.com/the-checklist/The-AW609-Tilt-Rotor-2014s-Best-Ride_83577.html |title=The AW609 Tilt Rotor: 2014's Best Ride |work=Aviation Today |first=Ernie |last=Stephens |date=1 December 2014 |accessdate=1 December 2014 |archiveurl=https://web.archive.org/web/20141202001100/http://www.aviationtoday.com/the-checklist/The-AW609-Tilt-Rotor-2014s-Best-Ride_83577.html |archivedate=2 December 2014 |url-status=live}} Furthermore, it is typical for flight controls, such as blade pitch, to both resemble and function akin to their counterparts on conventional rotorcraft, easing the transition of conventional helicopter pilots to such vehicles.

Proprotors can be designed to fold for storage purposes.Currie, Major Tom P., Jr., USAF. [https://fas.org/man/dod-101/sys/ac/docs/99-033.pdf "A Research Report Submitted to the Faculty, In Partial Fulfillment of the Graduation Requirements: The CV-22 'Osprey' and the Impact on Air Force Combat Search and Rescue" (PDF).] {{Webarchive|url=https://web.archive.org/web/20160306213726/https://fas.org/man/dod-101/sys/ac/docs/99-033.pdf |date=2016-03-06}} Air Command and Staff College, April 1999. However, in the case of the V-22, in order to facilitate proprotor folding, the proprotor's diameter had to be constrained to a diameter of 38-foot (11.6 m), five feet (1.5 m) less than optimal for vertical takeoff; this difference has been attributed for causing relatively high disk loading.Whittle, Richard. "[http://defense.aol.com/2012/09/05/flying-the-osprey-is-not-dangerous-just-different-veteran-pilo/ Flying The Osprey Is Not Dangerous, Just Different: Veteran Pilots] {{webarchive|url=https://web.archive.org/web/20120914073208/http://defense.aol.com/2012/09/05/flying-the-osprey-is-not-dangerous-just-different-veteran-pilo|date=2012-09-14}}" defense.aol.com, 5 September 2012. Retrieved: 16 September 2012. [https://web.archive.org/web/20131003121815/http://breakingdefense.com/2012/09/05/flying-the-osprey-is-not-dangerous-just-different-veteran-pilo/ Archived] on 3 October 2013.

In a typical implementation, both proprotors must be rotating in order to maintain flight in helicopter mode. To guard against instances of single engine failure, on both the V-22 and AW609, both engines are connected by drive shafts to a common central gearbox so that one engine can power both proprotors if such a failure occurs.Norton 2004, pp. 98–99. Despite this provision, the V-22 is generally not capable of hovering on a single engine.Whittle, Richard. "[http://breakingdefense.com/2015/07/fatal-crash-prompts-marines-to-change-osprey-flight-rules/ Fatal Crash Prompts Marines To Change Osprey Flight Rules] {{Webarchive|url=https://web.archive.org/web/20150719000019/http://breakingdefense.com/2015/07/fatal-crash-prompts-marines-to-change-osprey-flight-rules/ |date=2015-07-19}}". Breaking Defense, 16 July 2015. If a proprotor gearbox fails, that proprotor cannot be feathered, and both engines must be stopped prior to an emergency landing. The autorotation characteristics are poor partly due to the rotors' low inertia.McKinney, Mike. [http://www.verticalmag.com/features/features_article/20112-flying-the-v-22.html "Flying the V-22"] Vertical (magazine), 28 March 2012. [https://web.archive.org/web/20140430000553/http://www.verticalmag.com/features/features_article/20112-flying-the-v-22.html Archived] on 30 April 2014.

• Bell XV-15
• Bell Boeing V-22 Osprey
• Bell Eagle Eye
• Bell V-280 Valor
• AgustaWestland AW609
• NASA Puffin
• Leonardo Next-Generation Civil Tiltrotor

{{reflist}}

{{Refbegin}}

• Norton, Bill. Bell Boeing V-22 Osprey, Tiltrotor Tactical Transport. Earl Shilton, Leicester, UK: Midland Publishing, 2004. {{ISBN|1-85780-165-2}}.
• Whittle, Richard. [https://books.google.com/books?id=_9Asc0bgm_cC The Dream Machine: The Untold History of the Notorious V-22 Osprey.] New York: Simon & Schuster, 2010. {{ISBN|1-4165-6295-8}}.

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{{Aircraft gas turbine engine components}}

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Category:Aircraft configurations