# Tiltwing

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{{Short description|Aircraft with a rotating wing for takeoff and landing}}
[[File:X-18 tilting its wing bw.jpg|thumb|[Hiller X-18](/source/Hiller_X-18) tilting its wing]]

A '''tiltwing''' [aircraft](/source/aircraft) features a wing that is horizontal for conventional forward flight and rotates up for vertical takeoff and landing. It is similar to the [tiltrotor](/source/tiltrotor) design where only the [propeller](/source/Propeller_(aircraft)) and engine rotate. Tiltwing aircraft are typically fully capable of [VTOL](/source/VTOL) operations.<ref name=Straight_Up>Markman, Steve and Bill Holder. "Tilt-Wing VTOL Systems". ''Straight Up: A History of Vertical Flight''. Schiffer Publishing, 2000. {{ISBN|0-7643-1204-9}}.</ref>

thumb|VTOL disc loading lift efficiency

The tiltwing design offers certain advantages in vertical flight relative to a tiltrotor. Because the slipstream from the rotor strikes the wing on its smallest dimension, the tiltwing is able to apply more of its engine power to lifting the aircraft. For comparison, the [V-22 Osprey](/source/V-22_Osprey) tiltrotor loses about 10% of its thrust to interference from the wings.<ref>[http://www.flightglobal.com/blogs/the-dewline/2009/06/boeing-looks-ahead-to-a-v-23-o.html Boeing looks ahead to a 'V-23' Osprey]</ref>

Another advantage of tiltwing aircraft is the ease of transition between VTOL and horizontal flight modes.  A tiltrotor must first fly forwards like a helicopter, building airspeed until wing lift is sufficient to allow the nacelles to begin tilting down.  As a note, the MV-22 Osprey's stall speed in airplane mode is {{convert|110|kn|km/h mph|-0}}.  Conversely, a tiltwing aircraft can begin the transition from helicopter to airplane at zero forward airspeed. Because of this, the [Canadair CL-84 Dynavert](/source/Canadair_CL-84_Dynavert) was able to take off vertically, then accelerate from zero airspeed to {{convert|100|kn|km/h mph|-0}} in 8 seconds.<ref>[https://www.flightglobal.com/pdfarchive/view/1992/1992%20-%200263.html Tilting at Targets]</ref>

However, the fixed wing of a tiltrotor aircraft offers a superior [angle of attack](/source/angle_of_attack)—thus more lift and a shorter takeoff roll—when performing [STOL](/source/STOL)/[STOVL](/source/STOVL) operations.{{Citation needed|date=September 2010}}

The main drawbacks of tiltwing aircraft are susceptibility to wind gusts in VTOL mode and lower hover efficiency. The wing tilted vertically represents a large surface area for crosswinds to push against.<ref name=Straight_Up/> Tiltrotors generally have better hover efficiency than tiltwings, but less than helicopters.<ref>Warwick, Graham. "[http://www.flightglobal.com/pdfarchive/view/1992/1992%20-%200262.html Tilting at targets]" page 44 ''[Flight International](/source/Flight_International)'', February 1992. Accessed: 4 January 2014.</ref>  This is due to the difference in rotor disk loading.

As of 2014, [NASA](/source/NASA) is testing a diesel-electric hybrid 10-foot 10-rotor tiltwing called the [GL-10 Greased Lightning](/source/NASA_GL-10_Greased_Lightning), with most propellers folding during horizontal flight.<ref>Warwick, Graham. "Distributed power" ''[Aviation Week & Space Technology](/source/Aviation_Week_%26_Space_Technology)'' page 31, 25 August 2014. Accessed: 26 August 2014.</ref>

==List of tiltwing aircraft==
Tiltwing designs with rocket, jet, or propeller propulsion

* [Avión Torpedo](/source/Avi%C3%B3n_Torpedo) (1902)
* [Weserflug P.1003](/source/Weserflug_P.1003) (1938)
* [Vertol VZ-2](/source/Vertol_VZ-2) (1957)
* [Hiller X-18](/source/Hiller_X-18) (1959)
* [Kaman K-16B](/source/Kaman_K-16B) (1959)
* [LTV XC-142](/source/LTV_XC-142) (1964)
* [Canadair CL-84 Dynavert](/source/Canadair_CL-84_Dynavert) (1965)
* [NASA GL-10 Greased Lightning](/source/NASA_GL-10_Greased_Lightning) (2014)
* [Airbus A³ Vahana](/source/Airbus_A%C2%B3_Vahana) (2018)
* [Pterodynamics Transwing](/source/PteroDynamics)

==See also==
* [Thrust vectoring](/source/Thrust_vectoring)
* [Tailsitter](/source/Tailsitter)
* [Tiltrotor](/source/Tiltrotor)
* [Tiltjet](/source/Tiltjet)
* [Coleopter](/source/Coleopter)
* [PTOL](/source/PTOL)
* [VTOL](/source/VTOL)
* [Variable-incidence wing](/source/Variable-incidence_wing)

==References==
{{Reflist|1}}

{{Aircraft types (by method of thrust and lift)}}

Category:Aircraft configurations
Category:Tiltwing aircraft

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Adapted from the Wikipedia article [Tiltwing](https://en.wikipedia.org/wiki/Tiltwing) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Tiltwing?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.