Folding wing

Douglas Skyraider

A folding wing is a wing configuration design feature of aircraft to save space, and is typical of carrier-based aircraft that operate from the limited deck space of aircraft carriers. The folding allows the aircraft to occupy less space in a confined hangar because the folded wing normally rises over the fuselage decreasing the floor area of the aircraft. Vertical clearance is also limited in aircraft carrier hangar decks. In order to accommodate for this, some aircraft such as the Supermarine Seafire and Fairey Gannet have additional hinges to fold the wingtips downward, while others such as the S-3 Viking have folding tails.

Short Brothers, the world's first aircraft manufacturer, developed and patented[1] folding wing mechanisms for biplane ship-borne aircraft like their Short Folder, the first patent being granted in 1913. The Folder's biplane wings were hinged so that they folded back horizontally alongside the fuselage,[2] usually being held in place by latches projecting sideways from the rear of the fuselage.

Since the monoplane supplanted the biplane in the late 1930s, virtually all fixed-wing aircraft designed for shipboard duty have been equipped with folding wings. Notable exceptions include the SBD Dauntless, F2A Buffalo, and A4D/A-4 Skyhawk (all USN types), the Mitsubishi A5M, and Yokosuka D4Y (Japanese), and the Sea Harrier (British). All six are relatively compact designs.

The Grumman-patented Sto-Wing aftwards-folding wing folding system, pioneered on the Grumman F4F-4 Wildcat, has been used since World War II on a number of Grumman-designed carrier aircraft, and is still in use in the 21st century on the Grumman E-2 Hawkeye shipboard AEW aircraft.[3][4]

A folding wing has some disadvantages compared to a fixed wing. It is heavier and has more complex connections for electrical, fuel, aerodynamic and structural systems.

Comparison of the Grumman F4F Wildcat between folded and unfolded wings.

Many naval helicopters have rotor blades that can be aligned over the fuselage to save space on board ships.

Folding surfaces are rare among land-based designs, and are used on aircraft that are tall or too wide to fit inside service hangars. Examples include the Boeing B-50 Superfortress and its folding tail. The Saab 37 Viggen and the Boeing 377 Stratocruiser have foldable rear fins that make them lower for entering hangars. The Boeing 777 (classic) twinjet wide-body airliner was offered with folding wingtips for confined airports. The new Boeing 777X models will feature a shorter and simpler folding wingtip than was planned for the earlier Boeing 777. This will provide an extra 7 metres of wingspan in flight, yet the plane will still fit inside the same airport gates as the 777-300.

Simple fold

Aftward fold

Double fold

Rotating wing

Folding-wing planes on flight deck

Notes

  1. ↑ Patents secured by Short Brothers including patents nos. 1792/13, 15727/13 and 28610/13, 5290/14, 20537/14 and 9276/15, see Barnes and James, pp. 92, 110
  2. ↑ Flight 1956
  3. ↑ Dwyer, Larry (19 February 2014). "The Aviation History Online Museum - Grumman F4F Wildcat". aviation-history.com. The Aviation History Online Museum. Retrieved April 2, 2016. The F4F-4 was the first version of the Wildcat to feature a Grumman innovation, the Sto-Wing. The Sto-Wing used a novel approach using a compound angle folding-wing that was unique to Grumman...It was a successful design that was later used on the F6F Hellcat and TBF Avenger.
  4. ↑ "WING-FOLDING MECHANISM OF THE GRUMMAN WILDCAT - An American Society of Mechanical Engineers Historic Mechanical Engineering Landmark". asme.org. American Society of Mechanical Engineers. May 15, 2006. Retrieved April 29, 2017. The innovative wing folding mechanism (STO-Wing), developed by Leroy Grumman in early 1941 and first applied to the XF4F-4 Wildcat, manufactured by the Grumman Aircraft Engineering Corporation, is designated an ASME Historic Mechanical Engineering Landmark.

Bibliography

  • Barnes C.H. & James D.N. Shorts Aircraft since 1900. London (1989): Putnam. p. 560. ISBN 0-85177-819-4.

Herman L. Grimes, Sr. U.S. Patent 2,137,486 United States Patent Office. Patented November 22, 1938 Filed August 22, 1936 Book Title: "Quest for Recognition of a Father's Invention" Author: Jr. Herman L. Grimes Published October 8, 2009

http://professionalpublishinghouse.com/millbook_annotations/mb_quest.htm

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