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.
In 1935, the Douglas TBD Devastator was the first aircraft to feature hydraulic folding wings, allowing the pilot to fold the wings from the cockpit without requiring other sailors to fold them manually.[3]
Description
Comparison of the Grumman F4F Wildcat between folded and unfolded wingsNorth American XB-70 in flight with 65% percent (fully folded) wing position
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,[4][5] a version of which is still in use in the 21st century on the Grumman E-2 Hawkeye shipboard airborne early warning (AEW) aircraft and its C-2 Greyhound derivative.[6][7]
Another Grumman naval aircraft, the F-14 Tomcat, had variable-sweep wings that could be swept between 20° and 68° in flight. For parking, the wings could be "overswept" to 75°.[8]
A folding wing has some disadvantages compared to a non-folding wing. It is heavier and has more complex connections for electrical, fuel, aerodynamic, and structural systems.
Folding surfaces are rare among land-based designs and are used on aircraft that are too 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) twinjetwide-bodyairliner was offered with folding wingtips for confined airports. The new Boeing 777X models feature a shorter and simpler folding wingtip than was planned for the earlier Boeing 777. This will provide an extra 7 metres (23 ft) of total wingspan in flight, yet the plane will still fit inside the same airport gates as the 777-200LR/777-300ER.
An example of aircraft using folding wingtips other than stowage/hangar space such as aerodynamics and flight handling was the North American XB-70 Valkyrie. This increased both compression lift and enhanced directional stability at high speeds.
^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
^Dwyer, Larry (19 February 2014). "The Aviation History Online Museum - Grumman F4F Wildcat". 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.