TheGouge flap, is a type ofaircraft flap, which moves on a track when raised or lowered; in level flight. Invented byArthur Gouge ofShort Brothers in 1936, it allows pilots to increase both the wing area and the chord of an aircraft's wing, thereby reducing thestalling speed at a given weight. This provides benefits including a shorter take-off distance for any given load, a shorter distance to achieve a specific height and a lower take-off speed. However, the Gouge flap system, in spite of its use on production aircraft like theShort Sunderland and theShort Stirling, has only been used on aircraft produced by Short Brothers.
The Gouge flap was patented in 1936, British Patent no. 443,516 being awarded jointly to Short Bros. Ltd. and Arthur Gouge for "Improvements in or connected with Wings for Aircraft, (controller flaps)".[1]
The Gouge flap "consists of a sharp nosed aerofoil, which in the closed position, forms part of the wing profile . The flap tapers with the wing, i.e. the width of the flap at any point is a constant proportion of the wing chord at that point; when open the extended portion also varies with the chord. All sections through the flappedportion of the wing are similar in shape and proportion. The flap moves on tracks, rotating conically about an imaginary axis below the wing, nearly parallel to the trailing edge. When open, the flap increases the wing chord and the wing area."[2]
The BritishAeronautical Research Committee's research paper R&M No. 1753 concluded, among other things, that Gouge flaps half and fully open, decreased take-off distance by 14% and 23% respectively and decreased the distance from starting to clearing a "50 ft obstacle" by 21% and 23% respectively. Speed at take-off was "reduced by 3 and 8 m.p.h, respectively."[3]
Short Brothers first installed the Gouge flap on aScion fitted with the (scaled-down) wings being prepared for theShort Empire flying-boat.[4] The flaps on this aircraft, which was designated 'M.3', were submitted to extensive testing by theRoyal Aircraft Establishment Farnborough, their report appearing as R&M No. 1753 (seeBibliography below). Shorts used the Gouge flaps on several successful aircraft types, e.g. the Empire boats,[5] theShort S.26 G-class 'Golden Boats', theShort Sunderland[6] and theStirling.[7]
WhenFlight Magazine described theFowler flap in 1942,[8] the article's subtitle read "An American High-lift Device With Properties Similar to Those of the Better-known British Types", and the Gouge,Handley Page, andFairey/Youngman flaps were all given equal mention. The Gouge flap, although widely used on Shorts aircraft, was not adopted by other manufacturers, several of which developed their own variants. TheAeronautical Research Council's R&M no. 2622 entitled "The Aerodynamic Characteristics of Flaps" dated 1947 compared many variants but merely mentions the Gouge flap in a footnote on p. 10, where it is described as being "rather like the Blackburn flap ... but with no slot between the flap and wing."[9]
The advantage of the extra value of the maximum lift coefficient provided by a slot acted in the Fowler flap's success relative to the Gouge flap, as did its natural tendency to retract itself in flight.[8]
Shorts themselves did not use the Gouge flap on their next project, theShetland, preferring the use of slotted flaps on this large seaplane.[10]
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