| S.20 Mercury | |
|---|---|
 Image from a contemporary newspaper article, depictingMercury atopMaia | |
| General information | |
| Type | Transport seaplane carried to flight altitude by Short S.21 Maia |
| National origin | United Kingdom |
| Manufacturer | Short Brothers |
| Designer |
|
| Primary users | Imperial Airways |
| Number built | 1 |
| History | |
| Introduction date | 14 July 1938 |
| First flight | 5 September 1937 |
| Retired | 1941 |
| S.21 Maia | |
|---|---|
| General information | |
| Type | Flying-boat, launch aircraft for S.20 Mercury |
| National origin | United Kingdom |
| Manufacturer | Short Brothers |
| Designer | Arthur Gouge Robert H. Mayo |
| Status | destroyed by enemy bombing 11 May 1941 |
| Primary user | Imperial Airways |
| Number built | 1 |
| History | |
| Introduction date | 14 July 1938 |
| First flight | 27 July 1937 |
TheShort Mayo Composite was apiggy-back long-rangeseaplane andflying boatcombination produced byShort Brothers to provide a reliable long-range air transport service toNorth America and, potentially, to other distant places in theBritish Empire and the Commonwealth.
Short Brothers had built theEmpire flying boats which were capable of operating long range routes in theBritish Empire but could only attempt the trans-Atlantic route by replacing passenger and mail-carrying space with extra fuel.
It was known that aircraft could maintain flight with a greater payload than that possible during take-off. Major Robert Mayo, the Technical General Manager atImperial Airways, proposed mounting a small, long-range seaplane on top of a larger carrier aircraft, using the combined power of both to bring the smaller aircraft to operational height, at which time the two aircraft would separate, the carrier aircraft returning to base while the other flew on to its destination. The BritishAir Ministry issuedSpecification "13/33" to cover this project.
The Short-Mayo composite project, co-designed by Mayo and Shorts chief designerArthur Gouge, comprised theShort S.21 Maia, (G-ADHK) which was a variant of theShort "C-Class" Empire flying-boat, fitted with a trestle or pylon on the top of the fuselage to support theShort S.20 Mercury(G-ADHJ).[a][2][3]
Although generally similar to the Empire boat,Maia differed considerably in detail: the hull sides were flared and had "tumblehome" rather than being vertical as on the Empire to increase the planing surface (necessary for the higher take-off weights); larger control surfaces; an increase in total wing area from 1,500 sq ft (140 m2) to 1,750 sq ft (163 m2); the engines were mounted further from the wing root to clearMercury's floats and the rear fuselage was swept up to raise the tailplane relative to the wing. Like theEmpire boats,Maia could be equipped to carry 18 passengers.[1]Maia first flew (withoutMercury) on 27 July 1937, piloted by Shorts' ChiefTest Pilot,John Lankester Parker.[4]
The upper component,Mercury, was a twin-float, four-engine seaplane crewed by a single pilot and a navigator, who sat in tandem in an enclosed cockpit. It could carry 1,000 lb (450 kg) of mail and 1,200 imp gal (5,500 L; 1,400 US gal) of fuel. Flight controls, except for elevator and rudder trim tabs, were locked in neutral until separation.Mercury's first flight, also piloted by Parker, was on 5 September 1937.[5]
The mechanism that held the two aircraft together allowed for a small degree of movement. Lights indicated when the upper component was in fore-aft balance so trim could be adjusted prior to release. The pilots could then release their respective locks. At this point the two aircraft remained held together by a third lock which released automatically at 3,000 lbf (13,000 N). The design was such that at separationMaia would tend to drop whileMercury would climb.[6]
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The first successful in-flight separation was carried out from the Shorts works at Borstal, nearRochester, Medway, on 6 February 1938,Maia piloted by Parker andMercury by Harold Piper. Following further successful tests, the first transatlantic flight was made on 21 July 1938 fromFoynes, on theShannon Estuary, west coast of Ireland, toBoucherville,[7] nearMontreal,Quebec,Canada, a flight of 2,930 miles (4,720 km).Maia, flown by Captain A.S. Wilcockson, took off from Southampton carryingMercury piloted by CaptainDon Bennett.[b] As well asMercury, the launch aircraftMaia was also carrying 10 passengers and luggage.[8]Mercury separated from her carrier at 8 pm to continue what was to become the first commercial[c] non-stop East-to-West transatlantic flight by aheavier-than-air machine. This initial journey took 20 h 21 min at an average ground speed of 144 miles per hour (232 km/h).[9]
TheMaia-Mercury composite continued in use withImperial Airways, includingMercury flying toAlexandria, Egypt, in December 1938. After modifications to extendMercury's range, it established a record flight for a seaplane of 6,045 miles (9,728 km) fromDundee in Scotland toAlexander Bay, in South Africa between 6 and 8 October 1938.
Only one example of the Short-Mayo composite was built, the S.21 Maia with the registrationG-ADHK and the S.20 MercuryG-ADHJ. The development of a more powerful and longer-range Empire boat (theShort S.26), the increase in allowable all-up weights with the standard "C-Class", the further development ofin-flight refuelling and the outbreak of the Second World War combined to render the approach obsolete.Maia was destroyed inPoole Harbour by German bombers on 11 May 1941.[10]Mercury was flown toFelixstowe for use by320 (Netherlands) Squadron RAF, a unit of theRoyal Air Force formed from the personnel of theRoyal Netherlands Naval Air Service. This squadron was based at the time atRAF Pembroke Dock. When this squadron was re-equipped withLockheed Hudsons,Mercury was returned to Shorts atRochester on 9 August 1941 and broken up so that itsaluminium could be recycled for use in the war effort.[11]
On the Tay Embankment close to theRRS Discovery there is a bronze plaque attached to the seawall.[12] This commemorates the world record long-distance seaplane flight, at a location where the estuary and hills behind the take-off waters are seen. The plaque shows in raised relief the two aircraft still joined but reaching the altitude at which they would have separated. The plaque also contains wording including: - ″Commemoration of the 1938 flight of Captain Bennett from the Tay Estuary to South West Africa... The world record long-distance flight by a seaplane was achieved by the aircraft "Mercury", the upper component of the Short Mayo... The two experimental planes ...were built byShort Brothers forImperial Airways and designed to carry mail long distances without refueling... This tribute to the epic flight by Captain D.C.T. Bennett and First Officer Ian Harvey was unveiled by Captain Bennett's wife Mrs Ly Bennett and Lord Provost Mervyn Rollo on 4 October 1997.″
The concept also had an unusual legacy, since in 1976NASA needed to transport theSpace Shuttle between theKennedy Space Center andEdwards Air Force Base between each mission, and to get the craft airborne for gliding tests. Jim McLaughlin, Chief Weights Engineer for Boeing 747 program, who was assisting NASA with the SCA Program, was previously the Chief Weights Engineer for Short Brothers and had been involved in the development of the Mayo Composite design at Shorts, and reminded a NASA engineer of the concept which enabled NASA to modify a second-handBoeing 747 as thecarrier aircraft accordingly.[13]
Data from[14]
General characteristics
Performance
Data from[14]
General characteristics
Performance
Related development
Aircraft of comparable role, configuration, and era
Related lists
| External videos | |
|---|---|
 British Movietone Newsfilm footage |
| External image | |
|---|---|
 Sequence of photos taken during first public separation (at Flight PDF Archive) |
