Short Mayo Composite

https://en.wikipedia.org/wiki/Short_Mayo_Composite

The Short Mayo Composite was a piggy-back long-range seaplane/flying boat
combination produced by Short Brothers to provide a reliable long-range air
transport service to North America and, potentially, to other distant places in
the British Empire and the Commonwealth.

Short Brothers had built the Empire flying boats which were capable of operating
long range routes across the British 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 H. Mayo, the Technical General
Manager at Imperial 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 British Air Ministry issued Specification "13/33" to cover this
project.

The Short-Mayo composite project, co-designed by Mayo and Shorts chief designer
Arthur Gouge, comprised the Short S.21 Maia, (G-ADHK) which was a variant of
the Short "C-Class" Empire flying-boat fitted with a trestle or pylon on the top
of the fuselage to support the Short S.20 Mercury(G-ADHJ).

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 takeoff 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 clear Mercury's floats and the rear fuselage was
swept up to raise the tailplane relative to the wing. Like the Empire boats,
Maia could be equipped to carry 18 passengers. Maia first flew (without Mercury)
on 27 July 1937, piloted by Shorts' Chief Test Pilot, John Lankester Parker.

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 (456 kg) of mail and 1200 Imperial gallons 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.

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 lb. The design was such that at
separation Maia would tend to drop while Mercury would climb.

S.20 Mercury

Role
Transport seaplane carried to flight altitude by Short S.21 Maia

National origin
United Kingdom

Manufacturer
Short Brothers

Designer
Arthur Gouge
Robert H. Mayo

First flight
5 September 1937

Introduction
14 July 1938

Retired
1941

Primary users
Imperial Airways
RAF

Number built
1

S.21 Maia


Role
Flying-boat, launch aircraft for S.20 Mercury

National origin
United Kingdom

Manufacturer
Short Brothers

Designer
Arthur Gouge
Robert H. Mayo

First flight
27 July 1937

Introduction
14 July 1938

Status
destroyed by enemy bombing 11 May 1941

Primary user
Imperial Airways

Number built
1

The first successful in-flight separation was carried out from the Shorts works
at Borstal, near Rochester, Medway, on 6 February 1938, Maia piloted by Parker
and Mercury by Harold Piper. Following further successful tests, the first
transatlantic flight was made on 21 July 1938 from Foynes, on the Shannon
Estuary, west coast of Ireland, to Boucherville, near Montreal, Quebec, Canada,
a flight of 2,930 miles (4,714.4 km). Maia, flown by Captain A.S. Wilcockson,
took off from Southampton carrying Mercury piloted by Captain Don Bennett. As
well as Mercury, the launch aircraft Maia was also carrying 10 passengers and
luggage. Mercury separated from her carrier at 8 pm to continue what was to
become the first commercial non-stop East-to-West transatlantic flight by a
heavier-than-air machine. This initial journey took 20 hrs 21 min at an average
ground speed of 144 mph (232 km/h).

The Maia-Mercury composite continued in use with Imperial Airways, including
Mercury flying to Alexandria, Egypt, in December 1938. After modifications to
extend Mercury's range, it established a record flight for a seaplane of 6,045
miles (9,726.4 km) from Dundee in Scotland to Alexander 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
registration G-ADHK and the S.20 Mercury G-ADHJ. The development of a more
powerful and longer-range Empire boat (the Short S.26), the increase in
allowable all-up weights with the standard "C-Class", the further development of
in-flight refuelling and the outbreak of the Second World War combined to render
the approach obsolete. Maia was destroyed in Poole Harbour by German bombers on
11 May 1941. Mercury was flown to Felixstowe for use by 320 (Netherlands)
Squadron RAF a unit of the Royal Air Force formed from the personnel of the
Royal Netherlands Naval Air Service. This squadron was based at the time at RAF
Pembroke Dock. When this squadron was re-equipped with Lockheed Hudsons, Mercury
was returned to Shorts at Rochester on 9 August 1941 and broken up so that its
aluminium could be recycled for use in the war effort.

Specifications (S.20 Mercury)

General characteristics
Crew: 2 (pilot and navigator/radio operator)
Payload: 1,000 lb (454 kg)
Length: 51 ft (15.5)
Wingspan: 73 ft (22.3 m)
Height: 20 ft 3 in (6.17 m)
Wing area: 611 ft² (56.8 m²)
Empty weight: 10,163 lb (4,610 kg)
Loaded weight: 26,800 lb (12,156 kg)
Max. takeoff weight: 15,500 lb (7,030 kg)
* Normal composite launch weight: 20,800 lb (9,435 kg)
Record composite launch weight: 26,800 lb (12,156 kg)
Powerplant: 4 × Napier Rapier VI 16-cylinder "H-block" piston engines, 365 hp
(272.29 kW) each

Performance
Maximum speed: 212 mph (341 km/h)
Cruise speed: 195 mph (314 km/h)
Range: 3,900 mi (6,275 km)
Wing loading: 33.6 lb/sq ft
Extended range: 6,100 mi (9,815 km) (Cape flight)


Specifications (S.21 Maia)

General characteristics
Crew: 3
Capacity: 18
Length: 84 ft 11 in (25.9 m)
Wingspan: 114 ft (34.7 m)
Height: 32 ft 7½ in (9.94 m)
Wing area: 1,750 ft2 (162.6 m2)
Empty weight: 24,745 lb (11,224 kg)
Loaded weight: 38,000 lb (17,237 kg)
*Takeoff weight (composite): 27,700 lb (12,564 kg)
Powerplant: 4 × Bristol Pegasus XC radial engine, 919 hp (686 kW) each

Performance
Maximum speed: 200 mph (322 km/h)
Range: 850 mi (1,368 km)
Service ceiling: 20,000 ft (6,100 m)




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