Short Mayo Composite
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Short Mayo Composite

Carefully-conducted tests had proved that an Imperial Airways' Empire flying-boat could achieve a transatlantic crossing only if its entire payload consisted of fuel. Since it is well known that an aircraft can be flown at a much greater weight than that at which it can take off from the ground, Robert Mayo proposed that a small heavily loaded mailplane be carried to operational altitude above a larger 'mother plane' and then released to complete its long-range task. The proposal was accepted by the Air Ministry and Imperial Airways, which jointly contracted Shorts to design and build such a composite unit. The Short S.21 Maia, the lower component, was a slightly enlarged and modified version of the Empire boat; the Short S.20 Mercury, the upper long-range unit, was a new high-wing twin-float seaplane with four 254kW Napier Rapier H engines giving a cruising range of 6116km with 454kg of mail.

The first airborne separation took place on 6 February 1938, and after a number of experimental flights Mercury was air-launched over Foynes on 21 July to fly non-stop the 4715km to Montreal in 20 hours 20 minutes with a 272kg payload. On 6 October 1938 Mercury was launched over Dundee to establish an as-yet unbroken non-stop international seaplane distance record of 9652km to the Orange River, South Africa. However, the outbreak of war ended experimentation, and Mercury was eventually broken up at Rochester and Maia destroyed by enemy action during May 1941.

Ian Qusklay, 30.01.2017

In 1938 I was an 8 year old schoolboy at The Convent,now Lawside school, which was situated at the foot of the Law hill in Dundee.Together with a classmate I sneaked out of school and climbed to the top of the hill to see the Mercury-Maia take off from the Tay and head for South Africa.The nuns made us pay for our sins but it was well worthwhile.

George Dickinson, 14.05.2015

Further Internet searching has possibly (probably?) given me the answer. The East Anglian Film Archive has a film of the opening of Luton airport on 16 July 1938. It includes a fly-over by the Composite, including a separation. The question is, did it fly over Bushey/Watford en route to Luton? Any confirmation, please?

George Dickinson, 14.05.2015

Just another point about this sighting, the Composite was flying very low, maybe a couple of thousand feet, so recognition was easy and infallible. Also, a low flight path would match a journey between consecutive displays at Hendon and Hatfield.

George Dickinson, 14.05.2015

From mid-1937 I lived in Bushey Hall Road, Watford, not far from the "5 Arches" where the LMS Railway crossed the River Colne. One day I saw the Short-Mayo Composite flying northwards right over our house. On "Flightglobal/Archive" on the Internet, I have just found a copy page from "Flight" magazine for 26 May 1938, giving outline details for the "Empire Air Day" to be held on 28 May. There were to be several appearances by flying boats, all of them at or near the coast (RAF flying boats?), except three, these being at Hornchurch, Hendon and Hatfield (civil). Could these three have been fly-overs by this aircraft, in which Bushey/Watford would have been under the route between Hendon and Hatfield? If this is not the explanation for the sighting, is there any other, please? Does anybody know? I would like to settle this in my mind, if possible!

Dr M Andrews, 29.07.2014

There is a painting and statue of the composite at Dundee Airport presented in 1994 to commemorate the connection between the aircraft, Donald Bennett (Pathfinders) and Dundee

john kinneaar, 25.09.2013

wher can i get copies of these aircraft to make a model?

Neil Farley, 28.06.2013

Very interested to here all your comments. I run the Imperial Airways website (in fact the text and picture above comes from it). We are 2 months away from opening the world's first dedicated Imperial Airways museum and would love to make contact and hear from anyone with reminiscences or connections with anything to do with the airline.

J Robinson, 01.02.2013

Additionally to my comment in January 2011 I now have research further into Imperial Airways documents and other sources which show clearly that my father was infact the only Inspector (Engines & Airframe) on the Maia / Mercury project.
He was noted as being at Foynes weeks before both aircraft arrived and returned aboard Maia - each aircraft arrived separately.
Prior to test flights from different stations both aircraft arrived separately and Mercury was lifted onto Maia - the engineering crew required for pre flight checks and lifting were always aboard Maia as were various officials.
My father was between 1937 and 1939 part of Major Mayo's Development Department whilst he was General Manager (Technical) with Imperial Airways.
My father had also between November 1936 and February 1937 been Engineering Inspector (in-charge) at the new Hythe flying boat base.

Betty Garfield, 22.05.2011

I lived in Wormit,Woodhaven was small area of the village From there all supplies etc were taken boat by boat. enterprising boat owner from Woodhaven took passengers round the planes.We saw practise flights take off and the actually take off in October

Betty Garfield, 22.05.2011

I lived in Wormit,Woodhaven was small area of the village From there all supplies etc were taken boat by boat. enterprising boat owner from Woodhaven took passengers round the planes.We saw practise flights take off and the actually take off in October

J Robinson, 21.01.2011

My father was a Engines Inspector with Imperial airways seconded to Short Bros. during build of Maia/Mercury and was also on board Maia through the trails period am still clarifying if he was onboard during the World Record Flight.

Lester, 21.09.2008

There is some amazing footage of this aircraft available at

Dr. Eric Thomas, 24.09.2007

I saw the Maia-Mercury composite airborne after taking off from the RAF base at Pembroke Dock in the summer of 1938 and suspect that it had refuelled there during a test flight or even prior to the release of Mercury over Ffoynes on its historic flight to Montreal in July of that year. Does anyone out there have any information about this remarkable aircraft's visit to Pembroke Dock? Would like to hear from you.

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