Shorts Mayo composite - Shorts S.20 and S.21

[Guest Glenn]

Tests demonstrated that an Imperial Airways Empire flying boat could only achieve a crossing of the Atlantic if its entire payload consisted of fuel. Knowing that an aircraft could fly at far greater weight than its takeoff weight, Robert Mayo proposed a solution in the form of a composite unit. The concept was for a small, heavily laden mail plane to be carried to operational altitude and launched by a larger 'mother' aircraft.

 

The British Air Ministry and Imperial Airways both accepted the proposal and jointly contracted the Shorts company to design and build such a composite unit. A slightly modified Empire flying boat, an S.21, named Maia, formed the lower parent unit. A Short S.20, Mercury, formed the upper long-range unit. This was a new design, a high-winged twin-float seaplane with four Napier Rapier H engines of 340 hp. It had a cruising range of 3,800 miles (6116 km) with 1,000 lb (454 kg) of payload.

 

The first flight involving an airborne separation took place on 6th February, 1938. After more test flights, the Mercury was air-launched over Foynes on 21st July, 1938, to fly non-stop to Montreal, Canada, in 20 hours and 20 minutes, a distance of 2,930 miles (4715 km), with 600 lb. (272 kg) of mail.

 

On 6th October, the Mercury established a long-standing record for an unbroken seaplane distance flight from Dundee to the Orange River, South Africa (5,997 mls / 9652 km).

 

The outbreak of war ended further developments. The Mercury was broken up at Rochester, and the Empire Maia was destroyed by enemy action in May 1941. Imperial's Empire flying boats were also used in early in-flight refuelling tests on trans-Atlantic flights in 1938-1939.

 

 

 

[siznaudin]

" a high-winged twin-float seaplane with four Napier Rapier H engines of 340 hp."

 

A not-so-good quality shot of a Rapier engine in the Shuttleworth collection.

 

16 cylinders "H" configuration and lots of revs & noise. A Halford design and he maxed out with the 24 cylinder Sabre. Napier sure specialised in complex motors .....

 

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