Later than intended, but here's the story of the GAL.41.
In 1938, following the Cadman report of 1937, into the then current state of British civil aviation, the Air Ministry issued specifications S,14/38, and S.15/38 for a 'modern' long and medium range airliner respectively.
Responding to S.15/38, General Aircraft proposed the GAL.40, an advanced, four engined airliner with constant speed propellers, fowler flaps, and a tricycle undercarriage. Two versions were proposed, the GAL.40, with four Hercules, and the GAL.40A, with Merlins.
Since the aircraft was to incorporate pressurisation, then a new technology, it was decided to build a test-bed aircraft, the GAL.41. This was basically a modified ST.25 Monospar Universal, the existing wings, tail, engines and undercarriage being retained, the fuselage being replaced by a new one incorporating the pressure cabin.
The 'boiler-type' cabin was made from high strength Alclad alloy, 10' long, 5' in diameter, with hemispherical ends. The Alclad was rivetted together, with a strip of rubber material in the joints to act as seal. Acces was via a rubber sealed, inward opening wooden door. Pressurisation was to be maintained by an auxilliary engine driven centrifugal supercharger type blower, mounted in the aircraft's nose. Design cabin pressure was 1 atmosphere, 14 lbs/sq.in., at a height of 13,000'
During the initial pressure tests, with cabin under low pressure to test for leaks, so many of the fasteners did so that the cabin made a noise 'like a concert organ'. This resulted in the cabin's designer, one Jack Finnimore, clambering over the cabin's exterior with a bucket of soapy water and brush, checking each rivet in turn for leakage.
On May 11th, 1939, the GAL.41 made it's first flight, powered by two 95hp Pobjoy Niagra III radials.THe cabin door was left off to provide for an emergency exit. Following early test flight the wing root fairing was revised, to reduce turbulent airflow.
Following prolonged testing and development, the pressure cabin was made to function properly, though as far as is known, it was never tested at pressures higher than 7 1/2 lb. sq. in.
Early in the aircraft's existance, the RAE were very keen to acquire it for research purposes, but by the time the cabin was developed to sufficient degree, the RAE had apparently lost interest, transferring their attention to the pressurised Wellington variants. It is not known with certainty when the GAL.41 stopped flying, but it's pressure cabin was not scrapped until 1947.
Of course, following the outbreak of war, S.15/38 was cancelled, and the GAL.40 never left the drawing board...
Source :- 'Aeroplane Monthly ' December 1990, pp.734-737
cheers,
Robin.
