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MEDWAY AIRCRAFT PRESERVATION SOCIETY Rochester Airport. Chatham. Kent. UK. info@mapsl.co.uk |
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Rochester Airport. Chatham. Kent. UK.
SHORT'S EXPERIMENTAL SHERPA
There
is no doubt that the Sherpa was a new concept in aero design. David Keith-Lucas
became the chief designer at Shorts after the war having been the chief aerodynamacist
for the company from 1940 until 1949. He had been instrumental in much of the
design of the SA.3 Sperrin bomber which lost out to the Vickers Valiant in coming
to operational service and it was after this setback that he began to take an
interest in the 'aero-isoclinic'wing. In this design he used a front fuselage
common to the Sperrin and a large fin but substituted the wing and horizontal
tail, the engines being buried in the wing roots similar to the Valiant. The first
project using this wing was called the PD.1, but this got no further than the
drawing board. The next design was called the SB.1 and was a glider that had wooden
wings and a metal stressed skin fuselage. It first flew on July 14 1951 after
a winch launch. Sixteen days later it was taken to 15,000ft by a Short Sturgeon
tug and the pilot, Tom Brooke-Smith, commented that he 'found the aircraft awkward
and tiring to fly on the tow but after release found it handled beautifully'.
Several further experimental flights were carried out by the glider before it
crashed giving its pilots some nasty injuries. After some thought it was decided
to fit engines to what was left of the SB.1 with the damaged aircraft being designated
the SB.4 Sherpa.
The wing was made in one piece and attached to the fuselage
at three points, its structure comprising mainly spruce and plywood with light
alloy in strategic areas. Part of it was also fabric covered. All this work was
undertaken as a private venture since no finance was forthcoming from the Ministry
of Supply. The rebuild eventually took two years before Tom Brooke-Smith made
the first flight with excellent results. With the registration G-14-1 and named
the Sherpa (this stemmed from the recent conquest of Everest and partly from Short
at Harland Experimental Research Prototype Aircraft), the wings and elevons were
little changed, the flaps were still pneumatic but the anti-balance tabs on the
elevons were now trimmed by an electric motor and gearbox which varied the fulcrum
position.
The Sherpa flew adequately within its permitted limits of 250kt and
5,000ft and normal level speed varied from 117mph to a flat-out speed of 170mph.
©Robin J Brooks - MAPS.
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