MEDWAY AIRCRAFT PRESERVATION SOCIETY Ltd

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 aerodynamicist 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, the SB.1, was a glider with wooden wings and a metal stressed skin fuselage.  It first flew on July 14 1951 after a winch launch.  Sixteen days later, it was towed to 15,000 ft 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, causing nasty injuries to its pilots.  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.  This name stemmed from the recent conquest of Everest and also formed from the initial letters of Short at Harland Experimental Research Prototype Aircraft). 

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.  It carried the registration G-14-1 and was named  The wings and elevons were little changed and 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 250 kt and 5,000 ft and normal level speed varied from 117 mph to a flat-out speed of 170 mph.