M.Simons The World's Vintage Sailplanes 1908-45
THE AIRSPEED TERN
A. Hessell Tiltman and Nevil Shute Norway, who had worked together on the design of the Vickers airship, R 100, under Barnes Wallis, decided in 1930 to set up a new company to build aircraft. They established the firm, Airspeed
Ltd, with a workshop in an empty bus depot in York. Their first project was a high performance sailplane.
The Airspeed Tern was far in advance of any other British sailplane design of that time. It had a 15.24 metre (50 ft) span cantilever wing, but instead of the usual German single-spar construction, it was built along orthodox powered aircraft lines with two spars, cross-braced. The thin plywood covering ahead of the front spar was intended only to give a smooth entry to the aerofoil, and took no torsional loads. The rest of the surface was fabric. The profile was Goettingen 549, as on Kronfeld’s Wien. There were no spoilers or airbrakes. Only the outer panels of the wing were detachable, the 1.5 metre wide centre section being built integrally with the fuselage. Rigging was quick and easy, the ailerons connecting automatically as the wings were put on. The tailplane and rudder were fabric covered and had the distinctive outlines that were to become characteristic of Airspeed designs.
The fuselage was large, with plywood covered belly and sides, the upper decking ahead of and behind the wing being fabric covered over light stringers, very much like the construction of contemporary biplanes.
Only two Terns were ever built and only one seems to have done much flying. A third was started but never completed by Airspeed, who later sold the parts to the Dart Aircraft Co at Dunstable. Soon after completion the prototype was soared by Carli Magersuppe, a German pilot then touring the country with Kronfeld at the invitation of the newly formed British Gliding Association. He flew 13.4 km, soaring along the cliffs from Ravenscar to Scarborough, and set a height record, for an English sailplane, of 250 metres. In spite of the attendant publicity, buyers did not come forward quickly. The only aircraft sold went to a group from the Southdown Club and it participated in the Balsdean gliding meeting held by the BGA east of Brighton on October 1931. In the following year, E. H. Mole borrowed the other Tern from Airspeed and with it tried to break the British duration record. He succeeded in setting a height record of 440 m.
The Southdown Tern attended most of the British National Competitions from 1932 onward, but never distinguished itself. Potentially, the Tern was a fine sailplane and it must be concluded that it was ahead of its time in England. It was the glider pilots themselves who were not yet capable of using such an aircraft fully.
Post war, the remains of the two Terns, the Southdown example and the one completed by Dart Aircraft, were purchased by Andy Coulson and one serviceable aircraft was made from the two, with some modifications, but after resale to a group of RAF pilots, nothing more was ever heard of it.
Tern: Span, 15.24 m. Wing area, 18.7 sq m. Aspect ratio. 12.44. Empty weight. 101 kg. Flying weight, 181 kg. Wing loading, 9.8 kg/sq m.
Flight, September 1931
THE "TERN" GLIDER
A NEW HIGH EFFICIENCY GLIDER. - Airspeed, Ltd., of Piccadilly, York, have recently constructed the "Tern," a glider which promises to uphold the prestige of English aircraft designers in this particular market. Mr. N. S. Norway and Mr. A. Hessell Tiltman are the joint Managing Directors, and Mr. Norway is primarily responsible for the design. As will be seen from the photographs, the glider is of the full cantilever type, with a high aspect ratio and a span of some 50 ft. It has already performed very creditably in the hands of various pilots, both English and German, all of whom have been loud in its praises. The photographs show various parts of the "Tern" under construction; that of the wing depicts very clearly the Warren girder drag bracing, so arranged as to provide exceptional torsional stiffness. This bracing consists of two flanges separated by the full depth of the main spar, which is considerable, since the wings are of cantilever construction joined by spruce lattice members. As a further help towards this stiffness and also as a safeguard when handling the machine, the whole of the leading edge is covered in three-ply wood. The ribs are simple and of the normal German construction, with glued three-ply gussets, and in fact German practice has been followed very largely in the wing, particularly in points like the trailing edge, the spring landing skid and many other details. In the cockpit arrangements and general make-up of the fuselage, British light aeroplane practice has been followed to a greater extent, thus this cockpit is roomy and particularly comfortable, and is fitted with a proper instrument board carrying an air speed indicator and cross level beneath a Cellon wind screen. The controls are on ball bearings, providing a light and positive control system.
A particular feature of the machine is the ease with which it can be dismounted and assembled. Each wing is detachable from the centre section by taking out two large main bolts, while the aileron controls connect automatically and need no attention whatsoever when dismounting the wings. In a similar way, each tail plane has the elevator permanently attached to it, and thus needs no attention as the elevator control connects itself when the tail plane is assembled. So simple is the whole operation that three men can completely rig and assemble the machine in less than 10 min. In a recent attempt Herr Magersuppe flew the "Tern" under record conditions for a distance of 84 miles from Ravenscar to Scarborough. After gaining a height of some 300 ft. he flew over the cliff edge in the rising current, but was unable to cross the town of Scarborough and had to land upon the beach, which he did quite safely.
The Tern flying at Dunstable.
THE "TERN": A new sailplane which has been designed and built by Airspeed, Ltd., of York. It is stressed for auto and aeroplane towing, the latter at 70 m.p.h. A detachable undercarriage is fitted for auto-towing.
This view of the Tern airborne at Scarborough shows the detachable undercarriage which made auto-towing easier.
Competing at Dunstable - the Tern, built by the Airspeed Company in their York days. Family resemblance is seen in the rudder.
A BRITISH SAILPLANE: Major Petre about to take off the "Tern." This full cantilever sailplane has an excellent view and has already made some record flights.
Major Petre in the capacious cockpit of the Airspeed Tern at Balsdean in 1931.
A begoggled Major Petre about to take off in the Tern at the meeting at Balsdean on the South Downs in October 1931.
With work in progress on the fuselage, the spruce framework and birch ply bulkheads and formers are still visible. Cockpit instrumentation consisted of an air speed indicator and a cross-level.
The wing of the Tern is seen under construction at York. The deep cantilever wing section with its Warren girder internal bracing and ply-covered leading edge “D”-box gave the structure exceptionally good torsional strength.
The convincing “flying" shot of the Tern model, above, is made more so by the inclusion of a scale pilot in the cockpit. Below the builder of the model, Peter Tiltman, gives us a plan view which is reminiscent of the de Havilland D.H.88 Comet.