Slingsby T.21 Sedbergh
Designed by F. N. Slingsby, this side-by-side two-seater was designed to meet the ATC's requirements for a simple dual control sailplane of medium performance and low price. The prototype, designated T21P, first flew in 1944 and had a wing span of 50ft 0in using the same wing section as the Grunau Baby, and with a removable nose upper deck section to give students the same exposure to the airflow as experienced in primary gliders. Structure: All wood frame, wing D-box and forward fuselage plywood covered, remainder fabric.
The first production version was the T21A for clubs and other civil customers, with the span increased to 54ft 0in, which first flew in April 1947.
The T21B (originally designated T28) was the version of the T21A, with fixed nose, ordered for the ATC and known as the Sedbergh TX Mk 1 in Service use, being named after the famous Yorkshire public school; this first flew in December 1947.
Altogether 121 civil T21As were built and 73 T21B Sedberghs for the ATC, plus 19 more T21Bs built under sub-contract by Martin Hearn Ltd, who had also built Cadets for Slingsby. Three more T21s were built outside – by the Midland Gliding Club, by Leighton Park School and by Mr J. Hulme, making a total, including upper surfaces.
Slingsby T21B Sedbergh
The forward portion of the fuselage back to the two main wing attachment frames is a wooden stressed skin structure, and the centre and rear portions are of fabric-covered girder construction. The tailplane is braced and the rudder and elevators fabric-covered. Landing gear consists of a large non-retractable monowheel with a nose skid in front of it, and a sprung tailskid. The two pilots sit side-by-side in an open cockpit with dual controls, and with two small windscreens ahead of them; the spoiler lever, cable quick-release and trimming controls are positioned on a console between the two pilots.
The Royal Air Force operated 92 T.21B’s (known as the Sedbergh T.X. Mk. 1) in its air cadet training program until the 1980’s. Approach control is accomplished only by upper surface spoilers. Most examples had open cockpits; a few were modified to incorporate a canopy (T. 21 C).
Sedbergh T.21 B
Wing span: 16.5 m / 54 ft 0 in
Wing area: 24.2 sq.m /260.5 sq.ft
Aspect ratio: 11.2
Airfoil: Go 535
Length: 26 ft 8 in
Empty Weight: 272 kg /600 lb
Payload: 204 kg / 450 lb
Gross Weight: 476 kg / 1050 lb
Wing Load: 19.6 kg/sq.m / 4.01 lb/sq.ft
Max speed: 105 mph
L/DMax: 21 @ 69 kph / 37 kt / 43 mph
Min sinking speed: 2.79 ft/sec at 38.5 mph
No. of Seats: 2
No. Built: 218