Made distinctive by its swept forward wing and the extensive area of its transparent canopy glazing, which extends back to the wing trailing edge, the T53 tandem two-seater trainer was designed by J. L.Sellars and was Slingsby's first all-metal type. The type is intended for initial or advanced training and the prototype, the T53A, made its first flight at Wombleton, Yorkshire, on 9 March 1967. It had tapered wings with camber-changing flaps with a range of 5° up to 15° down, ailerons of large chord and an all-moving tailplane. The first production version, the T53B, made its first flight on 28 March 1968, and had the cockpit moved forward, the structure redesigned and simplified, the flaps deleted and the all-moving tailplane replaced by a conventional tailplane and elevators; the aileron chord was also reduced and these changes resulted in lighter stick forces and a considerable saving in weight. The T.53B features two fixed tandem wheels and a swept- forward flapless wing of constant chord (the prototype T.53A had flaps).
Of light alloy stressed skin construction throughout, the T53C has two-spar cantilever shoulder wings with 3° forward sweep at the quarter-chord line as compared to the 5° 15' forward sweep of the T53B; the ailerons are mass-balanced and there are Schempp-Hirth air brakes in the upper and lower surfaces. The fuselage is a semi-monocoque and the cantilever tail unit has an internal spring-loaded trimmer. Landing gear consists of a non-retractable main wheel and nose wheel (or skid on the ATC variant), plus a tailskid; main wheel shock absorption on the T53C is by Armstrong damper units and there is an expanding caliper brake. The pilots sit under a sideways-hinging moulded flush Perspex canopy, and radio and an oxygen system can be fitted if desired.
The first T53B, XV951, was in RAF markings for air cadet training, and there were a number of modifications made to meet ATC requirements. These included fitting a nose skid in place of the standard nose wheel, to shorten the landing run; fitting a ground rapid-retrieve factility to improve utilisation in circuit training; fitting a performance retarding device for basic pilot training and making the main wheel spring-loaded. It was also envisaged that the ATC variant could be operated with open cockpits if the crew's comfort demanded. But in the end it was the T53C that was built in small numbers for the ATC, the variant incorporating the special ATC modifications being known astheT53C(M).
The C, which first flew in May 1970, had a revised and extended fin and rudder with extra area above the tailplane, no dorsal fin, a structurally redesigned wing, reduced aileron control loads resulting from the use of aileron servo tabs, a revised spring trim system and improvements in the cockpit layout, seating, ventilation and canopies; some extra equipment was carried and the all-up weight was increased.
The T53D project of October 1968 was a semi-aerobatic powered trainer version with a pusher engine installed on the port wing only, and a fuel tank in the wing leading edge, and the T53E was another project for a powered trainer version of the T53C.
Only 16 T53Bs and one more T53C (actually the last T53 converted) were built before the November 1968 fire at Slingsby's works put a stop to production, but the design was later acquired by Yorkshire Sailplanes, who had built three more as the YS.53 Sovereign by 1974. This differed from the T53B chiefly in having longer tail surfaces and a nosewheel instead of nose skid.
Yorkshire Sailplanes YS.53 Sovereign
Wing span: 17m / 55.5 ft 6 in
Wing area: 18.02 sq.m / 194 sq.ft
Aspect ratio: 15.9
Length: 25 ft 3.25 in
Height: 4 ft 7.25 in
Empty Weight: 354 kg / 780 lb
Payload: 226 kg / 499 lb
Gross Weight: 1279 lb / 580 kg
Wing Load: 6.59 lb/sq.ft / 32.19 kg/sq.m
Airfoil: Wortmann FX 61-184
No. of Seats: 2
L/DMax: 29 @ 89 kph / 48 kt / 55 mph
MinSink: 0.76 m/s / 2.5 fps / 1.48 kt at 50 mph
Max speed: 135 mph
No. Built: 21