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Slingsby T 43 Skylark 3

  Probably the most successful of all the Slingsby designs were the Skylark series of high performance single-seaters, which won the World Championships in 1960 and set many national and international records; altogether ДальшеMore>>> 192 Skylark Mks 1-4 were built. The T37 Skylark 1, first of the series, was built for a lark, according to Mr F. N. Slingsby - hence its name - and was an experimental single-seater with a three-piece laminar flow wing of 45ft span, intended to test various lateral stability devices to determine the best type of lateral control surface for use with a laminar flow aerofoil; the wing was of NACA 63-/64-series section and had very effective air brakes but no flaps. The fuselage was based on that of the T30 Prefect, with a one-piece canopy, the length being 20ft 11 1/2in, and there was a main skid only plus a tailskid, no monowheel being fitted. The first of two prototypes made its maiden flight in March 1953, and only the two Mk 1s were built partly as this version had, for that time, a very high stalling speed. But it had proved sufficiently promising to be developed into the T37B (later T41) Skylark 2, the prototype of which first flew in November 1953. This had the wing span increased to 48ft and a new semi-monocoque elliptical cross section fuselage with spruce frames and plywood skin which increased the length to 24ft 6in; a fixed monowheel was introduced to supplement the nose skid, although this could be replaced by'jettisonable dolly wheels. The Mk 2 was of all-wood construction with plywood covering, like the Mk 1, and it also had a three-piece laminar flow wing. Its good performance made it popular both with clubs and private owners, and a total of 61 Mk 2s were built, plus two more from Slingby-supplied kits; about half this total were exported, production of the Mk 2 ending in 1962.
  The Mk 2 was followed by the T43 Skylark 3 single-seater, an enlarged and developed version suitable for Open Class competition; this had the wing span increased by nearly 12ft to 59ft 8 1/4 ft (18.19m) and the aspect ratio to 20.5, while the tail surfaces were enlarged, just as the Mk 2's tail unit had been larger than the Mk 1's. The prototype Mk 3 first flew in July 1955 and there were several sub-types; altogether 65 Mk 3s of all variants were built, and a Skylark 3B flown by the Argentine pilot Rudolfo Hossinger won the Open Class in the 1960 World Championships in Germany, a historic instance of a British type beating the Germans on their own ground. The Skylark 3A, of which seven were built, was the original Mk 3 variant with a length of 24ft 9in, and the Mk 3B had the cockpit moved forwards by 3in to compensate for the rearward movement of the cg caused by the larger tail; the elevator mass balances were also repositioned and the 3B's length was 25ft. Altogether 24 Mk 3Bs were built, and both 3As and 3Bs later had the all-up weight increased to 830lb by a retrospective modification. The Mks 3C and 3D, two examples of each of which were built, were the same as the 3A and 3B respectively but had the wing spars strengthened to meet BCAR and ARB requirements. The Skylark 3E was a 'one-off' experimental version (serial BGA 480) with outer wings of a different NACA 64-series section and reduced chord ailerons, but was otherwise the same as the Mk 3B; it was later converted back to this standard. The Mk 3F was the same as the 3B but had geared tabs added to the ailerons, a modified tailplane and elevator plan form of greater span, and an all-up weight of 830lb; 25 of this variant were built plus five more constructed from kits supplied by Slingsby. Last variant was the Skylark 3G, which was the same as the 3F but with increased span ailerons of reduced chord with the geared tabs removed; four Mk 3Gs were built.
  All the Mk3 variants had the same all-wood construction with plywood covering as the Mk 2, and a similar high-set laminar flow three-piece cantilever wing of spruce and plywood with air brakes in the upper and lower surfaces. The wing has a main spar and a light rear spar to carry the ply-covered ailerons, and is plywood-covered to the rear spar with a fabric-covered trailing edge. The wooden cantilever tail unit has a plywood-covered fin and tailplane and fabric-covered rudder and elevators. The landing gear is very similar to the Mk 2's, with a tail bumper as an alternative to the tailskid, and the monowheel can be replaced by jettisonable dolly wheels. The pilot sits under a one-piece blown canopy which hinges sideways to open, and he is provided with an adjustable seat and rudder pedals.


Data: Skylark 3B
Span: 59 ft 8 1/4 in
Length: 25 ft 0 in
Height: 5 ft 9 in
Wing area: 173.3 sqft
Aspect ratio: 20.5
Empty weight: 547 lb
Max weight: 830 lb
Max speed: 134 mph
Min sinking speed: 1.84 ft/sec at 40 mph
Best glide ratio: 36:1 at 46 mph



Slingsby T 50 Skylark 4

  Although developed from the later versions of the Skylark 3, the Skylark 4, with its new and shallower fuselage with the pilot sitting in a semi-reclining position, and its new outer wings and ailerons giving a wing span of exactly 18m (59ft 0 1/2 in), was almost a new design. It was developed through the Slingsby T47, a version of the Skylark 3 projected in December 1958 with a span of 20m (65ft 7in) created by increasing the span of the constant chord centre section; the wing area was now 193.45sq ft and the aspect ratio 22.2. The Skylark 4 has the wings faired directly into the top fo the fuselage without the builtup pylon-type structure behind the cockpit of the Mks 3 and 2, the height of the wing being 9in lower than the Mk 3's. The wing is very similar to that of the 3G but has modified wing roots, and the main spar has been strengthened to avoid the Mk 3's tendency for the wing tips to be deflected downwards at high speed. The prototype Skylark 4 first flew in February 1961 and altogether 63 Mk 4s were built, plus three more constructed in New Zealand by Mr Fred Dunn from kits supplied by Slingsby. The Mk 4 was successful in competitions, and scored two notable successes in 1963 when examples of this version won both the US and Canadian National Championships. Structurally the Mk 4 was very similar to the Mk 3, with a light rear spar carrying the ply-covered ailerons, the wing being plywood-covered to the rear spar and with a fabric-covered trailing edge; the air brakes in both upper and lower surfaces are on the 50% chord line. The wooden fuselage is a semi-monocoque of elliptical cross section with a glassfibre-covered nose and plywood covering for the remainder. The pilot sits under a moulded Perspex canopy that is larger than the Mk 3's, and likewise hinges sideways to open. Landing gear consists of a non-retractable Dunlop monowheel with rim brake, a rubber-sprung nose skid and a tail bumper. The fin and tailplane are plywood-covered and the rudder and elevators fabric-covered, with a trim tab in the starboard elevator.


Span: 59 ft 7 in
Length: 25 ft 1 in
Height: 5 ft 3 in
Wing area: 173 sqft
Aspect ratio: 20.5
Empty weight: 570 lb
Max weight: 830 lb
Mex speed: 135 mph
Max aero-tow speed: 80 mph
Min sinking speed: 1.74 ft/sec at 43 mph
Best glide ratio: 36:1 at 47 mph



Slingsby T 51 Dart

  This high performance Standard Class single-seater was the last Slingsby type of conventional all-wood construction and the last to be designed under Mr F. N. Slingsby's direction. The prototype Dart 15 first flew on 26 November 1963 and the Dart 15 - known as the 15R when fitted with a retractable monowheel - was the initial Standard Class version with 15m span shoulder wings, which were cantilever single-spar spruce structures with a birch plywood leading edge torsion box and a fabric-covered rear portion; there were air brakes at the 50% chord line and the plain ailerons were plywood-covered. The wing spars were initially entirely of wood, but were later changed to box spars of mixed wood and light alloy construction with Redux bonding when this type of spar was introduced into the Dart 17 in 1965. Wing root fillets like those on the Dart 17 were also fitted at this time and later production Dart 15s had an all-metal tailplane. Altogether 50 Dart 15s were built, plus five more constructed from kits supplied by Slingsby, four of these being built by Mr Fred Dunn in New Zealand; the price of a Dart 15 in July 1964 was £1,425. This version scored a number of competition successes: one flown by G. Burton gained 5th place in the Open Class at the 1965 World Championships at South Cerney, Gloucestershire, and the Dart 17 prototype, flown by H. C. N. Goodhart, took 7th place in this event. The Dart 15 was awarded the OSTIV Design Prize at these 1965 Championships. In League One of the 1967 British Championships, Darts came 1st and 2nd and took eight more of the first 20 places.
  But the Dart 15 in its wooden-sparred form was really too heavy and did not really have the performance for soaring in average British conditions, and this led to the Dart 17 - or 17R with retractable monowheel - with the span increased to 17m, this now being the Open Class version; the prototype 17 first flew in November 1964 and the price of a 17R was £1,950 in August 1966. Altogether 44 Dart 17s and 17Rs were built, plus four more built from kits in New Zealand by Fred Dunn. There was also one Dart 15/17, G-ATOE, which had detachable wing tips for changing the span from 15 to 17m, and two examples of the Dart 15W were built, this being a special version for the British team in the 1968 World Championships in Poland. The 15W had a new Wortmann wing section instead of the previous NACA 64-series aerofoils, a revised canopy shape and cockpit interior; the 15W first flew at Lasham on 29 March 1968 and after the Championships both 15Ws were converted to Dart 17Ws with the 17m span wing, first flying in this form on 3 May 1969, and both were later fitted with retractable monowheels, in which form they were designated Dart 17WR.
  Most Dart 15s and 17s had the retractable wheel, which became available as an optional fitting at the end of 1965, and this allowed a change of wing incidence, thus avoiding the Dart's tail-high attitude when flying at high speeds. All-metal tailplanes were also fitted to the later production Dart 17s. With the original wooden spar wing, flexure was caused when the Dart 17's air brakes were extended, and so to reduce this a new box spar with light alloy booms Redux-bonded to wooden webs was introduced, the first Dart 17 with this spar being rolled out in April 1965. At the same time the aileron span was increased by 11 3/4 in, and new wing root trailing edge fillets were added to reduce drag. On the Dart 15 the new spar resulted in a saving of 45lb in tare weight over the wooden-sparred version.
  The Dart's fuselage is a semi-monocoque spruce structure of elliptical cross section, the cockpit section being covered with glassfibre and the remainder with birch plywood. The pilot sits in a semi-reclining seat under a sideways hinging moulded Perspex canopy with clear vision panels, and the cockpit is very similar in size and general arrangement to the Skylark 4's. The fuselage is shallower than the letter's because the flying controls run along the sides of the cockpit instead of under the pilot's seat. The fin and rudder are of spruce with glassfibre leading edges, the rudder being fabric-covered, and the light alloy stressed skin tailplane, previously wooden, is an all-moving surface with anti-balance tabs. As well as the monowheel, which has an expanding brake, there is a short forward skid under the nose and a tail bumper fairing.


Data: T51 Dart 17R
Span: 55 ft 9 1/4 in
Length: 25 ft 5 in
Wing area: 149.3 sqft
Aspect ratio: 20.4
Empty weight: 525 lb
Max weight: 816 lb
Max speed: 136 mph (in smooth air)
Min sinking speed: 1.97 ft/sec at 46 mph
Best glide ratio: 36:1 at 51.5 mph