Armstrong Whitworth A.W.52
Armstrong Whitworth Aw52 was the name for two different flying wing experimental aircraft that were developed in the 1940s in Britain. It was first a non-driving concept model ( AW52G ) constructed, followed by a twin- scale enlarged model ( Aw52 ).
History
The Nurflügelauslegung has some advantages over a conventional aircraft, so theoretically, the total resistance of the cell is only half as high. One of the essential disadvantages is the difficulty of controlling the transverse axis about vertical and transverse rudder is performed combining elevons. Because of the small lever arm the control surfaces must be designed to be relatively large.
Another approach to reduce the aerodynamic drag, the boundary layer control is quite special the destination, the flow around the airfoil to keep long as laminar as possible and so as to shift the transition point from laminar to turbulent flow conditions as far as possible along the tread depth to the rear, because the turbulent portion of the flow is responsible for the majority of the resistance profile.
To influence the boundary layer is generally characterized in that suction slots are provided on the surface or holes, through which the boundary layer is drawn, before it can be turbulent. Benefit primarily the control surfaces of the smooth flow. Through carried out during the war studies at a Hawker Hurricane with laminar flow, the sensitivity to contamination by insects, for example, was known. A newly developed wing was able to obtain the laminar flow over 60% of tread depth; The reduction of resistance to a normal leaf was in this case up to 50 %. However, after a relatively short time, the surface rough become destroyed the laminar flow.
If a flying wing combined with a Boundary layer control, particularly significant improvements in the aerodynamic drag can be expected. In the years after the Second World War, the possibilities of such designs have been the subject of studies in the UK. Coordinated the activities of the Tailless Advisory Committee, which was established by the Ministry of Supply. One of the companies included herein was Armstrong - Whitworth Ltd.. in Coventry.
Under the leadership of John Lloyd, a study of a jet-propelled flying wing airliner was started with a laminar profile. This interpretation meant that passengers and engines had to be housed in the wing and consequently the height of the passenger cabin dictates the wing thickness and hence the size of aircraft. The span would therefore have to be 80 to 90 T at least 49 m and the total weight.
The first draft of Armstrong Whitworth envisaged a Pfeilflügler with normal vertical tail, but without tailplane. AW50 as indicated, it should have a range of 36.6 m and a total weight of about 23 tonnes. The drive should consist of four Metropolitan - Vickers F.3 - turbofan engines. Since neither the Ministry of Supply, the company still wanted to tackle such a project without preliminary investigations themselves, they suggested a scaled-down version earlier than glider. However, this known as Aw51 construction with a span of 12.20 m was only just as the AW 50 realized.
Constructive developments of this discontinued proposals eventually led to Aw52. But even here, should help to clarify previously a reduced version as Glider, the basic problems of control, stability and handling. The construction work on this AW52G said machine began in May 1943, the construction was started in March 1944. The first flight took place on March 2, 1945 from Baginton Aerodrome (now Coventry Airport ) take in tow a Armstrong Whitworth Whitley. The following each half-hour flights from a release altitude of 6100 m confirmed the results of wind tunnel tests and the expectations in terms of stability and controllability.
The test flights of the machine with the RAF serial number RG324 extended over two years, after which it was placed at the entrance of Baginton Aerodromes and finally scrapped in 1950.
However, the development work at high speeds could be carried out only with a powered aircraft, one reason why the Ministry of Supply in late 1944 a contract for the construction of two test aircraft in accordance with the Air Ministry Specification E9/44. It is a twin-engine, all-metal aircraft was required in Nurflügelauslegung and twice that of the previous glider. The wings should use a laminar profile of the National Physical Laboratory, which could theoretically maintain the laminar flow up to half the depth of the surface for the first time. The setting angle changed from 1 ° 2 ' at the root of -2 ° at the wing tip. In order to obtain the required smooth surface of the wing should be made in two halves divided horizontally. The planking of a relatively thick Alclad sheet was clamped in a lesson and then almost set up the wing structure from outside to inside. The two halves were then bolted and the wing leading edge and trailing edge mounted separately. The deviations from the ideal curve should be so only 2/1000 inch.
A major problem with the design team led by John Lloyd was faced, was the tendency to premature stall at the wing tips in the use of swept wing layout. The remedy through slots in this area was ruled out, since thereby the desired laminar flow characteristics of the wing would have been lost. Instead, a boundary layer control procedures of the wing tips should include starting the entire span of the elevons. This was achieved by suction slots on the wing surface, which were arranged in front of the correctors. Theoretically, this should be delayed by the removal of the boundary layer in front of her turbulent transition point of the barn entrance. The slots were connected inside the wing and flaps in the engine inlet. When the throttle and when retracting the stick the flaps opened and automatically generated a suction force. In the case of A.W. 52G, the suction force was provided by wind- driven propeller on the legs.
The first A.W. 52 (RAF ID: TS363 ) conducted its first flight at the Aeroplane and Armament Experimental Establishment Boscombe Down from the airfield on 13 November 1947. The second copy ( TS368 ) flew nine months later on September 1, 1948 for the first time. Both aircraft were brought together at the Farnborough show in 1948. The flight performance of the design, however, remained below expectations; Lloyd came to the conclusion that laminar flow in a swept wing can not be maintained. Together with the low lift coefficient of about 1.6 with flaps extended services for the used engine power were clearly too low. Nene version reached 500 mph ( 800 km / h ), while the machine Derwent drive 80 km / h was slower.
On May 30, 1949 John Lancaster flew the TS363 at high speed flight, flapping wings when spread from the ends over the entire wing. This had uncontrollable oscillations about the transverse axis of rotation and the pilot escaped with the ejection seat. The second prototype began testing continues, but with a speed limit of 250 kt .. 1950, the machine was transferred to Farnborough, where further tests were carried out to wing sweep and laminar flow. The wing was able to achieve a laminar flow over 20% of tread depth again because of the two-year test strain only after extensive treatment. However, it was finally determined that the daily flight operations the necessary quality of the surface may not be kept permanently, after which further attempts were adjusted with the Aw52. The aircraft was scrapped in 1954.
Construction
A.W.52G
The tailless glider was built mainly of wood. The wing used the NACA 653 220 profile and was made in three parts: a central part with a swept- forward wing and a straight trailing edge and two outer sections with more pronounced wedge shape and trapezoid shape. The parts had a built from pine and plywood spar. The planking consisted Plymax in the plywood on Duralumin plates of thickness 0.711 mm or 22 swg (Standard Wire Gauge) was glued on.
The fin discs were arranged on the outermost ends of the wings. The control system already corresponded to the planned larger machine. The two crew members sat in the middle section behind the other under a streamlined hood. The tricycle landing gear was not retractable.
A.W.52
Because of the relatively small dimensions of the crew members could not be accommodated in the fuselage, but sat in a forced draft fuselage gondola, which jutted forward over the flying wing. The canopy was slightly offset to the right ( direction of flight). The two jet engines were housed in a largely integrated in the wing gondolas on both sides of the crew compartment. As the AW52G decreed the Aw52 a slotted Fowler flap along the entire trailing edge of the wing center section. The Bugradfahrgestell was retractable.
The first Aw52 with the RAF serial number TS363 was ( lb 5000 ) Shear powered by two Rolls- Royce Nene each, while the second copy ( TS368 ) two Rolls- Royce Derwent jet engines ( per 3500 lb thrust) were used. The fuel capacity of 1,700 gal was in eight tanks.
The control was carried out by elevons on the outer wing tips. Normal elevons act as elevators when they are moved in the same direction, or as ailerons in opposite directions actuation. Variant employed herein was modified so that trimming surfaces were attached to the trailing edge of the moving control surfaces, which have been referred to as " correctors ". The purpose of the hydraulically-actuated " corrector " was to provide a trim without impairing the ease of manually operated elevons. The correctors were associated with the Fowler flap control when the flap turned down down, and thus the trim buglastig changed, then the corrector to compensate for moving opposite to the top. Rudder and fins were provided externally as end plates on the wings at the tail root an anti -spin parachute was each housed in a fairing.