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Aviation History
1948
1948 - 1631.PDF
SEPTEMBER 30TH, 1948 FLIGHT .409 HICH-LIFT RESEARCH Youngman - Baynes Air- craft with Full - span Slotted Flaps J\ ou1 •*-•*• to GREAT deal of research has already been carried out on high-lift wing surfaces, and in order further 1 examine and test a full-span flap system, invented by Mr. R. T. Youngman, a research aircraft has been built by the Heston Aircraft Co., Ltd., to the design of Mr. L. E. Baynes, of the aircraft section of Alan Muntz and Co. This aircraft, which made a successful first flight on February 5th, is sponsored by the Ministry of Supply. The possibility of modifying a Proctor to carry the special wing was at first examined, but this proved impractical, and the Youngman-Baynes design built instead is a sturdy- looking low-wing cabin monoplane with slab-sided fuselage and rather large tail surfaces. Certain Proctor components have been incorporated, such as the windscreen, doors, tail wheel and some main undercarriage components. The undercarriage legs are somewhat longer than is usual to allow adequate ground clearance for the flap system when it is fully extended. The fuselage and tail units are of conventional ply-covered wooden construction, and the,, engine is a Gipsy Queen 32. The slightly tapered wings, of semi-high-speed section, axe of two-piece construction, their spars being bolted up to the lower fuselage members and joined, without centre section, at the aircraft centre line. Construction is of wood, with compressed-wood spar booms, spruce ribs and ply covering. However, the flaps are all of light alloy. This high-lift wing follows earlier development work initiated by Mr. Youngman, and represented by the high- lift and brake flaps embodied on the Barracuda, Fulmar, and Firefly. The present scheme is derived from a Fleet Fighter design put up to the Admiralty in 1943 to facilitate take-off and landing on the restricted decks of the small slow-speed c-cort carriers. The Youngman high-lift wing combines full-span retract- able aerofoil flaps and inset ailerons, with a second or auxiliary aerofoil flap spanning the inner portion of the wing. This arrangement provides the maximum possible lift coefficient consistent with the maintenance of lull aileron control at slow speeds. The flaps occupy all that part of the wing aft of the rear spar, which is at 0.5 C. From beneath the body the main flap extends to the wing tip and has a backward movement of 15 per cent of the mean chord. In the fully extended position the main flap in way of aileron (aileron neutral) provides a lift increment of 0.8 with the flap set at 15 deg to the main • wing chord. The deflection of a 0.15 C aileron +18 deg c 17 The wing of the Youngman-Baynes research aircraft. Control runs are shown in diagrammatic perspective, and the letters A, B, C, and D indicate main wing, full-span flap, part-span flap and aileron respec- tively. The same lettering is used on the small diagram of flap linkages. provides lift increments of +0.32 and —0.55 at a wing incidence of 16 deg. With the 0.20 C aileron fitted, the aircraft conforms fully with the specified requirements for lateral control at slow speed. It may be noted that thit very satisfactory result is achieved by relying more upon rearward flap movement than upon large flap deflections for lift increment over the outer portion of the wing. There is also the added advantage of a much smaller adverse yawing moment. - ; ..<-" Lift Nearly Doubled ' -;;:- " The auxiliary flap is 0.25 C and extends from beneath the body to the inboard tip of the aileron. It combines a backward movement of 7.5 per cent with an angular deflection of 45 deg relative to the main wing chord line. The combination of the main and auxiliary flap at 15 deg and 45 deg respectively provide a lift increment of 1.8. The overall lift increment for the complete aircraft assessed on the gross wing area flaps retracted is 1.5. Intermediate flap settings provide smaller increments at relatively high lift drag ratios for the take-off. Structurally the flap and aileron operating mechanism is noteworthy for its simplicity. The main flap is sup- ported by three shear links at its leading edge and one torque link under the body. The auxiliary flap is sup- Geometry of the Youngman flaps. Screw jacks operated electrically actuate the movement, and flap angles are governed entirely by the mechanical linkages.
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