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Aviation History
1946
1946 - 0030.PDF
FLIGHT JANUARY 3RD, 1946 The Folland E.28/40 Torpedo Reconnaissance Bomber with Many Unusual Features ACHANGE of Air Ministry policy in 1943 led to thestoppage of work on a most interesting project.The specification to which the machine was de- signed by Follahd Aircraft, Ltd., of Hamble, was E. 28/40, and was for a single-engined torpedo reconnais- sance bomber. The requirements of the specificatiop were very difficult. The machine was to carry a crew of three (pilot, observer/bomb aimer and air gunner/ wireless operator), torpedo, bombs, power-operated gun turret, full navigation and night-flying equipment, the usual pyrotechnics, arrester gear for deck landing, and have a range of 800 miles. All this on a single Bristol Centaurus III engine! Any firm might well have been forgiven for turning down the specification, but the Folland designers decided to '' have a crack at it." That the result was unorthodox is scarcely to be wondered at, but it seems rather a pity that the company was not allowed to complete the machine, from which some instructive lessons might have been learnt. The E.28/40 was a Jiigh-wing monoplane of all-metal construction, with fixed and "spatted" undercarriage. Its most unusual feature was that the wing was carried in trunnions so that its angle of incidence could be varied from 4 deg. to 79 deg. The latter angle was, of course, only to be used when the wing was folded. Variation of incidence in the flying range was from 4 deg. to 15 deg. The choice of a variable-incidence wing was dictated by various considerations. For one thing, the amount of equipment that had to be carried was such that, with the limits of wing span and area prescribed by carrier operation, a wing with very pronounced high-lift charac- teristics had to be used. Leading-edge slots and trailing- edge flaps required a high angle of incidence for maxi- mum lift, and to give the necessary ground angle with a fixed wing would have meant a very "stilty" under- carriage, which would have produced various troubles. By using the variable-incidence wing, not only were these avoided, but the further advantage accrued that the pilot could set his wings to the appropriate angle for take-off, landing or any flight condition, while maintaining the LENGTH - 44;t. SPAN - 52ft. 6in (18ft. folded.) fuselage at an attitude which would give him the best possible view. Variable Incidence and Area There is, of course, nothing new in variable-incidence wings, but to the best of our knowledge the Folland E.28/40 is the only modern aircraft to incorporate this feature. Its wing had actually both variable incidence and variable area, for the trailing-edge flaps were of the type which, when lowered, extend beyond the main trail- ing edge. It was found that when the main wing flaps and leading-edge slots were opened to maximum lift, the tailplane stalled before the main wing. This difficulty was overcome by fitting leading-edge slats on the tail- plane. These delayed the stall until well after the main wing had stalled. The extra complications introduced by the need to vary the wing incidence were, of course, quite consider- able. The wing-spar incidence pivots were carried in spherical bearings, and the main spar was of the three-boom type, two of the booms lying approxi- mately under the upper skin, and the third boom just inside the lower skin. The upper booms formed the hinge joints, while, the lower boom carried the latch joint. The change of incidence was effected by electrically operated screw jacks. When the wings were at maximum incidence the bottom joints could be The spar was of three- boom type. Shown here is the folding hinge at the centre section.
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