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Aviation History
1925
1925 - 0066.PDF
FEBRUARY 5, 1925 NEW DE HAVILLAND AIR LINER D.H.54, with Rolls-Royce "Condor," to Carry 14 Passengers AMONG the new commercial aeroplanes planned for 1925and now nearing completion, is the 14-passenger de Havil- land 54, which is to be fitted with a single RoUs-jtoyce" Condor " engine. This machine, the construction of'wnich ~fg"&9pf&tt9fmto be completed in about a month's time, is atypical de Havilland in its general lines, and might be described briefly, although not very accurately, as an " over-grown D.H.34." The general lay-out and many of the con- structional features are the same, but a closer inspectionreveals certain not inconsiderable differences. The general arrangement drawings published on the nextpage show the lines of the D.H.54, from which it will be seen that the machine is a normal two-bay biplane, withthe top plane straight and the lower set at a considerable dihedral angle. A feature of the D.H.54 will be the pro-vision of camber gear similar in principle to that first tried out on the type D.H.50 with such success. This gear, itmay be recollected,, consists in a hinged trailing edge pulled down by the action of springs and rising under increasedair pressure with increase in speed. The gear is entirely automatic in action as regards the variable camber function,but the flaps are divided, the outer portions retaining their differential movement and aileron action. The advantageof this flap gear is two-fold : it reduces the stalling speed considerably, and, what is almost of as great importance or possibly 14, passengers. The roof structure shows curvedbeams of built-up box section, and even under these beams the head-room is about 6 ft., while between the beams thedistance from floor to roof is some 6 in. more. The per- manent seats are arranged in three rows, two close togetheron one side and a single row on the other, with a narrow gangway running between. Behind the permanent seatsland against the rear wall of the cabin, is another spare seat with room for two passengers. Aft of the cabin is a largelavatory with the usual fittings. The door to the cabin is placed on the starboard side, and provision is to be made formaking a watertight joint between door and door-frame, so that in case the machine should be forced to alight on thesea, it will, it is expected, keep afloat for many hours if need be. It may be recollected that experiments were carriedout at Felixstowe last year with a D.H.18 in order to deter- mine how long a land machine with its cabin made water-tight would remain afloat. The D.H.54 will incorporate the experience thus gained. One of the difficulties of preventing an aeroplane fromsubmerging on alighting on water is that the undercarriage usually causes the machine to nose over, so that a fairamount of water gets into the cockpits and cabin. In "the D.H.54 this will be guarded against by arranging the under-carriage so that it, or at any rate part of it, can be dropped EEEEEEEE a s E IS m E E E E E E S S S E E EH The D.H.54 Com-mercial Aero- plane (R o lls-Roy.ce " CotuW' Engine) : ""'thefuselage nearing completion in theStag Lane shops. for a passenger machine, it allows of approaching the aero-drome with the fuselage practically horizontal, because the effect of the camber gear is to increase the angle of incidenceas well, so that with the tail down but a few degrees the wings are at the angle of maximum lift. There may be athird and less obvious advantage with the sprung flaps in coming out of a stall. Certainly, in the D.H.50, the dropis very small before the machine flattens out after a stall, and it is thought that the D.H.54 may to some extent havethe same characteristics. Constructionally, the D.H.54 follows previous de Havillandpractice m that the fuselage is a ply-wood-covered structure devoid of wire or tie-rod bracing. In the new machine,however, a departure from usual practice is to be found in that the fuselage is in two sections, so as to facilitateground transport. The joint in the fuselage occurs just aft of the cabin door, and actually the two spare seats andthe lavatory are in the tail portion of the fuselage. The joint is in the form of bolts through the longerons, withfish-plates inside and out. Each portion is a complete structure in itself, and the joint between the two portionsis covered with a fabric strip so as to make the fuselage water- tight—at any rate, the cabin portion of it and the first twobays aft of the joint, at the end of which is a watertight bulkhead. The rear portion of the fuselage is provided in each baywith large openings in the bottom, the object of which is to give access to the interior for purposes of inspecting thestructure. In actual use these openings will be covered over with doped fabric. Unusual head-room characterises the main cabin of theD.H.54, in which there will be seating accommodation for 12, when the pilot realises that a forced descent on the wateris unavoidable. This is accomplished as indicated in the accompanying sketches. The undercarriage, which is of theusual De Havilland Vee-type, except that the shock-absorbing gear is in the form of rubber blocks working in compressionand incorporating oleo damping gear, has its front legs cross-braced in the usual way, but the rear bay has no suchbracing. At their upper ends the rear legs are attached to the lower longerons by means of a substantial bolt, andthis bolt can be withdrawn by the pilot by means of the mechanism shown in the sketch and a lever in the cockpit.When the bolt is withdrawn the undercarriage is free to drop, and in so doing the hook attachment of the axle tothe front chassis struts allows the former to fall free, the front struts and their bracing remaining in place on tlu-machine, but swinging free so that on impact with the water they will be forced back and up against the bottom of tntfuselage. It is not thought that the presence of these struts will cause any appreciable tendency to nose over. The cabin of the D.H.54 is lighted by large windows inthe side, and heating and ventilation has been arranged for, hot air from a muff around an exhaust pipe being admittedthrough a diffuser near the floor, and fresh air, forced in by a scoop placed in the roof, being admitted through anotherdifiuser placed at head level. The amount of hot and cold air admitted can be regulated by the passengers themselves,a regulator being placed on the front wall of the cabin. Emergency exits are provided in the roof, and take the formof circular openings covered with fabric. The pilot's and navigator's cockpit is situated ahead'ofthe top plane, between it and the engine, and as the pilot's seat is raised and the coaming around it forms a " hump,"
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