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Aviation History
1957
1957 - 1594.PDF
682 FLIGHT This wing permits the use of relatively conventional ailerons, butit has necessitated the adoption of an aerofoil of unusual profile, which has a slight negative camber at the root and changessection progressively (and radically) from root to tip. The use of negative camber at the root postpones drag rise due to super-sonic flow at the junction between the upper surface of the wing and the fuselage. Wing, fuselage and pods have all been de-signed as a lifting system to match each other. The camber changes to positive near the inner engines and remains so out tothe tip. Effective wash-out of the camber line ensures that the stall starts at the root and, to maintain maximum lift coefficient,the nose is relatively blunt. The wing is intended to increase the critical Mach number at a given lift coefficient, but it will haveto operate at a rather greater angle of attack for a given lift than would a wing with all-positive camber. Tail Both tailplane and fin have three main spars. The tail-plane has an extensive integrally stiffened three-plank structure between the front and centre spars; the only such structure in the AIRLINERS OF THE WORLD DOUGLAS DC-8 . . . ENGINEER'S STATION FORWARD PLUG-TYPE ENTRY DOOR (outward opening) /« 4 A« CONDITIONING BAY whole airframe. Each plank has three stiffened angles, and thetwo leading members are tapered off by the front spar. Most of the remaining skin in the tail unit is stabilized in a bonded innersection with stiffened flutes. The fin and rudder structure termin- ates no less than 8ft from the tip and the whole remaining surfaceis tuned for use as an aerial with a central feeder cable. Above the light alloy structure, glassfibre sections are inserted extendingover the entire chord of each surface and continuing up and down the rudder trailing edge. The remainder of the metalstructure is then bolted to the glassfibre spars and around the profile periphery. Pods The pods are interesting in that their trailing edges arecurved inboard to follow the natural streamlines of the airflow; this gives lower drag than pylons used as fences which constrainthe air to flow axially across the wings. The complete pylon and nacelle assembly is sub-contracted to Ryan. The engine pylonshave two spars, chordwise frames and stringers. The spars pick up on stiff ribs in the wing which (unlike the majority of the ribs,which are perpendicular to the rear spar) run fore and aft. The nacelles are conventional double-skinned assemblies in which theentire access doors (amounting to virtually half the nacelle and hinged along the junction with the pod) are of titanium sheet. Awide strip of the trailing edge of the pylon is also fabricated from titanium. Undercarriage The main gear consists of a conventionalshock strut carrying a tandem bogie on which the rear wheels are articulated to allow the aircraft to pivot about a point 4.5ft fromthe inside gear. The track is 20ft 9Jin. Each main leg is a forging, forked at the upper end and carried by a large triangu-lated forging bolted to the aft face of the rear spar and to a pair of sub-spars. The main legs are held fixed in the down positionby a set of side brace links which are locked on-centre by a pair of spring-loaded toggle links. The wheels are automaticallybraked during the first part of the retraction cycle and the gear is closed by three doors in the latched-up position. The largest ofthese, covering the wheels, is operated by a hydraulic jack con- trolled by the position of the gear; the door is closed when thewheels are down. Goodyear dimpled tyres at 131 Ib/sq in and disc brakes are fitted. All undercarriage units can be unlockedand allowed to fall under gravity. 1 Weather radar dielectric radome2 Intake to cabin air system 3 Cabin-air turbo-compressors (55,000 r.p.m.) 4 Turbine exhaust 5 Heat exchanger exhaust 6 Access door 7 Electrically-heated multi-layer glass screen (no wipers) 8 Upper windows each side 9 Forward pressure bulkhead 10 Supernumerary seat 11 Engineers' panel 12 Radio racks (air cooled) 13 Coats 14 Twin nosewheel doors 15 Nose gear geometry similar to DC-7 16 Steering cylinders (10 deg each way with rudder, 78 deg by handwheel) 17 Retraction jack 18 Galley service door 19 Underfloor hold (door starboard)20 Wall-fixed slots 21 Attendant's seat 22 Centre-joint butt-stop 23 Centre section tank ("overwater" model 1910 only) 24 Centre keel-member (5ft deep) 25 Mainwheel doors (normally closed after undercarriage extension) 26 Windows (18iinx15in) 27 Grille (cabin air in: out at floor level) 28 Passenger-address speaker 29 Hat racks 30 Emergency exits 31 Emergency doors 32 "Hot wall" panelling 33 Inward-opening freight door ZA Concealed lighting ROLLS-ROYCE CONWAY BY-PASS TURBOJETS 35 Integral three-spar fin 36 Sloping frames 37 Fibreglass (dielectric) structural isolation 38 Bonded inner skin 39 V.O.R. aerial 40 H.F. aerials (1 and 1) 41 Tailplane screw-jacks 42 Tailplane hydraulic and electric motors 43 Tait de-icing trunk44 Retractable bumper 45 Integrally-stiffened skin 46 Fully-powered rudder 47 Manual elevators 48 Fuel system runs 49 De-icing duct (cyclic heat) 50 De-icing trunk 51 Hot air anti-icing 52 Production break 53 Primary (combustion) airKow 54 By*pass airflow (diagram) 55 Inswept pylon tails 56 Intake to Sundstrand-drive oil- coolers
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