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Aviation History
1957
1957 - 1617.PDF
FLIGHT, 1 November 1957 705 AIRLINERS OF THE WORLD CARAVELLE Societe Nationale de Constructions Aeronautiques du Sud-Est, Paris A FTER a remarkably smooth and short design and develop-fjL ment period, the Caravelle is now fairly launched on its J- -*- sales career. Contracts are in hand from Air France andS.A.S. with prospects of further orders from several other airlines. It is maturing at a moment when increasing interest is being shownin jet transports capable of operating short stages economically. The Caravelle was designed for just that purpose. Its average stagelength in service will be about 500 miles. The decision to build the Caravelle was taken in January 1952; agovernment contract was awarded to Sud-Est Aviation (which combined with Ouest-Aviation to become Sud-Aviation in 1957) in September1952; metal was cut in April; the first machine was rolled out in April 1955; and the first flight was made on May 17, 1955.In addition to the collaboration of Rolls-Royce, de Havilland's experi- ence contributed considerably to the general design (ironically, it maynow seem, since the Caravelle is a strong rival for the Comet in the short-medium-range jet market). Many British companies have suppliedcomponents, including Lockheed, Dunlop, Hobson, Venner, Tedding- ton Controls, Self-Priming Pumps, Flight Refuelling, and Graviner. AIRFRAME The circular-section fuselage is of conventionalmulti-stringer monocoque construction with a cylindrical section, 126in diameter and 53ft long, extending for nearly half the total fuselagelength. Extensive use is made of spot-welding techniques and all joints are sealed with Araldite resin bond. The nose section is takenfrom the de Havilland Comet; there is a double-curvature portion between this and the cylinder which forms the bulk of the 6,120 cu ftpressurized fuselage. The fuselage contains 28 windows, 11 of which are inward-opening escape hatches; by the main entry door—uncon-ventionally situated under the tail—and by a 78in by 69in freight door with an inset sliding crew-door forward on the port side. Wing The design of the N.A.C.A. 651212 section wing was con-ditioned by the desire to provide a long-life structure with fail-safe characteristics. A three-spar torsion box forming an integral fueltank is the basis of the structure. The top and bottom skins are taper- rolled and stiffened with quarter crescent-shaped ribs and stringersinterspersed with pierced baffle ribs. Attached to the torsion box is the drooped leading-edge (the variable camber flap of the prototype hasbeen discontinued on subsequent aircraft), two aileron sections and eight flap sections. Air brakes extend above and below the wing. Undercarriage Of Hispano-Suiza manufacture, the main under-carriage comprises four-wheel bogies which retract partly into the wing and partly into the fuselage, and a twin-wheel nose undercarriage unitsteered hydraulically through a range of 100 deg. Wheels, brakes and anti-skid units are supplied by Hispano, while the tyres, inflated to96 lb/sq in, are supplied by Dunlop. POWERPLANT The installation of the two Rolls-Royce AvonRA.29 (basically similar to the Comet 4 and 4B engine) in this position offers advantages which are worth restating: (1) the wing and flaps areaerodynamically clean from root to tip. (2) Fire risk is reduced by the separation of fuel and engines. (3) Cabin noise levels are low. (4) The change of air intake incidence with wing incidence is half that for wing-mounted engines. (5) Asymmetric thrust is negligible. (6) Thrust line is close to the centre of gravity, variations of thrust having little effecton longitudinal stability. SYSTEMS Flying Controls The Caravelle shares with theComet irreversible hydraulic servos for all surfaces. Proportional feel is also provided hydraulically, although the Caravelle has, in addition, basefeel provided by pre-tensioned torsion bars. The Lockheed Servodyne valves are operated by cables from the duplicated wheels and pedals inthe cockpit. A single Hobson "q-pot" device supplies controlled hydraulic pressure to all jacks according to dynamic pressure sensed atthe starboard pitot head. A Lear autopilot is standard equipment. Cabin Air Tapped compressor-bleed air, passed through a heatexchanger, turbine expansion unit and water extractor, is used to pressurize the cabin to a differential pressure of 8.25 lb/sq in (8j000ftat 40,000ft). Cooling air is ducted from the two ram-air scoops at the base of the fin to the heat exchangers close to the engine. The Cara-velle's cabin air system was developed in conjunction with the U.S. firm of AirResearch, who make much of the equipment. Electrics There are three primary electrical circuits: a 28.5 V DCsystem; a 26 V 400 c/s AC system and 115 V 400 c/s AC system, with the structure used generally as the earth. Electrical power is sup-plied from a carbon-pile regulated 30 V DC generator on each engine with a continuously rated output of 375 amps, or an output limited to30 min of 400 amps. All the 115 V AC current is supplied from a pair
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