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Aviation History
1973
1973 - 2584.PDF
FLIGHT International, 18 October 1973 AIR TRANSPORT ALF 502H TURBOFAN 630-631 • Seven-stage axial/single-stage centrifugal compressor. • "Folded" reverse-flow annular combustor. 9 Two-stage air-cooled turbine directly coupled to the compressor shaft. • Two-stage uncooled fan-drive turbine: the drive extends forward through the hollow compressor shaft to the fan reduction gear. • Single-stage fan with additional core-engine supercharger stage. • Single-stage planetary helical reduction gear transmits power from turbine to fan. • Accessory drive (from the power producer) externally mounted on the lower fan shroud to ensure easy access to engine-driven accessories. 0 Modular construction. • Designed for 10,000hrTBO. Take-off thrust (sea level, static 15C/59F day) 6,5001b, 2,950kg Bypass ratio 6-1:1 Length 56-8in,1-44m Height 52-5in, 1-33m Weight 1,2451b, 565kg and cargo pallets of up to 108inX88in may be carried if the optional cargo door and strengthened floor are fitted. Below-floor baggage volume is a generous 500 cu ft and an inflated main wheel or engine module can be carried in the forward hold, with its 53in-wide door. Noise will have an increasing effect on the operational flexibility of aircraft and to this end the 146-100 will have an overall 90PNdB noise footprint smaller than that of the turboprops which it will replace. The approach foot print will be about the same, but the superior climb gradient will ensure that the take-off over-flying footprint will be smaller. Economics Low noise could have a beneficial impact on 146 economics, with noise legislation continuing to clamp down on the noisier aircraft. In general terms the direct operating cost per flight on short stages should be 15 per cent to 20 per cent below that of current short-haul jets in widespread service, while per-seat DOCs should be some 10 per cent to 15 per cent below those of twin turboprops. Particular attention has been paid to design ing an aircraft optimised for profit on 100-mile to 200-mile stages. Reduction of flight-cycle-dependent costs has therefore been a prime objective. On a 150 n.m., 280km stage with a 2,750hr utilisation the DOC distribution is approximately: engineering, 22 per cent; fuel and oil, 26 per cent; crew, 18 per cent; annual costs, 34 per cent. Engineering costs are being held down by simplifica tion, reduction in the number of parts whenever possible and use of off-the-shelf components. Annual costs—amortisation, insurance, interest charges and spares—are held down by a relatively low first cost. " US. 14S BASIC DATA Span Length Height Wing Gross area Aspect ratio Quarter-chord sweep Anhedral Fuselage External diameter Ground clearance Cabin length Entry doors Height Width Sill height Cargo compartment volume Front Rear Total Fuel capacity Design speeds VMO MMO Typical cruise speed •86ft 6in 85ft 10in 27ft 11 in 832sqft 26; 36m 26-16m 8-51m 77-3m2 9-0:1 15° 8° 11ft 8in 2ft 2in 50ft 7in 6ft 3in 2ft 8in 6ft 4in 265 cu ft 252 cu ft 517 cu ft 2,220 Imp gal 2,664 US gal 315kt CAS MachO-7 425kt TAS at 22,000ft 3-56m 0-66m 15-42m 1-91m 0-81m 1-93m 7-50m3 7-14m3 14-64m3 10,090lit 584km/hr CAS 788km/hr TAS at 6,700m Major factors contributing to reduced costs in these areas include simplicity in all systems design and structural jointing areas—no stringer/frame cleats on fuselage and simplified wing/fuselage joint, with only a single joint in the top wing skin. Maximum standardisation of parts is adopted wherever consistent with low cost—all six lift-dumpers are identical, the engine pylons are common, both wing spoilers are identical, all four engine pods are interchangeable, flap tracks and many undercarriage elements are non-handed and seat rails are positioned so that all floor panels in the parallel section are identical. The airframe structure is designed for long service life under intensive short-haul utilisation. Conventional and widely available materials, at moderate stress levels, are used. The entire airframe structure is designed on the fail safe philosophy, with duplication of load paths and bonded crack-stoppers where appropriate; fail-safe fuselage frames can contain a skin crack well in excess of one frame pitch in length. Design philosophy Extensive use of metal-to-metal bonding reduces the number of rivet holes, to give improved fatigue resistance, and well proven corrosion protection techniques are used. Fatigue testing will demonstrate 80,000 crack-free flights, giving a guarantee of least 40,000 crack-free flights in service and an economic repair life of 60,000 flights. The landing gear is to be tested to 200,000 landings. Structure The 8ft 8in-diameter pressurised fuselage is of conventional skin/stringer construction but with the cockpit section and tail cone stringerless. Top-hat-section stringers are Redux-bonded to the copper-based alloy skins above the keel area. Open Z-section stringers are "wet" assembled with Thiokol and riveted to the skin •in the keel area. Skins are chemically etched to reduce stress levels. Frames are built-up pressings except for the main wing/undercarriage location frames, which are machined from the solid. The fin and tailplane use etched skins and bonded top-hat stringers. The wing-root fairing is of Nomex honeycomb sandwich, as are the majority of control surfaces. The wing uses,machined, tapered panels top and bot tom. The top skin is in zinc-based alloy for compressive strength, the lower in copper-based material for the best fatigue resistance. There is no magnesium in the prime structure. Engine pylon support ribs are machined integ rally with the wing. ^Outboard of the engines the leading edge has a double skin, for de-icing hot air. The undercarriage is of the twin-wheel levered suspen sion type with a trailing axle beam. It is made in light alloy to avoid complicated machining operations on steel and is therefore slightly bulkier than would otherwise be the case. Its wide track is determined by the *2g turn
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