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Aviation History
1973
1973 - 2582.PDF
FLIGHT International. 18 October 1973 Hawker Siddeley's prediction of the fesder- liner market CD Q. C 628-62^ 120 100 Feederline growth Excludes Warsaw Pact Countries and China 1966 1968 1970 1972 1974 1976 1978 1980 1982 ing 502 turbofans offer the most economical package, in terms of both first cost and maintenance expense. Guarantees renegotiated with Avco should ensure that four 502s have the lowest maintenance cost of any avail able powerplant package suitable far the 146. Why not a trijet? First, says Hawker Siddeley, there would be at least two engine installation standards. There would be c.g./loading problems because of the length of fuselage ahead of the wing. It would also be difficult to have doors at either end of the cabin and a rear-fuselage- mounted speedbrake would not be possible. Engine-out ferrying would not be so practicable and developments with rear-ramp loading would be impossible. Many of the same arguments apply to a rear-engined twin layout. An under-wing twin would satisfy many of the requirements, but would suffer in the engine-out case. Given four engines, the high wing and under-wing lay out of the powerplants became logical. Mr Bethwaite believes that the benefits and disadvantages of engine noise shielding by the airframe are hard to define. Airfield performance The wing itself is a highly efficient aft-loaded design which enables a total aircraft lift coefficient of 3-38 to be achieved. With a cruise speed set at a conservative Mach 0-7, the 146 wing has been designed with the emphasis more on low-speed performance than would have been possible with higher cruising speeds. The wing has tabbed Fowler flaps but leading-edge devices are not fitted. A slat would add complication and would probably mean having to resort to an all-moving trimming tail because of the greater induced pitching moments. The 146 is designed for simplicity and has basically a manual flying-control system. Hawker Siddeley believes that, be cause of the highly efficient wing, there is no real economic penalty in terms of wing area and weight resulting from the good airfield performance of the 146. The first variant of the 146, the 71-seat Series 100, will have to cope with short, unprepared strips. It has a high centre of gravity because of its high-wing layout, so it requires a wide-track undercarriage. The HS.146 main-wheel retraction system is ingenious, providing a main-wheel track of 15ft 6in, which is wider than that of the Lockheed Hercules, yet the fuselage blister is hardly discernible. The Series 100 has a sea-level take-off performance as good as that of the HS.748 and at high altitude and high temperature it is better. The company says the airfield capabilities of the 146 satisfy 95 per cent of the market and that such performance is necessary for a turboprop replacement. The Series 200 is a fuselage-stretched 102-seat variant (six-abreast) aimed more at regional carriers with less demanding airfield requirements. The extra payload is traded for airfield performance. The airframe structure is unchanged apart from the additional fuselage sections. The Vj|0 and VNA design speeds are reduced to enable the majority of Series 100 components to be used and the aircraft is restricted to paved-runway operations. The main competition for the Series 200 will come from second-hand DC-9s, One-Elevens and 737s. Hawker Siddeley expects that the stretched variant could take 30 per cent of 146 sales initially and perhaps a greater proportion as time goes on. How can the 146 succeed when the F.28 and One-Eleven 475 have not sold as well as they might? Apart from design considerations, a decisive factor could be linked to the amortisation period of existing turboprops. In about 1976- 77 the number of twin turboprops reaching ten years old takes a substantial upward swing. From that time onwards Hawker Siddeley considers them ready for replacement. This is not to say that the HS.748 will necessarily go out of production as the 146 line starts up. There should be a continuing market for it. The 146 will be assembled at Hatfield but considerable sub-assembly work will be done at other Hawker Siddeley factories and design work is going on both at Hatfield and Woodford at the moment. About 250 Hawker Siddeley design staff are working on the 146 at present. Bought-out items are being selected, although no suppliers have signed yet. Contracts will be long-term with a fixed price plus an agreed escalation clause. The price of the engines has been fixed on a similar basis. Flexibility The HS.146-100 will carry 71 passengers up to 1,200 st miles, 1,930km from a 3,650ft, 1,100m runway. A high thrust-to-weight ratio is maintained even after an engine failure and the aircraft suffers no WAT limitations for airfield elevations up to 8,000ft and temperatures of ISA+.20°C. On the ground the 146 needs no ground-power unit if either the optional APU or starter battery pack is fitted. , The engines are started electrically—pneumatic ground trolleys are never needed. The engine accessories are at eye level and the core of the engine can be reached by slid ing back a cowl. There is a single pressure refuelling point. Airstairs are optional at the forward and rear left doors. The galley provision is adequate for several short stages
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