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Aviation History
1981
1981 - 1236.PDF
1246 FLIGHT International, 2 May 1981 tenanoe. BAe has opted for access panels1 that do not carry load because this arrangement is simpler, although slightly heavier. This philosophy is fairly typical throughout the 146 de sign, BAe generally opting far an easier structure to build and maintain at the expense of a little weight. Inspectability is another area in which the 146 has been given a lot of attention (see the accompanying feature beginning on page 1254). The metal strips between the spar booms and skin, which provide an alterna tive load path as failsafe structure, are a good example. BAe has deliberately made the strips thin and wide so that they extend well in front of and behind the spar booms, making it easy to see any cracks which might appear. The 146 fuselage, like the wing, is assembled from fewer parts. There- is only one main joint in the front fuselage, for example: between the nose and the centre section. By com parison, the Trident had two. Like the Trident and A300, the nose1 section is stringerless, the fuselage skin only being supported on frames. In the rest of the fuselage, inverted V-section stringers are bonded to the skin, saving many thousands of rivet holes. This arrangement is not new, however. It was used on the Trident. What is new are the fuselage frames, which now comprise an inner ring to take bending and an outer, notched ring that carries mainly shear. This arrangement allows elimination of about 5,000 stringer/frame cleats. Like the wing, the 146 fin box comprises a front and rear spar, two skins with bonded top hat stringers, and ribs. But the ribs differ in being fabricated and having channel-section trusses. Ten attachments support the taitplane, which is a two-spar design with single-piece upper and lower skins. The top and bottom half of each spar is made of a different alu minium alloy, and the ribs are also of sheet metal construction. BAe has only used composites in two areas of secondary structure—the wing/fuselage fillet and flap track fairings. It has used glassfibre rein forced plastic in both places. Two of the flap track fairings on each wing are in line with the engine pylon to Avco Lycoming's ALF- S02R-3 turbofan pro duces a maximum thrust of 6,7001b. Four power the 146, giving it an excellent hot and high per formance. The ALF- 502 is a two-shaft design with a geared fan. Its core is the same as that of the Chinook engine. The ALF502R-3 was certi ficated in January this year minimise the total drag. An overall impression of the 146's simplicity can be gauged by the num ber of structural drawings, which totals about 9,000. The BAe One- Eleven had about 19,000 structural drawings, while the Trident had roughly 16,000. BAe also claims that the use of integrally machined parts and Redux bonding saves around 120,000 fasteners. The desire for simpler assembly and maintenance has been pursued in the 146's systems, where one approach has been high parts commonality. There are two 3,0001b/in2 hydraulic systems to power the flaps, airbrakes, undercarriage, and brakes. Each hyd- draulic circuit is driven by a pump on an inboard engine, and one system has an electrically driven AG pump as a backup. There is also a DC electric pump to provide hydraulic power to the brakes. All hydraulic- pipe couplings are flareless, with swaged fittings for easy assembly and maintenance. Electrical power is provided by an AC generator on each outer engine. Backup power can be supplied by a generator on the Garrett AiResearch GTCP36-10O auxiliary power unit (APU), which may be used at alti tudes of upi to 20,000ft. BAe claims that the APU is only about a third of the weight of competitive units, as well as having only half their fuel burn—a significant factor in short- haul aircraft, which keep their APUs running during turnround. A limited amount of electrical power is avail able through a hydraulically driven generator as a further safeguard. Fuel for the 146 is stored in in tegral tanks—one in each wing and one in the centre1 section. Pressure refuelling is standard, but each wing also has an overwing filler. Each wing of the 146 has an anhedral angle of about 3°, but the wings become vir tually flat when it gets airborne, so fuel feed is not a problem (a high wing is inherently stable, making di hedral unnecessary). Fuel is fed to the engines via electric pumps in the outer wing, and there' are backup hydraulically driven pumps. An extra fuel capacity of 300gal is available as an option. This would be housed in two tanks in the rear wing/ fuselage fairing. All the fuel-wetted areas of the wing are assembled with Thiokol sealant between joints, which helps combat corrosion and avoid BAe has optimised the 146 for short sectors of less than 300 n.m. but it can, of course, be operated profitably on longer legs. Left BAe 146-100 take off performance, assuming fuel reserves for a ISO n.m. diversion plus 4Smin holding at 5,000ft. Right BAe 146-100 payload/range, assuming the same fuel reserves and ISA enroute temperatures 7.000. 6.000. 5,000_ 4,000. - High speed cruise Long range cruise 400 Stili air range (n.m) % 10,000_ — 82 passengers & baggage 80.7501b MTOW long /-„„ 200 400 600 800 1,000 1,200 1400 1,600 1.800 Still air range (n.m
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