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Aviation History
1979
1979 - 4706.PDF
2128 FLIGHT International, 29 December 1979 An aircraft without a trace of paint proves it—the AVS&'s best friend is carbonfibre. Composites save 3301b, and offset the weight penalty of 30ft2 more area than the Harrier 12,000hr—a scatter factor of two. The new front fuselage gives im proved visibility, accommodation and avionics space. Design eye point is raised lO^in and windscreen and canopy redesigned to give better for ward (17° down), side (60° down) and over-the-shoulder visibility. Composite construction reduces the number of parts required for assembly and saves 561b—almost 25 per cent. Left and right half shells are moulded, 0-149in-thick sandwich skins, with a low-density, epoxy-based core between carbon-fibre sheets. Stiffners are integral mouldings. Floor panels and bulkheads bolt in place and the half shells are bolted together. A detachable nosecone allows access to the avionics. The whole assembly is mechanically attached to the centre fuselage. A single front fuselage ex ample has been built. To balance the new nose, the rear fuselage is extended 18in. The struc ture has been restressed to withstand loads imposed by the wider AV-8B vectoring-in-forward-flight ,(Viff) en velope. Rear equipment-bay volume is increased. The taller Sea Harrier fin is fitted to compensate for increased front-fuselage side area. Redesign of the rear fuselage is the responsibility of British Aerospace, Kingston, now Cunpod strokes and a retractable dam increase the hovering ground cushion, generating more vertical lift. The rectangular, zero-scarf front nozzle can be seen as well as the deep inboard pylon a candidate sub-contractor to build sections for production AV-8Bs. While the wing uses around 3,000 fasteners, the tailplane, of later con struction, is much simpler. The slab surface is essentially four parts: metal leading edge, composite upper skin, composite lower skin with bonded-on spars, and detachable trail ing edge. Harrier tailplanes are prone to ground handling damage and the honeycomb trailing-edge construction prone to delamination. The detachable composite trailing edge will solve both problems. Carbon-fibre is considered ideal for the tailplane's high-vibration environment. The new intake is designed to give increased static thrust and reduced cruise drag. Double-row auxiliary in takes increase additional V/Stol intake area to 8 -4ft2, compared with 3-6ft2 for the Harrier's single row of blow- in doors. A 1 per cent better pressure recovery has been demonstrated— equivalent to 6001b more VTO (vertical take-off) thrust. The fixed intake has been resized to match airflow require ments in high-altitude cruise, reduc ing spillage drag. A 2:1 elliptical lip shape replaces the Harrier's circular arc and throat area is up from 9-2ft2 to 9-7ft2. Intake redesign has in creased the forward fuselage fuel tank capacity. Vertical performance is a complex interaction between thrust and ground cushion effects which lift the aircraft and weight, reingestion and suck-down which hold the aircraft down. To im prove the ground cushion and reduce reingestion, lift improvement devices have been fitted under the fuselage. These consist of strakes on the gun- pods and a retractable dam between the pods. High-energy exhaust gases reflected by the ground are trapped by these devices. This generates lift and reduces intake ingestion of the hot gases, increasing thrust. A 20° drop in intake temperature has been demonstrated. Lift improvement de vices generate 1,2001b more VTO lift. The devices reduce pilot workload in vertical landings by improving ride quality and counteracting jet-induced suck down. The cobblestone effect ex perienced by hovering Harriers is re moved, while the procedure of in creasing thrust as the aircraft ap proaches the ground is reversed. Pilots have found that the YAV-8B will sit 20ft from the ground unless the engine is throttled back. To AV-8B WEIGHTS AND MEASURES AV-8B AV-8A Span (ft) Length (ft) Height (ft) Wing Area (ft?) Operation empty weight (lb) Internal fuel capacity (lb) External stores (lb) Max VTO weight* (lb) Max VL weight* (lb) Max 1,000ft STO weight* (lb) Max design gross weight (lb) 30-33 46 33 11-65 230 12,750 7,500 9,200 19,550 17,850 28,750 29,750 25-27 45-55 11-54 201 12,190 5,000 5,000 17,050 16,700 22,300 25,000 * Tropical (90°F) sea-level day.
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