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Aviation History
1982
1982 - 2681.PDF
m mmmm. ... "*.nst?2: Supersonic Harrier: one step closer ROLLS-ROYCE'S work on a plenum chamber burning (PCB) supersonic Pegasus reaches its third phase when tethered tests re-start next April at Shoeburyness. In a £1-5 million Ministry of Defence-funded programme, the Pegasus 2A will be installed in a time-expired Harrier airframe and tethered tests carried out to investigate problems such as hot gas re- ingestion (HGR), airframe heating, and the effect of PCB on airframe composites, and ground erosion. The tests continue work that began some 20 years ago, when a supersonic P.1154 Harrier powered by the BS100 plenum-chamber-burning Pegasus was planned. Although kept since then at a low funding level, the work has eliminated A supersonic Harrier, or its derivative, is still on the cards for late Nineties fighter requirements on both sides of the Atlantic. Julian Moxon reports on new work at Rolls-Royce. many of the worries about problems that might occur with PCB, such as water ingestion and intake distortion. In answer to a Ministry of Defence request, Rolls-Royce has also produced a submission that, "compatible with the money available", extends PCB work to- date to the Pegasus 11 engine flying in today's Harrier. If approved, (and it seems likely that it will be), this would see full- scale rig testing of an augmented Pegasus run for the first time with a rotating, variable area forward nozzle (PCB work so The heart of the PCB system is the extremely complex colander fitted in each front nozzle. Cool fan air is mixed with fuel and ignited in the shortest pos sible duct length to increase Pegasus thrust by around 100 per cent FLIGHT International, 4 December 1982 far has been fixed nozzle). The geometry of such a nozzle is tricky, but R-R has several ideas to solve the problem. Most likely is an RB.199-type translating shroud arrangement on extended nozzles, operated by a flexible cable or by gears. Mini-jacks are also being considered for what could, in any case, be a simpler, two- dimensional variable nozzle. Other Pegasus 11 work, if funded, would cover: • Engine tests to prove the latest burner technology • Detail models to optimise the engine nozzle airframe configuration • Nozzle actuation and control system development • More work on hot gas re-ingestion 0 Further tethered tests, but using hydraulic jacks to raise and lower the aircraft for dynamic trials of the PCB system. Currently, the airframe is winched to various fixed heights, although it can be pitched, yawed, and rolled. More attitude tests are also included in Rolls-Royce's new submission. Development of the PCB system has been gradual, its future always uncertain. The original concept—burning the fan air in the front nozzles, leaving the rear nozzles to deal with unreheated core air- remains unchanged. Design techniques have improved, however. 1633
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