GUY NORRIS / SEATTLE
Dassault and Gulfstream say issues such as sonic boom mitigation are slowing supersonic business jet projects
Dassault and Gulfstream say market pressure is building to develop their respective supersonic business jet (SSBJ) study projects, but both stress the paramount need to overcome key environmental and technical issues before any programme can possibly go ahead.
Speaking at the 2001 Aerospace Congress and Exhibition in Seattle recently , Gulfstream vice president Preston Henne said "entry into the market is constrained by technical problems." Although various market studies by both companies indicate a requirement for between 300 and 400 aircraft over the next 20 years, they warn environmental considerations may make the project too difficult. Presenting a list of "barriers to QSJ [Quiet Supersonic Jet]", Henne says key issues include sonic boom mitigation, engine emissions, community noise, closing the performance gap and establishing the certification basis.
Dassault is studying a trijet SSBJ design aimed at flying 7,400km (4,000nm) ranges at speeds up to Mach 1.8. The current canard-equipped configuration is based on a Falcon 50-size cabin with a span of 17m (56ft), a wing area of 130m2 (1,400ft2) and a length of 32.4m. Dassault's Michel Rigault says the nine-passenger configured aircraft is being outlined with a maximum take-off weight of around 40,000kg (87,500lb) and an operating empty weight of 37,500lb.
Gulfstream's QSJ is based on a 37m3 (1,300ft3) GII-size cabin, seating eight to 14 passengers, with a range of between 7,400km and 9,250km and a target Mach speed of between 1.6 and 2.0. In 14-seat configuration, the 198mm (78.1in) high cabin will have a 0.5m wide aisle, compared to 0.43m in Concorde.
Target price for the QSJ is between $70m to $100m. "We have a business case which suggests that price would be profitable," says Henne who adds that the experience of the GV shows this is sustainable. He adds: "If people had said in the early 1990s that people would be standing in line for the GV for $40 million they'd have said you were crazy."
Noise targets are roughly equal, Dassault stressing "at least an 18dB margin" and Gulfstream a newly defined target of Stage 4 with an additional 10dB buffer. Both are relying heavily on advanced aerodynamics and shape optimisation to help reduce the boom intensity to around 1.5kg/m2 (0.3lb/f2) (versus 9.8 for Concorde). Dassault's Rigault says: "We cannot afford to develop exotic materials for such a small aircraft, so progress can only really come from aerodynamics."
The two companies are exploring diverse engine support cost requirements as part of their overall development strategy. Dassault suggests that a 500h time-between-overhaul (TBO) target may be acceptable as part of a trade-off between logistics and maintenance costs, while Gulfstream believes autonomous operational requirements will drive a mission reliability level of 0.99% and an engine life TBO of 2,000h.
Source: Flight International
