Variable geometry lowers supersonic cruise altitude

London
Source: Flightglobal.com
This story is sourced from Flightglobal.com

A supersonic business jet (SSBJ) with a variable geometry wing could land on short runways and fly 6,000ft (1,830m) lower than a fixed-wing SSBJ, says a European study.

As well as the lower altitude and short runways the variable geometry design is said to have the advantage of being able to use smaller engines and a smaller wing area, to achieve the same performance as a comparable fixed-wing design.

These performance advantages, say researchers, overcame the disadvantage of the wing's hinge mechanism, which has been estimated at 15% of the wing mass.

The study, a work package within the European Union's Sixth Framework Programme's five-year €26 million ($34.7 million) Environmentally Friendly High Speed Aircraft (HiSAC) project, involved two virtual models, one variable, one fixed.

"The optimum cruise altitude for the swing wing is 43,000ft [13,100m], rising to 49,000ft at the end of the cruise phase. This is 6,000ft lower than for the conventional fixed-wing design," says HiSAC industrial partner Dutch company ADSE consulting and engineering's senior aircraft design consultant Evert Jesse.

The market justification for the research is demand for business aircraft able to cross distances of 6,500km (3,500nm) in up to half the time of current jets.

Jesse expects that by the end of the year the variable geometry design will be sufficiently detailed that it can be compared with the other SSBJ configurations other HiSAC companies are investigating.

Starting in May 2005 and ending in 2009 the Dassault-led HiSAC project's goals are to achieve specifications for an environmentally friendly and economically viable SSBJ and enabling technologies' road maps for their further maturation and validation including a future proof of concept aircraft. But no demonstrator aircraft will be fabricated for the study.

To achieve the environmental standards to enable commercial SSBJ use HiSAC will identify the aircraft characteristics that will ensure a reduction in external noise by an 8db cumulative margin, less than 5-10g per kilogramme fuel burnt NOx emissions, landing and take-off emissions comparable to subsonic aircraft, overland sonic boom reduction, a transatlantic range, up to 16 passengers and flight-time reductions of up to 50% compared with existing aircraft.

Technologies to be considered are variable cycle and nozzle noise reduction for engines, forced laminar flow, high-lift devices and engine mixer-ejector nozzles. Mixer-ejector windtunnel tests are expected later this year.

HiSAC has 37 partner organisations from 13 countries include Ireland's Trinity College Dublin, Rolls-Royce, Sweden's Volvo Aero, Alenia Aeronautica, EADS Deutschland, Poland's Institute of Aviation Wasawa, Cranfield University, Swedish Defence Research Agency and France's Safran.


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