A Sample Feature From Aviation News

Aerion – Dawn of a supersonic revival?

Aviation News has been talking to the Aerion Corporation and ExecuJet on the fantastic new supersonic business jet (SBJ) that could be flying by 2012 and in service two years later. But is it all a pipedream or could this be just the starting grid for a Concorde Mk 2?

Above: Aerion Corporation estimates a potential order book of 250-300 within the first ten years of production for its Supersonic Business Jet. If successful, it could be a potential link to a full scale Concorde replacement. (Photos, Aerion)

Since the demise of Concorde from the skies in August 2003 business people have been denied a fast-track option to getting ahead of the opposition and moving rapidly across the Atlantic. In reality, it had been a relatively brief period – less than 27 years – in which trans-atlantic travel had shrunk to little more than 3hrs. Then it was over. Now the Aerion Corporation has taken a major step towards restoring that option – but on a personalised basis on demand, no longer tied to scheduled flights. From 2014, it just might be possible to leave Paris at 8:00am, have breakfast in New York, lunch in Boston, dinner in Washington and be back in Paris for a breakfast the following day before dawn! But is the market big enough? Aerion thinks it is and an objective analysis of the market tends to support their view.

Above: Distorted by this perspective illustration, the 29.5ft long pressurised compartment occupies little more than one third of the total length of the Aerion SBJ but places the passengers well forward of the two JT8D turbofan engines.

Launched in 2004, the Aerion SBJ is based on a unique aerofoil known as a natural laminar-flow (NLF) wing, designed by world-leading aerodynamicist Dr Richard Tracy. Aviation News will be looking in detail at this concept in a future issue but expressed simply, the straight-wing NLF design has 50% supersonic drag reduction and that makes the aircraft a lot more slippery than it would be otherwise. This moves the aerodynamic efficiency into a region where a relatively conventional engine can be employed, saving a lot of money. Moreover, the wing itself has desirable effects by minimising the overpressure (sonic boom) experienced at ground level with swept or delta wings. Below Mach 1.15 cruise, at 45,000ft or above, the sonic boom is not heard on the ground at all. While commercial supersonic flight over the US is prohibited, the rest of the world operates under ICAO rules and large areas of land can be crossed at speeds in excess of Mach 1 legally. While the patented NLF wing is key to efficiency the rest of the airframe also benefits from design innovation.

Aerion have chosen the Pratt & Whitney JT8D-219, de-rated to 19,400lb thrust for the SBJ, meeting the latest ICAO emissions standards and benefiting greatly from US government investment in making this engine more fuel efficient for the E-8 JSTARS programme. Extensive analysis by Pratt & Whitney confirms that essentially the basic JT8D-219, already flying in one-third of the world’s airliners, will suffice but with a new combustor and higher grade alloys plus some new materials in ancillary equipment. At supersonic cruise for 60% of flight time, the engine is projected to have a TBO of 3,000hr and the economics work out comparable to a conventional subsonic business jet. Fuel efficiency is about at the level of a large executive jet.

Aerion has tested subscale sections of the new NLF wing on an F-15 and aerodynamic predictions made after NASA conducted wind tunnel tests hold up. Sections of the wing were tested on rocket sleds at Sandia National Laboratories, in which both small and large scale sections were accelerated to Mach 1.6. Much of the thin wing will be fabricated from composites for strength and weight saving, although the leading edge will have a coated metal surface for erosion resistance. Test results revealed a need to reduce the wing area from 1,400sq ft to 1,200sq ft and the original T-tail was replaced with a horizontal stabiliser at the base of the fin. There is carbon in places on the heavily area-ruled (pinched-waist) fuselage but it is mostly fabricated from aluminium alloys. The fuselage interior accommodates a pressurised cabin (8,000ft equivalent altitude at 51,000ft) capable of carrying 8-12 people but inspection of a large model reveals just how far forward that section is. Overall, the 29ft 6in cabin has the cross-section of a Challenger 300, 6ft 6in wide and 6ft 2in in height, with three separate seating areas and space for a galley and a toilet.

Above: The substantial interior is optimised for eight seats in luxury, or 12 in comfort, with ample space for a conference compartment, forward galley and aft toilet, specifics entirely at the behest of the owner.

With operating costs claimed comparable to current subsonic business jets, performance projections reveal critical advantages. Maximum range of 4,400nm is achieved at Mach 0.95 but compromised to about 3,550nm at Mach 1.07, optimised again in the supersonic regime at around 4,200nm at Mach 1.45. Range at Mach 1.6 drops to 3,500nm. Mapped flight routes simulated over real-world examples show convincing advantages that would work productively for the business or executive traveller. A Paris-New York flight maximising over-water flight would take just 4hr 14min, saving more than 3hr over a conventional bizjet. Restricted to Mach 0.85 across the US the SBJ would cut only 40min from a 5hr New York to Los Angeles flight today, but an over-water dash down to Miami from New York would take a mere 93min versus 2hr 27min in a subsonic jet. With an eye on at least one potential market, a 4hr 15min dash from Dubai to Singapore would cut the time in half.
Costs are everything for the business executive and set against these impressive gains is the buying price of $80m. Specific operating costs, however, show the SBJ cheaper than Challenger 605, Gulfstream G40, Global Express XRS and, expectedly, much cheaper than the BBJ and A319. No small aircraft, the SBJ has a length of 148ft 3in, a height of 23ft 3in and a wingspan of just over 64ft – it needs a big garage. At 90,000lb maximum take-off weight, of which half is fuel, the SBJ has a balanced field length of less than 6,000ft and with a wet runway landing roll of just under 3,500ft it is very manageable for its size. Aerion are keen to point out the ‘green’ credentials of the aircraft, selecting a performance profile that takes cruising speed to the stratosphere at 51,000ft and no measured boom from Mach 1.1-1.2. Marketing claims that it flies ‘below the ozone layer’ and is therefore more ‘green’ because of that are invalidated by the facts. But full marks for trying! Chlorofluorocarbons, responsible for breaking down ozone vital for screening out critical UV rays, were banned in the US several decades ago and in any event, drift up from lower altitudes.

Below: Extensive wind tunnel and supersonic sled tests and flight trials with subscale wing sections prove the theoretical value of the natural laminar flow wing. Brainchild of Richard Tracy, design lead on the Learstar 600/Canadair Challenger and design engineer on Global Hawk and the NASA X-30 NASP project, the patented wing is a key element in the Aerion design advantage

For the rest of this feature please see the March 2008 issue.