New plane engine designs put the bite on efficiency

Engine makers are developing new techniques for tomorrow's aircraft.

The next wave of passenger aircraft design is 15 years away and the engines used could be significantly different from today's models. This is one of the conclusions made by Airbus, the world's biggest civilian aircraft maker, which is battling with its US-based rival Boeing on when and how to replace its popular old single-aisle aircraft, such as the A320 that was introduced in 1988. Airliner designs, which place the engines on the wings of the plane, have remained unchanged for decades. But now engine makers are developing highly efficient engines such as the unducted fan.

These are open-rotor engines featuring several rows of propellers that jut out at different angles like rows of shark's teeth and move in a contra-rotating direction, giving the plane greater lift. The engines could help satisfy airline demands that any new plane must be 30 per cent more efficient to justify the costs of replacing their existing fleets. And in what would grab passengers' attention at the airport, they could be placed on the tailfins of the aircraft, said John Leahy, the chief operating officer of Airbus.

"What is technology of the future on engines? If you talk to the engine manufacturers and tell them to create an engine off a clean sheet of paper, they will probably go with the unducted fan," Mr Leahy said. "That is probably available in the middle of the next decade, maybe." And although carbon-fibre is an increasingly important light-weight material used in wide-bodied planes, which helps with fuel efficiency, Airbus has still not mastered using the material on the less expensive single-aisle aircraft.

"If we were to build a brand new single-aisle aeroplane today, we would probably build it out of metal, not out of composite because composites are very expensive," Mr Leahy said. Any investment in a new design would be a big gamble. Starting in the late 1990s, Boeing spent years and billions of dollars, developing its so-called "sonic cruiser", a plane that would fly faster than any other passenger aircraft.

Its design included a canard, or mini wings, at the front, which performed the same function as a tailplane. It also had two engines mounted at the back on a pair of huge wings-cum-tailplanes instead of traditional wings. But the project was cancelled in 2002 after it prompted little interest among airlines, which favoured lower operating costs over any marginal improvement in speed. Now, with 2025 the arrival date for any new aircraft, Airbus and Boeing are wrestling with interim solutions. Both are considering whether to spend the more than US$1 billion (Dh3.67bn) needed to develop new engines for the 737 or 320, in partnership with engine makers such as CFM International and Pratt and Whitney.

"There are cases not to do it, cases to do it, and that is what we are debating internally back and forth," Mr Leahy said. "I really don't think [Boeing] will re-engine if we don't do it." [e-mail]