Professional Engineering

The workhorse of the skies is getting a makeover. The Airbus A320, the European aircraft company’s best-seller, is to be produced in a new version, the A320Neo, by October 2015. The new airliner will offer 15% fuel savings, a 15% cut in CO₂ and 50% less NOx emissions, and a 15dB noise reduction compared with today’s A320.

Neo stands for New Engine Option, and it’s the engine that will deliver most of the advancements. “It’s not really the airframe side that creates the big breakthroughs in fuel savings,” says John Leahy, Airbus’s chief operating officer. “It’s coming from the engine technology.” Two new engine options are being offered by Airbus to its customers, and they represent contrasts in engineering and in philosophy. 

In this contest between two engine makers, Pratt & Whitney is portrayed as the radical innovator with its PurePower PW1100 engine. CFM International, the joint venture between GE of the US and Snecma of France, is emphasising its solid experience with its Leap-X engine. 

The line-up may not look much different from what Airbus has offered customers for the past 20 years or so, although there is one significant missing name. CFM has been supplying its CFM-56 for the current A320; the new P&W engine brings in the German and Japanese firms that were involved in the IAE V2500 consortium, but not Rolls-Royce, which has opted out. “The nameplate this time is Pratt,” says P&W’s senior vice-president of engineering Paul Adams. 

The real differences, though, are in technology. Pratt’s engine is a geared turbofan or GTF and is, says Adams, “a new kind of product offering in the commercial aeroengine space”. In simple terms, the GTF puts a gear system between the fan and the low-pressure compressor, which means the fan operates at a lower speed and enables the optimum bypass ratio to be increased to 12:1 or even a bit higher. 

“The gear system means we can optimise the fan and the low-pressure compressor which enables us to take the bypass ratio beyond where historically it would have been optimised at,” says Adams. “This has a direct effect on propulsion efficiency so that ramifies itself into a lower fuel burn.”

P&W says it is saving 16% in fuel compared to what it achieves with the V2500, and that feeds through directly to a 16% CO₂ emissions cut too. It’s also using its Talon combustor technology with fast quenching to cut NOx by around 50%. Adams is wary about claiming that these figures are exactly what any airline operator will get, but they are similar to what Airbus quoted in its A320Neo publicity launch.