The most striking contrast seen at the recent ILA Berlin Air Show was that of a state of the art Airbus A350 XWB, a new twin jet family due to enter service later this year, and a tiny E-Fan two seat all electric general aviation training aircraft.
The E-Fan is seen as the first link in a chain of new and progressively larger and more capable propulsion systems that will augment if not ultimately replace the use of liquid fuels in aircraft.
But it will not just be a tough road, but one requiring three miracles of technology according to Alan Epstein, P&W’s vice president of technology and environment, in an interview in Flightglobal.
It’s a report the repays reading alongside this earlier Flightglobal article in which Airbus’s chief technology officer Jean Botti, talks about radical moves aimed at testing technologies that could power an electrical regional airliner with an endurance of up to three hours flight time in coming decades.
This is however, not a case of an engine maker saying ‘no way’ and an airliner designer and maker saying ‘this way.’
It’s a matter of separate interviews focused on different parts of the challenge. The technical problems Epstein talks about are massively and persuasively real. But the Airbus road map to an electric future is in some respects similar to that enunciated at times by Boeing, that is, there are ways of replacing liquid fuel burning engines at various stages of a flight by electrical energy supplied by non-fossil carbon releasing means, such as solar or wind capture and using them in hybrid power trains through quick change battery packs which scientists can envisage and enumerate but technologists have not yet turned into reality.
This includes increasingly serious proposals to use electric ground tugs to replacing engines when it comes to the often long taxi runs between runways and terminal gates. On some shorter inter city routes like Melbourne-Sydney or San Francisco-Los Angeles, that could save close to 20 per cent of the fuel burn, because jet engines are incredibly inefficient if used to lurch around for up to 20 minutes of sector time accelerating and decelerating several hundreds tonnes of airliner from being at rest to 15 kmh and back to rest again, over and over.
A long haul departure from major airports like CDG Paris can involve up to 30 minutes taxi and wait time, constantly burning fuel in engines that are at peak efficiency at high speeds and high altitudes, not walking speed at close to sea level. If the flight concerned is going to be airborne for 12 hours or so, that wasted tonne of fuel on the ground has a substantial negative effect on its range/payload performance when the airliner is required to arrive at top of descent to say Singapore carrying statutory reserves for holding, diverting and making a missed approach. Fuel that had to be carried by burning even more fuel all the way from Paris.
If aviation is going to have a sustainable future in a world where demand will reflect the rise to affluence of new economic super powers and fossil carbon releasing fuels are environmentally out of the question then the various miracles of superconductivity, shielding, and efficiency that P&W and Airbus talked about must be made to happen.