Towards an energy-optimised aircraft

The aerospace sector was already thinking hard about saving energy long before global warming became a concern. Thanks to lighter aircraft and more efficient engines, emissions per passenger-kilometre have fallen 80% since the early 1960s. Today’s most efficient aircraft consume barely more than 2.5 litres of fuel per passenger per 100 kilometres. As a result, civil aviation accounts for barely 2% of global CO2 emissions.

The aviation world is taking action to reduce its environmental footprint

The stated goal of the International Civil Aviation Organization (ICAO) is now to stabilise CO2 emissions at their 2020 level – amid growth in air traffic to boot – and to work to reduce them by 50% by 2050 relative to 2005 levels. For aerospace programmes in production, aircraft manufacturers continue to make improvements to models even after launch.

For example, the A320 Neo’s consumption in 2020 should be 20% lower than that of the initial model.

For future programmes, the ICAO has tasked France, via its Civil Aviation Research Council (Conseil pour la Recherche Aéronautique Civile – CORAC), with conducting research aimed at reducing the environmental footprint: more efficient engines, lighter aircraft, development of the use of electrical propulsion technologies, and development of aircraft biofuels.

The energy-optimised aircraft

In the quest to reduce aircraft energy consumption, the energy-optimised aircraft is logically one of the three major research priorities defined by CORAC in its technological roadmap unveiled in March of this year.

Safran is developing an engine designed to use 30% less kerosene than a traditional turbojet. The prototype, known as Open Rotor and under development since 2008 as part of the European Clean Sky programme, is currently undergoing testing at Istres. The aim is to bring it to market by 2030, in time for Airbus and Boeing to refresh their narrow-body aircraft ranges. The icing on the cake: it is also much quieter than its predecessors.

In terms of architecture, Airbus is continuing with its testing, notably by fitting its A340 Blade with laminar wings aimed at reducing friction by 50%, translating into a 5% reduction in CO2 emissions. To achieve this performance, the wings are each equipped with extensions forming a 20-degree angle to the rest of the wing.

Meanwhile, in electric aircraft, pioneering spirit is alive and well and concept planes abound. Solar Impulse completed a round-the-world flight with its four solar-powered electric motors. E-Fan X is a hybrid aircraft developed by Airbus in partnership with Siemens and Rolls-Royce.

Efforts on the ground too

As well as working to limit kerosene consumption and optimise flight paths, it is worth emphasising two lesser-known but equally important factors.

For airports, taxiing operations and the use of auxiliary engines during stopovers account for around three quarters of emissions of greenhouse gases, nitrogen oxide and particles, and around 95% of emissions of volatile organic compounds. Beyond measures to limit taxiing time, two technological solutions are currently in testing.

The first could prove its effectiveness at major airports hosting long-haul aircraft. The innovative TaxiBot, a diesel-electric tractor developed by airport equipment supplier TLD, makes taxiing possible with the main engines switched off but the APU* running, meaning the main engines need only be started two to three minutes prior to take-off.

The second solution, being tested on the A320, could be of interest for short- and medium-haul aircraft. The Electric Green Taxiing System has been developed as part of a joint venture between Safran and Honeywell. It consists of an electric motor fitted to each main landing gear, enabling aircraft to taxi without using their main engines. These electric motors are powered by the APU.

Although it now serves mass transport, aviation has always helped push the boundaries by investing in research and development, opening up the way for innovation. There are thus many environmental initiatives in progress in this structured sector, where effectiveness relies on coordination between players.

— Pascale Rombaut-Manouguian, Senior Industry Analyst, Credit Agricole S.A.