Last week one of the largest international conferences of aviation researchers gathered in London. More than 1,000 engineers from all over Europe, and some from the US, attended Aerodays 2015 to learn about the latest aviation research.
The event, which is only held every four to five years, is a showcase for European-funded research. Aerospace R&D is highly dependant on government support, so the event provides a meaty cross-section of technology and ideas from the sector - from the latest in self-healing materials and electric propulsion, to advances in cabin ventilation and in-flight infotainment
However, the most reassuring aspect of the conference was the clear strategy and direction outlined for aviation by EU government officials and industry executives. Both emphasised that their top level priority is still to create more sustainable means of air transport.
Aviation contributes between 2-3% of man-made CO2 emissions today. Levels of air travel are also predicted to rise by at least eight times by 2050. The EU has therefore committed to reducing the CO2 emissions of aviation by 75% by 2050, alongside a 90% reduction in NOx emissions and a 65% reduction in noise levels.
The EU's flagship technology programme to create more environmentally-friendly aircraft is Clean Skies. The pan-European project has almost 600 participating companies and academic institutions and is receiving a total of €5.76 billion of funding, almost half of which is from the EU.
Clean Skies was launched in 2008, and the first phase of projects are now reaching a mature enough stage to show off results. The programme is split into several themes: wing technologies, propulsion, regional aircraft, helicopters, electrical systems and recycling.
Some of the most eye-catching demonstrators so far have been in the area of engines, where Rolls-Royce and Safran have been leading the development of five engines to reduce fuel burn, noise levels and nitrous oxide emissions. Two are using open rotor configurations, while the others are developing geared turbofan technology, a three-shaft engine with low pressure stages and a turboshaft engine for helicopters.
Artist's impression of aircraft with open rotor engines at the rear
Open rotors represent the largest step-change. An open rotor engine has two parts, a conventional gas generator and a turbine driving two counter-rotating unducted fans through a gearbox. Rig tests conducted recently under Clean Sky programmes have confirmed that open-rotor engines will significantly reduce emissions and noise compared to current generation turbofan engines.
An open rotor engine under development for single-aisle jets from 2025 was shown at the conference which engineers claim will lead to a 40% reduction in fuel-burn per seat. The demonstrator was developed to be suitable for installation at the rear of the aircraft, which presents the challenge of placing the gearbox in a hot section of the engine. Engineers are also working to minimise the weight and size of the engine.
Progress was also shown in the development of a diesel-powered light helicopter. Airbus engineers at Marignane, France, have fitted an EC120 helicopter with a newly designed high compression engine (HCE). The turbocharged V8 has been developed in partnership with French race-car engine maker TEOS Powertrain Engineering.
Preparations for the first flight are underway, and researchers say the HCE has a number of advantages over turboshaft engines, including lower fuel consumption, CO2 emissions and improved performance in extreme conditions because of the superchargers.
The Airbus Helicopters test bed for diesel engine development
Violeta Bulc, the EU commissioner for transport, says aerospace engineers need to make a “quantum leap” in propulsion systems. The other big challenge is how to generate and store electricity on aircraft in the future.
“I know we will soon see hybrid planes,” she says. “I know we don't have all the answers yet, but engineers can come up with the solutions to take care of our environment. The European aviation sector has always been a cradle of innovation, from the early pioneers who established Airbus and gave an incredible push to the industry. Now we are seeing the same with the development of electrification and entirely new aircraft.”
American aims
Reassuringly US aviation research aims broadly echo those of their European counterparts for those of CO2, NOX and noise emissions. Mike Sinnett, vice president of product development at Boeing, points to the incremental improvements in aircraft.
“The goals seem audacious, but they are achievable. Today there has already been a 70% improvement in fuel and 90% reduction in noise. The 737 is a great example. It was conceived 57 years ago, but year-on-year it has been improved by about 3% each year.”
Similarly to the EU's Clean Skies program, Boeing, Nasa and the US government are also collaborating closely with the 'EcoDemonstrator' program. Critically, says Sinnett, it allows the riskier parts of innovation to be done outside of the “critical path” of an aircraft development program.
“It seems like today people are less tolerant of risk within aircraft development program, The media is more interested in our failures than our successes. We have to do it in a way that doesn't attract attention.”
As part of the program, an aircraft is taken out of service and is “loaded-up” with new technologies, taken up into the air and tested. Recent projects have demonstrated laminar flow technology on the wings. Another has looked at recycling, how to reuse aircraft components and waste from production lines.
Fayette Collier from Nasa is the project manager of another sustainable aviation project in the US, the Environmentally Responsible Aviation Programme (ERA). The program, which aims to develop technology which will be integrated into aircraft in 10 - 15 years time, started with 32 proposals, of which eight were progressed between 2012 and this year.
The projects have looked at changing the shape of aircraft: lighter smaller tails to reduce drag, laminar flow wings that reduce the number of insects that get stuck onto them and morphing wings that reduce noise and drag.
“Once you start adding all these technologies, they can have a significant impact on noise and emissions,” says Collins.
Simnett says: “The structure of the airplane and the shape of the aircraft has been tight over the last thirty years. But the development of materials technology means we can have wings that give us better aerodynamic lines, structural loads. Combined with the ultra high bypass ratio enignes will unleash the power of improved efficiencies over the next thirty years.”