Etihad's sound investment

A research programme has seen Etihad Airways, Boeing, NASA and Safran banding together to reduce noise emissions from future generations of airliners. Alan Dron has been finding out more.

Picture: Boeing

With the global pandemic dominating the headlines in 2020, it is easy to forget that only a year ago, the big issue was the environment.

That situation has not changed. When coronavirus has been dealt with by the world community, the need to improve airliners’ environmental credentials will still have to be addressed.

With that in mind, the latest in a series of Boeing aircraft to bear the ecoDemonstrator title undertook a number of test flights in the US in September, using a fresh-off-the-production-line Etihad Airways 787-10.

The aircraft operated the flights in September, before it was formally handed over to Abu Dhabi-based Etihad. Other key partners included NASA and France’s Safran Landing Systems.

The ecoDemonstrator programme extends back almost 10 years and aims to accelerate innovation by taking promising technologies out of the laboratory and testing them in the air to improve sustainability for airlines, passengers and the environment.

Over the years, Boeing has taken a succession of aircraft and tested new technologies on them with the aim of making flying safer, more economical and less intrusive.

Around one-third of the technologies tested on ecoDemonstrator aircraft have found their way into production. Among improvements to have materialised are the winglets now seen on the tips of the latest-generation 737 MAXs.

The manufacturer works with partners from the aviation industry, government and airlines to develop these new measures.

The 2020 programme with Etihad expanded a strategic sustainability alliance the two companies formed in autumn 2019 at the Dubai Air Show.

At the show, Etihad and Boeing announced the ‘Etihad Greenliner’, which is being used by the companies to explore and assess sustainability initiatives while the aircraft operates scheduled services across the airline’s network.

Other stakeholders, from equipment suppliers to airspace regulators, are being invited to join the companies in advancing and testing efficiency measures on or with the Greenliner.

One of aviation’s biggest bugbears, especially for residents who live close to airports, is noise. Even with steady reductions – compare the decibels created by a Boeing 707 in the early 1960s with those of a modern wide-body – take-offs and landings continue to cause disruption for large numbers of people around the world.

Noise formed the core of this year’s programme of work.

“A 787-10 was taken over to Seattle, where it was configured for these trials,” said Rami Awadalla, Etihad’s director of fleet engineering. “They had to install around 200 microphones, spread across the front of the fuselage and on the belly.”

The aircraft then flew to Boeing’s facility at Glasgow Industrial Airport, Montana – a former Strategic Air Command base – where the runway and surrounding area had been outfitted with another 1,000 microphones to record the aircraft’s noise levels. In the space of eight days, the 787 made 88 passes over the microphone array in more than 60 configurations, with differing flap settings and engine thrust levels, and with the undercarriage retracted or lowered.

The 787 flew in a racetrack pattern over the airport, each time passing over the microphones between 600 to 800 feet above the ground. This low altitude improved the quality of the data collected.

“It’s a balance between low enough for a good quality signal and not being too low for safety reasons,” said Russell Thomas, an acoustics expert at NASA’s Langley Research Center in Virginia, who led what is officially called the propulsion airframe aeroacoustics and aircraft system noise flight test.

All the test flights were operated using 50,000 gallons of a 50-50 blend of standard fuel and a sustainable aviation fuel made from agricultural waste.

“This is an opportunity we get very rarely,” said Thomas. “It’s not possible to put an aircraft the size of a 787 in a wind tunnel or rely solely on computer simulations that may not perfectly represent reality.

“Only by flying can we obtain the most realistic conditions for obtaining the measurements we need. And this is really the first time we’ve ever been able to attempt the kind of research we’ve planned."

“This is pushing the boundaries of acoustic flight-testing. I don’t think either NASA or Boeing has ever put so many microphones on the ground or on the aircraft.”

The testing generated 1.6 terabytes of noise data. Such a huge amount will require considerable analysis, but will eventually be used to improve NASA’s aircraft noise prediction capabilities, as well as create lessons for pilots to reduce noise and feed into future quiet aircraft designs.

One particular field of study was in trying to quieten the levels that occur when an aircraft’s undercarriage is lowered. Up to 30% of noise from aircraft on approach to a runway is caused by air flowing around the landing gear.

The undercarriage legs, struts and assorted pipes, create considerable air turbulence; as aircraft engines have become progressively quieter over the years, this undercarriage-generated problem has become an increasingly large component of the overall noise generated by an aircraft as it lands.

With this in mind, Etihad’s 787 was outfitted with a series of fairings around components of the landing gear. Designed by Safran Landing Systems, the perforated fairings covered part of the nose landing gear, while aerofoil-shaped panels wrapped around struts on the main gear, with the aim of smoothing out the airflow.

This part of the programme will also look at future designs of undercarriage that could eliminate some of the gaps and holes around the gear, together with rerouting items such as hydraulic tubes, to try to cut down the whistling sound that the airflow creates when passing over them.

Eight acoustic sensors mounted on the landing gear augmented the 1,200 microphones used on the aircraft fuselage and on the ground.
Data from the testing must be analysed, but preliminary results were said to be positive and observers on the ground reported a noticeable reduction in noise.

The aircraft was flown by Boeing pilots and space was cleared in part of the cabin for engineers and their equipment racks, to help record the data.

As well as the noise experiments, the ecoDemonstrator was also used to test some of the latest wellness techniques, Awadalla added.

One of these was a new type of anti-virus treatment for flightdecks. Designed by Boeing, it is an ultraviolet (UV) wand that a technician or cleaner can pass over high-touch areas in the flightdeck to kill any bacteria or viruses.

Boeing designed and developed the UV wand as part of its confident travel initiative (CTI) to support customers and enhance the safety and well-being of passengers and crews during the Covid-19 pandemic.

The self-contained apparatus resembles a carry-on suitcase. Crews pass UV light over high-touch surfaces, sanitising everywhere the light reaches. The UV wand can disinfect a flightdeck in less than 15 minutes, said Boeing. It eliminates the need to use liquid disinfectants on sensitive electronic panels or display screens.

Boeing has now signed a deal with Florida-based Healthe, which will manufacture and distribute the wand.

“Boeing spent six months transforming an idea for the wand into a working model, and Healthe will now take that prototype and make it available to the world at large,” said Mike Delaney, who leads Boeing’s CTI efforts. The wand could be ready for sale to airlines before the end of the year.

Etihad’s 787, meanwhile, has reverted to its normal duties of carrying passengers, having played a small part in making life more comfortable for future residents living near airports.