Boosting aerodynamic efficiency is the cornerstone of Boeing’s latest battery of ecoDemonstrator test flights. The tests are being carried out on a near-end-of-life 757 that will later be used to test new aircraft-recycling techniques, before being consigned to history.
The 757 is the third aircraft type to undergo ecoDemonstrator test flights, following earlier programmes involving a 737-800 in 2012 and a 787 in 2014. While the 737 flights were carried out in conjunction with American Airlines, and the 787 flights were run under the US Federal Aviation Administration’s continuous lower energy, emissions and noise (CLEEN) programme, Boeing has chosen a European airline partner – TUI Travel – to work with on the 757 tests.
The overall aim of the ecoDemonstrator programme, says Boeing Commercial Airplanes director of environmental performance Jeanne Yu, is to speed up the implementation of fuel-saving technologies in aviation, and “inspire people to action” on developing more environmentally friendly aircraft.
Whereas the 737 ecoDemonstrator focused strongly on adaptive wing and regenerative fuel cell technologies, and the subsequent 787 programme concentrated on ceramic matrix composite (CMC) nozzle design, the latest round of testing will look at ways of reducing environmental effects on natural laminar flow. A key piece of this research involves the application of various insect-repelling, or “bug-phobic”, coatings to the leading edge of the aircraft’s left wing to try to reduce drag by minimising the amount of insect residue.
“Any bug you have on an airplane will affect drag,” says Yu, adding that a total of five different “microscopically adhered” coatings will be tested. The bug-phobic testing is being carried out in conjunction with NASA’s environmentally responsible aviation (ERA) project. Sections of the various coatings will be applied to the leading edge slats, after establishing a baseline by using uncoated surfaces to capture insect-accumulation levels. Durability of the coatings will be examined to see how they withstand flight conditions.
The coatings will be tested on 15 separate flights, taking place throughout June and coming to an end in July. These tests will be carried out in Shreveport, Louisiana, a location chosen because of its high insect levels. Shreveport was selected from 90 candidate airports on account of its “runway length, temperature, humidity, weather, ability to handle a 757 aircraft and thunderstorm frequency”, says NASA. Knowledge gained by NASA – with the exception of anything that uses Boeing’s proprietary technology – will later be made publicly available to benefit the entire industry.
Another set of 757 ecoDemonstrator tests, which was completed in April, focused on active flow control. These tests involved installing 31 actuators to force jets of air on to the aircraft’s vertical tail and rudder surfaces, the aim being to reduce the size and weight of the tail that is needed by generating the same side force during take-off and landing that a larger tail provides.
757 ecoDemonstrator, TUI colours
Boeing
The results of the nine test flights carried out in Seattle are now being analysed. However, NASA expects them to confirm the findings of an earlier wind tunnel test, which showed that the active flow control jets could increase side force by 20-30%. “A 20% increase in side force could allow designers to scale down the vertical tail by about 17% and reduce fuel usage by as much as 0.5%,” says NASA.
“Solutions to reduce fuel use by 1% or 2% may not sound like much,” says Fay Collier, manager of NASA’s ERA project. “But shaving aircraft fuel consumption by even a few percentage points can save millions of dollars and help protect the environment from harmful emissions,” says Fay Collier, manager of NASA’s ERA project.
The two NASA experiments on board the 757 ecoDemonstrator form part of eight ERA technology demonstrations that are being conducted this year and will bring the project to a close. The eight demonstrations span five focus areas: aircraft drag reduction; weight reduction through use of advanced composites; fuel and noise reduction through advanced engines; emissions reductions through improved engine combustors; and fuel and noise reduction through aircraft configuration changes. With all eight of its demonstrations, NASA aims to mature the technologies to the point where there would be less risk for aircraft manufacturers to incorporate them into future designs.
“Having a relevant test bed, such as Boeing’s ecoDemonstrator, to help mature technology concepts is extremely important to NASA’s environmentally responsible aviation project,” says Collier. “Our researchers have been working hard to develop technologies to reduce airplane fuel consumption, noise and emissions. Being able to prove those concepts in flight tests gives them a better shot of getting into the commercial fleet.”
A total of 15 different technologies will be tested as part of the 757 ecoDemonstrator programme, compared with 32 technologies on the 787 platform and 12 on the 737. Some of the previously tested technologies have already been – or soon will be – put into practice, says Yu. These include an “advanced technology winglet” concept that was tested on the 737 ecoDemonstrator and was later “transitioned right into the baseline design for the 737 Max”. The new winglet can improve fuel efficiency by as much as 1.8%, says Boeing.
In addition, a new lightweight material that was installed under the aft wing section of the 787 ecoDemonstrator aircraft “will be wrapped into production” of future 787s, says Yu. “We plan to see this flying on the 787 in the next year,” she adds.
“A lot of the technologies will be seen on multiple airplanes, with some near-term and some longer-term timelines,” says Yu. “Transitions will happen at different times. For example, we probably won’t see fuel cells for another 15 years. The main thing is to speed up implementation.”
Boeing deliberately chose a 757 that was nearing the end of its commercial life to be its latest ecoDemonstrator test bed because, once the flight tests have been completed, the airframer plans to work with the Aircraft Fleet Recycling Association (AFRA) to look at new recycling methods. “We’re hoping that in parting it out we will learn more about how to recycle,” says Yu.
In mid-2010 AFRA set an ambitious target for 90% of the materials salvaged from scrapped aircraft to be recycled – preferably into products in the aviation supply chain – by 2016.
Boeing has already made some headway on finding new uses for scrapped carbonfibre, an example of which could be seen on the 787 ecoDemonstrator aircraft. Small access doors on the underside of the ecoDemonstrator’s wings were manufactured using excess carbonfibre from the production of trailing edges for the 787 at Boeing Aerostructures Australia. Boeing says this was the first time that recycled carbonfibre from aerospace parts had been recycled for commercial aircraft use. “We’re trying to find new uses for carbonfibre and we continue to look at that,” says Yu.
Once the latest round of ecoDemonstrator test flights comes to an end in July, Boeing and its partners will analyse the results to try to work out which technologies can be transitioned to commercial-use platforms, and when. Yu says the airframer is “not talking about” any other possible future ecoDemonstrator programmes at this stage, but “will likely start doing smaller demos and ground demos” in the meantime “to fill in the gap”.
Source: FlightGlobal.com
