Every so often, a rather special aircraft takes off from Boeing’s main plant in Seattle. It has no paying passengers, no cabin crew, and no destination. The 757 climbs into the sky, flies for a short period, and then promptly returns to where it came from.
This seemingly pointless journey actually provides Boeing with an enormous amount of valuable data. That’s because the aircraft in question is the ecoDemonstrator – a flying testbed kitted out with dozens of new technologies that might one day make it on to commercial programmes.
The ecoDemonstrator was used to evaluate natural laminar flow, which translated into a novel type of winglet on the 737 Max. And it once carried a new design of broadband antenna, which led to the creation of a multi-bandwidth radome now fitted to the Dreamliner. The ecoDemonsrator is the ultimate flying laboratory, a reconfigurable home for innovation that enables Boeing to bring bright ideas to life.
“It’s a unique programme because it provides us with a basis where we can take technologies that are being developed in a laboratory and deploy them on an actual flying asset to demonstrate their usefulness,” says Mike Sinnett, Boeing’s vice-president of product development. “A number of interesting technologies have made the transition from ecoDemonstrator and onto our commercial airplanes. Some make it, others don’t. It’s our chance to give them a try.”
Sinnett points to the development of a natural laminar flow advanced winglet that is now flying on the 737 Max as a good example of that transition. “We spend a lot of time looking at the smooth part of the airflow, where it flows over the surface of an aircraft structure before becoming turbulent and causing more drag. In this demonstration, we developed the manufacturing technology and the surface treatment to allow for laminar flow over a larger portion of the winglet than had ever been possible before. That testing went from development to demonstration and then directly onto a new airplane.”
Blueprint revealed
The ecoDemonstrator effectively provides a fascinating insight into Boeing’s blueprint for the future of aviation. The innovation frontiers being explored onboard cover a wide range of areas, from future propulsion concepts and advanced materials through to efficiency of flight and maintenance crews and the development of sustainable fuels. In fact, there are virtually no areas of Boeing’s civil aerospace operations that aren’t informed by the technology trials that are being carried out onboard.
Efficiency of flight and maintenance crews is a case in point. Here Boeing has deployed a capability that allows it to provide airborne flight crews with information to enable them to improve their routeing to save time and distance travelled. For example, it is possible to look at weather wind models, and the pattern of aeroplanes cleared for flight, and to determine a better path through prevailing conditions.
“That information is processed on the ground and provided by a datalink to the aircraft in flight,” says Sinnett. “It allows us to take time off flying. It may only be minutes between two way-points that are two or three hundred miles apart, but over a vast period that adds up to meaningful fuel and time savings.”
The datalink for that technology was proved out on the ecoDemonstrator, and Boeing is now looking at other ways that operational efficiency of crews might be improved in the mid-term. “We’ve already begun to remove a significant amount of paper from the pilot environment by allowing electronic maps and flight planning, and we are transitioning that into maintenance planning and electronic log books that allow the maintainers of the aircraft to eliminate the paper in their process as well,” says Sinnett.
“Then, in the far term, we are thinking about better operational control of the airplane and co-operative behaviour between aircraft while they are airborne through a technology called 4D precise navigation control. On an ecoDemonstrator last summer we showed software functionality developed by Nasa called AStar that lets aircraft coordinate their approach paths with each other to ensure that they arrive at a specified point at a specified time to allow more closely spaced arrivals, which improves efficiency at airports.”
Cutting fuel costs
“That technology is not ready for prime-time yet, but we have demonstrated that we can make it work. Eventually it will lead to reduced fuel burn on approach. At present, this is one of the most highly fuel inefficient phases of flight, when the aircraft is in a very high drag state with the landing gear down and the high-lift devices deployed.”
Even further into the future, Boeing says it is thinking about aeroplanes that can fly in formation, reducing fuel burn on the trailing aircraft. Sinnett says: “While that may not be something that we choose to do in the near future for passenger transport, it may very well be something we do to take advantage of freighter operations in a trans-oceanic environment. You can imagine three or four freighters flying together with two or three of them drafting in the wake of the lead plane. We are working with our customers on these concepts today.”
Improving the cabin experience is also a major area of investigation on ecoDemonstrator flights. On the 787, Boeing did a lot of work to improve humidity, and on the purification of recirculated air through a system that scrubs volatile organic compounds. Those technologies are now being deployed on new programmes such as the 777X. Other advances now flown include improved LED lighting that can provide an infinite palate of colours, and novel hinge and pivot mechanisms which allow passengers 50% more space in the overhead lockers.
More radically, Boeing is looking at how it might integrate sound and lighting to make better use of more of the interior of the plane as a projection space for images. “You could, for example, have scenes projected of the cities that you are flying into on the bulkhead walls,” says Sinnett. “It could offer information about street scenes, with music playing from the local environment, integrated with information about your arrival – temperature, connecting gate information, that sort of thing – all displayed on usable spaces inside the passenger cabin. The integration of sight and sound in ways that haven’t been done before are concepts we are looking at on ecoDemonstrator.”
Aircraft exteriors are also being looked at. Laminar flow, the smooth, uninterrupted flow of air over the contour of the wings, fuselage, or other parts of an aircraft in flight, is a strong focus of research. That very particular phase of airflow is difficult to achieve on a wing in flight, and once it is achieved it is very easy to lose it through effects such as surface contamination. So Boeing modified the left wing of an ecoDemonstrator aircraft to provide a different sweep angle on a significant portion of the wing.
By removing the typical leading-edge slats and installing what are known as Krueger leading-edge devices, it was possible to shield the leading edge from residue caused by dead insects. By installing a tripod and camera on top of the plane with infrared capability while the craft was in the air, it was possible to determine the extent of laminar flow as a function of Mach number and sweep angle, and to monitor the effect of insect contamination to try to work out a practical solution.
Making wings insect-proof
“While we were doing all that work on one wing of the airplane,” says Sinnett, “on the other wing we were testing coatings from Nasa that allow bug residue to come off the airplane rather than sticking. We tested multiple versions of bug-phobic coatings on one wing, and high-speed laminar flow on the other. That’s great research information.”
Boeing is also looking at advanced flow control. By using bleed air from the auxiliary power unit to re-energise flow as it moves over the rudder, it might be possible to enable the rudder to be more effective at varying angles or allow the use of a smaller rudder and tail.
“This science will allow us to design architectures with smaller control surfaces,” says Sinnett.
Advanced materials use is also being researched onboard the ecoDemonstrator, using the aircraft to demonstrate the feasibility of recycling carbon fibre for non-primary structures such as fuel tank access doors. Boeing says it has taken carbon-fibre scrap out of the 787 Dreamliner production system and reused it on the ecoDemonstrator. “It’s to prove a process by which we can recapture the material, reform it, and qualify it as airworthy,” he says.
Furthermore, the ecoDemonstrator helped prove a ceramic matrix composite that was used to produce an exhaust plug that now flies on the Trent 1000 engine on a 787. “Ceramic matrix composites are neat materials that have very high operating temperature properties out to 1,500°F but at 20% less weight than titanium,” he says. “It’s a structure that feels like a ceramic but behaves like a metal. You can drive a nail through it without shattering it. We were very happy with its thermal performance and now we have a lot of applications.”
And finally, there are sustainable biofuels. So far, more than 1,600 aircraft operations have been flown using what Boeing describes as green fuels. “We are trying to come up with other materials that can be used for biofuels, looking for different feedstocks,” says Sinnett. “In the far term we are thinking beyond liquid fuels, about electric propulsion, fuel cells, and other alternatives such as liquefied natural gas and hydrogen. We’ve had demonstrators flying with some of these fuels.
“There’s a lot of opportunity to reduce our reliance on kerosene.”
Boeing not convinced by blended wings Boeing is unlikely to pursue the blended wing as a serious design option for a future civil airliner because of configuration and consumer acceptance issues.
Mike Sinnett, Boeing’s vice-president of product development, says blended-wing configurations are still being evaluated within his organisation. However, he casts doubt over whether they would ever result in the introduction of a radical shaped passenger plane.
“Blended wing for future aircraft programmes has been the mantra of almost everyone, except airplane designers,” he says. “I know a lot of people want to see them because they look cool.
“But the studies we have conducted have led us to believe that for commercial transport applications, with the technologies available today, the blended wing would not be as efficient a configuration as more traditional designs. We’ve done the studies to show that.”
Sinnett says that blended-wing designs present acceptability problems, with passengers unwilling to sit in windowless environments. “If you are further outboard from the centre of gravity from the airplane, as it banks and rolls, there is a significant amount of up and down movement for the passengers, so that’s a ride quality issue. Also, how are you able to evacuate an aircraft like that in the same amount of time that’s required to evacuate a plane today?
“Those are two practical examples of things that so far have stood in the way of us being able to configure an airplane to take advantage of blended-wing aerodynamics. So at an airplane level, when we finally meet all the requirements, the blended-wing concept is no longer a winner from an efficiency standpoint.”
That might be true of passenger planes, but Sinnett believes the blended wing might still have a role for freighter or military programmes. “It’s about having the right tool for the job,” he says.
In terms of a possible future supersonic passenger aircraft, Boeing is working with Nasa on low-boom technologies to get over acoustic constraints. “I’m pretty sure we will see commercial supersonic flight again – I just don’t know when,” says Sinnett.
“We are working with Nasa on low-boom technology to reduce the acoustic impact of supersonic flight. We are also developing advanced propulsion techniques that will allow us to return to commercial supersonic flight in a practical and cost-effective way. It’s one of those things that we continue to look at as we evaluate new technology.”