Date:31 July 2006
The aircraft of the future will be stronger, safer and smarter. With refuse-to-crash technology and radical new flight controls, flying may some day be as easy as driving.
Nasa research pilot Craig Bomben was flying at 6 000 m under a clear, blue desert sky this past March when a sudden lurch rocked his highly modified F-15 Eagle fighter jet. The plane’s nose jerked sickeningly upward, a sign that the aircraft had suffered one of the worst possible malfunctions: Part of the stabilator, the combination horizontal stabiliser/ elevator that controls up-and-down motion, had jammed. “It’s not something a pilot ever wants to feel,” Bomben recalled later. “You can lose your stabilator a bunch of ways – computer failure, stuck actuator, missile up the tailpipe – but when you lose it, you’re out of luck. You’re not going to fly the airplane home.”
Fortunately for Bomben, his flight mission was to test technology that could help pilots of the future cope with just such problems. Developed at Nasa’s Dryden Flight Research Centre at Edwards air base on the US West Coast, the Intelligent Flight Control System utilises an on-board neural network to adapt to unexpected failures. Within one-80th of a second, it had detected the deliberately triggered malfunction on Bomben’s F-15. In less than 2 seconds, it had figured out how to use other control surfaces – rudder and ailerons – to compensate for the jammed stabilator. “There was a small degradation with the flying qualities at first,” Bomben says. “But, within 30 seconds, the plane was flying identically to a base-line Eagle.”
Nasa’s advanced flight control system is part of a wave of technologies now moving off the drawing board and toward reality, via test benches, wind tunnels and scale-model experimentation. Individually, each of these innovations could help make air travel safer and more efficient. Collectively, they could revolutionise it.
Since the dawn of aviation, bold souls have been trying to do for planes what Henry Ford did for the car – make them widely accessible. But that vision always ran foul of a hard reality: the technology just wasn’t there. No matter how you put them together, planes are just too difficult to fl y and too expensive to build to qualify as realistic mass transportation, and managing swarms of them in already congested airspace seems an impossible task. But finally, the day is drawing near when all the pieces come together and we reach that long-elusive goal – the aircraft for the everyman.
No one yet knows what this craft will look like, though some have already begun to make educated guesses. (See “The Plane of the Future,” page 5, for some of the forward-thinking designs PM solicited from amateur and professional aircraft designers.) The wait may not be all that long. Engineers at Nasa and at major aerospace contractors, such as Boeing and Lockheed Martin, have started putting pen to paper to determine how the future may play out.
A report prepared by Nasa’s Langley Research Centre recently assessed future demand for Personal Air Vehicles (PAVs). Such aircraft may be one way to cut the Gordian knot of ever-denser land traffic, the report concludes. As we travel more and more, it takes us longer and longer to get where we’re going. Over the next 20 years, for instance, highway speeds in a big metropolis such as Los Angeles are projected to drop by a third, from 50 to 35 km/h. Although it may not be practical to abandon the freeways for the skyways to get to work, PAVs could provide the means for those who would like to take a day trip to the countryside.
In an ideal system, ordinary people will be able to climb into their own planes, take off from small airstrips, and fly anywhere from 150 to 750 km at speeds of up to 300 km/h. Either the planes will fly themselves, or the task of piloting will be so heavily automated even a minimally trained person would be able to master it. Mass production could bring the cost down so much that millions of citizens in developed countries could afford their own aircraft. Though the cost of fuel is still a wild card, the Langley study forecasts the price of a PAV will drop as low as R500 000 to R750 000.
“Remember when people talked about mass transportation systems based on remotely piloted cars?” says Frank Cappuccio, executive vice president of Lockheed Martin’s advanced development programs office, Skunk Works. “We might skip that and go straight to planes.”
To look down one path to the future of aviation, drive to the end of the Virginia Peninsula, an hour and a half southeast of Richmond, and pull into the parking lot of the Langley Research Centre. Inside a three-storey room equipped with a crane and a six-axis motion simulator, engineers are tweaking a mockup of what could be the next generation of aircraft cockpits. Called Synthetic Vision System, this simulated flight deck is designed to give a pilot total situational awareness – even in fog, clouds and pitch-black conditions.
The head-up display technology on which the system is based has been available in commercial airliners since the 1970s, feeding pilots information on altitude, heading and speed. What’s novel about Synthetic Vision is the integration of systems that also provide data on the location of nearby aircraft, and render a computerised view of the terrain to provide a clear sense of the plane’s location regardless of visibility. Punch in the destination and a virtual route appears on the display – a 3D “highway in the sky” down which pilots can steer.
Later this year, Langley will begin work on Integrated Intelligent Flight Deck Technologies, which is even more sophisticated. It will patch in real-time weather data and link to an advanced system of air traffic control. The Next Generation Air Transportation System, which Nasa and the Federal Aviation Administration plan to introduce by 2025, will replace today’s fixed routes and controller-to-aircraft voice communication with zones of free-flowing traffic, and will automatically connect ground-based flight control computers to aircraft avionics via data uplink. Instead of telling a pilot where to go, air traffic control will simply send the data straight to the cockpit display.
The purpose of these projects is to take the most dangerous and difficult functions out of the hands of the pilot and shift them to the aircraft’s electronic nerve centre – an essential step toward the day when planes become as easy to operate as cars. “Our goal is to optimise situational awareness and reduce the likelihood of pilot error,” says Steve Young, principal investigator for Integrated Intelligent Flight Deck Technologies. “Pilot errors occur because we’re human. But if we design a system in the right way, we can minimise the risk of those (errors) happening.”
At the Wallops Flight Facility on Virginia’s eastern shore, another Langley team is exploring more radical improvements in flight control. Dubbed “refuse to crash” technology, the team’s Integrated Resilient Aircraft Control will soon be tested on a scale model of a passenger jet. Like Synthetic Vision, the system will be able to monitor a plane’s overall situation, but – when necessary – can take over to prevent a collision. It will also be able to prevent the plane from slipping into a stall or a spin that would cause the pilot to lose control of the craft.
“It’s like a horse,” says Brien A Seeley, president of the CAFE Foundation, which promotes the development of Personal Air Vehicles. “An airplane equipped with this technology will refuse to do something to cause itself harm.”
Even if human error can be removed from the equation entirely, mechanical failure means that flying will always involve a certain amount of risk. If millions of people are going to clog the airways, planes will need to be more durable than ever. Technologies such as Dryden’s Intelligent Flight Control System will prove invaluable in helping damaged or malfunctioning aircraft reach their destinations safely. But it would be far
better if breakdowns could be eliminated altogether.
The solution may lie in something called Integrated Health Management – technology that allows a machine to help maintain itself.
For years, cars have been equipped with dozens of sensors and microprocessors that can detect when a mechanical fault has occurred. On some cars, data from on-board diagnostic computers can be uploaded to their manufacturers’ processing centre, where technicians are on standby to talk drivers through any problems.
In the future, airplanes and other complex machines will be able to manage their own health in far more sophisticated ways.
At a Navy test facility in Patuxent River, Maryland, researchers deliberately introduce tiny cracks into turbine fan blades to determine whether a health management system can monitor the cracks’ growth and accurately predict the turbine’s failure. The experiment is part of an initiative from Darpa, the central research organisation for the US Department of Defence, to develop advanced prognostics. Currently, an engine might have to be overhauled if any cracks are found in the blades. But if a system can calculate that a given crack presents no immediate danger, the plane could fly longer before being serviced.
“And if something does go wrong, the system will immediately respond and give you a real-time indication of what the problem is,” says Leo Christodoulou, manager of Darpa’s prognosis programme. “Today, the pilot may get a warning light. In the future, the system might tell you what’s wrong and what you can do about it.”
A PAV that finds itself in trouble, for instance, could alert the pilot to how much time remains before a malfunction becomes critical, and provide a list of airports within range where it could be repaired. Aircraft may even incorporate ways to mend themselves.
“A sophisticated system might utilise a self-healing material, so if cracks start to form, capsules will break and release adhesive to close them,” says Carolyn Mercer, co-principal investigator for the Aeronautic Vehicle Integrated Health Management System at Nasa’s Glenn Research Centre.
Although a plane that heals itself sounds pretty clever, what most people are really waiting for is a plane that flies itself. “Not everybody’s going to be willing to go through pilot training,” says Lockheed Martin’s Cappuccio. To make Personal Air Vehicles a reality for mainstream America, engineers will have to eliminate the need for a pilot – or at least make flying so easy that anyone with a driver’s licence will be able to do it.
Avionics has already developed enough for Unmanned Aerial Vehicles (UAVs) to routinely take off, fly and land on their own. PAVs will probably evolve from the same control systems. Northrop Grumman’s Global Hawk UAV, for instance, can be as easy to operate as a Web browser. “You don’t need any pilot skills,” says Rick Ludwig, director of the company’s unmanned systems division. “You take your mouse, put the cursor over the place on the map where you want to go, and click. Your vehicle will navigate there.”
The military is now testing a vertical take-off UAV called Fire Scout, which can be programmed to carry supplies to a remote location, land, and wait for a special operations team to retrieve the delivery. A civilian version may one day haul freight or even messenger packages short distances. Once reliability is established, pilotless planes will eventually be trusted to carry human beings – though many experts caution that this is still a long way off. After all, Ludwig says, “how many passengers are going to walk on to an airplane that has nobody in the cockpit?”
The incredible advances in avionics will alter how planes fly, not how they look. But radical new materials and fabrication techniques could lead to a generation of aircraft whose shapes not only appear significantly different, but also change during flight.
Recently, engineers working for a small Southern California startup called NextGen Aeronautics hoisted a 550 kg wing into a wind tunnel at Langley’s facility in Virginia. As massive fans sucked air through the 5 m-wide tunnel at nearly the speed of sound, the wing underwent an astounding transformation. Guided by actuators buried inside, the wing’s complicated structure of aluminium lattices expanded and compressed – stretching and shrinking the wing’s silicone-rubber skin. The tips of the wings moved forward and back, changing the wingspan as well as the chord, or distance from leading to trailing edge.
“We were able to change the area by more than 50 per cent,” says NextGen founder and president Jayanth N Kudva. “Five years ago, no one thought that was possible. Soon, we’ll be able to change the shape of the airfoil as well.”
This morphing process has the potential to let a single plane fulfil a variety of roles. The military is interested in building aircraft that can change from a surveillance platform, circling high and slow with a broad wingspan, to a high-speed attack plane that tucks its wings like a hawk diving for prey. Aircraft such as the F-14 Tomcat have already utilised morphing – in the form of wings that sweep back to reduce drag – but the purpose was to optimise performance, not to change the vehicle’s basic mission.
NextGen is planning to test a scale model of its wing later this year; Lockheed Martin – under the same Darpa programme to explore the potential of morphing – is developing a concept that will tuck the inner portion of the wing into the fuselage, leaving only a short length of wingtip exposed to the airstream. (See “Morphing in Air” below.)
While current research is focused on military applications, morphing wing technology could profoundly alter civil aviation – proving invaluable for PAVs, too. “Airplanes are designed to cruise at one altitude and one Mach number,” Kudva says. “But as flight conditions change, planes could change shape continuously to optimise efficiency at all times.” For example, wings will be long to generate maximum lift at take-off and landing, when safety dictates low airspeed; when cruising at high speed, sweptback wings will maximise fuel economy.
To accomplish this feat, aircraft will be built not only of aluminium alloys and advanced composites, but of shape-memory polymers and plastics. Like a bird in flight, which constantly adjusts its wings to compensate for gusts and patches of lift, the aircraft of the future will be in a constant state of change, altering the shape of its wings and control surfaces, and narrowing or flaring its engine exhausts.
Not all of these technologies will make it into the air. And many others, as yet unforeseeable, will doubtless take us by surprise. If someone tries to sell you a self-piloting plane tomorrow, back away slowly. It will be at least two decades before the pieces come together. But when they do, we could be in for the most exciting time in aviation since Orville Wright made the first tenuous flight.
“There’s going to be a major change in society’s mindset,” says Seeley of the CAFE Foundation. “When the convenience and practicality and cost converge to make PAVs attractive, it will be a natural revolution, like the adoption of cellphones. In 20 to 30 years, we’re going to see an exponential increase in our ability to move through the air.”
Morphing in air
It’s two planes in one: Lockheed Martin’s 4,5 m remote-control aircraft, developed at the company’s Skunk Works facility, uses double-hinged wings to radically alter its shape in flight. With the wings fully extended, the vehicle is optimised for high-altitude, long-loiter missions. With the inner sections folded against the fuselage, the plane becomes a high-speed ground-attack aircraft. Veriflex and Veritex polymers change shape to ensure a streamlined profile. The craft crashed while taxiing during tests last year, but the repaired vehicle should be ready for flight this summer. Eventually, similar technology will make Personal Air Vehicles more flexible in evolving weather conditions, improving the way c
ivilians fly, too.
The plane of the future
With Personal Air Vehicles still a generation away, it’s anyone’s guess as to what form they might take. For some notion of what’s to come, PM turned to Austin Meyer, the man behind X-Plane – a flight simulator program