I FEEL dizzy. I鈥檝e never flown a Boeing 757 before, and as I descend into Reno/Tahoe International Airport in Nevada it feels as if we are swinging all over the sky. Worse, it is dusk and we are dropping through muddy cloud that limits visibility to an arm鈥檚 length. Out there somewhere are mountains thousands of metres high.
But when I look ahead I see a cloudless sky and crisp green mountains surrounding the grey runway below me. There is something else too: my direction and speed are displayed on indicators that seem to float in mid-air. There is even a line of purple chevrons that disappear into the distance, guiding me down towards the runway like markings on an invisible highway in the sky. This is NASA鈥檚 Synthetic Vision Systems (SVS) in action, a technology designed to fundamentally change how we look at the world.
Electronic screens such as head-up displays 鈥� a transparent panel mounted in front of the windscreen that allows pilots to see their instruments while keeping an eye on goings-on in the real world 鈥� have been around for years. SVS, however, dispenses with the real entirely. Instead it shows the pilot a highly detailed simulation of the world outside created by fusing real-time images from radar, infrared sensors and a huge 3D digital map. With this system, clouds and thunderstorms melt away. Night becomes day. Every twist and turn of a flight, and every potential hazard, can be pointed out in big, red, flashing letters. The windscreen remains, but with SVS on board a pilot need never look through it.
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My Boeing is just a flight simulator at NASA鈥檚 Langley Research Center in Hampton, Virginia. But SVS has already guided real aircraft onto real runways, and the pilots involved gave it rave reviews. If all goes to plan, the system could be operational by 2006, enhancing safety, helping to cut fuel bills and allowing airlines to carry more passengers with fewer delays.
The display is based on the largest, most detailed map ever created. It was generated in 2000 using radar mounted on the space shuttle Endeavour, and recorded the topography of 80 per cent of the Earth鈥檚 surface to a resolution of 30 metres. By adding realistic colour and reference points, such as railways, rivers, towns, cities and roads, NASA has created a photorealistic 3D map of most of the world. All the map data needed for a flight is stored on a server aboard the aircraft. The simulator I鈥檝e just tested, for example, relies on a server loaded with 8 gigabytes of data.
But even the best map is useless if you don鈥檛 know where you are. So twice a second the system takes GPS measurements accurate to 3 metres or so. These are enhanced by information from the inertial navigation system, which calculates the aircraft鈥檚 position 50 times every second. With position, altitude and direction plotted precisely, the SVS can then digitally recreate and display the view ahead on a screen in front of the pilot. 鈥淛ust as the world moves under the aircraft as you look out the window, so does our synthetic world,鈥� says Randy Bailey, a lead engineer on the SVS project. The advantage of using a digital map rather than live pictures from a camera mounted outside the aircraft is that the view is always perfect, even at night or in fog. 鈥淐onsider the image as a porthole looking at the world, but unencumbered by clouds or other weather,鈥� says Bailey.
鈥淲ith this system, clouds and thunderstorms melt away. Night becomes day鈥�
This is a porthole, though, with all sorts of added extras. Once you have programmed in your destination, SVS adds digital markers indicating the optimum flight path and approach route for landing. It also superimposes real-time information such as speed and direction, information from forward-looking infrared detectors that can pick up things such as runway lights and hills, and data from a radar system that can identify storms or other aircraft (see Diagram). SVS also picks up transmissions from an aircraft-signalling system called Automatic Dependent Surveillance-Broadcast. Every plane equipped with ADS-B transmits its location, altitude, speed and potential path to other aircraft, and SVS uses this data to highlight any risk of collision. The result is a digitally generated highway through the sky, complete with road markings, hazard indicators and signposts.
SVS is not just for flight and landing. Its Runway Incursion Prevention System keeps aircraft safe on the ground too. This contains digital maps of every major airport, accurate to within about 30 centimetres. During the final approach the system highlights runway edges and centre lines, and once the aircraft touches down it displays the taxi route. Most importantly it indicates the presence of nearby aircraft or vehicles, and is designed to prevent collisions on the ground. It even displays spoken instructions from air traffic control as text, thanks to a built-in voice recognition system.
Last summer a group of airline pilots tested SVS for real 鈥� sometimes with their windscreens covered. Rick Shay, a pilot for United Airlines, flew NASA鈥檚 Boeing 757 and an SVS-equipped Gulfstream GV jet, and clearly enjoyed the experience. 鈥淚t gives you a great deal of situation awareness,鈥� Shay says. 鈥淚t鈥檚 easy to fly, intuitive and lots of fun.鈥�
SVS is the latest phase of NASA鈥檚 Aviation Safety and Security Program, which aims to slash the number of fatal aircraft accidents. As well as helping to prevent collisions between aircraft, it should reduce 鈥渃ontrolled flight into terrain鈥� accidents 鈥� crashes in which a mechanically sound aircraft is inadvertently flown into the ground. Worldwide, these crashes account for around a third of all aircraft accidents. According to American Airlines pilot Dan Kiggins, who tested the system last year, this is a particular hazard on South American routes, where the terrain is mountainous and radar is sometimes lacking. 鈥淚t鈥檚 grim. Down there you鈥檙e on your own, landing at night with no radar,鈥� he says. 鈥淭he equipment [NASA] are offering is exactly what we need. It would be like putting the lights on.鈥�
Apart from the safety benefits, SVS should also reduce delays by cutting the minimum spacing between aircraft on approach to landing. With SVS, pilots will be able to clearly see an aircraft in front of them, since it will be digitally highlighted and labelled to show whether it is altering course. 鈥淚f it is slowing down you know right away,鈥� says Bailey. If pilots are able to react to these changes more quickly it should help reduce the number of missed approaches, which use up expensive fuel, and help keep flights on schedule.
But, as with any new technology, there might be problems. 鈥淚t may be such a compelling display that the pilots focus all their attention on it,鈥� says Chris Wickens, a psychologist at the University Of Illinois at Urbana-Champaign Institute of Aviation. 鈥淭hey may fail to focus on the reality that is out the window.鈥� Kiggins agrees. Although he found the system intuitive and straightforward, the display is cluttered, he says. He thinks NASA might need to reduce the amount of information on the screen.
There are other drawbacks. For the system to function safely, nearly every feature of every airport has to be measured and entered into the on-board database, which must also be kept up to date. And if an aircraft isn鈥檛 equipped with ADS-B, it may not show up on the system, but since ADS-B is expensive to install, only a few aircraft already use it.
Despite this, NASA engineers hope that aircraft such as business jets will be using SVS by 2007. And there may be additional uses for NASA鈥檚 technology.
Military vehicles already use infrared imaging, and car manufacturers have experimented with the technology. In April General Motors unveiled the Cadillac STS SAE 100, a testbed that will use GPS and satellite images to provide a bird鈥檚-eye view of a driver鈥檚 surroundings, even nearby lamp posts. Fly-by-wire and electronic instrument panels have successfully made the transition from aircraft to automobile. So how about SVS? 鈥淣ever say never,鈥� says Bailey. 鈥淥nce GPS was too expensive. Now it is in every car.鈥�
