GRAHAM WARWICK / WASHINGTON DC
Over most of the first 100 years of aviation, cockpits became more complex. That trend is being reversed as commercial IT finds its way on to the flightdeck
When the Wright brothers made their historic first flight, their 1903 Flyer did not have much in the way of instrumentation: a counter to record engine revolutions, an anemometer to measure air speed, and a stopwatch to measure flight time.
As aviation advanced it became more complex, and the quantity of information handled by the pilot increased.
More and more gauges were added to the instrument panel until the cockpits of multi-engined transports of the 1950s and 1960s looked like watchmakers' workshops. The first generation of electronic flight instrument systems transferred information from dials to screens and added more in the form of the engine indication and crew alerting system with its synoptic displays of subsystem status.
Simplified workload
Only within the past 10-15 years have designers made significant progress in simplifying the cockpit and reducing pilot workload. The watchword today is human-centred cockpit design, terminology that acknowledges the human-factors shortcomings of earlier generations of electronic flightdeck. It also accepts that the information load on crews is still increasing and needs to be managed more efficiently.
The application of commercial information technology to the cockpit has been key to developments over the past few years. Crews of the latest aircraft look at information presented on large-format liquid-crystal displays developed from those used in laptop computers; the displays communicate with avionics boxes via the Ethernet databus used in office networks; and the avionics themselves use the same PowerPC or similar microprocessors that are the heart of personal computers.
For decades, aviation was a driver of electronics technology. Now it is a user, benefiting from rapid advances in commercial electronics, while facing the challenge of keeping pace with an industry that has far shorter development cycle times and product lifetimes. The change began with development of the microprocessor in the early 1970s, but the cockpit has evolved more slowly than the office for several reasons.
First of these is the environmental challenge of operating over a wide range of temperatures, pressures and g loadings - something that need not worry the designer of a desktop computer. Second are the regulatory requirements for validation and certification of safety-critical avionic systems. Combined, these result in a product development cycle for aircraft that is far slower than for commercial electronics.
Only with its latest generation of aircraft is the industry approaching the goal of being able to keep pace with technological and operational changes by evolving and upgrading software and hardware independently. Open systems standards are coming to the cockpit. With enough display flexibility, network capacity and processing capability, modern aircraft should be able to keep pace with change without the need for frequent avionics retrofits and cockpit upgrades.
Although aircraft have changed relatively little externally in the past 20-30 years, computing technology has had a huge impact internally. Among the most significant developments has been fly-by-wire. Placing a computer in the loop between pilot input and aircraft response has had a profound effect on performance and safety. Although analogue systems began to emerge in the 1960s, and the first fly-by-wire fighters entered service in the late 1970s and early 1980s, development of digital flight control systems has been the key.
The Airbus A320 introduced airlines to digital fly-by-wire in the late 1980s, followed in the mid-1990s by the Boeing 777. The latest generation of regional jets, led by the Embraer 170/190, have digital flight controls, and Dassault is developing the first fly-by-wire business jet, the Falcon 7X.
Europe's NH90 military helicopter and the military Bell Boeing V-22 and civil Bell Agusta Aerospace BA609 tiltrotors have digital flight controls, while Sikorsky's S-92 is going fly-by-wire and Eurocopter is demonstrating fly-by-light.
Fly-by-wire advantages include lower weight, with electrical signalling replacing mechanical control runs. Digital flight controls can disguise an aircraft's undesirable flight characteristics and limit a pilot's ability to exceed the safe flight envelope. Aircraft stability can be relaxed to increase manoeuvrability or reduce drag.
Control laws can be developed that optimise the aircraft's handling for each phase of flight. Software can autonomously detect disabled or damaged flight control surfaces and automatically reconfigure the good controls to preserve safe handling.
Optically signalled fly-by-light is one avenue of future flight control system development, particularly for aircraft vulnerable to electromagnetic interference, such as low-flying helicopters operating close to power lines.
Power-by-wire is another, coupling fly-by-wire control with electric actuation. The Airbus A380 will have one power-by-wire control channel, while Boeing has selected a "dual/dual" hydraulic/electric flight-control architecture for the 7E7. Another route is closer integration of flight controls with other systems.
In military aircraft, flight control systems are becoming vehicle management systems, integrating propulsion control and the operation of secondary systems such as landing gear. This makes sense in fighters like the stealthy Lockheed Martin/Boeing F/A-22, where thrust vectoring is integral to flight control; or the short take-off and vertical landing Lockheed Martin F-35 Joint Strike Fighter, where propulsion and flight control are tightly coupled. The F-35 is also the first power-by-wire fighter.
Essential integration
Highly integrated systems are essential for unmanned air vehicles, where space, weight and power are at a premium. Unmanned combat air vehicles are also among the first aircraft to go fully power-by-wire, to eliminate the weight and complexity of hydraulic and pneumatic systems. Safety-critical controls and mission-critical systems have been kept separate, but development of partitioned operating systems able to run flight control software alongside less-critical applications promises greater integration.
Fly-by-wire has made flying simpler and safer. Handling can be made more uniform and predictable, and envelope protection can be provided. Sophisticated autoflight modes can be provided that go beyond a simple autopilot and autothrottle. In the wake of 11 September, research has begun into ways of preventing aircraft flying into obstacles, intentionally or accidentally.
Arguably, the biggest revolution in cockpit technology was the introduction of electronic flight displays in the 1970s. Early monochrome cathode ray tubes (CRT) quickly evolved into colour displays, but while aviation was getting to grips with electronic displays in the 1980s and 1990s, the electronics industry was abandoning bulky CRTs in favour of flat-panel LCDs.
LCDs consume less power, generate less heat, require less space and have much improved graphics capability. But their use in cockpits meant disadvantages had to be overcome in adapting commercial displays to be readable in bright sunlight and viewed from across the cockpit. And displays have to be available over an aircraft life measured in decades, compared with years - sometimes months - for a desktop.
The latest displays beginning to appear in business jet cockpits - Gulfstream's PlaneView flightdeck for the G500 and G550 and Dassault's EASy cockpit for the Falcon 2000EX and 900EX - are based on the same large-format active-matrix LCDs used in laptops. But new display technologies are on the horizon that could provoke another disruptive change in commercial electronics. Foremost among these is the organic light-emitting diode (OLED) display. The self-illuminating OLED, still in its infancy, is brighter and sharper than the LCD, 20-50% cheaper to produce and paper thin. Another cockpit display gaining ground is the projection LCD. Lockheed Martin has selected projection technology to turn almost the entire instrument panel of the F-35 into a flexible display surface. The advantage of projection displays is that the same micro-LCD optical engine can be used with different optics for displays ranging from 125mm-square to 820mm-diagonal. As LCD technology advances, the optical engine can be updated without changing the display. LCDs are now appearing in head-up displays (HUD) and helmet-mounted displays (HMD), replacing CRTs.
Bringing large-format LCDs into the cockpit transforms the management of information. The latest flightdecks feature cursor-controlled menu windows, on-screen radio tuning and systems control, electronic charts and graphical weather, and video display capabilities.
HUDs are becoming more common in business jets, driven by the availability of enhanced vision systems (EVS), which provide improved situational awareness in low visibility. Initial EVSs use an infrared (IR) sensor, but systems are under development that will fuse imagery from multiple IR, low-light television and millimetre-wave radar sensors. The next step is the synthetic vision system (SVS), which computer-generates a picture of the outside world from an onboard terrain and obstacle database.
The ultimate goal is a fused EVS and SVS that will allow the pilot to fly visually in any visibility condition. Combined with high-resolution, full-colour HMDs, this technology forms the core of the "virtual cockpit" concept, where the flightdeck is no longer physically constrained by the aircraft. This promises the ultimate in flexibility to adapt and update via software the way in which information is presented to the pilot, who need no longer be in the nose - or even in the aircraft. But the new emphasis on human-centred cockpit design will be essential if this technology is to be successfully introduced on to future flightdecks.
Source: Flight International
