It is generally undisputed that digital technology on board has helped improve aviation safety. In the vast majority of cases, it helps prevent dangerous situations in the air before they become a problem.
But all of these incidents effectively show how digital equipment can also become a threat. The mysterious breakdowns have triggered a debate in aviation that both airlines and manufacturers would prefer to avoid. How much more high-tech equipment should engineers insert into the cockpit? Does more digital technology automatically result in improved safety? And how much power should flight computers be allowed to have before pilots become disastrously impotent?
Computers have a Janus-faced nature. On the one hand, they help prevent crashes, which is why no one questions their right to exist. Some experts would even like to see more computers in the cockpit. British aviation expert David Learmount, for example, believes that computers could replace one of the pilots in the cockpit one day. "Why do you need two if the computer system is the captain's copilot?" Learmount asks provocatively.
On the other hand, the computers themselves can turn into a safety problem. When the Australian accident investigators took a closer look at the details of the Qantas Flight 72 incident, they discovered that it was by no means an isolated case. Last December, just two months after the drama off the Australian coast, a similar problem occurred on board another Qantas A330. Airbus competitor Boeing is not immune to unexpected computer glitches, either. In 2005, a flight computer caused a Boeing 777 to climb 700 meters for no apparent reason. It happened twice during the flight and caused the jetliner to lose more than a third of its speed, so that it almost stalled.
"Incidents of this nature are a harbinger of what is to come," says Thomas Haueter, the director of aviation safety at the powerful US National Transportation Safety Board (NTSB), which investigates air accidents. He is alluding to the kinds of breakdowns in on-board computers that are difficult to predict. "Lots of people are very concerned that previously unknown problems could arise from the overabundance of computers and software." Haueter wants to make sure that pilots can never lose complete control over their aircraft.
There are about 2,000 computers operating in a modern Airbus A320 short-haul jetliner. They control the air-conditioning system, monitor the engines and check the toilets, but they also help fly the plane.
The days are long gone when a pilot fully understood his aircraft. "We have to make a huge effort so that we don't experience a decline in aviation safety," says Haueter. The manufacturers are well aware of the problems. "They know that automation is the way of the future, but they also know that computers have to be tested more effectively than they have been until now."
The authors of a report released by the US National Academy of Sciences (NAS) describe "several aircraft accidents" in which pilots confused various computer settings. "The software behaved the way it had been programmed to behave, but not the way the pilots expected." The US Federal Aviation Authority (FAA) agrees that the growing computerization of aircraft makes "validation and verification of software more challenging." Programs have become so complex that they can hardly be tested for all eventualities anymore.