Do Computers Make Planes Less or More Safe?

A Flight Safety Debate Looms

What happened in that stormy night over the Atlantic? Were the pilots overwhelmed by crashing computer systems? Did the jumbled error messages cause them to make a fatal mistake? "Whatever the eventual findings, the crash already is prompting questions about how thoroughly aviators are trained to cope with widespread computer glitches midflight," writes the Wall Street Journal.

The British trade publication Flight International also anticipates a new debate over air safety and cites, in particular, the February crash of a Turkish Airlines Boeing in Amsterdam. During the landing approach, a malfunctioning altitude indicator reported that the plane was already two meters below the runway. The computer that controls the automatic thrust control system, believing that the aircraft was already on the ground, reduced engine power. The pilots ignored the change, perhaps because they had placed too much trust in the computer.

The Boeing 737 eventually crashed into a field near the runway, killing nine on board. "The issue of the human factors associated with operating highly automated aircraft is likely to move up the agenda once more," Flight International predicts.

That agenda will probably be influenced by the final report on the near crash of a Lufthansa flight due out this autumn. In March 2008, the wing tip of an Airbus A320 scraped across the runway at Hamburg Airport in strong crosswinds. The dramatic images of the near crash quickly circled the world in the form of an amateur video that was eventually viewed millions of times on the Internet.

The pilots were initially described as heroes for having saved the plane. But then the tabloids sharply criticized the co-pilot for being inexperienced and inept.

"But now the situation turns out to be more complex," says Johann Reuss, the investigator with the German Federal Bureau of Aircraft Accidents Investigation (BFU) who was assigned to the case. He cannot comment further, because the final report has not been released yet.

Part 2: Digital Technology Has Improved Safety, But it Can Still Present a Threat

According to investigation results that have remained classified until now, the A320 apparently behaved in an unexpected way during the high-wind landing. The most likely explanation is that because one of the plane's tires had already briefly touched the ground, the flight computer switched from approach mode to ground mode. But when the computer is in ground mode, it does not permit the pilots to turn the ailerons as sharply as they would have done to handle the extreme crosswinds. The computer intervened by limiting the angle of the ailerons, causing the wing tip to suddenly scrape across the runway.

"This sort of behavior on the part of the aircraft wasn't described in any manual," says one pilot critically -- nor is it described today, because Airbus is remaining tight-lipped about the incident until the investigation is complete.

The landing could easily have ended in a disastrous accident. The computer was in control for almost three seconds. It was only through the determined intervention of the pilot, who pulled the plane back up into the air, that the aircraft, traveling at more than 200 kilometers per hour (124 mph), could be prevented at the last minute from crashing.

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