Airspeed systems on U.S. airliners failed

The airspeed indicator systems on a number of United States airliners have failed in recent weeks, keeping pilots from knowing how fast they were flying, a very dangerous situation.

The problems specifically involve the Airbus A330 aircraft operated by Northwest Airlines, a major U.S. carrier. There is even a growing suspicion that this problem may have been central to the crash of a Northwest A330 that went down in the Atlantic ocean a few weeks ago, killing all 228 people aboard.  Each of the airspeed issues was reported by the pilots of the affected planes, yet no one paid much attention to the reports until the crash of the Rio to Paris flight.

Speed is one of the critical pieces of information that a pilot must know in order to do his or her job safely. Fly too slowly, and you are in danger of losing control in a stall. Fly too fast, and you are in danger of subjecting the airframe to forces that it cannot safely handle. It is the former condition that is more dangerous in most conditions, and can cause an aircraft to enter a spin from which it cannot recover before it loses all altitude and crashes.

The systems in question make use of an old invention called a Pitot tube. The Pitot tube was invented by French engineer Henri Pitot in the early 1700s and was modified to its modern form in the mid 1800s by French scientist Henry Darcy. It is widely used to determine the airspeed of an aircraft, using difference in air pressure. In modern aircraft, the data from the pitot tube is fed to an airplane’s computer system, from which it is relayed to the pilot.

There have been at least a dozens instances of airspeed system failures recently, according to an AP story on the situation. All have involved the same type of Airbus airplane operated by Northwest. The system have been known to fail in a variety of flight situations and in locations as diverse as Japan and Brazil. Other airlines operating the same aircraft have not experienced these problems, leading to speculation that Northwest maintenance practices are a contributing factor. The FAA continues to investigate.

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