Wednesday June 10, 2009
FACTBOX - Attention centres on Air France speed sensors
REUTERS - Attention is focusing on the possibility that faulty speed sensors, or pitot tubes, were a factor in causing an Air France Airbus A330 to crash into the Atlantic Ocean last week.
The crash of flight 447 from Rio de Janeiro to Paris, with 228 people on board, was the world's deadliest air disaster since 2001 and the worst in Air France's 75-year history.
 |
A combination photo shows the Brazilian Navy picking debris from Air France flight AF447 out of the Atlantic Ocean, some 745 miles (1,200 km) northeast of Recife, in these handout photos distributed by the Navy in Recife, northeastern Brazil June 9, 2009. (REUTERS/Brazilian Air Force/Handout) |
Here are details and background on the pitot tube:
CONTRIBUTING FACTOR?
There is speculation that the airplane's pitot tubes -- probes on the exterior of the fuselage -- may have iced up, giving false speed readings and confusing the plane's computer and pilots as they navigated equatorial thunderstorms.
Pitot tubes on aircraft are typically heated to prevent them becoming clogged with ice. Investigators are considering iced tubes as a possibility, but the head of France's air accident agency has said it is too soon to say if problems with the speed sensors were in any way responsible for the crash.
A French pilots' union, Alter, said on Tuesday that "there is a real risk of losing control of an Airbus" in the event of a pitot tube malfunction, though it added that it was drawing no conclusions on the cause of flight 447's crash.
Another pilots' union, SNLP, said frozen pitot tubes could not be the sole reason for the disaster.
Widely used to gauge the speed of aircraft, pitot tubes are also used to measure wind and gas speed for industrial purposes.
Air France has said all its flights using long-haul Airbus jets will be equipped immediately with new speed sensors, a pilot's union said on Tuesday.
CAUSE OF PREVIOUS CRASHES?
Blocked speed sensors have been blamed for contributing to airplane crashes in the past.
In 1996, a report into the crash of a Boeing 757 airliner off the Dominican Republic blamed a faulty reading by the pitot tube -- which was blocked by dirt or insect remains -- for the disaster, alongside pilot error.
HENRI PITOT, INVENTOR
The devices were invented some three centuries ago and still play a key role in 21st century high-tech avionics.
Invented in 1732 by French engineer Henri Pitot, they were used to measure the flowing speed of rivers and canals.
The device consists of a tube with two holes, bent at a right angle. The first hole is placed in the moving air (or in Pitot's days, water), with the mouth of the bent section aimed upstream to measure its velocity.
The side hole measures static air pressure, and the difference between the two is used to calculate airspeed.
Pitot tubes can be mounted on a plane in several different ways -- including from the edge of the wing, or on the exterior of the fuselage. The A330 Airbus has three pitot tubes.
Modern makers of pitot tubes include Thales, which made the devices used on Flight 447, and Goodrich Corp of the United States. Thales was not available for comment.
Copyright © 2008 Reuters
News Poll
- Road bully leaves couple badly hurt
- Penang’s great food paradox
- Theft of jet engine an inside job, says minister
- No reason for me to resign, says Chew
- Jusco blast claims second life
- Convert still not a Malaysian
- Ku Li: I will explain oil royalty issue
- Work starts on LRT station
- Bung Moktar finally admits marrying Zizie
- Karpal vows to fight for Anwar
- Penang’s great food paradox
- Theft of jet engine an inside job, says minister
- We must fix our weaknesses
- 18,000 join search for best food
- Road bully leaves couple badly hurt
- Govt will not withdraw sugar subsidy
- Work starts on LRT station
- RM20bil FDI target will be met this year, says Mukhriz
- Prepare for an emergency
- Eight women among 44 foreigners held in raid
RSS
