Airspeed systems failed on US jets

Sully

Malfunctioning equipment on at least a dozen recent flights by US passenger jets made it impossible for pilots to know how fast they were flying, investigators have discovered.

A similar breakdown is believed to have played a role in the Air France crash into the Atlantic in June that killed all 228 people aboard, including three Irish citizens.

The discovery suggests the equipment problems are more widespread than previously believed and gives new urgency to airlines already scrambling to replace air sensors and find out how the errors went undetected despite safety systems.

The equipment failures, all involving Northwest Airlines Airbus A330s, were brief and noticed only after safety officials began investigating the Air France crash – on a Rio de Janeiro to Paris flight – and two other recent in-flight malfunctions.

The failures were described by people familiar with the investigation.

A car’s speedometer uses tyre rotation to calculate speed, but a plane relies on sensors known as Pitot tubes to measure changing air pressure. Computers interpret that information as speed.

While a car with a broken speedometer might be little more than an inconvenience, many plane control systems rely on accurate speed information to work properly.

Like the fatal Air France flight, the newly-discovered Northwest incidents and the two other malfunctions under investigation involved planes with sensors made by the European electronics giant Thales Corporation.

The Air France crash called into question the reliability of the sensors and sparked a rush to replace them.

Many companies, however, simply replaced them with another Thales model. As it became clear the problem was more widespread, Airbus and European regulators told companies to replace at least two of the three sensors on each plane with models made by North Carolina-based Goodrich.

The planes are allowed to continue flying while the switch is made.

Thales officials declined to comment. The company has previously said its sensors were made to Airbus specifications.

The Northwest incidents were discovered when Delta Air Lines, which merged with Northwest last year, reviewed archived flight data for its fleet of 32 Airbus A330s, the people close to the inquiry said.

All of the incidents took place in the Intertropical Convergence Zone, which extends from 5 degrees north of the equator to 5 degrees south, and all the planes involved landed safely, they said.

Aviation experts said the discovery could provide clues to what caused Air France Flight 447 to crash into the Atlantic en route from Brazil to France on June 1, and what might be done to prevent future tragedies.

French investigators have focused on the possibility that Flight 447’s sensors iced over and sent false speed information to the computers as the plane ran into a thunderstorm at about 35,000 feet.

An important part of the investigation focuses on 24 automatic messages the plane sent during its final minutes. They show the autopilot was not working, but it is unclear whether the pilots shut it off or whether it shut down because of the conflicting airspeed readings.

Three weeks after the Air France crash, the US National Transportation Safety Board said it was investigating two other A330 flights that experienced a loss of airspeed data.

The most recent was on June 23, when a Northwest flight hit rain and turbulence while on autopilot outside of Kagoshima, Japan.

According to an NTSB report, speed data began to fluctuate. The plane alerted pilots it was going too fast and autopilot and other systems began shutting down, putting nearly all the plane’s control in the hands of the pilot, something that usually happens only in emergencies.

In May, a plane belonging to Brazilian company TAM Airlines lost airspeed and altitude data while flying from Miami to Sao Paulo, Brazil. Autopilot and automatic power also shut down and the pilot took over, according to an NTSB report. The computer systems came back about five minutes later.

“These two cases we know were dealt with effectively by the crew, and we think this happened in Air France and maybe wasn’t dealt with effectively,” said Bill Voss, president of the Virginia-based Flight Safety Foundation, an aviation safety think-tank.

Morgan Durrant, a spokesman for the only other US airline that operates A330s, US Airways, said it had not seen similar problems in its 11-plane fleet of the jetliners.

Delta/Northwest and US Airways recently completed replacing older Thales tubes with new Thales tubes. The companies say they are now replacing them with Goodrich tubes.

Read more: http://breakingnews.ie/world/airspeed-systems-failed-on-us-jets-421727.html#ixzz0NbCRqSUm

This was probably the worst year for Aviation, lots of incidents with planes. Seems that the Airspeed systems are a big enough issue but oddly not worrying the plane manufacturers!

Fratton Fred

does the "Stick Shaker" work off these pitot tubes as well?

diverdriver

No, it's activated by angle of attack sensors. An aerofoil stall will when it reaches it's critical angle of attack. The speed is irrelevant.

FlutterinBantam

That little "hockey stick" usually around the pitot tubes is your friend.


Don't kick it.:cool: