That’s serious – pitot tubes as speed sensors – isn’t it too old?

Airbus A330 has history of airspeed problems | Markets | Markets News | Reuters

Airbus A330 has history of airspeed problems

PARIS, June 6 (Reuters) – Airbus (EAD.PA) has faced problems
with the speed sensors on its A330 aircraft dating back to at
least 2001, forcing changes in equipment as well as the pilot’s
flight manual, according to regulatory documents.

An automated error message from the flightdeck pointing to
discrepancies in airspeed data is among a handful of clues
available so far to experts investigating last week’s crash of
an Air France A330 in an Atlantic storm that killed 228 people.

France’s chief crash investigator said on Saturday airspeed
problems had arisen on the same type of plane before but
stressed it was too soon to say if these were to blame for the
crash and added the plane was still safe to fly. [nL621070]

Airbus confirmed on Saturday it had recommended before the
crash that airlines change speed sensors called pitot probes.
But it said it was an optional move based only on performance
rather than concerns about safety, which would be mandatory.

Operators have however been warned in the past of unsafe
conditions resulting from potential ice damage to the sensitive
probes fixed to the fuselage, according to online filings.

In 2001, France reported several cases of sudden fluctuation
of A330 or A340 airspeed data during severe icing conditions,
according to the U.S. Federal Aviation Administration.

“Lost or erroneous airspeed indications could result in lack
of sufficient information for the flight crew to safely operate
the airplane, and consequent inadvertant excursions outside the
normal flight envelope,” the FAA wrote in a 2001 summary.

Airbus was ordered as a result to update the cockpit manual.
On Thursday, following the crash, Airbus issued a reminder to
pilots on procedures in the event of speed discrepancies.

The plane which crashed was an A330-200, the newer of two
variants of the A330 wide-body twinjet. It was built in 2005.

In 2002, operators of the A330-300 sister model had been
ordered to upgrade speed sensors, again because of problems in
extreme weather, according to a directive issued in Australia.

The pitot probes, angular tubes sticking out from the side
of the aircraft, measure speed based on pressure but their
measurements can be halted or skewed if they become blocked.

Two companies manufacture sensors suitable for the A330,
France’s Thales (TCFP.PA) and U.S.-based Goodrich (GR.N).

A spokeswoman for Thales, which supplied the sensors on the
crashed aircraft, said on Friday it was premature to speculation
whether they were linked to the crash pending the investigation.

France’s weather office said on Saturday the equatorial
storm in the plane’s path was severe but “not exceptional”.
(Reporting by Tim Hepher; Editing by Matthew Jones)

Last year I was teaching Advanced Measurements in Mechanical Engineering. One of the subject was of course, pitot tubes, and their applications. I cited few places from the web that pitot tubes that were blocked/malfunctioned, caused serious problems, including plane crashes. I really hope it is not the case with the Airbus, but who knows. I suggest to replace it with surface-mounted MEMS devices – at least it can be easily multiplicated and should not be affected by the weather. Of course, it should be reliable and work in any conditions (ice, dust, clouds, etc), though I’m not sure about pitot tubes either working well under such conditions. I’m sure that GPS is good enough, and wonder why it’s not implemented. Gyros are also good, after all, missiles do not use pitot tubes to measure their velocity.


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