You may get some answers from this very recent incident...
NTSB: Airbus A330 Experienced An 'Airspeed Anomaly' Northwest Flight Crew In Japan Noted Airspeed Fluctuations
The NTSB has released a preliminary
finding in an incident involving a Northwest Airlines Airbus A330
on a flight in Japan last month in which the onboard computers
switched off the aircraft's autopilot possibly due in part to
inconsistent airspeed indications.
The report reads:
NORTHWEST AIRLINES INC
Incident occurred Tuesday, June 23, 2009 in Kagoshima, Japan
Aircraft: AIRBUS A330-323, registration: N805NW
Injuries: 217 Uninjured.
This is preliminary information, subject to change, and may
contain errors. Any errors in this report will be corrected when
the final report has been completed.
On June 23, 2009, at 0303 UTC, an Airbus
330-323, U.S. registration N805NW, operated by Northwest Airlines
as flight 8 from Hong Kong, China, to Tokyo, Japan, experienced an
airspeed anomaly while in cruise flight at FL390 approximately 50
miles southwest of Kagoshima, Japan. The crew reported that they
were in normal cruise at FL390 and in visual conditions with some
convective weather displayed on radar about 25 miles north of
track, with thin cirrus clouds ahead.
After entering the cirrus and moderate precipitation and
turbulence, the crew observed, and FDR confirms, the autopilot and
autothrust switch off, and the aircraft switched to Alternate Law.
The master caution and warning messages were activated. The crew
followed flight manual procedures and the autopilot and normal law
returned in about one minute, however the event quickly repeated
itself, lasting for about 2 minutes. The crew turned the airplane
60 degrees off course to exit the weather as soon as the anomalous
indications were observed. The autopilot, autothrust and other
controls returned to functioning, but the airplane remained in
alternate law for the rest of the flight.
The crew observed, and FDR confirms, large airspeed
fluctuations, small altitude fluctuations, and an overspeed alert.
The flight continued to Tokyo, Narita airport and landed with no
damage or injuries to the 9 crew and 208 passengers on board.
The incident occurred in Japanese airspace, and the
investigation was delegated to NTSB by the Japanese Transportation
Safety Board, who assigned an Accredited Representative to the
investigation.
FMI:
National Transportation Safety Board