US requires sensor changes on some Airbus planes

* Goodrich to supply new parts

* Order affects A330, A340 planes

* FAA directive takes effect Sept. 8

WASHINGTON, Sept 2 (Reuters) - U.S. airlines must replace speed sensors on some of their Airbus EAD.PA planes, parts that have come under scrutiny since the crash of an Air France AIRF.PA jetliner three months ago.

The Federal Aviation Administration (FAA) on Wednesday ordered carriers operating A330 and A340 jetliners -- Delta Air Lines DAL.N and US Airways LCC.N -- to swap probes manufactured by Thales SA TCFP.PA with components made by Goodrich Corp GR.N.

The FAA order, which takes effect Sept. 8, affects about 40 planes, and follows similar action by European authorities in response to the crash of Flight 447 that killed 228 people. The A330 plunged into the Atlantic Ocean on a flight from Rio de Janeiro to Paris on June 1.

Investigators said they do not yet know what caused the crash but are interested in what role, if any, unreliable speed readings from the plane may have played in events leading up to the disaster.

The investigation is expected to take another year.

European safety officials have reported speed indicator discrepancies on some A330 and A340 planes at high altitudes in bad weather. Investigators indicate that planes equipped with Thales probes appear more susceptible in rough conditions.

Regulators are especially concerned about ice crystals forming on sensors and throwing off readings. Inaccurate readings can disengage the autopilot or other automatic functions and cause the pilots to lose control of the aircraft.

There have been several reports of problems with Thales sensors.

Airbus in July urged airlines to switch to Goodrich, which already supplies sensors on most of the world’s A330/A340 fleet. About 200 planes are equipped with sensors made by Thales, Airbus has said.

Separately, U.S. transportation investigators are looking into possible anomalies with speed and altitude indicators on two A330 planes in May and June.

Privately held Thales is best known as Europe’s largest defense electronics company, which has so far declined to comment on the sensor matter. (Reporting by John Crawley and Tim Hepher; Editing Bernard Orr)