NTSB Releases Preliminary Details on Northwest A330 Airspeed Incident
Additional details: 23 June incident involving airspeed fluctuations, Northwest Airlines Airbus A330 flight, Hong Kong to Tokyo
According to Air Transport Intelligence news, additional details are emerging from a 23 June incident involving airspeed fluctuations on a Northwest Airlines Airbus A330 flight from Hong Kong to Tokyo.
ATI news reports that on 25 June the US National Transportation Safety Board (NTSB) officially declared it was investigating the Northwest incident and the loss of primary speed altitude in cruise during a 21 May flight operated by Brazilian carrier TAM with an A330.
In a preliminary report NTSB says the Northwest flight experienced an airspeed anomaly at 39,000ft roughly 50 miles southwest of Kagoshima, Japan. Reports from the crew indicated normal cruise in visual conditions with radar displaying some convective weather about 25 miles north of the track.
Once the aircraft entered cirrus clouds, moderate precipitation and turbulence the crew observed an autopilot and autothrust switch off and the aircraft switched to alternative law. The aircraft's flight data recorder confirmed the switch offs.
NTSB explains the caution and warning messages were activated, and the crew followed flight manual procedures, and autopilot returned in roughly one minute. "However the event quickly repeated itself, lasting for about two minutes," the board says.
After the second event the crew turned the aircraft 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 alternative law for the right of the flight," the board notes in the preliminary report.
NTSB says the FDR confirmed large airspeed fluctuations, small altitude fluctuations and an overspeed alert. The flight with nine crew members and 208 passengers continued to Tokyo and landed with no damage.
The Japanese Transportation Safety Board delegated the investigation to NTSB and assigned an accredited representative to the case. French investigators have previously said automatic messages transmitted by the aircraft show the Air France A330 that crashed 1 June off the coast of Brazil was experiencing conflicting airspeed information from onboard sensors.
Source: Air Transport Intelligence news