TSB Board concerned that runway overruns may continue if more is not done to understand uncommanded nosewheel steering events on Boeing aircraft
Montreal, Quebec, 5 November 2013 – The Transportation Safety Board of Canada (TSB) today released its investigation report (A10Q0213) into the 30 November 2010 runway excursion of an American Airlines Boeing 737-800 at the Montreal/Pierre Elliott Trudeau International Airport.
The aircraft was on a flight to Montreal, Quebec from Dallas, Texas with 113 people aboard. The aircraft landed normally on the wet runway in a crosswind. As the aircraft was slowing down, it veered, uncommanded by the crew, towards the left side of the runway. The captain, the pilot flying, tried using the rudder and the nosewheel steering tiller to steer the aircraft back to the runway centerline. Although the aircraft heading started to return back towards the runway heading, the aircraft continued to travel towards the left and exited the runway surface. There were no injuries, and damage to the aircraft was minor.
Investigators found that the uncommanded veer to the left of runway centerline was likely due to a jam in the nosewheel steering system. Following the occurrence, investigators did not find any anomalies with the nose-gear wheel system, as the jam likely cleared up. The flight crew did not receive any indication that a problem existed with the nose-gear steering system, nor are there any written procedures to manage a nosewheel steering problem of this kind. The aircraft’s flight data recorder (FDR) does not record parameters from the nosewheel steering system, thus making it difficult to determine when and how problems with nosewheel steering occur.
There have been 11 similar occurrences reported involving various Boeing aircraft types in the past 21 years throughout the world. The cause of these uncommanded nosewheel steering occurrences remains uncertain, despite post-event examinations and other efforts to analyze them. The manufacturer’s safety review process has deemed these occurrences to be an acceptable risk given their remoteness, and the manufacturer has not taken further action to correct them. As their cause is uncertain, and because little is being done to better understand the problem, the Board is concerned that there remains a risk for runway excursions to occur.
Following the accident, American Airlines now discusses this occurrence as part of recurrent training for its flight crews. This training is given to the flight crews to raise awareness of the possibility of a runway excursion due to a nosewheel steering problem after landing.
The TSB is an independent agency that investigates marine, pipeline, railway and aviation transportation occurrences. Its sole aim is the advancement of transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.
For more information, contact:
Transportation Safety Board of Canada
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