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Computer-Related Incidents with Commercial Aircraft

IB 1456 hard landing, A320, Bilbao airport, Spain, February 2001

7 February 2001

Synopsis

As the A320 aircraft, EC-HKJ, approached the landing on a flight from Barcelona in very gusty wind conditions, the alpha-protection law of the flight control was triggered, through a combination of high alpha (angle of attack; roughly, the angle the wing makes with the impinging stream of air through which it is flying) and a sudden change in impinging wind (gust) along with full, sudden control sidestick movements by the pilots as they attempted to counter the gusts. The crew attempted to go around, but the alpha protection lowered the nose and the aircraft impacted the runway hard. We include here the english version of the Final Report

Subsequent to the accident and the results of the investigation, Airbus changed the triggering conditions of the alpha-prot law in the ELACs (Elevator and Aileron Computers, the main flight control computers for pitch and bank) so that the "rate" term no longer contributed to a change to alpha-prot law. Airbus explanated this action to Aviation Safety Week editor David Evans for an article Software Changes Being Made to Help Prevent Landing Mishaps published in that journal on April 18, 2001. We thank Capt. Don Hudson for this reference.

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