C3/2006L Incident involving an airliner landing at Helsinki-Vantaa airport on 20 February 2006

An incident occurred at Helsinki-Vantaa airport in Finland at 11:36 on 20 February 2006. At this time, two of the four main landing gear tyres burst as the aircraft flying the scheduled Finnair Oyj flight from Warsaw to Helsinki landed. Accident Investigation Board Finland (AIB) decided to appoint an investigation commission, C 3/2006 L, for this incident. Air Accident Investigator Markus Bergman was named investigator-in-charge accompanied by investigator Tapani Vänttinen as member of the commission.

As the aircraft was approaching Helsinki, the pilots inadvertently applied the emergency/parking brake lever instead of the speed brake lever. Even after the lever was released, one of the two parking brake circuits in the aircraft malfunctioned and retained pressure. The result of this was that the outermost tyres on the main landing gear burst during the landing roll. Apart from the damaged tyres, the incident did not result in damage to the aircraft or injuries to people.

The investigation revealed shortcomings in the aircraft’s emergency/parking brake system, the indication and warning system as well as with airline regulations and pilot action.

The direct causal factor of the incident was a malfunction in the emergency/parking brake system. Contributing factors include the pilots’ error as they applied the speed brakes, the fact that the aircraft’s indication and warning system did not provide clear enough information to the pilots about the malfunction and the fact that the pilots forgot that the emergency/parking brake telltale lamp was on. The emergency/parking brake system had functioned abnormally twice before but this had been reported in the aircraft’s technical log book by using a technical remark rather than a malfunction report, which was also a contributing factor to the incident as a remark did not require the technical personnel to initiate immediate fault isolation activities.

The investigation commission issued three recommendations. A recommendation was given to the aircraft manufacturer for them to redesign the emergency/parking brake system so that it be impossible for the emergency/parking brake to retain pressure when the brake lever is disengaged in the air and/or to publish a procedure according to which pilots are able to depressurise the emergency/parking brake system aloft without compromising flight safety. A second recommendation for the aircraft manufacturer was that they also redesign the emergency/parking brake warning and indication system so as to provide sufficiently detailed information to pilots of system status and possible faults when airborne. The third recommendation was given to the airline. It was for them to issue unambiguous instructions on how to report aircraft malfunctions and how to enter technical remarks.

C3/2006L Report (pdf, 0.77 Mt)