C7/2006L Veering Off the Runway at Seinäjoki Airport on 11 December, 2006

An incident occurred at Seinäjoki airport on 11 December 2006 at 20:56 (all times in this report are Finnish time) when an ATR-42 airliner momentarily veered off the side of the runway during its landing roll. There were 27 passengers and 3 crew members onboard. Accident Investigation Board Finland appointed an investigation commission for this occurrence. Investigator Jouko Koskimies was named investigator-in-charge, accompanied by air accident investigator Hannu Melaranta as member of the commission. MSc Markku Roschier and Dr. Päivikki Eskelinen-Rönkä, a phonic expert, were invited to participate in the work of the commission.

At 20:50 on 11 December a Finnish Commuter Airlines’ ATR-42, on its scheduled route from Helsinki to Kokkola with a stopover at Seinäjoki, was approaching Seinäjoki runway 32 in gusty crosswinds at dark. According to ATIS information wind was 180 degrees 12 knots, maximum 22 knots. When the aircraft called Outer Marker (PSJ) inbound the AFIS officer reported the previous two minutes’ average wind: 190 degrees 10 knots, maximum 16. Because this wind information did not exceed the limitations of the flight manual the captain decided to land on runway 32. Halfway through the landing roll the aircraft suddenly and strongly veered to the left. Despite the flight crew’s best efforts at approximately 700 m from threshold the aircraft veered off the 30 m wide runway. The left main landing gear travelled approximately 115 m at ca. 2 m from the edge of the paved surface on the 2.5 m wide sand/gravel runway shoulder, leaving a few centimetres-deep rut in the gravel. The landing gear hit and destroyed two runway edge lights and its anti skid wiring was cut. The captain managed to steer the aircraft back onto the runway, whereafter he taxied to the apron. After the damage to the aircraft was inspected the following leg of the flight was cancelled.

At 22:44 the Seinäjoki AFIS officer reported the occurrence to Area Control Centre (ACC) South Finland, which in turn alerted Accident Investigation Board (AIB) Finland at 22:47. At 23:00 AIB Finland contacted Seinäjoki State local district police and requested that they visit and investigate the scene. Both pilots were breathalysed and their results indicated zero blood alcohol.

The investigation established that the aircraft had no such defect that could have caused the occurrence. At the time of the incident the weather was cloudy and humid. Winds were southerly and gusty. The runway was wet, albeit with good braking action.

A chain of events with several interrelated factors caused the aircraft to veer off the runway. These factors included:

• The decision to make a downwind landing,
• A strong gust of wind from the left, approximately halfway through the landing roll, which caused the aircraft to unexpectedly bear to the left,
• The wetness of the runway, which allowed the aircraft to skid sideways,
• The runway was not wide enough for the flight crew to steer the aircraft back toward the runway centreline,
• The pilot attempted to straighten out the aircraft by using the rudder. However, as speed decreased the rudder effect alone was insufficient,
• The captain did not hear the co-pilot call ”70” and, hence, engaged the nose wheel steering too late, and
• The captain’s limited experience as pilot-in-command of an ATR.

The investigation commission issued one recommendation to EASA.

C7/2006L Report (pdf, 0.29 Mt)