Description

On 9 March 1997, a McDonald Douglas MD 81 being operated by SAS on a scheduled passenger flight from Stockholm Arlanda to Kiruna left the runway during the night landing at destination performed in a strong crosswind with normal visibility. An emergency evacuation was performed in which 155 of the 156 occupants were uninjured and 1 suffered a serious injury. Only minor damage was caused to the aircraft.

Investigation

An Investigation was carried out by the Swedish Board of Accident Investigation. It was found that the aircraft commander was PF for the accident landing. Approaching the destination, a weather report gave W/V as 250° /22-32 knots and the braking coefficients on the runway in use, Runway 21, were given as 0.36, 0.32, 0.32 with 100% sanded ice on the runway. A LLZ/DME approach was flown with the Autopilot engaged during which TWR reported that the visibility had decreased to 4000 metres in snow showers and gave a spot wind of 270° / 32 knots with the landing clearance. The landing was performed with autobrake set to medium but after selecting reverse and believing that the aircraft swerved to the right, the PF de-selected reverse and set Maximum autobrake. The aircraft then began to drift towards the left edge of the runway and, approximately 1,500 meters from the touchdown end, left the runway surface and continued parallel to it in lying snow for approximately 400 metres until it came to a stop. An emergency evacuation of the aircraft was performed in which one elderly passenger received a shoulder injury and had to be carried from the site on a stretcher. All exits were used except the forward right hand one where the crosswind from the right blew the escape slide up vertically, which blocked the exit.

It was found that the asymmetric reverse thrust had been the result of a rigging discrepancy in the mechanical engine control system.

The maximum allowable crosswind component for the prevailing friction coefficient of 0.32 was checked as 22 knots, which for the accident Runway corresponds to an actual wind of 250°/42 knots or 270°/25 knots. The wind recorded at the time of landing was 270° 31-42 knots.

The Investigation concluded that the main factors causing the accident were:

• the gusting winds with gusts exceeding the mean wind speed by more than 10 knots not reported;

• the exceedance of the recommended crosswind speed;

• the aircraft touching down more than 9m left of the runway centerline and

• a runway braking action coefficient which was less than reported.

It was noted that the prescribed reaction time for the RFFS attendance was not attained, but that this had no actual consequences.

Two Safety Recommendations were made to the Swedish Civil Aviation Agency (LFV):

1. To ensure that air traffic control personnel are given more in-depth operational flight instruction and the possibility of joint training with flight crew personnel.
2. To ensure that routines and equipment are developed to enable ATC personnel to report information concerning actual crosswind component upon request.

The Final Report of he Investigation was published on 18 February 1998 and may be seen if full at SKYbrary bookshelf: Report C 1998:03e

Further Reading

• Runway Excursion
• Cross Wind Landings
• Landing on Contaminated Runways
• Runway Surface Friction
• Wind Velocity Reporting