What happened
On January 31, 2000, at approximately 14:40 local time, a Finnair ATR 72-201, registration OH-KRK, was taxiing to stand 18 at Helsinki-Vantaa Airport after arriving from Jyväskylä. The crew had received ATIS information indicating that braking action on the taxiways and aprons was poor due to icy and slippery conditions.
As the aircraft approached the stand, the captain attempted a 90-degree right turn. During this maneuver, the pilot feathered the left propeller. The aircraft failed to turn as intended, with the nose wheel sliding straight, causing the aircraft to oscillate laterally. The captain applied the brakes and stopped the aircraft approximately 50 meters from the passenger bridge. To regain motion and assist the turn, the captain unfeathered the left propeller.
As the aircraft continued toward the stand, the pilot attempted to slow down using the brakes while approaching a stop marker. However, the aircraft failed to decelerate. Despite applying maximum braking and utilizing the parking brake, the aircraft continued moving forward. The left propeller subsequently struck the corner of the passenger bridge, shattering the bridge's window and damaging its wall structure. The impact caused the propeller blades to break and resulted in minor injuries to a gate agent and a cleaning staff member on the bridge due to flying glass fragments. There were no fatalities among the 51 passengers and 4 crew members on board.
The investigation
The investigation examined the aircraft's flight data recorder (FDR) and cockpit voice recorder (CVR) to reconstruct the taxi sequence. Technical inspections of the aircraft revealed that the left propeller's composite blades were destroyed upon impact and the propeller hub was damaged. The investigation also reviewed the airport's surface conditions, noting that the apron was partially icy and slippery, particularly in the tracks used by the aircraft's landing gear. Additionally, the investigators reviewed the airline's operating manual, which recommended using both engines and limiting nose wheel steering deflections when taxiing in very low friction conditions.
Findings
- The primary cause of the collision was the unintentional application of excessive engine power, which had been left at a high setting following the attempt to restart motion after the initial slide.
- The slippery and icy condition of the apron acted as a contributing factor, making the aircraft difficult to control.
- The pilot's decision to unfeather the left propeller to assist the turn resulted in a power setting significantly higher than what was required for taxiing, which was inadvertently maintained until the collision.
- The airline's procedures for taxiing in adverse weather were found to be insufficiently detailed for such low-friction environments.