What happened
On February 18, 1997, at approximately 12:15 local time, a runway incursion occurred at Helsinki-Vantaa Airport. A runway friction measurement vehicle was performing routine inspections and had moved from taxiway Romeo onto runway 33. The driver intended to measure the braking performance of taxiway Romeo and proceeded to cross the runway, eventually stopping on the right side of the active runway to calibrate equipment.
Simultaneously, a Piper PA-28R-20 and registration OH-PJX, operated by Finnairin Lentokerho ry, was on final approach for runway 33. As the aircraft descended to an altitude of approximately five meters, the pilot observed the yellow inspection vehicle positioned across the runway, roughly 50 to 100 meters ahead of the aircraft's path. To avoid a collision, the pilot immediately executed a leftward evasive maneuver. The aircraft touched down to the left of the runway centerline and continued banking toward the left edge of the runway, passing the stationary vehicle on its left side without contact.
The investigation
The investigation examined the communications between the aircraft, the vehicle driver, and the Helsinki-Vantaa tower. It was established that the vehicle driver had previously received permission to cross runway 04 and had communicated intentions to continue on runway 15. The investigation also reviewed the air traffic controller's actions regarding the arrival of the aircraft and the monitoring of runway occupancy.
Findings
- The air traffic controller permitted the vehicle to occupy the runway based on a mistaken assumption that there were only three aircraft in the current flight group.
- The controller failed to verify any changes to the flight plan or the specific composition of the arriving aircraft.
- The controller's failure to confirm the number of aircraft in the formation was a primary factor.
- An unusually long interval between the third and fourth aircraft in the flight group contributed to the controller's incorrect mental model of the traffic situation.
- The controller's attention was diverted toward determining the refueling needs of an arriving aircraft at the time of the incursion.