On Thursday February 9th 2006 at 08:37 Finnish time an incident occurred at Oulu airport in which the runway safety margins became smaller than allowed about 660 meters from the threshold of runway 30 at the arrestor cable. A general aviation category airplane OH-KJJ (TB 20), departing from Oulu to Helsinki, passed at an altitude of 150 to 400 feet over a tractor on the runway.

The tractor in use by Air Force was cleaning the arrestor cable apparatus when Air Traffic Control gave a clearance for take off for the aircraft taking off from runway 12. The driver of the tractor was at this time outside the tractor cleaning the arrestor cable area at the runway periphery. The Air Traffic Controller noticed the occurrence immediately when the aircraft was in the air by the tractor.

The safety margin applicable at the runway was not followed, but the performance of the light aircraft was so good that no clear situation of danger arose.

The cause of the incident was the controller’s mistake. He forgot to secure that the runway was clear of obstacles over its entire length when he gave a clearance for take off for the departing aircraft. Contributing factors were substantial traffic of land vehicles and on the radio due to the morning snow fall and the fact that the controller’s work shift was the first operative work shift after a long training period.

The accident investigation commission presents following safety recommendations:

1. Such portable VHF radiotelephones should be acquired for all land vehicles of Oulu airport and Air Force so that the drivers have a true possibility to follow the air communication radio traffic when working outside the machines.
2. Alternatively a possibility should be investigated to use in all communication traffic, also in road vehicles, the same VHF Air Traffic Control frequency when working on the runway areas, whereby all participants would have a continuous and clear idea about the other traffic.
3. A beacon light of strobe light type should be mounted on all vehicles moving on the airport traffic area to improve the vehicle discernment.
4. Oulu Air Traffic Control should take in use a mode of operation, in which the Air Traffic Controller is not alone allowed to take control responsibility during the first working day after a long absence.

Download here the investigation report, pdf-file in Finnish, 1,8 MB