What happened
Two separate incidents involving significant safety risks occurred near the Vihdin VOR radio beacon in 1997.
On 20 August 1997, a potential collision risk was identified involving two aircraft: OH-LYZ (a DC-9-51) and OH-LYO (also a DC-9-51). The investigation focused on the proximity of these aircraft near the VOR station.
On 25 October 1997, a second safety incident occurred involving aircraft OH-LMW (a DC-9-82) and OH-LYS (a DC-9-51). This event took place east of the Vihdin VOR. During the investigation of the October event, radio communications were analyzed, including instances where controllers provided vectors and altitude instructions, such as directing an aircraft to climb to flight level 120 while simultaneously managing other traffic in the vicinity.
The investigation
The investigation examined the operational procedures of the Helsinki-Vantaa Approach Control. Investigators reviewed air traffic controller logs, duty rosters, and training records. The scope included an analysis of the airspace structure, the use of situational information to form a traffic picture, and the timeliness of decision-making. The investigation also reviewed the physical working environment, the availability of tools, and the impact of traffic volume and quality on controller performance. Radio telephony recordings were analyzed to evaluate the accuracy of readbacks and the clarity of instructions provided to crews.