C5/​2008L An air prox­im­ity in­ci­dent in Oulu Ter­mi­nal Area on 9 Sep­tem­ber 2008

27.02.2009

An incident occurred in Oulu Terminal Area (TMA) near Kiiminki on Tuesday, 9 September 2008 at 14:54 Finnish time. The incident involved a Finnish Air Force (FiAF) Fokker F.27 transport aircraft and a Hornet flight (a formation of four F-18 fighters). The Hornet flight was taking part in air defence exercise Ruska 2008. While approaching Oulu aerodrome after having completed an exercise mission, the flight leader of the Hornet flight climbed through the flight path of the Fokker transport aircraft, flying in Oulu TMA. The transport a/c had a three-person crew. On 16 September 2009 Accident Investigation Board Finland appointed investigation commission C5/2008L for this incident. Investigator Ari Huhtala was named investigator-in-charge, accompanied by investigators Timo Heikkilä, Timo Kostiainen and Captain Kimmo Koivuniemi (investigator appointed by the Military Aviation Authority) as members of the commission.

Fighter control had relayed Rovaniemi ACC’s inbound clearance to the Hornet flight. The ACC radar controller’s clearance entailed a visual flight rules (VFR) approach from the air defence exercise range to Oulu aerodrome. The Hornet flight was flying in an open formation that was approximately three kilometres wide and nine long. Once having entered the airspace below Oulu TMA the flight maintained an altitude of approximately 300 m and reduced airspeed to approximately 600 kmh. At the same time, a Finnish Air Force Fokker F.27 transport aircraft was on a VFR cross-country flight from Ivalo to Jyväskylä, flying at 450 m in the northeast corner of Oulu TMA. Right before the Hornet flight arrived at VFR reporting point SANKI, the Oulu Tower controller issued an approach clearance to the Hornet flight, telling them to maintain 900 m or above. After having received the clearance the flight leader initiated a climb and, failing to see the transport aircraft, crossed its path. The three other pilots in the flight saw the Fokker and turned to avoid it. Immediately after this the air traffic controller issued a traffic report cautioning of crossing traffic. The crew of the transport aircraft noticed the crossing traffic on the Traffic alert and Collision Avoidance System (TCAS) display, and a moment later they saw two fighters; one Hornet passed ahead of them and the other one below them.

The investigation revealed that special attention is needed to coordinate FiAF air defence exercises with general ATS services. The risk analysis prepared for exercise Ruska had some shortcomings, particularly with regard to ATS services. Flight plan instructions pertaining to the handling of exercise sorties should have been more detailed. Correspondingly, the operation of certain ATC units should have been analysed in greater detail. The investigation also revealed that there were technical shortcomings of varying degree in ATS communications. Cooperation between fighter control and ATC units showed need for improvement.

The incident was caused by the TWR controller failing to issue early enough the traffic reports of significant VFR traffic. Instead, without first confirming their altitudes, the controller attempted to separate the aircraft by means of altitude. A contributing factor was that neither the flight progress strip at Oulu TWR nor the SSR radar return indicated the true altitude of the Hornet flight. Since the flight leader’s SSR transponder Mode C was not available, the radar display only indicated the altitude given in the flight plan instead of the true altitude. Furthermore, inconsistent regulations and orders pertaining to air defence exercise procedures in use at Oulu TWR at the time only reinforced the air traffic controller’s mistaken understanding of altitudes used by military aircraft when returning to base in Oulu.

During the time of the investigation, the investigation commission learned that Finavia had initiated a review of the ANS Operation Manual with the purpose of harmonizing regulations and publications. Finavia also updated some Airspace Management (ASM) processes and introduced them on 1 October 2008. Moreover, Finavia is presently drafting regulations for the preparation of Air Traffic Control units’ local rules and regulations. Finavia and the Civil Aviation Authority are also studying whether it is possible to expedite the permit process related to changing the Eurocat system database. In addition to taking these actions, the Memorandum of Understanding between regional ATS authorities and the Finnish Air Force Headquarters has been updated. The update included SSR transponder usage in military aviation.

The investigation commission issued four safety recommendations. The first recommendation advises Finavia to publish regulations on topics that can be included in local rules and regulations. The second one advises the Finnish Air Force Headquarters to publish Airfield Special Regulations for Oulu aerodrome, together with Finavia. The third recommendation urges the Finnish Air Force and Finavia to officially adopt all Airfield Special Regulations as well as related In-Flight Guides (IFG). The fourth recommendation advises Finavia to correlate the flight plan data and default altitude information in Eurocat SSR radar target datablocks.

The Finnish Civil Aviation Authority had nothing to add to the investigation report. The Military Aviation Authority (MAA) proposed an additional recommendation regarding cooperation with ATS and fighter control units. The Finnish Air Force Headquarters concur with the MAA’s statement, included as Appendix 1 to this investigation report. The specifics are taken into account in the investigation report. Finavia’s statement is included as Appendix 2 to the investigation report.

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