What happened
On August 30, 2009, at approximately 15:37 local time, a mid-air near-collision occurred approximately 8 nautical miles south of Akureyri Airport. The incident involved a Beech 77, registration TF-BEZ, operating a private VFR flight from Reykjavík, and a Fokker 50, registration TF-JMR, operating a scheduled passenger flight also en route from Reykjavík.
While flying in visual flight rules (VFR) conditions, the pilot of TF-BEZ became disoriented while flying above a cloud layer and contacted Air Traffic Control (ATC) for assistance. Due to simultaneous malfunctions in the ATC communications equipment, transmissions were intermittent and required repeated clarifications. During this period, the pilot of TF-BEZ attempted to descend through a gap in the clouds to regain visual reference. Simultaneously, the crew of TF-JMR was descending through the same cloud layer in instrument flight rules (IFR) conditions.
As the two aircraft approached, the crew of TF-JMR observed TF-BEZ through the clouds. The aircraft passed with a horizontal separation of approximately 100 meters and a vertical separation of roughly 500 feet. The crew of TF-JMR performed an evasive maneuver, banking right to avoid the encounter.
The investigation
The RNSA investigation established that the pilot of TF-BEZ was unaware that their descent would place them in the path of the descending TF-JMR. The investigation highlighted several critical technical and procedural failures:
- Transponder Limitations: The transponder on TF-BEZ provided position data but lacked Mode C capability, meaning ATC could not monitor the aircraft's altitude.
- Communication Failures: ATC was experiencing significant hardware issues, necessitating manual switching of transmission paths to ensure the pilot of TF-BEZ could hear instructions.
- Frequency Mismanagement: At the time of the incident, TF-BEZ was operating on the ATC frequency rather than the Akureyri Tower frequency, despite being within the airport's Class D airspace.
- Inadequate Traffic Information: While ATC informed the pilot of TF-BE4 that TF-JMR was descending, they failed to provide specific information regarding the relative position and distance between the two aircraft.
Findings
- The primary contributing factor was the lack of Mode C altitude reporting on TF-BEZ, which prevented ATC from maintaining an accurate vertical profile of the aircraft.
- The failure of the TCAS (Traffic Collision Avoidance System) on TF-JMR to provide a Resolution Advisory (RA) was due to the absence of altitude information from the TF-BEZ transponder.
- Communication gaps caused by faulty ATC equipment hindered the effective exchange of critical flight information.
- The pilot of TF-BEZ was navigating through a complex environment of broken cloud layers and mountainous terrain (with peaks near 5,000 feet) while disoriented.