What happened
On August 23, 2010, at 20:51 local time, a serious near mid-air collision occurred within the Pori Terminal Control Area (TMA). A Piper PA-28-140, registration OH-PCE, was conducting a local VFR flight. During the flight, the pilot decided to climb to approximately 2,700 feet to show scenery to a passenger, which resulted in the aircraft entering the controlled TMA airspace without the required air traffic control clearance.
Simultaneously, a Jet Air Jetstream J32, registration SP-known (callsign JEA874), was operating an IFR route flight from Helsinki to Pori. As the Jetstream was approaching runway 30, the two aircraft crossed paths at an angle of approximately 90 degrees. At the moment of closest approach, the vertical separation was roughly 400 feet, and the horizontal distance was approximately 0.2 nautical miles.
The investigation
The investigation examined radar recordings, radio communications, and interviews with the air traffic controller and the pilots. Investigators found that the Piper PA-28-140 was operating with a transponder set to code 2000, but the pilot had not engaged Mode C. Consequently, the transponder failed to transmit altitude information to the controller's display.
The controller had observed an aircraft with code 2000 near Harjavalta but, because no altitude data was available, assumed the aircraft was in uncontrolled airspace below the TMA floor. Because the traffic was not identified as a threat, no traffic information was issued to the Jetstream. The investigation also noted that the Jetstream crew performed an unannounced climb of 400 feet to avoid the traffic, a maneuver that was not reported to the controller at the time.
Findings
- The primary cause of the incident was the unauthorized entry of the Piper PA-28-140 into the controlled Pori TMA without air traffic control clearance.
- The pilot of OH-PCE had insufficient knowledge of the specific requirements for flying in different airspace classes and failed to verify altitude restrictions via aeronautical charts.
- The pilot's attention was diverted by showing scenery to a passenger, leading to inadequate airspace monitoring.
- The lack of Mode C altitude reporting on OH-PCE prevented the controller from identifying the aircraft's presence in controlled airspace and prevented the Jetstream's TCAS from issuing a Resolution Advisory (RA), though a Traffic Advisory (TA) was issued.
- The air traffic controller did not assign a specific altitude to the VFR flight, which was required by regulations because the flight path did not follow a published transition.
- The Jetstream crew did not notify the controller of their altitude change performed to avoid the collision.