What happened
On September 3, 1997, at approximately 17:00 local time, a near-collision occurred near Lappeenrania Airport, Finland, involving three aircraft: a Hughes 296C helicopter (OH-HLT), a Cessna 172M tow aircraft (OH-CKQ), and an SZD-51-1 glider (OH-773). The incident took place in Class D airspace under Visual Flight Rules (VFR).
The helicopter, returning from a photography flight, contacted Lappeenranta Approach to request landing instructions. At the same time, the Cessna 172M was performing a glider tow operation. The air traffic controller provided traffic information to the helicopter and issued a departure clearance to the Cessna 172M, noting its left turn after takeoff.
As the aircraft tracks intersected, the distance between the helicopter and the tow combination closed rapidly. The helicopter pilot, unable to see the tow combination early enough due to sun glare on the canopy and the aircraft being obscured by the cockpit frame, asked the controller for the position of the tow aircraft. The controller responded that the aircraft was on the runway end of runway 24, but failed to specify which side of the runway centerline the aircraft was on. Both pilots eventually performed right-hand avoidance maneuvers, passing each other with an estimated horizontal separation of 30–50 meters and a vertical separation of approximately 20 meters.
The investigation
The investigation examined the communications between the air traffic controller and the pilots, the visual conditions at the time of the event, and the flight paths of all involved aircraft. The investigation established that while the controller provided appropriate traffic information, the specific instruction regarding the position of the tow aircraft was imprecise. The investigation also looked into the visibility factors, including sun glare and cockpit obstructions, that affected the helicopter pilot's ability to maintain visual contact with the tow combination.
Findings
- The incident was caused by the helicopter pilot failing to detect the glider tow combination in a timely manner.
- Sun glare reflecting off the helicopter's canopy and the position of the tow aircraft behind the cockpit structural members hindered visibility.
- The air traffic controller's response to the helicopter pilot's inquiry regarding the tow aircraft's position was imprecise, as it did not specify which side of the runway centerline the aircraft was located.
- The tow aircraft pilot initially expected the helicopter to approach from a different direction based on previous traffic information.
- Both aircraft crews performed appropriate avoidance maneuvers in accordance with visual flight rules.