What happened
On July 18, 2010, at 17:06 local time, a Boeing 737-800 operating an IFR flight from Trapani, Italy, to Bremen, Germany, experienced a serious disturbance during its approach to runway 27. The aircraft, carrying 152 passengers and six crew members, was in a descent at approximately 4,500 feet when the crew observed a white glider crossing their flight path from right to left. The minimum vertical separation between the two aircraft was reported by the 737 crew as approximately 200 ft, while the maximum lateral distance was 0.36 nautical miles. Radar data indicated that the flight paths of the two aircraft crossed at an angle of approximately 105 degrees.
The investigation
The BFU examined radar records from the air traffic control service and radio communications between the controller and the 737 crew. The investigation also reviewed meteorological reports, which indicated visibility exceeding 10 kilometers and no significant cloud cover below 5,000 feet. The investigation focused on the sequence of traffic information provided by the controller and the subsequent visual contact made by the 737 crew.
Findings
- The air traffic controller identified a primary target on radar at the 12 o'clock position but was uncertain if the target was an aircraft. As a precaution, the controller issued traffic information to the 737 crew.
- The 737 crew confirmed receipt of the information and subsequently established visual contact with the glider.
- The event occurred in Class E airspace, where IFR flights are separated from one another, but VFR flights (such as the glider) are not subject to separation services.
- The lack of separation requirements for VFR flights in Class E airspace contributed to the close approach, as the controller provides traffic information where possible but does not provide active separation for VFR traffic.