What happened
On October 17, 2010, at approximately 16:50 local time, a serious separation incident occurred in Class E airspace near Lübeck-Blankensee airport. An Airbus A320-233 operating an IFR flight from Gdansk, Poland, was descending toward runway 25. Simultaneously, a VFR glider tow formation, consisting of a Grob G 109 B and an ASW 27-18E, was performing a flight pattern south of the airfield.
As the A320 descended through 3,000 feet, the crew observed traffic on their TCAS display. While the A320 crew maintained visual contact with the tow formation, the aircraft's TCAS issued a Resolution Advisory (RA) for a climb. During the maneuver, the glider tow was performing a turn. The pilot of the Grob G 109 B attempted to avoid the A320 by maneuvering downward, which resulted in the towed ASW 27-18E striking the tow rope. The impact caused the left winglet of the glider to break off. There were no injuries to the crew or passengers on any of the involved aircraft.
The investigation
The BFU investigation examined radar recordings, flight data from the A320, and radio communications between the Bremen Radar controller, the Lübeck Tower, and the aircraft crews. The investigation focused on the coordination between air traffic control sectors and the situational awareness of the pilots involved. The BFU also reviewed the operational procedures of the airline involved, noting that the crew was managing a high workload due to a short approach.
Findings
- The primary cause of the incident was that the crews of the involved aircraft failed to recognize the collision risk in time, and the A320 performed a lateral correction that was too late and insufficient to maintain safe separation.
- The A320 was being vectored by radar in a manner that made its path unpredictable to the glider pilots, especially given the aircraft's high ground speed of 260 knots.
- The radar controller provided a traffic information update that contained a discrepancy regarding the aircraft type and direction, and failed to issue a timely avoidance recommendation.
- The glider tow pilot was unable to communicate the specific nature of the flight (a tow operation) to the coordination controller, as the towed glider was on a different radio frequency.
- The local tower controller did not provide timely traffic information to the pilot of the Grob G 109 B, which could have significantly increased his situational awareness.
- The A320 crew did not independently initiate a lateral maneuver or terminate their descent despite the proximity of the other aircraft.