What happened
On August 28, 2005, at 11:28 UTC, a commercial flight, SAS 765, operating a De Havilland DHC8D, was being vectored by Prague Radar for an ILS approach to runway 06 at Prague Airport (LKPR). While descending through 4,000 ft AMSL, the crew of SAS 765 reported visual contact with unknown VFR traffic approximately 2 to 3 NM away. The crew subsequently identified the traffic as a glider being towed by another aircraft.
At the same time, a Z 142, registration OK-PNM, was performing a tow operation for an ASW 19 glider, registration OK-5117, near Nové Strašecí. The tow aircraft had departed from Kladno (LKKL) and was climbing toward the lower boundary of the Prague TMA II airspace.
The investigation
The ÚZPLN investigation examined radar records, radio communications between SAS 765 and Prague Radar, and statements from the pilots involved. The investigation reviewed the flight paths of the commercial airliner, the tow aircraft, and the glider.
Investigators established that the crew of SAS 765 followed all instructions provided by air traffic control. The pilot of the Z 142 reported climbing to approximately 2,886 ft AMSL near Kačice to reach the TMA II boundary and maintained this altitude until the glider was released southwest of Nové Strašecí. The pilot of the glider confirmed the flight was conducted to facilitate thermal soaring. Radar data was used to reconstruct the sequence of events, though the investigation noted that the Z 140 and the glider were not equipped with SSR or flight recorders.
Findings
- The crew of SAS 765 correctly identified and reported the presence of VFR traffic to air traffic control.
- The pilot of the Z 142 possessed the necessary qualifications and was aware of the TMA II boundaries.
- The air traffic controller (APP EC) had issued descent instructions to SAS 765 at a time when no conflicting IFR traffic was identified in the sector.
- Due to insufficient and conflicting objective information, it could not be determined whether an actual airspace infringement or a violation of minimum separation standards occurred.
Safety action
- Conduct additional analysis of incidents with Aeroklub České republiky pilots to increase their awareness of flight regulations when operating near international airport TMA/CTR boundaries.