Incident Description
On 1 April 2015, in the Warsaw Flight Information Region (FIR EPWW), an Airbus A319 and an Airbus A320 came into close proximity near the EVINA navigation point. The A319 was en route from BOKSU to TUSIN at flight level FL 380, while the A320 was flying from YABER to TUSIN also at FL 380. Due to converging flight paths, the air traffic controller reduced the speed of the A319 to Mach 0.77 and cleared the A320 to proceed directly to the MIKOV point while maintaining Mach 0.79.
Near EVINA, the A319 crew began to accelerate. The controller instructed the A319 to turn left to a heading of 200°, then again left to 180°, resulting in the A319 passing behind the A320 at a distance of approximately 6.8 nautical miles, below the required 7 NM lateral separation. Strong and variable winds were present in the sector during the event.
Findings
The investigation revealed that the controller was on his second shift after two days off. The number of open sectors was appropriate, and traffic density was moderate. The controller held a valid air traffic control license with ACS rating since 2000 and had completed a refresher course in January 2015.
Initial measurements of distance and ground speed differences did not indicate a separation loss within FIR EPWW, so intervention appeared unnecessary. However, the controllers did not coordinate with ACC Prague for the A319 to turn right at HLV, which would have increased lateral separation. Instead, the A320 was cleared to MIKOV on a collision course with the A319. No inquiry was made about spot wind at FL 380 before vectoring; wind slowed the A320 and accelerated the A319.
There was an option to hold the A320 at FL 370, but the previous sector controller had cleared it to FL 380 (with coordinator approval) and initiated speed adjustments. Speed adjustments negatively affect flight economy over a long portion of the flight. Traffic information was not provided to the crews.
Cause
The incident was attributed to errors in air traffic management work.
Actions Taken
The investigating body recommended providing the final report to the involved controller and adding the materials to the ATS training database for use in initial and refresher training.