Synopsis
On Thursday, November 23, 2017, at approximately 07:54 UTC, a serious incident involving a loss of separation occurred in the Riga Flight Information Region (FIR). The aircraft involved were an Airbus A320-200, registration VP-BWI, call sign SDM-6641 (operated by the airline "Russia" on a scheduled flight from Saint Petersburg Pulkovo to Berlin Schönefeld) and two military F-15C aircraft, call signs MA01 and MA02. The F-15Cs had departed from Šiauliai (EYSA) at 07:45 as part of an ALPHA Scramble mission tasked by the Combined Air Operation Centre (CAOC) at Uedem, Germany, to interrogate targets transiting over international waters with transponders off. The incident was classified as a serious incident by the Transport Accident Investigation Bureau (TAIIB).
History of the Flight
At 07:41:54, Vilnius ATC informed Riga Sector West Controller about three operational traffic aircraft from Kaliningrad at flight levels 350 and 360. At 07:42:24, the MCU Control Reporting Centre "KARMELAVA" Fighter Allocator (FA) contacted the Operational Supervisor (OSUP) to notify of an Alpha Scramble mission heading into Riga airspace. The FA initially requested flight level 250, and reduced separation of 1,000 feet below FL290 was agreed. At 07:46:28, the heading changed to 210° and flight level 300. At 07:46:54, 2,000-foot separation was agreed. At 07:52:42, the FA requested FL330 and above 300 to go supersonic. After coordination, at 07:52:55, the OSUP cleared the military aircraft to climb to FL340 and go supersonic.
Communications and TCAS Event
At 07:51:34, the A320 pilot contacted Riga Control, reporting position TENSI at flight level 360. At 07:54:15, the controller informed the A320 of military traffic 2000 feet below about to go supersonic. At 07:54:23, the A320 crew reported a TCAS Resolution Advisory (RA). The crew followed the TCAS instructions. The F-15Cs, despite being cleared to FL340, violated the cleared level, leading to the TCAS RA. Radio recordings confirmed that the Fighter Controller had cleared the F-15s to FL340, which was acknowledged by the pilot at 07:53.
Separation and Damage
The minimum horizontal separation recorded during the incident was 3.6 nautical miles, and the minimum vertical separation was 200 feet. No damage to aircraft was reported. The incident occurred in Riga FIR Class C airspace (TMA). The civil aircraft continued its flight after the TCAS RA.
Investigation
On November 24, 2017, the TAIIB was notified by the Safety Management Department of the Air Navigation Service Provider LGS. The TAIIB classified the occurrence as a serious incident and initiated an investigation under Annex 13 to the Chicago Convention and EU Regulation No 996/2010. Requests for information were sent to the Baltic Air Surveillance Network and Control System Combined Control and Reporting Centre KARMELAVA and LGS.