Incident Overview
On 13 April 2002 at approximately 16:40 UTC, an Airprox (near collision) occurred between two commercial airliners in French Class A airspace south of IRMAR, within the Geneva UAC area. The involved flights were EZY872, a Boeing 737-33V operated by Easy Jet from Nice to Amsterdam, and LBT534, an MD-83 operated by Nouvelair from Monastir to Brussels. Both flights were following the same route IRMAR-MOLUS-PENDU.
Sequence of Events
At 16:36, EZY872 contacted the INS sector on 125.55 MHz, climbing to FL260 and requesting FL360. The radar controller cleared it to FL300 and later to FL350 after coordination between MOLUS3 and MOLUS4 sectors. LBT534 was on the same route at FL320, in contact with MOLUS4. At 16:41:34, the Short Term Conflict Alert (STCA) activated. At 16:41:51, the MOLUS3 controller instructed EZY872 to turn left 30 degrees. The pilot acknowledged and reported having the other aircraft on TCAS. At 16:41:59, radar data showed a minimum vertical separation of 200 feet and lateral separation of 1.5 nautical miles. At 16:42:02, the Aix controller called MOLUS4 to report the incident. At 16:42:04, the MOLUS4 controller informed LBT534 of traffic at 11 o'clock, 2 NM, climbing through its level. The pilot reported the traffic in sight. At 16:42:13, EZY872 was instructed to contact MOLUS4 frequency 124.030 MHz, passing FL327. At 16:42:43, EZY872 reported on MOLUS4 frequency at FL350, heading 324°. The controller instructed it to resume own navigation on route MOLUS-PENDU. At that time, EZY872 was at FL330, 1000 feet above LBT534.
Established Facts
Both flights were operating under Instrument Flight Rules (IFR). The radar controllers and coordinators held valid licenses. Radio communications were in English. Visual Meteorological Conditions (VMC) prevailed. The coordinator of MOLUS4 stated that when MOLUS3 requested a flight level for EZY872, the aircraft was about 30 NM from IRMAR and not yet visible on his main radar screen; he had to zoom on an auxiliary screen and saw EZY872 but not LBT534. According to radar recordings, both aircraft were visible. The pilot of EZY872 reported a TCAS Traffic Advisory (TA) but no Resolution Advisory (RA). The pilot of LBT534 reported seeing an unidentified traffic on his TCAS at the same altitude, approaching from behind and beginning a slow descent; he assumed it was a military aircraft. He also claimed he received no traffic information from Geneva control.
Analysis (from the investigation)
The investigation noted that the MOLUS4 coordinator, when asked for a flight level for EZY872, requested the aircraft's position and granted FL350 without considering LBT534, which was 6 NM to the right laterally at that time. Both aircraft were then 27.5 NM from IRMAR. The coordinator later stated he did not see LBT534 on his radar. When the STCA alerted, EZY872 was still on MOLUS3 frequency despite the coordinator having requested its transfer.
Aftermath
The coordinator of MOLUS4 filed an Airprox report. Easy Jet filed an incident report on 20 May; the captain recalled visual conditions with another aircraft approaching but not within 5 NM, and his TCAS did not issue an alert. The captain of LBT534 filed a report on 27 May.