History of the Flight
On 25 November 2014, at Paris-Charles-de-Gaulle Airport, a serious incident occurred involving two commercial air transport aircraft. The Bulgaria Air Airbus A319, registered LZ-FBB (call sign LZB431), was arriving from Sofia, Bulgaria. The Freebird Airlines Airbus A320, registered TC-FBJ (call sign FHY542), was preparing to depart for Istanbul, Turkey.
At the time, runways 08L and 08R were in use as nominal twin runways: take-offs on 08L and landings on 08R. Landing aircraft were required to cross runway 08L to reach the terminals. The METAR at 08:30 UTC reported visibility of 9 km.
At 08:18:43, the LOC controller instructed the crew of LZB431, which had just vacated runway 08R via taxiway V5, to "hold short of 0 8 L, holding point S6." The crew read back correctly. At 08:18:51, the LOC controller cleared FHY542 for take-off from runway 08L.
At 08:19:34, the LOC controller told the LZB431 crew, "Bulgaria 4 3 1, number one, keep on taxiing." The crew read back using the same terms. At 08:20:17, LZB431 entered runway 08L via S6. One second later, the Runway Incursion Monitoring and Conflict Alert System (RIMCAS) warning was triggered. FHY542, performing the take-off run, was approximately 1,500 m before the intersection with S6 at an indicated airspeed of 139 kt.
At 08:20:37, FHY542 flew over the intersection with S6 at a height of around 500 ft. LZB431 had vacated the runway and stopped on taxiway T9.
Crew Statements
The Freebird Airlines crew stated that after being cleared for take-off, they saw the Bulgaria Air A319 approaching holding point S6 as they reached V1. They expected it to stop, but when it crossed the holding point, they decided to take off as rotation speed had been reached. They estimated flying over the A319 at around 100 ft.
The Bulgaria Air crew reported that after vacating runway 08R, they were initially told to hold short of runway 08L. While approaching the holding point, the controller said "number one, keep on taxiing." They interpreted this as a clearance to cross and read back the instructions. After crossing, the controller informed them they had not been cleared. They did not see the A320.
The Air France crew (flight AFR1089) noted that when the controller told the Bulgaria Air A319 to keep taxiing, they questioned whether it was a crossing clearance, knowing that explicit clearances were normally given.
The LOC controller stated that he started his shift at 08:00 and had requested assistance from a COR LOC controller due to high workload from reduced separations on final approach. After the Bulgaria Air flight vacated runway 08R, he instructed them to taxi to holding point S6. Realizing a potential conflict with the Air France flight, he gave priority to the Bulgaria Air flight. He then concentrated on an aircraft on short final and was informed by the COR LOC controller that the Bulgaria Air flight was crossing runway 08L, but it was too late to intervene.
The COR LOC controller noted that traffic was heavy with reduced separations, requiring increased monitoring. He observed the Bulgaria Air flight taxiing slowly but could not tell if it would stop. When it crossed the holding position marking, he alerted the LOC controller.
The ITM controller reported that the traffic peak was denser than usual, with ten aircraft on frequency and a tailwind component complicating speed reduction. A missed approach shortly after he took the position increased his workload.
Airport Information
Paris-CDG has two sets of twin parallel runways. For the south twin runways, aircraft land on 08R and take off from 08L, requiring landing aircraft to cross 08L. The AIP states: "Aircraft vacating runway 08R/26L... must NEVER cross RWY 08L/26R without first receiving specific ATC clearance." Taxiway S5 was closed, making S6 the first intersection taxiway after vacating via V5.
Altitude differences at the airport make it difficult for pilots crossing via S6 to see aircraft taking off from threshold 08L, as the first 500 m of runway 08L are about eight meters higher than the threshold of runway 26R.
RIMCAS
The airport is equipped with RIMCAS, which monitors ground movements and automatically detects runway incursions. It provides visual and aural alerts based on the seriousness of the situation. Level 1 alerts indicate a potential conflict, and Level 2 indicates an actual incursion. In this incident, the system triggered a warning one second after LZB431 entered runway 08L.