What happened
On 5 September 2022, Lyon-Saint-Exupéry airport was operating in a single-runway configuration on runway 17L due to maintenance work on runway 17R. At approximately 08:14 UTC, an Air Algérie Boeing 737-800, registered 7T-VKR, was established on the ILS approach for runway 17L.
Shortly thereafter, the tower controller instructed the crew of a KLM Embraer ERJ-175, registered PH-EXH, to cross runway 17R. After a landing Airbus A320 had vacated the runway, the controller asked the Embraer crew if they were ready for immediate takeoff. The crew confirmed readiness, and the controller cleared them to line up and wait on runway 17L. The Boeing 737 was approximately 4.3 NM from the threshold at this time.
At 08:16:31, the controller cleared the Embraer to take off. However, the Embraer crew applied the brakes and delayed the start of the takeoff run. Meanwhile, the Boeing 737 continued its approach. The controller, attempting to optimize traffic, cleared the Boeing to land while the Embraer was still in the process of taking off. The Boeing crossed the runway threshold at a height of approximately 60 ft, while the Embraer was still near the opposite threshold. To avoid a potential conflict that might have forced a low-level go-around, the controller allowed both aircraft to continue their respective maneuvers. There were no fatalities or injuries and no damage to the aircraft.
The investigation
The BEA examined the sequence of events using flight data recorders, radio communications, radar data, and controller statements. The investigation focused on the air traffic management procedures at Lyon-Saint-Exupéry, specifically regarding single mixed-mode runway operations.
The investigators analyzed the functionality of the new A-SMGCS Type 2 ground radar system, which had been recently commissioned. They also reviewed the regulatory framework regarding reduced separation minima and the controller's awareness of recent changes to the airport's Operations Manual. The investigation also looked into the coordination between the tower controller and the tower assistant.
Findings
- The primary cause of the separation loss was the controller's attempt to optimize traffic efficiency by inserting a departure between two arrivals without sufficient safety margins.
- The controller's decision-making was based on obsolete separation standards, as they had not fully assimilated recent regulatory changes that abolished reduced separation minima for runway 17L.
- The controller and assistant were distracted by frequent notifications and alerts from the newly implemented A-SMGCS ground radar system.
- There was a lack of formalized working methods or specific approach fixes for managing single mixed-mode runway operations in non-low-visibility conditions.
- The A-SMGCS alert settings were improperly configured, as they were still based on the old, abolished separation minima, which contributed to the controllers' confusion.
- The controller's strategy failed to account for unexpected delays, such as the Embraer crew's delay in starting the takeoff run.