What happened
On 14 November 2019, heavy snowfall at Lyon Saint-Exupéry airport triggered Low Visibility Procedures (LVP). During the snow clearance operations, a Boeing 737-800, operated by Air Algérie and registered 7T-VKR, was taxiing for departure on runway 35L.
At approximately 22:33 UTC, the local controller cleared the aircraft to line up and take off. Simultaneously, the ground controller cleared a pair of snowploughs (call sign ELEC8) to enter the runway to perform a junction between taxiway A4 and the runway. As the lead snowplough entered the runway safety area, the local controller observed the vehicle on radar and immediately instructed the Air Algérie crew to reject their takeoff run. The crew applied maximum thrust but reduced power seconds later after the instruction. The aircraft eventually vacated the runway via taxiway A6.
The investigation
The BEA investigation focused on the coordination between the ground (GND) and local (LOC) controllers, as well as the management of the aerodrome's "Snow Plan." Investigators examined radio communications, radar data, and the workload of the controllers during the period of intense snowfall. The investigation also looked into the configuration of stop bars and the specific frequencies used by ground vehicles during the incident.
Findings
- The runway incursion was primarily caused by a coordination failure between the GND and LOC controllers.
- The ground controller had cleared the snowploughs to enter the runway while the local controller was unaware of the vehicle's entry into the runway safety area.
- A significant contributing factor was the decision to keep the snow-clearing vehicles on the GND frequency, which prevented the local controller from receiving direct updates on their movement.
- High controller workload and poorly defined roles during the snow episode contributed to the confusion.
- The stop bar configuration was incompatible with the specific paths taken by the snow-clearing vehicles.
- The aerodrome's Snow Plan was found to be too formal and disconnected from the operational realities of managing a sudden, heavy snowfall event.
Safety action
The BEA issued four safety recommendations addressing the regulation and suspension of operations during snow episodes, the coordination of snow clearance operations, and the improvement of the aerodrome's Snow Plan.