The prevention of collisions, whether it be in-flight collisions or high-energy collisions on the ground, is the air traffic control’s main mission. While accidents of this type have been rare in recent years, probably due to the development of prevention and recovery systems, the collision between a De Havilland DHC8 and an Airbus A350 at Tokyo (Japan) at the beginning of 2024 along with the frequent occurrence of incidents or even serious incidents must serve as a reminder of the catastrophic potential of a collision of this nature and lead to the robustness of our barriers being questioned. In the majority of these cases, these occurrences bring to light the criticality of ground/aircraft and ground/ground coordination and communication.
1. Clearance to land on a runway occupied by another aeroplane at runway threshold
On 31 December 2022 at Bordeaux-Mérignac, the crew of the Airbus A320 registered OE-INE were cleared to land on runway 23 although a Robin DR400 had been holding at the runway threshold for around four minutes. The pilot of the DR400 who did not have information about the exact position of the A320 reminded the controller of his position. The controller then became aware of the situation and ordered a go-around. The crew of the A320 who were concentrated on the aiming point after the threshold had not identified the presence of the DR400. The minimum height of the A320 during the incident was estimated at 103 ft at around 260 m from the threshold of runway 23. It flew over the DR400 at a height of 178 ft (around 53 m). The investigation showed that there was a reduced number of controllers in the control tower at the time of the occurrence. A single controller was simultaneously holding the GND, TWR, APP and FIS positions which contributed to him forgetting that the DR400 was at the runway threshold.
2. Lapsus by the control service when giving a landing clearance, read back not checked, missed approach on short final on request from an aeroplane lining up
The serious incident to the Boeing 787 registered N16009 on 20 July 2020 at Paris-Charles de Gaulle airport was the result of a lapsus by the controller who cleared the crew to land on the parallel runway of the twin runways for which the crew of the Airbus A320 registered OE‑IJF had been given line-up clearance. The controller not checking the read-back and the crew of the 787 not clarifying the situation meant that the error was not identified. The situation was detected by the crew of the A320 when they lined up on the runway. They asked the controller about the presence of the 787 on final and faced with the imminence of a potential collision, the crew of the A320 asked the aeroplane on final to carry out a go-around. The crew of the 787 who had sight of the A320 on the runway carried out a missed approach.
3. Windshear warning on final approach, track deviation during the missed approach, abnormal proximity with an aeroplane taking off from a parallel runway, TCAS resolution advisory
The investigation into the serious incident to the Embraer ERJ170 registered F-HBXK on 21 October 2020 at Paris-Charles de Gaulle questioned the missed approach operational conditions in the WINDSHEAR procedure. In this occurrence, the crew reacted to a windshear warning by flying a missed approach and keeping the wings level as indicated in the corresponding procedure. This manoeuvre carried out in strong crosswind conditions, contributed to the aeroplane closing in on the Airbus A320 registered OO-SNE taking off from the parallel runway of the twin runways.
4. Incursion of snow-clearance vehicles cleared to enter the runway, rejection of take-off run by an aeroplane
On 14 November 2019, there was a substantial snowfall in the Lyon region and LVP conditions were in force at Lyon St Exupéry airport. The GND controller cleared vehicles to enter the inner runway to clear snow to join a taxiway and the runway. The vehicles were kept on the GND frequency. At the same time, on the TWR frequency, the TWR controller cleared the crew of a Boeing 737 to line up and take off from this same runway. The investigation particularly highlighted that the Snow Plan whose definition was too formal, was in part, disconnected with operational realities. This may have led to a high workload for the controllers. There was also no clear framework concerning the use of frequencies for the vehicles.
5. Loss of separation between an aeroplane taking off and an aeroplane going around, TCAS resolution advisory
On 12 April 2019 at Strasbourg, without the volume of traffic making it necessary, and probably for reasons of optimization and operational efficiency, the controller inserted a take-off between two landings. He did not regulate the approach speed of a Boeing 737 and then belatedly informed the crew of this 737 that the clearance to land would be late. The strategy chosen provided no margins and did not allow for possibilities such as the time taken by the preceding aeroplane to vacate the runway or the time taken by the crew of the aeroplane taking off to start the manoeuvre despite being asked to take-off immediately. The report refers to a previous incident that occurred at Strasbourg and was investigated by the BEA, namely the loss of separation between an Embraer ERJ145 taking off and a Boeing 717-200 landing, which led to the destabilization of the flight path of the latter on very short final in LVP conditions. More recently, the BEA has published a report concerning a Boeing 737 landing on a runway occupied by an Embraer ERJ175 taking off in a similar context.
