Description

On 18 October 2022, an Airbus A321 (EC-JRE) operated by Iberia on a scheduled international passenger flight from Madrid to Venice as IB3242 initiated a very low go-around from an ILS Cat 3 approach in thick fog when instructed to by ATC. This was necessary because a Boeing 737-800 (EI-EBE) operated by Ryanair on a scheduled international passenger flight from Venice to London Stansted as FR973 was still on the runway after a line up and wait clearance had been given. The A321 had not made any calls to TWR, and the late instruction and slow response meant that it passed very close overhead the 737.

Investigation

A Serious Incident Investigation was carried out by the Italian Agenzia Nazionale per la Sicurezza del Volo (ASNV) based on recorded ATC data, reports from the captains of both aircraft and details of the internal investigation carried out by the ANSP. 

The 38-year-old Airbus A321 captain had a total of 8,300 hours flying experience which included 7,970 hours on type, and the 53-year-old Boeing 737-800 Captain had a total of 14,930 hours flying experience which included 1,105 hours on type. The TWR controller involved had almost 14 years experience as a controller and had been employed as such at Venice since April 2010.

The prevailing weather conditions at the time the conflict occurred were such as for LVP to be in force. The Investigation noted that the METAR was giving OVC at 100 feet with a surface visibility of 400 metres and a TDZ RVR increasing through 650 metres. 

What Happened

The captain of the departing 737 reported that whilst holding short of runway 04R at taxiway ‘A’ in Low Visibility Procedures awaiting landing traffic, both pilots heard another aircraft on approach check in with TWR. After the first aircraft had landed, the 737 was cleared to line up and wait on 04R, which it then did to await a takeoff clearance.

Whilst the A321 was at approximately 11nm on a Cat 3 ILS approach to runway 04R, and the 737 was lined up at the beginning of the same runway, the TWR control position was being handed over to a new controller. When the incoming controller sat down in the operating position, he inadvertently inserted the transmit plug of his headset into a telephone line socket. Unaware of his consequent inability to transmit, the controller then issued a takeoff clearance to the 737. No readback of this intended clearance was received, but the controller did not notice this. 

After a couple of minutes had passed with no radio calls on the frequency, the 737 crew reported having observing the A321 on their TCAS display approaching the same runway and descending through about 1,200 feet. The 737 crew made radio calls to TWR to remind the controller that they were still holding position on the runway as instructed, but received no response.

Around the same time, the controller, believing he had issued a takeoff clearance to the 737 and observing that it had not started its takeoff roll, recognised - without understanding why - that there was a potential conflict between the two aircraft. He then made a series of unsuccessful transmissions using his still improperly connected headset, which may have occurred at the same time as the calls made by the 737 crew reiterating their presence on the runway. 

Observing the A321 was now only 1.7 nm from the runway at 600 feet and having heard no calls from TWR or the A321, the 737 crew instructed the A321 to go around on frequency 121.5 MHz using their second radio. Because they received no response on that or the TWR frequency, they reported having begun to increase thrust in order to clear the runway at taxiway B. As they did so, with the A321 passing approximately 400 feet, the controller, “probably using his hand held microphone”, instructed the A321 to go around and then repeated the instruction and advised that the runway was occupied. This controller transmission ended with the A321 approximately 1.1 nm from the runway but it was “about 14 seconds” before a readback was made by which time the A321 was less than 1 nm from the runway. A missed approach was commenced. Radar showed that with just 0.7 nm to go before the aircraft reached the beginning of the runway, the first positive vertical speed was indicated as the controller instructed the 737 to hold position. The 737 acknowledged and requested an explanation for what had just happened. The TWR controller responded that “he had encountered some problems with his microphone which had prevented them hearing a previous communication”. 

Once the A321 was clear of the climb out, the 737 was cleared for takeoff and the A321 was subsequently cleared for another approach. After landing, the A321 crew were also informed by the controller that he had experienced a problem with his microphone.

Why It Happened

The TWR controller position concerned was inspected, and it was noted that when seated, a controller would not be in a good position to see all the connector receptacles dedicated to various communication channels available to a headset or a handset.

It was also noted that at the time the position had been handed over, it was the off-going controller who had issued the lineup and wait instruction to the 737 and who had also instructed the A321 to continue approach, thereby “implicitly delegating to the oncoming controller the issue of a takeoff clearance to the 737”.  

It was considered that the handover - which itself represents a potentially critical situation in air traffic management - had therefore “occurred at a non-optimal time in an evolving scenario” which was occurring with LVP in force.

The controller newly in position had been “unable to realise that he was not able to communicate with aircraft on the frequency in use even after not receiving any readback of the takeoff clearance which he believed he had issued". Only when he heard the 737 crew telling the A321 to go around did he resolve his communication problem by using his handset.

The Cause of the event was the oncoming controller’s improper insertion of the connector of his headset into a telephone line connector making R/T transmissions to aircraft impossible.

Five Contributory Factors were identified:

• Carrying out the handover between the off-going and incoming controller at a non-optimal time when an operationally complex scenario existed.
• The fact that the controller in question did not detect the absence of a readback after issuing a takeoff clearance to the 737.
• The failure of the newly in-position controller to promptly identify the origin of the radio communications malfunction.
• The operating ergonomics of the TWR control panel in relation to the connector panel for communication devices.
• The low-visibility conditions on the day of the event, which may have prevented the A321 crew from seeing, well in advance, the 737 lined up and stationary on the runway.

Safety Action taken by the ANSP ENAV included addressing the following matters: 

• The need to carry out the handover of positions from one controller to another in compliance with its provisions.
• The need to physically separate the connector intended for headphones/microphone from the one intended for the handset. 
• The importance of controller awareness and training to ensure that radio and other communications are correctly performed. 
• The need for a strengthening of the skills of controllers in problem solving.

The Final Report was only published in the Italian language and was as one of a batch of 10 ‘Short Reports’ published together. No Safety Recommendations were made on the basis that actions taken by the ANSP were sufficient. 

Related Articles

• The Handover-Takeover Process (Operational ATC Positions)
• Read-back or Hear-back
• Low Visibility Procedures
• Missed Approach
• Low Level Go-Around