On 3 February 2018, an Airbus A320 (EI-CVB) being operated by Aer Lingus on a scheduled international passenger flight from Lyon to London Gatwick had just landed on runway 26L and was decelerating through approximately 60 knots when the crew saw a vehicle enter the runway and drive towards them. They were approaching the rapid exit taxiway (RET) on which they expected to leave the runway and did so and were followed onto the same taxiway by the vehicle. The Captain advised his intention to submit a Safety Report.
A Field Investigation was carried out by the Aircraft Accident Investigation Branch (UK) (AAIB). It was triggered by the A320 Captain’s Safety Report as both the Airport Operator and their ANSP, having investigated the concerns recorded in the Safety Report internally, had concluded that the actions of the vehicle driver and the controller had been, respectively, in accordance with the applicable runway inspection and ATC procedures. It was noted that the reporting 46 year-old Captain had a total of 12,000 hours flying experience which included 8,800 on type.
It was established that at the time the aircraft touched down on runway 26L, an airport operations runway inspection vehicle identified to ATC as “Leader 6” with two personnel on board was waiting at Holding Point G1 towards the end of Runway 26L for permission to carry out a routine runway inspection. About 12 seconds after the aircraft had touched down on a wet runway in light rain with a small tailwind component and whilst it was decelerating on the runway, the TWR controller asked the crew whether they “were making ‘Foxtrot Romeo’” (a RET approximately two thirds of the way along the 3,012 metre-long LDA following the displaced landing threshold). The crew response was that they were intending to “make the second one” by which they meant ‘Foxtrot Romeo’ which was the second of two RETs available, the first being about halfway down the runway. The controller then responded with “thank you that’s Foxtrot Romeo break, Leader 6 enter 26Left at Golf vacate behind the Aer Lingus at Foxtrot Romeo” which was duly acknowledged. The access Golf is approximately 360 metres beyond the RET Foxtrot Romeo.
The aircraft was “still on the runway at a reported speed of about 60 knots” and approaching RET Foxtrot Romeo when the crew observed a vehicle entering the runway ahead and travelling towards the aircraft. The aircraft vacated as anticipated on the Foxtrot Romeo RET and changed to GND “whilst Leader 6, having driven along the runway, then also vacated at RET Foxtrot Romeo”. The Captain subsequently stated that he had “been surprised to see the vehicle entering the runway and believed the vehicle’s clearance had been conditional on the aircraft vacating first” so he had submitted a safety report.
The ATC Perspective
Because the Captain had advised that he would be submitting a safety report, the ANSP conducted its own investigation during which the occupants of the vehicle involved stated that the aircraft Captain had told them that he had been “concerned that after he had landed he could see a vehicle on the runway (and that) due to the wet weather he could have missed the (anticipated) exit”. This ATC internal investigation concluded that the clearance given to the inspection vehicle had been in accordance with prevailing ATC SOPs and that there were consequently “no issues with the runway inspection process at Gatwick in general, or with this particular event”. The AAIB was subsequently told (although this was not in the ANSP Report) that the controller involved “had considered that, as a result of the transmissions after touchdown, the aircraft’s landing clearance had been amended for it to vacate the runway at RET Foxtrot Romeo” which in his opinion meant that “the aircraft was not now cleared beyond the RET”. However, the manager qualified this view by saying that “the transmissions had not contained the necessary phraseology for the clearance to have been effective, nor for the pilot to have understood that the vehicle would be appearing ahead of the aircraft”.
The Airport Operator’s Perspective
Following the incident, the Head of Airside Operations issued a verbal instruction that “operations vehicles were not to enter the runway ahead of a landing aircraft, regardless of their clearance, unless the aircraft was seen to be fully committed to vacating the runway”. However, a subsequent report on the incident completed by that department “largely reflected the ATC report with the ‘root cause’ section only quoting the ATC report findings” and coming to the same conclusions and closing the investigation, although it then continued with an additional section called “Preventative and Corrective Measures” in which it stated that “a joint review of inspection procedures between airside operations and the ATC services provider would be conducted, to explore potential opportunities for improvements to the safety and efficiency of runway inspections”. An initial meeting to start this ‘joint review’ was in April 2018 and it was agreed that the airside operations team would in future “provide 15 minutes notice to ATC before attempting to commence a normal runway inspection” and it was agreed that further meetings would be held monthly. One did take place in May but the only other one in 2018 was held in September. However, none of the issues discussed at these meetings related directly to the potential risk perceived by the reporting Captain.
Regulatory and Elective Requirements for Runway Inspections
Prior to EASA regulatory powers being extended to airports in 2014, UK national requirements had been for four inspections per day but although this was reduced to two per day by EASA, the airport elected to continue with four inspections per day. It was noted that additional information on inspections to that contained in the Aerodrome Manual was contained in a SOP published by the airport’s Standards Department but only covered runway 08R/26L and did not include any instructions on whether inspections on active runways should take place with or against the traffic flow. It was noted that because Gatwick depended on high intensity use of their single runway to be able to reach their (self-declared) traffic capacity, it was often necessary to conduct inspections in stages rather than as a single 3 minute non-stop run at the maximum permitted speed of 40 mph. It was noted that the declared single runway traffic capacity at Gatwick was 55 movements per hour “with plans to increase this further”.
As a result of the runway inspection review, the ANSP published a Temporary Operating Instruction (TOI) effective from 23 July 2018 which amplified the relevant content of the MATS (airport-specific) Part 2. This did not add much of direct significance to managing the risk of vehicle/aircraft conflict and did not detail the direction of inspection runs relative to the runway direction of use. However, it did state that if an inspection run was done in sections, then the final section may be done against the flow of traffic in which case, “vacating aircraft must be notified about the against traffic inspection plan and must clearly be established in the turn off the runway-centreline into the runway exit before the ops vehicle is instructed to enter the runway”. It was noted that the “hazard analysis and risk assessment” which was conducted as part of the process of producing this TOI had identified “a vehicle entering the runway ahead of an aircraft before the aircraft was established on a turn into a runway exit” as a hazard, but that on the basis of the frequency and potential severity of such events, this hazard was “deemed acceptable to ATC”. This analysis “did not consider the implications of an aircraft failing to exit the runway at its stated or cleared exit point, for whatever reason, and continuing on the remaining runway". This TOI was adopted as a ‘Supplementary Instruction’ with effect from 1 December 2018 with the intention that it would be added to the MATS Part 2 when that publication was next revised.
Previously Recorded Similar Occurrences
It was found that in the twelve months prior to the event being investigated, three other runway incursion events involving vehicles had been recorded, one of which in November 2017 had involved a runway lighting inspection and had involved an operations vehicle being on the upwind runway threshold as an aircraft had touched down. It was found that the subsequent internal incident report produced by the airport operations department had highlighted issues including inspection runs “being done at excessive speed (in excess of 70 mph), poor communications between the airport operations staff and ATC and ATC clearances including phrases such as ‘as fast as possible’ and ‘as quick as you can’”. This report found that the immediate cause of the incident had been the inspection being performed “with the next arrival in mind rather than the task at hand”. It also recommended “a review of the way runway lighting inspections were performed and a review of the risk assessments for all runway inspections and operations”, neither of which had been completed prior to the occurrence of the 3 February 2018 event.
The effectiveness of CAA regulatory oversight at Gatwick in respect of operational safety risk was reviewed by the Investigation and evidence was found that it was likely to have been compromised by a high Inspector workload. The reliance of busy Inspectors unable to attend relevant meetings at the airport on staying abreast of issues by “receiving and reviewing copies of the relevant meeting minutes” was found to be problematic since “the standard of the minutes did not always allow a proper understanding of the items discussed or the outcomes agreed”. It was observed that whilst the annual CAA audit “did identify and address relevant issues relating to ATC and runway inspections, the latter were identified only after the investigated incident had occurred (and that) it remains important to ensure individual airport Inspector workload is commensurate with providing adequate oversight of a major complex airport”.
The Overall Airport Context for the Investigated Event
The way in which the various parties within the airport operator and the ANSP dealt with runway safety issues and in particular the runway incursion risk was examined by the Investigation in some detail. One finding was that ATC management seemed to think that at least pilots based at Gatwick (the Aer Lingus crew involved in the event under investigation were not) would be “aware of runway inspection procedures” whereas this was confirmed by senior pilot managers from two Gatwick-based airlines to be wrong. These managers also stated that “they would not consider it acceptable for vehicles to enter a runway ahead of an aircraft until the aircraft was physically vacating the runway (and) pointed out that although a crew may have nominated the exit they would be using and may appear to be turning off the runway, they may (still) choose to continue past the exit at any time due to a technical failure or operational issue”.
The assembled evidence on runway inspections which had to be carried out in a demanding operational environment was considered to indicate “a lack of understanding” of how the airport operator and ANSPs work impacted airport users and “had potentially normalised procedures that would otherwise have been considered undesirable or at worst unacceptable”. Both organisations’ internal investigations of the 3 February 2018 event had been “triggered by the pilot declaring his intention to file a safety report” and both “saw nothing wrong in what happened” in direct contrast to the opinions of both the airline involved and other airline operators. The ATC report considered that the aircraft had been “committed” to vacating at the intended RET but failed to consider the fact “the aircraft appeared to be still on the centreline at the time the instructions were issued to the operations vehicle, the speed of the aircraft, the wet state of the runway and the implications had the aircraft, for whatever reason, needed to continue on the runway past the RET”. It was noted too that “there was also no apparent understanding of the potential distraction caused by asking the crew questions at a time of high workload”. It was considered that the assumption by the controller involved - which was supported by ANSP management - that the landing aircraft had been re-cleared to proceed no further than the second RET was “not clearly in accordance with any recognised ATC procedure”.
It was noted that a new runway inspection SOP became operational in January 2019 but that “it still does not include details on the direction (in which) runway inspections are to be performed (and) also requires lighting inspections to be done with the driver looking forward and the additional vehicle occupant having to look behind the vehicle”. This new SOP also now includes a requirement that “vehicles should not enter the runway ahead of a landing aircraft until the aircraft has fully committed to the exit” but does not say that this is irrespective of any ATC clearance issued and fails to define what “fully committed to the exit” actually means.
The formally documented Conclusion of the Investigation was as follows:
Gatwick Airport operates at high intensity to maximise the use of its single runway. This demands that airport operations, ATC and aircraft all operate as efficiently as possible if the declared runway capacity is to be attained. This capacity is not imposed but is set by the airport itself.
In setting the capacity it is important to balance maximising the number of aircraft operating to the airport with the safety of the operation itself. This Investigation indicates that the pressure of meeting the operating targets has had a direct effect on undertaking runway inspections both safely and effectively.
Many of the measures taken to redress the issues outlined in this report have yet to be completed and continued oversight and regular reviews in this area at all levels should be maintained.
One Safety Recommendation was made as a result of the Investigation as follows:
- that Air Navigation Solutions Ltd amend the wording of the Gatwick Airport Manual of Air Traffic Services Part 2, Chapter 10 and Supplementary Instruction 021 to specify how an aircraft is determined to have fully committed to vacating the runway, and ensure a vehicle cannot be cleared onto the runway ahead of an aircraft until the aircraft has done so. [2019-003]
The Final Report of the Investigation was published on 22 August 2019.