B738 / Vehicle, Kansai Japan, 2023

B738 / Vehicle, Kansai Japan, 2023

Summary

On 20 July 2023, a Boeing 737-800 was given a night landing clearance at Kansai with the controller unaware a runway inspection in the landing direction was in progress. When the vehicle driver heard this clearance, they identified the approaching aircraft position and estimated their inspection could be completed without impeding the inbound aircraft but on checking, were instructed to exit the runway at once and did so. Minimum aircraft/vehicle separation was 3,480 metres. The immediate cause of the potential conflict was controller error when various ground movement activities were occurring towards the end of an otherwise quiet night shift.

Event Details
When
20/07/2023
Event Type
HF, RI
Day/Night
Night
Flight Conditions
VMC
Flight Details
Type of Flight
Public Transport (Passenger)
Intended Destination
Take-off Commenced
Yes
Flight Airborne
Yes
Flight Completed
Yes
Phase of Flight
Landing
Location - Airport
Airport
General
Tag(s)
Inadequate ATC Procedures
HF
Tag(s)
ATC clearance error
GND
Tag(s)
Aircraft / Vehicle conflict, ATC clearance error, Maintenance work in progress
RI
Tag(s)
ATC error, R/T Response to Conflict, No Single Runway Occupancy Frequency
Outcome
Damage or injury
No
Non-aircraft damage
No
Non-occupant Casualties
No
Off Airport Landing
No
Ditching
No
Causal Factor Group(s)
Group(s)
Air Traffic Management
Safety Recommendation(s)
Group(s)
None Made
Investigation Type
Type
Independent

Description

On 20 July 2023, a Boeing 737-800 (B-5156) being operated by China Postal Airlines on a scheduled international cargo flight from Shanghai Pudong to Kansai as CF205 was cleared to land in night VMC despite the fact that, unknown to the TWR controller issuing the clearance, a routine inspection of the landing runway was still in progress with the vehicle concerned travelling in the landing direction whilst working the GND frequency rather than the TWR frequency in accordance with local airport procedures. The conflict was only resolved when the vehicle driver involved persisted in challenging the GND controller who then recognised he had confused two different mobiles.

Investigation 

A Serious Incident Investigation was carried out by the Japan Transport Safety Board (JTSB). Recorded ATC communications including phone calls were available as was data from the ‘drive recorder’ installed in the runway inspection vehicle. Historic aircraft position data was available from the airport MLAT system but this did not cover airside vehicles, even those permitted to operate on an active runway when so cleared.

The 43 year-old TWR controller had been position-qualified for in excess of 14 years and the 43 year-old GND controller had been position-qualified for in excess of 20 years. A third controller in the ‘Co-ordinator’ position played no part in the investigated event and their experience was not recorded. The GND controller was designated as the shift leader. The rather unusual ATC practice at Kansai involved vehicles remaining on the GND frequency even when cleared to operate on an active runway despite the fact that such vehicles were not included in the airport MLAT system so whilst TWR controllers could see the precise location of aircraft on the runway, mobiles could only be located visually. This unusual GND/TWR arrangement turned out to be of considerable relevance to the event under investigation.

What Happened

The airport night shift controller team, which consisted of three controllers as described above, had begun their shift at 1930L but did not begin to work in position until “about 2100L” in the case of the TWR and GND controllers and “from about 2140L” for the Co-ordinator position. The team were “relieved for rest or other duties” and left the TWR control room at “about 0030L” and did not return until “about 0520L”. A runway inspection of the active runway, 06L/24R with 06L in use, had been commenced at 0444L by a vehicle using the callsign Operations 4 and a similar inspection of parallel runway 06R/24L, which was designated as closed for maintenance throughout the time when the investigated event occurred, had subsequently commenced at 0515 by a vehicle using the callsign Operations 3. The former inspection was paused to allow an aircraft to land at 0528L and then resumed.

The China Post Boeing 737 took off from Shanghai Pudong for what is typically a 2½ hour flight to Kansai at 0353 and whilst working Kansai Approach requested and was cleared for an ILS approach to runway 06L at 0528 and was then transferred to TWR and checked in there 3 minutes later when on final approach and approximately 10 nm from the runway. Shortly after this, the driver of the vehicle doing the closed runway (06R/24L) inspection called GND using its callsign ‘Operations 3’ and when told to “go ahead” had advised “vacated runway A” and given its position. (Note that ‘Runway A’ was the normal GND description of runway 06R/24L, whilst the description ‘runway B’ was used by GND to refer to runway 06L/24R.)

Despite hearing the driver’s initial call, the GND controller thought that it was Operations 4 which had called and stated that despite responding to the initial call with “Operations 3, go ahead”, when hearing the word “Operations”, he had “thought reflexively that Operations 4 had called and had thus looked toward the active runway”. Operations 3 then called saying “Vacated Runway A” and gave its current position. Thinking that Operations 4 had vacated Runway B after completing its runway inspection, the GND controller read back only "Roger, vacated runway".

When looking back toward the GND controller in order to coordinate with Operations 4 to vacate the active runway for the approaching 737, the TWR controller heard the call from Operations 3 about vacating the runway over the speaker, but did not recognise which inspection vehicle the report came from. The Co-ordinating controller also heard the report through the speaker that a vehicle vacated a runway, but did not recognize which inspection vehicle it came from. However, since the GND controller had believed he had been talking to Operations 4, he immediately informed the TWR controller that the active runway was clear. Although the TWR controller was unable to visually confirm that Operations 4 had vacated the active runway, he could not see where he had most recently seen it near the runway 16L threshold and therefore issued a landing clearance to the 737.

Meanwhile, Operations 3 requested permission from GND to begin inspecting the closed runway’s parallel taxiway and received the response to “hold as there was an arriving aircraft”. When the TWR controller issued the landing clearance, Operations 4 was continuing his inspection of the active runway in the same direction as the aircraft landing direction. Operations 4 thought the GND controller’s holding instruction to Operations 3 was odd and decided to confirm the range of the inbound aircraft with a “mobile device” and could see that an aircraft was on approach to the same runway he was driving on. He provisionally assessed that there would probably be enough time to complete the run he was doing but decided to contact the GND controller to find out whether he should vacate the runway or continue the inspection run. The GND controller, perceiving that this call had come from Operations 3 replied he did not need to vacate the runway. Having received this reply, Operations 4 tried again and this time, the GND controller “noticed” the call was from Operations 4 and instructed it to vacate the runway from its present position which it then did.

Having instructed Operations 4 to vacate the runway, the GND controller immediately informed the TWR controller that it might be still on the runway. The TWR controller checked the active runway visually and saw that Operations 4 was about to vacate the runway at taxiway B10, which was approximately 2,300 metres from the landing threshold of the 3,500 metre-long active runway. Having visually confirmed the position of the approaching aircraft as well, he judged that there was no need to instruct the aircraft to execute a go-around and it subsequently touched down without either pilot seeing the inspection vehicle on the runway.

Why It Happened

The whole event occurred because of the GND controller’s error in not ensuring that the identity of a vehicle was recognised when only two vehicles had been given permission to enter two different runways. The fact that this error continued to be made in subsequent communications until the driver of the vehicle cleared to inspect the active runway challenged the GND controller about clearing the runway meant that recognition of the conflict was delayed such that it was not far from creating a significant potential for collision.

The Probable Cause of the Accident was recorded as “whilst the vehicle was conducting a scheduled inspection on the only active runway with entry permission, the Tower cleared an aircraft to land on the same runway, therefore that aircraft flight crew, who had not detected a vehicle on the runway, continued their approach and landed”.

Contributing to the issue of conflicting clearances was:

  1. The fact that the Tower Controller was told by the Ground Controller, who was responsible for vehicle movements on both the active and closed runways, that the active runway was clear of vehicular traffic when this was not the case and the Tower Controller did not then visually detect the presence of the inspection vehicle on the active runway. 
  2. The Ground Controller mistook a report of vacating the runway from a vehicle which had been on the closed runway for one from the inspection vehicle which was on the active runway and therefore incorrectly told the Tower Controller that the runway was clear of vehicles. The Ground Controller also failed to fully readback a correctly given report from the vehicle which announced it had vacated the closed runway.

Safety Action as a result of the investigated event was note to have included the following:

The Kansai ANSP required that: 

  • All instructions, responses and co-ordinations with regards to vehicles shall include the runway designator and the taxiway designator. 
  • TWR Controllers shall confirm the position of a vehicle when it enters or vacates the runway. 
  • When there is an arriving aircraft, in principle, the vehicle shall be vacated from the runway before the arriving aircraft passes the point at 10 nm from the runway threshold.

The Air Traffic Services Department of the Japan Civil Aviation Bureau required all facilities providing aerodrome control services to take the following measures by November 30, 2023:

  • When permitting inspection vehicles and others to enter or vacate an active runway or helipad or when instructing them to vacate the same and subsequently confirming this, the applicable ATC procedures shall specify the communication format so that misidentification is prevented. 

The closest distance between the aircraft on approach and the inspection vehicle was assessed as having been “approximately 3,480 metres” which would have placed the 737 about 1,500 metres (20 seconds) from touchdown. However, although it was assessed by the Investigation that the conflict had been a ‘Serious Incident’, it was determined that the appropriate ICAO Runway Incursion Severity Scheme Classification was ‘C’ which is defined as “an incident characterised by ample time and/or distance to avoid a collision”.

The Final Report was adopted by the JTSB on 7 June 2024 and subsequently published simultaneously in both the definitive Japanese language version and in an English language translation on 27 June 2024. No Safety Recommendations were made.

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