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Incident: Finnair A319 at Helsinki on Oct 28th 2016, crew corrects ATC mistake
By Simon Hradecky, created Thursday, Dec 15th 2016 18:56Z, last updated Thursday, Jun 29th 2017 16:01Z
A Finnair Airbus A319-100, registration OH-LVD performing flight AY-933 from Helsinki (Finland) to Manchester,EN (UK), was taxiing for departure from runway 22R.
A SAS Scandinavian Airlines Canadair CRJ-900, registration OY-KFB performing flight SK-1706 from Copenhagen (Denmark) to Helsinki (Finland), was on final approach to Helsinki’s runway 22L cleared to land on the runway, when the crew of the A319 received clearance to cross runway 22L. The A319 crew spotted the CRJ on short final and stopped before crossing the hold short line.
Finland’s Onnettomuustutkintakeskus (Accident Investigation Board AIBF) rated the occurrence a serious incident and opened an investigation. Denmark’s HCL have assigned an accredited representative to the investigation.
On Jun 29th 2017 the AIBF released their final report in Finnish releasing following findings into the serious incident:
Helsinki Airport had set runway 22L for arrivals and runway 22R for departures in a lively traffic situation. This meant, due to the location of the terminals, that departing aircraft had to cross runway 22L to reach runway 22R.
The aerodrome chart shows the runway crossing points as “hot spots” instruction flight crew to exercise special attention while moving in these areas. The last safety assessment had occurred in 2002, another safety assessment was necessary.
The tower controller, while following the landing traffic, issued staggered crossing clearances behind landing traffic. The attention by the tower controller may be disturbed by outside coordination line calls particularly during busy periods of time.
SK-1706 was already in the roll out on runway 22L and AY-933 was nearing the hold short line at ZG (taxiway G) requesting to cross the runway. The tower controller cleared AY-933 to cross runway 22L although SK-1706 had not yet passed the intersection with taxiway G. There is no safety net available that could alert the controller of an error early.
The tower controller sought to provide a quick service while controlling aircraft and made a mistake in mistaking on which taxiway AY-933 would cross the runway.
The flight crew of AY-933 made their position clear by reporting to be at ZG, the controller however did not take notice of the position ZG and assumed the aircraft was on ZD. Following the incident the standard operating procedures at Helsinki were changed requiring controllers to always spell out the taxiway at which the aircraft were cleared to cross the runway.
The tower controller relied on his vision and did not cross check the position on the traffic management systems prior to issuing the crossing clearance. Helsinki Airport does provide assistance to air traffic control with a ground position and monitoring system, electronic flight strips as well as stop lights. A warning system based on cooperation between those systems is not operative.
The crew of AY-933 found the runway was not clear and queried tower to verify the clearance. Flight crew being obliged to verify the runway is clear provide an additional safety net in case of error by tower.
In accordance with the instructions issued the stop bar lights were extinguished at holding points ZD and ZG. Their use is coupled to the tower instructions to ensure the stop lights are not illuminated in places were crossing clearance just past a landing traffic occur repeatedly. Further development and integration with other systems would be possible and provide an additional safety net.
The controller made an according exeception report to Finavia.
The controller was properly licensed and held the necessary medical certicate. The skill and health of air traffic controllers are regularly monitored.
Finavia has been active in training of human factors related to air traffic control. In recent years emphasis was put on changes due to technical gravity. At the level of the European Union importance of human factors is increasingly emphasized. Eurocontrol has identified human activity as a key success factor in aviation safety management.
Air Traffic Controller, Air Traffic Control Superiors, the Risk Management Unit as well as the crew of AY-933 did not consider the occurrence a serious incident, however, the investigation considered the occurrence a serious incident. Definition of a serious incident varies with EU regulations, ICAO runway safety and Eurocontrol runway safety action plans.
The AIBF reported that one aircraft was approaching the hold short point ZY on taxiway Y, two in a row (AY-841 being the second aircraft) were approaching the hold short point ZD on taxiway D. The controller issued the landing clearance to SK-1706. The first aircraft on taxiway D was given a conditional crossing clearance to cross past the landing traffic.
A short time later AY-933, after SK-1706 had touched down and was rolling past the intersection with taxiway D but ahead of the intersection with taxiway G, reported approaching holding point ZG, the controller cleared the aircraft to cross runway 22L and hold short of holding point WD (holding point on taxiway D ahead of runway 22R) suggesting the controller believed the aircraft was on taxiway D (instead of G). The flight crew of AY-933 noticed the runway was not clear, queried tower and stopped short of ZG.
The AIBF analysed that although lively the traffic scenario at Helsinki was a normal morning in good visibility. Runway 22L was used for arrivals, runway 22R for departures. Three runway 22L crossing points were in use to permit departing aircraft reach runway 22R, on each of the crossing points multiple aircraft could have been waiting for crossing. In an attempt to permit as many aircraft cross the runway as possible before the next landing would block the runway, air traffic control issued crossing clearance as soon as the landing traffic had gone past the relevant taxiway (staggered crossing clearance) or used conditional crossing clearance past the landing traffic.
At the time of the occurrence four aircraft were waiting to cross runway 22L. The first two received conditional crossing clearances (past the landing traffic), the third however mistakenly received a crossing clearance despite still being ahead of the landing traffic because the controller confused the taxiway the aircraft was on. This confusion was probably caused by AY-841, behind the first aircraft waiting at ZD, approaching holding point ZD at the same time as AY-933 approached ZG, the controller thus assumed the aircraft on ZD was calling and as the landing traffic had already gone past taxiway D cleared the caller to cross the runway. However, the crew had indicated they were approaching ZG, but this did not change the controller’s perceiption, who also reasoned that the first aircraft at ZD had already received a conditional crossing clearance and overtaking was not possible.
Immediately after issuing the crossing clearance the controller recognized his mistake and wanted to correct the mistake, however, the crew was already calling to query the crossing clearance. The controller in response corrected the mistake. The AIBF pointed out that in such a scenario a risk of radio traffic congestion exists that could prevent correcting such a mistake.
In this case the safety net via the flight crew worked, flight crew are obliged to verify the runway is clear prior to entering the runway and the flight crew did not cross the hold short line although cleared to do so.
The controller was experienced and quick in decision making. Visibility was good. The controller was therefore relying on his vision and on the image of aircraft rolling. The strong impression of the rolling aircraft on D caused the controller to not take into account, that the crew was reporting to be taxiway G. In this traffic situation the position report by the aircraft was insufficient. Air Traffic Control not only requires technical know how but also the capability of demanding data processing and decision making. The aim is to proactively control aircraft so that surprises do not occur. Maintaining situational awareness is essential for safety, however, it is also essential for air traffic control to accelerate traffic. For aircraft taxiing flexibility and speed using contingent runway crossing clearances appear to be the unofficial practice with the aim to avoid stops during taxi.
The controller had arrived for work at 07:00. At 08:50 she had been working for over an hour in busy traffic and was soon to be relieved for a rest. It is possible that the nearing rest period influenced concentration momentarily. In addition three calls to coordinate the launch of weather balloons, unrelated to the controller’s main task, were handled by the controller in an already busy period of time. Although those calls did not have any direct impact on the occurrence, they might affect the controller’s concentration.
The AIBF then analysed the possibility of creating additional safety nets by improved stop bar lighting, introduction of a runway incursion detection system and the safety management in general.
The AIBF analysed that about three weeks after the occurrence the standard operating procedures were changed to require air traffic controllers including the taxiway in runway crossing clearances.