Norwegian B38M at Helsinki on Jan 18th 2019, touched down despite go around instruction
Last Update: December 19, 2019 / 19:12:00 GMT/Zulu time
Date of incident
Jan 18, 2019
ICAO Type Designator
Airport ICAO Code
A Turkish Airlines Boeing 737-900, registration TC-JYH performing flight TK-1769 from Istanbul (Turkey) to Helsinki (Finland), had landed on runway 22L just prior to the Norwegian and was slow to vacate the runway. At the time tower instructed the go around the Turkish was just about to turn off the runway, by the time the Norwegian touched down the Turkish was already on the high speed turn off ZJ but had not yet crossed the hold short line. The Norwegian was able to vacate the runway via high speed turn off ZJ, too.
Finland's Onnettomuustutkintakeskus (AIBF) reported, they have opened an investigation into the occurrence when an airliner landed on the runway that was still occupied by a previously landed airliner. A AIBF spokesman later added the Norwegian did not react to a tower instruction in this situation.
On Jan 19th 2019 Finland's ANS (ATC provider) reported the Turkish B739 was already vacating the runway hence, according to the ATC manuals, it was permitted to issue a landing clearance. However, the B739 slowed unexpectedly - but did not stop - prompting the controller to call the Norwegian to go around twice. Although the Norwegian continued for landing, there was no real danger as there was sufficient distance between the two aircraft.
On Jan 19th 2019 the AIBF indicated that important data were lost due to late notification of the event to the AIBF. The Turkish B739 had already departed to Istanbul when the AIBF received notification, the CVR recordings therefore are most likely lost though an attempt is being made to read the CVR out in Istanbul.
On Dec 19th 2019 the AIBF released their final report concluding the probable causes of the serious incident were:
1. ATC cleared a transport category airplane to land although the preceding transport category airplane had not vacated the runway. The controller issued the landing clearance since there was reasonable assurance that prescribed separation would exist when the airplane arrived at the threshold.
Conclusion: The principle of reasonable assurance is recognized internationally, and its purpose is to enable the efficient use of runway capacity. If the situation changes, safety will be ensured by canceling the landing clearance. This instruction shall be transmitted in a timely manner to allow time for its execution.
2. After issuing the clearance, the controller focused on two airplanes that were crossing the runway and therefore paid little attention to the airplane that was vacating the runway.
Conclusion: Runway crossings affect tower operations at Helsinki-Vantaa airport in several ways and may result in the breakdown of deconfliction. Controllers should be aware of the associated risks and assume a proactive stance to the problem during all work shifts.
3. The controller noted that the preceding landed airplane had slowed down significantly and could even be stationary on the taxiway.
Conclusion: There can be a multitude of justified reasons for slower-than-normal taxi, such as procedures at an unfamiliar airport, winter conditions, or waiting for a taxi clearance or a follow me car. The traffic situation and prevailing conditions may change abruptly, in which case ATC will need to decide quickly whether the conditions of a landing clearance continue to exist, or should the succeeding airplane be directed to go around.
4. The controller delayed the go-around instruction until the airplane had crossed the threshold. The automated callout system was calling radio altimeter heights. The goaround instruction, delivered in a normal tone and comprising a single message, was masked by the 50, 40, and 30 ft callouts.
Conclusion: Controllers shall be sufficiently conversant with flight crew activities and the sound environment in the flight deck during various phases of the flight. Sometimes the controller may need to transmit an urgent instruction (such as a goaround call) to ensure safety in an evolving situation. These calls shall be readily distinguishable among other radio communications in terms of both tone and volume.
5. The ATCOH guidelines and definitions pertaining to runway vacation after landing are interpreted inconsistently among the Finnish controller community.
Conclusion: An underlying safety management principle is that actions shall not contradict rules and regulations. Either the actions and procedures shall be aligned with internationally recognized regulations, or the Finnish interpretation – that in this case offers a wider safety margin – shall be endorsed and incorporated in aerodrome-specific publications.
The AIBF analysed the occurrence happened during the hours of darkness in clear skies with visibility above 10km. Runway 22L had been cleared of snow to a width of 54m, 20cm high snow banks were at both sides of the cleared area.
The AIBF analysed the situation in the cockpit of D8-351: "Flight IBK351’s cockpit voice recorder data revealed that during the approach briefing both crewmembers stated that they felt a little bit tired after a long day. Saying this aloud showed that they recognized the associated risks and a need for heightened attention. The briefing also included a missed approach procedure."
The AIBF analysed the actions of TK-1769 after touch down: "They slowed down the airplane significantly during rollout and then proceeded along the exit taxiway at a slow speed. The captain explained in a written statement that vacating the runway at a higher speed would have been risky due to the reported taxiway friction."
The AIBF reported the situation in the cockpit of D8-351 during final approach:
During the approach and landing, the first officer and captain exercised the duties of PF and PNF, respectively. They adhered to the sterile cockpit procedure during the approach by engaging only in conversations needed for the operation of the airplane. Their actions were also in all other respects compliant with the standard operating procedures.
During the final approach, they watched the two SAS airplanes that were crossing the runway and maintained awareness of THY1XE as it was vacating the runway. They considered the runway clear since the SAS airplanes had crossed the runway and THY1XE was on the taxiway outside the 60 m wide runway. They found these observations consistent with the landing clearance they had just received and felt they could concentrate on landing without distractions.
Up to the receipt of a landing clearance, pilots are “go-around minded,” and their mindset is tuned to the continuation of the flight; after they are cleared to land, their attention shifts to landing the airplane and they become “landing minded.” In this particular incident, the airplane had been cleared to land, and neither communications with ATC nor the pilots’ own observations gave them any reason to expect an instruction to go around.
Since a go-around call is rarely transmitted when the airplane is already over the threshold, pilots do not anticipate such an instruction unless the controller has advised them to expect a late landing clearance or the pilots themselves have recognized the possibility of a go-around based on their observations of weather or an unusual traffic situation or for some other reason. When over the threshold, the pilots concentrate on landing since the airplane is only dozens of feet above the ground and touchdown will happen in a matter of seconds.
In the flight deck of IBK351, the entire go-around instruction consisting of the flight’s call sign and the two-part message was masked by automated callouts that alerted the pilots of the passing of 50, 40, and 30 ft of altitude.
The AIBF reported the tower actions:
The controller cleared IBK351 to land on the still occupied runway 22L since it could be expected with reasonable accuracy that adequate separation10 would exist when the airplane arrived at the threshold. The purpose of the principle of reasonable accuracy is to enable the most efficient use of runway capacity, and it involves a built-in option to cancel the landing clearance and instruct the airplane to go around if the runway remains occupied.
Another option is to first notify the crew that a landing clearance will be issued later (by transmitting “expect late landing clearance” or describing the situation by transmitting, e.g., “continue approach, another 737 vacating”); in these cases a landing clearance will be granted after the controller has determined that the runway is clear. This option also enables the crew to anticipate a go-around – which they shall execute autonomously unless they receive an explicit landing clearance.
In this particular case, the controller had cleared the SAS airplanes to cross active runway 22L after THY1XE had landed. The SAS airplanes were essential traffic from the controller’s point of view because the controller had to ensure that they exited the runway.
The location of the SAS airplanes and THY1XE posed a visual observation problem due to their angular displacement of approximately 90o, and this displacement increased further as THY1XE was turning onto the taxiway. During the interview, the controller described its position by stating, “it was there… off to one side.” The controllers were at the time of the incident unable to determine whether THY1XE was stationary or in motion, and they explained that several other controllers at the tower had thought it had come to a halt.
Tower controllers monitor traffic continuously and estimate runway occupancy times using the average turnoff speed of different airplanes as a yardstick. Airplanes that had landed before and after THY1XE had turned off and proceeded along the taxiway at speeds approximately twice as high as THY1XE.
From the aspect of cognitive ergonomics, an air traffic controller’s job is an example of autonomously conducted safety-critical work. Even though an ATC facility is constantly manned by several persons, they are assigned different tasks, and therefore an individual controller will often need to make operational decisions quickly and assume full responsibility for his or her actions. Unlike the flight crew of a transport category airplane, who share tasks between the PF and PNF, tower controllers do not establish the roles of a ‘controlling controller’ and ‘monitoring controller.’
This particular incident was, however, an exception as one of the two controllers involved had been recently transferred to Helsinki-Vantaa and was paired with an instructor at the TWR-E position. The controller had begun site-specific training in a simulator covering, among other topics, the airport’s runway usage, low-visibility procedures, and a range of contingencies such as go-arounds and full emergency procedures. The next phase included 45 shifts of actual controlling at the tower under the supervision of an instructor controller. The first shifts during site-specific training are scheduled for periods of low traffic intensity, and the trainee then progresses to handle more intensive traffic situations. Training is based on the learning-by-doing principle, in which the instructor guides the trainee and assists him or her as required. During site-specific training, and often during any particular shift, the trainee is rotated between all control positions (TWR-E, TWR-W, GND-1, and GND-2) in order to instruct him or her in the specifics of each position in a time-efficient manner.
In this particular incident, both the trainee – who was communicating with the airplanes – and the instructor were experienced controllers. They held valid licenses and ratings, and the instructor had a valid instructor’s endorsement obtained during a training instructor course at Avia College. Their previous shift had ended the night before at 0100 h and they reported again for duty at 1130 h on the day of the incident. They began the shift at the TWR-E position and then moved to the GND-2 position for a total of four hours (2 x 2 h) before relocating to TWR-E at 1700 h. The scheduling of breaks during the day had been in accordance with regulations, as the team had taken two thirty-minute breaks before the incident, and continuous time on task had not exceeded two hours.
Upon recognizing the possibility of a runway incursion, the instructor immediately prompted the trainee to transmit a go-around call, and the trainee concurred and complied. Any training situation is characteristically based on the ‘play it safe principle.’ In this incident, the trainee controller would in all probability have told IBK351 to go around even though the controller had been solely responsible for the control position.
The controller inserted the phrase I say again into the message, and the structure and phrasing of the message were correct in all respects. When passing the go-around instruction, the controller maintained the tone and pitch of speech that the controller had used in preceding communications.
During the interviews, the controllers mused on the reasons why the crew had disregarded the go-around call and wondered whether it had been masked by a transmission from another aircraft but rejected this theory after listening to the recordings. The conclusion of the interviews was that the controllers did not understand what had happened in IBK351’s flight deck. Their view was purely technical and experience-based; it did not demonstrate an understanding of factors related to flight crew operation, human factors in play during the final approach and landing, or the impact of automated callouts in the flight deck.
With respect to the terminus runway vacated the AIBF reported:
The investigation revealed that the current instructions pertaining to the vacation of the runway after landing (see paragraph 2.7.1) are interpreted inconsistently.
The instructor controller used the phrases “coming on top of row of lights” and “getting past the lights in time” during the interview and referred several times to a condition of “being on the other side of the line.” The controller apparently thought that THY1XE had not yet crossed the holding position markings, which at Helsinki-Vantaa (for CAT I–III) are 90 m from the runway centerline and 60 m from the runway edge (in accordance with aviation regulation AGA M3-5). The investigation found this notion prevalent in the controller community.
On the other hand, a controllers’ representative mentioned in a media interview that THY1XE had not proceeded a sufficient distance from the runway, and said, “there is a technically defined limit of 50 meters from the runway edge.”
ANS Finland’s Air Traffic Control Officer's Handbook (ATCOH) contains two definitions that are applicable to a situation where a preceding airplane is vacating the runway after landing, and one of them includes the foregoing distance of 50 m. The other option is a case where the preceding airplane has turned off and is moving away from the runway (see paragraph 2.7.1).
Due to the emergence of different interpretations, SIAF inquired ANS Finland about its views on the interpretation of the options laid down in the ATCOH. ANS Finland responded in writing that “one of the two conditions shall be met.” This means that the preceding airplane [even though stationary] shall be no closer than 50 m to the runway or it shall have turned off and be continuously in motion away from the runway.
The ATCOH (see paragraph 2.7.1) states that an airplane may be cleared to land on an occupied runway when there is reasonable assurance that the runway is clear no later than the point in time when the airplane crosses the threshold. In the interests of safety, a goaround call will be transmitted if required. The investigation revealed that risks resulting from the issuance of a landing clearance on an occupied runway and its consequences have not been assessed by the authorities or operational-level organizations, and parameters (such as weather, friction, lighting, and other conditions) for reasonable assurance have not been established. The safe application of the principle of reasonable assurance therefore hinges on appropriate action by controllers exercising operational responsibility.
The AIBF analysed the occurrence:
The landing airplane did not execute a go-around; it landed normally and vacated the runway along the same taxiway as the preceding landed airplane.
The most significant anomaly was the failure to execute a go-around despite the controller’s instruction. There was no collision potential due to sufficient safety margins embedded in the applicable procedures.
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Date of incident
Jan 18, 2019
ICAO Type Designator
Airport ICAO Code
This article is published under license from Avherald.com. © of text by Avherald.com.
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