Backgrounder

TSB recommendations to address the risk of runway incursions

Risk of collisions on runways between the parallel runways on the south complex of Toronto/Lester B. Pearson International Airport (A17O0038)

The Transportation Safety Board of Canada (TSB) has identified the risk of collisions on runways as a serious risk in the Canadian aviation sector; this issue has persisted on the TSB’s Watchlist since 2010. Despite the efforts of government and the air industry, the risk of collisions on runways that results specifically from runway incursions remains a significant concern.

As a result of a number of runway incursions at Toronto/Lester B. Pearson International Airport (CYYZ), the TSB launched a safety issue investigation to examine the circumstances in more detail. This report contains the results of the investigation into 27 similar runway incursions that occurred on the south runway complex at CYYZ between June 2012 and November 2017. These were not the only incursions during this time at CYYZ; however, they posed substantial risk and shared many characteristics. All of the incursions involved aircraft that had landed on the outer runway and, despite receiving instructions from air traffic control and intending to hold short of the inner runway, did not do so.

TSB recommendations

The Canadian Transportation Accident Investigation and Safety Board Act specifically provides for the Board to make recommendations to address systemic safety deficiencies posing significant risks to the transportation system and, therefore, warranting the attention of regulators and industry. Under the Act, federal ministers must formally respond to TSB recommendations within 90 days and explain how they have addressed or will address the safety deficiencies.

Recommendations made on 31 January 2019

Phraseology for use in safety-critical scenarios

Over the past 5 years, the TSB has investigated 3 events in Ontario^{Footnote 1}—including one of the incursions detailed in this report—in which air traffic control (ATC) instructions issued to flight crews to address a conflict were not recognized or acted on. When ATC recognize a conflict between aircraft or vehicles, they must issue prompt instructions to resolve the conflict. These instructions need to be recognized and understood by the intended recipients so that the safest course of action can be taken. If these instructions are not actioned, there is a risk that the conflict may result in a collision.

The current guidance provided to air traffic controllers in Canada with respect to the phraseology in safety-critical situations is different from international guidance. It does not prescribe any attention-getting enhancements, such as using the word “immediately” or repeating the instruction. Without these enhancements, the instruction may not be compelling enough to attract the intended recipient's attention, and, as the phraseology may be different from what flight crews are expecting, there is a risk that the instruction will not be immediately understood, particularly during periods of high workload.

Therefore, the Board recommends that

Timing of post-landing procedures

Once an aircraft has landed on a runway and the landing roll is complete, the flight crew must perform a series of post-landing tasks. As detailed in this investigation, during normal operations, most flight crews begin these tasks when the aircraft is clear of the landing runway, in accordance with their operator’s standard operating procedures (SOPs). These tasks, or checklists, are usually brief and occupy only a small amount of one or both of the flight crew members’ attention.

At airports that have closely spaced parallel runways, aircraft that have landed on the outer runway normally exit the runway via a rapid exit taxiway, which sometimes terminates directly on the inner runway. In most cases, ATC will instruct flight crews to hold short of this runway because the runway is in use by other departing or arriving traffic. In these cases, it is essential that, immediately after exiting the landing runway, flight crews focus their attention on acquiring the visual cues necessary to identify the runway holding position in order to prevent the aircraft from incurring on the other active runway.

Most operators’ SOPs require that the post-landing checks be conducted once the aircraft is clear of the landing runway. However, as shown in this investigation, if these SOPs are followed when flight crews are operating on closely spaced parallel runways, they may focus their attention inside the cockpit at a time when their full attention and visual focus are required outside, and flight crews may miss the visual cues and incur on the active runway as a result of this distraction.

In 2012, the U.S. Federal Aviation Administration (FAA) published guidance for operators to help them develop and implement SOPs to prevent runway incursions. Although this guidance advises flight crews to initiate non-essential post-landing actions—such as raising flaps or adjusting trim—after the aircraft is clear of all active runways, it does not propose any specific amendments to post-landing SOPs that reflect this advice. None of the operators involved in the occurrences studied had incorporated any changes to their post-landing SOPs to address this concern.

Therefore, the Board recommends that

The Board also recommends that

Taxiway design and conspicuity

The taxiway layout between the closely spaced parallel runways at Toronto/Lester B. Pearson International Airport (CYYZ) has several characteristics that are uncommon when compared with those at other airports, both within North America and globally. The runways are spaced a relatively short distance apart, and the rapid exit taxiways provide direct access to the adjacent runway without first progressing to another transitional surface. The runway holding positions are located immediately following a 65° curve and are situated at greater distances from the protected inner runway than is seen elsewhere.

These uncommon characteristics present significant challenges for flight crews. When exiting the landing runway, crews are normally occupied with other tasks and, because they are using a rapid exit taxiway, the aircraft is usually travelling at taxi speeds that are faster than typical. A flight crew’s unfamiliarity with these uncommon characteristics, the short amount of time and distance available, and distraction due to other tasks reduces their ability to identify the runway holding positions. As demonstrated by the occurrences covered in this investigation, if these positions are not identified, aircraft can incur on the other active runway and potentially collide with another aircraft.

International guidance recommends many strategies to address runway incursions. All but one of these have been implemented on the south complex at CYYZ; the remaining strategy is to make physical changes to the taxiway layout.

A change of this scale may be required to increase the distance and taxiing time between runway holding positions, to reduce the taxiing speeds of aircraft approaching the hold-short line, to prevent direct access to adjacent runways from rapid exit taxiways, and to re-situate visual cues in common locations. Among the possible reconfigurations that may address these factors is the inclusion of an intermediate parallel taxiway between the runways, as found at numerous other airports with parallel runways.

It is recognized, however, that a change this significant cannot be made overnight, and simpler incursion mitigation strategies may need to be implemented, or current strategies improved, in the meantime. Although much has been done over the past few years to improve the conspicuity of the runway holding positions, options still remain, such as altering the type, amount, or intensity of the runway holding position lighting, which may further improve the likelihood that flight crews identify the cues and stop before incurring on the runway.

Therefore, the Board recommends that