Canada E190 at Toronto on Jan 30th 2016, runway incursion
Last Update: May 24, 2017 / 14:55:26 GMT/Zulu time
An Air Canada Airbus A320-200, registration C-FZQS performing flight AC-1259 from Puerto Vallarta (Mexico) to Toronto,ON (Canada) with 148 people on board, was on short final to runway 24R when the crew initiated a go-around because of the runway incursion. The aircraft positioned for another approach and landed safely on runway 24R about 20 minutes later.
C-FNAW departed a few minutes later and reached New York on time without further incident.
The Canadian TSB reported the occurrence was rated a serious incident and is being investigated.
On May 24th 2017 the TSB released their final report concluding the probable causes of the serious incident were:
Findings as to causes and contributing factors
- The plain-language taxi instruction issued by the ground controller was misinterpreted by the flight crew, and the flight crew’s readback using the same phraseology was ineffective in confirming that the ground controller and the flight crew had a common understanding.
- Due to a misinterpretation of the taxi instruction, ACA726 taxied across the hold line and onto Runway 24R without an authorization from the airport controller to line up on the runway or take off.
- Given that the airport controller’s attention was directed toward the arriving aircraft, the controller did not detect ACA726 crossing the hold line and taxiing onto the runway.
- When the runway incursion monitoring and conflict alert system (RIMCAS) stage 1 visual alert displayed on the tower advanced surface movement guidance and control system (A-SMGCS) display, the airport controller’s attention was directed toward the aircraft on final approach, resulting in the stage 1 alert being undetected on the A-SMGCS display.
- Five seconds later, the RIMCAS stage 2 alarm sounded in the tower at the same time that the ACA1259 flight crew reported to the airport controller that there was an aircraft on the runway and that they were overshooting the runway. The RIMCAS stage 2 aural alarm did not provide a timely warning to the airport controller to provide alternate instructions to the flight crews.
Findings as to risk
- If air traffic controllers are not required to use standard phraseology that reinforces the need to hold short of a departure runway, there is an increased risk of miscommunication leading to runway incursions.
- If plain-language phraseology used by air traffic controllers is not explicit, there is a risk of miscommunication between air traffic control and flight crews.
- If airport lighting system stop bars are not illuminated at a hold line across a taxiway or in a holding bay leading to a departure runway and the RIMCAS stop bar overrun monitoring function is not used, there is an increased risk that an airport controller will not be alerted to an unauthorized movement of an aircraft or vehicle across a hold line.
- If required commuting flights are not included as part of the pilot’s duty day, there is an increased risk of pilots operating while fatigued due to prolonged periods of wakefulness.
The TSB analysed:
When the ACA726 flight crew contacted the ground controller, they had already completed their pre-departure preparations, including the pre-takeoff checks, as they anticipated arriving at the departure runway quickly. They confirmed with each other that everything was ready for departure before requesting taxi instructions from the ground controller, and expected to receive an authorization to take off shortly after they had started to taxi to the runway.
The crew’s expectation that they would quickly receive an authorization to take off was reinforced when the ground controller asked them whether they were “ready to go.”
After confirming that the ACA726 flight crew were ready to go, the ground controller replied with further instructions that they “go to the right side and eighteen thirty-five.” The flight crew interpreted this instruction as an authorization to go to the right runway (i.e., Runway 24R) and taxied to position on the runway in preparation for takeoff. This interpretation was consistent with their expectation of what would happen next according to their mental model of the situation.
Although there were available cues that could have alerted the flight crew to the misunderstanding, the cues were either not sufficiently compelling or were considered and explained away. The fact that the perceived instruction to enter the runway would not normally be received from a ground controller was not sufficiently compelling to cause the crew to question their understanding of the situation. Similarly, the aircraft on final approach was perceived by the flight crew to be on approach to the parallel runway.
Although the first officer (FO) read back the instructions, saying “over to the right side, eighteen thirty-five, thanks for the help,” the misunderstanding was not detected because the readback consisted of the same plain-language phraseology that had been used by the ground controller.
The plain-language taxi instruction issued by the ground controller was misinterpreted by the flight crew and the flight crew’s readback using the same phraseology was ineffective in confirming that the ground controller and the flight crew had a common understanding.
Use of the phrase “holding short” is optional when issuing instructions to taxi to the threshold of a departure runway. In this occurrence, the use of the phrase “contact tower holding short” at the end of the taxi instruction would have communicated to the crew that they were not authorized to enter the runway.
The phrase “holding short” is arguably an unnecessary addition to a taxi instruction, given that flight crews should be aware that they must not taxi over a hold line and enter a runway without either a specific authorization to line up on the runway in preparation for takeoff or an authorization to take off. However, this occurrence demonstrates how errors in communication can happen and why the use of standard phraseology that reinforces the clearance limit has the potential to improve safety. If air traffic controllers are not required to use standard phraseology that reinforces the need to hold short of a departure runway, there is an increased risk of miscommunication leading to runway incursions.
This article is published under license from Avherald.com. © of text by Avherald.com.
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