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ASN Wikibase Occurrence # 195641
Last updated: 27 June 2017
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Type:Silhouette image of generic E190 model; specific model in this crash may look slightly different
Embraer ERJ-190AR (ERJ-190-100 IGW)
Owner/operator:Air Canada
Registration: C-FNAW
C/n / msn: 19000149
Fatalities:Fatalities: 0 / Occupants: 54
Other fatalities:0
Airplane damage: None
Category:Serious incident
Location:Toronto-Pearson International Airport, ON (YYZ/CYYZ) -   Canada
Phase: Taxi
Nature:International Scheduled Passenger
Departure airport:Toronto-Pearson International Airport, ON (YYZ/CYYZ)
Destination airport:New York-La Guardia Airport, NY (LGA/KLGA)
Investigating agency: Transportation Safety Board (TSB) - Canada
On 30 January 2016, runways 23 and 24R at the Toronto/Lester B. Pearson International Airport (CYYZ), Ontario, were being used for arriving and departing aircraft.
Air Canada flight 726 (AC726), an Embraer 190 aircraft, was operating on a scheduled flight to New York-LaGuardia Airport, United States, with 4 crew members and 50 passengers on board.
After pushback from the gate, the flight crew received an FMS data error message that needed to be corrected before takeoff. The flight was initially authorized to remain where it was on the apron until it was advised by the apron control that it would have to move. The captain requested authorization to taxi to a location that was out of the way, and at 20:56, AC726 was authorized to taxi on the apron to Taxiway DV, as it would be departing from runway 24R. The captain taxied the aircraft while the first officer (FO) worked with company dispatch to correct the FMS data error.
At 20:58, the FMS data error was corrected, just as AC726 arrived at Taxiway DV. Based on their close proximity to runway 24R, the flight crew completed the pre-takeoff checks while on the apron before requesting further taxi instructions to runway 24R.

==Call sign confusion==
At 20:59, AC726 then contacted ground control to request taxi instructions. The ground controller completed a scan of the NAV CANADA Extended Computer Display System (EXCDS), but since apron control had not yet forwarded the flight data entry (FDE) for AC726 to ground control, there was no indication on the ground controller's EXCDS display screen that AC726 was ready to taxi.
At the same time, Air Georgian flight 7286 (GGN7286), a Beech 1900 also taxiing for departure on runway 24R, was under the control of the ground controller. Because call signs of 726 and 7286 sounded similar, the ground controller believed that the transmission had originated from GGN7286 and asked GGN7286's flight crew to repeat their transmission. GGN7286 replied that it was on taxiway C. Shortly afterward, AC726 requested taxi instructions a second time because its first call had not been addressed. The ground controller then coordinated the transfer of control of AC726 with apron control.
At 20:59:58, the ground controller issued taxi instructions to AC726 to taxi from the apron to tunway 24R, stating, "seven two six, two four right for you, ATIS Zulu, altimeter two niner six niner, you're gonna give way to that Georgian and taxi into the holding bay."

==Approaching traffic==
While AC726 was taxiing, Air Canada flight 1259, an Airbus 320, was on final approach for runway 24R. AC1259 was operating on a scheduled flight from Puerto Vallarta-Licenciado Gustavo Díaz Ordaz International Airport, Mexico, to Toronto, with 5 crew members and 143 passengers on board. At 21:00:24, the airport controller cleared AC1259 to land on runway 24R.
The AC726 flight crew were not aware that AC1259 had been cleared to land on runway 24R because the landing clearance was issued on the tower frequency, while AC726 was monitoring the ground frequency.
At 21:00:42, the ground controller asked the AC726 flight crew if they were ready to go, and the FO replied, "I think that we finally got everything all sorted out here, so yeah, we are ready." The ground controller replied, "OK, the nineteen hundred [GGN7286] is still waiting for their video player to finish so he is not ready; you can go to the right side and [switch to frequency] eighteen thirty-five". This transmission was interpreted by AC726's flight crew as authorization to go to the right runway (i.e., runway 24R). AC726 subsequently read back, "Over to the right side, eighteen thirty-five. Thanks for the help, Air Canada seven two six." The ground controller then forwarded the EXCDS FDE to the airport controller as per procedure.

While AC726 was taxiing, both the captain and FO observed an aircraft on final approach and believed it to be landing on runway 24L, which is parallel to runway 24R.
While planning to release AC726, the airport controller observed the aircraft on the advanced surface movement guidance and control system (A-SMGCS) display as it approached the hold line. The airport controller then looked toward the final approach of runway 24R to ensure that AC726 could be taxied into position onto the runway in preparation for takeoff between AC1259 and a second aircraft, both of which were on final approach to land on the same runway.
At 21:01:33, while the airport controller's attention was directed away from AC726 and toward the aircraft that was on final approach to runway 24R, AC726 taxied over the hold line. At 21:01:45, when AC726 crossed the edge of runway 24R, the runway incursion monitoring and conflict alert system (RIMCAS) stage 1 visual alert displayed on the tower A-SMGCS display. The RIMCAS stage 1 visual alert went unnoticed on the A-SMGCS display.
Approximately 5 seconds later, as AC726 was turning onto the runway 24R centreline, the flight crew of AC1259, which was 0.41 nautical miles (nm) from the runway 24R threshold and 270 feet above ground level, reported to the airport controller that there was an aircraft on the runway and that they were overshooting the runway. The stage 2 aural alert on the tower RIMCAS sounded in the tower at the same time as AC1259 reported that it was overshooting the runway. AC1259 was climbing through 580 feet when it flew over AC726 on the runway.
The airport controller could not visually see AC726 on the runway from the south tower controller work position. When asked by the airport controller, AC726 reported that it was on runway 24R. The airport controller advised AC726 that it had not been given authorization to line up on runway 24R and requested that it hold its position.
At 21:03:00, AC726 was cleared for takeoff on runway 24R and departed. AC1259 subsequently landed safely following its second approach.

==Findings as to causes and contributing factors:==
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.


Accident investigation:
investigating agency: Transportation Safety Board (TSB) - Canada
status: Final
number: A16O0016
released:24 May 2017
duration of investigation: 1 year and 4 months
download report: A16O0016


AC726 taxi instructions (indicated by dotted line) into the runway 24R holding bay (Source: Google Earth, with TSB annotations)

Revision history:

24-May-2017 16:24 harro Added
24-May-2017 16:52 harro Updated [Photo, ]

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