A Canadian Transportation Safety Board (TSB) report has been released after more than
two years of work investigating the events of March 7th, 2020.
On this day, two Air Canada aircraft experienced a close
call during the take-off of two jets. Findings from the incident cite radio communication
complications and inaccurate transponder data as factors, but, overall, an oversight on the part of
air traffic control. Today, let's go over the report's findings in more detail.
In March of 2020, an Air Canada Embraer E190,
registered C-FMZW, was about to fly from Toronto to Denver.
Immediately after the E190 initiated its take-off roll, air traffic control gave clearance for the
aircraft behind it to taxi into position and hold on the same runway. This was an Air Canada
Boeing 777-300ER registered C-FJZS flying from Toronto to Halifax. This route typically sees
smaller aircraft, but, perhaps as a result of pandemic chaos, larger aircraft were deployed.
A number of events took place over a few minutes. The 777 had been given clearance for take-off
while the E190 was still conducting its take-off roll. However, the E190 suffered
a bird strike in the process and rejected take-off at 135 K.I.A.S. (knots indicated
air speed). The E190 crew notified ATC of the rejected take-off. However, this message was
communicated at the exact same time the 777 sent its take-off clearance acknowledgment.
This overlap in transmissions meant that the 777 was unaware of the E190’s rejected take-off. As
such, the big Boeing jet began its take-off roll down runway 06L, accelerating down the runway,
reaching a speed of 80 KIAS. During this time, the air traffic controller had shifted his attention
away from this runway, assuming the E190 would take off uninterrupted. This shift
in awareness meant that the controller did not notice the E190 decelerating.
Continuing to accelerate, the 777 crew soon realized the E190 was still on the runway
and not becoming airborne as anticipated. Thankfully, the 777 initiated a rejected take-off
at a speed of 127 KIAS. The aircraft had actually reached a speed of 133 KIAS before decelerating.
Managing to stop clear of the E190, the TSB report notes that
the separation between the two aircraft was as close as 5,000 feet (1,524 meters).
While the distance may be quite large on an everyday human scale,
the size, weight, and speed of an accelerating Boeing 777-300
meant that any slower reaction could have resulted in more serious consequences.
So what happened? Obviously, the birdstrike started it all.
But more importantly were the air traffic controller's incorrect assumptions that the
E190 was becoming airborne. Because of this, the 777 was cleared to take off.
Escalating the danger was the overlap in communications as the E190's message
of rejected take-off went undetected by both ATC
and the 777 behind it. Analysis showed that transmissions occurred within one-hundredth
of a second of each other, with durations both around three seconds long.
Not knowing the E190 has performed a rejected take-off,
the 777's crew could see the jet ahead of it as it began its take-off roll.
Just like ATC, the 777 pilots believed the E190 would soon become airborne.
Even worse was the E190's transponder transmitting that it was in the air after it had achieved
a speed of over 50 knots. Thus, an inaccurate aircraft status was in place for nearly a minute.
Finally, a runway incursion monitoring and alert system
had failed to detect the danger as it had detected both aircraft were in the air
despite still being on the ground. This resulted in a late and inaccurate alert.
Ultimately, it appears that this incident was a perfect storm of small oversights that compounded
after a bird strike. Making matters worse was the inaccurate status being transmitted by the E190,
delaying a response from air traffic control and the 777.
What do you think of this event? Let us know by leaving a comment!