HOW was THIS Allowed to HAPPEN?!

how can two aircraft be on the take-off role on the same runway at the same time sometimes it takes a truly bizarre incident in order to highlight weaknesses in a safety system and this story i'm about to tell you is a perfect example of that stay tuned the story i'm about to tell you took place on the 7th of march 2020 at 9 48 eastern standard time on toronto leicester b pearson international airport in canada now in order for you to understand how this incident could happen we first need to start with explaining a little bit about the layout of the airport itself the airport consists of five different runways connected by a taxiways and aprons on the south side of the airport you have two parallel runways runway six left and right and two four left and right on the center part you have two more parallel runways runway one five left and right and three three left and right and then on the northern side there is a singular runway wrong with zero five two three the incident that i'm about to tell you about took place in rome with zero six left but the fact that both rumble zero 06 left and runway 605 was in use at the same time is going to play a role here the air traffic control tower is situated at the center of the airport this means that the controllers in the tower will have a great view of what's happening on every part of the airport but it also means that some parts of the runways are quite far away from them so in order for them to be able to see what was going on there they would need binoculars from time to time inside the tower there are nine air traffic controller workstations and at the time of the incident four of those workstations were occupied two of those controllers were busy handling all the ground movements on the taxiways and aprons one was dealing with giving out air traffic control clearances on the clearance delivery frequency and one of the controllers were in charge of all of the takeoff and landings that controller was sitting at the workstation of the north controller position which meant that he had an unobstructed forward view of runway 60523 and also of the center runways runway 1 5 left and right and 3 3 left and right and those were the runways that the north tower controller would be normally handling but at the time of the incident the amount of movements at the airport as in takeoffs and landings were considered moderate to sometimes light and that meant that this controller was working in something called a combined position this meant that he was covering the workload for both the north and the south controller and since runway 06 left was in use as well as runway 05 in order for this controller to be able to see what was going on with 06 left and give clearances there he needed to stand up on his workstation turn around 180 degrees and look over the heads of his colleagues now this was not normally a problem he had a good view from there and this is something that they would normally do air traffic controllers have access to a lot of different tools and warning systems in order to increase their situational awareness tell them what is going on in their area of responsibility and also to warn them in case something is about to go wrong one of those systems is called rimcast which stands for runway incursion monitoring and conflict alert system dreamcast is part of the new advanced surface movement guidance control system or asmgcs this system fuses together information from a lot of different sources including ground radar but also the adsb transponder systems inside of the aircraft themselves and this is supposed to be far superior to the older warning systems that were much more reliant on only ground radar and because of that gave a lot of false warnings and wasn't very reliable now the way that dreamcast works is that it divides its warnings into two different stages stage 1 and stage 2 warnings like i mentioned before it utilizes ground radar and the adsb status of the aircraft to determine where the aircraft are and if they are in conflict with each other as in if they're sharing a runway for example but then it also takes into consideration whether or not these aircraft are airborne or how quickly they are approaching each other in order to determine which type if any warning it's going to issue a stage 1 alert is issued when dreamcast feels that two or more targets are on the same runway at the same time this is just a graphical alert on the screen it doesn't have any audio elements to it and it is inhibited when rimcast feels that one of the targets the one in front is accelerating away from the other target with more than 50 knots a stage 2 alert is both a visual on screen alert and an aura to highlight to the controller that something serious might be about to happen now the stage 2 alert is issued when a target is felt to be in front of an aircraft that is accelerating for departure with a higher speed than 20 knots this alert is inhibited if the target in front is felt to be accelerating away from the target behind because that will be interpreted as a departing aircraft and thus not a threat both of these warnings are inhibited if any of the targets are sent to be in the air as in airborne because this is an on-ground collision warning system and that brings us to the next interesting part of this puzzle which is how the aircraft in themselves sends that they're airborne and when they send that information out to adsb almost all modern transport category aircraft have something called weight on wheel switches and those are connected to their air data inertial reference units and when the aircraft gets airborne those weight on wheel switches will feel that the aircraft is no longer on the ground and they will send the signals up through the air data inertia reference units into the transponder and out via adsb saying i am now airborne these systems are generally very good and reliable but there have been some instances where they haven't worked and because the whole idea with the aircraft sending out its status as being on the ground or in the air was to start activating the tcas system to highlight potential conflicts and collisions in the air the system needed to have some kind of safeguard because of that and the need for redundancy it was also decided that these aircraft would include a system that would feel if the aircraft reached a speed of minimum 100 knots and if it did so it would send out an in the air signal no matter what the weight on wheel switches were saying and that's going to become important here now on the day of the incident the weather was really nice it was only some very high clouds light winds very good visibility and a temperature of minus 5 degrees celsius the controller had started his shift at 0 6 15 in the morning and he had rotated through several different controller positions until that time 709 30 he took on the role as a tower controller because the weather was nice he used something called pilot applied visual separation rules between the parting aircraft what this means is that it's up to the pilots in the aircraft behind to maintain visual separation between him and the preceding aircraft of the departure and by doing this the controller could save a lot of time because using the normal separation rules applied when the weather is less good would extend the distance between each departuring aircraft quite a lot now this type of very tight separation can only be used if there's no risk of wake turbulence to the aircraft behind this tends to happen if a large aircraft a heavy aircraft depart it creates these very very strong wake vortices behind the wings and those can actually be dangerous so if a large aircraft is departing you're going to have to extend the separation anyway but if it's a relatively small aircraft departing that is not going to be a problem and you can keep the departures really really tight now you might ask yourself why is it so important to keep the departures that tight those aircraft so close to each other but what you have to remember is that if a controller can manage to shave off a few seconds of each departure it means that they can actually get away quite a few more aircraft during any given hour and this means fewer delays for the passengers shorter on ground time for the airlines which ultimately saves a lot of money so this is something that any professional air traffic controller is trying to achieve now when pilot applied visual separation rules are enforced the air traffic control is not supposed to give the take-off clearance to the following aircraft until the proceeding aircraft is airborne the controllers will perceive the aircraft to be airborne when they initiate the rotation because they know that the pilots have done passed their v1 decision speed and that they are committed to the take-off most experienced controllers will have learned where different aircraft types typically start to rotate on the runway and when they see that those aircraft are passing that part of the runway they might start to initiate the take-off clearance for the following aircraft because they know that giving the take-off clearance and having that aircraft reading that take of clearance back will take a few seconds at which point that previous aircraft is going to be well airborne now before we get into the actual serious incident here i just want to share this short message from my sponsor who makes it possible for me to create this kind of content for you guys do you want to feel smarter by watching great documentaries from some of the best filmmakers in existence well then head over to curiositystream.com the netflix for documentary fans it is one of my favorite subscription streaming services with thousands of high quality non-fictional titles available enjoy new shows every week about things like nature science history sports and much more i recently watched a great documentary series called seneth advances in space exploration about the advances in rocket technology and satellites and you should check that out curiosity stream is available on pretty much any streaming device that you can imagine all around the world and it's extremely affordable with less than 20 dollars per year but since you are a subscriber of this channel you can use the link in the description here below which is curiositystream.compilot and the coupon code mentor pilot that will give you a whopping 25 further reduction on the price bringing it down to 14.99 per year that's only one dollar 25 cents per month which is incredible value for money thank you curiosity stream for sponsoring the channel now back to the video at time city 948 this is 18 minutes after the atc controller has taken up the role as tower controller in the tower and air canada embraer 190 with 83 passengers on board two cabin crew and two pilots are getting ready for takeoff at runway 06 left the tower controller tells them to enter the runway and he gives them the take-off clearance the pilots on board the embraer start to advance their trust levels for takeoff and the aircraft starts accelerating down the runway as the embryo passes 50 knots the adsb system inside of the aircraft sends a signal to the rim cast system inside of the control tower saying that it's now airborne like we were discussing before this is happening well before the aircraft is actually airborne it will be accelerating for many more seconds but it now shows up as airborne on the rim cast display sending out the airborne signal at 50 knots is much earlier than most other aircraft would do most other aircraft will do it at 100 not but it's still ok according to the current rules now as this is happening and the embraer continues to accelerate down the runway the aircraft controller clears another air canada aircraft a boeing triple 7 with 345 passengers on board two pilots and a 12 cabin crew to enter the runway line up and wait for departure the boeing triple 7 is significantly bigger than the departing embraer 190 ahead of them so wake turbulence is not going to be a problem and the pilots line up on the runway and gets ready for an immediate takeoff whenever they get the clearance on boarding brayer 190 everything is now looking normal and when the controller sees that the embraer is passing the point on the runway where he is pretty confident that it's just about to rotate the controller starts issuing the take-off clearance for the boeing triple 7 behind them this was read back by the pilots in the triple 7 and they started advancing their trust levels for takeoff initiating their own take of role now they could still see the embraer in front of them but they were also pretty confident that he was just about to get airborne here there might be some differences between the rules in north america and the rules that applies to us here in europe because i would not be allowed to start my takeover unless the preceding aircraft has gotten airborne there's also more rules in europe when it comes to the vertical separation needed during standard instrument departures so it is unlikely that this type of clearance would have been issued in this way in europe but in canada at the time this was perfectly normal when the boeing triple seven pilots had read back their take-off clearance the air traffic controller perceived that there was nothing more for him to monitor at that time on this runway so he turned back on to his noddly facing tower position in order to monitor some landing traffic on runway zero five but now comes the problem because as the air traffic controller was giving the take-off clearance to the boeing triple seven behind them the pilots in the embraer noticed that a big bird passed just below the side window on the captain's side they could both hear how it impacted the body and the captain thought that there was a major risk that this bird would be sucked into the left-hand engine and because he thought so he immediately initiated a rejected takeoff this happened at 139 knots which is just a couple of not short of the v1 speed of 146 knots so the fact that the controller had judged the embraer's position on the runway as being close to takeoff is completely understandable however now the embraer is not taking off anymore it's about to stop on the runway ahead of the huge boeing triple seven behind them the embraer pilots now followed standard rejected takeoff procedures and part of those procedures was that the first officer needed to call air traffic control and tell them that they were rejecting the takeoff unfortunately as he was doing this at the exact same time the first officer in the boeing triple 7 behind them also read back their take-off clearance and because the output strength of the radio inside of the boeing triple seven was submitted stronger than the embraer's radio this completely masked the message from the embraer meaning that not only did the air traffic controller not hear that the embraer was rejecting the take-off neither did the pilots inside of the boeing triple seven behind them the pilots of the boeing triple seven is now in the middle of their own take-off role and they can still see the embraer ahead of them but they're still assuming that it's about to take off because judging the distance and the speed of an object ahead of you when you are moving yourself is very very hard the controller on the other hand is looking the other way towards runway 05 where he has landing traffic coming in and the rim cast system on his screen ahead of him is not giving out any type of warning because the embraer even though it's decelerating now is still above 50 knots which means that it's still indicating airborne the tower controller now turns back toward runway 06 left again and he clears another aircraft a de havilland-8 to enter the runway to get ready for takeoff which means that there are now three aircraft on this runway at the same time but dreamcast is still not giving off any warning because now the embraer is indicated as airborne and the boeing triple seven has accelerated to above 100 knots which means that it is also indicated as airborne on his screen the boeing triple seven continues to accelerate down the runway and the pilots are now starting to get really worried about what they're seeing in front of them because in front of them the embraer has reduced their speed to well below 50 knots now and starting to come almost to a full stop but the rim cast is still not activating because now the boeing triple 7 is shown as airborne and the dash 8 has still not entered onto the runway behind them as the boeing triple seven reaches 127 knots the captain decides to reject the takeoff at this point that's about five thousand feet in between the embraer and the triple seven which is about 1 650 meters and it's shrinking very fast obviously now some of you might ask yourself wouldn't it be more logical or even safer for the boeing triple 7 to just continue to accelerate and take off above the embraer in a situation like this and while that would have been the case if they would have passed v1 before they would have noticed that this was happening the fact is that at this stage in takeoff raw it's no time for complex decision making the pilot perceived that the runway was blocked ahead of him and the way that we've been trained is that above 80 knots we're supposed to reject the takeoff basically only for engine failure and fire severe damage or the aircraft is unsafe or unable to fly and in this case a blocked runway could be considered to be either unsafe or unable to fly in any case it's very very hard to judge the distance ahead to the obstacle when you're on speeds like this so i completely understand the captain's decision to reject this takeoff and the investigators that wrote the final report about this incident did not question the captain's decision to reject either in any case the boeing triple seven was now rejecting the takeoff and the first officer communicated this fact to the tower controller the tower controller acknowledged this and started getting ready to give any type of assistance that the boeing triple seven crew might need after the rejected takeoff and he also started to look up in the sky where he was expecting to see the embraer 190 departing but it was at this point that he realized to his horror as he was looking down on the runway further ahead that embraer 190 had also rejected the takeoff and was now still on the runway at this point the first rim cast warnings activated in the control tower first between the dash eight that was just about to line up on romwe 06 left and the embraer at the very end then between the triple seven that was now decelerating at the middle of the runway and the embraer and finally between the dash eight and the triple seven in the end both aircraft managed to stop safely on the runway and the embraer 190 received the taxi clearance to exit the runway at the very end and then proceed to watch the terminal building the boeing triple 7 also exited the runway from about to the midpoint but then they had to hold on the taxiway for about 45 minutes to allow the brake discs to cool down until they were safe to continue and after that they also continued back to the terminal building the investigation eventually concluded that this incident had been caused by highly optimized atc workflow in combination with pilot-applied visual separation this together with the bird strike that caused the embraer to reject its takeoff and the simultaneous transmission from both first officers about the rto and the take-off clearance which eventually masked the message from the embraer and caused all of the involved parties to lose their situational awareness and this by the way is something that you might recognize from one of my other videos that i did which had a much worse outcome you can check it out up here these factors together with the fact that rimcast hadn't issued any warning to the air traffic controller during the critical phase of this incident because of the way that the adsb transponders on board of the aircraft had been programmed led to the issuing of an atc i an air traffic control information bulletin in this bulletin it was highlighted that certain aircraft types including the embraer might have a earlier onset of in-flight indication and that because of this some warnings might not come when expected there was also some experiments made by increasing the speed where the aircraft would indicate when it was airborne but it showed that if that was done it could lead to a much higher rate of false warnings that could eventually lead to the air traffic controller stopping to listen to dreamcast at all in the end though it was the human factor that saved the day when the pilots in the boeing triple seven realized the threat and rejected the takeoff thus saving the situation from becoming even more critical now if you want to check out the video where a very similar situation led to a much worse outcome then check out this video up here and if you want to support the work that me and my growing team is doing then consider becoming a patreon supporter we really really appreciate it and i hope to see you in one of my weekly patreon hangouts very soon have an absolutely fantastic day and i'll see you next time bye

Channel: Mentour Pilot

Views: 6,194,021

Keywords: true crime, crime stoires, storytelling, captain, mentour pilot, mentor pilot, crash investigation, full epsiodes, aviation, pilot, crash, air crash investigation, final report, boeing, airbus, piper, cessna, disaster, fatal crash, air incident, air disasters 2022, canada, embraer, 777, toronto, RIMCAS, ground radar, lester b. pearson, runway, alert, near miss, Crime storytelling, Storytelling, True story, Mentour pilot crash

Id: nj7nG6gJqsU

Length: 21min 26sec (1286 seconds)

Published: Sat Jul 16 2022