What happened to Turkish Airlines flight 1951?!

[Music] at local time 8 23 on the 25th of february 2009 turkish airlines flight 1951 a boeing 737-800 took off from istanbul ataturk airport with destination amsterdam and skipwall airport it was flown by a boeing 737-800 that was purchased by turkish airlines in march 2002 making it about seven years old at the time of the accident onboard the aircraft we had 128 passengers four cabin crew and three pilots because this was a training flight and designated as the pilot flying on the flight was the first officer only a few hours later this aircraft would have end up crashing about one mile short of runway one eight right in skipper during the initial descent down towards the isles approach runway one eight right in amsterdam the crew experienced several spurious landing gear warnings the pilots proceeded with the approach through the landing gate of 1000 feet without the aircraft being properly stabilized or prepared for landing and they did not notice that the speed kept creeping lower and lower and lower leading to stall at an altitude of 420 feet above the ground from which the pilots were unable to recover why did this happen [Music] now before we start the explanation here if you like these kind of videos where i explain you know incident accident or aircraft systems to you make sure that you have subscribed to the channel and that you've highlighted the notification bell so you get all notifications when i send out new and exciting videos to you what i'm going to do now guys is i'm going to give you a comprehensive view of the technical systems that were involved in this crash as well as how the crew interacted with each other and with the aircraft and why so what you have to understand is that this flight was a completely normal flight to start with the crew took off from other turkey international airport they climbed up to their cruising altitude of 36 000 feet and proceeded west one towards amsterdam what they didn't know though was that they had a technical issue with their aircraft that they still hadn't noticed now in order for you guys to understand the implications of this technical failure you need to understand a little bit about how the autopilot functions on the 737ng so essentially the 737ng have three different main components to the autopilot you have the flight control computer a flight control computer b and the outer throttle computer now the different flight control computers will give information to each pilot flight control computer a will give it to the captain flight control computer b will tell it to the first officer and they both have separate kind of input parameters so the flight control computer a for example will have the separate pitot system static system uh angle of attack vanes and radio altimeter and the same for the flight control computer b and it will show that information to their pilots okay if there is a failure in one of the systems well then that means that only half of the cockpit is going to be kind of affected of it now they will show a warning and the pilots need to figure out which one have the correct indications but there are checklists to do that now the outer throttle the outer throttle takes its information primarily from flight control computer a specifically in the case of the radio altimeter now generally speaking when we are flying on autopilot only the flight control computer on the side of the pilot flying is actually telling the autopilot what to do right the other one is a backup but there is a specific situation where both of the flight control computers are working together to fly the aircraft and that is during a dual channel approach hence the name so when we have approach mode armed and we have engaged both autopilot a and autopilot b in that case both of the autopilot will be giving instructions to the aircraft on how to fly and if one of the autopilot suddenly says dude i want to go to the right here and the other one says no no we'll continue straight ahead then they are the the way that the aircraft reacts is that it will just disconnect both autopilots and another function that we have during and out the coupled dual channel approach is that the aircraft isn't is intending to do an outer land in order to do a proper outer land the aircraft needs to flare right otherwise it'll be a very hard landing so there is a function in the autopilot system that when we go below a certain radio altitude namely 50 feet the autopilot will start to flare the aircraft and as we descend through 27 feet well then the radial altimeter will send that signal to the outer throttle and the outer throttle will reduce the thrust back to idle okay that's in order for the aircraft to be able to land and to then slow down after landing now that's really important for you to know because the failure that this particular aircraft has is a failure to the left-hand radio altimeter so there are two radio altimeters on the 737 one on the left and one on the right and what they are are basically just a sender and a receiver antenna at the bottom of the body of the aircraft the sender sends out a radio signal that bounces off the ground comes back into the receiver and then you know you calculate the height of the ground based on how much time it took this system is really really accurate at lower altitudes but not so accurate at higher altitudes which means that the pilots are only being fed information on the primary flight display about the radio altimeter height when we are below 2500 feet on this particular flight this radio altimeter on the left hand side on the captain's side started to malfunction just after departure the flight data recorder which was recovered after the crash showed that at 400 feet it started sending strange information to the flight control computer on the captain's side it basically said that it was minus eight feet all right now there are no indications that the flight crew noticed any of this during the initial part of the flight nor would you be expected to notice anything of that because the radial altimeter doesn't really have any function at this point so the aircraft just continued to fly towards its destination now this is not the first time that a boeing 737 ng had had problems with the radio altimeter at this time in fact there had been loads of reports from different operators all over the world to boeing about spurious and intermittent problems with the radio altimeter the problem was that when the technical department tried to go in and look for the source of the problem they couldn't really find any because these faults they would come up on one flight disappear after a few seconds and then it would work perfectly for three flights and then it might come back again so boeing and the technical departments at turkish airlines for example thought maybe this has to do with moisture creeping into the the antennas so they started fitting the aircraft with these gaskets around the antennas and they insulated the connectors to make sure that this didn't happen but it still happened from time to time because of this boeing had actually sent out a change to their dispatch deviation procedure guide this is a document that you read prior to dispatching the aircraft if you have a failure and the ddpg now said that if there was a problem with the radioaltimeter well then you shouldn't be using the outer throttle for subsequent approaches now the issue with that is that this document is only really read prior to departure while we're in flight the pilots will be reading from the qra the quick reference handbook and in the quick reference handbook there were no such instructions that the the the kind of thought from boeing on that was that if a pilot is up flying and gets a faulty indication or the outer throttle is not working the way it should be doing well then you can just disconnect it right it's the job of the pilots to monitor the instrumentation and how the aircraft is behaving and if the system is not behaving the way it should be then it's perfectly possible to disconnect out the throttle and fly the approach with manual thrust or even flight manually [Music] now on this particular flight in the flight deck we have three pilots and the reason for that was that this was a line flight under supervision or a line training flight okay in the captain's seat we have a really senior line training captain captain hassan tassin arisan he is 54 years old one of the most senior training captains at turkish airlines at the time and an ex-military fleet commander he is training another ex-military pilot first officer murat cesar murat is 42 years old he has over 4000 hours of fast jet time in the turkish air force but this is only his 17th flight with turkish airlines so he is being trained into his new role as a first officer now in turkish airlines at the time during line training and below 20 sectors you need to have a safety pilot that means a pilot who is monitoring that the flight crew are doing what they're supposed to helping the line training captain out in case you know he needs to be focusing on instruction to make sure that nothing bad happens he's also there in case something would happen to the captain so that he could jump into that wall and help the training first officer out doing that role was first officer olga oscar olga is only 28 years old but it's still fairly experienced he has worked about three years for turkish airlines at the time and he had previous experience flying the md-80 anyway pilot flying for the flight is the training first officer murat so as they're getting closer towards amsterdam murat started to take up the weather for for amsterdam skip hall and the weather indicated a kind of okay but marginal weather so there was indicated clouds at 600 feet with an overcast cloud layer at 1100 feet and the visibility was 3500 meters but going down temporarily to 500 meters the flight crew discussed which type of approach to fly and they just they decided that it was perfectly okay to fly a category one ils approach into runway one eight right which was in use for uh for the approach a category one is approach will allow the aircraft to fly down to 200 feet and to a visibility of 550 meters so first officer murad is now setting up for the approach and he's starting his approach briefing for the captain and the safety pilot and at this point the aircraft is flying completely normally there are no warnings no indications that anything is wrong at time 953 they initiated their descent with dutch air traffic controls the [Music] cockpit voice recorder is indicating that they got a lot of different heading changes altitude changes and speed changes which is completely normal when you fly into amsterdam amsterdam is one of the more busy airspaces in europe and eventually they get into contact with amsterdam area control amsterdam area control clears them to descend to flight level 7-0 towards a point called artip which is part of the standard arrival procedure for runway 1 8 right in amsterdam and contact skikpo approach control the the captain who has the pilot monitoring does that he contact skipper approach and tells them where he's going a skipper approach comes in and tells him to proceed direct to the vor spikey boar and the center flight level four zero which is four thousand feet now up until this point the descent has been completely normal there hasn't been an indication of anything being wrong but here during the time when the captain is speaking to approach control is the first indication that something is wrong with the flight because as we are listening to the cockpit voice recorder you can hear how the landing gear warning horn suddenly starts sounding now the landing gear warning horn is a system that is there to remind the pilots that they've forgotten to take in the gear down prior to landing the system is connected to both the configuration of the aircraft as in what flap setting we have the truss lever angle but also crucially to the radio altimeter okay so as this warning is going on it actually goes on for about a minute and a half and that's a very long time to be listening to that warning during that time on the cockpit voice recorder you can hear how the captain is muttering radio altimeter and landing gear indicating that he's looking at his primary flight display that he sees a strange value and from the flight data recorder we know that it was indicating minus eight feet at this point and that he recognizes that the warning that he's hearing is the landing gear warning horn now the warning then cuts out but it will come back several times during the approach but just intermittently the aircraft is now being cleared to descend down to 2000 feet and turn onto a heading of 265 degrees which is kind of an in this initial base leg to intercept the aircraft to the ils from a 1 8 right when the aircraft reaches 2 000 feet the first officer calls for flaps one and reduces the speed back to 195 knots now during this time the output throttle is working perfectly okay as the speed is being reduced to 295 on the mode control panel the other throttle just brings the trust back until the speed has been established and then comes back up again like a good boy like the way it's supposed to be working soon after this air traffic control gives the crew its final heading heading 210 degrees and they're now cleared for the ils approach for runway 1 8 right now in the standard operating procedures of turkish airlines at the time all approaches are supposed to be flown as dual channel approaches when available so this means that because they're now getting their final approach heading and they're clear for the approach the first officer's pilot flying is supposed to engage the second autopilot to make it a dual channel approach now he now makes a mistake which is very common among cadets like when i'm training this happens all the time and that is that instead of arming the approach mode first and then engaging the second autopilot in order to set it up for a dual channel he does it the other way around he switches the command a on before approach now when you do that what you're essentially telling the aircraft is that you want the other autopilot to be in command so in normal circumstances when everything works the way it should it just switches over from command b to command a and continue flying on autopilot but when the first officer makes these mistakes and switches on command a what happens is that the autopilot disconnects itself right the first officer reacts to this by just re-engaging command b but he doesn't really talk anything else about it he doesn't mention it more and there's no discussion going on with the captain so this is actually an indication that something is definitely wrong with the autopilot flight director system it should not react like this but anyway the crew continues to fly the first officer does not try to engage the second autopilot again and soon thereafter he calls for flaps five continues to reduce the speed back to 170 knots and here you can once again hear the landing gear horn going off just for a short while this time the first of them goes to ask for flap 15 followed by gear down right the procedure at turkish airways at the time was to select gear down and flaps 15 as the glide slope becomes alive but the crew is now finding themselves in a fairly tricky position and that is because in skipple approach control at the time they have made it a habit to close the aircraft in on a very tight circuit basically aiming to vector the aircraft to intercept the glide slope and the localizer at 6.2 miles generally when we fly every day kind of approaches we tend to intercept maybe eight to ten miles because that will give you a little bit more room to intercept the glide slope from below but in this case the crew had been getting a vector of 210 degrees now if that would have been a track they would have intercepted the glide slope and the localizer at 6.2 miles which would have been perfect but because there has been a little bit of westerly wind at this altitude the aircraft has actually been pushed to a track of 201 degrees instead and this will have them intercepting the localizer at five and a half mile and above the glide slope and that is going to become very important anyway the first officer is doing a good job here he's anticipating that we are going to have to descend like a rock later on so it's getting the gear out and the flap 15 and the speed back they intercept the localizer captain calls localizer intercepted and after this things happens very very quickly and it's important for you to understand why this has an impact because as the localizer is now being captured the someone is reaching up and changing the mcp altitude from 2000 feet which is what they were cleared at to first 1200 feet and then 700 feet okay then vertical speed is being initiated with initially 500 feet per minute descent and then 1400 feet per minute this is being done because if you get localizer intercept but you're above the glide slope okay the glide slope will not capture and you cannot descend the aircraft away from your mcp selected altitude without changing it right and you have to change it quickly down get the aircraft descending quickly because as you're getting closer towards the runway the glide slope will go lower and lower and go further and further away from you so if you're not quick and you don't do this quickly it's very likely that you will miss the glide slope completely and you won't be able to fly the approach this is why it's likely that it wasn't the first officer who did this but it was actually the captain who saw that this was about to happen reached out and now it's starting to input on the autopilot while the first officer is still pile flying but something that has happened now which they haven't noticed is that the roll bar on the captain's flight director has disappeared okay now this is significant because during a dual channel approach when the aircraft comes at about 50 feet of the runway both the localizer and glide slope bars on flight director disappears out of view that's because we're not supposed to use them for a flare okay the aircraft will be flaring automatically but in any case we're not supposed to be looking at the flight director during that part of the of the approach so if they are over the runway this is normal all right but at this point as they get localized to capture the roll bar disappears the aircraft is now descending the workload is expected to be quite high here because the captain is actually doing the job of the first officer while still trying to monitor the situation at the same time the safety pilot has been in contact with the cabin crew the cabin crew calls in to tell them that the cabin is ready for landing right so he's looking the other direction it's likely that he never noticed that this happened to the to the flight director bar on the captain's side and even if they would have noticed it's unlikely that they would have understood the significance of it now you might ask yourself what is the safety pilot doing at this point and actually the safety pilot around this point is pointing out to the captain that remember that you have a radio altimeter failure on your side the captain responds with kind of a yup affirm but there's no further kind of discussion and in fact none of the warnings that they've gotten up until the point not the um the landing gear horn not the faulty kind of radio altimeter indication has led to any real discussion among the crew about why this is and what kind of implications it could be so the aircraft intercepts the glide slope as they intercept the glide slope the pitch bar on the captain's flight director also disappears indicating kind of the same as we were talking before as they're descending now and they've been sending with a much higher vertical speed than normal what happens when you do that is that the aircraft will accelerate and the outer throttle as the speed is accelerating away from the set value that the pilots have selected on the mode control panel will try to reduce the speed right so the other throttle has moved into a as in into approach idle at this point now the pilots wouldn't think that this is strange this is actually what it's designed to do so the fact that the out the throttle is sitting there and there's absolute idle on would not kind of raise any suspicions by the flight crew the problem is though that it hasn't gone into because of the high speed it has actually gone into the flare mode because it thinks that it's actually during a flare before landing so the outer thrust will sit in the full mode for the next 98 seconds now skipper approach has seen that the aircrew have established themselves on the localizer they tell them to contact a skipper tower the captain who is pilot monitoring calls into tower and the tower tells them that they are clear to land runway one eight right this is the last communication that air traffic control will have with turkish airlines flight 1951. the aircraft continues to descend and the captain next calls out 1000 now this is really important because in turkish airlines at the time the landing gate is 1000 feet now what means with the landing gate is that when you pass that altitude the aircraft has to be completely established and ready to land you need to have completed your landing checklist the aircraft need to be fully configured you need to have the correct speeds be on the localizer and glide slope and the thrust needs to be up to its approach value and on a flaps 40 approach when you have flaps 40 selected the trust is normally sitting between 55 and 60 and one at this point the flaps have not been selected to 40 trust is still as idle and the landing checklist has not been completed so the flight crews actually pass the landing gate without being properly established right so what they should do at this point is they should execute a go around right this is why we have landing gate so that there is no choice okay there's no ambiguity here if you pass the landing gate without being properly established you go around no questions asked but in turkish airlines it's also the sop that the captain is the one that decides if a goron should be flown or not and in this case he doesn't call for it so the safety pilot and first officer doesn't question it they continue the approach at 900 feet the first officer calls for flaps 40 flaps 40 is selected and then someone tries to arm the speed brake right this is also part of the landing checklist but what happens on this occasion is that as the pilots start to arm it they get both the speed brake armed and the speed brake do not arm warning light the reason they're getting this is probably also connected to the problem they have with the radio altimeter because once the aircraft is on the ground you will actually get this warning but the implication for them as they're arming it is that there is actually a quick reference handbook checklist to be done if you get that kind of warning it is an indication that the speed break will not come up automatically and you need to do that yourself so there is a checklist that needs to be done and there's actually a performance calculation because it will have an impact on our landing distance anyway this is completely disregarded the speed brake is left with both of these lights illuminated and they continue to descend so at this point the captain is starting to challenge the landing checklist and they go through it point by point as a now descending down the last point on the checklist is cabin crew seats for landing they now realize that they haven't been talking to the cabin crew so the captain turns over to the safety pilots and tells him to please seat the cabin crew save the pilot tells the captain that yeah we got cabin secure earlier and he reaches for the pa mic and starts making the pa for the cabin crew to seat down the aircraft is now at 500 feet descending captain calls out 500 feet but what has happened now is that instead of coming up with the thrust to keep the speed that the indicated 144 knots that they should be keeping the trust is still in the position and the way that this impacts the flight is that as the speed is now decelerating down below 144 knots the only way for the aircraft to keep the glide slope is to increase its nose position so the nose keeps pitching back back back back back and at this point it's probably around 10 to 11 degrees nose up which is an extremely high nose position for this configuration at this point generally when we're flying a flaps 40 normal approach you should have about zero so the nose should be sitting on the horizon as we're descending down on the glide here it's sitting to you know 10 to 12 degrees nose up which is not normal the next thing that happens is that they get stick checker activation okay the speed is now a below 107 knots and it touches the lower red barber's poles on the primary flight display and that starch the stick shaker and basically whenever we get a stick shaker you need to react very very quickly okay because you're about to stall you haven't stalled yet but you're about to stall as the stick shaker activates the safety pilot cries out speed speed speed and there is an indication on the on the flight data recorder that the nose is being pushed forward and the trust is being pushed forward as well to about mid position it's likely that it is the first officer who's pilot flying who's doing this remember he has been just recently in the simulator having done his typewriting training so he would have done approach to stolen recovery quite recently but at this point the captain calls that he has controls as soon as he does that the thrust goes back down to idle again because the outer throttle is still engaged it's still in mode so it just pushes it back and initially the captain seems to be pushing the nose forward that brings the aircraft out of stick shaker for a few seconds and then about nine seconds later the captain realizes that they don't have any trust he brings the trust levels up disconnected out the throttle and the autopilot and raises the nose but the problem is that this is all too late it takes four seconds for the engines to spool up from approach idle to full thrust and during that time the aircraft enters into a full stall and this is only at 400 feet from which it is impossible to recover the last indications on the corporate voice recorder is the ground proximity warning system warnings for pull up terrain terrain pull up and then the aircraft crashes into the ground and all recording stops [Music] the aircraft hits a field about 0.9 nautical miles prior to the threshold around the 1 8 right it hits with the tail section first and it breaks into three different pieces the engine disattaches from the wings and gets thrown about a thousand feet further than the aircraft body and the cockpit slams hard into the ground this kills one cabin crew five passengers and also the three pilots in the cockpit so what did the final report reveal then well the final report basically said that there were several factors that impacted the outcome of this flight they said that the failure of the pilots to go around when they pass the landing gate without being fully established was one of the causes also the fact that they you know did not monitor their airspeed enough to realize that the trust was in idle and the speed was going down well below their minimum approach speed also led to it but the fact that there was a technical malfunction on the radio altimeter that caused the outer throttle to reduce back to idle and stay there was definitely a part of the blade on top of this was also air traffic control's decision to give them this tight vector now it had been a standard procedure in skipper at the time to give these tight vectors but the fact is that the actual rules for dutch air traffic control at the time stated that they should have given them much more distance they can give them a short approach but they have to indicate that to the aircrew because the aircrew can then mentally prepare for the higher workload that will come to that so that was also one of the finding another finding was the way that the pilots executed the approach to stall and recovery maneuver which was deemed unsufficient this was then disputed by the airline the airline did not agree to this but what has happened and what we as pilots have kind of experienced after this is that the amount of training when it comes to approach to stall and recovery has changed quite a bit okay it used to be training at high altitude only after this incident we started practicing approach the stall and recovery both at high altitude but also in traffic circuit altitude and on final approach because the way to handle it is actually quite different the fact that you have so much more drag when you're in a landing configuration makes the recovery from the approach to stall quite a bit more tricky so that was a change we also included the approach to stall and recovery training in recurrent training so prior to this incident that wasn't a requirement you could basically just do it as part of the type rating and then never do it again but after this it was included in the recurrent trainings at least you would do it every three years and in fact we are doing it quite more often than that right now after this incident there has also been all sorts of different kind of contestations to the final report both by turkish airlines but also by boeing and the um the final report has been have had to be revisited several times after this but the the facts kind of stays the same so i really hope that you're enjoying these uh series that i'm doing about famous air crashes and investigations if you want to see more of it i have a full playlist up here that you can check out and please let me know what else you want me to talk about sign them in in the comments here below and i will try to answer as many of your questions as possible i also want to send a huge thank you to the sponsor of this episode which is nordvpn now i use nordvpn myself especially when i'm out traveling to you know through airports or restaurants where i might be using local wi-fi it's very good to know that my data will not be able to trace when i do so but to be perfectly honest what i use it the most for is to get past these pesky regional restrictions when it comes to netflix for example you know by the click of a button i can just change my location to be in the united states and there's loads more and better um tv shows to watch there if you are interested in this then use the link here below that link will give you a whopping 68 discount on the two-year deal with nordvpn and you can use that deal to up to six different devices on the same deal so go down click the link and consider supporting me by supporting them [Music] [Music] zero speed [Music] foreign one [Music] level 340. [Music] zero wow yeah as a very large emergency it looks like we lost an aircraft so continue on this heading one two and two another heading one two one two five [Music] you

Channel: Mentour Pilot

Views: 648,140

Keywords: Tk 1951, tk1951 crash, tk 1951 air crash investigation, tk1951 crash animation, tk1951, Mentour Pilot, mentour pilot 737 max, aviation incidents, aviation incidents and accidents, fear of flying mya, fear of flying help, nervous flyer tips, Aviation documentary, aviation scene, Boeing 737, Boeing 737NG, Airbus A320, Breaking news, Aviation facts, air crash investigation 2021, aircraft investigation, Autothrottle, auto Throttle, Amsterdam crash, Landing, takeoff

Id: eMUBzS0n_Cw

Length: 38min 34sec (2314 seconds)

Published: Fri Jan 29 2021