The Oil Change That Crashed A Passenger Jet | The Crash Of Smartlynx 9001

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Mini AIr Crash investigation makes some of the best videos.

👍︎︎ 9 👤︎︎ u/Amuzzin 📅︎︎ Feb 23 2021 🗫︎ replies

Well I've just discovered a new Youtube channel. Thanks!

👍︎︎ 6 👤︎︎ u/beethy 📅︎︎ Feb 26 2021 🗫︎ replies

What a wild story!

👍︎︎ 2 👤︎︎ u/wintertash 📅︎︎ Feb 27 2021 🗫︎ replies
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This is the story of smartlynx 9001. On the 28th of february 2018, a smartlynx A320 was over the skies of tallin, estonia. It wasnt flying anywhere it was just a flight to train pilots for the airline. On that day the plane had a safety pilot, 4 training pilots and a safety inspector onboard and before the flight they had a safety briefing, today theyd be a training session would have 5 touch and gos, for a touch and go you approach the runway as you would for a normal landing and then you touch down and take the plane back into the air, it's great practice for pilots. In addition to that they'd also have one go around and one full stop landing. The first student pilot took the wheel, or the sidestick maybe? As the student pilot did their touch and gos a warning popped up on the screen. ELAC1 + ELAC2 PITCH FAULTs. The ELAC or the elevator aileron computer had an issue, the ELACs as the name suggests controls the elevators and the ailerons, the ELACs take in the sidestick inputs and then move the control surfaces as the pilot commanded. Think of it as a middle man in the chain. The pilot who was monitoring the flight didnt think much of it and so they did what we all do, they reset the computer to clear the error. Weve all done it, turing it off and then back on fixes a lot of problems but not today. The first student pilot landed his plane and brought the plane to a stop and now the second student pilot assumed control of the plane. As the student number 2 took the plane to the skies the ELAC1 pitch fault error popped up again, and like last time the system was reset as per procedure. The same happened during the next touch and go. On the fifth touch and go an ELAC2 pitch fault error popped up. This happened again for the 4th students second touch and go, these pitch fault errors kept coming and the resets werent helping. It was time for The third touch and go the plane touched down and it was rolling down the runway. The plane then accelerated to 130 knots to lift back into the skies. The instructor asked the student to rotate, he said "rotate rotate" but the plane wouldn't budge, it was stuck to the ground firmly. The pilot replied that was trying his best to raise the nose of the plane into the air. At this point a new warning was shown "manual pitch trim only" the pilots would have to manage the pitch trim on their own. When you trim an airplane the airplane stays in a particular state without any inputs, so let's say you trim a plane up, then the plane will nose up on its own. But now the pilots had to manage that on its own. The plane was on the ground. It was as if the pilots were locked out of the controls of their plane. The plane gained so much speed that it lifted off on its own. Sensing trouble, the instructor said " I have control". As the plane was pitching up and flying away from the runway the instructor retracted the flaps a bit. The pilots selected gear up, but the plane started to descend, and the plane hit the ground, the plane hit the ground and bounced and began to gain altitude at 6000 feet per minute. As the plane climbed out they got a flaps locked warning and a warning that alerted them to a fire in engine number 2. They weren't out of the woods yet. The pilots kept the plane number control by manually trimming the plane and by using engine thrust. It was hard to control the plane when they pulled back on the power the plane would dive setting off the terrain alarm. But somehow the pilot stabilized the plane at 1200 feet and he took stock of the situation. The pilot in control asked, do we have engines, the safety pilot replied with "we have engine two fire". They were in dire straits, the elevators were in mechanical backup mode, engines one and two were damaged from the bounce and engine number two was on fire and the flaps were locked in place. The pilots declared a mayday and made a right turn to make a beeline for the airport before anything else failed. As they headed towards the airport they let the tower know of their intentions "Tallinn Tower, we are going for runway 26", they requested for fire trucks as the right hand engine was on fire. They talked about shutting the burning engine down but they decided to keep it running because theyd need all the help that they could get to get this plane down on the ground. Soon after the landing gear was extended and engine number two failed. On their final approach engine number one failed killing power to most of the airplane. Only the basics still worked. They had the runway in sight they were on the home stretch, the safety pilot stated. "Gear is down. We don't have engines". The safety pilot started counting down the airplanes speed. "Speed 150" "Speed 130", the plane touched down hard 150 meters short of the runway, it decelerated as it went along and soon it was on the runway but after a harrowing touchdown the plane came to stop to the left hand side of the runway. The plane was in one piece and all onboard were alive, they had survived their airborne ordeal. Now before we go any further lets just get some acronyms out of the way first. Theres a few so much so that I wanna call this episode the alphabet soup. Okay so the ELAC is the elevator aileron computer, the SEC stands for the Spoiler elevator computer, the THS is the trimmable horizontal stabilizer which I'm gonna call the horizontal stabilizer , the THS-OVM is the horizontal stabilizer override module and the PTA is the pitch trim actuator. With the airplane more or less intact and with a bunch of pilots who lived to tell the tale, they investigators were able to know that the plane lost pitch control during the flight and so thats where they focused their efforts. The pitch of the airplane is controlled by two elevators and the horizontal stabilizer, the two small wing like things at the back of the plane. These are massive and are moved by hydraulics, the hydraulic systems are controlled by electrical signals sent by a computer. Yeah if that computer were to fail it could lead to a loss of pitch control and thats why airbus built an insane amount of redundancy into this pipeline. Usually the horizontal stabilizer and the elevators are controlled by ELAC 2 if that computer were to fail ELAC 1 would take over. If that failed the SEC 2 would take over and if that failedSEC 1 would take over. If that failed only manual pitch trim would remain. The horizontal stabilizer is fed by 3 hydraulic lines and there are three motors and each of these computers is wired to use a different hydraulic line - motor combo, so no matter what the computers can control the pitch of the plane, or that's the idea. Now you might be wondering, how does the pilot control the horizontal stabilizer? In this chain, right before the trimmable horizontal stabilizer actuator moves the flight control surfaces, there's something known as the THS-OVM or the override module. The OVM allows the pilot to as the name suggests override the computer at any point. If youve watched a cockpit video of youve probably noticed a spinning wheel in the cockpit between both pilots. That's the trim wheel. The pilot can rotate it to trim the plane up or down. When the pilot does that a signal is sent to the override module. This causes a disc in the override module to move downwards, this means that the computer's commands can no longer reach the actuator as it is physically separated. The pilot now has all the control. But when this happens a small piston in the override module moves downwards and triggers three PTA microswitches, when these switches are triggered it sends a signal to the computers saying that they've been overridden. On the accident airplane as the plane touched down, the computer would bring the horizontal stabilizer to 0 degrees or neutral. But since they were practicing touch and gos, the pilot grabbed the trim wheel and he trimmed the plane to nose up, making it easier for them to take back off again. When he did this everything that we talked about before happened the OVM gave control to the pilot and the piston went down but the micro switches didnt engage correctly, this meant that the computers were not told that they were overridden. So the computer is commanding all sorts of stuff from the horizontal stabilizer but its not gonna carry those commands out because the pilot is the one controlling it. So as far as the computer is concerned the horizontal stabilizer is moving uncommanded and so the ELAC 2 computer by design fails, the computer is essentially programmed to go " wait i didnt command that something wrong in the system, i should probably step down and let someone else take over" . And this is how we got the ELAC 2 pitch fault warning. But the pilots trimmed the plane on the ground why did they get these warnings in the air as they were climbing out, well these warnings are inhibited during takeoff so as to not distract the pilots. Since they were being warned about something that happened a while ago. It was hard for them to piece together what was happening. In this way both the ELAC 1 and 2 computers failed, taking away half their redundancy. But the question still remained. Why did the PTA micro switches fail, why did they fail to inform the computers that they had been overridden? They sent all of the hardware to france where they tested the switches, they found that the activation of the switches were erratic and was highly dependent on the temperature. The reason for this? They found that the oil used in the THSA and the OVM was not the oil that the manufacturer called for, this oil had a different viscosity value and so the piston encountered a different amount of friction than what it was designed for and this meant that the piston did not activate the switches as intended and thats why the computers had no idea that they werent in control. They couldnt figure out where the oil of the incorrect specification came from, they guessed that it was from an earlier maintenance check. Now if you're still watching you might be wondering, okay that explains the failure of ELAC 1 and 2, what happened to SEC 1 and 2? Well to understand that we need to look at a moment in time, no literally a 1.02 second silver of time where something seemingly insignificant happened.First lets look at the SEC, the spoiler elevator computer can control the horizontal stabilizer when needed and much like the ELACs it too has a command sub computer and a monitoring sub computer. It works as youd think the command computer sends out commands and the monitoring computer makes sure that everythings alright. These computers take in all sorts of data from all over the plane, part of what they do is figuring out if the plane is on the ground or if its in the air. It takes in data from the landing gears to figure this out. On the accident flight the one of the landing gears was compressed for 1.02 seconds, it basically bounced. the monitoring computer picked this up but the command computer didnt because they work asynchronously and on data with different time stamps. When the landing gear is compressed for a second it sends the monitoring computer into flight mode. But since the SEC's command computer had not detected this it stayed in ground mode. This meant that the command computer and the monitoring computer disagreed with each other. Over time they diverged from each other. Remember how i told you that both halves work together, and within a short amount of time both halves of the SEC disagreed with the other by a large margin. Due to this internal disagreement both SECs failed. And with that the pilots had lost ELAC 1 and 2 and SEC 1 and 2, they no longer had pitch control , they only had manual pitch trim. In a way they were locked out of the controls of their plane. No one had expected such a series of unforeseeable events to occur, these events were so unpredictable, from the wrong oil to the precisely timed bounce of 1.02 seconds to a lot of other things. It was a perfect storm, but these pilots were lucky. They managed to walk away from something no one could have foreseen. Before we wrap up for the day on the scale of 1-10 how much automation do you want in your plane, where 1 is the least and 10 represents the most amount of automation. Im just curious because Whenever I post a video about automation going wrong i get a lot of comments lamenting the rise of automation and when I put out a video about a pilot making a mistake I get a lot of comments calling for more automation. Where do you lie? Let me know in the comments below.
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Channel: Mini Air Crash Investigation
Views: 378,832
Rating: undefined out of 5
Keywords: air crash investigation, mini aci, air crash confidential, airbus a320 crash, airbus, airbus a320, estonia plane crash, estonia smartlynx, smartlynx airlines, smartlynx airbus a320 crash, tallin airport, talling airport crash, runway undershoot, tallin airport airbus a320, the crash that no one could have predicted, smartlynx airlines a320 runway landing, avaition education, aviation documentary, aviation videos, 2018 a320 crash, aviation safety, avgeek, theflightchannel
Id: bo-S3kAInB8
Channel Id: undefined
Length: 13min 31sec (811 seconds)
Published: Tue Feb 23 2021
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