Clear Ice Causes Engine Failure On Scandinavian Airlines Flight 751 | Mayday | On The Move

good morning ladies and gentlemen this is your captain i hope you have it captain stephen rasmussen has been in love with flying all of his life i got my first idea of flying when i was a young boy after learning to fly in the air force rasmussen joined scandinavian airlines he seemed to like be the one who really enjoyed his job on december the 27th 1991 he's in command of a state-of-the-art dc-9 the flight will take him to the very edge of his abilities as his engines fail and his plane falls out of the sky i was in a nightmare stockholm scandinavian 751 we are crashing into the ground now what caused the most baffling accident in sweden's history is nothing investigators could have imagined what they finally uncover will strain rasmussen's lifelong relationship with airplanes to the breaking point i really felt that i didn't trust the aircraft [Music] hey [Music] it's two days after christmas stockholm islander airport is a mess of snow slush and ice passengers boarding a mid-morning scandinavian airlines flight to copenhagen are finding the cabin very uncomfortable it was really warm inside the plane when we entered because there had been like heaters on during night and i saw when the passengers embarked they also wanted to take off like jackets and shoes and because it was like a sauna [Music] is it possible to turn the heat down now 34 year old ulf sedermark has been with the airline for four years he's the first officer on today's flight it was a light snowfall temperature was just below freezing and light winds we were gonna fly stockholm to copenhagen and then to warsaw back to copenhagen and down to barcelona that day would be a quite a long working day stefan rasmussen has just finished an exterior check of the plane the danish pilot is in command this morning in those over 12 almost 13 000 hours i have been sitting in an aircraft i always felt that i i put the aircraft and back on my like a rickshaw and and when we took lift in the wings we melted together the plane rasmussen is strapping on today is a nearly new dc-9 easily identifiable by its two rear engines by now everyone should know that door stays open right even in the days before terrorist threats flying with the cockpit door open is unusual it's just one way rasmussen has endeared himself to the crews and passengers he flies with [Music] i always had my cabin door open because i found out that if we had the door open and they could see that they were a human being in there they trust you for me it felt good that the door was open it just feels like you have a connection more than if the door is closed the winter weather has delayed this flight but rasmussen won't compromise safety for schedule where are we now with the ic the wings aren't quite done they've done the underside now they're doing the top thank you under captain rasmussen's instructions the ground crew had already de-iced the plane once now they're giving it another pass and it took a while but they had trouble getting rid of the snow on top of the wing so we were slightly late for their push back out our runway for captain per homburg this kind of delay is routine business he flies dc-9s for the airline a passenger this morning he's scheduled to command another flight later that day good morning ladies and gentlemen this is your captain i hope you had a good christmas we're just getting our wings cleared as we've had a bit of snow overnight and when that's finished we're ready for takeoff for some warmer weather i hand-picked the airline's best cabin crew to take care of you today we all hope you have a nice flight finally scandinavian airlines flight 751 is cleared to proceed there are build-ups of snow that the crew must avoid on the way to the would have runway nice of them to clear the snow well that would have made it too easy approaching holding point runway zero eight roger scandinavian 751 spoilers armed auto break take off unarmed runway update performed checklist completed said power despite the winter conditions the takeoff is routine v1 rotate gear up gear up selected when wolfie reads out for the gear i heard the things which was different just 25 seconds into the flight as the plane is climbing there is a problem when you hear things that are different from the anomaly you get suspicious there was a really big raw in the aircraft almost like an explosion boom there was another banging noise that i just thought what is that i had never heard that before it's obvious the source of the noise is the right engine that sounds serious i believe it's a compressor stop i took the the right throttle i moved a little back but there it it really became strange because the engine performance increased when i reduced the total it's like if you're sitting in your car and you're turning your your wheel to the left and the car is driving to the right you get confused we're not supposed to like call into cockpit now and then i thought this is an emergency i have to call captain but captain rasmussen doesn't respond to the call he's too busy trying to figure out what's going wrong with his plane i couldn't see anything on the instrument they were quite stable and and they're quite normal range and no no problem but but i could hear those drawing every second he searches for telltale signs of attack or structural failure i looked up at here they kept impression because if you have a a bomb or a freight door and thing which is ripped off that'll that'll give a decompression in the cabin pressure levels are stable but the crew has other concerns i saw the smoke and it smelled burnt what should we do about this just 3 200 feet above the ground the emergency escalates the right engine quits when we have flown a little over one minute the right engine just went down i had a very very short moment of thinking that i was in a nightmare and just dreaming i was confused i was really confused two seconds later the left engine also quits the plane is now powerless one engine drop and then another engine drop i thought that it wasn't true it wasn't true it wasn't real less than a minute and a half after takeoff the dc-9 begins falling from the sky and after that it was complete silence and i think that was the worst moment for me just being in the air and it's so quiet it was like a bird just sailing through the sky so then i started to to get scared engine relay as the pilots try to restart their engines things get even worse the left engine erupts in flames i saw the exhaust gas temperature was rising rapidly max temperature was around 680 degrees celsius and i saw it to go above 800 a fire in the engine could spread to the rest of the plane should i pull if sedermark pulls the fire extinguisher in the left engine he will never be able to restart it he pulls the handle to put out the fire from his seat captain per homeburg can see that the crew is in trouble flight 751 is now falling at a rate of 1200 feet per minute but air traffic controllers at the stockholm airport have no idea the plane is in trouble ireland stockholm scandinavian 751 good morning sk751 climb to flight level 180 we have problems suddenly the radio goes dead a result of the failed engines [Music] only the right engine can provide power but it's now spinning too slowly to generate electricity for the instruments without the engine you don't have any propulsion so you will the only energy you have is your height with time running out the pilots of flight 751 must find a way to restart the right engine or else crash into the countryside below scandinavian airlines flight 751 is now falling from the sky at 20 feet per second oh can i help captain per homburg who boarded the flight as a passenger becomes part of the flight crew like he came out in the cockpit and he said is there anything i can help you with i don't think i even said yes i said just start the apu if the auxiliary power unit can be launched it will bring back the radio and instruments so i just handed him the emergency checklist and started focus on controlling the flight to see that we were maintaining the speed and by the attitude that we were wings level he managed to start the auxiliary power unit so my flight instruments were supplied from that but for some reason captain rasmussen's instruments don't come back online he managed to to fly the plane basically by feel power is also restored to the cabin but it's small comfort to passengers who now know they're in extreme danger stockholm air traffic control instructs the pilots to return to the airport scandinavian 751 are you able to turn right heading zero niner zero radar vectoring for zero dash one but the plane is now just sixteen hundred feet from the ground and first officer sedermark's attempts to resuscitate it aren't working roger we are maintaining our heading but we are trying to restart our engines making a 180 degree turn back to stockholm could be catastrophic i really had the feeling that if i turn the aircraft at that time we have stalled when you're turning back you are losing a lot of energy so the most safe thing to do is actually just to go straight keep your wings level that means that you will use less energy of your altitude so you can maintain your speed you can maintain two thousand feet we are not able to maintain two thousand feet we are descending we are at sixteen hundred feet and descending homburg wants rasmussen to focus his attention on finding a landing spot look straight ahead look straight ahead he was screaming at stefan just to look straight ahead and watch the flight path prepare for on ground emergency on ground emergency bend down bend down bend down so we shouted ben down i don't know how many times bend down bend down bend down keep your seat belts fastened while passengers brace rasmussen considers where to land his plane look straight ahead and i had an idea that on the northern direction could bring us out to the to the baltic sea with with that time frozen and that's an excellent runway but instead he finds himself gliding powerlessly over a dense forest i saw that green area and i saw that little uh light spot in the middle of the forest but that really looked short still right still right just 500 feet above the ground captain rasmussen lifts the plane's nose to slow it down hoping to soften the crash landing pine trees from the top there look very soft i could use the trees as almost like a pillow should i lower the landing gear yes gear down bend down and hold your knees i prepared myself for a hard impact if it's an emergency landing we have no engines i just thought this is going to be a hard landing stockholm scandinavian 751 we are crashing into the ground now i i wasn't afraid until we were flying into the trees then i was scared and i knew we were not gonna make it i didn't thought i should die i knew i should die i made my pray to god and then a moment after we were we were we were in a strange world after we have come to a complete stop i feel the smell of airplane fuel i thought okay we're going to explode and i look around and i see the snow because there was a big crack in the airplane fuselage just in front of the aft galley and you could just walk down on the ground everything was quiet and i woke up it might only have been a split seconds or so i was afraid that my spine was broken that i wasn't wouldn't be able to walk again so i remember i was sitting there and i was moving my toes and my feet just to see if i could have control over them i had a pain in my hand because i had broken a bone in my hand and i was bleeding heavily from my forehead so i was trying to get clear of all the blood that was coming down in my eyes and stefan told me that we had to get out of the aircraft after plowing through 125 meters of pine forest the pilots fear is now that the broken aircraft could catch fire dozens of passengers escape through the brakes in the fuselage walls but captain per homburg has been knocked unconscious by the crash it all went so fast that like no one could take in like what happened so i tried to to stay with the group of passengers i had there but i just knew the feeling also that we had to wait a long time for for the rescue teams help will be here soon fortunately no fire materializes but because they removed their winter clothing while boarding the sweltering plain many passengers are starting to freeze most people were just standing in their shirts t-shirts very very little clothes few didn't even have shoes on they are now at risk from hypothermia so i focused on being caring maybe i did it for my own sake also i needed a hug also it was comforting to like comfort someone else the wreckage of scandinavian airlines flight 751 lies just 15 kilometers northeast of stockholm islander airport the fuselage has broken into three pieces in the chaos of the moment nobody knows how many people have been killed in the crash [Music] rescuers arrive within minutes and attend to the freezing survivors they pull captain per home berg from the cabin unconscious he landed on the wall at impact and he skidded down on the wall to to the floor at impact so he he was quite badly damaged he cut his eyelid and he also got his collarbone that was broken off so his shoulder was in front of him 92 of the passengers have sustained injuries only eight are considered serious but when the crew conducts a head count they're stunned to learn that out of the 129 people who boarded flight 751 not a single one was killed in the crash everyone survived was like a shock just to take in wow that was a fantastic comment since i was the happiest captain in the world we were all alive it was a great moment reporters break the remarkable story to the world as the swedish accident investigation board or saib takes charge of the case [Music] scandinavian airlines alerts its own investigators dispatching tori huldgren to head up its team it's most unusual that the plane crashes in in the woody area and everybody survives and never heard of it before the police kept everybody off the site itself it was recording around the aircraft of 100 meters we had a complete aircraft nothing had burned and we had lots of good data henrik islander from the saib gets to work on the evidence and we all started to plan the documentation of the extend site which means photographing all the final approach through the wood you know and and to take photos of all the parts that were spread all over the place the two black boxes which record cockpit conversations and store flight data are recovered immediately [Music] investigators speak to survivors everyone tells a similar story would you mind telling me what you saw and heard loud booming sounds from the engines moments after the fight began smoke in the cabin and finally the entire loss of power and an engine on fire you have a twin engine aircraft and you are really not supposed to lose both engines at the same time the pratt and whitney turbofan engines are sent to a scandinavian airlines repair shop for closer examination investigators are eager to speak with captain rasmussen about the incident but to their dismay scandinavian airlines takes him to the media first the first question what did you think when boat engine refused to function it'll take me awful long time to tell you all that the normal case is that the key weaknesses like the crew and so on should be kept in canteen until they meet the investigation board european media celebrate captain stephen rasmussen as a hero for landing the dc-9 without engine power but investigators consider the possibility that he or his co-pilot had made errors that caused the crisis in the first place the owner and glory always rests with a captain but so does also the mishaps i knew that being a person where the in the spotlight of the press would be a quite different situation and i said to myself the only thing you can do now is to give them all the story and then pray that they will find the reason lars lindbergh is an investigative representative for the swedish airlines pilot association he examines the wreckage for signs of mechanical or structural failure we knew both engines had failed for some reason so it was concerned what was the background for something uh like that to happen the first time i saw the the engines in the workshop i was surprised is this all they found there was a number of parts that were completely missing and this was something we hadn't seen before to this extent to find out what happened investigators must find the missing pieces which now lies somewhere in snow-covered fields and forests a close study of scandinavian airlines flight 751's engines reveals exactly which pieces are missing parts of this aircraft was shedding parts from both engines and then what you do is you go further in and you document everything and you try to find the root cause and see how it all comes together the missing pieces could hold the key to discovering why both of the planes engines quit within seconds of each other but they could be anywhere along the 15 kilometer route the aircraft covered during its short flight they must be found investigators use the flight data recorder to map the plane's journey and determine where engine parts may have fallen after scouring the snow-covered fields along the plains path the recovery team finds 500 fragments just a fraction of what's missing many are very badly damaged some of the titanium blades actually seem to have been on fire you have this titanium fire inside both engines both the right and the left engine and this titanium fire is a very unique occurrence you it's requiring very very high pressure and very high temperature for a titanium blade to catch fire investigators dig deeper into the cause of the engine trouble the left engine's fuel line is badly dented it was obviously hit by a fast moving piece of metal inside the engine the impact caused it to rupture this part got dislodged it went out and hit the fuel line and that fuel line cracked sprayed fuel onto the hot engine the engine was clearly coming apart during the flight it sounds serious the discovery explains the fire in the left engine and why so many pieces of it were found so far from the crash site but investigators are left wondering why the engines broke up in the first place [Music] a major clue comes from passenger and crew testimonies which told of repeated booming noises before the left engine caught fire the cockpit voice recorder picked up these sounds you can hear that then we could correlate that with when the damage occurred you can see that on the flight data recorder the sounds are familiar to investigators and leave no doubt the dc-9s engines began surging shortly after takeoff jet engines rely on a steady stream of air for combustion a series of fans move incoming air through various stages of compression but when that flow is disrupted fuel at the rear of the engines ignites violently and shoots forward that's the search you can have a small search and you can have a large search you can have the complete search on the whole engine it sounds serious this surge process was very violent so after a very short time we had an aircraft with two engines that could not be restarted that didn't generate any thrust basically you had a giant glider at that point [Music] a closer look at the fan blades from the front of the engines explains why they were surging they're badly dented [Music] the damage would have prevented them from effectively directing air to the rear of the engines this damage that twisted the fan blade started this process you got this disturbed air in the fan you got this rotating fan stall that then triggered this whole breakdown the compressor surge and then the whole process that led up to the dual engine failures but what exactly mangled the blades there are ways to tell if it comes from a stone rubber ice and so on you can see it on the shape of the damage the ice causes very specific damages it's sort of like a soft dent analysis of dent patterns on the fan blades is conclusive they were struck by ice now investigators want to find out where the ice could have come from weather data for the 24 hours leading up to the crash they know stockholm had been hit with rain and snow in the hours before flight 751 took off it was a situation with a temperature around zero degrees it was a drizzle snow rain in the morning they learned that the dc-9 arrived from zurich the night before with the fuel tanks more than half full they had quite a large amount of reserve fuel or diversion fuel in their wings the the fuel in the wing tanks were close to -20 degrees celsius the conditions that night were ideal for the formation of clear ice on the wing surface and here you had very very cold fuel on the top wing skin and as the temperature dropped during the night it went to snow and rain and finally snow so there was a layer cake ice at the bottom slush and snow on top but when 10 inches total on top of the wings in the morning responsibility for de-icing the plane ultimately falls on the captain rasmussen insists he was aware of the overnight build-up investigators wonder if the pilot did all he could to ensure his plane was completely free of ice rasmussen claims he instructed technicians to de-ice the plane thoroughly i didn't walk around with the aircraft it was cold it was frosty noticing that there was still frost on the wings the head technician ordered a second round of de-icing i was really convinced that the aircraft was clean and so was he so was he where are we the wings aren't quite done they've done the underside the cockpit voice recorder backs up rasmussen's [Music] the testimony yes yes it de-iced the aircraft once and looked at then i said once more and they did i have the second time in fact a total of 850 litres of fluid was sprayed on the aircraft but the fluid may have been faulty not potent enough to melt the thick layer of ice that had accumulated on the wings overnight [Music] technicians test samples of the fluid used to de-ice flight 751 if we found no discrepancies there was nothing wrong with any of the fluids used but when investigators interview the maintenance crew that worked on the plane they begin wondering if the de-icing team was thorough enough in their efforts the ground crew insists that after they sprayed the wing it appeared to be clean but that appearance was deceptive it looked perfect because the clear eyes on top of the fuel tanks you cannot see the clear eyes a technician inspected the front of the wing and found no ice he couldn't have known that there was ice further back out of his reach no provisions for stairs or anything that he could use to get up on the wing at the icing platform it looked shiny and nice couldn't see any ice on it but still there was maybe an inch of ice on top of it when the aircraft took off as soon as the plane took flight the ice became a problem on this aircraft the engines are positioned behind the wings and as the aircraft rotated and the wings bent in order to take the weight of the aircraft this ice in the wing roots loosened and it sucked right into the engine the ice damaged the fan blades at the front of the engines and ultimately caused them to begin surging nobody really expected this would happen it could happen but it did when ice breaks off the wings during flight it doesn't pose a problem for most aircraft but the placement of a dc-9s engines leaves them more susceptible to being struck the pratt and whitney engines on flight 751 were designed to withstand this type of ice ingestion something else must explain the disaster investigators know that the wrong reaction by a pilot can make surges worse they comb through the flight data to see what these pilots did when the emergency struck the first thing you do when you have a search if you recognize is that the search is that you reduce power captain rasmussen claims he did just that of course you just pulled the throttle back and then you have to the balance between the incoming fuel incoming air and now that was actually what i did but the flight data recorder tells a different story why is the engine power increasing it clearly shows that in the moments after the surge thrust was reduced but then seconds later was increased to beyond full power yeah it didn't add up because the the rpm was increasing to 110 percent and the throttle position was moving they shouldn't be the only thing that could move the trucks in clamp was the pilot's hand but if rasmussen didn't push the throttles forward something else did it would explain the captain's confusion as his engines began to surge as a pilot when you when you've gone through the training you've done all your emergency training you've been through the simulator and now you have a system that's doing something that you don't expect it's very confusing despite their relentless efforts investigators can find no possible explanation for the increase in thrust the frustrating part with the investigation was that we could not figure out why the system did what it did then almost two months after the accident the plane's manufacturer provides the answer the culprit is something called automatic thrust restoration [Music] it's brand new it automatically increases the thrust during the climb swedish authorities learn that automatic thrust restoration or atr was recently introduced as a safety feature on scandinavian airlines planes it existed because the faa had discovered some pilots were throttling back considerably while taking off and landing to reduce noise over residential neighborhoods the atr was designed to make it impossible for them to throttle back to dangerous levels so as soon as he powered back the system kicked in investigators learned that when rasmussen reduced power to clear his engine surge the system read this as a dangerously low power setting and pushed the throttles forward the increased thrust made the surging worse until the engines destroyed themselves the investigation concludes that the pilots had taken the right steps to clear the surge and prevent the catastrophe but the computer code which governs the atr undermined their efforts the strip of cereals and ones caused the throttles to move and caused the engines that were stalling because they already got too much fuel but even more few and they went into self-destruct both engines in a few seconds they're both totally destroyed [Music] the system was so new to scandinavian airlines that nobody there had even heard of it and it was confusing for everyone because we didn't know about the system we didn't have information on the system sas didn't know the system existed on their aircraft we hadn't bought that modification and it was sneaked in via another system because he didn't know about the atr rasmussen was unaware that he could only save his plane by switching it off news that the automatic thrust restoration was responsible for the accident proved both a blessing and a curse for captain rasmussen it eliminated any notion that he had made a mistake when i got that message i was really released it was like winning in the lottery it was you know because i was so happy because then i could explain why i was in that total corner confusion but the fallout would ultimately destroy a love affair and end a career on october the 20th 1993 the swedish accident investigation board releases its report on the crash of flight 751 it determines that the actions of captain rasmussen and first officer sedermark contributed to the safe outcome of this incident and although investigators question captain per homebug's decision to enter the cockpit in the first place they do praise his contribution this crew flew until they stood still on the ground they never gave up they never gave up they didn't give an inch the investigators put much of the blame for the accident on scandinavian airlines because their procedures for checking for clear ice were inadequate i believe it's a compressor stall the report also condemns the fact that the pilots didn't know about the automatic thrust restoration and how it would act in a surge situation if the atr system hadn't been there if the trials hadn't moved forward there wouldn't have been an accident it was a bit strange that we didn't have all the documentation available to us so we knew what we could expect if something like this would happen in the wake of the crash scandinavian airlines started training its pilots how to use the atr system they also implemented steps to ensure airplanes don't take off with clear ice on the wings we changed all the procedures we provided stairs for the mechanic and they made it a requirement to go up on top of the wing and touch it with your hand to verify after the icing after healing from his injuries first officer ulf sedermark returned to the cockpit i didn't feel the responsibility that that i wouldn't be able to do my job again whatever happens i know that i i still can see things for what they are and i still love doing my job and if something bad happens i can deal with it but stefan rasmussen's return proved far more difficult said power after i'd heard from a high skilled psychologist we talked about getting in the air again he knew that that would be a hard decision to take gear up fire drill [Music] after time in the simulator rasmussen couldn't regain confidence in his plane sorry guys in a disaster this situation in a in a crisis is that you have optimized the year teamwork between man and machine i really felt that that i didn't trust the aircraft pilot stands to take the responsibility before all that went wrong too much of the glory and also too much of the responsibility [Music] with the right counselling about 90 percent of pilots involved in an accident are able to continue flying [Music] even though captain rasmussen received treatment his career ended with the crash of flight 751 taking that decision to leave aviation as pilot was like [Music] having you your highest love and um come to that conclusion conclusion that um that you have to kill her [Music] i had many hours many missions of happiness in an aircraft and i loved my passengers a lot my aircraft so much so i said that's it i never regret it never and i think i was right [Music] you

Channel: On The Move

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Keywords: on the move, cars, planes, trains, documentary, documentaries, full length documentaries, plane documentary, mayday series, mayday, plane disasters, airport, runway, plane pilot, pilot, hd documentary, 2021 documentary, united airlines, plane crash, air accident, air crash, air disaster, plane accident, air emergency, plane disaster, plane emergency

Id: XAY_splkS9A

Length: 45min 3sec (2703 seconds)

Published: Wed Jul 28 2021