Tiny Failure That DOOMED Flight 120 | Survivors Accounts | FULL DOCUMENTARY

Summary

China Airlines Flight 120 faced a terrifying ordeal when moments after landing safely and shutting off its engines, the aircraft erupted into flames. Miraculously, all 165 passengers and crew managed to evacuate without injuries. The investigation into this near disaster exposed a critical maintenance mishap where a missing washer led to a fuel leak and eventual fire. This event underscored the importance of meticulous attention to detail in aircraft maintenance to prevent potential tragedies.

Highlights

• Miracle on the runway as all passengers of Flight 120 escape unharmed. 🙌
• The investigation reveals that a missing washer led to the catastrophic fuel leak. 🧐
• Boeing initiates a worldwide redesign effort to enhance 737 safety. 🌍
• A critical bolted part, unassuming yet vital, wreaks havoc by puncturing a fuel tank. 🔧💥
• Heroic efforts by the crew ensured a rapid evacuation under dire circumstances. 🚒

Key Takeaways

• Always double-check your work! A tiny washer caused a massive fire. 🔍
• Airplanes are incredibly resilient, as shown by the miraculous survival of Flight 120's passengers. ✈️
• Even minor aircraft maintenance can have major consequences if done incorrectly. ⚙️
• The incident led to important safety redesigns for all Boeing 737 aircraft. 🛡️
• Quick thinking and training of the crew and passengers helped avoid any casualties. ⏱️

Overview

In an incredible sequence of events, China Airlines Flight 120 narrowly avoided disaster when it burst into flames after landing in Okinawa, Japan. The quick actions of the cabin crew coupled with the passenger's cooperation allowed for a timely evacuation with zero casualties. This event shed light on the remarkable resilience of both technological and human elements within aviation.

As investigators delved into the wreckage, they uncovered that the fire was caused by a missing washer during maintenance, which allowed a vital part to come loose. This part punctured a fuel tank, leading to a severe fuel leak and subsequent inferno. The incident highlighted how even the smallest oversight can lead to major incidents in aviation.

In response to this incident, Boeing undertook a global effort to redesign the faulty component across all 737 aircraft, ensuring enhanced safety standards. This move aimed to prevent such an incident from occurring again and served as a stark reminder of the critical nature of precision in aviation maintenance and engineering.

Chapters

• 00:00 - 01:00: Introduction and Incident Overview The chapter titled 'Introduction and Incident Overview' begins with a tense situation involving a plane that is about to be evacuated. With both engines on fire, a sense of urgency and panic is prevalent among the 157 passengers struggling to escape the burning 737 aircraft. The event is described as going up like a bomb. Amidst the chaos, investigators focus on analyzing the incident, scrutinizing every small detail to understand the cause and sequence of events that led to the inferno.
• 01:00 - 04:00: Flight Preparation and Takeoff This chapter discusses the critical discovery in the investigation of the failure that affected China Airlines Flight 12. The investigation revealed a significant oversight in risk assessment, resulting in potential danger to more lives. The chapter captures the urgency and introspection of the investigators as they grapple with unexpected risks that have serious implications.
• 04:00 - 07:00: Events Leading to the Fire The chapter begins with China Airlines Flight 120 being on its final approach for landing at the Okinawa Naha Airport. A notification is made to the passengers to cooperate with the flight attendants as they prepare the cabin for landing, setting the stage for the events that might lead to a fire.
• 07:00 - 12:00: Evacuation and Immediate Aftermath The chapter is titled 'Evacuation and Immediate Aftermath'. It begins with the introduction of the flight captain, 47-year-old Yuin Cou, and the first officer, 26-year-old Sang Tawe. Together, they have accumulated over 8,500 hours of flight experience. The narrative mentions the technical details of their approach, noting a ceiling of 1,000 feet. The focus then shifts to the aircraft, a Boeing 737, described as a routine model for landing due to its popularity and familiarity among pilots. The chapter does not provide further details regarding the evacuation or aftermath, focusing instead on the context leading up to these events.
• 12:00 - 16:00: Investigation Begins The chapter titled 'Investigation Begins' focuses on a short domestic flight from Taiwan to Okinawa, Japan. The airplane carries 157 passengers and eight crew members on a journey lasting about one hour. Among the passengers is Jim Caruso, a medical examiner for the US Navy stationed in Okinawa, who is traveling with his family. The chapter likely sets the stage for an ensuing investigation, involving a mix of characters who are part of or affected by the events on the flight.
• 16:00 - 24:00: Focus on Fuel System and Electrical Issues The Caruso family was returning from a vacation in Brisbane, Australia, after spending 12 to 14 days there. They hoped to be home for lunch. Living in Okinawa has provided them with ample opportunities to travel extensively throughout Asia, visiting China, Hong Kong, Mainland Japan, and Korea. They have utilized their location to explore the region, with Naha Airport located at the southern end of Okinawa on the shore of the East China Sea.
• 24:00 - 31:00: Breakthrough: Discovery of the Bolt The chapter titled 'Breakthrough: Discovery of the Bolt' describes the process undertaken by pilots as they prepare for landing over the China Sea. It details the specific aeronautical maneuvers such as deploying flaps and slats to maintain lift at reduced speeds. This allows the aircraft to descend safely by extending the wing area, ensuring sufficient lift during lower speed flight.
• 31:00 - 36:00: Tracing the Origin of the Bolt The chapter 'Tracing the Origin of the Bolt' discusses the complexities of landing an aircraft, particularly focusing on the phase where the plane slows down for landing and the final touchdown. The passengers are eager to land and return to their normal lives.
• 36:00 - 42:00: Connection to Previous Incidents This chapter discusses the process of landing an aircraft and the subsequent taxiing to the terminal. The focus is on the expectation that landing is the most challenging part and once completed, the rest, including the taxi, should be routine. There's also a mention of 'previous incidents', suggesting a link to past experiences with non-routine landings or taxi processes.
• 42:00 - 53:00: Final Investigation and Conclusion The chapter titled 'Final Investigation and Conclusion' describes the final moments of a flight handled by China Airlines as they complete their journey. The pilots proceed with parking the plane and shutting down the engines by moving the engine start levers to the cut-off position. The action of shutting down the engines signifies the end of a tense and strenuous flight, allowing the pilots to finally relax. With the engines off, the risk of a catastrophic event diminishes significantly. The chapter emphasizes the relief experienced by the pilot, knowing that the possibility of any serious incident occurring post-landing is almost nonexistent.

Tiny Failure That DOOMED Flight 120 | Survivors Accounts | FULL DOCUMENTARY Transcription

• 00:00 - 00:30 what is going on out there everyone we're about to evacuate the plane remain calm I certainly knew that with both engines on fire it was not going to go well 157 passengers rush to escape a burning 737 the to it goes up like a bomb in the struggle to explain The Inferno the smallest Parts come under intense scrutiny the analysis leads to a
• 00:30 - 01:00 stunning Discovery where is it there was a true breakthrough in the investigation the failure that doomed China Airlines flight 12 is putting more lives in danger every day we really didn't anticipate that there's a risk and it bit us hey hey
• 01:00 - 01:30 [Music] China Airlines flight 120 is on Final Approach for landing ladies and gentlemen we're about to begin our descent into okanawa naha Airport please give the flight attendant your full cooperation as it prepare the cabin for a landing
• 01:30 - 02:00 the captain is 47-year-old yuin cou what's a weather for approach CL ceiling ,000 ft Wednesday AP the first officer is 26-year-old sang tawe the pilots have more than 8,500 hours of flight experience between them almost straight down the pipe sir Landing this Boeing 737 should be routine the 737 is probably the most popular airframe in the world it's flown by most Pilots as they start out in their careers
• 02:00 - 02:30 it's a short-range domestic airplane flight 120 is a 1-hour journey from Taiwan to the southern Japanese island of Okinawa this morning there are 157 passengers and eight crew on board put your Trail up and passing your seat belt Jim Caruso is a medical examiner for the US Navy stationed in Okinawa he and his family are on the last leg of a long trip home from
• 02:30 - 03:00 vacation the family was returning from Brisbane Australia uh we had done probably 12 or 14 days on vacation and we were hoping to be home for lunch living in Okinawa has given the Caruso the chance to travel through much of Asia we got to see China Hong Kong Mainland Japan Korea we have made use of our location to experience the area naha airport sits at the southern end of ok hour on the shore of the East
• 03:00 - 03:30 China Sea the pilots reconfigure their plane as they slow down and descend for landing let's go to flaps 25 flaps 25 they deploy flaps from the wings back Edge along with slats from the front edge these devices keep the plane Airborne at lower speeds when we start configuring we begin to put out flaps and slats which extend the area of the wing and give us more lift and allow us
• 03:30 - 04:00 to fly slower and of course the landing and touchdown itself are the most complicated part of the flight they're now less than a minute from the runway okay honey have to remain in your seat I think everybody was looking forward to Landing getting off the airplane and getting back to regular [Music] life 13 20
• 04:00 - 04:30 10 it's a textbook [Music] Landing clut them once you're landed you figure your your home free the taxi is usually routine after landing checklist
• 04:30 - 05:00 speed breaks all that's left for the China Airlines Pilots is to park the plane engine start levers engine start levers cut off with the engines off they can finally relax the pilot is relieved he's no longer at risk uh catastrophic event after you're parked is almost non-existent seat belts seat belts
• 05:00 - 05:30 off the biggest challenge ahead of you from there is making sure you can get through customs no one ever expects anything to go wrong especially once the engines are turned off but one passenger has noticed that something's not right my wife was next to a woman who made some sort of exclamation towards the engine on the right side Wasa
• 05:30 - 06:00 what's going on there was some smoke coming from that engine that was the first sign that something was out of the ordinary what is going on out there anti ice a star switches off the pilots are finishing the shutdown checklist transponder tcast hey what is it what's happening just when they thought they were safely pared marked
• 06:00 - 06:30 cockpit ground number two engine fire a radio call alerts them to an urgent danger their plane is on fire attention crew on station attention crew on station bringing the flight attendants to their station tells them that what might likely be next would be an emergency evacuation dnasty 120 we are calling a fire truck stand by uh we have wheel fire please tab crew prepare for evacuation
• 06:30 - 07:00 prepare for evacuation everyone remain calm we're about to evacuate the plane remain calm fear begins to spread throughout the cabin Outside the Fire is getting worse the engine on my side also started smoking and flaming so now we had both Wings on fire and at that point people began to panic remain calm no
• 07:00 - 07:30 pushing I had no idea at that point how things would play out but I certainly knew that with both engines on fire it was not going to go well parking brakes Sak brakes slap lever the pilots know they need to get their passengers off the plane before Flames reach the fuel tanks but they can't open the cabin doors yet engine fire warning switches
• 07:30 - 08:00 override they must follow an evacuation checklist we want the pilots to grab the list simply read it and do it no wondering what step is next because the sequence of the steps are very important and rotate everybody remain calm do not bring your luggage of personal belongings seconds feel like hours as the crisis escalates finally the pilots are ready to open the
• 08:00 - 08:30 doors evacuation required now [Music] required no pushing no pushing please keep moving forward but it will take time for all 157 passengers to make it to the exit George ishizaki is watching the unfolding disaster from inside the airport terminal I just happen to have my camcorder with me I thought oh oh my God what is
• 08:30 - 09:00 happening keep moving forward with the fire growing more intense time is running out let's go let's go we were quite a ways back from any exit since the overl exits were were useless so my uh Focus was really to get the kids moving forward and off the aircraft fing turn is
• 09:00 - 09:30 fil fire go ahead go ahead all right Jim Caruso stays behind to help other passengers get off the Burning Plane I don't actually remember hesitating it may have been a little difficult to make that decision since the kids were already moving forward okay no pushing keep moving forward the smoke actually started building and then that's when everything
• 09:30 - 10:00 started happening really [Music] quickly Jim Caruso is separated from his family the Heat and smoke are getting worse he hears a cry for help the woman behind me pointed towards the overhead bin I was concerned if she was pointing towards Flames coming in I looked up and I saw a pair of crutches
• 10:00 - 10:30 everybody was just sliding down the slides and once they got on the ground they were just scrambling once the smoke and fire started building the cabin became rather warm I do recall some of the windows actually cracking from the heat finally they make it to the exit [Music]
• 10:30 - 11:00 the plane has been burning for close to 3 minutes it could explode at any moment Captain all passengers are evacuated you're the last one got to get out of here typically the captain will stay until
• 11:00 - 11:30 everybody's off and he will verify that the airplane is empty the pilots have put their passengers safety first but now it may be too late for them going to have to climb up to the window you first all 737 cockpits are equipped with an emergency escape rope it's designed to help Pilots exit through the side window but it's no easy maneuver exiting the airplane is more difficult than it sounds it's a relative small window
• 11:30 - 12:00 going down the Rope has a [Music] risk then w w you felt a huge Kaboom I've never felt anything like that we actually could feel the ground shake
• 12:00 - 12:30 passengers run to safety as a fiery explosion engulfs the plane they just escaped the fate of the pilots is still unknown as I look back after the first explosion I recall two members fast roping as it were out the cockpit the force of the blast overpowers the first officer he dropped down from the height of the cockpit window onto the ground incredibly he's able to get up and away from the
• 12:30 - 13:00 Flames the captain quickly follows it was good that he did that because the fire just gutted the airplane more explosions Rock the airport the fuselage I guess melted the back half just kind of fell to the ground finally fire trucks arrive on scene everybody had exited the aircraft at that point and was gathering in the terminal
• 13:00 - 13:30 it was a huge relief to have the kids and my wife and I together we certainly were looking back at the aircraft again in amazement fire on an airplane can quickly become lethal incredibly on flight 120 all 165 people on board have escaped unharmed I've never heard of any evacuation where somebody wasn't hurt to get this many people off in such a dire circumstance in a very short period of
• 13:30 - 14:00 time with no injuries is miraculous if there's a next time passengers may not be so lucky pressure to figure out what happened falls on an international team of air crash investigators okay let's get to work they need to explain how an airliner that had landed safely and turned off its engines suddenly burst into
• 14:00 - 14:30 flames we have no clue we do not know what happened we try to find out from the wreckage remain still on the apron normally fires occur in Flight uh perhaps during taxi sometimes but rarely in a parking spot after the engines are shut down the challenge for investigator is most of the evidence will be destroyed by the fire
• 14:30 - 15:00 across the globe there are more than 5,000 Boeing 737s in service there's a 737 taking off and Landing uh every 3 or 4 seconds in the world if the plane has a design floor that somehow leads to uncontainable fire countless passengers could be at risk we aware that the 737 is probably the most popular airliner out there so there's a reason once an accident occurs to try to figure out what happened pretty darn
• 15:00 - 15:30 quickly the search for flight 120's black boxes begins immediately one of our main goals initially is to try to find the cockpit voice recorder and the flight data recorder these are important because a lot of times they tell us what happened but investigators know that after such an intense fire there's a chance the blackbox D will be
• 15:30 - 16:00 lost they need other leads good investigators don't rely totally on flight data recorders for instance or cockpit voice recorders because they can be destroyed so we rely on witnesses to tell us their impression of what happened well we taxi It Off The Runway down the apron to our sun parking spot once we pared we shut off the engines and sometime after that we heard the aircraft TOS on fire we needed to know what type of fire it was what the ignition Source would be
• 16:00 - 16:30 what the fuel source would be those were the areas of our main questioning right off the bat I radio the controller letting him know we had a wheel fire investigators know that if a wheel caught fire on flight 120 there's more than one possible cause a deflated Tire can result in burning rubber overheated brake pads could potentially ignite hydraulic fluid in a wheel well an aircraft there are a lot of hydraulic lines going to the
• 16:30 - 17:00 landing gear assemblies and things like that hydraulic fluid is very flammable if a hydraulic leak occurred and it happened to drip onto a hot break for instance well there you go hey what is we have me fire if the pilots are right about where the fire started investigators should be able to find proof they examin the plane's right side wheel well and landing gear
• 17:00 - 17:30 assembly they find scorched wreckage but not enough to convince them that this is where the fire began once we were able to closely examine that part of the aircraft we were very confident that a wheel well fire per se did not occur the seat of the fire seemed to be forward and a little bit to the right of the wheel well area it seems the pilots were mistaken about the origins of the fire where it started remains a mystery solving that mystery may have just
• 17:30 - 18:00 become easier investigators have recovered the plane's black boxes the Japanese team they retrieved the both CVR and FDR let's get working on the FDR immediately on Modern 737s the flight data recorder has thousands of parameters data bits that come in to the recording device itself it will take time to download Lo and verify all the
• 18:00 - 18:30 [Music] data meanwhile the charred fire scene continues to challenge investigators with all this heat damage it's nearly impossible to tell where the fire started they're almost certain the fire began on the right side of the plane as Witnesses reported but where exactly wait a second scorched wires provide a promising new lead what do you think did
• 18:30 - 19:00 an electrical fire destroy flight 120 serious electrical failures are rare but not unheard of in 1998 the cockpit of Swiss Air flight 111 began filling with smoke shortly after takeoff the pilots tried to make an emergency landing in Halifax Canada they never made it their plane disappeared into the Atlantic Ocean killing all 229 people on board investigators found that an electrical
• 19:00 - 19:30 fault in the entertainment system almost certainly sparked the fire that doomed the plane okay see what we got if the fire aboard flight 120 was caused by faulty wiring investigators may now be able to confirm it they've successfully downloaded the blackbox data any electrical problem or failure in any onboard system should show up in the data almost every system on the
• 19:30 - 20:00 aircraft is recorded its status is recorded uh so we looked very quickly through these hundreds of electrical possibilities and we found nothing it wasn't electrical the analysis comes up empty at that time we can root out some wheel fire or some other electrical fire investigate turned their attention to the aircraft's right
• 20:00 - 20:30 engine in Flight the cfm56 power plant generates internal temperatures of more than 2,000 de F hotter than molten lava could an engine Fire have sparked The Inferno we of course looked at the engines very carefully the right engine especially because there was a lot of fire damage around it it was fairly easy to look inside the engine and and examine the core so to speak where all the damage in
• 20:30 - 21:00 an engine failure usually occurs and we we found nothing [Music] wrong the engine was damaged externally but not internally so we eliminated it as a possible Factor what could have burned this entire plane down the investigation has hit a wall the cause of the catastrophic fire remains unknown while every day
• 21:00 - 21:30 thousands of 737s continue to fly there's growing pressure on investigators to find the answer we knew we had a little bit of a detective work ahead of us and we pressed on the video capturing the fiery destruction of China Airlines flight 120 could provide investigators with Clues to what started the fire
• 21:30 - 22:00 wow the footage reveals just how quickly the flame spread through the passenger jet but for investigators the most important clue is missing the recording hasn't captured the critical moment the fire started from the video we can only understand there was fire and the location of the fire and it seems that something feeding to the fire but we cannot understand
• 22:00 - 22:30 why investigators widen the search for leads what did you see the effort pays off when an airport ground worker provides a critical detail gramp worker on the right side of the aircraft said very distinctly that he saw a liquid running down the Leading Edge of the right wing before fire broke out
• 22:30 - 23:00 thanks fluid leaking from this part of the wing of the aircraft can be only one thing jet fuel the 737 holds 4,390 Gall of fuel much of it in tanks located inside the plain's two massive Wings when we figured out that a actual fuel leak had occurred it was a breakthrough a true breakthrough in the invest instigation we now needed to know why it
• 23:00 - 23:30 originated we know the fuel was leaking but from where fuel line finding solid evidence amongst the burnt remains of the plane's fuel system won't be easy the Boeing 737800 has high pressure pumps inside the wing they deliver 200 Gall of fuel
• 23:30 - 24:00 per hour to the engine all that fuel flows through flexible pipes could one of those fuel pipes be the culprit fuel lines are probably in a sense the most vulnerable part of a fuel system they take bends and sometimes they're exposed where they could get knocked or punctured by something so we tried to trace the entire fuel system of the aircraft it's another dead end it wasn't a fuel
• 24:00 - 24:30 eyes none of the fuel lines are ruptured we had a lot of fire damage but the fuel lines that We examined uh seem to be intact and functional investigators still can't explain the fire they know enough fuel leaked from the plane to feed the Flames but they don't know where it came from Once We eliminated fuel lines per se as as a possible problem pretty much the only thing out
• 24:30 - 25:00 in that area that could have gone wrong is a leak in the fuel tank itself the plan's fuel tanks are made from aluminium alloy and designed to withstand the rigors of flight for years they should never crack or leak examining them presents one of the most difficult challenges yet they hope a tool called a b scope will do the trick it's a small camera that can peer into tight spaces it gives them a unique view inside the
• 25:00 - 25:30 plane's right-wing fuel [Music] tank what it reveals changes the entire course of this investigation whoa would you look at that all of a sudden it clear as a bell and we saw this bolt sticking out of the fuel tank itself where the bolt came from is a complete m history but it has ruptured the tank
• 25:30 - 26:00 right where the groundw worker spotted leaking fuel it's hard to describe how significant this was I mean this was the core of the investigation now we knew what happened the rest of the investigation was trying to figure out why this occurred a punctured fuel tank was the cause of one of the most infamous air crashes in history a supersonic Air France Conor burst into flames on takeoff after
• 26:00 - 26:30 running over a piece of metal debris on the runway did a similar scenario lead to the total Destruction of China Airlines flight 120 okay we need to cut into this Wing investigators need to get a closer look at the mysterious bolt that made a hole in the fuel tank the investigator in charge said yep Now's the Time to start cutting into that thing [Music]
• 26:30 - 27:00 [Music] [Music] okay got it now they need to figure out where the bolt came from they study schematics of the 737 world Wing
• 27:00 - 27:30 structure we went back to the drawings and went back to things like maintenance records to try to figure out exactly what it was they soon get their answer a down stop assembly the down stop assembly is part of the slat mechanism on the Wing's Leading Edge Let's to flaps 25 flaps 25 Pilots extend flaps and
• 27:30 - 28:00 slats during every takeoff and Landing the down stop is fixed to the end of a track that slides back and forth the device prevents the slats from moving too far forward the down stop is there quite frankly to stop it when it reaches its maximum deployment length um if it didn't exist then there would be no way to retain the slant on the
• 28:00 - 28:30 aircraft investigators have identified the piece that penetrated the fuel tank they know it's not from another plane like the runway debris that caused the Concord disaster but they have other important questions that need answers we had the assembly we knew it punctured in the tank our next step was trying to figure out how this could possibly have occurred
• 28:30 - 29:00 investigators pour over Boeing service documents to learn more about down stop assemblies on the 737 they make a surprising discovery this has happened before and it's happened more than once there have been two previous instances of this device coming apart and causing minor few leaks and this was the first instance of an actual
• 29:00 - 29:30 destructive fire in both previous instances parts from a down stop assembly punctured a fuel tank just like on flight 120 clearly they knew it was a problem Boeing was so concerned about the problem it issued a special work order to secure the down stop assembly on all 737s worldwide the solution that Boeing had recommended was to remove the nut from
• 29:30 - 30:00 this particular device and install some thread hardening material and then you reinstall the nut it hardens in place what if the work water on this plane was never completed investigators review the Boeing work orders if the plane that burned in Okinawa was never fixed that could explain the accident we're trying to figure out when is the last last time is anybody touched that assembly
• 30:00 - 30:30 but according to the records the proper work was carried out very recently we discovered that this particular component this down stop had been manipulated only a couple of weeks or so prior to the accident just doesn't make sense investigators can see that the nut on the down stop assembly is still attached it seems that the work order to replace it was completed just as the record show so what went
• 30:30 - 31:00 wrong that's the weird part that we we want to figure out at that time they examine the down stop assembly from flight [Music] 120 they check all the component parts finally they spot something we decided to count parts and lo and behold a a washer was missing [Music]
• 31:00 - 31:30 where is it there's supposed to be a washer right behind the Nut could a single missing washer have played a role in the accident it seems unlikely but investigators can't rule it out they need to find the washer we thought initially that the washer may have somehow gotten inside the fuel tank but that's not the case at All We examined very carefully the rest of the wing we found that particular washer in the
• 31:30 - 32:00 Leading Edge assembly of the wing just laying in there loose the washer is a fit recovering the missing washer raises a puzzling question the nut was on there and it was torqued down correctly but there was no washer on it at all how did the washer become detached from the bolt but not the nut if the nut is still on the ball why there is something between where fall
• 32:00 - 32:30 off it seems like an impossibility and yet somehow it happened the flight 12 fire investigation heads to Taiwan and the headquarters of China Airlines investigators hope to shed some light on the mystery of the detached washer I appreciate you making the time we went to China Airline to ask them to
• 32:30 - 33:00 demonstrate how they do the Menace work do you think you can show me how you completed this repair on a down stop assembly sometimes maintenance records don't tell you the true story they can tell you that according to somebody a Manus procedure had been done correctly but to get a better story you have to actually watch the procedure being done a mechanic demonstrates how he performed the down stop repair you won't be able to see much of what
• 33:00 - 33:30 I'm doing performing maintenance on this particular down stop is a little tricky mechanic is going to be in a very restricted visual area so he's going to have to work with his hands he's going to have to feel the apparatus after applying glue you put the bolt into
• 33:30 - 34:00 place you can imagine that you are under the wing and you cannot see [Music] [Applause] it sorry just dropped it don't worry it's it's easy to pick up again
• 34:00 - 34:30 it's an eye openening demonstration that's how it's done thank you you have been very helpful it's not very easy for them to confirm they finish their job and uh everything is in order there records show that the work order repair was the only time mechanics ever serviced the down stop in the history of the accident airplane there's only one possible
• 34:30 - 35:00 explanation for how the washer found in Okinawa came loose it fell off during the maintenance procedure in Taiwan could have just slipped off the gentleman's fingers when he was trying to install it it could have stuck to the nut and then fallen off just before he touched them together a lot of things could have happened the bottom line is uh the washer was not
• 35:00 - 35:30 [Music] there but understanding what happened to the washer still leaves investigators scratching their heads the down stop assembly had a well tightened nut that was also glued to the bolt how could it fall out and how did this piece start a raging fuel fire that destroyed a $70
• 35:30 - 36:00 million airplane all right now let's test it without a washer investigators experiment with the suspicious part from flight 120 to see how it performs without the washer the design of this assembly requires each component to play a specific role so any piece that is not reinstalled is critical they make a stunning
• 36:00 - 36:30 [Music] Discovery the small washer is the only thing preventing the unit from falling out of its Mount without the washer it fails we discovered that the nut and the bolt was smaller than the rest of the assembly and that the washer was a required item this is an example of an intact uh down
• 36:30 - 37:00 stop assembly we'll take the nut off take the washer off the nut back on like they did in Taiwan and now you'll note that the assembly itself is pretty ineffective it falls apart uh without much problem at all finally it's clear why the down stop assembly was able to fall out of the slat track how it punctured the fuel tank is
• 37:00 - 37:30 the final piece of the puzzle but investigators believe the design of the slat mechanism itself May hold the answer the engineers are designing these aircraft they take into consideration maximum space utilization and for the design of a Leading Edge slant they came up with something called a can the slat can is the area inside the wing that houses the moving track the can is a void that extends into the fuel tank and allows for the
• 37:30 - 38:00 device that operates the slat to move in and out the space inside the slat can is tight just big enough for the sliding track a foreign metal object taking up any space inside the can would be an accident waiting to happen it would render the entire assembly uh not only non-functional but dangerous [Music]
• 38:00 - 38:30 China Airlines flight 120 157 passengers eight crew investigators believe they finally understand the sequence of events that led to a devastating fuel fire in Okinawa it all begins weeks before the accident with a botched repair to a critical
• 38:30 - 39:00 component a single missing washer turns a down stop into a hidden danger a bolt that can work its way loose over time washers really aren't supposed to hold things together but this washer did because of its design 6 weeks after the failed repair please give the flight attendance your full cooperation as it prepare the cabin for landing a routine descent into
• 39:00 - 39:30 Okinawa requires the pilots to deploy the flaps and slats as usual inside one of the track cans on the right wing the loosened down stop is just barely holding on touchdown is enough of a jolt to finally knock the down stop out of its track the unsuspecting crew soon retracts the flaps and
• 39:30 - 40:00 slats the plane's powerful Hydraulics move the slat track back into the can but now the down stop bolt is in the way the track pushes it to the back of the can and then straight through puncturing the rightwing fuel [Music] tank a hole in a fuel tank caused the leak the plane would have been carrying thousands of liters of fuel as the plane
• 40:00 - 40:30 taxis the engine exhaust is powerful enough to disperse the leaking fuel it can't come into contact with the hot tail pipe or brakes after landar Shu but once the pilots Park and shut down the engines the situation instantly becomes much more dangerous Eng start levers and you start levers cut off the leaking fuel starts dripping directly onto the scorching hot tail
• 40:30 - 41:00 pipe what is going on out there the leaking jet fuel ignites on contact the speed of the development of the fire is incredible obviously fuel Burns very well and it goes up like a bomb everybody remain C the cabin crew's professional conduct gets 157 passengers off the plane in just 1 minute and 42 seconds
• 41:00 - 41:30 the naha airport fire leads investigators to a striking realization the repair that was ordered actually caused the fire it was kind of ironic the Taiwanese maintenance procedure was to prevent an accident and in essence the procedure had a lot to do with why this particular accident happened it's a great study and unintended consequences we really were trying to fix a problem we really didn't
• 41:30 - 42:00 anticipate that every time we handle uh a maintenance piece like this there's a risk and it bit Us in the wake of the naha airport Inferno Aviation authorities around the world order the inspection of the entire fleet of 737s in the us alone 21 planes are found to have the same defect all of them at risk of a catastrophic fuel leak and fire Boeing takes immediate action it redesigns the down stop mechanism and ensures that the improved part is
• 42:00 - 42:30 installed on each and every plane Boeing made the changes necessary to ensure that the accident didn't occur again took a little time as it normally does to get to the final resolution of it but they did what they needed to [Music] do