Mayday Air Crash Investigations - S10 E02 - The Heathrow Enigma
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00:00January 2008. The Boeing 777 is the gold standard for commercial aviation.
00:09For more than 10 years, the plane has logged 2 million flights without a single major accident.
00:15But less than a thousand feet above London's Heathrow Airport, all that changed.
00:20Hey, I can't get power on the engines.
00:23What do you mean?
00:25It's not giving me power.
00:27This can't be happening.
00:29I thought if I don't do anything, then everybody will die.
00:34Mayday! Mayday! Speedbird! Speedbird!
00:42Whatever brought down one of the world's most technologically advanced airplanes
00:47can't be found at the crash site.
00:50They had the pilots, they had the passengers, they had the aircraft, they had everything there
00:55except the thing that caused it.
00:57That had disappeared as if by magic.
01:03Mayday! Mayday!
01:04Mayday!
01:05Mayday!
01:06Payday!
01:30hour journey from Beijing to London. Captain Peter Burkill has made this trip many times
01:35before.
01:36I was operating that route a lot. It was one of my favorite flights because it was daylight.
01:42You could see the views the whole way along the route.
01:46Burkill and First Officer John Coward both have thousands of hours flying the 777 under
01:51their belts.
01:52It's a joy to fly. She handles really well. She's got modern equipment. The computers
01:59are easy to use. She's got the range, the ability to do short haul as efficiently as
02:04long haul.
02:05For these two, as for many pilots, a day on the job consists of sitting in the cockpit for
02:10long hours as computers fly the plane. Powered by two massive Rolls-Royce engines, the Boeing
02:17777 is one of the safest planes in the industry. Nick Harris is flying back to London after
02:26a business trip to China.
02:27The good thing was that it seemed to be that we were coming in early into Heathrow. I was
02:31looking forward to getting home to see the family.
02:35Flight 38's destination is Heathrow Airport, one of the busiest international airports in
02:40the world. Nestled in the southwest corner of London, it's bordered by the A30 motorway.
02:49People who live in the nearby neighbourhood of Hounslow are well accustomed to the sound
02:52of jets taking off and landing.
03:01The area's tightly packed houses come into distant view for British Airways Flight 38.
03:12The autopilot is in control as the crew lines up with runway 27 left. As it nears the ground,
03:19the plane is buffeted by some high winds.
03:22Just a little turbulence. It's the first wrinkle in an otherwise smooth journey.
03:28It's not me. It's the autothrottles doing their thing.
03:37We were picking up wind gusts of about 20 to 30 knots, and we were fully aware that the
03:44autothrottles would be able to cope with that, so they'd be moving up and down quite a lot.
03:49You may want to keep the autopilot on a little longer than usual until the wind comes down.
03:53Will do. In turbulent weather, the autopilot can make
03:59faster adjustments to keep a plane level than the pilots.
04:021,200 feet above ground. I'll have to turn that off for now, sir.
04:06Sure. Thank you.
04:07Two minutes before landing, Coward takes over flying the plane.
04:11You have control?
04:15Just as the two pilots had planned.
04:17I have control.
04:23I had a few seconds to spare before clearance to landing, and I was just tidying up my map charts.
04:31Speedbird 38. Prepare to land. 27 left.
04:38Clear to land. 27 left. Speedbird 38.
04:42I remember looking out to see if our gate was available.
04:48500 feet. 500 feet.
04:52Stable?
04:54Well, sort of.
04:56Suddenly, there's a problem.
04:57Pete, I can't get power on the engines.
05:00It's not giving me power.
05:03What's going on?
05:04What do you mean?
05:06I was looking at the engine instruments, and they didn't make sense to me because we were asking for full power,
05:13but the engine instruments were not giving us any power at all.
05:19What's going on?
05:21Flight 38 is crippled in the worst way imaginable.
05:24Well, it looks like we have double engine failure.
05:26With neither engine providing enough power, the jet won't make it to the airport.
05:32With 152 people on board, Flight 38 is falling toward London with only seconds until it hits the ground.
05:46This can't be happening. This is one of the most modern jets in the world.
05:52In the cabin, there's no indication that anything's gone wrong.
05:57On approach to land, everybody seemed relaxed in the cabin.
06:01We're just looking forward to landing.
06:04Airspeed low, airspeed low, airspeed low.
06:11And now I was looking at our impact point.
06:16I could see a set of buildings around the Hatton Cross area and a petrol station.
06:22I just knew if we were hitting those, then it was certain 100% fatalities.
06:27At that point, I felt the weight of my four bars on my shoulder.
06:35I am the captain. If I don't do anything, then everybody will die.
06:38This close to the ground, Burkill doesn't have many options.
06:46He could take back control of the plane from Coward, but doesn't think that's the right move.
06:50First decision really was to not take control. I remember looking over at John. He was still flying the plane.
06:58Well, good. He's doing a good job. He's doing what I need him to do.
07:00Burkill knows that even if they managed to clear Hounslow, the jet could still smash into the busy A30 motorway or the antennas at the edge of the airport.
07:09I thought about raising the gear. That's the biggest drag on a commercial jet, but I needed the gear to crash on.
07:20We were going to impact, and that was going to take the brunt of the impact, so I had to leave the gear there.
07:26With a crash imminent, Burkill has only one move left, but it comes with enormous risk.
07:32I knew I had about 15 seconds to make a huge decision. I needed to get past those buildings.
07:43It was obvious to me that I needed to raise the flaps.
07:48Retracting the flaps will reduce drag, but also lift. The plane will fly further, but drop faster.
07:55Burkill must determine which is more important.
07:57I wanted to discuss it with the crew, but this was all in a matter of seconds.
08:04I remember holding that lever for a fraction of a second.
08:07He hopes this move will help his plane avoid catastrophe.
08:11The effect was immediate.
08:14Now Burkill makes the announcement every pilot dreads.
08:18Mayday! Mayday! Speedbird! Speedbird!
08:22It was hard, very hard. I remember a couple of impacts and the noise.
08:36The landing was hard. Just a huge bang. The noise, bits falling off the ceiling.
08:45Then I also became a passenger because we were now in an uncontrolled airplane.
08:50We were sliding along the ground and I didn't know what we were going to hit next.
08:56And then I thought about my wife and kids and I said goodbye to them.
09:04The lights went out.
09:05I could hear the wreckage breaking up.
09:10And then we stopped.
09:11I was surprised that I was still there.
09:27And then I looked around the flight deck and I was more surprised to see that all three of us were unscarred.
09:34And I quickly became the captain again.
09:44The crew switches off the fuel.
09:46APU fire switch.
09:48Hydraulic and electrical systems.
09:50Patrol switches. Come, checklist complete.
09:53I then had to look after my survivors.
09:57I thought 20% were dead because this aircraft was broken up.
10:02This is an emergency. Evacuate. Evacuate.
10:06The air stewardess then took control completely.
10:11And as she opened the door, I smelt the fuel.
10:17You should hurry.
10:18And realized that we need to get off this aircraft.
10:22The big danger now is fire.
10:25Having survived the landing, passengers could be killed if flames sweep through the jet.
10:29Jump. Jump.
10:31I left all my luggage and just got myself down the slide.
10:33Jump.
10:35Let's get out of here.
10:37I went through the galley and checked the right-hand aisle.
10:41And I was surprised to see nobody there.
10:44Despite Birkhill's fears, there are no casualties.
10:58Outside in the cool January air, the scale of the disaster is clear.
11:03The right wheel had actually been ripped off during the impact.
11:07The engines were just sad.
11:09They were ripped apart.
11:11The cowlings were ripped off and the engines were half-buried.
11:15It wasn't an aircraft anymore.
11:17I now start to realize that we've been involved in a major accident.
11:21I saw the damage to the undercarriage and to the wing.
11:25The plane narrowly missed the A30 and the antennas at the foot of the runway.
11:31It could have been total devastation.
11:34The impact had been on anything other than soft mud and grass.
11:41The likelihood of a fire was immense.
11:44Given the amount of damage, it's incredible that only 47 people were injured.
11:49I felt quite lucky that I was still alive.
11:52It was quite a surreal feeling.
11:57From China, British Prime Minister Gordon Brown praises Birkhill and the crew.
12:01I think it's right to pay tribute to the calmness and professionalism of the British Airways staff.
12:06The captain, Peter Birkhill, for what he achieved in engineering a landing that protected lives.
12:14Investigators have some early hunches about what caused the engines to fail.
12:18They also have plenty of clues.
12:21But a key piece of evidence is already missing.
12:26He throws emergency planning swung into action.
12:28The crash of British Airways Flight 38 dominates the news.
12:32It's the most serious accident at Heathrow in 30 years.
12:36Heathrow Airport is a very busy airport.
12:41It is the main airport in the UK.
12:43So anything that happens in Heathrow Airport immediately hits the media.
12:49More significantly, the 777 is one of the world's most modern and reliable jets.
12:54The accident unsettles the airline industry.
12:59The 777 is as safe as an airplane can be.
13:04It had such a superb safety record.
13:08What on earth happened?
13:09You don't like not knowing whether it might happen to the rest of your fleet.
13:16Investigators quickly arrive on the scene.
13:18Phil Sleit is the lead engineer for Britain's AAIB, the air accidents investigation branch.
13:26When you first approach an accident site like this, the first thought you've got is, where do I start?
13:32The fan land is about a thousand feet short of the runway.
13:35The landing gears pushed up through the wings. The nose landing gear collapsed.
13:43Just hours after the crash, investigators interview the crew.
13:47Captain Peter Burkill has a first-hand account of what happened.
13:51I think I wanted to talk about it because I knew of the innocence of the whole crew.
13:56This isn't our fault. We didn't do anything wrong.
13:59But the engines weren't giving us any more power.
14:02Well, it looks like we have double engine failure.
14:04We tried to give them more power manually, but there was nothing.
14:08Burkill explains that something had caused both of the jet's Rolls-Royce engines to roll back
14:13at the same time, robbing the aircraft of power.
14:17When you hear something of a double engine failure, you start looking at what's common.
14:23What could cause both engines to fail at the same time?
14:27So our first thoughts were that it may have run out of fuel.
14:30A fuel shortage is rare, but it has happened before.
14:36In 1983, a Boeing 767 ran out of fuel flying over central Canada.
14:43A mistake in converting between metric and imperial measurements left the plane with much less fuel
14:48than the crew thought. At 26,000 feet, they lost power to both engines.
14:55The captain was able to glide the plane to a safe landing at an abandoned air base.
15:04In the case of Flight 38, this theory is immediately questioned.
15:09Jet fuel has a certain odor. Anyone who has worked with an aircraft will know the distinctive smell
15:14of jet A1 fuel. There was certainly a lot of fuel leaking from the aircraft,
15:20from the ruptures to the bottom of the engines when we arrived on site.
15:24The check of the plane's dipsticks confirms two of the tanks did in fact have fuel.
15:29So we knew that there was plenty of fuel on board this aircraft to complete the flight.
15:34There remain several other possible explanations for such a loss of power,
15:38and investigators must tackle them all.
15:40There is great confidence that the mystery can be solved, as any and every piece of evidence
15:47investigators could ever want is readily available. They have access to the pilot,
15:54the crew, and most importantly, the entire plane.
15:59We were quite fortunate to have the amount of data that we had on this aircraft.
16:05Because the aircraft remained intact, we were able to interrogate lots of computers,
16:09and also get lots of data from the recorders. Additionally, we had data external to the aircraft,
16:14such as radar data, and also the radio transmissions as well.
16:19Mark Ford retrieves the plane's flight data recorders, which promise to give investigators
16:24important clues. He has another resource, the QAR, or Quick Access Recorder. While the black boxes are
16:33in the rear of the plane, the QAR is a data recorder in the front, used mainly for diagnostics.
16:41It does have an advantage over the flight recorder, though, in that it has a greater memory capacity,
16:45and can record additional parameters over and above those available in the flight recorder.
16:50You can recover the data from a Quick Access Recorder within a matter of minutes in some cases.
16:56Speed, altitude, control settings, cockpit conversations. In all, the various recorders
17:02have preserved 1400 different pieces of data, which should help the investigators close the case.
17:08But when they study the QAR, what they find is chilling.
17:12The Quick Access Recorder data stopped about 45 seconds prior to the accident itself. Initial thoughts
17:18were that there was an electrical problem, possibly, that had affected not only the QAR,
17:22but possibly the engines as well. The 777 is one of the latest advances to computer-assisted airplanes.
17:30Pilots don't directly control the plane. Instead, their inputs are sent to a computer.
17:36Those signals are then relayed to the engines, flaps, and other systems on the aircraft.
17:43Pete, I can't get power on the engines.
17:45A massive failure of the plane's information systems could explain why the engine stopped working.
17:53Perhaps the computers that control them froze.
17:59Farnborough is home to the AAIB.
18:02The flight data recorder has been sent here for analysis.
18:07An electrical problem would be recorded on this device.
18:10But interpreting the information will take some time, time investigators don't have.
18:18There are hundreds of 777s landing every day. They need to find answers before whatever brought
18:24down Flight 38 strikes again.
18:30While they wait, authorities turn their attention to the fuel recovered from the ruined plane.
18:36A bad batch of fuel could have deprived the aircraft of power just when it needed it most.
18:43Fuel can be contaminated in many different ways. It could be particle contamination,
18:47it could be biological contamination, and they can get into filters to restrict the flow.
18:53We took several samples from various points within the fuel system. So not only from the fuel tank itself,
19:01but also from remnants within fuel lines and also within various fuel components.
19:06We managed to trace the fuel back through the documentation to a shipment of Jet A1, which came from South Korea.
19:13And that was shipped across in a tanker to China, and was then transported by pipeline to Beijing airport.
19:21We compared it with over 1,200 other batches of fuel in the UK, and it came out to be very good.
19:28And investigators next consider the possibility of a blockage in the fuel tanks.
19:42They discover some bizarre evidence.
19:44Several small pieces of tape are recovered, along with something else.
19:49When we were in the fuel tanks, we did find a few small articles. One of them was a red scraper.
19:56The items were likely leftover from when the plane was built seven years ago.
20:00But while they're peculiar, there's no indication that any of them played a role in bringing down the plane.
20:07Obviously, it's not ideal to find anything within a fuel tank.
20:11We obviously looked to see whether this would have had an effect on the fuel flow to the engines.
20:16The items were so small, they would not have caused a restriction.
20:23As the search for answers continues, a puzzling find surfaces.
20:27Less than three years before the Heathrow crash, another 777 suffered a serious mid-air problem.
20:35After taking off in Perth, Australia, a Malaysian passenger jet was climbing through 38,000 feet,
20:41when suddenly the plane's autopilot pitched the nose up and climbed steeply.
20:48Calamity was only averted when the pilot took manual control of the jet.
20:54They did manage to get it safely back to base.
20:56The investigators established that this was a computer problem.
21:01British aviation authorities consider that the electronic brain of one of the world's most reliable jets
21:07might be faulty.
21:12The Malaysian Airlines aircraft was really quite an unnerving one.
21:18The investigators sort of pulled out the files on it and started looking over it to try and get some clues.
21:23Did we have a problem with the electronic control system causing the engines to roll back?
21:28If flaws are found with Flight 38's computers, it means 777s around the world could all be disasters in the making.
21:37This thought hangs heavily over the industry.
21:44When the readout of the plane's flight data recorder is conducted in Farnborough,
21:49investigators learn that the crash could have been much worse.
21:52There was very little they could actually have done.
21:57It looks like we have double engine failure.
22:01There was only 30 seconds between when they were fully aware of what was going on.
22:04Airspeed low.
22:06And the accident was inevitable.
22:07Records show that soon after the engines failed,
22:10the plane started falling faster than 1800 feet a minute, a very steep descent.
22:15But lack of power was only one factor working against the crew.
22:21They had extended their flaps on descent.
22:24It helps control the plane at lower speeds by increasing lift,
22:27but the extended flaps create drag, which slows the plane down.
22:31It takes more power to keep the plane flying with a wider wing.
22:35Airspeed low.
22:37I needed to raise the flaps.
22:41I knew that by raising it one notch to flap 25 would be the right thing to do.
22:46To reduce the drag, that's what I had to do.
22:52And what he did here gave them a few extra feet.
22:58Had the flaps been left at flaps 30,
23:00the aircraft would have struck the ground just before a set of ILS antennas.
23:06The plane then would have slammed into the antennas,
23:09sustaining even more damage and increasing the chances of serious injuries.
23:17For their efforts, Burkill and his team are considered heroes.
23:21Flying is about teamwork and we had an outstanding team.
23:24The evacuation...
23:24There is no doubt, without the flight crew's actions,
23:27Flight 38's landing would have been a catastrophe.
23:35Now the recordings...
23:36As they continue examining data from the flight data recorders...
23:40Continue right to the moment of impact.
23:43Investigators are no closer to solving the case.
23:47Analysis of the flight recorder didn't identify any particular fault with the
23:51aircraft electrical system that would have resulted in both engines rolling back.
23:55They are at least able to determine why no data was found on the quick access recorder for the last 45 seconds of the flight.
24:03It's not an electrical fault as they first feared.
24:06The 45 second delay in the QAR recording was a result of the fact that the QAR doesn't record in real time.
24:13It buffers the data and then will record approximately 45 seconds later.
24:18With all the information from the plane's various data recorders now collected, investigators have a precise picture of what happened.
24:30The jet was on the proper course as it made its approach to land when things went horribly wrong.
24:35At 720 feet, the right engine rolled back. Seven seconds later, the left engine rolled back.
24:43The autothrottle attempted to command greater thrust.
24:47That's not me, that's the autothrottle.
24:48But the engines didn't respond.
24:50I can't get power on the engines.
24:54While electrical and computer problems are ruled out as causes of the crash,
24:59the flight data recorders do point investigators to the likely source of the problem.
25:04The two most significant parameters from the quick extra recorder were the fuel metering valves.
25:08Both those valves indicated that they had opened to their fully open position.
25:13The plane's computers were calling for as much fuel from the tanks as possible.
25:18The valves were fully open, but not nearly enough fuel was reaching the engines.
25:23A plane with plenty of fuel and a working computer system still crash-landed, and investigators can't determine why.
25:35They focus on the weather on the day of the accident.
25:41It was a very cold air mass over Siberia, so we were aware of the cold conditions,
25:46but the flight was expected to be smooth and also quick.
25:49The plane's path took them high over Russia.
25:52The outside temperature went as low as minus 74 degrees centigrade.
25:57It's a potentially dangerous temperature, if not monitored closely.
26:01In cold air masses, you have to be very aware of the fuel temperatures.
26:06When fuel starts to freeze, it produces wax.
26:09As the fuel temperature drops, the wax becomes greater within the fuel itself,
26:14until it comes to a point where it can no longer flow.
26:16We have a fuel temperature gauge on the flight deck, which is monitored at all times,
26:24and I personally look at that every time I do a fuel check, which minimum is once an hour.
26:29Basically, you don't want to get it below minus 34 degrees centigrade.
26:34While they were cold, the temperatures never dipped into the danger zone where the fuel could wax and clog the system.
26:42And the fuel temperature increased significantly as the jet approached London.
26:45We were coming through 20,000 feet, and I remember seeing minus 20 degrees centigrade, so it had already started to warm up.
26:55Another potential cause of the crash is ruled out.
27:00Investigators are now running out of possible explanations.
27:03And the expectation from the media, and also from aviation experts, was that we would have the answer within days.
27:11But there was no comment today about the ongoing investigation.
27:15It very quickly became apparent that that would not be the case.
27:19They had the pilots, they had the passengers, they had the aircraft, they had everything there.
27:25Except the thing that caused it, that had disappeared, as if by magic.
27:29Despite mountains of data and physical evidence at their disposal, investigators are still unable to say what caused the crash of a British Airways 777 at Heathrow Airport.
27:49They turned to a failure of the fuel delivery system as a culprit.
27:54To prove it was responsible, they need to pinpoint anything out of the ordinary about Flight 38's journey.
27:59On January the 17th, 2008.
28:04It's a daily flight, operating from Beijing to Heathrow.
28:08We wanted to work out what was unique about this flight.
28:13Why this flight in particular?
28:17If you've got a very puzzling incident, like the 777 accident at Heathrow,
28:22you're going to mine all the data you can.
28:25Just put them over there for now.
28:30So we approached many operators to obtain some data of previous flights so that we could then do a comparison.
28:41Flight data is collected from companies around the world.
28:45And we had something like 144,000 flights in all.
28:49But it will take months of work to analyze this enormous volume of information.
28:57To study Flight 38's fuel system more closely, huge sections of it are brought to the AAIB hangar and reassembled.
29:05It allowed us to basically just sit there and look at it and to brainstorm and come up with ideas as to what might have caused it.
29:13McDermid and his team consider all possibilities, from design flaws to a malfunction specific to this aircraft.
29:20The examination comes up empty.
29:23We carried out an exhaustive and very thorough inspection and testing of the fuel system, and we find nothing wrong.
29:30Frustrated, investigators are at a dead end.
29:33We kept going through this cycle.
29:36We kept going back over what we'd done before, had we missed something.
29:41And every time we went back over, we kept coming back to, no.
29:45There was no trouble with the plane's computers.
29:49It had plenty of fuel.
29:52And no problems with the fuel itself.
29:55But somehow, when it was most vital, the engines didn't get the fuel they needed.
30:04The AAIB detectives have run out of suspects.
30:09There was no clear explanation.
30:13Nothing that you'd seen before.
30:17It's not given the penalty.
30:18In any airplane, let alone the 777, could have explained this.
30:25Now they turn away from the clues they have to those they don't.
30:32Phil started coming out of a mantra, which was a quote from Sherlock Holmes.
30:36Whatever is left, however improbable,
30:41must be the cause.
30:43It has to be.
30:49In this case, we always kept coming back to what's there,
30:53what could have been there, that's not there now.
30:55And we come back to ICE.
30:58Suspicion that the cause of the accident was ICE grew stronger and stronger.
31:02But investigators are faced with a nearly impossible task.
31:05How can they prove that ICE had brought down the plane when the evidence they need would have melted
31:11by the time they arrived?
31:16Three months after the crash, Brian McDermott flies to Seattle to work with engineers at Boeing,
31:21the company that built the 777.
31:23If ICE brought down Flight 38, they need to prove how and why.
31:29We took the pipes from the right side of the fuel system.
31:35And those pipes and those couplings were used on the test rig at Boeing.
31:39Ice in the fuel lines has long been a concern for jets of all kinds.
31:45But decades ago, engineers found an ingenious way to deal with the ice forming in the fuel of passenger jets.
31:51The heart of the system is the fuel oil heat exchanger, or FOHE.
31:59Cold fuel runs through thin tubes, which are surrounded by the hot oil used to lubricate the engines.
32:04The purpose of a fuel heater is to heat the fuel up to prevent icing of the delicate fuel control system.
32:12The FOHE is designed to prevent exactly the problem investigators suspect crippled Flight 38.
32:20But it's also a potential bottleneck in the system.
32:24During the fuel testing, we were looking to establish where we could get a restriction
32:30that would restrict the fuel flow to 6,000 pounds per hour.
32:34And the only place that we could get such a restriction occurring was on the face of the fuel or heat exchanger.
32:40Investigators have to prove three things.
32:43First, that substantial amounts of ice can accumulate inside the fuel pipes.
32:48Second, that the ice can suddenly be released.
32:52And finally, prove that it can block a device specifically designed to melt it.
32:59We use different methods of controlling the environment around the pipes.
33:02That range from dry ice to cold fuel and to hot air to simulate the environment around the pipes that the aircraft experienced during the flight.
33:14After each fuel cooling test, investigators look inside the pipes for ice.
33:20But they can never get much ice to form, let alone block the fuel lines.
33:24When the fuel temperature was minus 30 degrees centigrade, very little ice would stick to the inside of the fuel pipes.
33:32Investigators know the temperature on the accident flight didn't get much colder.
33:36So how had the ice formed?
33:41We still hadn't answered the question of where does the ice come from in the first place?
33:45And indeed, was it ice? Or was there something else that we've missed?
33:50Surprisingly, when the fuel temperatures are warmer, the breakthrough arrives.
33:55If you have water in the fuel, then that water will freeze and form ice crystals.
34:00And then when the temperature gets to about minus 20 degrees centigrade, then those ice crystals will start to stick together and will also stick to the inside of the pipes.
34:12Below minus 20, any ice crystals in the fuel are too cold to attach to the pipes.
34:17But in the sticky range, between minus 20 and minus 8 centigrade, slushy ice forms and sticks to the sides of the fuel pipes.
34:28So when we demonstrated that ice could actually build up and grow onto the walls of the fuel pipes, there was a certain amount of surprise as to how much could actually grow.
34:38And now we're getting somewhere.
34:40Well, the question for us at this stage was, how could that ice come off the pipes?
34:44Investigators think they have the smoking gun, but they still can't prove how a small bit of ice could bring down a $200 million plane.
34:55They continue analysing thousands of comparative flights to see what made Flight 38 unique.
35:01But after seven months, they still can't crack the case.
35:05From 35,000 Rolls-Royce powered flights, it was less than 1% that had the same features as the accident flight.
35:11Then, on November the 26th, 2008, more than 10 months after the crash, the importance of finding an answer is underscored when the elusive culprit strikes again.
35:25Another 777 runs into trouble 39,000 feet above the United States, when one of its engines simply stops working.
35:33Fortunately, in that case, the engine recovered and the aircraft landed safely at Atlanta.
35:42Even though it didn't result in an accident, it reinforces concerns that there's a potentially dangerous flaw on every 777 around the world.
35:52The incident captures the attention of the British Airways crash investigators.
35:55The Delta Shanghai flight really was investigated with huge interest.
36:03The engines were Rolls-Royce engines of the same type.
36:08So they immediately went looking for evidence of the same problem.
36:14And, in fact, they do find important similarities between the Delta airliner and British Airways Flight 38.
36:20The aircraft had operated a long sector from Shanghai and China to Atlanta.
36:26The fuel temperatures were within the sticky range that we had defined during the research.
36:32We were able to see that the reaction of the engine was very similar to that of the 777 at Heathrow.
36:40Later examination of the Delta flight shows no evidence of any electronic, mechanical, or fuel system problems.
36:50Strongly suggesting that the culprit was indeed ICE.
36:53When we heard about the Delta flight, we were more convinced than ever that we were on the right track.
37:01McDermott and the investigators at Boeing in Seattle continue their testing.
37:05It's been a year since the accident, and the problem hasn't been found or fixed.
37:11They've run hundreds of simulations and spent millions of dollars.
37:15They still can't get the ICE in the fuel lines to clog the fuel oil heat exchanger
37:20and cause the kind of blockage that brought down Flight 38.
37:23We came to a stage where we had not actually come up with what had caused this accident.
37:36At this time, the media and also the general public,
37:41there was a bit of unrest as to why we had not yet come up with an answer.
37:47Industry pressure to resolve this case is intensifying.
37:56Investigators still need to know what made Flight 38 different from thousands of others
38:01that had flown under similar conditions.
38:04To find out, they retrace every moment of Flight 38's journey.
38:10The voyage from Beijing involved a gradual climb, a steady cruise, and a gradual descent.
38:17The fuel temperatures fell and rose accordingly, causing ice to accumulate in the fuel lines.
38:23That ice posed no danger unless it was released.
38:27Now investigators study the fuel flow and find that it was kept steady for most of the flight.
38:33The autopilot maintained constant speed and low power for hours,
38:37never demanding an abrupt increase in engine power until just before they reached the runway.
38:42The approach into Heathrow was quite a turbulent approach.
38:48And the engines were demanding various levels of thrust power.
38:51That's not me, that's the autothrottles doing their thing.
38:54And there were four changes in fuel flow,
38:58one of which was a very high fuel flow of around about 12,000 to 13,000 pounds per hour demanded.
39:05A closer review of the American Delta flight reveals that its engine rolled back under the same
39:11circumstances, a sudden demand for power after a long period of consistent speed.
39:21Investigators are now set to duplicate these precise conditions.
39:25They hope that by reproducing the moments just before landing, which was the only part of the
39:30flight where the crew suddenly required more power, they may finally get the answer they're looking for.
39:37The problem that we were looking at is very, very difficult to replicate.
39:41And during what was one of the last tests, we actually managed to get all the elements together.
39:45After simulating running engines at constant speed, investigators increase the power.
39:51We allowed the ice to accumulate for three hours, and then the flow rate was increased.
39:58What happens next breaks the case wide open.
40:05In Boeing's Seattle lab, investigators' sudden demand for more engine power causes the fuel pressure
40:12downstream of the fuel oil heat exchanger to drop dramatically.
40:15We then saw that ice had formed across the face of it.
40:26Soft ice that had formed deep inside the fuel lines broke free when the pressure was abruptly increased.
40:34It restricted the flow of fuel to the engines.
40:40Investigators have finally found the Achilles heel hidden deep inside the 777.
40:45The tubes that bring the fuel through the FOHE jut out just above the container of hot oil.
40:53It's just a few millimetres, but was enough to prevent the ice from coming in contact with the
40:58hot surface below and melting.
41:00Now, the ice doesn't totally restrict the fuel flowing through it.
41:05It has some porosity.
41:07So the fuel will continue to flow through.
41:10But the flow rate is much lower than it should be.
41:13In all of the tests, only one gave investigators the result they were looking for.
41:18The one that exactly matched the journey of flight 38.
41:22While the plane flew over Russia, water in the fuel turned to ice.
41:28At minus 20, it began to build up along the inside of the pipes.
41:33The steady speed of the aircraft ensured this accumulation was never interrupted.
41:39Then, as the plane approached Heathrow, turbulence resulted in the first demand for power since much
41:45earlier in the flight, and things cascaded into a serious problem.
41:49The gushing fuel washed the ice through the fuel system until it built up against the face of the FOHE,
42:02with disastrous results.
42:04Pete, I can't get power on the engines.
42:08It's not giving me power.
42:10Facing a threat no one knew existed,
42:13the pilots didn't have a chance to solve the problem.
42:19But why had the American Delta crew been able to clear the blockage,
42:27while the British Airways flight ended in near catastrophe?
42:35It's discovered that after just a few seconds of reducing engine power to idle,
42:42the blockage in the FOHE clears.
42:44But this maneuver was not available to the British Airways pilots because they were so close to the ground.
42:55Soon after the Seattle tests, Rolls-Royce redesigned the fuel oil heat exchanger.
43:00So what Rolls-Royce did was to actually remove those protruding tubes so you now have a flush face.
43:05And they found that if they flattened the surface, even if ice crystals did form on the fuel,
43:11they'd go straight down the holes in the block.
43:15Very, very easy fix.
43:19Other aircraft manufacturers are ordered to ensure that their systems aren't vulnerable to the same problem.
43:24Peter Burkill, John Coward and the rest of the crew of Flight 38 received the British Airways safety medal for their performance during the accident.
43:36It's the company's highest honor.
43:39The crew have been presented with an unprecedented failure.
43:43And they did the best they could in the time that they had available.
43:46The crew did as good a job as they could.
43:51And since they really only had about 30 seconds to think about what they were going to do about this,
43:57they couldn't have done any better than they did.
44:00The ice that brought down one of the world's most sophisticated airplanes was gone by the time investigators showed up.
44:06The weird thing about this investigation was that the culprit had fled the scene.
44:12The inquiry into what happened consumed thousands of hours of manpower and cost millions of dollars.
44:21These people really pulled out the stops to find out.
44:24And the reason? We have to know.
44:28With unrelenting diligence and a little inspiration from Sherlock Holmes, the mystery was finally solved.
44:37Whatever is left, however improbable.
44:42Must be the cause.