Original subtitles

(narrator): An Airbus A330 loses power enroute to Hong Kong.

- What the hell was that? - We now have two engines stalled.

You know, my blood ran cold.

(narrator): To survive, the pilots must avoid ditching in the Indian Ocean.

(screaming)

Soaring six miles in the air, a British Airways 747 suffers a mysterious engine flame-out.

(exclamations) - Mayday, mayday, mayday.

- What the crew had to deal with was mind-boggling.

(narrator): And with four engines down,

China Airlines Flight 006 plummets thousands of feet in just seconds.

- Engines 1, 2 and 3 have lost thrust! (alarm sounding)

- This airplane is totally out of control.

(narrator): In three terrifying events, with all engines out...

- That is one of the most dire situations any crew can be in.

(narrator): ...can investigators piece together what really happened?

- Stop. Would you look at that.

- Mayday, mayday.

- It's going up!

(indistinct radio chatter)

- Seatbelt, please. Thank you.

(narrator): Cathay Pacific Flight 780 cruises at 38,000 feet

over the South China Sea.

(chiming) - This is your captain speaking.

We'll be starting our descent into Hong Kong shortly.

(narrator): On a 4.5-hour flight from Surabaya, Indonesia,

the plane is just 30 minutes from its destination of Hong Kong.

- It's a crisp morning; clear skies, a light wind.

It was a nice day to go flying.

(narrator): Captain Malcolm Waters

is one of Cathay Pacific's youngest captains.

His first officer, David Hayhoe,

is an ex-fighter pilot with the Royal Australian Air Force.

The Airbus A330 is powered by two Rolls-Royce Trent-700 engines.

Every aspect of flight operation is aided by advanced computers.

- The engineering and complexity that goes into them,

and the science that presents the information, they're incredible machines.

(narrator): 165 miles from Hong Kong Airport,

the Airbus leaves cruising altitude

and begins its descent.

- Airspeed's, uh, 295 knots.

Rate of descent: 700 feet per minute.

It's looking good.

(narrator): The aircraft is performing perfectly. (rattling)

And then something goes wrong. (alarm sounding)

- What the hell was that?

I describe it as a low, thumping noise and airframe vibration,

so, you know, David and myself kind of looked at each other, like: That's unusual.

(narrator): The flight computer alerts the pilots to a problem.

(alarm sounding) - Okay, let's see what we got.

- Engine 2 stall.

(narrator): The plane's monitoring system indicates

there's an issue with the right engine,

engine #2.

- Okay... thrust lever #2.

Confirm?

- Confirm.

(narrator): Captain Waters reduces power on the engine to idle

to protect it from damage. - Idle.

(narrator): The lowest possible level while still keeping it running.

It has an immediate effect. The engine noises disappear.

- That's better.

(narrator): Without thrust from the right engine,

the pilots are now relying exclusively on the left engine to get them to Hong Kong.

- A single-engine approach is not a big deal.

We practise it a lot in the simulator.

(narrator): But as the flight crew prepares for landing,

the left engine, engine #1, also fails.

(alarm sounding)

- We were relying on this one engine to get us safely on the ground,

and now it had exactly the same symptoms and noises and sounds as the other engine.

Engine 1 stall.

- Engine 1 stall confirmed.

- Engine 1 to idle. (alarm sounding)

(alarm stopping)

(narrator): Both engines are now still running, but producing no thrust.

The plane is gliding.

- Dammit! Our descent rate is not looking good.

(narrator): Without thrust, they won't make it to Hong Kong or any other airport.

Despite several attempts, the pilots cannot get the engines to produce power.

- We've only got five, six minutes before we're at sea level.

I... felt fear.

And you have all those human responses to fear.

The hair standing up on the back of your neck,

the tightening of your stomach, the dryness in your mouth.

(narrator): The pilots confront the grim prospect of ditching in the South China Sea.

- I'm calling a mayday. - Do it.

- Approach, mayday, mayday, mayday.

Cathay 780 had engine 1 stall and engine 2 stall.

- Cathay 780, understood.

- The seas looked very rough. It was a lot of whitecaps.

The swells would be one to two metres.

I felt that our engines would act as two big scoops

and would pitch the aircraft down quite violently,

and that would probably result in us cartwheeling and breaking apart.

This cannot be happening.

(narrator): First Officer Hayhoe begins preparing to ditch the plane.

Then Captain Waters gets an idea.

- Okay... try slow movements.

Go slowly. Just...

ease in fuel.

Easy does it.

I was just pinching the side of the thrust lever just to move it a millimetre.

Each time I pinched it, it would just go up a millimetre.

(narrator): Incredibly, it seems to be having an effect.

- Rotation increasing in engine 1.

- It's working.

The rotation of the fan was increasing from...

28% to 29 to 30 to 32

as I moved this very, very slowly and gently up.

(narrator): Captain Waters realizes that the engine won't go any higher than 74% power.

- That'll have to do.

- We got a thrust setting that resulted in us being able to fly level.

We weren't descending any more and...

that was, like, a huge relief.

(narrator): With one engine working,

the pilots can now attempt a landing at Hong Kong Airport.

But there's no margin for error.

- You see that? Altitude is holding.

- Fantastic.

Okay, approach preparation.

- We did have an engine that was now functioning, but I didn't trust it.

Let's do this.

- Okay, flaps 1.

- Gear down. - Gear down.

(narrator): The safest plan is to get the plane 5,500 feet from the ground,

then pull engine 1 back to idle,

reducing speed and altitude...

...in preparation for a gentle glide onto the runway.

- Cathay 780, we have both runways available for your approach.

- Final items... okay.

(narrator): But just one minute from touchdown...

- It's overspeed.

(narrator): An overspeed warning sounds,

a signal the aircraft is flying too fast.

They should be slowing down.

- Speed checked: 240.

800 feet.

- You know, my blood ran cold. It just looked completely wrong,

and I was very uneasy that things were out of my control

and that there was something that I was missing.

(narrator): Then he sees it.

Engine 1 is still running at high speed,

too high to land safely.

- I had that whole feeling again of fear.

Anger. It was a scary moment.

(narrator): The pilots have no choice but to risk a high-speed landing

on a runway at the edge of the ocean.

- It was our one chance to get this on the ground,

and we had to make the best go at it.

(automation): Too low. Terrain.

Too low. Terrain. Pull up.

(narrator): Going 100 knots faster than normal...

(automation): Pull up. (narrator): ...Captain Waters pushes the nose down,

forcing the Airbus onto the runway.

- Brace! (narrator): At the end... lies open water.

- The aircraft did not wanna land.

And I remember thinking: Wow, this is it. 'Cause it was very violent.

(screaming)

- Full reverse! (dramatic music)

(narrator): The crew deploys reverse thrust

and applies full braking power to avoid overshooting the runway.

- No #2 reverse! No decel.

- Immediately, I just step on the brakes, hold 'em,

toe brakes to the floor.

(narrator): Just one faulty engine is providing reverse thrust.

Will it be enough to stop the plane from careering into the sea?

- Full reverse!

(narrator): Cathay Pacific Flight 780 screeches to a halt

just a few thousand feet from the end of the airport's runway.

- I can't believe it.

- We made it.

Nice one.

- It was just this humongous relief.

I was so happy that, um, you know, we were gonna go home and see our families.

(sirens wailing)

(narrator): The passengers and crew evacuate safely,

with only a few minor injuries.

Hong Kong's Civil Aviation Department immediately launches an investigation.

- Thank you.

(narrator): Because the plane's Trent-700 engines were made by British company Rolls-Royce,

Anne Evans, of the British Air Accidents Investigation Branch, joins the investigation.

- This Trent-700 is a very common engine

fitted to a lot of airplanes all over the world.

So if there's an engineering problem with a particular design,

then we want to find that quickly.

(narrator): Investigators look to the plane's flight-data recorder for answers.

They start with the A330's engine functions.

- Stop. What's going on here?

(narrator): Right away, they notice something unusual.

- Thrust levers are moving, but fuel flow's flat-lining.

(narrator): Right after the pilots tried to restore power to the engines

by pushing the throttle up,

the fuel flow remained the same.

- Nothing happens.

The engines just are not responding at all. They're just remaining at idle.

Dammit!

(narrator): Investigators wonder if a fuel-flow problem caused Flight 780's engine trouble.

- Thank you.

(narrator): Evans turns to the plane's in-depth data logs.

They explain in detail the error messages... - Engine 2 stall.

(narrator): ...that appeared on the monitoring system throughout the flight.

- "Engine 2 control system fault."

(narrator): Anne Evans discovers that early in the flight,

the computers detected a problem in a key part of the fuel system called the main metering valve.

- So the warnings that were coming up

were warnings to do with the main metering valve supplying fuel to the engine.

(narrator): The main metering valve is made up of a piston

that slides within a cylinder.

When the pilots move the thrust levers,

it increases or decreases the flow of fuel to the A330's turbofan engines.

When investigators cut the valve open to study it...

- That's not normal, is it?

(narrator): ...they find something they've never seen before.

- What we saw seemed like very, very fine powder.

Even finer than caster sugar. Very, very small particles.

(narrator): Microscopic analysis reveals that the powder

is a type of superabsorbent polymer, or SAP,

made up of tiny spheres.

- These are organic compounds designed to absorb water.

That gave us a clue as to where they'd come from.

(narrator): The powder is used in refuelling trucks

to prevent water from getting into the aircraft's fuel tanks.

The refuelling trucks pump fuel from underground tanks and pipes

through a filter on the truck and into the aircraft.

If the fuel is contaminated with water,

the powder in the filter absorbs it by forming a gel inside the filter.

But the waterlogged gel is supposed to stay in the filter.

It should never end up in the fuel.

- It is so commonly used within the industry

for this purpose of filtering out water.

What we didn't understand was: How did it get on board the aircraft?

This one looks somehow collapsed.

(narrator): Investigators recover the filters from the truck

used to refuel Flight 780 at Surabaya Airport.

And when they examine a sample of the filter under a microscope,

investigators make a puzzling find.

- It looks like... sodium crystals?

(narrator): The powder spheres are encrusted with salt.

- Had salt water got into the fuel system?

This one's straight from the manufacturer.

(narrator): When Anne's team conducts tests on fresh filters, exposing them to salt water...

- Well, would you look at that.

(narrator): ...the filters collapse,

just like the ones used to fuel Flight 780,

allowing both the salt crystals and white powder spheres to pass through.

- What was important was that we demonstrated we could generate spheres.

(narrator): Investigators now believe salt water collapsed the fuel filters,

leading to powder contamination in the fuel system of Flight 780.

But one critical question remains.

- So how did salt water get into the fuel system?

(narrator): After a careful review of the fuel system

at Surabaya Airport,

investigators make a stunning discovery.

The fuel system is located close to the sea.

And during a recent upgrade,

the open fuel pipes were possibly exposed to groundwater.

Investigators now believe they know what happened to Cathay Pacific Flight 780.

The underground fuel supply, contaminated with salt water,

broke down a filter, releasing a powder into the fuel.

The powder jammed the metering valves,

preventing enough fuel from reaching the engines.

- Engine 1 stall. (alarm sounding)

- We had fuel contamination,

and that contamination throughout the fuel system

led to the seizure of both main metering valves,

such that the pilot no longer had control over the power of the engines.

(narrator): Investigators believe Captain Waters was able to restore

some thrust in engine #1

only because its fuel-metering valve wasn't yet completely jammed.

Only a small trickle of fuel was getting through.

- Slowly, slowly. Come on.

- Rotation increasing in engine 1. - It's working.

(narrator): Once the spheres jammed the valve, it was stuck open...

(automation): Pull up. Terrain. - Ugh!

(narrator): ...forcing Captain Waters to make the risky high-speed landing.

- No #2 reverse!

(narrator): Expert piloting brought Flight 780 safely to the ground.

(exclamations) - I can't believe it.

(narrator): Since the accident, there have been efforts

to improve the regulation of aviation fuel-handling and storage.

Manufacturers have designed the filters to prevent collapse and powder contamination.

The crew's heroic efforts in the face of engine failure

save Cathay Flight 780 from all-but-certain disaster.

Total engine failure is an ultra-rare occurrence on modern airliners.

- Seatbelt, please. Thank you.

(narrator): Fortunately, the fast-thinking flight crew of Flight 780 had some control

of their jet's engines,

allowing them to bring the plane to safety.

But 28 years earlier,

a bizarre incident puts the pilots of British Airways Flight 9 to the ultimate test.

- Oh, my Lord, look at engine 4!

- It's the same on my side.

- When you have an uncontrollable and unpredictable event

that puts your airplane at risk,

that takes a whole different set of skills to resolve.

- Dad! The engine's on fire!

- They've all gone... All four engines have failed!

(narrator): June the 24th, 1982.

British Airways Flight 9 cruises high over Indonesia.

In a few hours, the plane and all 263 people on board

are scheduled to land in Perth, Australia.

Captain Eric Moody commands the flight.

He's one of the first ever trained on the 747.

- Roger, check with Jakarta.

- Jakarta Control,

Speedbird 9 over Halim at level 3-7-0.

(ATC): Speedbird 9...

(narrator): First officer Roger Greaves has been co-pilot

for more than six years.

Barrie Townley-Freeman has been a flight engineer on these aircraft

for a little longer.

- I'd not flown with Eric before,

or Barrie.

That was the first time we'd actually met,

on that, uh, that flight.

Alright, Roger, it's all clear. Just keep your eyes open.

I'll be back in a moment. Just gotta use the loo.

(narrator): But while he's gone...

...conditions in the cockpit become unusual.

- We started to get these...

pinpricks of light on the windscreen.

It smelt like sort of a sulfuric electrical smell,

and I went on that flight deck expecting to hear

that we had some electrical smoke somewhere on the aircraft,

but nothing was further from the truth.

Anything on radar?

- No, it's clear, not a cloud.

Oh, my Lord, look at engine 4!

It's lit up somehow.

Captain, Captain, have a look at #1.

- It's the same on my side.

(narrator): The pilots notice that the plane's engines are lit by a brilliant white glow.

But it's the flight's passengers that first spot flames.

- Dad! The engine's on fire!

- There were huge flames coming out of the back of the engines,

40 feet long, shooting out of the back of all the engines.

What's going to happen? (alarm sounding)

(narrator): As fire engulfs the engines,

one of them revs loudly and flames out.

- Engine failure, #4.

- Once one engine fails, you call for the drill to shut that one down.

(narrator): Then the unthinkable happens.

- Number 2 engine's gone.

- Alright, then. Begin the engine shutdown. - No, wait!

They've all gone. All four engines have failed!

(narrator): Somehow, all four engines have completely stopped working.

- Roger, declare emergency.

- Mayday, mayday, mayday. Speedbird 9.

We have lost all four engines.

(narrator): Without engine power,

the 747 is now an enormous glider.

- One of the nightmares for a commercial airman

is the idea of losing all your power.

A 747 can glide 120 miles from high altitude, but at the end,

you're gonna come in contact with the surface of the earth one way or another.

- Alright, begin restart drill. - Set.

- Battery. - Check. On.

(narrator): The flight crew tries to restart the engines.

- Standby power. - On. - Anything?

Anything? - No!

(narrator): Plunging towards the Indian Ocean,

the crew has to get their engines going.

- Come on.

- Again, gentlemen. - Alright, from the top. Battery.

- Check. On. (narrator): Without engine power,

the cabin's air pressure decreases,

releasing the oxygen masks.

(exclamations)

Captain Eric Moody is running out of options.

- Come on. Anything? - No.

- We hadn't had any success with the drill at all,

uh, despite all the efforts we were putting in.

But it was the only thing we had left to cling onto.

(narrator): Descending steadily,

the flight crew prepares to ditch the Boeing 747 in the Indian Ocean.

- Alright, then. - I knew it was so difficult to land airplanes on the sea,

even when you had everything going for you.

Uh, and I thought: Well, we haven't got much going for us here.

I'd never done it before. (beeping)

(narrator): As a precaution,

Captain Moody decides to turn the plane back to the closest airport, Halim,

just outside Jakarta.

If they must ditch,

the chances of a successful rescue are higher

if the plane is closer to land.

- Start lever? - Cut off. - Fuel pressure?

(indistinct) - Stand by. Ignition on.

(narrator): And then, as suddenly as it stopped working,

the fourth engine roars back to life.

- Engine 4 back online!

- The noise a Rolls-Royce engine makes when it starts up,

well, it was wonderful to hear it.

(narrator): As the plane falls past 4,000 metres,

another engine coughs and comes back to life.

- Engine 3 back online!

(narrator): It's followed quickly by the final two.

- I can't believe it.

Engines 1 and 2 both back online!

(narrator): The crippled jet is back under full power. (cheering)

- Oh, my God, Mum! (applause)

- Jakarta, Speedbird 9. We are back in business.

(narrator): The crew calls for an emergency landing in Jakarta.

- Twelve thousand.

- Let's get this thing on the ground as quick as you can.

- Fifty feet.

Thirty feet.

- Reverse.

(laughter)

The airplane just landed itself. It seemed to anyway.

It kissed the earth. It was beautiful.

- Wow. That's... that's amazing. (chuckling)

(narrator): Flight 9 and its passengers and crew are safely on the ground,

but no one knows what happened. (cheering)

The next morning, the flight crew returns

to Halim Airport in Jakarta to inspect their plane.

The pilots and investigators are shocked by what they discover.

- The airplane had lost its sheen,

and in some places, it had been sandblasted quite well,

and all the decals and the paint had come off.

There really was very little to see

until they stripped the engines down.

(narrator): The flight crew and investigators have never seen anything like this before.

And their surprising discovery changes aviation-safety procedures forever.

(Ferguson): This was an event which was unique in aviation history.

(narrator): The engines from British Airways Flight 009 are sent to their manufacturer,

Rolls-Royce, in the UK.

Engineer Malcolm Grayburn and his team

are tasked with figuring out what caused them all to mysteriously flame out...

- Dad! The engine's on fire!

(narrator): ...and come back to life.

- We did do a forensic analysis of the engines.

(narrator): Grayburn is stunned by what he discovers.

The engines were choked with fine dust,

pieces of rock and sand.

On close study, he discovers that the debris is volcanic ash.

The evidence points to a clear suspect.

On the night of the flight, the Mount Galunggung volcano,

located just 100 miles southeast of Jakarta,

erupted unexpectedly.

The enormous ash cloud rose nine miles high,

right into the path of British Airways Flight 009.

Never before had a volcanic cloud seriously affected an airplane.

- Mayday, mayday, mayday.

We have lost all four engines.

(narrator): A turbofan jet engine works by sucking in enormous amounts of air.

The air is then highly pressurized by the engine's compressor.

This tightly packed air is mixed with fuel and ignited.

The force of this reaction propels the jet through the sky.

- The temperature in the combustion chamber,

where this ash is flowing through, are around 2000° Centigrade,

and so the volcanic ash we know melts at about 1300, 1400°.

(narrator): But when the liquid ash reached deeper into the engine,

it cooled slightly, turning into a sticky, molten goo.

It attached itself to the engine and began choking it.

- We got a fundamental disturbance of the airflow in the main core of the engine,

which caused the engine to backfire.

- Engine failure, #4.

(narrator): But if the engines were choked with ash,

how did they suddenly roar back to life?

- Engine 3 back online! (revving)

(narrator): What Grayburn discovers next

is that a remarkable piece of chemistry saved the plane.

- As soon as you came out of the volcanic ash, everything cooled down,

it was enough for this stuff to break off

and allow the engines to restart.

(revving)

- I can't believe it!

Engines 1 and 2 both back online!

(narrator): The pilots of Flight 009 are celebrated as heroes

for overcoming total engine failure

and guiding their plane and its passengers to safety.

But their miraculous discovery also provokes a giant leap forward in aviation safety.

- Now, more than 30 years later,

there's a worldwide system in place

to warn pilots when there's a risk of volcanic ash in the air

so the aircraft can avoid this kind of hazard.

It has worked wonderfully over the last few years.

- Here you go, gentlemen. - Hey, there she is. Hey! Melissa.

(narrator): But total engine failure happens again

just three years later.

China Airlines Flight 006 cruises on autopilot

39,000 feet above the Pacific.

- It was a routine commercial flight.

I sat there and read some books, went to sleep.

(narrator): While many of the 251 passengers doze,

the plane nears its destination of Los Angeles, California.

In the cockpit, the experienced three-man flight crew,

led by Captain Min-Yuang Ho,

has amassed more than 38,000 flight hours.

But as the crew prepares for an easy landing...

- Engine 4 is giving us weak thrust.

(narrator): ...the flight engineer spots something troubling.

There's a problem with one of the engines.

When the engine is throttled, it doesn't respond.

- We're losing speed.

(narrator): Then the strange situation suddenly gets much worse.

- Engine 4 flamed out.

(narrator): Engine 4 stops working completely.

- Take a look at engine-out procedures.

Work out a three-engine cruise altitude.

- Yes, Captain.

(narrator): Without the fourth engine, the plane slows down.

- Airspeed: 240.

- Reignite engine 4.

- Yes, Captain.

(narrator): At 39,000 feet, there isn't much oxygen,

so the chances of a successful relight are slim.

- No response, Captain.

(narrator): As the crew tries to restart their engine,

their plane slowly begins to roll to the right.

- We're banking right, Captain. Airspeed: 230.

(narrator): As the plane loses speed, it's in danger of stalling.

- Altitude, hold off. Nose down.

(narrator): Hoping to increase his speed,

Captain Ho tries pushing the plane's nose down.

Nothing the crew does seems to help.

Their jet is banking more and more steeply.

- I'm disengaging autopilot.

(screaming)

(narrator): Captain Ho takes manual control of the aircraft.

But he struggles as the plane veers into thick cloud.

He can't see the horizon.

Instruments that normally would help him keep the plane level

don't seem to be working.

- I've lost ADI! (alarm sounding)

- The ADIs have malfunctioned.

- It's going out of limits!

(narrator): Just minutes after engine #4 stops working,

the China Airlines flight suddenly stalls

and begins falling from the sky.

(narrator): A 747 jumbo jet is flipping upside down.

China Airlines Flight 006 plunges towards the Pacific Ocean.

- People just popped up like popcorn, hitting the cabin.

(screaming)

(narrator): In the cockpit, the flight engineer struggles against the plane's wild motion

to restart his fourth engine. (beeping)

The G-forces are so powerful that the flight engineer is pinned to the control pedestal.

- Ignition negative! (beeping)

(narrator): But his attempt is unsuccessful.

Then, the situation suddenly gets a lot worse.

- Engines 1, 2 and 3 have lost thrust!

(groaning) No response, Captain!

- Altitude: 370!

360! 350!

(narrator): In the cabin, the G-forces are punishing.

(screaming) - I closed my eyes.

I thought I was gone.

- Airspeed 80 knots and falling!

(beeping) No response!

The engines are flamed out!

(narrator): The stress of the dive tears the landing gear doors off the plane.

(woman sobbing) In less than a minute,

the plane drops almost 20,000 feet. (screaming)

- Emergency! Emergency!

(narrator): The plane suddenly breaks free from the clouds.

- I can see the horizon!

- Altitude: 10,000 feet!

(narrator): The captain uses the horizon as a reference to level the plane

just 30 seconds before they hit the ocean.

Now the G-forces suddenly change direction.

Passengers are pressed to the floor,

feeling five times their normal weight.

- You know, the G-force was so strong.

And... I weigh 200 pounds,

so my weight was almost 1,200 pounds.

(narrator): It's a race against time.

(beeping) And finally... - ADI's coming back.

(narrator): ...the plane starts to win.

- ADI's coming in.

(narrator): As mysteriously as the incident began,

three of the plane's engines regain power.

- Engines 1, 2 and 3 are coming back.

Engine 4 still negative.

(beeping) - Reignite engine 4. - Yes, Captain.

(narrator): Once again, the flight engineer tries to reignite the fourth engine.

(beeping)

But now... (revving)

- Engine 4 reignited.

(narrator): For the first time in minutes, the plane is flying under control.

- They saved the airplane.

That was a masterpiece of flying.

- Ladies and gentlemen, this is the captain speaking.

(sighing) Is anyone hurt?

(exclamations) Do we have a doctor on board?

(narrator): Captain Ho declares an emergency...

...and diverts the flight to San Francisco.

(all cheering)

- He made one of the best landings I've ever seen.

I mean, it was just... a perfect touchdown.

(narrator): On the ground, the full extent of the damage to the plane shocks everyone.

- Parts of the entire tail plane at the end were ripped off,

as though a tornado had come through.

(narrator): Two-dozen passengers have minor injuries.

A near-disaster was avoided, but what had gone wrong in the first place?

The National Transportation Safety Board is on site that very day.

The cockpit voice recorder is sent to Washington.

But it's designed to tape over itself every 30 minutes.

None of what happened in the cockpit

during the terrifying plunge from the sky remains.

- Without a cockpit voice recorder,

we had to reconstruct what the crew said and how they interpreted things,

and what was going on in the cockpit to the best of our abilities,

with the other data that was available to us.

(narrator): But the plane's flight-data recorder,

which suffered intense electrical damage,

has several gaps in the data log that have to be painstakingly reconstructed.

In the meantime, investigators begin by inspecting the plane's engines.

Despite the horrific dive through the sky,

engines 1, 2 and 3 are found to be in working order.

Engine 4, the first engine to fail, gets special scrutiny.

- They believed that the engine had flamed out,

or that there was something seriously wrong with the engine.

(narrator): After examining every inch of engine 4,

investigators determine that it was faulty.

- Engine 4 is giving us weak thrust. (narrator): And at 39,000 feet,

it wasn't able to produce adequate thrust to keep the faulty engine running.

- Engine 4 flamed out.

- The loss of thrust on a four-engine airplane is a minor event,

and the airplane will fly on three engines with no difficulty.

(narrator): Investigators are puzzled.

If the 747 was never in immediate danger,

is it possible that the plane's swift plunge

began somewhere other than in the engines?

(all screaming)

(narrator): The crew of China Airlines Flight 006

are brought in for intensive interviews by the NTSB.

- I heard the captain... (narrator): Without a cockpit voice recorder,

investigators rely on the pilots' statements

to piece together how a manageable problem became a near-catastrophe.

- I've lost ADI! (alarm sounding)

- The ADIs have malfunctioned!

- It's going out of limits!

- When we started banking right,

engine 4 was already flamed out.

We started to descend faster,

and engines 1, 2 and 3 also failed.

(alarm sounding) Engines 1, 2 and 4 have lost thrust!

(narrator): But the pilots' stories don't match the flight data,

which clearly shows that engines 1, 2 and 3

were running perfectly the entire flight.

They never lost thrust.

What could possibly have caused the plane to flip, twist, and hurtle towards the sea?

(screaming)

After months of analyzing the flight data and pilot interviews,

the NTSB can finally piece together

the series of events that led to this near-disaster.

Just after 10:00 Pacific time, the flight engineer spots the engine trouble.

- Engine 4 is giving us weak thrust.

(narrator): He struggles to fix the problem.

But investigators discover he misses a basic step.

He leaves the engine's bleed-air valve open.

The bleed-air valve regulates the flow of compressed air from the engines into the cabin.

When an engine isn't working properly,

the valve is supposed to be closed

so the engine can use all available air to restart.

- It's... a little puzzling that the flight engineer didn't shut off bleed air.

The end result is that the engine, which is slow to start,

won't start at all.

(narrator): Unwittingly, the flight engineer has started a ticking clock.

Engine 4 is slowly losing its ability to stay lit.

- We're losing speed.

(narrator): With more engine power on the left wing than the right,

the China Airlines flight begins turning.

- The proper thing to do would've been to step on the rudder.

That would've produced a, uh...

...twisting force, so to speak, that would've overcome the imbalance of the engines.

(narrator): Instead of adjusting the rudder himself,

Captain Ho continues to let the autopilot fly the jet.

But the autopilot isn't designed to move the rudder.

The autopilot can adjust the ailerons and spoilers on the plane's wings,

but these flaps aren't strong enough

to overcome the imbalance that the plane is experiencing.

- I'm disengaging autopilot.

(screaming)

(narrator): By the time Captain Ho takes manual control of the plane,

it's already banking alarmingly to the right.

- I've lost ADI!

(narrator): While he fights for control,

the 747 flips onto its back and enters a vertical nosedive.

Moments later, as G-Forces rapidly increase,

the flight engineer makes another enormous mistake.

- We started to descend faster,

and engines 1, 2 and 3 also failed. (beeping)

Engines 1, 2 and 3 have lost thrust!

(narrator): But the engines are perfectly fine.

Investigators now know the throttles were deliberately set to idle

in an attempt to slow the jet's furious fall,

something the flight engineer doesn't notice in the chaotic dive.

- If he had not seen the captain pull the power to idle on the... the engines,

he would reasonably assume that the fact that they went to idle was a problem,

rather than intentional.

(narrator): An investigation that starts with faulty engines reveals that, in fact,

a chain of mistakes by the crew puts Flight 006 just moments from certain death.

- The crew didn't behave as they should've behaved. Pilot error.

(narrator): But whatever mistakes the flight crew made...

- ADI's coming in.

(narrator): ...they still achieve the ultimate goal.

- The one big thing they did right...

...is they saved the airplane.

- China Airlines 006 is an extreme example

of why high-altitude-upset recovery training is so important.

It became a learning experience based on what this crew did.

(narrator): When an aircraft loses engine power...

...the response must be quick, concise and efficient.

- I can't believe it. - We made it.

- When you've got an engine problem, when you've lost an engine...

- Dad! The engine's on fire!

- ...the only thing you have to rely on is literally your training as a pilot.

- I can see the horizon!

- And it makes all the difference in the world. (tires squealing)

(cheering) (exclamations)

Subtitling: difuze