Original subtitles

Japan Airlines Flight 123 crashes into a mountain,

Japan Airlines Flight 123 crashes into a mountain,

killing 520 people.

It's the deadliest single aircraft accident in history.

It's the deadliest single aircraft accident in history.

We were working in this terrible carnage.

I get chills thinking about it.

I get chills thinking about it.

Investigators immediately

suspect an act of terror.

Right now it's a bomb.

Right now it's a bomb.

That's what the crime guys are telling us.

But the wreckage tells a different story.

There's no fire damage.

There's no fire damage.

No shrapnel damage?

What they soon discover...

It was the only thing holding the two sides together.

It was the only thing holding the two sides together.

...threatens to ground one

of the most popular commercial Jets on the planet, the 747.

of the most popular commercial Jets on the planet, the 747.

We were concerned that we

had a structural flaw in the airplane,

and others were worried too.

and others were worried too.

Ladies and gentlemen,

Ladies and gentlemen,

we are starting our approach.

We lost both engines.

Mayday.

Mayday.

Mayday.

Brace for impact!

I think I lost one.

Investigation started on the tragedy.

Investigation started on the tragedy.

He's gonna crash!

It's 6:10 PM at Tokyo's Haneda Airport.

It's 6:10 PM at Tokyo's Haneda Airport.

Japan Airlines Flight 123 is ready for departure.

Japan Airlines Flight 123 is ready for departure.

Number one engine, start.

Number one engine, start.

In the left hand seat is

39-year-old First Officer Yutaka Sasaki, training

39-year-old First Officer Yutaka Sasaki, training

to become a 747 captain.

I'll handle the radios while you fly.

I'll handle the radios while you fly.

The captain is Masami Takahama,

a former military pilot who joined

a former military pilot who joined

Japan Airlines 20 years ago.

Flight plan calls for a right turn out.

Flight plan calls for a right turn out.

Haneda ground... Japan Air 123 requests taxi, Charlie seven.

Haneda ground... Japan Air 123 requests taxi, Charlie seven.

Thank you, sir.

Today's flight is full,

with 509 passengers on board.

It's the start of the Obon holiday.

It's the start of the Obon holiday.

Obon is a Buddhist event

Obon is a Buddhist event

about the ancestors' spirits.

It happens in summer.

People in the city go back to their hometown

People in the city go back to their hometown

with families to celebrate.

26-year-old Yumi Ochiai is

an off-duty flight attendant.

Hi.

So glad to have a break for the holiday.

So glad to have a break for the holiday.

Yumi Ochiai was like many young Japanese.

Yumi Ochiai was like many young Japanese.

She wanted to see the world.

Working for the airlines allowed her to do that.

V1.

Rotate.

30 minutes before sunset, Flight 123 lifts off.

30 minutes before sunset, Flight 123 lifts off.

Positive rate.

Gear, up.

Very nice.

Flight 123 is one of dozens of 747s carrying

Flight 123 is one of dozens of 747s carrying

passengers throughout Japan.

To this day, the 747 is the most iconic jetliner ever

built. When it debuted in the '70s, it

built. When it debuted in the '70s, it

was by far the biggest commercial

plane that had ever flown.

plane that had ever flown.

And every pilot wanted to fly this plane.

To meet the growing demand

for cheap travel within Japan, Boeing designed the 747SR...

for cheap travel within Japan, Boeing designed the 747SR...

a special version of the jumbo jet.

a special version of the jumbo jet.

The 747SR, or short range, was an unusual variant

The 747SR, or short range, was an unusual variant

in that it was designed for high-density,

short-haul operations.

The Minister of Transportation was on the last leg.

Hope you gave him a smooth flight.

Hope you gave him a smooth flight.

Assisting on tonight's trip

is flight engineer Hiroshi Fukuda.

He's flown on 747s since they were introduced

He's flown on 747s since they were introduced

to Japan Airlines in the 1970s.

to Japan Airlines in the 1970s.

These earlier 747s required three pilots...

the third pilot being a flight engineer, who

the third pilot being a flight engineer, who

sat behind the captain and first officer

controlling all of the airplane's systems

and subsystems that were later consolidated

and subsystems that were later consolidated

into the more computerized two-pilot airplanes

that we have today.

Through 10,000, flight level 240 selected.

Through 10,000, flight level 240 selected.

It's an hour-long flight from Tokyo to Osaka...

one of Japan's busiest domestic routes.

one of Japan's busiest domestic routes.

11 minutes into the flight, Japan Airlines 123

approaches its cruising altitude.

approaches its cruising altitude.

OK.

1,000 feet to go, and we'll level off.

1,000 feet to go, and we'll level off.

Yes, sir.

As they neared 24,000 feet,

the crew settles in for what's expected to be a smooth flight.

the crew settles in for what's expected to be a smooth flight.

Whoa.

If an airplane is suddenly

displaced by some violent force, the autopilot

displaced by some violent force, the autopilot

can suddenly kick off.

Then the pilots now have to take control and physically

Then the pilots now have to take control and physically

steer the airplane again.

Something exploded?

Something exploded?

I'm squawking 7,700.

Putting 7700 into the transponder

is a way of broadcasting an urgent situation.

is a way of broadcasting an urgent situation.

Was that a gear door?

Check gear.

What about the engines?

What about the engines?

All engines are good.

When something unusual or sudden happens,

When something unusual or sudden happens,

pilots are trained to stop, analyze, evaluate the situation

pilots are trained to stop, analyze, evaluate the situation

before simply reacting.

Look at this.

16 seconds after the explosion,

16 seconds after the explosion,

the pilots realized the cabin is losing pressure.

If an airplane depression rises at anything

If an airplane depression rises at anything

over 20,000 feet or so, now suddenly you

over 20,000 feet or so, now suddenly you

don't have oxygen to breathe.

Put on your oxygen mask.

Fasten seatbelts.

We are making an emergency descent.

We are making an emergency descent.

Emergency masks provide

only 15 minutes of oxygen...

just enough for an emergency descent to below 10,000 feet.

just enough for an emergency descent to below 10,000 feet.

Something exploded.

Something exploded.

Right turn.

Right turn.

Tokyo, Japan Air 123, having trouble.

Tokyo, Japan Air 123, having trouble.

Request return back to Haneda.

Descend and maintain 220.

Over.

Roger.

Roger.

Right, heading 090.

The pilots of Flight 123

The pilots of Flight 123

attempt a sharp turn back to Haneda Airport...

now 70 miles behind them.

Don't bank so much.

OK.

There R5 door is broken.

There R5 door is broken.

We're making an emergency descent.

Don't bank so much.

Don't bank so much.

Hydraulic pressure has dropped.

While the crew tries to determine why the cabin

While the crew tries to determine why the cabin

depressurized, they face an even more serious problem

with the hydraulic systems.

with the hydraulic systems.

Without the hydraulic pressure,

Without the hydraulic pressure,

it's very difficult to move the control surfaces.

Don't bank so much.

It's manual.

The decrease in hydraulic pressure

is making it difficult for the first officer

to stop the dangerously steep right turn.

to stop the dangerously steep right turn.

Turn it back.

It won't go back.

Hydraulics are all out.

Nobody in that cockpit had ever seen

a complete hydraulics failure.

a complete hydraulics failure.

There was no checklist, no procedure

for how to deal with that.

Descend.

The pilots are unsure if their control

The pilots are unsure if their control

inputs are doing anything.

What's going on?

He's not turning back to Haneda.

Air traffic controllers

Air traffic controllers

are puzzled by Flight 123's erratic flight path.

Why isn't he descending?

Why isn't he descending?

Japan Air 123, confirm you were declaring an emergency.

ACTOR AS MASAMI TAKAHAMA Affirmative.

Request nature of your emergency.

ACTOR AS MASAMI TAKAHAMA Uncontrollable.

ACTOR AS MASAMI TAKAHAMA Uncontrollable.

Uncontrollable.

Roger.

Understood.

Put your heart into it.

If you've lost pitch control, elevator

If you've lost pitch control, elevator

control, an airplane will fall into an oscillating

series of climbs and descents...

a fugoid.

a fugoid.

The plane will pitch up until it runs out of speed.

It will then nose down into a descent.

It will then nose down into a descent.

It will pick up speed and momentum.

As the wings begin to generate more lift,

the plane will again begin a climb.

the plane will again begin a climb.

The pilots try using engine power to turn

the airplane towards Haneda.

the airplane towards Haneda.

By increasing power on the left side,

the plane would turn to the right.

the plane would turn to the right.

Increasing power on the right side,

the airplane would turn to the left.

It worked.

The 747 starts a slow turn to the right.

The 747 starts a slow turn to the right.

We are making an emergency descent.

We are making an emergency descent.

Put on your oxygen mask.

Fasten seatbelts.

Don't worry.

The pilots have turned us back.

We will be landing in Haneda soon.

We will be landing in Haneda soon.

OK?

Fasten seatbelts.

Still at 22,000 feet, the captain can see Haneda

Still at 22,000 feet, the captain can see Haneda

in the distance, 81 miles away.

Can you hold?

Can you hold?

The crew reflexively thought, let's

get this plane back to Haneda.

get this plane back to Haneda.

And why Haneda and not somewhere closer?

Because they were familiar with Haneda.

Haneda is within reach,

Haneda is within reach,

but the plane's erratic behavior is worsening.

And the pilots are at the breaking point.

Put on your oxygen mask.

Put on your oxygen mask.

Fasten seatbelts.

In the cabin, emergency masks

are running out of oxygen.

are running out of oxygen.

Fasten seat belts.

We are making an emergency descent.

I don't understand what's happening.

For 14 minutes, the crew of Japan Airlines 123

For 14 minutes, the crew of Japan Airlines 123

has been struggling to control their 747.

has been struggling to control their 747.

They can't get the plane to descend.

Gear, down.

Gear, down.

Lowering the landing gear, dumping all

of that machinery down into the air stream,

of that machinery down into the air stream,

will slow a plane down by vastly increasing the amount of drag,

helping it to descend.

It doesn't work.

The gear won't go down.

Ah.

Ah.

Let's try the alternate.

In an emergency situation

In an emergency situation

like a hydraulic failure, the crew can lower

the landing gear with gravity.

However, once the gear is down, it cannot be pulled back again.

However, once the gear is down, it cannot be pulled back again.

Lower!

Lower!

Yes.

Yes.

Gear coming down.

Really, they're just trying desperation moves

Really, they're just trying desperation moves

here, trying to find the right configuration to stabilize

the plane as best they can.

Keep the nose down.

Keep the nose down.

Yes.

With the landing gear down,

With the landing gear down,

the aircraft begins to slow.

We are descending now.

15 minutes after the incident began,

15 minutes after the incident began,

Japan Airlines 123 is finally losing altitude.

Japan Airlines 123 is finally losing altitude.

The gamble has paid off.

It's not in what I would call controlled flight,

but it's a steadier condition than it was in.

but it's a steadier condition than it was in.

And it's descending now into lower altitudes, where

passengers can breathe again.

passengers can breathe again.

Hold it here.

We're over Lake Sagami.

We're over Lake Sagami.

Just ahead, the pilots see

the familiar lights of Tokyo.

But the captain's optimism vanishes

when the plane suddenly banks hard to the left.

when the plane suddenly banks hard to the left.

This may be hopeless.

This may be hopeless.

Lower than those more.

Roger.

Understood.

Understood.

Keep heading 090 for runway 22.

Whoa!

Whoa!

As the plane descends below 10,000 feet,

the situation worsens.

It's uncontrollable again.

Watch out for the mountain!

So then it suddenly begins descending

So then it suddenly begins descending

at a high rate of speed directly towards the mountains.

Japan Airlines 123 is flying directly away

Japan Airlines 123 is flying directly away

from Haneda Airport, heading straight

towards the high terrain north of Mount Fuji.

towards the high terrain north of Mount Fuji.

Right turn or we will hit the mountains!

Right turn or we will hit the mountains!

Yes!

9 minutes after lowering the landing gear,

the plane has descended 15,000 feet.

the plane has descended 15,000 feet.

Where did he go?

Flight 123 drops below the peaks

of the surrounding mountains, out of range of Tokyo's radar.

of the surrounding mountains, out of range of Tokyo's radar.

Max power.

Max power.

Incredibly, the pilots are able to arrest

Incredibly, the pilots are able to arrest

the dramatic dive.

The plane begins a very abrupt pitch up,

The plane begins a very abrupt pitch up,

so much so that now they're very worried about the airplane

stalling at the top of that climb.

When the airspeed drops to 108 knots,

When the airspeed drops to 108 knots,

the stick shaker activates.

Increase power.

Not good! We're stalling!

The plane slows to 108

knots, which is beyond the stall margin for a 747.

knots, which is beyond the stall margin for a 747.

How they didn't just drop out of the sky at that point,

How they didn't just drop out of the sky at that point,

I'm not sure.

We're losing altitude!

Raise the nose!

Raise the nose!

The flight crew is exhausted.

For 25 minutes they have fought for control,

For 25 minutes they have fought for control,

as they continued to fly away from Haneda Airport.

Flaps?

Flaps?

The first officer suggests deploying

the flaps, which may help them stabilize the airplane,

allow them to fly at a slower speed without stalling.

Extend the flaps!

Flaps coming out.

Flaps coming out.

Because the normal hydraulic deployment

is, obviously, unavailable.

When flaps are deployed electrically,

When flaps are deployed electrically,

they come out very, very slowly.

For more than a minute,

Flight 123 flies almost normally.

Flight 123 flies almost normally.

Left turn!

Left turn!

As the crew attempts a left turn back to Haneda,

the plane banks hard to the right.

the plane banks hard to the right.

Japan Air 123 requests position.

Your position is 45 miles northwest of Haneda.

Your position is 45 miles northwest of Haneda.

Unknown to the pilots, the flaps on each wing

Unknown to the pilots, the flaps on each wing

are extending at different speeds.

What's happened is the flaps on the left side

have come down faster than the flaps on the right side.

have come down faster than the flaps on the right side.

This has caused the left wing to produce

a lot more lift, which is turning

a lot more lift, which is turning

the plane hard to the right.

The nose!

The uneven flaps make the situation worse.

The uneven flaps make the situation worse.

The nose!

4,000 feet from the ground, Japan Airlines 123

4,000 feet from the ground, Japan Airlines 123

is dropping fast, losing 15,000 feet a minute.

is dropping fast, losing 15,000 feet a minute.

Raise the nose.

Raise the nose!

Quite soon, we will

Quite soon, we will

be making an emergency landing.

The pilots use all their strength

The pilots use all their strength

to regain control.

I can't hold it much longer!

But nothing works.

But nothing works.

Flaps up!

Flaps up!

Sides up!

Raise the nose!

Raise the nose!

Power!

Japan Airlines Flight 123 crashes into a mountain

Japan Airlines Flight 123 crashes into a mountain

northwest of Tokyo.

When rescuers reached the site the next morning,

When rescuers reached the site the next morning,

they find devastation.

Only the left wing and rear section of the aircraft

Only the left wing and rear section of the aircraft

are recognizable.

As rescuers examine the tail section,

As rescuers examine the tail section,

they make an astonishing discovery.

There are four survivors.

To have made it out

and to have survived the next 15 or so hours

and to have survived the next 15 or so hours

under the wreckage in the wilderness,

I don't know how it happened.

But it did.

But it did.

520 people have died...

the deadliest single plane crash in history.

the deadliest single plane crash in history.

Japan's Air Accident Investigation

Japan's Air Accident Investigation

Commission, or AAIC, is soon joined by experts

from the NTSB and Boeing.

We were working down there in this terrible carnage,

and family members had already been

and family members had already been

brought up to the mountain.

And they built little altars.

And they built little altars.

I mean, that's... that's...

I get chills thinking about it.

One of the survivors is Yumi Ochiai,

One of the survivors is Yumi Ochiai,

the off-duty flight attendant.

She's able to talk.

She's able to talk.

Though injured, Yumi is

able to speak to investigators.

able to speak to investigators.

Yumi, can you tell me what you remember?

We were ascending when something exploded behind me.

We were ascending when something exploded behind me.

Investigators discover that, 12

minutes into the flight over Sagami Bay,

minutes into the flight over Sagami Bay,

there was an explosion.

The survivor's account gives investigators

their first big clue.

After the sound of the explosion,

After the sound of the explosion,

Mrs. Ochiai saw a white fog.

And this white fog is a result of a sudden decompression.

And this white fog is a result of a sudden decompression.

Immediately after decompression,

Immediately after decompression,

the flight attendant describes seeing a hole in the fuselage.

Thank you.

Based on the survivor's account,

investigators are immediately suspicious.

investigators are immediately suspicious.

Right now it's a bomb.

Right now it's a bomb.

That's what the crime guys are telling us.

Japan is already on high alert.

Japan is already on high alert.

Two months before the crash, a bomb

detonated at Narita Airport on the same day

detonated at Narita Airport on the same day

that an Air India 747 fell from the sky

off the coast of Ireland.

off the coast of Ireland.

There was all kinds of concern internationally, and in Japan,

There was all kinds of concern internationally, and in Japan,

that we had a terrorist group trying to blow

airplanes out of the sky.

Let's keep an open mind and look for something else.

Well, even if you think it might be a bomb,

that's speculation.

that's speculation.

The 747 was one of the more popular airplanes

in service at this time.

And we were worried that, if it was something else,

And we were worried that, if it was something else,

it might ground the airplanes.

it might ground the airplanes.

Make sure we catalog everything.

With the black boxes sent off for analysis,

investigators examine the wreckage in an aircraft hangar.

investigators examine the wreckage in an aircraft hangar.

Let's test for explosive residue near the back.

Let's test for explosive residue near the back.

I had this package of glass bottles, and cotton swabs,

and tweezers, and alcohol, and water,

and tweezers, and alcohol, and water,

and diligently swabbed the aft lab walls

and sent the samples back to the company in Seattle.

To reconstruct the final 30 minutes of the flight,

To reconstruct the final 30 minutes of the flight,

they turn to the radar track.

Almost 24,000 feet over Sagami Bay.

Almost 24,000 feet over Sagami Bay.

Yeah.

As investigators zero in

As investigators zero in

on how and where the incident began, they get a break.

Hey.

Hey.

That's our plane.

A witness on the ground

took a photo of the plane during the incident.

took a photo of the plane during the incident.

A piece of the tail missing.

Vertical stabilizer is pretty much gone.

Vertical stabilizer is pretty much gone.

Losing a vertical fin has never happened

to an airliner this big before.

to an airliner this big before.

The airplane had lost most of its tail.

And it makes sense that investigators

And it makes sense that investigators

were focused on the possibility of an in-flight explosion,

a bomb.

a bomb.

Missing tail... and Yumi Ochiai said

there was a hole behind her.

It all adds up, but we need the tail to prove it.

It all adds up, but we need the tail to prove it.

The day after the crash of Japan Airlines Flight

The day after the crash of Japan Airlines Flight

123, part of the missing tail is found floating

in Sagami Bay, south of Tokyo.

in Sagami Bay, south of Tokyo.

So what do you think?

Investigators examine the tail, looking for any clues

that point to a bombing.

that point to a bombing.

There's no fire damage.

No shrapnel damage?

No shrapnel damage?

But that's not what they find.

Nothing really looks like bomb damage.

Nothing really looks like bomb damage.

There's a lot of telltale signs.

I saw none of that.

Until they get the swab results back from the lab,

they can't rule out a bomb entirely.

they can't rule out a bomb entirely.

So you were the controller that handled Japan Air 123.

Right?

Correct.

Correct.

Investigators speak to the controller

who was in contact with the crew for 32 minutes.

who was in contact with the crew for 32 minutes.

Did the pilots say anything about what

happened to the plane?

Right from the start they said it was uncontrollable.

Right from the start they said it was uncontrollable.

Hmm.

Did they say why?

No.

But they did mention to dispatch something about damage

But they did mention to dispatch something about damage

to a door.

Hmm.

The R5 door is broken.

We're making an emergency descent.

Thank you.

That's very helpful.

That's very helpful.

The pilot reported that the door

may have come off.

And there was a concern that, if the door came off,

And there was a concern that, if the door came off,

it may have damaged the airplane.

The right rear door is here, behind our survivor.

The right rear door is here, behind our survivor.

Maybe that's the opening our survivor described.

Maybe that's the opening our survivor described.

That would explain the depressurization.

There is a precedent there.

In 1974, the cargo door of a Turkish Airlines DC-10

In 1974, the cargo door of a Turkish Airlines DC-10

had blown off, causing instant decompression of the cabin

had blown off, causing instant decompression of the cabin

and failure of the cabin floor, resulting

in the loss of flight control.

A door is big, so they could definitely

do damage to the tail.

Enough damage to knock it right off the plane?

Enough damage to knock it right off the plane?

Several days after the crash, the right rear door

is found.

is found.

Looks like the door was locked.

And it was found with the rest of the wreckage.

And it was found with the rest of the wreckage.

So it didn't fall off in flight.

It was a good theory.

It was a good theory.

I know.

We're missing something.

We're missing something.

We are back to square one.

We are back to square one.

No trace of explosives found on the wreckage.

No trace of explosives found on the wreckage.

Flight 123 was not brought down by a bomb.

Flight 123 was not brought down by a bomb.

Well, one thing's for sure.

Something happened in the back of that plane.

Something happened in the back of that plane.

Was there a structural issue?

Was there a design issue, even, which might affect

Was there a design issue, even, which might affect

more 747s than just this one?

We really needed to get an answer to that.

We really needed to get an answer to that.

We need to reassemble the tail.

While investigators focus on the rear of the plane,

the Japanese government orders inspections

the Japanese government orders inspections

of all 747 tail assemblies.

Around the world, the safety of the 747 is questioned.

Around the world, the safety of the 747 is questioned.

There was moves by the Europeans

There was moves by the Europeans

and the Brits to ground the 747.

And that would have had terrible economic impact

And that would have had terrible economic impact

on the United States.

So from the first emergency call to the crash,

it was almost 32 minutes.

it was almost 32 minutes.

The team turned to the cockpit

voice recorder for clues.

voice recorder for clues.

Let's hear it.

Get quick.

FLIGHT ATTENDANT (ON RECORDING): Thank you.

Sounds normal.

It's just a flight attendant asking

for something on the intercom.

for something on the intercom.

Whoa.

Something exploded?

We know there was definitely not a bomb.

But did you hear that?

Let's roll it back.

Let's roll it back.

Yeah, I heard that.

That was two explosions.

We didn't know what the boom, boom was

We didn't know what the boom, boom was

when we heard it on the CVR.

OK.

OK.

Let's assume that the first explosion was a decompression

somewhere behind Yumi.

What about the second one?

What about the second one?

Let's just keep listening.

FIRST OFFICER (ON RECORDING):

Don't bank so much.

Don't bank so much.

It's manual.

Turn it back.

It won't go back.

Hydraulics are all out.

The 747 has four hydraulic systems that

control the rudder, elevator, ailerons,

control the rudder, elevator, ailerons,

flaps, and landing gear.

Two booms and no hydraulics.

Two booms and no hydraulics.

Yeah, they had a lot to deal with.

For investigators, it's an important clue.

For investigators, it's an important clue.

If you lose all your hydraulic systems on the airplane,

you don't have any control over the flight controls.

you don't have any control over the flight controls.

It's no wonder they told ATC they were uncontrollable.

So having gone away from the door,

we began focusing on the aft end of the airplane.

we began focusing on the aft end of the airplane.

Somehow they're all connected.

Somehow they're all connected.

Let's try to pinpoint the cause of the decompression.

The team scours the reconstruction

The team scours the reconstruction

of the tail section of Japan Airlines Flight 123,

looking for evidence of what caused the first explosion.

looking for evidence of what caused the first explosion.

The United States needed to determine

the cause of this accident because we

the cause of this accident because we

manufactured the 747.

We were concerned that we had a structural flaw

We were concerned that we had a structural flaw

in the airplane.

And others were worried too.

OK.

Let's start here... the rear pressure bulkhead.

Let's start here... the rear pressure bulkhead.

The rear pressure bulkhead

The rear pressure bulkhead

stands more than 13 feet high.

Shaped like an umbrella, it acts like a cork

Shaped like an umbrella, it acts like a cork

in a champagne bottle, keeping the cabin pressurized.

Any explosion in the rear of the aircraft

Any explosion in the rear of the aircraft

could explain the sudden depressurization.

That's when we decided

That's when we decided

we need to focus on that area, on the bulkhead,

and see what happened there.

The team recovers the rear pressure bulkhead

from the crash site, and painstakingly reconstructs it

from the crash site, and painstakingly reconstructs it

over several days.

So this is it, huh?

So this is it, huh?

Yeah.

At 24,000 feet, that's over a quarter

million pounds of pressure.

million pounds of pressure.

That's a lot of force.

The rear pressure bulkhead

has to hold the pressure inside the airplane.

has to hold the pressure inside the airplane.

It's got to be very, very strong.

It's got to be fail-safe, and it needs to do its job reliably.

It's got to be fail-safe, and it needs to do its job reliably.

Look.

This damage here is from the crash.

This damage here is from the crash.

These... these rips are from the plane

slamming into the mountain.

Yeah?

Yeah?

One of the things that investigators are trained to do

and eventually learn to do is to look for anything

that's out of the ordinary.

that's out of the ordinary.

Check this out.

This isn't crash damage.

This is a rupture.

Yeah, and a clean one at that.

Look.

It runs mainly along this line of rivets.

The straight line fracture

The straight line fracture

certainly piqued our curiosity as to what this was all about.

certainly piqued our curiosity as to what this was all about.

Investigators discover a rupture 41 inches long.

Because of this long, flat area that we saw,

Because of this long, flat area that we saw,

it made us very curious that this thing had

ruptured instantaneously and caused

ruptured instantaneously and caused

this explosive decompression.

What could have caused the long rupture?

What do you have?

The team examines a piece of metal

from where the rupture occurred.

from where the rupture occurred.

Striations... lots of 'em.

Under close examination,

Under close examination,

they discover a web of radiating contours called striations.

They are telltale signs of growing cracks.

They are telltale signs of growing cracks.

Every time a little fatigue progresses it leaves a mark,

Every time a little fatigue progresses it leaves a mark,

what they call striations.

It's long-term metal fatigue.

Yeah.

Yeah.

Every flight, every time they pressurize the cabin,

those fatigue cracks would have grown.

If microscopic cracks form under rivets

If microscopic cracks form under rivets

on the pressure bulkhead, they would continue

to grow with the forces of the plane

to grow with the forces of the plane

being repeatedly pressurized.

So once the airplanes in service,

So once the airplanes in service,

these cracks start developing.

But they start under the rivet heads,

where you can't see them.

where you can't see them.

And even once they progress outside,

they're very difficult to see.

Because they're only a few millimeters long.

Because they're only a few millimeters long.

Why did the cracks form in the first place?

Why did the cracks form in the first place?

Yeah.

The pressure bulkhead is one of the strongest parts of a 747.

The design philosophy

The design philosophy

for the pressure bulkhead included a fail-safe design.

for the pressure bulkhead included a fail-safe design.

If this rear pressure bulkhead had a fatigue crack begin,

it would stop because there's a piece called a crack stopper.

it would stop because there's a piece called a crack stopper.

The rear pressure bulkhead consists of five bays.

Each bay is separated by a strap or a crack stopper designed

Each bay is separated by a strap or a crack stopper designed

to contain a small crack and prevent it

to contain a small crack and prevent it

from spreading to other bays.

So why did this rupture spread beyond the crack stopper?

So why did this rupture spread beyond the crack stopper?

Investigators dig into the maintenance

history of the aircraft.

history of the aircraft.

Maybe this will help.

This plane had a previous accident.

Seven years earlier, the plane had

an incident landing in Osaka.

an incident landing in Osaka.

It suffered a hard tail strike.

It suffered a hard tail strike.

Severe damage to the rear pressure bulkhead.

Keep going.

Keep going.

Bottom of the bulkhead was crushed, sent for repairs.

In this Osaka incident,

the airplane's tail did hit the runway pretty hard.

the airplane's tail did hit the runway pretty hard.

And it wore through the skin and actually

damaged some structure, including the rear bulkhead.

damaged some structure, including the rear bulkhead.

Instead of replacing the entire bulkhead,

Instead of replacing the entire bulkhead,

Boeing engineers decided to replace

only the damaged lower half.

only the damaged lower half.

Once the repair is made, it should

be as strong or stronger than when the airplane

be as strong or stronger than when the airplane

was originally made.

Well, this is the original bulkhead.

This is the new bulkhead.

Maybe the repair is the issue.

This kind of cracking in the same area

This kind of cracking in the same area

that the repair was, was really more of a coincidence

that the repair was, was really more of a coincidence

than we could have imagined.

So how did you fit the new bottom

to the top of the bulkhead?

Investigators look into the 1978 repair

Investigators look into the 1978 repair

more closely.

That was a really big job.

Technicians worked around the clock for eight days

inside the plane to mount and secure a new lower

inside the plane to mount and secure a new lower

bulkhead to the upper section.

Did you notice anything out of the ordinary?

There was only one small thing.

There was only one small thing.

Now just a little higher.

During the repair, technicians

During the repair, technicians

had difficulty connecting the upper pieces

to the lower pieces.

There's not enough overlap.

There's not enough overlap.

What do you mean?

We had trouble fitting the overlap

We had trouble fitting the overlap

at the 9 o'clock position.

The difficulties with the repair match

exactly where the bulkhead failed.

exactly where the bulkhead failed.

Hmm.

OK.

Thanks for your help.

Thanks for your help.

Investigators are now confident that the repair

seven years ago is connected to the crash.

seven years ago is connected to the crash.

Now we're getting somewhere.

OK.

Normally, the top and bottom are held together

Normally, the top and bottom are held together

with two rows of rivets.

Yeah?

Investigators scrutinized the repair of

Investigators scrutinized the repair of

Flight 123's pressure bulkhead.

Right.

Right.

And they did that everywhere except for right here.

One area of the bulkhead, the skin

did not overlap enough.

did not overlap enough.

Boeing had to design a patch, a repair.

Boeing had to design a patch, a repair.

It was called a splice.

Without enough space for two rows of rivets

Without enough space for two rows of rivets

in the overlap, a separate splice plate

is attached over the area.

But only one row of rivets showed signs of metal fatigue.

It's hard to tell how the repair was done.

It's hard to tell how the repair was done.

We knew that there was supposed

to be a splice plate there.

But it was evident to me that there was just one row

But it was evident to me that there was just one row

of rivets taking up the load.

It didn't look right.

It didn't look right.

They used two different splice plates.

And by using two different splice plates,

they compromised the repair.

they compromised the repair.

Investigators discover the repair

Investigators discover the repair

team cut the splice plate in two, perhaps

for easier installation.

for easier installation.

The lower plate helped secure the overlap.

The upper plate did not.

The upper plate did not.

That one row of rivets

was insufficient to sustain the loads,

was insufficient to sustain the loads,

and eventually fatigue cracks started

and the whole section failed.

and the whole section failed.

The fracture followed the gap between the two splice plates.

This particular 747SR

This particular 747SR

had accumulated over 18,000 cycles in its 12-year career

with JAL.

with JAL.

That's just an astonishing number.

V1.

Rotate.

Each one of those cycles,

each one of those takeoffs and landings,

meant pressurization and depressurization cycles.

meant pressurization and depressurization cycles.

The real bulkhead now had a weak spot.

The real bulkhead now had a weak spot.

It was sort of like a ticking time bomb ready to fail.

It was sort of like a ticking time bomb ready to fail.

That's it.

That's got to be it.

It's what investigators

call the golden nugget.

call the golden nugget.

We... we found the a-ha, that's the cause.

We... we found the a-ha, that's the cause.

There is no question

that, if done correctly, the repair would not have failed.

that, if done correctly, the repair would not have failed.

Investigators have discovered what

caused the rapid decompression.

caused the rapid decompression.

But they still need to understand

why the tail detached.

why the tail detached.

The bulkhead rupture's here.

And all that pressurized cabin it's got to go somewhere.

Now, the shock wave flows up the tail,

Now, the shock wave flows up the tail,

and it must have just popped off like a champagne cork.

and it must have just popped off like a champagne cork.

The first boom was the failure of the bulkhead.

The first boom was the failure of the bulkhead.

And the second one was after the vertical tail pressurized

and it failed.

and it failed.

Hey, check this out.

Hey, check this out.

All four hydraulic lines run through the tail section.

So when the decompression happens,

So when the decompression happens,

not only do they lose a chunk of that tail,

they lose all those lines as well.

they lose all those lines as well.

In this case, all four hydraulic lines

went up the vertical fin.

So that was a poor design.

So that was a poor design.

It was just considered so unlikely, so

It was just considered so unlikely, so

inconceivable that all four systems would in some way

be disabled.

But that's exactly what happened.

But that's exactly what happened.

It's a design flaw that

rendered the rest of the plane's flight controls useless.

rendered the rest of the plane's flight controls useless.

Don't bank so much.

OK.

OK.

Don't bank so much!

Hydraulic pressure has dropped.

Hydraulic pressure has dropped.

Without any hydraulics to control elevators, rudder,

or ailerons, Flight 123 flew an erratic flight

or ailerons, Flight 123 flew an erratic flight

path for 32 terrifying minutes.

Raise the nose.

Raise the nose!

The two pilots used all their strength

to regain control.

I can't hold it much longer.

I can't hold it much longer.

But nothing worked.

Flaps up!

Flaps up!

Sides up!

Sides up!

Raise the nose!

Terrain.

Power!

What began as a repair seven years earlier...

...set the stage for a devastating crash that

took the lives of 520 people...

took the lives of 520 people...

the worst single aircraft accident of all time.

The initiation and propagation of the fatigue cracks...

The initiation and propagation of the fatigue cracks...

A series of recommendations

takes direct aim at the original 747 design.

takes direct aim at the original 747 design.

Operators are ordered to install a cover

in the tail to protect the vertical fin

against a bulkhead decompression.

The improper repair...

Emergency cutoff valves

Emergency cutoff valves

are also recommended to prevent a total loss

of hydraulic pressure.

One way they can do

One way they can do

this is to put what they call fuses in the hydraulic system.

If you cut the line, the hydraulic fluid

If you cut the line, the hydraulic fluid

would be trapped in the rest of the line.

And they were installed on the 747.

And they were installed on the 747.

Today hydraulic fuses are used on almost

Today hydraulic fuses are used on almost

every commercial airliner.

This accident was a watershed moment

in aviation safety.

in aviation safety.

It pointed up a lot of areas that not only the 747 but other

It pointed up a lot of areas that not only the 747 but other

airplanes flying could be improved

airplanes flying could be improved

right then and for the future, and for future designs.