Original subtitles

NARRATOR: An Airbus A320 en route to Singapore

disappears while flying over the Java Sea.

JOHN: It crossed my mind that what could have caused it

is an act of terrorism, sabotage,

something extreme happening to the aircraft.

NARRATOR: For days, a massive search and rescue effort

turns up nothing.

EMMANUEL: A crash at sea is challenging.

It's difficult to locate because you usually don't have

the full flight path down to the surface of the ocean.

NARRATOR: What they find paints a confounding picture

of the final minutes of flight.

RAY: The plane started to bank.

EMMANUEL: We were very surprised by this action.

RAY: What are they doing?

NARRATOR: The investigation uncovers

a single tragic misunderstanding

that claimed the lives of 162 people.

Flight attendant: LADIES AND GENTLEMEN, WE ARE STARTING OUR APPROACH.

Pilot: WE LOST BOTH ENGINES!

Flight attendant: PUT THE MASK OVER YOUR NOSE.

EMERGENCY DESCENT.

Pilot: MAYDAY, MAYDAY.

Flight attendant: BRACE FOR IMPACT!

Controller: I THINK I LOST ONE.

Man: INVESTIGATION STARTING INTO THIS TRAGEDY...

Man: HE'S GONNA CRASH!

♪

NARRATOR: AirAsia Flight 8501 cruises high above the Java Sea

north of Indonesia.

It's a few days after Christmas,

and many of the 156 passengers aboard the Airbus A320

are on holiday.

The pilot in command is 53-year-old Captain Iriyanto.

He's highly experienced,

with more than 20,000 hours in the air.

His first officer is French national Remi Emmanuel Plesel.

He is 46 with about 2,000 flight hours,

much of it on the Airbus.

JOHN: On this particular leg, it was the first officer

that was manipulating the controls.

The captain was in command of the flight

but was performing the duties of the pilot monitoring,

or the non-flying pilot.

NARRATOR: Today's flight originated in the Indonesian city

of Surabaya. It's heading across the Java Sea to Singapore.

Total flight time is expected to be two hours.

♪

FO. PLESEL: It looks like weather ahead.

CPT. IRIYANTO: No. I don't like the looks of that.

NARRATOR: Twenty-two minutes into the flight,

the pilots notice bad weather ahead on their radar.

FO. PLESEL: Anti-ice? CPT. IRIYANTO: Anti-ice on.

JOHN: The crew would definitely be taking care

to avoid penetrating these thunderstorms

because it contains possibly extreme turbulence, hail,

lightning, everything that the air crew don't want

to expose themselves and the passengers to.

NARRATOR: The captain instructs the flight attendant

to prepare the cabin for turbulence.

FLIGHT ATTENDANT: Ladies and gentlemen,

please return to your seats and fasten seat belts.

♪

NARRATOR: Khairunnisa Haidar Fauzi

is one of four flight attendants

helping to look after the passengers

as they cruise at 32,000 feet.

♪

As an additional precaution, the captain decides

to increase altitude, to go above the storm clouds

in their path.

CPT. IRIYANTO: I'm gonna radio for a higher cruise,

get around that weather.

FO. PLESEL: Good idea. AUTOMATION:

NARRATOR: But before the captain

can contact air traffic control,

he gets a fault warning from the flight computer.

FO. PLESEL: ECAM actions?

NARRATOR: The plane's sophisticated computers

give the pilots step-by-step instructions

on how to fix the issue.

CPT. IRIYANTO: FAC 1 off and on.

FAC 2 off and on.

CPT. IRIYANTO: Warning cleared.

NARRATOR: Computers control most of the Airbus A320's systems.

JOHN: There are basically seven computers that fly the aircraft,

and they add a lot of helpful features

that take workload away from the pilot.

NARRATOR: Pilots are trained to follow the instructions

given by the aircraft's computers.

AUTOMATION:

NARRATOR: A few minutes later, the warning sounds again.

CPT. IRIYANTO: Same. FAC 1 off and on.

NARRATOR: After addressing the fault warning,

the captain radios air traffic control

to request the higher flight level.

CPT. IRIYANTO: Okay. So Jakarta air traffic control,

AirAsia 8501, request climb to 38,000.

NARRATOR: The Jakarta air traffic controller

has had an uneventful night.

He soon clears the pilots to climb,

but to a slightly lower altitude

than the 38,000 feet requested.

AIR TRAFFIC CONTROLLER: AirAsia 8501, you are cleared to 3-4-0.

NARRATOR: After permitting them to climb,

the controller waits for confirmation.

AUTOMATION:

NARRATOR: But the pilots are distracted by a third alarm.

CPT. IRIYANTO: Here we go again. FO. PLESEL: ECAM actions.

CPT. IRIYANTO: FAC 1 off and on.

NARRATOR: The controller hasn't heard back,

so he repeats his message.

AIR TRAFFIC CONTROLLER: AirAsia 8501, you are cleared to 3-4-0.

JOHN: It's very annoying and very time consuming

to deal with this recurring problem.

CPT. IRIYANTO: Enough of this.

FO. PLESEL: ECAM actions.

♪

NARRATOR: The controller still hasn't heard confirmation

from the pilots.

AIR TRAFFIC CONTROLLER: AirAsia 8501, do you read me?

Please, acknowledge.

♪

AUTOMATION:

NARRATOR: But in the cockpit, the fault warnings have escalated.

AIR TRAFFIC CONTROLLER: AirAsia 8501, do you read me?

Please, acknowledge.

NARRATOR: In the cabin, passengers have no idea

their pilots are struggling to maintain control of the plane.

♪

♪

The pilots now notice that the plane is rolling sharply left.

CPT. IRIYANTO: Level. Okay. Level.

NARRATOR: Something is going terribly wrong with Flight 8501.

The first officer is struggling.

CPT. IRIYANTO: Level!

NARRATOR: But soon the plane is rolling again.

CPT. IRIYANTO: Level! FO. PLESEL: I'm trying.

NARRATOR: The pilots can't seem to regain control.

FO. PLESEL: It's not responding.

AIR TRAFFIC CONTROLLER: AirAsia 8501, please confirm.

You are climbing to flight level 3-4-0.

NARRATOR: The controller still hasn't heard confirmation

from the pilots when the plane starts to climb

towards 34,000 feet

and then continues climbing steeply even higher.

♪

JOHN: No airline passenger

would have ever experienced something like this

under normal circumstances before.

It would have been a very violent, shocking maneuver.

CPT. IRIYANTO: Pull down! FO. PLESEL: It's not correcting.

NARRATOR: The plane seems to have taken on a life of its own.

It climbs higher and higher as the pilots fight to level off.

Then, inexplicably, the plane starts to drop.

JOHN: That would certainly cause near panic in some people.

Other people would be waiting for the pilots to quote fix it.

CPT. IRIYANTO: Altitude! FO. PLESEL: I see it!

NARRATOR: Flight 8501 is plummeting from the sky,

speeding toward the ocean below.

JOHN: The rate of descent here was very, very high.

NARRATOR: It seems the pilots can do nothing

to save their plane.

CPT. IRIYANTO: Pull!

FO. PLESEL: It's not correcting. What's going on? Max power.

CPT. IRIYANTO: Slowly.

♪

NARRATOR: Forty-three minutes into what should have been

a normal two-hour flight...

FO. PLESEL: Ugh!

NARRATOR: AirAsia Flight 8501 disappears from radar.

CPT. IRIYANTO: Pull! FO. PLESEL: I'm trying!

CPT. IRIYANTO: Pull! FO. PLESEL: It's not correcting! Ugh.

♪

♪

NARRATOR: News quickly spreads of the mysterious disappearance

of a commercial flight to Singapore.

♪

JOHN: The loss of AirAsia 8501 was a classic case of a flight

degenerating from mundane, normal cruise conditions

to the loss of the aircraft in a span of just twenty minutes.

NARRATOR: Within hours, relatives of the 162 passengers

and crew are demanding answers.

How could an airplane just disappear?

TONY (Archive): We don't want to speculate right now

because the plane has been missing for twelve hours,

and there's a deep sense of depression.

NARRATOR: All the authorities know is that the plane vanished

from radar somewhere over the Java Sea.

Speculation runs wild

about what could have brought the airliner down.

JOHN: It crossed my mind that what could have caused it

is an act of terrorism, sabotage,

something extreme happening to the aircraft.

But it was very difficult to come up with a clear picture

on the first news reports as to what had taken place.

NARRATOR: It's been only a few months

since Malaysia Airlines Flight 370 disappeared

in eerily similar circumstances, vanishing from radar

without sending any mayday call.

Search and rescue vessels are dispatched,

but combing the vast and choppy sea between Sumatra and Borneo

is a mammoth task.

An international team of air safety investigators

flies in to join the local experts in Jakarta.

Ray Nurcahyo is an air crash investigator

with the Indonesian National Transportation Safety Committee.

RAY: The air traffic control radar data is our main source

to detect the location of the aircraft.

NARRATOR: They begin by interviewing the air traffic controller.

RAY: So can you tell me what happened?

EMMANUEL: They were the ones who could tell us

a little bit more about what had happened.

They had seen the plane trajectory,

the plane flight path.

NARRATOR: They learn that the plane was flying towards an area

of bad weather.

JOHN: When you start out in an investigation,

you look at everything.

In this case, there were weather considerations.

RAY: And then?

AIR TRAFFIC CONTROLLER: Then, they started losing altitude fast.

♪

NARRATOR: And then, it disappeared from radar at 24,000 feet.

RAY: Thank you very much.

EMMANUEL: How could this plane being in cruising altitude

suddenly climb and fall with a very high rate of descent?

NARRATOR: Could the aircraft have lost engine power

in a violent storm?

RAY: The weather might be involved in the accident.

So we tried to get more information on the weather data.

♪

RAY: Can I get the weather overlay for this map, please?

NARRATOR: Investigators examine detailed weather charts

from the day of the accident.

RAY: There were thunderstorms here and here.

RAY: It's quite a large red color, so I assumed

there has been a bad condition on that area.

JOHN: It was monsoon season,

and so there's a lot of thunderstorms.

They can do damage to the airplane that --

it's something that you learn early as a pilot,

and it's something that you adhere to very strongly.

You do not fly through thunderstorms.

NARRATOR: Then they start mapping the flight track

to see if the plane could have entered the storms.

RAY: They were at cruising altitude.

Then here they asked for deviation.

They made it here and then they started to drop.

They almost flew into the first storm but then just missed it.

NARRATOR: Bad weather, the first possible explanation

for the disappearance of Flight 8501, proves to be a dead end.

RAY: This is the spot they were last seen on radar.

NARRATOR: Based on Flight 8501's last radar coordinates,

investigators have at least narrowed down the search area.

Dozens of rescue vessels and aircraft from multiple countries

scour the target area.

EMMANUEL: A crash at sea is challenging.

It's difficult to locate because you usually don't have

the full flight path down to the surface of the ocean.

NARRATOR: The Indonesian president decides to address

a nation in mourning.

PRES. WIDODO (Archive, translated): To all the families

of the passengers and crew,

I share my loss with you

in this tragedy.

And we all pray.

NARRATOR: Two days into the search, the first pieces

of wreckage are recovered from the Karimata Strait

in the Java Sea.

RAY: The main wreckage was found not far from the point

that we predicted based on the ATC radar.

♪

NARRATOR: Soon searchers are finding bodies.

Among the first is that of flight attendant

Khairunnisa Haidar Fauzi.

In a moving tribute, hundreds attend her funeral.

Funerals for many more follow.

Of the 162 passengers and crew, there are no survivors.

♪

As the wreckage is brought in for examination,

investigators can see that the task ahead of them is daunting.

Why would a highly sophisticated airliner,

flying at cruising altitude, suddenly fall from the sky?

EMMANUEL: We had a lot of little pieces everywhere.

My first reaction was it's not gonna be easy.

♪

♪

RAY: Is it all like this?

EMMANUEL: A crash at sea is challenging

because usually the main interesting parts are underwater

and that's a little bit difficult to get them.

NARRATOR: With much of the plane still missing

at the bottom of the sea,

investigators study debris found floating on the surface.

To see if the plane exploded,

they look for distinctive smaller pieces with burnt edges.

♪

JOHN: The debris that was recovered did not exhibit any

telltale signs of having been subject to a bomb explosion.

RAY: This plane didn't blow up.

NARRATOR: The pieces of AirAsia 8501 are large and clean.

EMMANUEL: We could eliminate a possible in-flight break up.

NARRATOR: It's a step forward, but unless they can find

the black boxes, the mystery of AirAsia Flight 8501

may never be solved.

The flight recorders offer the only hope of figuring out

what was happening in the cockpit.

The search for them goes into high gear.

RAY: The black box search team, assisted by Singapore, France,

the UK and China, we utilized side scan sonar

and underwater unmanned camera.

NARRATOR: All black boxes are equipped

with an electronic beacon that transmits a signal under water.

Ship-based sonar systems can detect the signal

and help guide searchers towards the black boxes.

EMMANUEL: When we get this signal, we are in a range

of about two thousand meters from them.

So this helps us narrow it down to where they are

and then the divers then have to try to find them.

NARRATOR: But weather complicates the search.

EMMANUEL: The depth was about forty meters,

and the sea was rough.

And we couldn't go every day we wanted to go.

So we had to adapt our strategy to the weather.

NARRATOR: After a two-week search, they finally succeed.

RAY: The black boxes were found, first on 12th of January,

the flight data recorder.

And the following day we found the cockpit voice recorder

around the same area.

EMMANUEL: We were relieved to get the boxes 'cause

this was a real major step towards the explanation

of what had happened.

♪

NARRATOR: Investigators start by listening

to the cockpit voice recording.

It should reveal pilot conversations and other sounds

from inside the cockpit of Flight 8501.

RAY: Okay, let's start when they ask permission to climb.

Play recording.

CPT. IRIYANTO: Jakarta air traffic control, AirAsia 8501

request climb to 38,000 to clear storm clouds.

EMMANUEL: Up to that point the flight was normal.

It was uneventful.

RAY: Continue recording.

NARRATOR: Almost immediately, investigators make a discovery.

FO. PLESEL: ECAM actions?

CPT. IRIYANTO: FAC 1 off and on.

FAC 2 off and on.

Warning cleared.

RAY: They were dealing with some kind of warning.

Play recording.

AUTOMATION: FO. PLESEL: ECAM actions?

CPT. IRIYANTO: Same.

RAY: Okay. The warning came back.

JOHN: They were getting continual fault warnings through

what's called an ECAM system,

Electronic Central Aircraft Monitoring system.

RAY: Play recording.

AUTOMATION: CPT. IRIYANTO: Here we go again.

FO. PLESEL: ECAM actions?

CPT. IRIYANTO: FAC 1 off and on.

FAC 2 off and on.

It's cleared.

EMMANUEL: At this point, the crew's behavior was standard,

was normal. They were quiet.

They were communicating on what checklists to apply.

AIR TRAFFIC CONTROLLER: AirAsia 8501, you are cleared to 3-4-0.

RAY: Okay, stop. We know from the controller

that he never heard back from them again. Play.

AUTOMATION: CPT. IRIYANTO: There it is again.

FO. PLESEL: ECAM actions?

NARRATOR: Then, the recording reveals something surprising.

CPT. IRIYANTO: No. I've got a better idea.

NARRATOR: The captain appears to have done something different,

and then there's a new warning.

RAY: Hold recording.

Now the autopilot has disengaged.

JOHN: An unexpected disengagement of the auto-throttle

and auto-thrust system results in a pretty loud warning.

This is a very serious concern to the investigators.

AUTOMATION: FO. PLESEL: What was that?

CPT. IRIYANTO: Okay, let's see what we have.

AUTOMATION: FO. PLESEL: Master caution? Why?

CPT. IRIYANTO: Checking...

Level. Level.

NARRATOR: Investigators now hear yet another cockpit warning.

RAY: Stall warning.

JOHN: The airplane would have warnings to tell the pilot

that they were getting close to an aerodynamic stall.

CPT. IRIYANTO: Pull! Slowly! FO. PLESEL: What's going on?

CPT. IRIYANTO: Pull!

NARRATOR: An aerodynamic stall occurs

when the angle between the wings and the oncoming air

gets too steep.

The amount of air flowing over the wings is reduced.

The aircraft loses lift and can no longer stay aloft.

JOHN: It's a highly uncommon event to have an Airbus stall,

particularly in cruise, because it is protected from stalling.

JOHN: Normally the computer won't allow the aircraft to stall.

It won't allow the wings to go at too high an angle

to the airflow and stall the aircraft.

NARRATOR: What caused this technically advanced plane to stall?

RAY: The autopilot disconnects. The aircraft stalls.

They struggle to recover.

It makes no sense.

NARRATOR: Only the FDR data can reveal what

was happening with the aircraft the moment the crisis hit.

♪

Until that data is ready for analysis,

the deadly midair stall remains a mystery.

RAY: What were you guys struggling with?

JOHN: One of the questions that the investigators

would have faced is:

Why and how did an aircraft that is supposed to be stall-proof

end up stalling?

CPT. IRIYANTO: Pull down. Slowly!

♪

NARRATOR: The flight data recorder should provide answers,

but it needs to be flushed of saltwater before it can be read.

In the meantime, investigators

pull the plane's maintenance records to look for clues.

They soon make a discovery.

The aircraft seems to have an issue with its RTLU.

EMMANUEL: RTLU is the Rudder Travel Limit Unit.

The plane had had a history of RTLU failures.

NARRATOR: The Rudder Travel Limit Unit

is a computerized component that prevents the rudder

on the tail from deflecting too far in either direction

when the plane is traveling at high speed.

If the flight computer detects any problems

with its rudder limiter, it sends a warning to the cockpit.

Records show the aircraft's Rudder Travel Limit Unit

had been malfunctioning for almost a year.

RAY: Twenty-three reports of the exact same failure.

JOHN: The RTLU failures on this particular airframe

had become increasingly frequent.

There were eleven in the last couple of months

and twenty-three in the preceding period,

which is highly unusual.

RAY: That seems like a lot of failures with the RTLU.

NARRATOR: Could these be connected to the mystery warnings

the pilots were experiencing? It could be a major breakthrough.

RAY: Three days before the crash there were

two exact same failures.

Why was this happening?

NARRATOR: After each failure, maintenance workers

reset the RTLU.

ERTATA : As long as the reset resulted in the computer to prompt pass,

maintenance personnel doesn't have to investigate further.

RAY: They just kept resetting it

and then putting it back in service.

NARRATOR: But they never found a permanent fix.

JOHN: They were returning the airplane to service after reset,

and from a legal standpoint it did clear the problem.

But obviously whatever the fault was, they hadn't

found it, because the problem continued to reoccur.

NARRATOR: The aircraft seemed to operate perfectly

despite the warnings.

Even the day before the crash, the plane had successfully flown

from Surabaya to Kuala Lumpur.

RAY: Have we got the unit?

NARRATOR: The plane's RTLU is among the wreckage

that's been recovered from the Java Sea.

♪

RAY: Let's send it back to the manufacturer

and see if they can find something.

NARRATOR: The unit is sent to France for analysis.

♪

Finally, investigators get to examine a key piece of evidence,

the flight data recorder.

If they can download all the flight data,

it should provide a detailed picture

of exactly what was happening with the electrical

and mechanical control systems on the aircraft.

RAY: After the black box recovered,

they transferred to our laboratory.

EMMANUEL: We worked with the Indonesian investigation authority

in extracting the data, which requires a lot of precautions,

since the flight recorders had been immersed.

♪

RAY: Move it down too a little bit.

NARRATOR: On examination, they discover the data board

has been damaged by the impact of the crash.

It's uncertain whether the information they desperately

need will be retrievable.

♪

The download begins.

RAY: Even though the condition of the black box was damaged,

we managed to recover all of the data.

NARRATOR: Success.

RAY: Okay, so let's start with those chime warnings.

So here's the first warning. It clearly was the RTLU.

They do the fix, simply resetting the entire system.

AUTOMATION:

JOHN: The procedure to reset the system was much like your PC,

rebooting the PC. They only had to turn the system off

and turn it back on again.

CPT. IRIYANTO: FAC 2 off and on.

RAY: Two more times the RTLU warning goes off,

and each time they did the right thing.

Then it went off on a fourth time.

Then suddenly there was a glitch.

What did they do different?

NARRATOR: After the fourth time, the warnings change.

There is now a fault with the aircraft's two main computers,

known as the flight augmentation computers.

RAY: Put the new data up on that screen.

♪

Something caused both computers to fail at the same time.

NARRATOR: But nothing in the data shows

what the crew did differently after the last warning.

What does come to light is that,

when the autopilot disengaged, the rudder moved slightly.

RAY: Now, let's see.

The plane started to bank to the left.

EMMANUEL: The electrical interruption

on the flight control computers created a rudder movement

of about two degrees to the left.

JOHN: Two degrees does not sound like a lot,

but at the speed they were flying

it's exactly what caused them to roll left 54 degrees.

JOHN: That's almost twice the normal bank

that you would feel in an airliner.

RAY: Now look at this.

It took them nine seconds to do anything about the bank.

NARRATOR: Despite the steep bank angle,

it seems the crew was slow to react and level the plane.

EMMANUEL: During the first nine seconds,

there was no crew inputs on the controls

following this roll that reached fifty-four degrees.

NARRATOR: Then the first officer suddenly reacts,

pulling hard to the right, then left again

and just as suddenly he starts to pull up.

RAY: All they had to do was steady the plane.

What were they doing?

NARRATOR: The FDR data shows that the plane

climbed steeper and steeper

until they reach a remarkable 45-degree pitch up.

RAY: Then it stalled.

NARRATOR: Investigators know that the captain

did something different, something that led

to a computer glitch causing the autopilot to disconnect

and the plane to bank sharply. But they don't know what he did.

JOHN: The single event of autopilot auto throttle disengagement

sends the investigators in two different directions --

one, what caused it? Two, how did the crew handle it?

As investigators struggle to answer puzzling questions

about Flight 8501 and its crew...

RAY: Hello? NTSC.

NARRATOR: They get an important new lead.

RAY: Wait, wait. Slow down. What happened?

♪

NARRATOR: A mysterious action by the captain

to solve a routine error appears to have set off

a deadly sequence of events.

Investigators are still trying to understand what happened

when they receive some new information.

RAY: Start from the beginning. Where was he?

EMMANUEL: Three days before the accident, on the 25th December,

this same captain was about to fly

from Indonesia to Kuala Lumpur when he had an RTLU malfunction.

He asked for an engineer to come to the cockpit

and try to fix that.

ENGINEER: RTLU problem again?

CPT. IRIYANTO: Yeah, it just keeps coming back.

NARRATOR: The maintenance engineer rebooted the system.

But the problem came back.

ENGINEER: I've got an idea.

NARRATOR: He then pulled the circuit breakers

for the main computer.

JOHN: Maintenance on the ground has a very specific list

of circuit breakers that says you can utilize

pulling these circuit breakers to reset computers

within the airplane.

NARRATOR: As the captain watched, the problem was fixed.

ENGINEER: Problem solved.

CPT. IRIYANTO: And can I do the same thing if it happens again?

ENGINEER: Yeah, just do what the ECAM tells you to do.

RAY: Don't tell me he tried to do that in the air.

NARRATOR: Investigators think that they now know

what the captain did that led to the crisis in the cockpit.

RAY: Begin simulation.

NARRATOR: To see if they're right, they decide to simulate

the cockpit warnings heard in-flight.

RAY: Okay, so let's start with the RTLU warnings.

AUTOMATION:

RAY: FAC 1 off. FAC 2 off.

Good.

AUTOMATION: CPT. IRIYANTO: Enough of this.

NARRATOR: After the fourth RTLU warning, he takes a new approach.

FO. PLESEL: ECAM actions?

CPT. IRIYANTO: No. I've got a better idea.

NARRATOR: Investigators believe the captain

pulled two critical circuit breakers.

RAY: Captain pulls circuit breaker one.

♪

NARRATOR: The result is immediate.

AUTOMATION:

RAY: And there goes the autopilot disconnect warning.

NARRATOR: Investigators can now be certain of one thing.

RAY: This had to be what he did.

JOHN: He was perhaps copying

what he'd seen the ground engineer do,

but of course the consequences in flight

to disabling critical systems are quite different.

JOHN: The captain wrongly assumed

that if it worked on the ground it'll work in flight.

ERTATA : The circuit breaker,

which is part of the flight augmentation computer,

is something that should never be pulled out in the air.

NARRATOR: Pulling the circuit breakers

has devastating consequences the captain didn't anticipate.

JOHN: Unfortunately, he was not pulling circuit breakers

that affected only the rudder limiter system,

but ones that also disabled the flight augmentation computer,

which tripped the autopilot, the auto throttle and

all the normal mode protections that the aircraft had.

NARRATOR: The plane begins to roll.

Over the next nine seconds, it rolls fifty-four degrees,

yet no one does anything to stop it.

What took them so long to react?

RAY: The first officer would have been looking here and here

when the autopilot warning was disconnected,

and the captain was still standing behind

the first officer's seat.

FO. PLESEL: What was that?

NARRATOR: It's likely that neither pilot

was looking at the attitude indicator

that showed the plane was banking.

RAY: That's why it took them nine seconds

to notice what this gauge here was telling them.

NARRATOR: As the plane started to roll,

the first officer was focused on the fault warnings.

He didn't notice that the plane was banking

until the captain sat back down again.

CPT. IRIYANTO: Oh my God. FO. PLESEL: Oh!

NARRATOR: Despite losing control of these systems,

the high-tech plane did have the capacity

to get back on course.

After the initial roll, why didn't the first officer

just steady the plane and reengage the autopilot?

Investigators have to try to understand

what was going on inside the pilots' heads.

JOHN: The co-pilot's movement of the stick

to its extreme rightmost position

resulted in a very violent roll to the right,

two to three times what would be programmed as the maximum

for an Airbus normally.

NARRATOR: In an attempt to understand

the first officer's actions, investigators study

how the human brain behaves in flight.

A sense of balance is maintained by liquid levels

in the ear canals. When that shifts violently,

the brain can get mixed signals that affect balance.

The FDR data shows how dramatic the plane's movements were.

RAY: So the plane rolled fifty-four degrees left,

and he pulled back almost level in just two seconds.

That would scramble anybody's gyros.

Maybe that was the confusion?

JOHN: As soon as the first officer had leveled the aircraft,

the fluid in his ear canals keeps spinning to the right.

The aircraft is level,

but there's a very strong illusion from the ears

that you're turning to the right.

RAY: He pushes the plane all the way to the left. But why?

CPT. IRIYANTO: Level. FO. PLESEL: I am! I am!

JOHN: The natural response would be to roll the aircraft

back to where it came from into the fifty-four degree of bank,

which was what they thought the level was.

RAY: And then he pulls it as hard as he can,

and the plane starts climbing.

JOHN: This is a massive input.

The airplane would pitch up very quickly.

FO. PLESEL: What's going on?

RAY: He was completely baffled.

JOHN: His vertigo may have led him to believe

that the aircraft was pitching down.

So he's actually recovering from an imaginary pitch down.

RAY: He was disoriented.

JOHN: With all the alarms that were going off,

with the rapid left-right-left rolls

and with the generally deteriorating situation,

I think the crew had started to lose their spatial awareness

completely.

NARRATOR: Investigators finally understand

what must have been going on with the first officer's

confused state of mind.

But if the first officer

wasn't operating the controls correctly,

why didn't the captain take the one step

that could have saved the lives of everyone on board?

♪

Investigators study the captain's behavior

during the roll. CPT. IRIYANTO: Pull down!

NARRATOR: They know from the recordings that

he was trying to help right the plane.

CPT. IRIYANTO: Pull down.

FO. PLESEL: I'm trying. It's not responding.

NARRATOR: He wants his first officer to stop climbing up

and push the nose down.

CPT. IRIYANTO: Pull down!

NARRATOR: But his command is confusing.

RAY: It's either you pull up or you push down.

JOHN: When one thinks that the co-pilot

is holding a side stick, pull means pull it back,

which means go up. And down means push it forward.

So pull down is a contradictory command.

EMMANUEL: In that case the captain should have said:

"Nose down. Nose down."

NARRATOR: The first officer continues pulling back

on his side stick until the very end.

JOHN: The input of the first officer...

CPT. IRIYANTO: Pull down!

JOHN: Was the exact wrong thing to do.

FO. PLESEL: What's going on?

NARRATOR: He clearly didn't understand the command.

So why didn't the captain take full control of the airplane?

RAY: He tried to take over here and over here.

CPT. IRIYANTO: Pull! FO. PLESEL: It's not correcting.

JOHN: There is a button on top of the side stick

that can let you take full control

to lock the other pilot out...

CPT. IRIYANTO: Pull!

JOHN: ... so that you know what's going on.

NARRATOR: The data shows that the captain

did push the take control button, but only briefly.

He didn't push it long enough to take over the plane.

FO. PLESEL: It's not responding.

RAY: But at the end, he never took control.

NARRATOR: It meant that both pilots were trying to fly

at the same time.

RAY: Both pilots started controlling the aircraft.

When that happened, control of the aircraft become ineffective.

NARRATOR: If he'd spoken three simple words,

the plane could have been saved.

JOHN: The training is, you say, "I have control,"

and the other pilot stops making inputs.

In this case, that wasn't happening.

♪

NARRATOR: Investigators now know that pilot error

led to a spatially disoriented first officer.

The captain, who could have helped

by communicating more clearly or taking over the plane,

did neither.

Investigators can never be certain why.

The case is building to a close when they get another piece

of information. The results of the RTLU analysis are in.

♪

It was a series of warnings from that unit

that triggered the events that led to the crash.

FO. PLESEL: ECAM actions?

JOHN: The failure the crew had experienced

with the rudder limiter system

was actually a negligible failure. It was a nuisance.

And the procedures to reset it...

CPT. IRIYANTO: FAC 1 off and on.

JOHN: ...were simple.

CPT. IRIYANTO: FAC 2 off and on.

Warning cleared.

NARRATOR: All the captain had to do

was keep on following the ECAM's instructions.

EMMANUEL: The plane had had a history of RTLU failures

throughout the year, and this failure had never been fixed.

NARRATOR: Microscopic examination of the unit's

electronic module finally reveals

the cause of those repetitive failures.

EMMANUEL: We found out that there was a crack

in the soldering joint on the electronic module,

which caused the RTLU to work from time to time only.

And had the correct maintenance task been applied...

ENGINEER: Problem solved.

EMMANUEL: ...the RTLU electronic module

would have been removed.

JOHN: The airplane should have been sent for troubleshooting,

and you could have broken the chain of events.

NARRATOR: For investigators, discovering

that such a minute fault sparked events

that led to the death of all 162 people on board

makes this all the more tragic.

As they prepare their final report,

it's clear that the crash of Flight 8501

has exposed a series of serious problems.

♪

The final report calls for improved maintenance protocols

to help eliminate minor recurring problems,

like the RTLU fault,

before they lead to a major catastrophe.

JOHN: When you start having four, five, six, eight,

ten recurring problems, it's saying

that the traditional methods are not working

and that you need to do much more heavy-duty diagnostics

until they find the problem.

CPT. IRIYANTO: Pull! Pull down.

RAY: And the other lesson we take from the accident

was the communication between pilots

to make sure that communication was well

to avoid the different interpretation of the command.

JOHN: This is a case that the industry learned

some very hard lessons, but the thing most importantly

is that the industry implements those lessons

so that we don't have another one.