Original subtitles

A Boeing 737 vanishes from radar above one of

A Boeing 737 vanishes from radar above one of

the most remote areas on Earth.

It's the worst accident

in the history of Panama.

A jumbo jet slams into the English countryside.

A jumbo jet slams into the English countryside.

It was like a battlefield.

A late night flight in Russia...

A late night flight in Russia...

...ends in a harrowing crash.

It's the sole control of the aircraft.

It's the sole control of the aircraft.

And without it, it would be very, very

difficult to fly the airplane.

When critical instruments cause confusion...

When critical instruments cause confusion...

Bank's not working.

...the consequences can be deadly.

Lock.

Lock.

Bank.

Suddenly, you find that the aircraft is performing

in ways that you didn't expect and the airplane

in ways that you didn't expect and the airplane

is out of control.

Ladies and gentlemen,

we are starting our approach.

we are starting our approach.

We lost both engines.

Max capacity load.

Emergency dispatch.

Mayday, mayday.

Brace for impact.

Brace for impact.

Do the last one.

After the engine has started.

It's gonna crash.

It's gonna crash.

Tocumen International Airport in Panama City.

Copa Airlines Flight 201 prepares for a one hour

Copa Airlines Flight 201 prepares for a one hour

flight South to Cali, Colombia.

V1.

Rotate.

Gear up.

Copa's most senior pilot, Captain Rafael Chial,

is monitoring the instruments.

is monitoring the instruments.

Set thrust to climb.

First officer Cesareo Tejada is at the controls.

First officer Cesareo Tejada is at the controls.

40 passengers are on board, mostly business travelers

40 passengers are on board, mostly business travelers

heading home to Colombia.

We've got some heavy weather moving in from the Gulf.

We've got some heavy weather moving in from the Gulf.

Tonight, the pilots won't be able to fly

their planned route.

Panama center, Copa 201.

We'd like to get around this weather.

We'd like to get around this weather.

Requesting a new heading for 0-9-0.

Copa 201, copy that.

Copa 201, copy that.

You're cleared on a heading, zero-niner-zero.

Cleared.

Cleared.

Heading 090.

Heading 090.

The new flight path takes

the 737 east around the storm before heading

the 737 east around the storm before heading

south again to Cali.

Panama center, Copa 201.

Panama center, Copa 201.

Level at 250.

The plane reaches cruising altitude.

The plane reaches cruising altitude.

Minutes later, Copa 201 disappears from radar.

Minutes later, Copa 201 disappears from radar.

If you're close to thunderstorms

and in a lot of rain, there'll be static on the radio.

and in a lot of rain, there'll be static on the radio.

And sometimes you may not be able to talk

to them for a few minutes.

to them for a few minutes.

But air traffic control never

hears again from Copa 201.

hears again from Copa 201.

The next day, search teams

begin the task of locating the plane and any survivors.

begin the task of locating the plane and any survivors.

A mass of wreckage is found in the remote Darien Gap.

A mass of wreckage is found in the remote Darien Gap.

Panama's deputy director of civil aviation,

Panama's deputy director of civil aviation,

Jorge Rodriguez, is under enormous pressure

to figure out what happened.

At that time, it was the first big accident

At that time, it was the first big accident

of an air carrier of Panama.

of an air carrier of Panama.

We lost 47 people on board.

All dead.

Investigators begin collecting

and cataloging the wreckage.

and cataloging the wreckage.

It spread across an area exceeding 100 square miles.

Tom Haueter, NTSB.

How are you doing?

How are you doing?

The United States National

Transportation Safety Board is invited

to join the investigation.

to join the investigation.

There's a lot of pressure at the NTSB

and all investigation to determine

the cause of the accident.

That's what we do.

That's what we do.

So certainly we want to know what happened, why,

and we want to prevent another accident.

That's our main mission.

That's our main mission.

After a grueling hunt, the search

team recovers the black boxes.

team recovers the black boxes.

We were hoping it was the cockpit voice recorder.

We'd get more information in terms of what

We'd get more information in terms of what

the crew was saying what was happening

right at the time of impact.

But then, the technicians opened

But then, the technicians opened

the cockpit voice recorder.

My God.

What a mess.

You just had a ball of Mylar tape.

You just had a ball of Mylar tape.

Fortunately, the flight data

recorder is in good condition.

recorder is in good condition.

The data we had, the takeoff,

the climb out, you know, the cruise, everything

looked like a normal flight.

looked like a normal flight.

Investigators know that Copa

201 diverted to avoid a storm.

201 diverted to avoid a storm.

Did the pilots make an error at that moment?

We could go back and look at the weather data

and the long range radar data.

and the long range radar data.

Flying in weather at night, thunderstorms

Flying in weather at night, thunderstorms

can be totally disorienting.

When the investigators examine the plane's track

they determine the plane did fly out of the storm's path.

they determine the plane did fly out of the storm's path.

I say that the weather wasn't an issue in that accident.

I say that the weather wasn't an issue in that accident.

If not the weather, then what

brought down Copa 201?

brought down Copa 201?

Everything was normal.

That was abrupt.

Investigators used the last two minutes of flight data

to create an animation of the plane's final moments.

to create an animation of the plane's final moments.

It should be correcting.

It's not correcting.

Whoa.

What the heck's going on?

What the heck's going on?

We would start seeing the aircraft roll

over into a bank angle then suddenly snap back to level,

over into a bank angle then suddenly snap back to level,

or vise versa.

They need to find an explanation for the plane's

erratic maneuvers.

The team searches the cockpit controls for clues.

The team searches the cockpit controls for clues.

One switches setting raises a red flag.

One switches setting raises a red flag.

The vertical gyro switch affects the most

important flight instrument in the cockpit,

important flight instrument in the cockpit,

the attitude indicator.

V1.

Rotate.

Each pilot has their own attitude indicator.

Each pilot has their own attitude indicator.

It registers how the plane is positioned

relative to the horizon.

relative to the horizon.

The pilot's attitude indicator is like a ball.

It shows bank angle.

It shows pitch.

It shows pitch.

Each attitude indicator is connected

to a vertical gyro, or VG.

to a vertical gyro, or VG.

The gyros constantly calculate the plane's attitude.

Looks like they were having trouble

with the first officer's gyro.

with the first officer's gyro.

On this flight, the first officer's

attitude indicator was switched over

to VG-1, the captain's gyro.

to VG-1, the captain's gyro.

Both of them were reading

data from the same gyro source.

Which makes you think that at some point either

Which makes you think that at some point either

it was selected that way, or they didn't realize it had been

selected that way, but they're both feeding

selected that way, but they're both feeding

data from the same source, which is unusual.

A pilot only switches to the other gyro

A pilot only switches to the other gyro

if there's a problem with their own.

If one gyro goes bad, you don't want to have

the pilot looking at bad data.

the pilot looking at bad data.

So you switch them both over to the good data.

Copa 201 was also equipped with a third gyro

Copa 201 was also equipped with a third gyro

and attitude indicator, independent of the captains

and first officers.

and first officers.

Pilots should use the third gyro to clarify which

ADI is operating correctly.

ADI is operating correctly.

What caused the pilots to switch over and share the captain's

gyro on flight 201?

gyro on flight 201?

OK, fire it up.

What we wanted to look at was,

is there anything here that would show us what happened?

is there anything here that would show us what happened?

Is there a failure in the gyros?

Or maybe the failure is actually the attitude indicator.

Well, this one seems to work fine.

Nothing is wrong with the first officer's instrument.

Nothing is wrong with the first officer's instrument.

Let me see the other one.

At first, the captain's instrument

seems fine too.

Hang on.

It seems to be stuck.

It seems to be stuck.

Every few seconds the captain's attitude

indicator freezes, even though the gyro

indicator freezes, even though the gyro

is still feeding it data.

Yeah, there it goes.

Yeah, there it goes.

Now it's working.

What's causing the intermittent failure?

They test every wire connecting the display to the gyro.

Oh.

Oh.

No wonder.

This wire is hanging by a thread.

We found basically a break in the wire.

Intermittent.

Intermittent.

It was close enough that sometimes it would touch

and sometimes it wouldn't.

The faulty connection is a major breakthrough

The faulty connection is a major breakthrough

in the investigation.

But it also poses a challenge.

The way the airplane is wired

is what the captain is seeing on his attitude indicator

is what the captain is seeing on his attitude indicator

is what's being recorded on the flight data recorder.

is what's being recorded on the flight data recorder.

The same faulty data being

fed to the captain's attitude indicator

was being sent to the flight recorder.

was being sent to the flight recorder.

OK, let's see what the plane was really doing.

But by carefully analyzing other parameters

But by carefully analyzing other parameters

in the flight data recorder they managed

to calculate its actual movements

to calculate its actual movements

and reveal the planes true motion.

Making it a visual of it

where you could see what the data is showing

where you could see what the data is showing

and what the airplane is doing.

That visual is extraordinarily helpful.

That visual is extraordinarily helpful.

The red image reflects the bad data

the pilots were seeing.

While the solid image shows how Copa 201 was actually flying.

While the solid image shows how Copa 201 was actually flying.

They're trying to level the plane,

but they're making it worse.

but they're making it worse.

You have the attitude indicator here stuck,

but the airplane's going the other direction.

but the airplane's going the other direction.

And then suddenly the attitude indicator

gets powered to it, unsticks, it goes back

gets powered to it, unsticks, it goes back

and mimics the airplane again.

Go right.

You need to go right.

I am.

What's it doing?

What's it doing?

He doesn't realize that all he's doing

He doesn't realize that all he's doing

is making the problem worse.

He's looking at an instrument providing bad data,

and he lost control of the aircraft.

and he lost control of the aircraft.

If this had been a daytime flight

the pilots would have had the horizon to guide them.

the pilots would have had the horizon to guide them.

But flying at night, they had to rely

solely on their instruments.

solely on their instruments.

The FDR data reveals that the plane rolls so far to the right

that recovery is impossible.

that recovery is impossible.

Once it got to this point, they didn't have a chance.

But investigators are puzzled.

It was the captain's gyro that failed in flight

It was the captain's gyro that failed in flight

and started sending bad data.

So why was it selected?

So the question is, why they believed the captain's

So the question is, why they believed the captain's

gyro was the good one?

Why was it switched to that position?

Why was it switched to that position?

On Copa 201, the captain's attitude indicator

On Copa 201, the captain's attitude indicator

malfunctioned.

So why was the crew relying on it

instead of the first officers, which

instead of the first officers, which

was functioning perfectly?

Trying to understand the flight crew's confusion...

Trying to understand the flight crew's confusion...

OK, let's start.

...investigators work with the same type

of flight simulator used by the crew for their 737 training.

of flight simulator used by the crew for their 737 training.

Climb to 25,000 and turn right.

They recreate the flight of Copa 201.

They recreate the flight of Copa 201.

Now, trigger the failure.

Including the malfunction of the captain's

Including the malfunction of the captain's

attitude indicator.

Now, how'd you make the switch?

Wait a minute.

Let me see that.

That is not the same switch that was on Copa 201.

That is not the same switch that was on Copa 201.

Two different configurations

Two different configurations

of one small control switch has overwhelming implications.

This is the gyro switch from the simulator

This is the gyro switch from the simulator

where the captain was trained.

Next slide, please.

Next slide, please.

And this is the gyro switch from Copa 201.

And this is the gyro switch from Copa 201.

Now, can we get a close up, please.

All right.

Now, let's see both.

Now, let's see both.

Wow.

That's completely different.

The cockpits, the simulator were dissimilar.

The cockpits, the simulator were dissimilar.

And so it was possible to get confused,

thinking you were going to independent

gyro source when you weren't.

gyro source when you weren't.

In the simulator, flipping the toggle to the left

switches the captain's instrument

to the third gyro, which is independent of the other two.

to the third gyro, which is independent of the other two.

But on flight 201, flipping the switch to the left

But on flight 201, flipping the switch to the left

put both instruments on the captain's system,

which was malfunctioning.

Panama center, Copa 201.

Panama center, Copa 201.

Investigators finally have a theory of how the flight

Investigators finally have a theory of how the flight

went so horribly wrong.

It looks like we're going to have

to take the long way around.

Mhm.

After diverting around the storm,

the crew of Copa flight 201 needs to turn

right to get back on course.

right to get back on course.

Turning right.

Heading 160.

Heading 160.

Well clear of the storm now.

Mhm.

Mhm.

As the plane levels out,

an error flag warns of a problem with the captain's attitude

an error flag warns of a problem with the captain's attitude

indicator.

They flip the gyro switch to the left,

thinking they're now using a backup gyro.

thinking they're now using a backup gyro.

Now they're both on the bad gyro and neither of them

Now they're both on the bad gyro and neither of them

knows about it.

That's weird.

Why won't it level?

In the middle of the night,

you don't have the horizon.

You lose the horizon, you don't know where you are.

First officer Tejada turns

First officer Tejada turns

his wheel to level the wings.

His frozen instrument makes it appear

the plane isn't responding.

So he continues to turn, sending the plane further and further

So he continues to turn, sending the plane further and further

to the left.

He's trying to correct a problem

He's trying to correct a problem

he's seen on his instrument.

He's taught, follow your instruments,

believe in the instruments.

He's actually making the problem a lot worse.

He's actually making the problem a lot worse.

Go right.

You need to go right.

I am.

I am.

What's it doing?

Now he sees a left bank.

So he's trying to correct it by banking right.

So he's trying to correct it by banking right.

Altitude.

What in God's name?

Pull up.

Pull up.

By the time the pilots realized they're in a dive...

Hang on!

Hang on!

Left, left, left.

I'm trying, captain.

...it's too late.

It would be extraordinarily disconcerting.

It would be extraordinarily disconcerting.

You've gone from a few degrees to the left to multiple degrees

to the right.

It was like, what's happening here?

It was like, what's happening here?

Confused by their instruments,

Confused by their instruments,

the pilots lose control.

In the accident's aftermath, Copa revamps pilot training

to ensure that crews are better prepared

to ensure that crews are better prepared

for an instrument malfunction.

One of the improvements we've made as an industry

One of the improvements we've made as an industry

is better pilot training, and also the improvement

in the flight instruments.

So that they're no longer mechanical.

So that they're no longer mechanical.

They're typically ring laser gyro.

They're more electronic.

So that you don't have the failures that you used to.

So that you don't have the failures that you used to.

40 miles Northeast of London, Stansted Airport

40 miles Northeast of London, Stansted Airport

is a major European hub.

Korean Air flight 8509 is preparing

Korean Air flight 8509 is preparing

to take off to Milan, Italy.

The aircraft was a Boeing 747 freighter.

The aircraft was a Boeing 747 freighter.

As the name suggests, it was not configured

with passenger seats, but the interior

with passenger seats, but the interior

was full up with freight.

Captain Park Duk-kyu is

a highly respected commander.

a highly respected commander.

Sir.

He's a former Colonel in the Korean

Air Force with thousands of hours

of flying time on the 747.

of flying time on the 747.

Park Hoon-kyu is flight 8509 flight's engineer,

Park Hoon-kyu is flight 8509 flight's engineer,

responsible for monitoring the aircraft's mechanical systems.

First officer Yoon Ki-sik has only 195

hours flying time on the 747.

hours flying time on the 747.

On this night, there were the three

crew and a Korean engineer.

crew and a Korean engineer.

The engineer has overseen some minor maintenance

work on the aircraft and will now accompany

work on the aircraft and will now accompany

flight 8509 back to Seoul.

flight 8509 back to Seoul.

All right, gentlemen.

Let's proceed.

80 knots.

Roger.

V1.

Rotate.

The plane lifts off from Stansted

Airport at 6:36 PM.

Positive rate confirmed.

Gear up.

Gear up.

Gear up.

At 2500 feet, the aircraft

needs to make a left turn.

Left turn at 1.5 DME.

Left turn at 1.5 DME.

But the captain's attitude indicator

But the captain's attitude indicator

registers that the plane isn't responding.

Bank.

Bank.

Bank.

The flight engineer recognizes

the plane is banking.

Lock.

Back.

Back.

In less than 60 seconds,

In less than 60 seconds,

for some unexplained reason, Korean Air flight 8509 has gone

from takeoff to catastrophe.

from takeoff to catastrophe.

Korean Air flight 8509 lies in pieces

just a few miles from one of the world's busiest airports.

just a few miles from one of the world's busiest airports.

The UK's Air Accidents Investigation branch

deploys a team to the site.

deploys a team to the site.

It was a very confusing debris field.

It takes a while for one to absorb the scene

It takes a while for one to absorb the scene

and to try and make sense of it all.

By daylight, they get their first good look

at the point of impact.

A massive crater surrounded on all sides by debris.

A massive crater surrounded on all sides by debris.

Investigators get a glimpse into the flight's final seconds

from a portion of the ground scar.

It was a long slender gash,

It was a long slender gash,

which was made by the wing.

And then you could see where the nose had impacted further on.

And then you could see where the nose had impacted further on.

This suggests the plane

hit the ground on its side.

hit the ground on its side.

But not according to the captain's

attitude direction indicator.

It shows the plane was flying level at the time of impact.

It shows the plane was flying level at the time of impact.

Did the ADI malfunction?

Did the ADI malfunction?

Seeking answers, investigators interview the crew

Seeking answers, investigators interview the crew

that flew the previous leg of the flight

from Uzbekistan to Stansted.

I need you to walk me through exactly what happened.

They told us that when they departed

from Tashkent the day before in good weather

from Tashkent the day before in good weather

in daylight conditions they had to carry

out a turn to the left.

out a turn to the left.

As the captain commenced the turn,

his artificial horizon did not work in role.

his artificial horizon did not work in role.

By daylight, the pilot was able to get

By daylight, the pilot was able to get

his bearings from the horizon.

After landing, the inbound crew left the terminal before

After landing, the inbound crew left the terminal before

the replacement crew arrived.

The only person who heard about the problem

with the attitude indicator was the Korean Air

with the attitude indicator was the Korean Air

maintenance engineer.

He then enlisted a local mechanic to help.

He then enlisted a local mechanic to help.

I need you to remove the captain's ADI.

The locally based engineer told us

he removed the instrument from the panel,

he removed the instrument from the panel,

unplugged the wires at the back.

unplugged the wires at the back.

All right.

That's our problem.

Can you reset the pin?

And found what he believed to be

And found what he believed to be

a problem with the connector pins

at the back of the instrument.

at the back of the instrument.

Looks good.

The engineer assumes the attitude

The engineer assumes the attitude

indicator was repaired.

But when investigators examined data from the flight recorders,

But when investigators examined data from the flight recorders,

something doesn't add up.

The readout is showing that the plane's roll angle

never exceeded two degrees.

never exceeded two degrees.

That's insufficient to cause the plane to go out of control.

That's insufficient to cause the plane to go out of control.

Clearly, it had gone in at a much steeper roll angle

than that, like 90 degrees.

than that, like 90 degrees.

So that set the alarm bells ringing.

Why should that occur?

Why should that occur?

It turns out the problem

with the attitude indicator was not properly diagnosed.

When investigators dig deeper into the navigation system,

When investigators dig deeper into the navigation system,

they discover that one of the plane's gyros

had short circuited.

had short circuited.

This was the gyro feeding the captain's attitude indicator.

It simply ended up corrupting the the role

It simply ended up corrupting the the role

information that was fed to both the flight data

recorder and the captain's ADI.

The rectification action

was completely ineffective.

was completely ineffective.

The aircraft took off with the same defect

that it had arrived with.

that it had arrived with.

The pilots on Korean Air faced the same problem

that took down Copa 201.

Go right. You need to go right.

I am.

I am.

One malfunctioning ADI.

In this case, the flight data shows

that both the first officer's attitude indicator

and the backup instrument displayed

and the backup instrument displayed

the plane's true bank angle.

Only the captain's indicator was malfunctioning.

Only the captain's indicator was malfunctioning.

An instrument

failure is a rare occurrence.

However, crews are trained to deal with it.

However, crews are trained to deal with it.

Why didn't the crew alert the captain

that his instrument was faulty and that they were potentially

that his instrument was faulty and that they were potentially

heading for disaster?

Were they all confused by their instruments?

Were they all confused by their instruments?

AAIB technicians salvaged the recording

from flight 8509's badly damaged cockpit voice recorder.

from flight 8509's badly damaged cockpit voice recorder.

One of the most important things

that was on that recorder was the sound of a warning

that was on that recorder was the sound of a warning

horn going off in the cockpit as the aircraft departed

from Stansted.

But even more significant

than the sound of the alarm is the absence

of any reaction to it.

of any reaction to it.

They seem to be ignoring the alarms completely.

The co-pilot should have said to the captain,

The co-pilot should have said to the captain,

your ADI is not reading correctly.

It was obvious from this accident

It was obvious from this accident

that the crew interaction played a big part in this accident.

that the crew interaction played a big part in this accident.

A lot of the captains in Korean Air

were people that had developed their skills in the military.

were people that had developed their skills in the military.

Captain park was a Colonel

and fighter pilot with a distinguished military career.

and fighter pilot with a distinguished military career.

There was definitely

There was definitely

a hierarchy between pilots.

When the younger, less experienced first officer

When the younger, less experienced first officer

noticed the discrepancy in the ADIS,

he didn't dare correct his captain's actions.

he didn't dare correct his captain's actions.

This crew were not operating as a crew.

They were operating as one man with a couple of assistants.

They were operating as one man with a couple of assistants.

Bank.

Bank.

Bank.

The captain wrongly believed

what his malfunctioning ADI was telling him.

what his malfunctioning ADI was telling him.

Lock.

Bank.

The aircraft just continued

to roll for 30 degrees, 40, 50, 60, 70, 80, 90 degrees of bank.

to roll for 30 degrees, 40, 50, 60, 70, 80, 90 degrees of bank.

The AAIB recommends changes

to Korean Air pilot training.

In response, the airline overhauls its training

programs, recommending that crews

programs, recommending that crews

work together more closely.

When problems happen with the attitude

indication systems, the actions pilots

indication systems, the actions pilots

take can eventually put the aircraft into a position

where it can't recover.

But it's not something that's immediate.

That is, if the crew takes the time to diagnose or recognize

That is, if the crew takes the time to diagnose or recognize

the problem and take the appropriate action,

there's usually plenty of time to correct this

there's usually plenty of time to correct this

and continue flying safely.

Aeroflot-Nord flight 821

Aeroflot-Nord flight 821

is moments from touching down in Perm, a city in Central Russia.

is moments from touching down in Perm, a city in Central Russia.

There are 82 passengers on board the Boeing 737.

There are 82 passengers on board the Boeing 737.

43-year-old first officer Rustam Alaberdin

is the pilot flying tonight.

The captain, Rodion Medvedev, 34,

The captain, Rodion Medvedev, 34,

is monitoring the instruments in radio communications.

They are making the two hour journey from Moscow to Perm

and will then return to the Russian capital.

and will then return to the Russian capital.

821, descend to 2000 feet.

821, descend to 2000 feet.

Surface wind 050 degrees out, 10 knots.

Tail wind is nine knots.

Tail wind is nine knots.

Increase your speed.

Right.

Of course.

891er, 821 confirming base turn

891er, 821 confirming base turn

and descending to 2000 feet.

The crew prepares for landing.

The crew prepares for landing.

Flips 30.

Sit.

Sit.

But in the tower, the controller

But in the tower, the controller

sees that flight 821 is climbing instead of descending.

Aeroflot 821, according to my data, you are climbing.

Aeroflot 821, according to my data, you are climbing.

Can you confirm?

Damn it.

To resume the descent, the first officer

To resume the descent, the first officer

adjusts the pitch of the plane.

We can confirm.

We can confirm.

And we're descending now.

But now, the controller

sees flight 821 flying past the approach path to the runway.

sees flight 821 flying past the approach path to the runway.

He instructs the crew to loop around and try again.

Aeroflot-Nord 821, restart your final approach.

Aeroflot-Nord 821, restart your final approach.

Turn right heading 360.

Descend to 2000 feet.

Descend to 2000 feet.

But this instruction is ignored.

821, descend to 2000 feet.

821, descend to 2000 feet.

Turn right, heading 360.

Follow my instructions strictly.

Follow my instructions strictly.

What the flight controller doesn't know

What the flight controller doesn't know

is that the pilots have lost control of the plane.

Wrong way.

Other direction.

Other direction.

Bank angle.

Bank angle.

Bank angle.

Flight 821 has crashed on the outskirts of Perm.

Everyone on board has died.

Everyone on board has died.

How did this landing turn into a fatal disaster?

How did this landing turn into a fatal disaster?

Aeroflot-NORD flight 821 has crashed on the outskirts

Aeroflot-NORD flight 821 has crashed on the outskirts

of Perm, Russia.

All 88 people on board are dead.

Be careful with this.

Bring it over here.

Russian investigators from the Interstate Aviation

Russian investigators from the Interstate Aviation

Committee, the IAC, are called in to find the cause

of this tragic accident.

of this tragic accident.

Their American counterparts from the National Transportation

Safety Board join the team.

Safety Board join the team.

Thank you for making trip from Washington.

I hope we can help.

I hope we can help.

We were invited because the Boeing was manufactured

in the United States.

in the United States.

What about the flight recorders?

They are in rough shape.

They are in rough shape.

The cockpit voice recorder and the flight data

recorder are badly damaged.

They are sent to a facility in France that specializes

They are sent to a facility in France that specializes

in retrieving data, but it could take weeks for the results

to return.

to return.

In the meantime, investigators need to find out

if all of the 737 flights systems

if all of the 737 flights systems

were in working order after taking off from Moscow.

Maintenance records reveal that a month before the crash

Maintenance records reveal that a month before the crash

the right engine started producing

20% more thrust than the left.

20% more thrust than the left.

That's enough to throw the engine balance way off.

A Boeing 737's engines are

A Boeing 737's engines are

spaced apart beneath the wings.

When the thrust is uneven, the stronger side

pushes the wing up, causing the airplane to roll.

pushes the wing up, causing the airplane to roll.

Pilots need to compensate for this uneven thrust.

Pilots need to compensate for this uneven thrust.

The only way it can counteract an asymmetric thrust

The only way it can counteract an asymmetric thrust

is to provide bank, a small amount of bank,

is to provide bank, a small amount of bank,

in the opposite direction to try and maintain

the aircraft's track.

The imbalance was so extreme

that the 737's previous pilots photographed the thrust

that the 737's previous pilots photographed the thrust

levers to show the degree of stagger

required to level the plane.

It's a crucial lead.

It's a crucial lead.

A split an engine balance makes it more difficult to fly,

but it shouldn't cause a crash.

But did these pilots know about the mismatch?

But did these pilots know about the mismatch?

Take a look.

The crash day.

The crash day.

And it's signed by our captain.

The pilots did know about the need

for staggered throttles.

for staggered throttles.

But were they able to fly the plane like this?

The airline insists both pilots were very experienced.

The airline insists both pilots were very experienced.

Captain had over 3,900 flying hours, 1,400 of these at night.

Captain had over 3,900 flying hours, 1,400 of these at night.

Wait.

2/3 of his hours were in the cockpit of the Tupolev 134.

2/3 of his hours were in the cockpit of the Tupolev 134.

The Tu 134?

The Tu 134?

Built in Russia, the Tupolev 134

was one of the most widely used Jets in the former Soviet bloc.

was one of the most widely used Jets in the former Soviet bloc.

Unlike the 737, its engines are positioned side by side

Unlike the 737, its engines are positioned side by side

at the rear of the plane and require minimal adjustment

if they're mismatched.

if they're mismatched.

Flying the 737,

it's very different from flying the Tupolev.

With this discovery, investigators

With this discovery, investigators

now consider how qualified the pilots were to fly the 737.

now consider how qualified the pilots were to fly the 737.

They delve into the captain's training records.

The captain's English language skills

were limited, which begs the question,

were limited, which begs the question,

how much training did he understand?

All the technical manuals

were written in English.

were written in English.

And all their operating procedures

were written in English.

Medvedev got his training certification for the 737

on September 10, 2006.

But then went back to flying the Tupolev.

He didn't get into the 737 again until January 9, 2007.

He didn't get into the 737 again until January 9, 2007.

He had a four month break away from his knowledge,

He had a four month break away from his knowledge,

and he had to have been forgetting

things left and right.

things left and right.

Hardly a proficient 737 pilot.

Hardly a proficient 737 pilot.

Hardly.

The first officer's record is carefully examined.

The first officer's record is carefully examined.

I am from IAC.

I have a quick question for you.

And in particular, his 737 training.

And in particular, his 737 training.

He had plenty of experience on Antonov 2.

The Antonov 2 is a huge propeller

biplane with a single engine.

But it's a much simpler plane to fly than the Boeing 737.

But it's a much simpler plane to fly than the Boeing 737.

737 simulator proved to be a real challenge for him.

737 simulator proved to be a real challenge for him.

One thing the first officer struggled with

One thing the first officer struggled with

was flying with thrust asymmetry.

Check the speed.

You are banking.

You are banking.

Bank angle.

Bank angle.

You're banking.

Bank angle.

This is the third time.

Bank angle.

Bank angle.

It appears both pilots were ill equipped

It appears both pilots were ill equipped

to fly the 737, especially when facing the challenge

of an uneven thrust.

of an uneven thrust.

Medvedev was simply too green to Captain the 737.

Medvedev was simply too green to Captain the 737.

We can't tell how much of the English training

he even retained.

The first officer had even more failings.

The first officer had even more failings.

It was a mistake to put them together in the cockpit.

The investigators now know

that two inexperienced pilots were paired in the cockpit.

that two inexperienced pilots were paired in the cockpit.

What they still don't know is how they sent flight

821 into a deadly spiral.

821 into a deadly spiral.

Pull up.

Specialists in France have finally extracted the data

Specialists in France have finally extracted the data

from the badly damaged flight recorder of Aeroflot-Nord 821.

from the badly damaged flight recorder of Aeroflot-Nord 821.

OK.

Now we can see what the plane was doing.

Now we can see what the plane was doing.

Let's pull up the parameters.

The first few hours of data

provide few clues as to the cause of the crash.

provide few clues as to the cause of the crash.

It looks like the auto throttle is on.

It's staggering the thrust levers

and matching the engines.

But in the last three minutes of the flight,

But in the last three minutes of the flight,

the situation changes dramatically.

The right engine is operating at nearly 61%,

The right engine is operating at nearly 61%,

but the left is closer to 40%.

but the left is closer to 40%.

The auto throttle, unable to handle such a large disparity

in engine power, disengages.

in engine power, disengages.

The first officer now has to manage

a massive imbalance in thrust, something

a massive imbalance in thrust, something

he couldn't master in training.

It required a lot more flying skill.

It required a lot more flying skill.

You had to compensate for the fact

that the engine power was mismatched,

or you had to very carefully move the throttles in a way

or you had to very carefully move the throttles in a way

that kept the power balanced.

And the crew wasn't very good at doing

And the crew wasn't very good at doing

either one of those things.

What the FDR shows next is more troubling.

What the FDR shows next is more troubling.

As the first officer begins the right turn toward the runway,

he turns the control column right,

he turns the control column right,

pushes it forward, and engages the stabilizer

trim, a sequence of actions that now turns off the autopilot.

trim, a sequence of actions that now turns off the autopilot.

In most instances, an autopilot is somewhat difficult

In most instances, an autopilot is somewhat difficult

to disengage.

But this man managed to do that by accidentally trimming

when he should not have.

when he should not have.

Then, something even more disturbing comes to light.

Take a look at this.

Take a look at this.

No one has an input for 20-25 seconds.

No one has an input for 20-25 seconds.

With the autopilot off,

neither pilot adjusts throttle, pitch, or roll for 25 seconds.

neither pilot adjusts throttle, pitch, or roll for 25 seconds.

There is nothing controlling the plane.

The mismatched engines are allowed

The mismatched engines are allowed

to continue banking the plane dangerously to the left.

OK.

Let's hear now what's going on in that plane.

Let's hear now what's going on in that plane.

Investigators now turn to the cockpit voice recorder.

821, is everything OK with the crew?

821, is everything OK with the crew?

Aeroflot 821 affirmative.

Take it.

Take it.

Take it.

The first officer doesn't know why they're banking.

He wants captain to take over.

He wants captain to take over.

Keep going.

Take it.

Take it.

Take it.

Take what?

I can't do it either.

Despite his resistance,

the captain grabs the controls.

the captain grabs the controls.

But instead of leveling the plane,

he banks further left, putting the plane into the diving role.

he banks further left, putting the plane into the diving role.

Oh.

Wrong way.

Other direction.

Other direction.

Bank angle.

What's going on?

He needs to bank right, but he's banking left instead.

He needs to bank right, but he's banking left instead.

He's confused.

With the flight in crisis,

With the flight in crisis,

it's crucial the captain checks his ADI and understands

what it's telling him.

what it's telling him.

But there is reason to suspect he's confused

and not reading it correctly.

In the Western ADI, the airplane symbol

In the Western ADI, the airplane symbol

remains fixed, aligned with the actual airplane.

So as you bank the aircraft, the horizon

So as you bank the aircraft, the horizon

will tilt to show the same view as you would see

if you looked out the window.

if you looked out the window.

The ADI in older planes

from Soviet bloc countries work just the opposite.

from Soviet bloc countries work just the opposite.

The horizon is fixed and the airplane symbol moves.

It's a huge difference.

It's a huge difference.

Captain was suddenly given control of the aircraft.

I think he looked down and didn't realize the situation

I think he looked down and didn't realize the situation

and started to bank it hard to the left.

and started to bank it hard to the left.

He may have reverted back to interpreting

He may have reverted back to interpreting

the instruments he was used to when he was flying

the Tupolev or the Antonov.

the Tupolev or the Antonov.

The captain didn't know which way he was really banking.

Exactly.

And he made the bad situation worse.

And he made the bad situation worse.

And it turns out there's

something else contributing to the captain's poor performance.

something else contributing to the captain's poor performance.

Right before takeoff

Right before takeoff

a passenger sent the text to a friend.

a passenger sent the text to a friend.

She thought captain was drunk.

Tests on the captain's remains confirm the worst.

Tests on the captain's remains confirm the worst.

He was drunk.

He was drunk.

That could explain why the captain

resisted taking control.

resisted taking control.

Take it.

Take it.

Take what?

I can't do it either.

I can't do it either.

And then misread his ADI.

The commander

had raised levels of alcohol, which impaired

had raised levels of alcohol, which impaired

his judgment and his ability to react accordingly

his judgment and his ability to react accordingly

in a stressful situation.

What's going on?

What's going on?

Aeronot 821, please, come in.

In the final report, the investigative team

recommends a significant overhaul

recommends a significant overhaul

of the Russian aviation system.

The whole system needed

to be looked at and strengthened in terms of the regulations

to be looked at and strengthened in terms of the regulations

and how they train Russian pilots.

When pilots misread their instruments,

routine flights can turn deadly.

routine flights can turn deadly.

The aviation industry has responded with better training

The aviation industry has responded with better training

to prevent confusion in the cockpit.

These are lessons learned, which become part

of future training, lessons learned

of future training, lessons learned

or insights that become catalysts for change

within an organization.

within an organization.

It's something that becomes part of the DNA of aviation.