Original subtitles

Korean Air Flight 6316,

now turn left direct to November, Hotel, Whiskey.

Where is it?

The pilots of Korean Air 6316 struggle to navigate

in the skies above Shanghai, China.

Keep turning left. Keep turning.

Keep turning?

The controller really needs the aircraft

to be going on the expected path.

- But seconds later... - Nose up. Nose up. Nose up.

...the M-D-11-F crashes near a residential neighbourhood.

The impact registered the equivalent

of a 1.6 earthquake.

When investigators reconstruct the flight in a simulator...

Start the dive in three, two, one, go.

...they come to a shocking realization.

The data showed that the upset was caused by a pilot input.

And that becomes the mystery.

It's a mild and overcast spring day

at Hongqiao International Airport in Shanghai, China.

Korean Air Flight 6316 is being prepared for departure.

The cargo plane is loaded with 86 tons of non-hazardous materials.

Checklist beacon light.

Before Start checklist, sir.

The Captain is 54-year-old Hong Sung Sil...

Captain Hong is a very experienced pilot

with 13,000 flight hours and a very good safety record.

...today his First Officer is 35-year-old Park Bon-Suk.

First Officer Park is less experienced than the captain

but also has an excellent safety record.

- Doors and windows? - Closed and locked.

Korean Air is South Korea's flag carrier.

Its headquarters is located at Gimpo International Airport in Seoul.

In 1999 Korean Air is one of the top three passenger airlines in Asia.

And its cargo division is top three in the world.

Its routes covered Asia, South America and Europe.

Hey, guys. Any issues or concerns?

All good so far.

Also on board is 48-year-old Flight Technician Park Byong-Ki.

The flight tech is a mechanic onboard who is not a part of the flight crew.

His job is just to make sure this aircraft

has no mechanic issue and will take off safely.

Engine ignition?

Standby. Fuel panel, auto.

Air panel, auto.

Before start checks complete.

Before the aircraft can begin taxiing to the runway,

it must be pushed into position on the taxiway.

Captain, can you release the parking brake?

Okay, brake released.

All aircraft are parked facing terminal

or the cargo apron, which means the aircraft has no ability to reverse by themselves.

So it's a need to have a tow truck to push them back onto the taxiway.

But as Flight 6316 is being pushed back...

Uh, something's not right.

...the Captain notices something amiss.

Why is that brake temperature light on?

It seems this brake isn't released.

The captain noticed there is a caution

that shows there is a high temperature on one of the brakes.

It doesn't mean this brake is failing.

It just means this brake is hotter than the others.

Yeah, when we landed that brake temp showed up.

In some rare conditions, the hot brake

can lead to fire in flight.

But at this point, the hot brake is not a serious issue.

You just keep an eye on it.

It's dropping down now.

I wonder what's gonna happen when we take off.

Captain, cleared to start engines 3-1-2.

Roger, starting number three.

The pilots are flying a McDonnell Douglas M-D-11-F.

The MD-11 is a large, wide-body aircraft.

This is a very high-performance airplane.

And once you understand the MD-11,

it is a very pleasurable airplane to fly,

but it does require the pilots to be on top of their game.

Hongqiao tower, Korean Air 6316 request taxi.

Korean Air 6316 taxi via kilo-seven tango-zero for runway 1-8.

The aircraft begins taxiing to runway 1-8.

- Right side clear? - Right side clear.

Left side clear.

So many airlines at this airport.

It's 77. It's normal now.

The elevated brake temperature has returned to normal.

Korean Air 6316 clear for takeoff.

Clear for take off 6316. Confirming, we're clear for takeoff.

Check thrust.

Thrust is set. Eighty knots...

V1...

Rotate.

Just after 4pm, they lift off from Shanghai.

Positive climb.

Gear up.

The flight from Shanghai to Seoul is expected to take two hours.

Shortly after takeoff, the controller provides

the pilots with their climb-out instructions.

Korean Air, 6316, now turn left direct to November

Hotel Whiskey, then climb and maintain 1,500 metres.

The M-D-11 is to continue climbing and turn left to intercept N H W.

N-H-W, or November Hotel Whiskey, is

a ground-based navigation beacon that assists pilots

in guiding their plane through the skies.

Okay, direct November Hotel Whiskey.

And say again altitude?

Reconfirming the altitude instruction is smart.

Every aircraft have their assigned route

or assigned altitude by the ATC.

So that is very important to hold this altitude

to avoid the conflicts with others.

But as the pilots confirm their instructions,

the controller notices the plane has yet to turn towards

the N-H-W navigation fix.

Flight 6316 turn left direct to November Hotel Whiskey,

then climb and maintain 1,500 metres.

The controller can see on the radar scope

that the aircraft is not turning left.

And so is reminding the crew that they need to turn left

by reissuing the clearance.

But as the controller repeats his instructions...

I don't see NHW.

...the navigation fix does not appear

on the Captain's display screen.

Where is it?

Uh, here. Keep turning left.

Keep turning.

- Keep turning? - Yes, keep turning more.

As the pilots continue their turn,

the controller realizes the plane isn't climbing.

Korean Air 6316, climb and maintain 1,500 metres.

Are they asking us to--

Yes, they're... they're telling us to climb.

The aircraft hasn't even reached

the initial altitude that they were cleared to.

So this is a way to remind the crew,

we need to get moving, we need to climb.

Just as Flight 6316 nears its assigned altitude...

...it disappears from the radar.

The plane is diving uncontrollably towards

the ground, too fast to be picked up by radar.

The controller is unaware of its descent.

Korean Air 6316, do you read?

Wait, wait... pitch

Korean Air 6316, radio check.

Korean Air Flight 6316 bursts throh the clouds above Shanghai...

Terrain. Terrain.

Nose up. Nose up. Nose up.

Pull up. Pull up.

...and slams into the ground seven miles

from the airport...

...less than two-and-a-half minutes after takeoff.

At the speed they hit the ground,

the impact was so severe that it registered

the equivalent of a 1.6 earthquake.

The aircraft crashes in Xinzhuang

on the outskirts of the town's residential area.

The accident claims the lives of both pilots and the Flight Technician.

Five civilians are killed, 40 more are injured.

The investigation into the crash is handled jointly by the three countries involved.

Representatives from the Korean Civilian Aviation Bureau

are onsite on behalf of the airline.

With the crash occurring on Chinese soil,

the investigation is led by the Civil Aviation Administration of China.

And as the plane is manufactured in the U-S,

an American investigator from the National Transportation Safety Board joins the team.

What'd you find?

The debris trail runs nearly two kilometres. Fan pattern.

Typically, on impact, as the airplane hits the ground,

all of a sudden pieces will start coming apart.

The biggest pieces will keep going straight.

The other pieces will start fanning out. They'll spread.

They had to impact at a relatively shallow angle

to make that pattern.

But as investigators continue to analyze the crash site,

they learn that critical evidence has been destroyed.

Not much left of the Flight Data Recorder.

One of the major tools in a modern aircraft

accident investigation is the flight data recorder.

More modern ones can record thousands of parametres:

angle of attack, airspeed, engine parametres.

The lack of a flight data recorder during an investigation is a major blow.

Police say some of the cargo has been stolen

from the crash site.

In the chaos, some of the local residents

decided to help themselves to some of the cargo.

This creates a situation where investigators might not find

critical parts that they need to solve the accident.

Has anyone found the Cockpit Voice Recorder?

Hopefully that wasn't stolen too.

If you don't have a flight data recorder and you don't have

a cockpit voice recorder, you really have to go back to the basics

to try to figure out what happened.

Investigators start by examining "impact scars"

left by the engines to determine at what attitude

the plane struck the ground.

The ground slopes 30 degrees down from the horizontal.

Slope is the same for the other ground scar.

And wings were level.

The aircraft engines are very heavy.

They'll make their own craters.

So you look at the angle the engines are in,

that gives you a very good idea of the pitch angle at impact.

Because those parts are basically going to try

to just bore a hole into the dirt.

So the aircraft takes off.

Roughly three minutes later, it crashes in a dive 30 degrees nose down, with wings level.

So what caused the dive?

The ground information tells you

how the airplane went down.

We don't know why it went down.

And that takes a lot more effort.

We need to test for explosives.

Get at least a dozen specimens from the wreckage

and send those samples to the lab for testing.

Chinese authorities wonder if an act of terrorism could have caused the accident.

In any investigation, anything could have happened.

And one of those events could have been sabotage or a bomb.

So it's important in investigations to rule out

something like that, as soon as possible.

As police look for evidence of explosives,

investigators interview the Air Traffic Controller.

Anyone who talked to the crew is a witness to the investigation.

And the controller is the last person to talk to the crew.

So it was very important to get his impressions, what he did,

what he's hearing back from the pilots and understand what was happening that night.

To start, what stood out to you about the flight?

Takeoff seemed normal.

But afterwards, the pilots struggled to maintain the flight plan.

Turn left direct to November Hotel Whiskey.

Then climb and maintain 1,500 metres.

They eventually made their turn. But I had to remind them.

After that?

As they corrected their turn, I noticed they were still too low.

So I told them to climb.

Korean Air 6316, climb and maintain 1,500 metres.

I had to remind them a second time, before they started to climb.

I thought they were off safely.

The next thing I knew, the plane disappeared from radar.

The air traffic controller sees the aircraft climbing.

Everything looks normal and fine,

and then all of a sudden, things go very wrong.

Korean Air 6316, do you read?

Korean Air 6316, radio check.

- Is that the radar data? - Yes.

It looks like your communication was by the book.

Thank you.

Looking at the radar recordings is very important,

especially if you haven't looked at the cockpit voice recorder or the FDR.

This gives you an initial framework to work with.

Can the radar data provide any clues?

The plane climbs to 1,371 metres or 4,500 feet.

Roughly 16 seconds later, it impacts the ground.

That's a descent rate of roughly...

...17,000 feet per minute.

We have a saying in aviation called 'the minute to die rule',

which means that if your rate of descent in feet per minute

is greater than your altitude, that's a dangerous situation.

Flight 6316's rate of descent

was more than three times greater than their altitude.

Pull up.

It's virtually impossible to recover the aircraft.

What would cause the plane to descend at such an incredible speed?

Maybe there was a problem with the aircraft.

I'll pull the maintenance records.

During the initial stages of the investigation,

the investigators will look at all of the maintenance records of the aircraft.

Any write-ups of issues on handling,

delayed maintenance for some reason...

anything at all that would give a clue to what could have happened here.

Here's something.

Investigators examine maintenance records

of Korean Air Flight 6316,

looking for clues to explain why a modern jetliner

plunged from the sky so soon after takeoff.

On May 25, 1996, the aircraft experienced a tail strike at LAX.

The incident required a repair that took 63 days to complete?

That was an interesting finding because

if the repairs to the aircraft from the tail strike

are not done properly, it can cause that area to detach

in flight and in the process damage the pitch controls of the airplane.

And we've seen that before.

In 1978, a Japan Airlines Boeing 747

suffered a tail strike while landing at Osaka.

A faulty repair led to an explosive decompression

seven years later, tearing off the tail and killing 520 people.

If that's what happened here, that could explain everything.

Did poor maintenance cause the plane's tail to break apart mid-flight?

Well, here's the vertical stabilizer.

Investigators find pieces of Korean Air Flight 6316's tail section

in the wreckage.

With all the pieces of the tail this close to the main crash site,

it didn't separate in-flight.

So the repair was done correctly.

They conclude a tail strike did not cause

any part of the MD-11's tail to detach from the plane.

Maybe the dive was caused by a failure

in one of the plane's control surfaces.

Like the horizontal stabilizer.

The horizontal stabilizer is the small wing

on the tail that controls the pitch of the aircraft.

Maybe the jackscrew jammed?

When commanded, a jackscrew in the tail rotates,

moving the horizontal stabilizer up or down.

If the jackscrew has jammed in a nose down position,

now the airplane would suddenly pitch over

and the flight crew would be fighting to try

to get the nose up.

- Pitch. - O-oh-okay. Okay.

But they would have a lot of forces

on the control column, trying to fight the aircraft from pitching down towards the earth.

Was the horizontal stabilizer jammed

in a nose-down position, causing the plane to plummet?

Well, the jackscrew isn't jammed.

So the stabilizer was working as intended.

And what position is it in?

10.25 inches.

So it was set to .65 degrees, nose-up.

The pilots were fighting against the dive...

Nose up, nose up, nose up.

...trimming the horizontal stabilizer

nose up while pulling back on the controls

to try to arrest the descent.

Terrain, terrain.

Chemical analysis report is in from the wreckage.

No evidence of explosives.

I'll start typing this up for the press.

We need to reassure the public it's safe to fly in China.

Sounds good.

The Civil Aviation Administration of China

along with its U-S and Korean counterparts release a bulletin

almost two weeks after the incident.

The Chinese investigation want to make two things clear.

One, it's not a bomb.

Two, it's not a fault from the Chinese ATC controller.

With terrorism, air traffic control and poor maintenance discounted,

investigators now focus their attention to the pilots.

Let's start with the Captain.

In all accidents, one of the tasks

is investigating the background of the pilots

to ensure that there's no issues.

V-1. Rotate.

Rotate.

Training can make a very big difference.

And also, things going on in their personal life.

We want to make sure that the person wasn't under

any particular stressors that could cause distractions

and inhibit their performance in any way.

Captain Hong was quite seasoned.

Almost 13,000 flight hours, with nearly 5,000 on the MD-11 alone.

No psychological burdens and a perfect safety record.

Yeah. First Officer Park, over 1,800 hours, majority on the MD-11.

No psychological burdens and also a perfect safety record.

- Two model pilots. - Yeah.

Yes. Is it intact?

They found the Cockpit Voice Recorder.

After the accident, there was very heavy rain in the Shanghai area.

So they pumped out some water from some of the ponds

that were left and they found the CVR.

Memory is safe. Full data recovery.

Excellent work. And thank you.

They're going to get the transcripts ready for us.

At this point in the investigation, we're wondering what caused

a mechanically sound airplane piloted by two well-trained,

experienced pilots, to suddenly dive into the ground.

And that becomes the mystery.

Okay. Let's start with an aerodynamic stall

from 1,371 metres.

Using a Boeing simulator in California...

We'll see what rate of descent we get.

...investigators combine radar data with evidence

from the wreckage of Korean Air Flight 6316 to determine

why the plane plummeted to the ground.

In the simulator, the investigators accomplished

over a hundred different scenarios. Trial and error.

How do we match the data points?

Pull up.

Rate of descent was 3,314 feet per minute,

not even close to 17,000. It couldn't have been a stall.

And so, they take all this information

and in the simulator try to determine what's the best fit for the data.

And you start eliminating things.

Let's try Out of Control Elevators.

The accident plane impacted nose down

at an estimated 20 to 40 degrees.

The pitch is way too sharp.

Let's try to pull up anyway for accuracy.

Through all the simulator runs they did...

Pull up.

86 degrees.

Okay, it was not Out of Control Elevators either.

...they found that you could not match

the rate of descent and the profile you needed to match

the data with an aerodynamic stall or a mechanical failure.

Try intentionally pushing the plane into a dive...

Push your nose down.

Let vertical speed increase.

Then trim the horizontal stabilizer up,

then try to pull out of it.

Start the dive in three, two, one, go.

Stabilizer in motion. Pull up.

Only one simulation precisely replicates the data from Flight 6316.

Dive time, 18 seconds.

25 degrees nose down.

Maxed out rate of descent.

That's the closest we've been yet.

Investigators conclude that the plane

must have been put into a nose dive intentionally.

The data showed that the upset was caused by a pilot input.

And so now the focus becomes on, why would the pilot do this?

Knowing that the crash of Flight 6316

could have resulted only from deliberate pilot input,

investigators listen to the CVR to determine why the pilots

commanded the airplane into a steep dive.

Okay. Let's have a listen.

Captain, can you release the parking brake?

Okay, brake released.

Wow. Something's not right.

Why is that brake temperature light on?

Is the high brake temperature somehow connected to the nosedive?

Yeah, when we landed, that brake temp showed up.

But soon after...

It's dropping down now.

So the brake was a non-factor.

Agreed. Let's keep going.

Flight 6316, copy ATC clearance.

Go ahead, Korean Air 6316.

Korean Air 6316, after departure turn left

direct to November Hotel Whiskey.

Initially climb and maintain 900 metres.

Read back please.

Okay, sir, initially maintain 900 metres, then after takeoff,

left turn direct to November Hotel Whiskey. Is that correct?

That's affirmative.

- Did he say 900 metres? - Yeah, 900 feet.

Did you catch that?

After the controller read the altitude clearance.

Investigators hear that there's some confusion

about altitude measurements.

Yeah, why are they using metric at all?

Imperial is airspace standard.

Not in China.

Most of this world, including South Korea, measure altitude in feet.

The Chinese aviation industry is based on the old Soviet Union aviation industry.

The USSR used the Metric system, so today China still uses the Metric system.

Okay. But I imagine the Captain will sort that out

in the takeoff briefing.

Let's find out.

Korean Air 6316...

...clear for takeoff.

Clear for take off 6316.

Confirming, we're clear for takeoff.

Wait...

Did the Captain skip his takeoff briefing?

I'm not seeing one in here.

A takeoff briefing is a way to create

what we call "a shared mental model," where both pilots

are on the same page.

Otherwise you're simply not prepared for the flight.

The briefing would have also noted that Shanghai uses metric altitudes.

So did skipping the briefing

somehow play a role in the nose dive?

Investigators revisit the CVR

searching for evidence that the omission

of a critical briefing contributed to the crash of Flight 6316.

Let's start with the initial climb.

Turn left direct to November Hotel Whiskey,

then climb and maintain 1,500 metres.

The team hears the controller giving the pilots

their climb out instructions...

I don't see NHW.

Where is it?

...but the Captain can't find the navigation beacon on his display.

It sounds like an issue with the Captain's NAV display.

Uh... here. Keep turning left.

The recording suggests the First Officer's

navigation display was functioning properly.

- Keep turning - Keep turning?

Yes, keep turning more.

Damn. Why isn't NHW showing?

The CVR portrays a captain who appears confused.

I bet he zoomed in too far on the NAV display.

That's why he can't see the beacon.

Had the pilot reached up and changed the range on his display,

he would have had that available to him.

That would explain why it took them so long to turn left.

Had they done the takeoff briefing, they could have caught the issue.

Had they discussed completely in the preflight briefing,

here's where we're going, and cross-checked their displays

that would have been caught. And it wasn't.

It still doesn't explain the dive, though.

Korean Air 6316...

climb and maintain 1,500 metres.

Are they asking us to--

Yes, they're telling us to climb.

It seems like they're so preoccupied getting the plane

to turn left they forgot to climb.

Especially since the controller told them twice.

Then investigators hear a warning telling the pilots

that they're approaching their target altitude...

Altitude.

Uh, pitch, sir.

...the First Officer points out that they're climbing too quickly.

Why is he climbing so quickly?

His mistakes are adding up.

He's trying to overcompensate to get to his altitude.

He's pitching up too fast.

He's doing things too quickly.

Was the nosedive just another mistake?

How far are they telling us to climb?

He still doesn't know his altitude clearance.

It doesn't look like the First Officer knows either.

Fif...1,500 feet, sir.

Fif...

They're talking in terms of feet,

even though the controller's instructions were in metres.

Investigators now realize the controller

and the pilots are using different altitude measurements.

Weren't they trained to use metric?

Should be, but let's check.

Certainly the more training you have

that would have helped greatly in terms of sorting out

the metres versus feet.

I see. Thank you for your time.

They look deeper into the training procedures for Korean Air pilots.

Korean Air says the Seoul to Shanghai route

is the only one where their pilots need to use metric.

What kind of training did they have?

They require their pilots to watch a single training video

to learn metric conversion.

According to the pilot records,

the Captain had only flown into Shanghai once prior.

The First Officer had never flown there before.

Which means the First Officer would have watched

the training video for the first time only that morning.

Investigators conclude that the pilots

of Flight 6316 confused metric and imperial...

Fif... teen.

...because they were inadequately prepared for the flight.

For the pilots to operate in a metric environment,

this is something that you need to get into a simulator,

and you need practise it.

Watching a video is just not going to be enough, period.

So was the metric confusion the reason why they pushed

the plane into a nosedive?

How... How far did they tell us to climb?

As the flight reaches its assigned altitude

of 4,500 feet, or 1,500 metres...

Fif...1,500 feet, sir.

Fif...

...the First Officer leads the Captain

to believe they should be much lower, at 1,500 feet.

The Captain, thinking that they have blown through their clearance,

would be extremely alarmed, because now,

there is a very strong potential for a traffic conflict.

Fifteen... I'm too high.

Descend... descend... descend.

The quickest response is to push forward on the controls.

- Wait. Wait, wait, wait... - Just a moment.

The Captain pushes the plane into a steep dive

to descend to a much lower altitude.

You can hear the Captain trim the plane down.

He put them in the dive.

He pitches the aircraft nose down,

and simultaneously is trimming the horizontal stabilizer,

which relieves the control column pressure.

But the combination of these things put the aircraft

into a dive from which it's almost impossible to recover.

During descent, the First Officer suddenly

recognises the seriousness of their situation.

Wait, wait. Pitch

O-oh-okay. Okay.

But by the time the pilots realize the danger...

Nose up, nose up, nose up.

Pull up.

...it's too late.

Investigators conclude that the crash

was caused by the Captain's confusion over his altitude measurement.

Even if the Captain thought he was too high,

why not descend more gradually?

Wait, wait, wait, wait.

First, he climbed too quickly,

then he descended way too quickly.

Investigators try to determine why the Captain

of Korean Air Flight 6316 reacted so drastically

to his belief that the aircraft was too high?

Maybe he was trying to cover up his mistakes?

On one hand, the Captain knows

it is dangerous when they're overshooting the altitude.

How far did they tell us to climb?

On the other hand, the Captain doesn't want

the controller to know that he made a mistake.

So he tried to get down quickly to save face.

What I don't understand is,

why didn't the First Officer try to stop him?

Especially since he was guiding him earlier.

There's a lot going on, and the First Officer

is not only trying to read back the clearances

but also trying to ensure that the Captain is turning

in the direction that needs to be turned.

Keep turning.

- Keep turning? - Yes. Keep turning more.

I've got the CVR all set for the moment before the dive.

Did the First Officer ever recognize the error?

How far did they tell us to climb?

Fif... 1,500 feet, sir.

Uh... oh.

Wait. Wait, wait, wait.

Investigators hear the First Officer hesitate

after providing the Captain with the wrong altitude.

Maybe at that point the First Officer recognized his mistake

was feet and metres, we don't know.

Just-just a moment.

- Wait, pitch. - O-oh-okay. Okay.

So the dive starts and he says: "Wait, wait, wait".

Then after five full seconds of free fall, he says: "Wait, pitch".

Clearly, there should have been some input,

some effort from the First Officer to try to slow things down.

In my opinion, the First Officer was speaking

but he wasn't speaking up.

Wait. Wait, wait, wait.

Just-just a moment.

He gave little hints that things were going wrong to the Captain,

but it was apparent that the pilots were not on the same page.

At the end of the day, the Captain caused the dive.

He overreacted.

The rate of descent was so high,

that now it became very difficult to recover

once you got down to the lower altitudes.

And probably, they didn't realize the trouble they were in

until they could see breaks in the clouds and see the ground.

Terrain, terrain.

Nose up, nose up, nose up.

Pull up... Pull up.

In their final report, investigators conclude that confusion

over the metric system led the First Officer

to relay the wrong altitude.

How far did they tell us to climb?

Fif... 1,500 hundred feet, sir.

That mistake caused the Captain to overcompensate...

Wait. Wait, wait.

Just-just one moment.

...and push the aircraft into a fatal dive.

We can look at this as a training accident,

as much as anything else.

The way the pilots were trained at that time resulted

in a series of decisions and actions that put the airplane

in an unrecoverable situation.

In Chinese aviation industry, we have a motto:

Every line in the checklist is written in blood.

Because behind every line in the checklist is a disaster,

but it's an opportunity to improve.

One of the recommendations was that Korean Air reinforce

its cockpit resource management training.

It's part of the fabric that holds a safe flight together.

And that includes things like a pre-takeoff briefing.

So these are some of the items that, in my mind, were most important.

Today, Korean Air is recognized

as one of the safest airlines in the world.

The amount of standardization through all the airlines,

the amount of training now is a much higher level than it was before.

The digital airplanes, there's a button you can turn,

and all your display shows metres instead of feet.

But it does bring up the need for vigilance.

This crew made so many errors.

Losing control of a big airplane is very unusual.

And hopefully, we won't see it again.

Subtitling: difuze