Original subtitles

Halloween 1994, a commuter

Halloween 1994, a commuter

plane circles outside Chicago waiting for clearance to land.

plane circles outside Chicago waiting for clearance to land.

Eagle flight 184, descend and maintain 8,000.

Eagle flight 184, descend and maintain 8,000.

Done.

8,000 Eagle 184.

8,000 Eagle 184.

Without warning, the controls snap to the right.

Without warning, the controls snap to the right.

The plane plunges straight toward the ground.

The plane plunges straight toward the ground.

Pilots who had questioned the safety of an airplane.

The airplane will have a nasty tendency to go out of control.

The airplane will have a nasty tendency to go out of control.

Investigators travel the world for answers.

The crash makes Roselawn one of aviation's darkest words.

The crash makes Roselawn one of aviation's darkest words.

Ladies and gentlemen, we are starting our approach.

We lost both engines.

...the mask over your nose.

- Emergency... - Mayday!

- Emergency... - Mayday!

Mayday!

Brace for impact!

It's gonna crash!

It's mid-afternoon on October 31, 1994.

It's mid-afternoon on October 31, 1994.

American Eagle flight 4184 left Indianapolis,

American Eagle flight 4184 left Indianapolis,

Indiana, 15 minutes ago.

It's heading to Chicago.

There are 68 passengers and crew on board.

There are 68 passengers and crew on board.

Happy Halloween, cowboy.

Thank you.

Thank you.

Flying through the clouds, the aircraft

Flying through the clouds, the aircraft

begins to experience some turbulence.

I'm going to keep them in their seats in this chop.

No sense in taking chances.

No sense in taking chances.

Captain Orlando Aguilar is

in command of today's flight.

It's supposed to be his day off.

He volunteered for this flight to make extra money.

He volunteered for this flight to make extra money.

His wife is expecting their second child.

His wife is expecting their second child.

Let's see if we can get above this.

Is there any chance flight 184 can climb to one 6,000?

Is there any chance flight 184 can climb to one 6,000?

Flight 184, maintain one 6,000.

First officer Jeff Gagliano

First officer Jeff Gagliano

is handling the flight duties on this leg of the flight.

He programs the autopilot to climb

He programs the autopilot to climb

to a less turbulent altitude.

Jeff actually was working on his dad's ranch in Wisconsin

Jeff actually was working on his dad's ranch in Wisconsin

just before he came in for that trip on Halloween that day.

just before he came in for that trip on Halloween that day.

Getting on a horse or getting in an airplane,

those were two of the things that Jeff loved most.

Flight 4184 is an ATR 72, a groundbreaking

new aircraft built in France.

new aircraft built in France.

Cost efficient and comfortable, the plane has

Cost efficient and comfortable, the plane has

become popular on short runs.

This flight is just one of five short hops

This flight is just one of five short hops

the crew will be making today.

Aguilar and Gagliano have flown this route countless times

and know it by heart.

and know it by heart.

When you're flying from Indianapolis to Chicago,

you're flying through some of the busiest

you're flying through some of the busiest

airspace in the world.

As flight 4184 approaches Chicago O'Hare,

As flight 4184 approaches Chicago O'Hare,

the pilots begin the descent to 10,000 feet.

Chicago center, we have discretion down to one

Chicago center, we have discretion down to one

zero thousand.

We're on our way down now.

We're on our way down now.

Zero 184, roger.

Zero 184, roger.

In Chicago, controller Michelle Willman

is returning from a break.

She's told that traffic into O'Hare

is facing potential delays because of weather.

is facing potential delays because of weather.

She will have to be prepared to put some flights on hold.

Operations into and out of O'Hare

Operations into and out of O'Hare

are handled on a priority basis.

It's not necessarily a first come, first serve basis.

It's not necessarily a first come, first serve basis.

International flights arriving to O'Hare,

because of their fuel status, get priority.

And then the turboprops come in at the end.

And then the turboprops come in at the end.

Eagle 184, holds southeast on victor seven.

Eagle 184, holds southeast on victor seven.

Chicago center, roger.

Hold southeast on victor seven.

Eagle 184.

Eagle 184.

Flight 4184 must now fly

a racetrack-shaped holding pattern

over northwestern Indiana.

over northwestern Indiana.

Chicago center, Eagle 184, entering the hold.

Chicago center, Eagle 184, entering the hold.

Eagle 184, roger.

Eagle 184, roger.

Aguilar programs the autopilot to keep the plane

circling at 10,000 feet.

I'll go up front and see if they want anything.

Can I get you boys anything?

I'm good.

Man, this thing gets a real high tech angle in these turns.

Yeah.

We're just wallowing in the air right now.

We're just wallowing in the air right now.

You want flaps 15?

It'll bring the nose down.

Sure.

And I guess Sandy's going "woo" now.

And I guess Sandy's going "woo" now.

Well, see y'all.

All right.

The crew needs to let the airline

The crew needs to let the airline

know about their delay.

It could affect the rest of the day's schedule.

Crews use text messages to communicate

Crews use text messages to communicate

with dispatchers so they don't tie up radio frequencies.

Should I let them know how much fuel we got?

Should I let them know how much fuel we got?

Sure.

Space F-U-E-L, is that...

Space F-U-E-L, is that...

we got 3,600 pounds.

Well, folks, once again, this is the captain.

Well, folks, once again, this is the captain.

I do regret to inform you that air traffic control has put us

into a holding pattern up here.

We're holding for approximately 20 minutes out of Chicago

We're holding for approximately 20 minutes out of Chicago

at this time.

I do apologize for all the delays.

I do apologize for all the delays.

That's much nicer now, flaps 15.

Once they let us out of the hold and forget they're down,

Once they let us out of the hold and forget they're down,

we'll get the overspeed warning.

Eagle flight 184, descend and maintain 8,000.

Danny, 1,000 Eagle 184.

Danny, 1,000 Eagle 184.

Eagle flight 184, should be about 10

Eagle flight 184, should be about 10

minutes till you're cleared in.

Thank you.

The flight is allowed to descend.

The flight is allowed to descend.

Are we out of the hold?

No.

Just going down to 8,000.

Just going down to 8,000.

Then a warning.

Ah, I knew we'd do that.

Ah, I knew we'd do that.

The plane is going too fast

to fly with its flaps extended.

I was trying to keep it at 180.

I was trying to keep it at 180.

Gagliano retracts the flaps.

There's a strange sound coming through the fuselage.

There's a strange sound coming through the fuselage.

Suddenly, the control column turns sharply to the right.

Suddenly, the control column turns sharply to the right.

God damn it!

Uh!

The controls won't budge.

Looks like the plane is starting to recover.

Looks like the plane is starting to recover.

The plane is falling from the sky.

The plane is falling from the sky.

The pilots begin to recover control,

The pilots begin to recover control,

but then it happens again.

Mellow out!

Mellow out!

Tony, rolled up.

See, that's it.

Nice and easy.

Pull up... terrain.

Pull up.

Pull up.

It was coming down too steep to even try to land.

It was coming down at an...

I mean, a sharp angle... a real sharp angle.

Flight 4184 has crashed into a field

Flight 4184 has crashed into a field

just outside Roselawn, Indiana.

Both pilots, the two flight attendants,

and all 64 passengers are dead.

and all 64 passengers are dead.

The Roselawn crash would soon become

The Roselawn crash would soon become

one of the most important accidents in aviation history.

one of the most important accidents in aviation history.

It will lead investigators to new conclusions about a string

of older crashes.

of older crashes.

The morning after the crash of American Eagle flight 4184,

a team from the National Transportation Safety Board

a team from the National Transportation Safety Board

is on the scene just outside Roselawn, Indiana.

Greg Feith is the lead investigator.

The morning that we arrived at the accident site, it was cold.

The morning that we arrived at the accident site, it was cold.

It was overcast.

It was one of those drizzly, dank days.

It was one of those drizzly, dank days.

All you could smell was the jet air or the kerosene fuel.

And because it was muddy and wet,

you had that odor, or that aroma, of dirt.

you had that odor, or that aroma, of dirt.

And so with all of those smells, that...

I mean, that really evokes some emotion there.

I mean, that really evokes some emotion there.

And now you have to walk through that field

and actually start to do your job.

With 4184, it was one of those types

With 4184, it was one of those types

of accidents where there was very

little left of the airplane.

Investigators know that the way

Investigators know that the way

the wreckage is spread out can tell them

how the plane hit the ground.

Because there was a fan-shaped debris pattern and it was

spread out over a very large area,

spread out over a very large area,

we knew that the impact was very shallow

but at a very high speed.

The airplane's two flight recorders

are found intact in the tail.

are found intact in the tail.

They're taken to the NTSB's labs for analysis.

They're taken to the NTSB's labs for analysis.

The data on the recorders could provide the clues

investigators need to solve the mystery

investigators need to solve the mystery

of what caused this crash.

But extracting the data takes time.

But extracting the data takes time.

In the meantime, investigators look for the location

of key pieces of wreckage.

The first things we typically look for are the four

The first things we typically look for are the four

corners of the airplane.

The NTSB's Bob Swaim leads that search.

The NTSB's Bob Swaim leads that search.

You're looking for the nose and the tail

and the two wingtips.

Because if you can tell where the four corners

Because if you can tell where the four corners

of the airplane are, you get an initial idea

of whether the pilot was in control or not.

of whether the pilot was in control or not.

The plane's four corners

are far away from each other.

are far away from each other.

The nose and cockpit are completely destroyed.

This tells investigators that the plane

hit the ground nose first in a shallow but rapid descent.

hit the ground nose first in a shallow but rapid descent.

- Oh my god! - Mellow it out!

- Oh my god! - Mellow it out!

Mellow out!

Uh.

The fact that the plane wasn't in a steep descent

on impact indicates that the pilots

on impact indicates that the pilots

had some control in the final seconds before the crash...

they just ran out of room to pull up.

Investigator Bob Swaim, meanwhile, has recovered some

of the plane's instruments... including

of the plane's instruments... including

its Attitude Director Indicator, also known

as the "artificial horizon."

as the "artificial horizon."

It's a key instrument that tells pilots if they're flying level.

If it malfunctioned, it could have misled the crew

If it malfunctioned, it could have misled the crew

and caused them to make mistakes.

A lot of the cockpit pieces use a fluorescent paint,

or something similar.

And when they contact each other,

And when they contact each other,

little, little bits of the paint transfer.

If we look at those with a black light, we can see things

If we look at those with a black light, we can see things

that the naked eye cannot see.

that the naked eye cannot see.

The force of the impact

has left tiny scratches on the shattered instrument.

Swaim discovers that the attitude indicator

seems to have been working.

seems to have been working.

Its final readings show the plane was leveling off.

The instrument coincides with the plane's

The instrument coincides with the plane's

actual position on impact.

The discovery means that the pilots knew their plane

The discovery means that the pilots knew their plane

was diving toward the ground.

Investigator Greg Feith is getting a clearer picture

Investigator Greg Feith is getting a clearer picture

of the flight's final seconds.

Now he wants to know about the history of this flight

Now he wants to know about the history of this flight

before it fell from the sky.

One of the elements of the investigation, of course,

One of the elements of the investigation, of course,

was to look at air traffic control.

Eagle 184, hold southeast on victor seven.

Eagle 184, hold southeast on victor seven.

Feith learns that flight 4184 had been

Feith learns that flight 4184 had been

in a holding pattern southeast of Chicago

for 39 minutes before the crash.

When we looked at the air traffic control records,

When we looked at the air traffic control records,

we found that the flow rate... that is,

the number of airplanes that were going into Chicago

the number of airplanes that were going into Chicago

O'Hare at the time...

had to be reduced because of the weather

moving through the area.

Well, folks, I do regret to inform you

Well, folks, I do regret to inform you

that air traffic control has put us into a holding pattern

up here.

And because of the reduced rate into Chicago,

And because of the reduced rate into Chicago,

we knew that 4184 was going to have to hold

for a very long period of time.

for a very long period of time.

Chief investigator Greg Feith

wants to know more about the weather conditions

along the holding pattern.

along the holding pattern.

So I want weather data, pilot reports,

So I want weather data, pilot reports,

atmospheric conditions, Doppler radar,

or anything you can find.

Flight 4184 wasn't the only plane

circling O'Hare that day.

circling O'Hare that day.

Several other planes were also on hold.

They all landed safely.

They all landed safely.

Interviews with the pilots of some of those planes

Interviews with the pilots of some of those planes

give investigators an important clue.

One after another, they all experienced icing...

One after another, they all experienced icing...

some as much as 3/4 of an inch.

Many of the pilots report the same thing...

Many of the pilots report the same thing...

ice.

Dr. Marcia Politovich works at the National Center

for Atmospheric Research.

for Atmospheric Research.

She's one of the leading experts on icing,

and the danger it poses to aircraft.

and the danger it poses to aircraft.

This essentially changes the shape of the wing

while you're in flight.

It creates drag, it reduces lift,

It creates drag, it reduces lift,

it causes performance and handling problems,

and it's just not a good thing to have.

and it's just not a good thing to have.

Investigators examine weather records

Investigators examine weather records

from the day of the crash.

They find a disturbing pattern of reports of icing all

They find a disturbing pattern of reports of icing all

along a cold front near Chicago, but the reports describe

the icing as light to moderate.

the icing as light to moderate.

Perhaps the size of the commuter plane

was a factor in this crash.

was a factor in this crash.

Yeah, different planes respond to icing differently.

A large plane will respond differently than a small plane.

A large plane will respond differently than a small plane.

Reasons for that are both environmental

and having to do with the airframe itself.

and having to do with the airframe itself.

Large jets generally fly

above the dangerous conditions inside a cloud,

above the dangerous conditions inside a cloud,

but the ATR 72 can't do that.

but the ATR 72 can't do that.

Smaller plane can't fly as high,

they're stuck in the icing environment for longer.

they're stuck in the icing environment for longer.

They may not have de-icing equipment.

And if they get in trouble, they may not

have enough excess power to get out of it.

have enough excess power to get out of it.

Investigators discover that flight

4184's holding pattern took it through layers of clouds

4184's holding pattern took it through layers of clouds

repeatedly.

Each time, it would have been exposed to icing conditions.

Each time, it would have been exposed to icing conditions.

4184 we knew had been holding in an icing event.

There were layers of clouds that they

There were layers of clouds that they

have been flying in and out of.

Steve Frederick was flying out of Chicago

on the morning of the crash.

on the morning of the crash.

He flew through the same treacherous weather.

Each time that I went through that cold front

Each time that I went through that cold front

during that day, the weather was intensifying.

The ice was getting worse, and I was getting

The ice was getting worse, and I was getting

more and more concerned.

Frederick asked his captain

to pass on a warning about the weather

to pass on a warning about the weather

so that other pilots would be alerted to the danger.

I found out a little bit later on that my captain had never

I found out a little bit later on that my captain had never

warned dispatch, and these pilots

never got the warning about the ice

that was out there that day.

that was out there that day.

And there's no feeling in the world that can compare to how

badly I felt at that moment.

badly I felt at that moment.

Greg Feith knows that, along with American Eagle

flight 4184, controllers had put several other planes into

flight 4184, controllers had put several other planes into

a holding pattern near Chicago.

But they all landed safely after coming out of the hold.

But they all landed safely after coming out of the hold.

One of the issues about air traffic control is that

the controllers can't just look at their radar screen

the controllers can't just look at their radar screen

and identify areas of... of precipitation

or icing conditions readily.

The controllers don't know that an airplane is sitting in icing

The controllers don't know that an airplane is sitting in icing

conditions unless the pilot provides

them with what they call a PIREP, or a pilot report.

them with what they call a PIREP, or a pilot report.

So if the crew, in this case 4184,

So if the crew, in this case 4184,

doesn't provide that information to the controller,

then the controller doesn't know that an icing event actually

is occurring out there.

is occurring out there.

Feith and his team wonder if the flight

crew simply didn't realize they were

flying into icy conditions.

flying into icy conditions.

The plane's cockpit voice recorder provides the answer.

The plane's cockpit voice recorder provides the answer.

Oh, that's much nicer now... flaps 15.

Oh, that's much nicer now... flaps 15.

Yeah.

Showing some ice now.

Showing some ice now.

I say let us out of the hold and forget...

But nine minutes before the crash,

the crew had noticed their plane was picking up ice.

the crew had noticed their plane was picking up ice.

The pilots must have been aware that they

were flying through an area of aircraft icing.

were flying through an area of aircraft icing.

You haven't heard any more from this controller, huh?

Nope, not a word.

Nope, not a word.

Then, two minutes before the accident,

another remark draws the attention of investigators.

another remark draws the attention of investigators.

We still got ice.

I see what you mean.

The crew knew about the ice.

Now investigators need to know what they did about it.

Now investigators need to know what they did about it.

The ATR 72 is equipped with sophisticated de-icing devices.

The ATR 72 is equipped with sophisticated de-icing devices.

It's crucial to know what the crew did about the ice buildup

on their wings.

This time, the flight data recorder provides the answers.

This time, the flight data recorder provides the answers.

Almost 17 minutes before the crash,

Almost 17 minutes before the crash,

something sets off the Master Caution Warning.

It could signal a problem in one of the plane's systems.

It could signal a problem in one of the plane's systems.

It could also mean the electronic ice detector is

picking up the presence of ice.

picking up the presence of ice.

The flight data recorder shows investigators that, in response

The flight data recorder shows investigators that, in response

to the alert, Captain Aguilar turned the plane's de-icing

to the alert, Captain Aguilar turned the plane's de-icing

system to its maximum setting.

The NTSB's Charley Pereira looks into the performance

of the ATR 72.

of the ATR 72.

The icing alert system had sounded orally,

and they heard it and they activated protection

and they heard it and they activated protection

systems on the airplane.

And at the time of the accident, the de-ice systems were on.

And at the time of the accident, the de-ice systems were on.

The complete ice protection system on the ATR 72 airplane

The complete ice protection system on the ATR 72 airplane

consists of a combination of what we call

anti-icing, which are hot surfaces that

anti-icing, which are hot surfaces that

don't allow the ice to form.

Windshields and the propellers are

also heated on this airplane.

also heated on this airplane.

And then they have de-ice systems,

which are on the leading edges of the wings...

what are called pneumatic boots.

what are called pneumatic boots.

They're like rubber inflatable chambers

that you blow air into, and they expand kind of like a balloon.

And that cracks the ice, then the ice flies off the airplane.

The flight data recorder

shows that after he activated his de-icing system,

shows that after he activated his de-icing system,

Captain Aguilar also pushed the throttle forward slightly,

increasing the plane's speed.

increasing the plane's speed.

This increased the speed of the air moving

over the plane's wings, making it

harder for ice to settle there.

harder for ice to settle there.

The pilots had done everything they could to deal

with ice buildup on the plane.

with ice buildup on the plane.

But were the anti-icing systems actually working?

But were the anti-icing systems actually working?

The shattered remains of that de-icing system

The shattered remains of that de-icing system

are now the main focus of the investigation.

The airplane was designed

in France by a group of French and Italian companies.

in France by a group of French and Italian companies.

The de-icing system was part of that design.

The de-icing system was part of that design.

So the components were made by small French vendors who were

So the components were made by small French vendors who were

located around the countryside, and then

they were assembled there in Toulouse

into the final airplane.

into the final airplane.

Bob Swaim arrives in France with pieces

Bob Swaim arrives in France with pieces

of the de-icing system.

I brought some pieces from flight 4184 to look at.

The key component to the de-icing system

The key component to the de-icing system

is probably not the black rubber boot

that you see on the airplane, but the timer that's inside

that you see on the airplane, but the timer that's inside

the airplane, or the timers, and the valves

that control those boots.

The force of the crash has left telltale markings

The force of the crash has left telltale markings

called "index marks."

They show the position of the valves at the time of impact.

They show the position of the valves at the time of impact.

Swaim compares them to the original blueprints.

Does anything seem out of the ordinary?

Does anything seem out of the ordinary?

The trip to France has led to yet another dead end.

The trip to France has led to yet another dead end.

There was nothing wrong with the plane's de-icing system.

There was nothing wrong with the plane's de-icing system.

Thanks a lot.

I appreciate it.

Thank you.

Investigators are puzzled.

Showing some ice now.

If the crew knew they had ice on their wing

If the crew knew they had ice on their wing

and their de-icing system was working,

why did the plane crash?

Other pilots think they know the answer,

and decide to speak out.

and decide to speak out.

Their decision will dramatically change the course

of this investigation.

of this investigation.

Three weeks after the crash, American Eagle pilot Steve

Three weeks after the crash, American Eagle pilot Steve

Frederick distributes a warning.

It says, "The ATR 72 fleet operated by American Eagle

is dangerous in icing conditions."

is dangerous in icing conditions."

It claims American Eagle pilots have

pleaded with the airline and regulators

pleaded with the airline and regulators

to do something about it...

but to no effect.

I drafted and distributed a brochure in Chicago O'Hare

I drafted and distributed a brochure in Chicago O'Hare

airport which essentially warned people about the problems

with the ATR aircraft, and made an outreach to the public

with the ATR aircraft, and made an outreach to the public

in order to try and get something done

because nothing was happening.

because nothing was happening.

Steve Frederick has more

than a professional interest in the crash of Flight 4184.

than a professional interest in the crash of Flight 4184.

Co-pilot Jeff Gagliano was his close friend.

They graduated from flight school together.

They graduated from flight school together.

Gagliano's death has hit him hard.

He made the comment one time that he would probably

He made the comment one time that he would probably

wind up dying because of ice in an ATR,

and it was eerily prophetic.

and it was eerily prophetic.

A month after the crash of American Eagle flight

4184, pilot frustration over the ATR's airworthiness boils over.

4184, pilot frustration over the ATR's airworthiness boils over.

A group of a dozen pilots refuses to fly,

A group of a dozen pilots refuses to fly,

citing risky weather.

The airline is forced to cancel flights.

And then Steve Frederick goes one step further.

And then Steve Frederick goes one step further.

He voices his concerns on a network TV morning show.

He voices his concerns on a network TV morning show.

We were told this airplane will try and kill you.

If you get too slow in ice, the... the airplane

will have a nasty tendency to go out of control.

will have a nasty tendency to go out of control.

When I came back to flying after my appearance

on "Good Morning America," I was summarily

on "Good Morning America," I was summarily

suspended without pay.

The public protest leads

investigators to wonder if the ATR 72 has

investigators to wonder if the ATR 72 has

a deadly vulnerability to ice.

Merci.

Merci.

Investigator Charley Pereira

visits the ATR's French manufacturer, Aerospatiale,

visits the ATR's French manufacturer, Aerospatiale,

to learn more about the plane's history.

We embarked on a research effort

We embarked on a research effort

to try to identify all previous ATR 42

and 72 roll control incidents.

and 72 roll control incidents.

He finds a disturbing pattern.

He finds a disturbing pattern.

And about five...

five of those were found to be similar, after the fact,

five of those were found to be similar, after the fact,

in our review to the Roselawn case.

One such incident took place in December 1988

One such incident took place in December 1988

in Mosinee, Wisconsin.

in Mosinee, Wisconsin.

An American Eagle ATR 42 had been

preparing to land in icy conditions

at Central Wisconsin Airport.

at Central Wisconsin Airport.

The airplane was on approach in severe icing conditions...

The airplane was on approach in severe icing conditions...

described as freezing drizzle and freezing rain.

Captain Mike Bodak was the pilot that day.

Captain Mike Bodak was the pilot that day.

We were just on the last two legs of our trip

before we'd be done with work, and we were doing our descent.

before we'd be done with work, and we were doing our descent.

Everything was proceeding normally.

Everything was proceeding normally.

Negative ice, just wet.

We'll call the flight center and let them

know we're turning inbound.

know we're turning inbound.

I hear in the tail a sound, "baa, baa,

baa, baa, baa, baa," like that, but it

baa, baa, baa, baa," like that, but it

just got louder and louder.

We have no idea what is occurring.

We have no idea what is occurring.

I thought initially a propeller blade may have come off.

I thought initially a propeller blade may have come off.

It was as if the steering wheel wasn't connected to anything.

The plane stalls.

The plane stalls.

Its wings can't generate enough lift to keep it in the air.

As I see I'm not getting any of the airplane back,

I come up on the power levers...

I come up on the power levers...

all the way.

The engines are now really trying to fly.

And at this point, I'm getting some of the airplane back.

And at this point, I'm getting some of the airplane back.

So I make a forward motion to try and break the stall,

and it's still going to "terrain, terrain"

and it's still going to "terrain, terrain"

and I don't have the airplane back yet.

And my first officer says...

Drop!

And I say, Max RPM.

And I say, Max RPM.

Terrain, terrain.

And he throws the props from 86% to 100%,

And he throws the props from 86% to 100%,

and instantaneously, boom, we fly out of this stall.

and instantaneously, boom, we fly out of this stall.

Woo!

The plane is less than 1,200 feet above the ground.

Captain Bodak has learned a sobering lesson about the ATR.

Captain Bodak has learned a sobering lesson about the ATR.

There was no warning.

There was no warning.

The plane stalled without any warning.

Planes do have warnings for stalls, but in this case

Planes do have warnings for stalls, but in this case

there was no warning.

I got... the first warning that I was in a stall

was I was in a stall.

But other pilots weren't as lucky.

But other pilots weren't as lucky.

An ATR 42 operated by an Italian airline

was flying over the Alps en route to Germany

was flying over the Alps en route to Germany

in October 1987.

The plane lost control and crashed in the mountains,

The plane lost control and crashed in the mountains,

killing all 37 people on board.

Ice was the main factor, but the final report

Ice was the main factor, but the final report

blamed pilot procedures.

For investigators, it's really important

For investigators, it's really important

to look back at historical information about any airplane.

You want to look for trends.

What they would find is a troubling detail

What they would find is a troubling detail

with this plane's history.

Did any of your studies uncover a wing design flaw?

Did any of your studies uncover a wing design flaw?

Charley Pereira wants to know if the engineers who

Charley Pereira wants to know if the engineers who

built the plane could explain why an ATR 72 would

go so badly out of control.

go so badly out of control.

To his surprise, he learns they knew that it

had a susceptibility to icing.

had a susceptibility to icing.

You've seen the flight data from the accident flight.

Where will the ice have formed to cause that?

Where will the ice have formed to cause that?

When I asked one of their oldest,

most senior aerodynamicists who couldn't speak any English

at all what he thought would be the shape and location

at all what he thought would be the shape and location

of an ice accretion that could cause

of an ice accretion that could cause

the behavior that we saw on the flight recorder

for the Roselawn airplane.

He drew up the airfoil section...

He drew up the airfoil section...

a little shape just behind the de-ice boots...

and said "this was it."

and said "this was it."

And the translation was that this is

what will cause this problem.

After the de-icing boot.

After the de-icing boot.

Investigator Charley Pereira

is beginning to understand how ice can affect the wings

is beginning to understand how ice can affect the wings

of the French-built plane.

If the ice built up behind the boot,

If the ice built up behind the boot,

the crew would have no way to clear it.

We still got ice.

And even a small amount of ice

And even a small amount of ice

can have a devastating effect on an airplane.

Ice can disrupt the smooth movement of air over the wing.

But how could so much ice build up behind the boot?

But how could so much ice build up behind the boot?

Investigators contact Dr. Marcia Politovich for assistance.

Investigators contact Dr. Marcia Politovich for assistance.

The NTSB called us to help them analyze weather

The NTSB called us to help them analyze weather

conditions in this case.

Her research shows that the pilots of flight 4184

Her research shows that the pilots of flight 4184

likely flew into something they'd never even heard of,

likely flew into something they'd never even heard of,

something even more dangerous than ordinary ice.

Yeah, based on the weather analysis,

Yeah, based on the weather analysis,

it looked to us like the kind of icing

that the plane encountered was from supercooled large drops.

that the plane encountered was from supercooled large drops.

Now, "large" is relative.

What we're talking about large here

is about the size of a human hair.

is about the size of a human hair.

Supercooled large droplets are about 100

times smaller than a raindrop.

They form inside storm clouds when the temperature

They form inside storm clouds when the temperature

is near freezing.

But the drops don't freeze until they come into contact

But the drops don't freeze until they come into contact

with something solid...

like the wing of an airplane.

Conditions that day were ideal for the formation of

these tiny, freezing droplets.

these tiny, freezing droplets.

On every lap of its holding pattern,

flight 4184 flew through layers of clouds that

flight 4184 flew through layers of clouds that

hid a small but lethal element.

They just put that poor guy in the wrong place

They just put that poor guy in the wrong place

at the wrong time.

Investigators learn that

supercooled large droplets, or SLDs,

supercooled large droplets, or SLDs,

have a distinctive way of accumulating

on an aircraft wing.

Ordinary ice accumulates on the leading

edge of the wing where de-icing boots can get rid of it easily.

edge of the wing where de-icing boots can get rid of it easily.

But SLDs act differently.

These supercooled drops hit the wing and slide

These supercooled drops hit the wing and slide

back over it before freezing.

This forms a ridge behind the boots,

This forms a ridge behind the boots,

out of reach of the de-icing system.

So as 4184 was flying in that type of environment,

So as 4184 was flying in that type of environment,

rather than the water droplet freezing on the protected

surface, or the de-ice boot, it actually

surface, or the de-ice boot, it actually

ran behind the de-ice boot and froze on the metal surface.

The pilots can't get a good view of their wings

The pilots can't get a good view of their wings

from the cockpit.

It's showing some ice now.

They would have been utterly unaware of the danger

They would have been utterly unaware of the danger

taking shape.

For Greg Feith, the investigation

is coming to a head.

His investigators think they know why flight 4184 crashed,

His investigators think they know why flight 4184 crashed,

but they can't prove it.

but they can't prove it.

To make matters worse, the plane's manufacturer

suggests that the Roselawn crash wasn't caused by an ice

suggests that the Roselawn crash wasn't caused by an ice

buildup, but by poor piloting.

The NTSB thought it was an aircraft problem.

And the French aircraft manufacturer

thought it was a pilot problem, and not

thought it was a pilot problem, and not

their particular product.

Feith wants to know if there

had been problems with ice on ATR-built planes in the past.

had been problems with ice on ATR-built planes in the past.

He finds troubling similarities between some incidents

He finds troubling similarities between some incidents

dating back decades.

Using data from flight data recorders,

Using data from flight data recorders,

investigators look at ailleron movements from flight 4184

and compare them to the other incidents.

and compare them to the other incidents.

They discover that on all those flights,

They discover that on all those flights,

the ailleron deflected in exactly the same way.

the ailleron deflected in exactly the same way.

There's no input at all from the pilots.

We knew that all of these aillerons

We knew that all of these aillerons

were being commanded to move...

not by the pilot, but in fact, the disrupted airflow

created by the icing event that the airplane had encountered.

created by the icing event that the airplane had encountered.

The physics of ice buildup explains

The physics of ice buildup explains

why the control column on flight 4184 snapped to the right.

why the control column on flight 4184 snapped to the right.

Air turbulence on the wing was so powerful

that it lifted the ailleron, which caused the plane to roll.

that it lifted the ailleron, which caused the plane to roll.

Since the ailleron is attached to the control column

by a cable, it jerked the control yoke to the right.

by a cable, it jerked the control yoke to the right.

The force of the turbulence pulling on the ailleron

was so great, that even two pilots trying to counter steer

was so great, that even two pilots trying to counter steer

weren't able to bring the ailleron back down.

The forces were determined to be about 250 pounds.

The forces were determined to be about 250 pounds.

So for the pilot, it would have been trying to roll against 250

So for the pilot, it would have been trying to roll against 250

pounds of aerodynamic force.

For chief investigator Greg Feith,

For chief investigator Greg Feith,

supercooled water droplets that left a ridge of ice

on the wings are now the prime suspect.

on the wings are now the prime suspect.

But how to prove it?

We had to try and model this icing event some way.

We had to try and model this icing event some way.

At the time of the crash,

NASA was just beginning to study the effect of supercooled

NASA was just beginning to study the effect of supercooled

large droplets on airplanes.

large droplets on airplanes.

Back in 1994, pilots didn't know

what SLD, or supercooled large droplets, were.

what SLD, or supercooled large droplets, were.

There was very little information in the pilot

community, and there was actually

very little information in the aviation industry about SLD.

very little information in the aviation industry about SLD.

Investigators first turn to NASA for help.

Together, they launch a daring experiment.

Together, they launch a daring experiment.

They use an Air Force tanker plane to create a cloud

They use an Air Force tanker plane to create a cloud

of supercooled water droplets.

An ATR 72 flies behind the tanker.

Yellow dye in the water shows investigators how

Yellow dye in the water shows investigators how

the droplets cover the plane.

The test should solve the final mystery...

The test should solve the final mystery...

how had ice caused flight 4184 to go so badly out of control?

how had ice caused flight 4184 to go so badly out of control?

One of the primary purposes of flying the ATR 72

in behind the tanker was to understand how the ice

in behind the tanker was to understand how the ice

accumulated on the airplane.

But more importantly, the effect of that ice in varying

But more importantly, the effect of that ice in varying

configurations of the airplane on the flight control

surfaces... that is, the aillerons.

Investigators make a startling discovery.

Investigators make a startling discovery.

A seemingly harmless action meant

to increase comfort on the plane may have led to disaster.

to increase comfort on the plane may have led to disaster.

I think it's a real high deck angle in these terms.

Yeah.

Captain Aguilar knows that the plane's high nose

angle is producing an uncomfortable tilt

angle is producing an uncomfortable tilt

in the passenger cabin.

You want flaps 15?

That'll bring the nose down.

Sure.

Extending the flaps would have

the effect of lowering the plane's nose,

making the ride more comfortable.

making the ride more comfortable.

When investigators duplicate this maneuver,

they find that it has a dramatic effect on where the ice ridge

they find that it has a dramatic effect on where the ice ridge

forms on the plane's wing.

The flaps make the icing problem even worse.

The flaps make the icing problem even worse.

By exposing more of the upper surface of the wing

to the oncoming water droplets.

to the oncoming water droplets.

And that's one of the reasons why we got...

the ridge of ice where we got it was because

of the flaps' 15 configuration.

of the flaps' 15 configuration.

Oh, that's much nicer now, flaps 15.

Yeah.

The crew of flight 4184

The crew of flight 4184

is unaware that a ridge of ice more

than a centimeter high has built up

than a centimeter high has built up

on the surface of their wings.

Eagle flight 184, descend and maintain 8,000.

Eagle flight 184, descend and maintain 8,000.

Down to 8,000, Eagle 184.

The ice buildup has no effect

on the flight until first officer Gagliano begins

on the flight until first officer Gagliano begins

his descent to 8,000 feet.

I knew we'd do that.

I knew we'd do that.

The descent increases the plane's airspeed.

This triggers a warning from the flight computer,

This triggers a warning from the flight computer,

telling the crew they're flying too

fast with the flaps extended.

I was trying to keep it at 180.

I was trying to keep it at 180.

Gagliano now retracts the flaps,

but the routine gesture has a dramatic effect

but the routine gesture has a dramatic effect

on the plane's aerodynamics.

When they retracted the flaps as they started their descent

When they retracted the flaps as they started their descent

down to 8,000 feet, the airplane pitched back up

into a very nose-high attitude.

into a very nose-high attitude.

Airflow over the ice-laden wing

was disrupted when the nose lifted back up.

was disrupted when the nose lifted back up.

That created the turbulence that pulled up the Aillerons,

That created the turbulence that pulled up the Aillerons,

sending the plane into a roll.

The plane stalled, and tumbled from the sky.

Damn!

Damn!

Uh!

Had this crew had about 2,000 to 3,000 more feet of altitude,

Had this crew had about 2,000 to 3,000 more feet of altitude,

there's a high probability that they would have been

able to salvage or recover the airplane

before it struck the ground.

before it struck the ground.

The NTSB has uncovered a deadly flaw

The NTSB has uncovered a deadly flaw

in a popular airplane.

There's a growing concern that unless something is done,

There's a growing concern that unless something is done,

this kind of accident would soon happen again.

this kind of accident would soon happen again.

Investigators conclude that problems

with the ATR's wing design make it vulnerable to this menace.

with the ATR's wing design make it vulnerable to this menace.

The Federal Aviation Administration

takes drastic action.

takes drastic action.

We are going to issue an airworthiness directive

this afternoon that will preclude

this afternoon that will preclude

the operation of these aircraft into known icing conditions.

The FAA takes swift action,

The FAA takes swift action,

banning all models of the aircraft

from flying in icy conditions.

from flying in icy conditions.

This throws regional airlines like American Eagle into chaos.

Public concern over the safety of ATR airplanes

Public concern over the safety of ATR airplanes

grows in the aftermath of the Roselawn crash.

The most controversial charge is that the FAA had relied

The most controversial charge is that the FAA had relied

on the French authorities to test and certify the aircraft,

on the French authorities to test and certify the aircraft,

and then just rubber-stamp their results.

Therefore, the ATR 72 was never really tested by the FAA

in any way, shape, and form, as though it

in any way, shape, and form, as though it

was manufactured here.

The plane's French builder

proposes to fix the problem by making the de-icing boots

proposes to fix the problem by making the de-icing boots

wider so they cover a larger part of the wing.

The company also rewrites operating procedures,

The company also rewrites operating procedures,

forbidding pilots from using the flaps

or flying on autopilot in icing conditions.

or flying on autopilot in icing conditions.

In response, the FAA issues an amendment

to their earlier directive, loosening operating

restrictions on the ATRs.

Most airlines decide not to take any chances.

Most airlines decide not to take any chances.

They move their ATRs to the south, where a warmer climate

They move their ATRs to the south, where a warmer climate

would reduce the risk of ice.

The crash at Roselawn set off a flurry of new research

The crash at Roselawn set off a flurry of new research

into aircraft icing and the conditions that produce it,

resulting in improved aircraft anti-icing

resulting in improved aircraft anti-icing

systems and pilot training.

Upgrades in air traffic control technology,

as well as advances in weather forecasting,

as well as advances in weather forecasting,

satellites and radar, provide improved and critical data.

satellites and radar, provide improved and critical data.

The tragedy in the investigation that followed the crash

of flight 4184 led to industry-wide changes that made

of flight 4184 led to industry-wide changes that made

cold weather flights safer.

There's a lot of weather data out there...

There's a lot of weather data out there...

satellites, radars, surface ops... and it just keeps

satellites, radars, surface ops... and it just keeps

getting bigger and bigger.