Original subtitles

Halloween, 1994.

You haven't heard anymore from this controller chick, huh?

No, not a word.

A commuter plane circles outside Chicago, waiting for clearance to land.

Eagle Flight 184, descend and maintain 8000.

Maintain 8000. Eagle 184.

Without warning, the controls snap to the right.

The plane plunges straight for the ground.

The behavior of the crew and the air traffic controllers would be examined.

Pilots would question the safety of an airplane.

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.

Mayday! Mayday!

It's mid afternoon on October the 31st, 1994.

American Eagle Flight 4184 left Indianapolis, Indiana, 15 minutes ago.

It's heading to Chicago.

There are 68 passengers and crew on board.

- Happy Halloween Cowboy. - Thank you.

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.

Captain Orlando Aguiar is in command of today's flight.

It's supposed to be his day off.

He volunteered for this flight to make extra money.

His wife is expecting their second child.

Let's see if we can get above this.

Center any chance Flight 184 can climb to 16,000?

Eagle Flight 184 maintain 16,000.

First Officer Jeff Gagliano is handling the flying duties

on this leg of the flight.

He programs the autopilot to climb to a less turbulent altitude.

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

uh, just before he came in for that trip on, uh, 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.

Cost efficient and comfortable, the plane has become popular on short runs.

This flight is just one of five short hops the crew will be making today.

It's Amanda Holberg's first day on the job

as a flight attendant with American Eagle.

She's paired with Sandi Modaff, a seasoned veteran.

Aguiar and Gagliano have flown this route countless times and know it by heart.

When you're flying from Indianapolis to Chicago,

you're flying through some of the busiest, uh, airspace in the world.

As Flight 4184 approaches Chicago O'Hare,

the pilots begin the descent to 10,000 feet.

Chicago center. We have discretion down to uh, 10,000.

We're on our way down now.

Eagle 184, roger.

In Chicago, Controller Michelle Willman is returning from a break

The trainee controller is still working under the supervision of a monitor.

She's told that traffic into O'Hare

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 are handled on a priority basis.

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

Um, international flights arriving to O'Hare

because of their fuel status get priority.

And then the turbo props come in at the end.

Eagle 184, hold southeast on Victor seven.

Chicago Center, roger hold southeast on Victor seven. Eagle 184.

Flight 4184 must now fly a racetrack shaped holding pattern

over northwestern Indiana.

Chicago Center, Eagle 184 entering the hold.

Eagle 184, roger.

Aguiar programs the Autopilot to keep the planes circling at 10, 000 feet.

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

The crew has little to do as they wait for Air Traffic Controllers

to give them permission to land.

- Can I get you boys anything? - I'm good.

Stereo, you don't have a hard job.

We do have it pretty easy.

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

- Yeah. - We're just wallowing in the air right now.

You want flaps 15?

- I'll bring the nose down. - Sure.

I guess Sandi's going ooh now.

- See y'all. - All right.

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 with dispatchers

so they don't tie up radio frequencies.

Should I let 'em know how much fuel we got?

Sure.

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

We've got uh, 3600 pounds.

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 at this time.

I do apologize for all the delays.

That's much nicer,

flaps 15.

I'm sure once they let us out of the hold and forget they're down,

we'll get the overspeed warning.

I can't hold anymore, man.

I'm doing circles up here, yeah.

We got plenty of gas. We could be up here for a long while.

- Hey, bro. - Yeah.

I'm getting busy with the ladies back here.

Ooh.

Yeah, so if I don't make it up there in the next say, 15 or 20 minutes,

you know why.

Ok, I'll uh, when we get close to touchdown, I'll give you a ring.

Oh, nah, I'll be up right now.

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

No, not a word.

Eagle Flight 184 descend and maintain 8000.

Down to 8000. Eagle Flight 184.

Eagle Flight 184 uh, should be about 10 minutes

uh, till you're cleared in.

Thank you.

The flight is allowed to descend.

Are we out of the hold?

No, we're just going down to 8000.

Then a warning.

I knew we'd do that.

The plane is going too fast to fly with its flaps extended.

Well, I was trying to keep it at 180.

Galliano retracts the flaps.

There's a strange sound coming through the fuselage.

Suddenly, the control column turns sharply to the right.

The controls won't budge.

The plane is falling from the sky.

The pilots begin to recover control.

But then it happens again.

Mellow it out, mellow it out!

Terrain. Pull Up.

- Terrain. Doesn't pull.

Terrain. Pull Up. Terrain. Pull Up.

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

It was coming down at a, I mean, a sharp angle, a real sharp angle.

Flight 4184 has crashed into a field

just outside Roselawn, Indiana.

Oh my God they're dead, they have to be

for the speed that it was coming down.

Hundreds of volunteers arrive at the crash site to offer help.

But there's nothing they can do.

There was not much to see of any airplane, you, you couldn't see no,

no cabin or anything of the airplane,

there just wasn't anything left of it.

Both pilots, the two flight attendants and all 64 passengers are dead.

The Roselawn crash would soon become

one of the most important accidents in aviation history.

It will lead investigators to new conclusions about a string of older crashes.

The morning after the crash of American Eagle Flight 4184,

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, it was overcast, It was one of those drizzly, dank days.

All you could smell was the Jet-A or the kerosene fuel

and because it was muddy and wet, 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.

And now you have to walk through that field and actually start to do your job.

The crash site is soaked in jet fuel and hydraulic fluid.

Human remains are scattered everywhere.

The site is declared a bio hazard.

With 4184, it was one of those types of accidents

where there was very little left of the airplane.

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,

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.

They're taken to the NTSB labs for analysis.

The data on the recorders could provide the clues

investigators need to solve the mystery.

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 corners of the airplane.

The NTSB's Bob Swaim leads that search.

You're looking for the nose and the tail and the two wing tips,

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.

The plane's four corners are far 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.

Mellow it out, mellow it out!

The fact that the plane wasn't in a steep descent 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 its Attitude Director Indicator.

Also known 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 and caused them to make mistakes.

We had a pretty good idea of the attitude of the airplane at impact,

so it would really help at that point to see if the pilots

had the same view of the flight that we found as they hit the ground.

Can you get the lights for me please?

A lot of the cockpit pieces use a fluorescent paint, or something similar,

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 that the naked eye cannot see.

There's a good imprint here.

The force of the impact has left tiny scratches

on the shattered instrument.

Swaim discovers that the attitude indicator seems to have been working.

Its final readings show the plane was leveling off.

The instrument coincides with the plane's actual position on impact.

It indicated that at least the flight instruments

that the pilots would have been looking at were appropriate,

they were proper, that the pilots had something to fly by.

The discovery means that the pilots knew their plane was diving towards the ground.

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 before it fell from the sky.

One of the elements of the investigation, of course,

was to look at Air Traffic Control.

Eagle 184 hold southeast...

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,

we found that the flow rate,

that is 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 that Air Traffic Control

has put us into a holding pattern up here.

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.

I do apologize for all the delays.

One of the aspects that we found was that one of the controllers

in the facility was relatively new, they were considered a trainee.

Had an inexperienced controller put Flight 4184 in peril?

Chief investigator Greg Feith wants to know more about the weather conditions

along the holding pattern.

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.

Several other planes were also on hold.

They all landed safely.

Interviews with the pilots of some of those planes

give investigators an important clue.

One after another,

they all experienced icing, some as much as three quarters of an inch.

Many of the pilots report the same thing.

Ice.

Dr. Marcia Politovich works at the National Center for Atmospheric Research.

She's one of the leading experts on icing, and the danger it poses to aircraft

It essentially changes the shape of the wing while you're in flight.

It creates drag, it reduces lift,

it causes performance and handling problems

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

Investigators examine weather records from the day of the crash.

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.

Perhaps the size of the commuter plane was a factor in this crash.

Different planes respond to icing differently.

A large plane will respond differently than a small plane.

Uh, reasons for that are both environmental and having to do with the airframe itself.

Large jets generally fly above the dangerous conditions inside a cloud.

But the ATR-72 can't do that.

A smaller plane can't fly as high.

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.

Investigators discover that Flight 4184's holding pattern

took it through layers of cloud repeatedly.

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 have been flying in and out of.

Steve Frederick was flying out of Chicago on the morning of the crash.

He flew through the same treacherous weather.

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 more and more concerned.

Frederick asked his captain 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 that my captain had never warned dispatch

and these pilots never got the warning about the ice 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.

Greg Feith knows that controllers had put several other planes

into a holding pattern near Chicago.

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

This means the controller had not put Flight 4184 in jeopardy.

She acted correctly, given the information she had about the weather.

One of the issues about Air Traffic Control

is that 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 conditions

unless the pilot provides them

with what they call a Pirep or a Pilot Report.

So if, 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.

Feith and his team wonder if the flight crew simply didn't realize

they were flying into icy conditions.

The plane's cockpit voice recorder provides the answer.

Can I get you boys anything?

Stereo, you don't have a hard job.

We have it pretty easy.

Hey, bro.

I'm getting busy with the ladies back here.

Ooh.

At first glance, the crew's behavior seems unprofessional

and undisciplined.

The first officer was listening to some music.

We knew that there were a lot of non-aviation things going on.

One of the most contentious elements was how did that affect the crew's performance

and their awareness to the situation that was starting to develop.

That's much nicer now,

flaps 15.

Showing some ice now.

I'm sure once they 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 pilots must have been aware they were flying through an area of aircraft icing.

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

No, not a word.

Then, two minutes before the accident,

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.

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's data recorder provides the answers.

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 also mean the electronic ice detector

is picking up the presence of ice.

The flight data recorder shows investigators that in response to the alert,

Captain Aguiar turned the plane's de-icing system to its maximum setting.

The NTSB's Charley Pereira looks into the performance of the ATR-72.

The icing, uh, alert system had sounded aurally and they heard it,

and they activated protection systems on the airplane,

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

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 don't allow the ice to form.

The windshields and the propellers are also heated on this airplane

and then they have de-ice systems which are on the leading edge

of the wings, what you call pneumatic boots.

Uh, they're like rubber inflatable chambers that you blow air into

and they expand kind of like a balloon and that cracks the ice

and the ice flies off the airplane.

The flight data recorder shows

that after he activated his de-icing system, Captain Aguiar,

also pushed the throttle forward slightly,

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.

The pilots had done everything they could to deal with ice buildup on the plane.

But were the anti-icing systems actually working?

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.

The de-icing system was part of that design.

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.

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 is probably not

the black rubber boot that you see on the airplane,

but the timer that's inside the airplane, or the timers

in the valves that control those boots.

The force of the crash has left telltale markings called index marks.

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

Swain compares them to the original blueprints.

Does anything seem out of the ordinary?

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

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 wings

and their de-icing system was working,

why did the plane crash?

Other pilots think they know the answer and decide to speak out.

Their decision will dramatically change the course of this investigation.

Three weeks after the crash near Roselawn, Indiana,

American Eagle pilot Steve Frederick distributes a warning.

It says the ATR-72 fleet operated by American Eagle,

is dangerous in icing conditions.

It claims American Eagle pilots have pleaded with the airline

and regulators to do something about it, but to no effect.

I drafted and, 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

in order to try and get something done because nothing was happening.

Steve Frederick has more than a professional interest

in the crash of Flight 4184.

Co-pilot Jeff Gagliano was his close friend.

They graduated from flight school together.

Galliano's death has hit him hard.

He made the comment one time

that he would probably wind up dying because of ice in an ATR.

And it was eerily prophetic.

A month after the crash.

Pilot frustration over the ATR's airworthiness boils over.

A group of a dozen pilots refused to fly, citing risky weather.

The airline is forced to cancel flights

and then Steve Frederick goes one step further.

He voices his concerns on a US Network 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.

When I came back to flying after my appearance on Good Morning America

I was summarily suspended without pay.

The public protest leads investigators to wonder

if the ATR-72 has a deadly vulnerability to ice.

Merci.

Investigator Charley Pereira

visits the ATR's French manufacturer Aerospatiale

to learn more about the plane's history.

We embarked on a research effort to try to identify

all previous ATR-42 and 72 uh, roll control uh, incidents.

He finds a disturbing pattern.

And, and about 5, 5 of those were found to be similar,

uh, after the fact in our review to the Roselawn case.

One such incident took place in December 1988

in Mosinee, Wisconsin.

An American Eagle ATR-42 had been preparing

to land in icy conditions at Central Wisconsin airport.

The airplane was on approach

uh, in severe icing conditions

um, described as freezing drizzle and freezing rain.

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 uh, we were doing our descent.

um, everything was proceeding normally.

Negative ice, just wet.

I'll call the flight Center to let them know we're turning inbound.

I hear in the tail a sound like that.

It just got louder and louder.

We have no idea what is occurring.

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.

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 all the way.

The engines are really trying to fly.

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, "terrain, terrain"

and I don't have the airplane back yet

and my first officer says...

Props.

And I say, "max rpm."

Terrain. Terrain.

And he throws the props from 86 to 100 percent.

And instantaneously boom, we fly out of the stall.

Whoo!

The plane is less than 1200 feet above the ground.

Captain Bodak has learned a sobering lesson about the ATR.

There was no warning.

The plane stalled without any warning.

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.

An ATR-42 operated by an Italian airline

was flying over the Alps enroute to Germany in October 1987.

The plane lost control and crashed in the mountains,

killing all 37 people onboard.

Ice was the main factor.

But the final report blamed pilot procedures.

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 with this plane's history.

Did any of your studies uncover a wing design flaw?

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.

To his surprise, he learns they knew that it had a susceptibility to icing.

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

Where would 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

of an ice accretion that could cause uh, the behavior that we saw

on the flight recorder for the Roselawn airplane.

He drew up the airfoil section and a little shape

just behind the de-ice boots and said this was it,

and the translation was that this is what will cause the problem.

Aft of the de-icing boot.

Investigator Charley Pereira's beginning to understand how ice can affect

the wings of the French-built plane.

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

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 buildup behind the boot?

Investigators contact Dr Marcia Politovich for assistance.

The NTSB called us uh, to help them analyze

weather conditions in this case.

Her research shows that the pilots of Flight 4184

likely flew into something they've never even heard of.

Something even more dangerous than ordinary ice.

Now based on the weather analysis, it looked to us

like the kind of icing that plane encountered

was from super-cooled large drops.

Now large is relative,

what we're talking about large here is about the size of a human hair.

Super-cooled large droplets

are about 100 times smaller than a raindrop.

They form inside storm clouds when the temperature is near freezing.

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.

We had all the clues that we needed.

A warm cloud top, minus eight to minus 12 degree Celsius.

We had drizzle formation near the top that was probably encouraged by some wind shear

near the cloud top.

And very little ice in the cloud

from what we could tell.

On every lap of its holding pattern

Flight 4184 flew through layers of clouds that hid a small but lethal element.

They just put that poor guy in the wrong place at the wrong time.

Investigators learn that super-cooled large droplets

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.

But SLD act differently.

These super-cooled drops hit the wing and slide back over it before freezing.

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,

rather than the water droplet freezing on the protected surface

of 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 from the cockpit.

They would have been utterly unaware of the danger taking shape.

For the pilots, when they looked out their side window,

they would see the outer portion of the wing.

They definitely could not see the top of the wing,

where this ice ridge was starting to form.

For Greg Feith, the investigation is coming to a head.

His investigators think they know why Flight 4184 crashed,

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 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 their particular product.

Feith wants to know if there had been

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

He finds troubling similarities

between some incidents dating back decades.

Using data from flight data recorders,

investigators look at aileron movements from Flight 4184

and compare them to the other incidents.

They discover that on all those flights

the aileron deflected in exactly the same way.

There's no input at all from the pilots.

We knew that all of these ailerons 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.

The physics of ice buildup explains

why the control column on Flight 4184 snapped to the right

Air turbulence on the wing was so powerful

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

Since the aileron is attached to the control column by a cable,

it jerked the control yoke to the right.

The force of the turbulence pulling on the aileron was so great,

that even two pilots trying to counter steer

weren't able to bring the aileron back down.

The forces were determined to be about 250 pounds.

So for the pilot, it would have been trying

to roll against 250 pounds of aerodynamic force.

Worse, the ATR's control yoke doesn't have power steering,

so those forces are transmitted directly to the pilots.

The pilots could not fight back against the air pulling on their aileron

For chief investigator Greg Feith,

super-cooled water droplets that left a ridge of ice

on the wings are now the prime suspect.

But how to prove it?

Now, the real analysis began because we had to understand

what was going on in-flight with the airplane.

We had good flight, data recorder information.

It only told us what happened,

it didn't tell us why it happened.

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 super-cooled large droplets on airplanes.

Back in 1994 pilots didn't know what SLD

or super-cooled 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.

Investigators first turn to NASA for help.

Together they launch a daring experiment.

They use a US Air Force tanker plane

to create a cloud of super-cooled water droplets.

An ATR-72 flies behind the tanker.

Yellow dye in the water shows investigators

how the droplets cover the plane.

The test should solve the final mystery.

How had ice caused Flight 4184 to go so badly out of control?

One of the primary purpose this is applying the ATR-72

in behind the tanker was to understand

how the ice accumulated on the airplane.

But more importantly, the effect of that ice

in varying configurations of the airplane,

on the flight control surfaces, that is the ailerons.

Investigators make a startling discovery.

A seemingly harmless action meant to increase comfort on the plane

may have led to disaster.

- Can I get you boys anything? - I'm good.

While American Eagle Flight 4184

was holding, Captain Orlando Aguiar notices

that the nose is tipped quite high.

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

Yeah.

Captain Aguiar knows that the plane's high nose angle

was producing an uncomfortable tilt in the passenger cabin.

You want flaps 15?

- It'll bring the nose down. - Sure.

Extending the flaps would have the effect of lowering the plane's nose,

making the ride more comfortable.

I guess Sandi's going ooh now.

When investigators duplicated this maneuver,

they found that it had a dramatic effect

on where the ice reach formed on the plane's wing.

the flaps made the icing problem even worse.

by exposing more of the upper surface of the wing

to the oncoming water droplets

and that's one of the reasons why we got um, the ridge of ice

where we got it was because of the flaps 15 configuration.

That's much nicer now,

flaps 15.

The crew of Flight 4184

is unaware that a ridge of ice more than a centimeter high

has built up on the surface of their wings.

Eagle Flight 184 descend and maintain 8000.

Down to 8000. Eagle Flight 184.

The ice buildup has no effect on the flight

until First Officer Gagliano begins his descent to 8000 feet.

I knew we'd do that.

The descent increases the plane's airspeed.

This triggers a warning from the flight computer,

telling the crew they're flying too fast with the flaps extended.

Well, I was trying to keep it at 180.

Gagliano now retracts the flaps.

But the routine gesture has a dramatic effect on the plane's aerodynamics.

When they retracted the flaps as they started their descent down to 8000 feet,

the airplane pitched back up into a very nose-high attitude.

Airflow over the ice-laden wing was disrupted

when those lifted back up.

That created the turbulence that pulled up the ailerons,

sending the plane into a roll.

The plane stalled, and tumbled from the sky.

Damn.

Had this crew had about two to 3000 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.

The NTSB has uncovered a deadly flaw in a popular airplane.

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

this kind of accident would soon happen again.

Investigators conclude that problems with the ATR's wind design

make it vulnerable to this menace.

The agency that regulates US aviation takes drastic action.

We are going to issue an Air Worthiness Directive this afternoon,

that will preclude the operation of these aircraft

into known icing conditions.

The FAA takes swift action

banning all models of the aircraft from flying in icy conditions.

This throws regional airlines like American Eagle into chaos.

Public concern over the safety of ATR airplanes grows

in the aftermath of the Roselawn crash.

The most controversial charge,

that the FAA had relied on the French authorities

to test and certify the aircraft then rubber-stamped the results.

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

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 wider,

so they cover a larger part of the wing.

The company also rewrites

operating procedures, forbidding pilots from using the flaps

or flying on autopilot in icing conditions.

In response, the FAA issues an amendment to their earlier directive,

loosening operating restrictions on the ATR's.

Most airlines decide not to take any chances.

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

into aircraft icing and the conditions that produce it.

There's a lot of weather data out there.

Satellites, radars, surface ops,

and it just keeps getting bigger and bigger

the collection of data.

New techniques in forecasting are being developed

to show pilots where icing is likely to occur

and help them avoid it.

But we're working on ways to get it to the people who need it.

Uh, dispatcher at airlines,

um, meteorologists at airlines.

And now even into the cockpit itself.

Many of those changes will take time to come into effect.

Pilots like Steve Frederick think that time will cost lives.

The problem that exists is that there is no technology available today

to the pilots or anyone on the ground to accurately forecast or predict

where these situations of bad ice are going to occur.

Once these airplanes have been exposed to the bad ice,

it's too late because these are no longer airline pilots,

they're test pilots.

And that airplane can fall out from under them and their passengers

without any warning and in the blink of an eye.