Original subtitles

First Officer: Pull up, pull up! Pull up!

Mayday, mayday, mayday!

Captain: No!

[Crash]

Narrator: A turboprop plane slams into a desert

in central Argentina.

Man: 22 fatalities.

My God.

[Speaking Spanish]

Man, Translated: The aircraft was completely destroyed,

burned, and the debris was dispersed

approximately 200 meters.

[Speaking Spanish]

Narrator: Investigators are mystified by what they uncover.

Captain: Pull back harder!

First Officer: I'm trying!

Man: Stop the playback.

Man: And then they drop like a rock.

Narrator: But exploring all possible causes...

Man: Take a look. No failures.

Narrator:...turns up nothing...

Man: There's not a single red flag in his record.

Narrator:...until a single microscopic filament

provides the first clue to solving the case.

[Alarm]

First Officer: What's wrong?

Captain: I don't know!

Flight Attendant: Ladies and gentlemen,

we are starting our approach.

Pilot: We lost both engines!

Flight Attendant: Put the mask over your nose.

Emergency descent.

Pilot: Mayday, mayday!

Flight Attendant: Brace for impact!

Controller: I think I lost one.

Man:...investigation starting into this tragedy...

Man: He's gonna crash!

♪

Narrator: May 18, 2011.

Neuquen, Argentina.

Dispatcher: Okay, gentlemen,

so here's what we're looking at for tonight.

Narrator: Sol Airline's flight dispatcher

is briefing the pilots on tonight's flight

to the port city of Comodoro Rivadavia.

Juan Raffo: So, what have we got?

Any problems along the way?

Dispatcher: Wind, five knots. Visibility, eight kilometers.

Light icing. Nothing unusual.

I've filed a standard cruising altitude of 19,000 feet.

Raffo: Okay.

Dispatcher: Have a good flight, gentlemen.

Adriano Bolatti: We will.

Narrator: Captain Juan Raffo is flying tonight.

He's a seasoned pilot with almost 7,000 flying hours.

First officer Adriano Bolatti has flown with the airline

for six months.

He's monitoring flight instruments

and radio communication.

Raffo: You have plans in Comodoro?

Bolatti: I do, so I'm glad Carlos let me take his shift.

Narrator: Tonight, Bolatti has swapped shifts

with another Sol pilot, Carlos Picinato.

[Carlos Picinato, Translated]: I had been scheduled

to work on that flight,

but the co-pilot had requested to work that flight instead.

The co-pilot and I got along very well.

He was very well versed in the aircraft systems,

maintenance, and mechanics.

[Speaking Spanish]

Flight Attendant: Welcome back. It's been three weeks already?

Narrator: There are 19 passengers

and one flight attendant on tonight's flight.

Picinato: The typical passengers

are people who work in the oil wells,

people who we came to know that traveled with us often,

from Neuquen to Comodoro.

Bolatti: Prop RPM.

Raffo: High.

Bolatti: Trim position?

Raffo: Check.

Bolatti: Anti-ice?

Raffo: As needed.

Air Traffic Controller: SOL Flight 5428,

you are clear for takeoff.

Bolatti: Roger. SOL Flight 5428, clear for takeoff.

♪

V-1. Rotate.

Narrator: At 8:05 PM, SOL Flight 5428 lifts off

from the airport in Neuquen.

Bolatti: Positive rate.

Narrator: The plane will fly directly south

from Neuquen to Comodoro Rivadavia

on the Patagonian coast.

Picinato: The route that we flew in the south

was a regular route.

We usually flew it twice a week.

The landscapes are beautiful.

[Speaking Spanish]

Narrator: Tonight, the pilots are flying

A Swedish-made Saab 340 turboprop.

Sam Stoterau: The Saab 340 is a twin-engine turboprop

typically used for shorter flights

that are connecting to larger hubs.

Picinato: It lends itself to flying easily.

It is a wonderful aircraft to fly.

Raffo: Airspeed 140 knots.

Bolatti: Check.

Raffo: Gear up.

Bolatti: Gear up.

Raffo: Flaps up.

Bolatti: Flaps up.

Raffo: Engage autopilot.

♪

Narrator: The passengers settle in for the 90-minute flight.

Bolatti: Buenos Aires, SOL Flight 5428

reporting waypoint EKOPA.

We are climbing through flight level five-zero

for one-nine-zero.

Controller: ATC Buenos Aires received.

Narrator: First officer Bolatti relays the aircraft's position

to air traffic control.

Bolatti: I hope we don't get in too late.

The guys are waiting for us. Tonight dinner's on them.

Raffo: We'll get there for dinner.

Don't worry.

Narrator: As per their flight plan,

the Saab 340 will climb to a cruising altitude

of 19,000 feet.

Stoterau: When flying propeller aircraft, they do fly lower.

They're not gonna get up

generally much above 25,000 feet,

although occasionally they're certified for higher than that.

♪

Bolatti: It looks like we're picking up some ice.

Stoterau: Oftentimes,

particularly in mountainous terrain,

turboprops will encounter icing conditions.

It's very common, so it's generally not an issue.

Raffo: Nothing to worry about.

We were expecting some light icing.

It should be better when we get to 19,000.

Stoterau: When in icing conditions,

your first objective is to climb above it.

Narrator: At 19,000 feet, water droplets freeze solid,

which keeps them from clinging to the aircraft.

Stoterau: The challenge of flying turboprop airplanes

is to evaluate the weather ahead of time

and really look at the paths of least risk

as it pertains to things like icing and turbulence.

♪

Bolatti: We're building up some ice on my wing.

Narrator: With the icing conditions getting worse,

the captain changes the plan.

Raffo: Okay, let's get it down to where it's warmer

to melt it off.

Ask to descend to a lower altitude. 14,000.

Bolatti: Roger.

Sol flight 5428 requesting descent

to flight level one-four-zero.

Controller: Sol flight 5428,

you are clear to one-four-zero.

Narrator: As Sol 5428 gets to the lower altitude...

Flight Attendant: All finished?

Narrator:...it's proving to be an uneventful flight.

Then, in the cockpit...

Bolatti: You feel that?

Narrator:...the situation suddenly changes.

Raffo: The propeller's vibrating.

Narrator: The pilots feel some vibrations.

It could be a sign of ice building up on the propellers.

Raffo: Put them on max.

Bolatti: Roger.

[Rattling]

Raffo: Ah, hell!

[Alarm]

♪

[Alarm]

Bolatti: What's wrong?

Raffo: I don't know!

[Crash]

[Screaming]

Narrator: The turboprop is suddenly

pitching down and banking.

[Screaming]

Bolatti: Pull back! Pull back!

Raffo: Pull back harder! Bolatti: I'm trying!

Narrator: The pilots struggle to get the plane under control.

Bolatti: Come on.

Raffo: Come on!

Bolatti: We gotta climb! Come on! Come on!

Raffo: Come on!

Come on! Come on!

Narrator: But they can't escape the dive.

Raffo: Come on! Come on! Radio!

Bolatti: Mayday, mayday, mayday!

SOL flight 5428.

Mayday, mayday, mayday!

[Screaming]

No! No! No!

Pull up! Pull up! Pull up! Pull up! Pull up!

Raffo: No!

Automation: Terrain. Pull up!

[Crash]

Narrator: The turboprop crashes and explodes

in a remote region of Patagonia.

News of the accident hits Carlos Picinato especially hard.

He knew both the captain and first officer.

[Speaking Spanish]

Picinato: It was nighttime.

I received a call from a crewmember.

I realized something was wrong.

To get a call at 3:00 am was not normal.

There was just great sorrow for our colleagues.

[Siren]

Narrator: Argentina's civil defense agency

sends emergency crews to the crash site.

But because of its remote location

on a desert plateau in Rio Negro province,

it takes hours for them to arrive.

♪

Pamela Suarez, Translated: The accident took place

in a very complex area of the Argentinean Patagonia.

The cold weather and the mountainous range

made it very difficult for us to have safe land access.

[Speaking Spanish]

Narrator: When the crews do arrive,

they find there are no survivors.

♪

Argentinean investigators examine the crash site

of Sol Flight 5428.

They need clues that might explain

what brought the plane down.

Augusto de Santis: 22 fatalities.

My God.

It's always a shock to have an accident of this magnitude.

One has to set their emotions aside and be professional

and serious about the job one has to perform.

Narrator: Augusto de Santis is coordinating the technical teams

from Argentina's Civil Aviation Accident Investigation Board,

or JIAAC.

De Santis: All right.

Let's start here, work our way out.

Narrator: It's De Santis' job

to determine what brought down SOL Flight 5428,

but it will be challenging.

There is little of the turboprop left to examine.

De Santis: The aircraft was completely destroyed, burned,

and the debris was dispersed approximately 200 meters

from the first point of impact.

[Speaking Spanish]

It doesn't look good.

Narrator: Two key components,

the flight data recorder and cockpit voice recorder,

are found intact,

but they are severely damaged.

De Santis: Okay, let's ship these out and see what we get.

♪

The first thing we did was send the data recorders

and the cockpit recordings to the NTSB in the United States.

Narrator: Next, investigators look for signs

that indicate how the plane hit the ground.

De Santis: It was very complex.

Every accident, every case is absolutely unique.

Most of the debris is in front of the impact point.

The aircraft's initial impact

left a four-to five-meter crater.

That indicates a very hard initial impact.

It must have crashed at a pretty steep angle.

This pattern showed that the aircraft

was out of control when it crashed,

with a great dive angle, which is what caused the crater.

The debris field was relatively small.

[Speaking Spanish]

Catalog every piece, no matter how small.

Narrator: Wreckage is brought to a temporary facility

near the accident site.

Because the crash was so catastrophic,

many of the pieces are almost unrecognizable.

Identifying each and every one is a painstaking process.

The first priority for investigators

is to determine if certain parts of the plane are missing.

A key component like an aileron

detaching from the plane mid-flight

could have caused the crash.

De Santis: So, it's all here?

Okay, then.

Engines.

Narrator: With no evidence of a breakup before the crash,

the investigators focus on the engines.

[Speaking Spanish]

De Santis: We initially tried to evaluate the engine damage

to determine if they were providing power to the aircraft

at the moment of impact.

Narrator: The remains of the turboprop's two engines

are sent for analysis.

Technicians examine their turbines,

looking for the type of damage that would indicate

they were not working when the crash occurred.

De Santis: Both engines presented

A similar damage pattern.

The visible damages, the torsion damage,

led us to think that both engines

were powering the aircraft at the moment of impact.

[Speaking Spanish]

Narrator: Investigators rule out engine failure,

but did some other key component break down in flight?

Horacio Larrosa: Okay, thanks.

Narrator: JIAAC investigator Horacio Larrosa

joins the investigation.

Larrosa: Okay. Let's dig into maintenance.

Narrator: Since the plane hit the ground nose first,

the team wonders if a propeller malfunction

could have brought the plane down.

They dig into the maintenance records.

Larrosa, Translated: As an aeronautical engineer

and manager of the technical research,

the main role was to review the technical documentation.

It says the prop maintenance was incomplete.

Narrator: Investigators have discovered

An airworthiness directive that wasn't carried out.

The order required the base of the propeller blades

to be inspected for cracks.

Larrosa: Hey, I got something.

They missed an inspection.

Narrator: Could a missed crack at the base of the propeller

be the culprit?

Investigators inspect what's left of the propellers

to see if they were working at the time of impact.

De Santis: The prop blades are pretty charred.

Some markings here.

It's tough to say for sure if they were spinning at impact.

Let's see where the propellers ended up.

Based on the position the components were found

and on their condition,

we could check if they had been working or not

at the moment of impact.

Narrator: If an engine's propeller blades

are working at impact,

they are projected away from the crash site.

If they aren't working, they stay near.

De Santis: Left engine prop is here.

Narrator: Investigators discover that the broken propellers

were some distance from the rest of the wreckage.

De Santis: The prop blades are some of the furthest pieces

from the point of impact.

They were spinning.

[Speaking Spanish]

The great distance in which the fragments landed

gives the impression that the propellers

were functioning at impact.

Back to square one.

Narrator: Investigators are no closer to explaining

why Sol Flight 5428 plummeted violently to the ground...

Raffo: No, no, no, no!

[Crash]

Narrator:...killing everyone on board.

De Santis: Okay. Let's add the flight path.

Narrator: Investigators now turn their attention

to the weather conditions on the night Sol 5428 crashed.

De Santis: This is the flight path from Neuquen to Comodoro.

Look what's waiting for them here.

They flew right into this cold front.

The information showed that there was severe icing.

Narrator: Ice on a plane can lead to disaster.

In 1997, Comair Flight 3272 was on approach

to Detroit Metropolitan Airport in near freezing weather...

Automation: Pull up.

Narrator:...when the Embraer turboprop stalled and crashed.

[Crash]

All 29 people on board were killed.

After months of investigation, the cause was finally revealed.

A thin layer of ice had formed on the plane's wings,

causing it to lose lift.

De Santis: Did the pilots know what they were in for?

Narrator: Investigators wonder if the pilots were aware

of the icing conditions

and took the proper steps to protect the plane.

It's something only one person can answer.

Larrosa: You were the flight's dispatcher that night.

Narrator: The airline's flight dispatcher provided the crew

with crucial information.

Picinato: A dispatcher tells you

about the passengers you will have on board,

the amount of fuel you will need

to go from one destination to another,

and they provide you with weather conditions

for the entire route.

[Speaking Spanish]

Larrosa: You didn't know there was severe icy weather?

Dispatcher: I told the pilots to expect only light icing.

Raffo: So, what have we got? Any problems along the way?

Dispatcher: Wind, five knots. Visibility, eight kilometers.

Light icing. Nothing unusual.

Larrosa: Can I take a look

at the meteorological report you gave them?

There you go.

Thank you.

Narrator: Investigators discover the report the flight dispatcher

provided did not indicate the potential for severe icing.

Larrosa: The report you gave them

suggested icing would be mild.

But it was actually severe.

[Speaking Spanish]

De Santis: They had been dispatched with information

that did not indicate this weather condition

and were told that if there was

a possibility of encountering icing,

it would not be severe.

The information in the meteorological report

showed a possible icing situation,

but not as critical as they found it to be.

Larrosa: Where did you get your report?

Narrator: Investigators need to find out

why the dispatcher didn't have the right information.

The team learns that because

the airport's meteorological office closed at 4:00 PM,

the weather report the dispatcher provided

was more than five hours old and no longer accurate.

[Speaking Spanish]

De Santis: The departure airport

did not have a 24-hour meteorological service,

so they departed with a weather forecast

that did not anticipate severe icing.

[Speaking Spanish]

Bolatti: It looks like we're picking up some ice.

Raffo: Nothing to worry about.

We were expecting some light icing.

[Speaking Spanish]

Larrosa: I believe the crew was surprised

by the severe icing conditions.

They were not expecting to find such conditions

during their flight.

[Speaking Spanish]

Narrator: But establishing that the pilots encountered

more severe weather than they expected

is not enough to prove that ice brought down their plane.

In icing conditions, pilots use the plane's anti-ice protection.

On the Saab 340A,

that consists mostly of pneumatic boots made of rubber.

The boots inflate and break up the ice

on the wing's leading edge.

To determine if the anti-icing system was activated

on the night of the crash, investigators examine

a key component recovered from the wreckage,

the Saab's central warning panel.

[Speaking Spanish]

De Santis: It's a panel located at the center of the cockpit

that both pilots can see.

It's composed of a series of light indicators

that warn if there's an abnormality

in any of the plane's systems.

[Speaking Spanish]

Narrator: Investigators analyze tiny filaments

attached to each of the indicators.

When they are lit, electricity is sent through the filaments.

If they were on during impact,

the hot filaments would stretch, not break.

The team discovers a filament is stretched.

♪

De Santis: Ice protection was on.

Narrator: It's a tantalizing lead for investigators.

But did a malfunction of the ice protection

bring down Sol Flight 5428?

Automation: Terrain.

Raffo: Radio!

Bolatti: Sol Flight 5428, Mayday, Mayday, Mayday!

Automation: Pull up.

Narrator: Investigators of Sol Flight 5428 scour the wreckage

for confirmation that a failure in the ice protection system

brought the plane down.

Larrosa: All that survived are the valves.

De Santis: Okay. Let's get them checked out.

Larrosa: Yeah.

♪

Narrator: The primary function of the valves

is to control the flow of pressurized air

that inflates the ice protection boots.

Was there a problem with the valves?

[Speaking Spanish]

De Santis: We isolated the anti-ice valve,

and we analyzed what was left of it.

[Air Hisses]

Narrator: When they test the valve components,

it's discovered that enough pressurized air

was passing through the valves to inflate the boots.

Larrosa: Take a look.

No failures.

[Speaking Spanish]

So, there was no doubt that the systems were being operated

and that they were working.

Narrator: If the pilots knew they were flying in ice

and the ice protection system was working,

then ice alone doesn't explain the accident.

The team has finally received

the flight data recordings from Washington.

This information is crucial

for uncovering the true cause of the crash.

De Santis: Let's see their airspeed.

Larrosa: Okay.

[Speaking Spanish]

De Santis: The information from the recorders was vital

to figuring out a lot of the things that the naked eye

or the elements picked up and analyzed at the crash site

could not reveal.

Okay, look here.

Their airspeed dropped to 129 knots, then 126 knots.

Larrosa: They're in ice.

They should be speeding up, not slowing down.

♪

The cruising altitude is supposed to be 19,000 feet.

Instead, they level out just under 18,000 feet

and slow down to less than 130.

♪

De Santis: The aircraft flight manual

says that when climbing in icing conditions,

the minimum speed is 160 knots.

They're 30 knots below that.

Larrosa: Then they descend to 14,000 feet

and slow again to 138 knots.

And then they drop like a rock.

Narrator: It's immediately obvious to investigators

why the plane crashed.

De Santis: They lost so much speed, they stalled.

The speed was progressively decreasing,

which harmed the aircraft aerodynamically.

[Alarm]

Raffo: Ah, hell!

De Santis: And took it to a final stall and loss of control.

Larrosa: You pick up ice, you should increase your speed.

Pretty basic.

Why didn't these guys do that?

If the speed decreases,

the pilot must increase all power

to try and get out of the situation

to maintain the speed of flight.

De Santis: Let's see their power settings.

Narrator: The investigators need to find out

how the pilots could have let the plane slow

to the point of stalling.

♪

Larrosa: 15,000 feet.

This is where they should start increasing power for the climb.

De Santis: But engine power barely budges.

They don't even have enough power to finish the climb.

Raffo: Nothing to worry about.

We were expecting some light icing.

It should be better when we get to 19,000.

[Speaking Spanish]

De Santis: Once they stabilized on the one-seven-zero level,

which was not the cruising level

that had been planned for this flight,

they did not increase the power.

Instead, they let the aircraft reach that level

and remain there.

Let's check their autopilot settings.

Narrator: The investigators now wonder if the pilots used

the correct setting for the weather conditions they were in.

De Santis: The autopilot selects what the crew needs.

For instance...

The route, the speed, different parameters.

Larrosa: It was set to vertical speed after they leveled off.

Narrator: Vertical speed is one of the autopilot modes

used to gain altitude during flight.

Stoterau: Vertical speed mode is going to allow you

to climb or descend at its pre-determined foot-per-minute,

so if you select 700 foot-per-minute,

it'll climb at 700 foot-per-minute.

Narrator: The purpose is to make climbs and descents faster,

but to do this, the autopilot will maintain

a steep climb angle at the expense of speed.

De Santis: Vertical speed?

Does that make sense?

[Speaking Spanish]

In this flight, we found that the vertical mode was selected,

and we compared this information to the aircraft's manual

on how to fly under these conditions.

Narrator: When investigators dig into the flight manual,

they discover that the autopilot setting the pilots chose

was wrong.

Larrosa: That's their mistake.

Narrator: The pilots should have selected

a different autopilot mode

that maintains airspeed, not rate of climb.

♪

In vertical speed mode,

the autopilot put the aircraft in a higher pitch

in order to maintain the desired rate of ascent.

In icing conditions, that's a problem.

Stoterau: It's gonna expose the whole underside of the wing,

and you're just gonna pack on ice even faster.

Narrator: The situation is made worse

by the lack of anti-ice protection

on the belly of the aircraft.

De Santis: This ice buildup

adds weight on different parts of the aircraft,

which makes it less controllable.

It becomes a major effort for the crew or the autopilot

to control the aircraft.

The performance is not the same.

Narrator: Investigators conclude a heavy buildup of ice

caused the plane to lose speed.

De Santis: The captain had almost 7,000 flight hours,

more than 2,000 on the Saab 340,

and he flew this route often.

He should have had the experience

to handle this situation.

Larrosa: Only 1,300 hours for the first officer,

but there's not a single red flag in his record.

It looks like they both check out.

Narrator: This raises a perplexing question.

Picinato: They were a very qualified cabin crew.

Juan had flown similar aircraft.

The first officer had many hours of experience

in flying under those conditions.

Raffo: It should be better when we get to 19,000.

Narrator: Investigators can't figure out

why two experienced pilots used the wrong autopilot setting

to fly through the icing conditions.

Bolatti: I can put it on vertical.

Raffo: Okay. The sooner, the better.

Bolatti: Roger.

Narrator: Why did the pilots made such a big mistake?

De Santis: Okay, from the top right after takeoff.

Raffo: Airspeed 140 knots.

Bolatti: Check.

Narrator: Investigators hope the cockpit voice recording

of Sol Flight 5428 will shed light

on why the pilots chose the wrong autopilot setting

for the icing conditions.

Raffo: Flaps up.

Engage autopilot.

Narrator: The team wants to know,

were the pilots aware of ice early enough

to prevent a dangerous level of buildup?

De Santis: It was crucial for us to obtain that information.

It was one of the most essential elements

for us to understand what was happening

and also in providing us with information to analyze.

Bolatti: I hope we don't get in too late.

The guys are waiting for us. Tonight dinner's on them.

Raffo: We'll get there for dinner.

De Santis: Initially, what we heard could be said

to be a normal operation.

They had a personal conversation

that had nothing to do with the operation.

So, when did they hit the ice?

Narrator: Investigators listen for confirmation

that the pilots were aware of the icy conditions.

Bolatti: It looks like we're picking up some ice.

De Santis: There it is.

Raffo: Nothing to worry about.

We were expecting some light icing.

Bolatti: I don't know, Juan.

It might be more than we thought.

This ice makes me a bit nervous.

De Santis: He's definitely worried.

[Speaking Spanish]

Larrosa: They were aware that there was ice buildup

and that it was progressing.

Raffo: It should be better when we get to 19,000.

De Santis: They're gonna try and get above the icing.

Larrosa: If they're so worried about the ice,

they should focus on the airspeed.

De Santis: Keep going.

Narrator: Now investigators listen for indications

that the pilots knew their airspeed was a problem.

Raffo: I want it to gain speed.

Bolatti: I can put it on vertical.

Raffo: Okay. The sooner, the better.

Bolatti: Roger.

De Santis: They're covered in ice, losing speed,

and not climbing.

Larrosa: And what do they do? Switch to vertical speed mode.

De Santis: Big mistake.

Narrator: Vertical speed mode actually does the opposite

of what the pilots needed.

It prevents the plane from picking up the speed

they need to stop ice buildup.

[Speaking Spanish]

De Santis: This shocked us a lot

because a person won't make a mistake

because they want to.

This indicates that there was a root problem

that led them to make an inadequate decision

in something as crucial as losing speed

under icing conditions.

Larrosa: They're just focused on getting above the bad weather.

♪

De Santis: They can't.

They're carrying too much ice to climb any higher.

Keep going.

Bolatti: We're building up some ice on my wing.

[Speaking Spanish]

Larrosa: That's when the crew began to observe

the ice buildup on both wings.

Raffo: Okay. Let's get it down to where it's warmer

to melt it off.

Ask to descend to a lower altitude. 14,000.

Bolatti: Roger.

SOL FLIGHT 5428, requesting descent

to flight level one-four-zero.

Larrosa: Go to 14, melt the ice.

Not a bad idea.

Stoterau: Once it became apparent

that they were picking up ice quickly

and they were unable to climb, they make a decision to descend

and reduce the amount of ice accumulation on the airframe

and find an altitude where the temperature was such

that that ice would melt.

♪

Bolatti: I don't think that helped very much.

Narrator: The CVR reveals that conditions

are no less treacherous when the pilots get to 14,000 feet.

Raffo: Ice is hitting everywhere.

Bolatti: Can you imagine how the aircraft's belly is looking?

Raffo: It's okay.

We're gonna stay at this altitude for now.

We'll keep de-icing until we get there.

Narrator: But the pilots can't rely entirely on de-icing.

They also need to push the throttles forward

to increase power.

[Speaking Spanish]

Larrosa: It was noted that while they were aware

of the ice buildup and how things were progressing...

[Speaking Spanish]

...they were not taking strong measures

to change the situation.

[Speaking Spanish]

Bolatti: Feel that?

Raffo: The propeller's vibrating.

De Santis: The first sign of stalling.

Narrator: The turboprop is on the verge

of an aerodynamic stall.

Raffo: It's because there's too much ice on the propellers.

Put them on max.

Bolatti: Roger.

Larrosa: Propellers?

They're misreading the signals from the plane.

They believe that the cause of the vibrations

was that the propellers had too much ice buildup.

Narrator: When an aircraft's propeller

accumulates too much ice,

the plane can begin to shake or buffet.

Increasing the propeller's speed

can be effective in dislodging it.

[Speaking Spanish]

Larrosa: What was actually happening

was a structural vibration of the entire aircraft.

The aircraft was virtually dying.

It was at a speed threshold where the next thing

was the loss of control due to the loss of lift.

[Speaking Spanish]

Bolatti: What's wrong?

Raffo: I don't know!

De Santis: That's the stick shaker.

How do they not realize that they're stalling?

Stoterau: The stick shaker is a device

that actually will shake the control yoke

in order to very viscerally communicate to the pilot

That you have a low-speed event and prompt the pilot to action.

Narrator: But what the investigators hear next

is the most troubling of all.

Raffo: Pull back!

Bolatti: Pull back!

[Alarm]

Automation: Bank angle.

Raffo: Pull back!

Bolatti: Pull back!

Automation: Bank angle.

Narrator: Investigators are surprised

by how the pilots respond when the plane begins to stall.

Raffo: Pull back!

Bolatti: Pull back!

De Santis: They're trying to level the plane.

Larrosa: Unbelievable.

They're making the stall even worse.

Narrator: It's a shocking revelation.

The pilots are doing the exact opposite

of what they should be doing.

Stoterau: When they encountered that stall event,

what they should have done is pushed forward enough

to break that stall and not been so worried

about losing altitude, but rather regaining their airspeed.

Narrator: Investigators suspect the pilots' last-minute attempt

to climb slowed them even more, making the stall unavoidable.

Bolatti: We gotta climb! Come on, come on!

Raffo: Come on! Come on!

Come on!

Bolatti: Mayday, mayday, mayday! SOL flight 5428.

Mayday, mayday, mayday!

De Santis: As soon as they fight the stick shaker,

they're too far gone. They can't recover.

Narrator: Investigators now know why SOL 5428 crashed

into a desert plateau in Patagonia.

De Santis: A wrong autopilot setting here,

a misread of the plane's vibrations here,

and when they finally stall,

they try to pull the nose up to level off

instead of trying to gain speed.

Larrosa: What kind of training did these guys get?

De Santis: We realized that we had to dig deeper

in terms of training,

how the company prepared two people who faced a situation

they could not adequately manage.

Narrator: Investigators pore through

the pilots' training records.

[Knocks]

Larrosa: Yeah?

De Santis: So, this is a regular route

where bad weather is common, right?

Larrosa: Right.

De Santis: Guess what's left out of the training program.

Training on the anti-ice system.

The flight simulator they used couldn't even simulate

flying in icing conditions.

Narrator: It's a stunning discovery.

[Speaking Spanish]

Larrosa: There was only training done

on how to turn on the different systems,

To manage the formation of ice, and how to de-ice the plane,

but no training is done on what to do

once the ice buildup has advanced

and how to get out of that situation by increasing speed.

Narrator: The revelation that the pilots

were not adequately trained to fly in icing conditions

is the last piece of the puzzle in this horrifying crash.

Raffo: It should be better when we get to 19,000.

Narrator: Investigators conclude

the airline's lack of proper training

led directly to the pilots

selecting the wrong autopilot setting...

Bolatti: I can put it on vertical.

Raffo: Okay. The sooner, the better.

Bolatti: Roger.

Narrator:...and to their failure to increase speed

in icing conditions.

[Shaking]

[Alarm]

Raffo: Ah, hell!

Bolatti: What's wrong?

Raffo: I don't know.

Narrator: The result was a stall, which they mishandled...

Raffo: Pull back! Bolatti: Pull back!

Narrator:...by fighting the plane's

stick pusher safety feature.

De Santis: They understood the situation they were in

because they were aware of the ice at all times.

Raffo: Pull back harder!

De Santis: The problem was that the actions they took

were not effective enough in order to mitigate the situation.

Bolatti: Pull up! Pull up! Pull up!

Raffo: No!

[Screaming]

[Alarm]

AAH!

Bolatti: No, no, no, no!

[Crash]

♪

Narrator: In the final report,

Investigators recommend sweeping changes to training

at all levels of commercial aviation in Argentina.

♪

[Speaking Spanish]

Suarez: The most important recommendation

that this accident generated

is about the pilots' training process in emergency situations

and how to handle the aircraft in icing conditions.

[Speaking Spanish]

De Santis: There's a lot of work being done

to prevent this from happening again.

We can't say we'll avoid all accidents,

but our goal is to have the least number of accidents

and the least number of casualties.

That is the most important thing.