Original subtitles

What have we done?

I don't know mate. I don't know.

I don't know mate. I don't know.

The pilots of a turboprop airliner

face a nightmare situation over Papua New Guinea.

face a nightmare situation over Papua New Guinea.

Mayday. Mayday.

Mayday.

Double engine failure.

And we're making an emergency landing.

This crew lose both engines at the same time.

This crew lose both engines at the same time.

There is only really one outcome.

Investigators quickly discover clues in the wreckage.

Landing gear's up.

The flaps are up, too.

The flaps are up, too.

They weren't configured for landing.

Something in the cockpit voice recording...

Something in the cockpit voice recording...

Amplify what's left.

Well, there it is.

...reveals a potentially deadly flaw in an

aircraft used around the world.

aircraft used around the world.

We wanted to make sure that the thousand

aircraft that were out there were operating safely.

Ladies and gentlemen, we are starting our approach.

We lost both engines.

Put the mask over your nose.

- Emergency descent. - Mayday.

- Emergency descent. - Mayday.

Mayday.

Brace for impact.

I think I lost one.

Investigation's started.

Investigation's started.

He's gonna crash.

Airlines PNG Flight 1600 soars 16,000 feet

Airlines PNG Flight 1600 soars 16,000 feet

above Papua New Guinea's Finisterre mountain range.

We're at cruise.

Australian captain Bill Spencer

is an experienced flight commander.

is an experienced flight commander.

Cruise power set.

Campbell Wagstaff from New Zealand

Campbell Wagstaff from New Zealand

is the first officer on today's late afternoon flight.

Both pilots were with PNG for about a year.

The captain had very good experience.

He had about 18,000 hours of flying time.

He had about 18,000 hours of flying time.

The first officer was also very experienced with just shy

of 3,000 hours flying experience himself.

of 3,000 hours flying experience himself.

One flight attendant looks

One flight attendant looks

after the comfort and safety of the 29 passengers on board.

after the comfort and safety of the 29 passengers on board.

Most are parents heading to their children's graduation

at Divine Word University at Madang.

PNG Flight 1600 is midway into a 30 minute

flight to the town of Madang on Papua New Guinea's north coast.

flight to the town of Madang on Papua New Guinea's north coast.

How's the arrival time looking?

17 after the hour.

Right on time.

Right on time.

The pilots are flying manually today because

their autopilot is inoperative.

They're at the controls of a twin engine Bombardier Dash 8,

They're at the controls of a twin engine Bombardier Dash 8,

well suited to carrying passengers

around the Pacific island.

The airplane is able to operate

in and out of short runways, unprepared runways, oftentimes

in and out of short runways, unprepared runways, oftentimes

in smaller communities where the facilities required

to operate a larger passenger aircraft wouldn't be available.

to operate a larger passenger aircraft wouldn't be available.

Two Pratt and Whitney turboprop engines power a plane

Two Pratt and Whitney turboprop engines power a plane

that's nearly 23 years old.

The Dash 8 is one of these airplanes

that's become timeless.

that's become timeless.

It's still operated by airlines all over the world.

As some of the major airlines upgrade their airplanes

As some of the major airlines upgrade their airplanes

to more modern jet aircraft, the Dash 8s

find a new home with other airlines

find a new home with other airlines

because they're always in high demand.

Charlie Bravo nearing Madang.

We're coming through it.

We're coming through it.

You hear that?

Woohoo.

40 miles from Madang, the pilots get

40 miles from Madang, the pilots get

an update on the weather ahead.

A storm is building near their destination.

A storm is building near their destination.

I'll take us around it, all right?

Good idea.

Turboprop aircraft cannot fly as high as a jet airliner can,

Turboprop aircraft cannot fly as high as a jet airliner can,

which means they can't go over a lot of the weather they

may experience on their flight.

may experience on their flight.

Madang Tower, Airlines PNG 1600,

we're diverting slightly to avoid weather.

we're diverting slightly to avoid weather.

PNG 1600, Madang Tower, diverting.

Copy.

Captain Spencer navigates around the storm.

The captain is trying to avoid

clouds, which is normal.

You want to give your passengers a smooth ride.

You want to give your passengers a smooth ride.

But 38 miles from Madang, the crew

still can't see the airfield.

still can't see the airfield.

I'm going to take us down.

Copy.

Copy.

At a major airport, there are typically procedures in place

that we can fly that will bring us through the clouds

and pointed right at the runway.

and pointed right at the runway.

Oftentimes, at more remote airports,

these procedures do not exist so we have to descend

these procedures do not exist so we have to descend

below a layer of clouds.

Once you're below a layer of cloud,

you can visually navigate to an airport

you can visually navigate to an airport

and conduct a safe approach and landing.

and conduct a safe approach and landing.

The crew advises the tower

of their revised flight path.

Madang Tower, PNG 1600, passing 13,000 on descent.

Madang Tower, PNG 1600, passing 13,000 on descent.

Estimated Madang 1-6.

Estimated Madang 1-6.

PNG 1600, Madang Tower, say again your level.

Passing 12,300.

Passing 12,300.

Roger.

Runway 07.

Runway 07.

Rainshowers overhead passing from the east.

Captain Spencer makes a sharp descent

through the clouds.

And the plane picks up too much airspeed.

And the plane picks up too much airspeed.

Aerodynamically, flying

overspeed by a couple of knots is not really a big deal.

overspeed by a couple of knots is not really a big deal.

Think of it like driving a couple of miles per hour

over the speed limit in your car.

Airspeed, mate.

Airspeed, mate.

Got it.

There are several ways to slow down the airplane.

You can increase the pitch of the airplane.

You can increase the pitch of the airplane.

And this will reduce the airspeed as the airplane

aerodynamically slows down.

aerodynamically slows down.

Additionally, you can reduce the power to the engines.

What have we done?

I don't know.

I don't know.

An earsplitting sound makes it almost impossible

An earsplitting sound makes it almost impossible

for the pilots to communicate.

It would be overwhelming.

It would be overwhelming.

There's loud noises that you're not familiar with.

There's smoke.

There's warnings being generated by the airplane.

There's warnings being generated by the airplane.

And it's all happening at once.

It's overspeeds, overspeeds.

It's overspeeds, overspeeds.

It looks like double propeller overspeeds.

First Officer Wagstaff notices the propellers

are rotating too fast.

are rotating too fast.

The plane is in a precarious state.

There could be control difficulties.

There could be control difficulties.

There could be engine damage.

And in severe cases, there could be engine failure.

And in severe cases, there could be engine failure.

What have we done?

It's overspeeding.

Number two is shut down.

Number two is shut down.

I can't hear you.

The crew will have a very difficult time

cutting through the noise and trying

cutting through the noise and trying

to identify the initial root cause of these problems.

Finally, the deafening sound dissipates.

Finally, the deafening sound dissipates.

You get the left side working?

No.

OK.

We got nothing.

We got nothing.

Both engines have failed.

The plane is descending fast.

The plane is descending fast.

This crew was faced with a scenario where

they lose both the primary and the backup system on

they lose both the primary and the backup system on

both engines at the same time.

That backs the crew into a very difficult

That backs the crew into a very difficult

situation where there is only really

one outcome, a forced landing.

A forced landing means the pilots have no choice

A forced landing means the pilots have no choice

but to land immediately.

16 miles from Madang Airport, Captain Spencer

16 miles from Madang Airport, Captain Spencer

turns towards the coastline.

He needs to find a safe place to put the plane down.

He needs to find a safe place to put the plane down.

Tell the tower.

Madang Tower, mayday, mayday, mayday.

Madang Tower, mayday, mayday, mayday.

Airline PNG flight 1600, double engine failure.

And we're making an emergency landing.

And we're making an emergency landing.

Confirm you are able to make it to the field.

The optimum scenario in a forced landing

The optimum scenario in a forced landing

would be gliding to an airport.

Failing that, the next best choice would be landing

Failing that, the next best choice would be landing

close to a town or city.

This may increase the odds that the airport fire rescue

This may increase the odds that the airport fire rescue

services can attend to both the aircraft

and its passengers and crew.

But no such options exist.

But no such options exist.

Brief him that we're going to ditch.

Negative. Negative.

Negative.

Negative.

We'll probably be ditching.

A ditching is a forced landing that

A ditching is a forced landing that

has to be made in open water.

It is the last choice for pilots if an alternative exists.

It is the last choice for pilots if an alternative exists.

Flight 1600 is rapidly losing altitude

and time is running out.

and time is running out.

Look there, a river.

From altitude, a riverbed

may look like a long, safe area to land the airplane

may look like a long, safe area to land the airplane

in a forced landing situation.

I'll get as close to the mouth of that river as I can.

Airlines PNG 1600 will be ditching on a river.

Confirm location.

Confirm location.

Controllers need a location so they can send help.

Not sure the name of the river.

Not sure the name of the river.

The lives of the 32 people on board are at risk.

Pilots will remain focused

right until the very end.

A pilot will not stop fighting to save their airplane.

A pilot will not stop fighting to save their airplane.

Want me to shut both engines down?

Yes.

Shut everything down.

Shutting down the engines prior to a forced

Shutting down the engines prior to a forced

landing off-field could help slow

the spread of any post-crash fire that may develop.

the spread of any post-crash fire that may develop.

Flight 1600 is now a glider.

Flight 1600 is now a glider.

The Dash 8 is only a few hundred feet above the ground.

At a certain point close to the ground,

the pilots have to rely on the decision they've made

the pilots have to rely on the decision they've made

and hope that it was the right one.

Brace.

Brace,

Seconds from touching down,

Seconds from touching down,

Captain Spencer sees a deadly hazard.

Boulders.

All you would have is your eyeballs.

All you would have is your eyeballs.

What you see from 10,000 feet, and 5,000 feet, and 500 feet

What you see from 10,000 feet, and 5,000 feet, and 500 feet

may look different as your depth perception increases

as you're getting closer to the ground.

200 feet from the ground, captain Spencer

200 feet from the ground, captain Spencer

tries to avoid huge boulders on the riverbed.

Brace.

Brace.

Brace.

The only option is the riverbank.

Airlines PNG Flight 1600 has crashed into bush near

the mouth of the Guabe River.

the mouth of the Guabe River.

28 people are dead.

28 people are dead.

Just one passenger and the three member flight crew survive.

There was a dry riverbed so the aircraft

broke up into many parts.

broke up into many parts.

And then there was a post-impact fire, which destroyed

a lot of the evidence.

a lot of the evidence.

The Papua New Guinea Accident Investigation

Commission rushes a team to the scene

Commission rushes a team to the scene

and calls in help from other countries.

I was pretty keen to get the lay of the land

I was pretty keen to get the lay of the land

and see what this accident site looked like

and also get boots on the ground.

and also get boots on the ground.

Eric Blankenstein from the Australian Transport

Safety Bureau is among the first investigators at the scene.

Safety Bureau is among the first investigators at the scene.

My first impressions

were that this was an incredibly large and difficult site

to work.

to work.

And we needed to prepare logistically

to get this job done.

The length and shape of the wreckage field

The length and shape of the wreckage field

indicate how the plane came down.

300 meters long.

It spreads out from the point of impact.

If you have this long distance

and it has this V form and wreckage trail,

and it has this V form and wreckage trail,

it means to us that it's a low angle

of entry and also high speed.

So straight away, we'll be able to get the impression

So straight away, we'll be able to get the impression

that this off-field landing was particularly

fast off-field landing.

Let's see how they configured the plane.

Normally, when you're doing a landing, including an off-field

Normally, when you're doing a landing, including an off-field

landing, you would have the flaps

down so you can effectively land the aircraft slower.

The landing gear configuration also

The landing gear configuration also

you would expect them to be in the down position

to soften that blow of impact.

to soften that blow of impact.

Landing gear's up.

Landing gear's up.

Blankenstein finds the landing gear actuator

in the raised position.

in the raised position.

The flaps are up, too.

They weren't configured for landing.

Without the flaps and landing gear deployed,

Without the flaps and landing gear deployed,

the plane would have hit the ground at high speed.

But what triggered the crisis is a mystery.

But what triggered the crisis is a mystery.

This is the left engine.

The left engine

had separated from its wing and broken into two sections.

Did the turboprop engines play a role?

Did the turboprop engines play a role?

Immediately, my attention

was drawn to some issue to do with the engines,

although we don't try and narrow down our focus too quickly.

although we don't try and narrow down our focus too quickly.

Not a lot of rotational damage to the props.

Not a lot of rotational damage to the props.

They can tell from the condition of the propellers

that very little power was coming from the engines.

that very little power was coming from the engines.

Were the left props feathered?

I'll check.

If an engine fails, the pilots

need to adjust the pitch of the propellers

so they don't create drag.

so they don't create drag.

It's called feathering.

Pilots generally

don't feather propellers of the aircraft

don't feather propellers of the aircraft

unless there's an engine problem.

If you feather a propeller, you no longer have

propulsion to your aircraft.

The left props were feathered.

The left props were feathered.

Did you check the right props?

Yes, they're feathered, too.

Yes, they're feathered, too.

When we identified that the propellers were

both in the feathered position, immediately we

were of the understanding that there was an issue

were of the understanding that there was an issue

with the engines themselves.

We're going to need these airlifted out of here.

We're going to need these airlifted out of here.

I'll arrange it.

We're able to airlift those out

with a helicopter to Madang and then transport the engine

with a helicopter to Madang and then transport the engine

sections to Port Moresby where we

could do a full and thorough examination of those engines

could do a full and thorough examination of those engines

themselves.

I've got the data.

David McNair from the Transportation Safety Board of

David McNair from the Transportation Safety Board of

Canada joins the investigation.

We had the notification from Papua New Guinea

that the Dash 8 had crashed.

Of course, since the aircraft is manufactured in Canada,

that requires our involvement.

that requires our involvement.

Can we hook this up, please?

Can we hook this up, please?

They focus first on the flight

data recorder or FDR.

The information about the engines on site

was limited.

The real evidence you're looking for

is the flight data recorder.

is the flight data recorder.

A lot of these parameters will tell you when the engines

did what and how it happened.

Check this out.

Check this out.

Investigators learned that 28 minutes

into the flight, the rotations per minute

or RPMs spiked to 1,500 on both engines.

or RPMs spiked to 1,500 on both engines.

It's the highest level the FDR can record.

It's the highest level the FDR can record.

Well, that's not normal.

So the normal operation

So the normal operation

of the propeller in the air is about 900 RPM to 1,200.

During the flight, they went above 1,500.

During the flight, they went above 1,500.

Double propeller overspeed.

Investigators discover evidence

Investigators discover evidence

of a frightening engine condition

called a double propeller overspeed.

called a double propeller overspeed.

Overspeeding propellers can destabilize the turbines

and cause catastrophic damage if pilots don't

and cause catastrophic damage if pilots don't

catch the problem soon enough.

You want the engine driving the propeller.

You never want the propeller drag in the engine.

You never want the propeller drag in the engine.

And that condition is where you see this overspeed.

Both engines saw a propeller overspeed condition,

Both engines saw a propeller overspeed condition,

which is extremely rare.

Could the double propeller overspeed have caused

Could the double propeller overspeed have caused

the crash of Flight 1600?

If the engine overspeeds fast enough and hard

If the engine overspeeds fast enough and hard

enough, the parts will break.

And then you don't have control of that engine anymore.

We need a closer look inside those engines.

We need a closer look inside those engines.

Wow.

Look at this.

Look at this.

The turbine blades in Airlines

PNG Flight 1600's left engine provide unmistakable evidence.

PNG Flight 1600's left engine provide unmistakable evidence.

It's corncobbed.

Right.

Right.

Corncobbing occurs when the speed of the propeller

is so fierce that it causes all the blades in the turbines

is so fierce that it causes all the blades in the turbines

to shear off.

The blades physically look like they've

been chewed out of the turbine so it gives a corncob look.

been chewed out of the turbine so it gives a corncob look.

And that's a feature by design that about 145 or 150%

And that's a feature by design that about 145 or 150%

over speed, they shed.

Corncobbing is a protective measure that

Corncobbing is a protective measure that

prevents the turbine blades from spinning quickly enough

to tear the engine apart.

Have a look at the right.

Well, the right looks perfectly OK.

Unlike the left engine,

the right turbine shows no obvious signs

the right turbine shows no obvious signs

of overspeed damage.

The left engine had shed its turbine blades

The left engine had shed its turbine blades

whereas the right had not.

Something completely different happened to the right engine.

Something completely different happened to the right engine.

The right engine was feathered.

But mechanically looking at the turbine itself,

it appeared to be undamaged.

it appeared to be undamaged.

We had assumed that both engines had been damaged

during the overspeed, but clearly

the right engine didn't see as much distress as the left.

the right engine didn't see as much distress as the left.

It certainly raised questions going

forward with the investigation.

forward with the investigation.

I can't figure it out.

Regardless, wouldn't the protective systems

have kicked in?

have kicked in?

Good point.

There are three protections designed to prevent

There are three protections designed to prevent

each engine from overspeeding...

a propeller control unit, an overspeed control

a propeller control unit, an overspeed control

unit, and a backup system.

Both of these propellers going above the maximum so rapidly

Both of these propellers going above the maximum so rapidly

would have to bypass those three systems.

Did the engine protection systems fail?

Did the engine protection systems fail?

As in most investigations, you start

looking at what are the reasons why this was possible.

looking at what are the reasons why this was possible.

Was there a system out there that would

Was there a system out there that would

prevent this from happening?

The answer is yes.

There was a system.

There was a design.

Test results.

Test results.

Investigators analyzed tests

performed on the protection systems for Flight 1600.

performed on the protection systems for Flight 1600.

No data on the right engine.

Inspections of the right engine

Inspections of the right engine

protection systems are inconclusive

due to post-crash fire damage.

The results will have to go to the manufacturer

The results will have to go to the manufacturer

for deeper analysis.

Maybe they can figure out what happened to it.

Maybe they can figure out what happened to it.

What about the left?

The left engine isn't as badly burned and inspections

provide a critical answer.

provide a critical answer.

All three protections were operational.

If the protection systems on the left engine

were working, why didn't they prevent an overspeed

were working, why didn't they prevent an overspeed

and eventual corncobbing?

and eventual corncobbing?

Bypassing three systems of protection at the same time

would be a statistical improbability.

would be a statistical improbability.

So we knew that there was something else involved

in these propeller overspeeds.

in these propeller overspeeds.

Let's see what the pilots have to say about what happened.

Let's see what the pilots have to say about what happened.

The team reviews transcripts of interviews

with the two pilots.

with the two pilots.

You obviously build a list of questions

you want answers to.

What was in your mind's eye at that point in time?

What was in your mind's eye at that point in time?

Were you aware of why the propellers oversped?

What were your actions at the time?

What were your actions at the time?

Captain said there was a lot of cloud cover on approach.

What else?

What else?

I'm going to take us down.

Copy.

Then out of the blue, the air speed warning started to sound.

As Captain Spencer started his descent,

As Captain Spencer started his descent,

a warning sounded, alerting him that the plane

was going too fast.

What did he do?

He said he raised the nose.

He said he raised the nose.

He pulled back on the power.

Sounds right.

Sounds right.

Agreed.

Airspeed, mate.

Got it.

Got it.

If you get a speed warning,

you need to slow down.

The first and most obvious is being to reduce the power.

The first and most obvious is being to reduce the power.

Think of it like taking your foot

off the gas pedal in your car.

off the gas pedal in your car.

The captain's testimony

doesn't provide any new leads for investigators.

doesn't provide any new leads for investigators.

What did the first officer have to say

about the airspeed warning?

Get this.

He says once the warning sounded,

the captain yanked the power levers back quickly.

the captain yanked the power levers back quickly.

First Officer Wagstaff's testimony

adds a crucial detail.

And the co-pilot particularly

indicated that the power levers were brought back very quickly

and then the problem happened right after that.

and then the problem happened right after that.

What have we done?

His instinct to pull the power levers back was correct.

His instinct to pull the power levers back was correct.

But did something happen when he pulled them back quickly?

But did something happen when he pulled them back quickly?

Maybe he pulled them back so fast,

they went all the way into ground beta mode.

they went all the way into ground beta mode.

The power levers on the Dash 8

The power levers on the Dash 8

have two settings, flight mode and ground beta mode,

used only when the plane is on the ground.

used only when the plane is on the ground.

You need a mode where you can taxi

You need a mode where you can taxi

the aircraft and have direct pitch and power control

over the propellers themselves.

It allows you to operate the aircraft

It allows you to operate the aircraft

more simply on the ground.

Pilots are trained not to put the plane into ground

Pilots are trained not to put the plane into ground

mode while airborne.

The only time to be in the ground range

is when you're on the ground, when you're starting

is when you're on the ground, when you're starting

the aircraft, when you're maneuvering the aircraft, when

you're taxiing the aircraft.

If he put the plane in ground mode mid-flight,

would that disarm those overspeed protections?

would that disarm those overspeed protections?

Let's look at the flight manual.

Listen to this.

If pilots put the plane in the ground mode mid-flight,

If pilots put the plane in the ground mode mid-flight,

it would have disabled the protection systems.

it would have disabled the protection systems.

If he's pulled the power levers back rapidly,

If he's pulled the power levers back rapidly,

you're now into No Man's Land.

you're now into No Man's Land.

You're on the precipice of disaster

because you have no propeller control.

So this is a case of pilot error then.

Maybe.

Maybe.

But maybe not.

Don't the power levers have a protective gate between flight

mode and ground mode?

That's correct.

A mechanical stop or gate

prevents pilots from moving the power levers into ground mode

prevents pilots from moving the power levers into ground mode

by mistake.

Triggers on the power lever lift the gate, allowing

movement to ground mode.

You have to physically move your hand

around the front of the power levers

around the front of the power levers

to reach those two small tabs.

And you pull them vertically up.

And then you can move it back but it's certainly nothing you

And then you can move it back but it's certainly nothing you

would want to do in the air.

Investigators need to find

out if the mechanical gate was working

out if the mechanical gate was working

properly on Flight 1600.

Well, it looks like some of the pieces survived the crash.

Well, it looks like some of the pieces survived the crash.

The trigger springs are burned from the post-crash

fire but they're still good.

Did the power lever triggers fail, allowing

Did the power lever triggers fail, allowing

the propellers to overspeed?

The wreckage information was limited.

Quite a bit of stuff was destroyed by the fire.

Quite a bit of stuff was destroyed by the fire.

But the things that there were analyzed.

In this case, one of them was the trigger spring.

In this case, one of them was the trigger spring.

The spring is supposed to hold the power

lever triggers in place.

They still got resistance.

They still got resistance.

The spring was working correctly.

And the triggers were working as designed.

And the triggers were working as designed.

And so we could see that in the inspection.

If the triggers were working, how easy

If the triggers were working, how easy

would it be for the captain to lift them and pull

the lever into ground mode?

the lever into ground mode?

We decided to look at the human factors

We decided to look at the human factors

aspects of the protection system trying to ascertain how

much you needed to lift the triggers to take

much you needed to lift the triggers to take

it below the flight idle gate.

So I ran a test on the levers.

So I ran a test on the levers.

First, I tested the levers to see how well the gate works.

I didn't touch that triggers.

I didn't touch that triggers.

The levers came to a full stop.

The levers came to a full stop.

The gate worked as designed.

Correct.

So then I did it again, this time quickly.

So then I did it again, this time quickly.

Blankenstein simulates the captain's physical reaction

to the airspeed warning.

to the airspeed warning.

Without even trying, I pulled the triggers.

That shouldn't happen.

The team discovers how easily

the pilots could have put the plane into ground mode

the pilots could have put the plane into ground mode

by mistake.

We noted during testing of the power

We noted during testing of the power

levers that if you were moving the power levers back quite

rapidly, we could see how it would be quite

rapidly, we could see how it would be quite

simple to actually inadvertently pull the triggers without even

realizing that you'd done it.

realizing that you'd done it.

The pilots only needed to lift the triggers 6

millimeters for the levers to move past flight

millimeters for the levers to move past flight

idle and into ground mode.

I don't think anybody

who flew the airplane at the time

who flew the airplane at the time

was aware that a 6 millimeter pull of one trigger

could cause both engines to go into propeller overspeed

could cause both engines to go into propeller overspeed

condition.

But did Captain Spencer actually

But did Captain Spencer actually

do what investigators suspect?

We're 4 minutes before they crash.

Let's start.

Investigators listen to the cockpit voice recorder

Investigators listen to the cockpit voice recorder

to confirm their theory, that the captain pulled the power

levers into ground mode.

levers into ground mode.

I'm going to take us down.

CAMPBELL WAGSTAFF Copy.

They hear the captain begin an early descent

They hear the captain begin an early descent

to avoid bad weather.

The cockpit voice recorder records the voices

The cockpit voice recorder records the voices

of the people in the cockpit, but it

also captures all the noises.

And the noises can be very useful for analysis.

And the noises can be very useful for analysis.

Soon after, the airspeed warning sounds.

Soon after, the airspeed warning sounds.

It fits with what the captain told investigators.

CAMPBELL WAGSTAFF (ON RECORDING): Airspeed, mate.

BILL SPENCER (ON RECORDING): Got it.

Whoa.

Whoa.

That is a wall of sound.

That's the sound of the propeller overspeed.

That's the sound of the propeller overspeed.

It's very, very loud

because the propeller tips are breaking the speed of sound.

because the propeller tips are breaking the speed of sound.

And so you get these really, really

high sonic booms back and forth, a lot of vibration,

high sonic booms back and forth, a lot of vibration,

a lot of noise.

Go back 5 seconds.

I thought I heard something before the propeller overspeed.

I thought I heard something before the propeller overspeed.

As they listen to the cockpit conversation...

As they listen to the cockpit conversation...

CAMPBELL WAGSTAFF (ON RECORDING): Airspeed, mate.

BILL SPENCER (ON RECORDING): Got it.

...a tiny sound catches the team's attention.

...a tiny sound catches the team's attention.

Did you hear that?

I heard something.

Hard to tell what exactly.

Hard to tell what exactly.

Can you delete the sound of the props?

Investigators sift through the layers of sound

in the cockpit.

in the cockpit.

Try losing the sound of the alarm as well.

OK.

Amplify what's left.

And let's have a listen.

There it is.

Buried deep within the noise of the cockpit,

they discover what they're looking for.

they discover what they're looking for.

This clicking sound just before the propeller

overspeed was perhaps the pilot in command

overspeed was perhaps the pilot in command

pulling the triggers upwards into the ground beta range.

pulling the triggers upwards into the ground beta range.

Now we're getting somewhere.

Right after the click, they

Right after the click, they

hear another critical sound.

It's the beta warning horn, initially drowned

It's the beta warning horn, initially drowned

out by the overspeed noise.

The beta warning horn

sounds when you take the power levers

sounds when you take the power levers

into the ground beta range.

It was intermittent.

It was intermittent.

And it was very difficult to hear above the sound

of the propellers themselves so we could hear

these little tweeting sounds on the cockpit

these little tweeting sounds on the cockpit

voice recorder that indicate that that was the case.

Airspeed, mate.

Got it.

It's definitive proof that confirms

It's definitive proof that confirms

the investigator's suspicions.

Mid-flight, the captain put the plane into ground mode,

Mid-flight, the captain put the plane into ground mode,

causing the propellers to overspeed.

The flight manual states specifically never to go

The flight manual states specifically never to go

below the flight idle gate.

It's prohibited, a matter of fact.

But if it's so easy to do, how come it hasn't happened before?

But if it's so easy to do, how come it hasn't happened before?

That's a good question.

That's a good question.

Was the crash of Flight 1600

caused by an unlikely pilot error

caused by an unlikely pilot error

or was there a deficiency with the Dash 8 that allowed it?

We need to find out whether we

We need to find out whether we

have a problem with the fleet.

We wanted to make sure that the thousand

aircraft that were out there were operating safely.

Investigators look for evidence of other pilots

who've made the same mistake as the crew of Flight 1600.

who've made the same mistake as the crew of Flight 1600.

Yes?

Yes?

Really?

About two months after the Madang accident,

there was an incident involving a Dash 8 where

there was an incident involving a Dash 8 where

the propellers had overspeed.

Right.

Thanks.

It's happened again.

What's happened?

An incident just like Flight 1600 just a few days ago.

An incident just like Flight 1600 just a few days ago.

The team learns about a crew

in Australia that put Dash 8 into ground mode mid-flight.

in Australia that put Dash 8 into ground mode mid-flight.

In that particular case,

the first officer had the hand on the power levers.

the first officer had the hand on the power levers.

And they experienced an updraft followed by a downdraft

And they experienced an updraft followed by a downdraft

and inadvertently gripped the triggers of the power levers

and moved the power levers below the flight idle gate.

and moved the power levers below the flight idle gate.

Pilots got out of it and put it back into flight

idle right away.

Everyone's fine.

Everyone's fine.

Those are not the only incidents.

Those are not the only incidents.

There are more.

The most recent incident

is just the tip of the iceberg.

Investigators uncover six other cases where Dash 8 pilots

Investigators uncover six other cases where Dash 8 pilots

mismanaged the controls of the Pratt and Whitney engines

by pulling the power levers into ground mode during flight.

by pulling the power levers into ground mode during flight.

It was pretty obvious to us

that inadvertent activation of the power levers

that inadvertent activation of the power levers

into the ground beta range can occur

and will occur in the future.

and will occur in the future.

The NTSB has been on top of this for years.

They wanted stops on the power levers to prevent moving

They wanted stops on the power levers to prevent moving

into ground mode during flight.

What about the FAA?

I asked myself the same question.

They followed suit.

It was mandated.

A lockout system was built for the Dash 8

A lockout system was built for the Dash 8

so this wouldn't happen again.

They fixed the problem?

The design of the system was reviewed.

The design of the system was reviewed.

And there had been many changes as to try and make

this gate less easy to cross.

this gate less easy to cross.

They knew about this 10 years ago.

So why didn't Flight 1600 have this system?

So why didn't Flight 1600 have this system?

Have a look.

This is only in the US.

Exactly.

Exactly.

Dash 8s in the United States had to incorporate a system

that prevented propeller overspeed when you went

that prevented propeller overspeed when you went

into the ground beta range.

And the rest of the world didn't incorporate that system.

And the rest of the world didn't incorporate that system.

If they had mandated this here, it could have saved lives.

Investigators conclude that the power

levers of hundreds of Dash 8s around the world

have a dangerous flaw.

have a dangerous flaw.

But there is one remaining issue to solve.

But there is one remaining issue to solve.

Did we get the results from the manufacturer of what

happened to the right engine?

Even though both engines experienced

the same overspeed forces, why wasn't

the same overspeed forces, why wasn't

the right engine destroyed in the same way the left one was?

- ACTOR AS ERIC - It looks

like the switch that activates the propellers

was improperly maintained.

was improperly maintained.

Shortly after the right propeller oversped,

it got stuck in the feathered position

it got stuck in the feathered position

and was unable to produce any thrust.

It's overspeeding.

It's overspeeding.

So it's effectively in neutral.

It's not in drive.

It's not in drive.

It's not in reverse.

It's just going with the airflow.

This prevented the right engine from corncobbing

This prevented the right engine from corncobbing

like the left one.

It's the final piece of the puzzle.

So Captain Spencer puts the plane in a fast descent.

So Captain Spencer puts the plane in a fast descent.

Investigators finally understand

the sequence of events that caused Flight 1600 to crash.

the sequence of events that caused Flight 1600 to crash.

I'm going to take us down.

Copy.

Copy.

As it heads for Madang,

thick clouds are in the plane's path.

The captain wants to see the airport.

Understandable, but he starts going too fast.

Understandable, but he starts going too fast.

Now around here at 10,500 feet,

the air speed warnings go off.

Airspeed, mate.

Got it.

- ACTOR AS ERIC - He pulls

- ACTOR AS ERIC - He pulls

the power levers back, accidentally putting

the plane in ground mode.

What have we done?

What have we done?

Both engines malfunction

for different reasons.

And the plane is now a glider.

And the plane is now a glider.

It was the worst of cases, the worst of consequences when

It was the worst of cases, the worst of consequences when

you've lost both engines and then you have

to do this off-field landing.

How long did it take for them to hit the ground?

How long did it take for them to hit the ground?

The propellers oversped

here so 4 minutes, 18 seconds.

here so 4 minutes, 18 seconds.

That's not a lot of time for an emergency landing.

That's not a lot of time for an emergency landing.

Madang Tower, mayday, mayday, mayday.

But was that enough time

But was that enough time

to find a safe landing spot?

We needed to know, how

did the crew manage the Flight what could they have done?

did the crew manage the Flight what could they have done?

What did they do?

Investigators examine how

Investigators examine how

the pilots of Airlines PNG Flight 1600

reacted after both their engines failed.

reacted after both their engines failed.

What are they doing?

What have we done?

I don't know, mate.

I don't know.

I don't know.

What were they not doing?

They turn to the transcripts from the cockpit

conversation to see if the pilots

conversation to see if the pilots

followed established procedures in the final 4 minutes

of flight.

of flight.

When you have both engines out,

you're faced with a forced landing.

And there's a checklist for forced landing.

And there's a checklist for forced landing.

Mayday, mayday, mayday.

Airlines PNG Flight 1600, we're making an emergency landing.

Airlines PNG Flight 1600, we're making an emergency landing.

And the typical forced landing checklist

has some basic guidance in terms of what speed they should fly.

has some basic guidance in terms of what speed they should fly.

Reducing speed gives pilots

more time to locate a suitable site

more time to locate a suitable site

and prepare for an emergency landing.

The forced landing checklist would

tell them to lower the flaps and put the gear down

tell them to lower the flaps and put the gear down

once they've chosen the site.

But there's no discussion about the checklist.

But there's no discussion about the checklist.

They weren't running any checklists at all.

They weren't running any checklists at all.

Instead of establishing the airplane

in a best glide configuration, they increased their descent

in a best glide configuration, they increased their descent

rate and sacrificed a lot of the altitude that could

have been advantageous for them in selecting

a forced landing site.

a forced landing site.

Look there, a river.

The crew reacted, but they didn't

The crew reacted, but they didn't

seem to do any sort of problem solving in terms

of what was the best option.

For example, didn't even discuss what speed to fly.

For example, didn't even discuss what speed to fly.

If they configured the plane for a glide,

what speed would they have been flying?

what speed would they have been flying?

Hold on.

The investigators determine the speed

The investigators determine the speed

the pilots could have slowed to in order

to maximize their glide time.

1.3 times stall speed.

1.3 times stall speed.

2.5 miles per 1,000 feet.

2.5 miles per 1,000 feet.

That's 120 knots.

That's 120 knots.

When they compare the glide speed to the actual speed

of the flight, investigators come

of the flight, investigators come

to an eye-opening realization.

They were going up to 250 knots

after propellers oversped.

after propellers oversped.

Twice as fast as they should have been.

How much longer could the pilots

How much longer could the pilots

have stayed airborne if they had maintained

their recommended glide speed?

They could have bought themselves

six more minutes of glide time.

six more minutes of glide time.

That additional time could have come in very handy

for several reasons.

for several reasons.

It would have conserved the energy of the airplane

and allowed them to fly longer.

It also would have given them more time

It also would have given them more time

to perform the appropriate drills and checklists that

would have helped them have a more successful outcome

from the forced landing.

from the forced landing.

I'll get as close to the mouth of that river as I can.

Instead of slowing the plane

and considering all his options, the captain

and considering all his options, the captain

tries to get on the ground as quickly as possible.

Following the overspeed, the rate of descent of the airplane

Following the overspeed, the rate of descent of the airplane

increased from 1,500 feet per minute

to 6,000 feet per minute.

to 6,000 feet per minute.

That's a staggering descent rate.

The last thing that you would want

The last thing that you would want

to do after having lost both your engines

is trade away all of your altitude.

With less time to plan for a ditching,

With less time to plan for a ditching,

the pilots choose a difficult landing site.

Airplanes are designed

Airplanes are designed

to take the structural load of landing

on a firm surface using the systems that we have on board

like landing gear and flaps.

like landing gear and flaps.

The systems aren't designed in a conventional airplane

to land on water.

to land on water.

Boulders.

In the end, boulders prevented any chance

of ditching on water.

of ditching on water.

Forced to land on the riverbank, PNG

Flight 1600 wasn't properly configured

Flight 1600 wasn't properly configured

for landing on the ground.

So many people died on this accident.

So many people died on this accident.

This was an eye-opener and made everybody realize,

in fact, something had to be done to prevent

in fact, something had to be done to prevent

this kind of situation.

The investigation into the crash

of Airlines PNG Flight 1600 concludes

of Airlines PNG Flight 1600 concludes

with a clear recommendation.

You can't just say pilot error and be done with it.

You can't just say pilot error and be done with it.

You have to say why was the error possible.

Why wasn't the error eliminated?

In this case, it's the design of the airplane.

In this case, it's the design of the airplane.

A system safeguard required in the United States

A system safeguard required in the United States

was not mandated elsewhere in the world.

We had enough evidence

to be able to force change.

to be able to force change.

We used the power of the pen and the facts and the evidence

that we had identifying safety issues.

that we had identifying safety issues.

And we presented that to the manufacturer

and Transport Canada.

And they did change.

It was always a good airplane,

but now we've had to make the system

so that purposeful act or unintentional act is now safer.

so that purposeful act or unintentional act is now safer.

so that purposeful act or unintentional act is now safer.

I mean you can't do it anymore if you wanted to.

So in this particular case,

we were able to really get down to what had occurred

we were able to really get down to what had occurred

and make those safety improvements.

And as an investigator, that's all you can ask for.

And as an investigator, that's all you can ask for.

It's why we do the work that we do.

We just want to improve the system

and ultimately save lives in the future.