Original subtitles

(plane droning) (rattling)

A New Year's Eve tragedy.

REPORTER (over TV): A seaplane with six onboard lost control.

BOSWORTH: This is big news.

NARRATOR: A multi-millionaire and his family are killed.

Initial reports about the crash site are puzzling.

He's not where he's supposed to be.

NARRATOR: Investigators quickly gather witness statements...

WITNESS: It took off normally, like any other flight.

(beeping)

NARRATOR: And scrutinize the pilot's background.

This guy was a competent pilot.

NARRATOR: With no significant clues, the team turns to recovered wreckage.

We had a completely functional aircraft at the time of impact.

NARRATOR: But something buried deep inside the plane

provides investigators with their biggest lead.

CAMPBELL: This was in the cabin.

I felt we may have an answer in our grasp.

(dramatic music)

PILOT (over radio): Mayday, mayday!

GPWS: Pull up!

(radio chatter)

NARRATOR: Five British tourists have started celebrating New Year's Eve

at a waterside restaurant at Cottage Point, Australia.

- And how was lunch? - Oh. It was great.

NARRATOR: Gareth Morgan is the pilot

for the 20-minute flight back to Sydney Harbor.

Have you enjoyed your Australian visit so far?

Very much.

Take the front seat. You'll get some good shots from up there.

NARRATOR: A born athlete raised in Vancouver, Canada,

Gareth Morgan has come to Australia to fly floatplanes.

GARETH: My dad's friend, he owned an airplane, got me hooked.

So, you know, I just thought, hey, this looks like a great career.

Gareth did not like to be bored.

He liked to be challenged and have variety in his life.

And a pilot's career, particularly a pilot on float planes,

gave that to him in spades.

NARRATOR: Richard Cousins is the CEO

of one of the largest food companies in the UK.

He's on holiday with his fiancée, her daughter, and his two sons.

Buckled in?

(engine starts)

NARRATOR: The trip to Cottage Point attracts a high-end crowd:

celebrities, business tycoons, and even close relatives of the Royal Family.

Seven months ago, Pippa Middleton, the sister of the Duchess of Cambridge,

and her husband, James Matthews,

took the same trip during their honeymoon in Australia.

(miked) Well, welcome back folks. Pleasure having you on board with me again.

(engine rumbles)

NARRATOR: The flight is operated by Sydney Seaplanes,

which runs a small fleet of agile floatplanes.

Today, Gareth Morgan is flying a de Havilland Beaver.

QUINN: It's a very gentle, easy, relaxed airplane to fly.

I call it the big comfy couch.

You can take large payloads. You can get into tight places, confined areas.

It's very versatile. (plane drones)

NARRATOR: The Beaver is powered by a single 450 horsepower radial engine.

The iconic aircraft is at work all over the world.

We're about ready for takeoff here, folks.

I went over the safety regulations on the way over. Does anyone need a refresher?

All good.

GARETH: We'll have you back in Sydney in a flash.

NARRATOR: Morgan takes the plane towards the designated take off area

in Cowan Creek.

You're deciding, "Okay, where are the hazards? Where are my obstacles?"

"Which direction is the wind coming from?" You're considering all those variables.

Cowan Creek Traffic, this is Float Beaver November Oscar Oscar.

We are taxiing to the takeoff point for a northeast departure to Rose Bay.

QUINN: Most locations where a float plane is operating,

you're in uncontrolled airspace, so you're not talking to a controller.

You are just making blind calls on the radio

to tell other aircraft what your intentions are in the area.

Any conflicting traffic, please advise. November Oscar Oscar.

NARRATOR: Traffic is clear. They can depart.

A takeoff on water is executed in two stages.

You're gonna be ploughing through the water

until it kind of crests over that bow wave that you're creating with the floats.

(propeller rumbles)

(dramatic music)

Once you're on that step, you're watching your attitude,

keeping your directional control with your rudder and your ailerons.

NARRATOR: Racing at 60 miles per hour,

the floatplane takes only 15 seconds to lift off.

(plane drones)

GARETH: You'll see Cowan Point down there.

NARRATOR: In the moments after takeoff, the plane must gain altitude quickly.

(plane drones)

The hills surrounding the bay are more than 400 feet high.

QUINN: What makes it different for pilots flying these kind of aircraft

is just being open to constant changes.

The variables are always changing.

NARRATOR: Gareth Morgan has to decide the best way to gain the altitude he needs

to clear the surrounding hills.

He can continue forward, climbing along the length of the channel.

He can also make a U-turn

and head back over the waterway from where he just took off.

QUINN: A pilot chooses their departure path based on experience,

knowledge of the area, comfort level with the aircraft.

Typically, you want to go out into the most open area possible.

NARRATOR: For the pilot, this is the eighth flight

during a busy day shuttling passengers.

(plane drones)

GARETH: That there's Cowan... um... Comox Creek.

Say again?

There's Comox Creek.

Oh.

(tense music)

NARRATOR: At just 130 feet, the floatplane stops climbing.

GARETH: I gotta... um...

NARRATOR: Morgan needs to gain altitude. He's headed towards a dead end.

QUINN: You have to have a point of making a decision.

(plane drones)

Can I make it or can I not make it?

And if you cannot make it, do you have the space to get out of that situation?

(rattling)

(engine droning)

NARRATOR: Less than two minutes after taking off from Cottage Point...

(plane drones)

The floatplane crashes into Jerusalem Bay and sinks.

ANCHOR (over TV): A New Year's Eve tragedy.

Six people feared dead in a seaplane crash on the Hawkesbury River.

By the time rescuers arrived on scene, the aircraft had disappeared under the water.

This is big news.

NARRATOR: Investigators from the ATSB, the Australian Transport Safety Bureau,

begin their first assignment of the new year.

I'll handle the press. Try to find some witnesses.

Someone must have seen this.

(newscaster speaks indistinctly)

BOSWORTH: The media attention was huge.

It was on every television that I turned on.

REPORTER (over TV): The search for answers intensifies

as police dive on the crash site, joined on the surface by investigators

from the Australian Transport Safety Bureau.

NARRATOR: All five passengers, including CEO Richard Cousins, are dead.

So is the pilot, Gareth Morgan.

MORGAN: It was a day that drastically changed our lives.

It was a devastating moment and we still live with it every day.

HUGHES: My first thoughts

went to those who had just lost loved ones in such a tragic accident.

And then it was change gears, and went straight into the business side of things;

what did we know, and how we were going to approach the investigation.

HUGHES: Okay. Great.

How deep is the plane?

NARRATOR: The ATSB begins its investigation into the crash

that took the lives of six people.

Police are saying it's probably under 14 meters.

It's right here, in Jerusalem Bay.

NARRATOR: Recovering all the wreckage is crucial.

There was no radio contact with the pilot, the flight wasn't tracked on radar,

and the plane didn't carry a key source of information.

Unfortunately, we find with accidents involving smaller aircraft

it is very unlikely that they will have some form of recording device onboard.

NARRATOR: Until the wreckage can be recovered,

witness statements are all there is to go by.

Let's just walk through where you were and what you saw.

We consider witness interviews what we call perishable evidence,

in that we try to get that done as soon as possible.

WITNESS: Well, it took off normally.

It just seemed like any other flight.

HUGHES: We utilized aircraft models so that they can show us,

rather than tell us, what their observations were.

And where were you?

WITNESS: Near the creek. Here.

HUGHES: We also use maps to try and get a sense of what they saw,

and where they were positioned.

NARRATOR: Investigators quickly discover that

although several people witnessed parts of the fatal flight, no one saw all of it.

Thank you so much.

BOSWORTH: No smoke. No one heard any unusual noises.

Witness A says he takes off normally and flies down Cowan Creek.

Witness B sees him climbing. No obvious issues.

BOSWORTH: The initial witnesses we interviewed

described the flight path of an aircraft steady,

no erratic movements on the southern bank of Jerusalem Bay.

They then described the aircraft doing a steep turn

before the nose dropped and the aircraft impacted the river.

We've got a gap in the flight path. He starts off here and somehow ends up here.

NARRATOR: Investigators can't confirm the plane's entire flight path.

The more we spoke to the witnesses, the more questions it did raise.

Do you have the flight chart?

NARRATOR: As investigators review the flight chart, they make a key discovery.

He's not where he's supposed to be.

NARRATOR: The plane ended up in Jerusalem Bay,

a narrow, dead-end body of water west of the takeoff area.

HUGHES: We established that there was no operational reason

for the aircraft to be operating in Jerusalem Bay.

NARRATOR: With little to go on,

the biggest piece of evidence is on the bottom of the bay.

Investigators will have to retrieve it.

BOSWORTH: The lift of the wreckage was quite a nerve-wracking event for my team.

We had the area cordoned off to vessels, except for emergency services.

The police divers first went down and secured the main fuselage.

NARRATOR: The team delicately lifts the aircraft to the surface.

BOSWORTH: We were very careful, especially with the main fuselage,

which carries a lot of water.

We needed to be patient to drain the water from it

before we lifted it onto the barge.

NARRATOR: The full recovery of the wreckage of the Beaver Seaplane

provides hope for the investigation.

CAMPBELL (hums): Well, they got everything.

NARRATOR: ATSB investigator Lian Campbell is tasked

with dissecting what's left of the plane

and searching for signs of mechanical failure.

The nose is creased.

BOSWORTH: Let's check the flight controls.

CAMPBELL: The aircraft was delivered to the hangar inverted,

and we decided to keep it in that orientation,

one, for safety because it was quite stable,

and also it afforded us good access to the flight controls.

NARRATOR: Did the plane crash because of an engine failure?

Well, the blade is damaged.

CAMPBELL: We are looking for signatures

if it was providing power at impact with the terrain or water.

Slight forward bending here. There's a midspan bend too.

It's a double bend.

NARRATOR: Investigators find a pattern they recognize.

So the propeller was turning normally. The engine was working.

The wreckage examination determined

that we had a completely functional aircraft during the flight,

and at the time of impact everything appeared normal.

NARRATOR: Still without any answers,

investigators scour every inch of the plane, inside and out, looking for clues.

CAMPBELL: We noted that the forward cabin roof area was filled with mud.

To ensure that we're not missing any vital evidence,

I had the unenviable task of going through this mud.

Duncan.

This was in the cabin.

Wow. Great job.

NARRATOR: They find something completely unexpected.

The discovery of a camera could change the course of the investigation.

HUGHES: The camera was a crucial piece of evidence that we could, hopefully,

gain some more insights as to what occurred during the flight.

Maybe there's something valuable on the memory card.

NARRATOR: But the camera was under water for four days.

BOSWORTH: The compact flash card was damaged.

We treated this card just like we treat the memory

from a flight data recorder that is damaged.

The creasing damage on the nose and the fuselage is fairly significant.

Agreed.

NARRATOR: While work begins on the data card,

investigators turn their focus back to the wreckage.

Deformation and creasing of the fuselage and the pontoons

can give us an indication of the speed,

orientation, and angle of entry into the water.

NARRATOR: Investigators measure how much the force of impact bent the plane's nose.

Deformation angle is 25 degrees upward.

Normally, it's only 12.

So the impact bent the nose upward 13 degrees.

- Correct. - So maybe we're looking at a stall.

It's possible.

NARRATOR: With the engine operating,

and eyewitnesses reporting the plane in a steep right turn,

investigators consider whether the pilot lost lift over the wings,

stalled the plane, and fell from the sky.

Stalls at low altitude are dangerous because there's no time to recover.

BOSWORTH: It says here that the angle for a stall

is 12 degrees or more if the flaps were set to climb mode.

HUGHES: The flap actuator was extended.

So the flaps were set to climb.

NARRATOR: Investigators conclude the float plane stalled before hitting the water.

(plane drones)

BOSWORTH: We had a pilot who was in Jerusalem Bay at low altitude,

conducting a steep turn.

This raised questions with the investigation team

on what was happening in the cockpit.

HUGHES: So why would a professional floatplane pilot

go into a dead end and then stall the plane?

Good question.

NARRATOR: Investigators want to know more about the pilot

who crashed the floatplane into Jerusalem Bay, Australia.

BOSWORTH: The majority of his time is on float planes.

- More than 9,000 hours. - He was very experienced.

(engine drones)

GARETH: This is Float Beaver November Oscar Oscar.

HUGHES: It looks like he started with Sydney Seaplanes in May of 2017.

He also had a stint with them

between December 2011 and April 2014.

- 535 hours on the plane that crashed. - So he knew that plane.

Hey, look here.

He had an incident only a few days before the crash.

The pilot was involved in an incident

while he was flying a Cessna 208 floatplane.

- Was it his fault? - No, I don't think so.

It's just a rough landing in Rose Bay. Traffic was busy and waves were high.

HUGHES: The event was essentially a bad luck event

beyond the control of the pilot.

This guy was a competent pilot.

(Bosworth sighs)

So what are we missing here?

It was New Year's Eve.

- Not a normal day. - What are you getting at?

Was he celebrating a bit early?

NARRATOR: Is it possible the pilot was impaired?

I'll check on the status of the toxicology report.

I'll make some calls.

HUGHES: One of the things that we do look at

is whether there was the use of any substances such as alcohol,

or any other medications they may have been taking.

BOSWORTH: Can you think back?

What was he up to while the passengers were having lunch?

(Gareth laughs)

BOSWORTH: He had a lunch break at the café at Cottage Point.

Happy New Year, my friend.

BOSWORTH: We were aware that the pilot had been required to move his Beaver

while another aircraft entered the area to onboard passengers.

I gotta go. I gotta move my plane.

Okay.

NARRATOR: Did Gareth Morgan have a drink between flights?

All right. Right. Thank you.

- No one saw Gareth having a drink. - Toxicology report confirms that as well.

MORGAN: We knew his integrity.

We knew that he would have had the wellbeing of his passengers

first and foremost in his mind at all times.

NARRATOR: A month into the investigation,

and the ATSB can't find any problems with the pilot or the plane

involved in the crash at Jerusalem Bay.

MORGAN: Nobody knew what had happened.

Something went terribly wrong in that cockpit and we did not know what.

NARRATOR: Investigators place their hopes on the camera found in the wreckage,

and the data on the memory card inside.

BOSWORTH: This was meticulous work.

The controller chip contained 144 solder points,

which needed to be reconnected under the microscope.

Thank you. It looks like we got something. The lab is sending the images now.

We were successful in recovering over 350 images from the compact flash card.

NARRATOR: Investigators analyze the pictures,

hoping they see something that might help them solve the case.

It looks like they're taxiing.

(plane drones)

HUGHES: Oh, it's taken from the passenger's side next to the pilot.

NARRATOR: The next 22 pictures were taken during the taxi, takeoff, and climb.

Nine were taken while the plane was airborne.

Taken over 39 seconds.

That's the last one.

(sighs) Too bad that's all there is.

I think there's more we can do with these.

When we had the photos from the accident flight,

we decided to see if we could rebuild the flight path of the aircraft

using these images.

Time: 15:11:45. Direction: forward.

Estimated altitude: 98 feet.

NARRATOR: They compile data from the photographs about the plane's position,

the camera angle, and the time of day.

BOSWORTH: Okay, that's all of them. Let's process this.

So? How's it going?

NARRATOR: Strung together, the images provide investigators

with a key portion of the plane's flight path.

HUGHES: Using camera tracking software,

we were able to get a better idea of the aircraft's flight path,

but also have a more accurate understanding

of the altitude of the aircraft.

(simulation plane drones)

BOSWORTH: The plane is at 98 feet and turning right

and it stops climbing for some reason.

HUGHES: That's odd.

BOSWORTH: We could see that the aircraft was in a bank turn,

but despite being in the climb flap setting, the aircraft was losing altitude.

NARRATOR: The photo analysis tells investigators

that the plane was descending,

but the complete flight path remains an educated guess.

Well, the good news is that matches the flight path from our eyewitnesses.

But it doesn't go much beyond that.

BOSWORTH: You're right. We need to come at this from a different perspective.

HUGHES: At that point,

because we had no obvious reason as to why the accident occurred,

we were looking at all the other possible hypotheses.

Maybe he had a seizure.

Or heart failure.

Well, that's a possibility.

His medical records indicate no history of headaches, blackouts, dizziness.

I'm not seeing anything.

NARRATOR: Investigators shift their focus back to the pilot, Gareth Morgan.

What about the cardiology?

This isn't normal.

Some of the ECGs had signs of sinus bradycardia,

which is a slower than normal heart rate.

His resting heart rate is 50 bpm.

He's like a trained athlete.

BOSWORTH: Yeah, it's an abnormality. But it's not a problem.

He was a very fit individual and there was nothing in his medical history

that could have led to medical incapacitation.

I thought we'd have more answers by now.

NARRATOR: Almost two years into the investigation,

the ATSB prepares a final report

without any firm conclusions about what caused the crash.

BOSWORTH: The investigation team were disappointed

and frustrated that they could not provide an answer to the families.

(phone ringing)

Duncan Bosworth.

Yeah, well, incapacitation was always a possibility.

We went pretty far down that road. We came up empty.

While the report was being prepared, we have an internal review.

This included our aviation medical specialist.

No, we must have tested for that.

I'll get back to you, all right?

The aviation specialist raised the fact that

carbon monoxide could have been an issue during this accident.

(plane drones)

NARRATOR: When aviation fuel is burned,

exhaust from the engines contains a highly poisonous carbon monoxide gas,

which can cause short-term symptoms.

Long term exposure can have a severe impact on health, and can be fatal.

They tested for carbon monoxide, right?

Here's the pathologist's report.

BOSWORTH: I said, "I thought it must have been examined,"

because we had the toxicology report

and nothing had been raised about carbon monoxide.

Kerri?

It's not here.

I could not find evidence of carbon monoxide testing during the autopsy.

I have a few questions for you.

NARRATOR: Investigators contact the state's health pathologist.

Is there any reason you didn't test for carbon monoxide poisoning?

NARRATOR: The team learns that pathologists

do not test for carbon monoxide unless there's evidence of a fire.

Any chance you still have the original samples?

I see. Oh, you do.

Oh, that's great.

HUGHES: That's when they went off and did the additional testing

to assess whether carbon monoxide was an issue or not.

NARRATOR: 26 months after the crash,

Gareth Morgan's blood sample is tested for carbon monoxide.

Look at this.

NARRATOR: The results provide investigators with their biggest lead yet.

I felt we may have an answer in our grasp.

Morgan's carbon monoxide levels were at 11%.

Some of the passengers also tested positive for CO poisoning.

(heavy breath)

NARRATOR: Toxicology results confirm

that the pilot and two passengers of the ill-fated floatplane

had higher than normal levels of carbon monoxide in their blood.

(plane drones)

HUGHES: We were re-energized

because we may have found that missing piece of evidence.

According to this study, the pilot would have been suffering

from neurobehavioral and cognitive side effects.

We did a lot of research to see what that 11%, in particular for the pilot,

how that would have affected his performance.

You'll see Cowan...

um...

Comox Creek.

NARRATOR: Was Gareth Morgan's carbon monoxide level high enough

to incapacitate him and cause him to crash the plane?

BOSWORTH: At 11%, he would have had feelings of nausea,

dizziness, possibly a headache.

HUGHES: It's hard to know with those symptoms

if it's carbon monoxide poisoning or something else.

NARRATOR: The side effects of 11% carbon monoxide poisoning are so insidious,

it would have been hard for Gareth Morgan to be aware of what was happening to him.

HUGHES: Quite often the cognitive effects can be quite subtle,

and they may often be overlooked or even dismissed by the pilot.

How much carbon monoxide does he need to breathe in to reach 11%?

The safety literature says there would have to be

a concentration of 80 parts per million in the cabin for a sustained period.

That's an awful lot of carbon monoxide in the aircraft.

- So, what's the source? - And how did it get into the cabin?

BOSWORTH: We knew the source of carbon monoxide in an aircraft

would be the exhaust system or a heater in the aircraft.

There was no heater, so our focus was on the engine exhaust system.

Well this piece seems okay.

NARRATOR: When an engine burns fuel,

the hot gases are directed through the exhaust manifold and out of the tailpipe,

preventing them from entering the plane's cabin.

Take a look at this.

See those cracks?

NARRATOR: Investigators take a closer look at pieces of the cracked manifold,

to determine if the damage occurred before or after the crash.

(tense music)

There's some oxidation here.

NARRATOR: Rust on the fractures in the exhaust manifold

tells investigators that the crack developed prior to the accident.

We found the leak.

After we discovered there was an exhaust leak,

we had to determine how the carbon monoxide got into the cabin

to affect the occupants.

What's the most likely point of entry?

HUGHES: Right here, the firewall.

NARRATOR: Investigators try to determine

how carbon monoxide entered the floatplane's cockpit,

incapacitating the pilot.

The firewall exists between the engine accessory bay and the cabin

to prevent fumes getting into the cabin.

Zoom in.

NARRATOR: The team examines the plane's firewall.

It's pretty banged up.

NARRATOR: They focus on two panels,

which allow access to the engine for maintenance.

Here's what we found.

NARRATOR: They discover the left access panel

is missing one of its four required bolts.

The right panel is missing two.

BOSWORTH: That means there were three holes in the main firewall

on the day of the flight.

(Hughes hums)

NARRATOR: It's a pathway for exhaust to travel from the engine bay

into the cabin of the Beaver.

(heavy breath)

Several pre-existing cracks in the exhaust system

released the poisonous gas into the engine bay.

Tiny bolt holes allowed the gas to leak into the cabin through the main firewall.

BOSWORTH: So we have the source and the point of entry.

NARRATOR: The discovery leaves investigators with a burning question.

How long has the dangerous problem existed?

(plane drones)

The last work performed on the parts was done in early 2017.

NARRATOR: Maintenance records show when the access panels were last modified.

That's months before the accident.

HUGHES: That means Sydney Seaplanes' pilots

have flown the same Beaver floatplane hundreds of times

without being affected by the carbon monoxide leak.

And it also means Gareth Morgan flew the plane dozens of times himself

without a problem.

So why did it affect him this time?

One of the key questions we were asking ourselves was:

Why did the accident happen on this flight?

NARRATOR: ATSB investigators examine pilot logbooks to understand

what made the fatal flight of a Sydney Seaplane different from others.

He's flying the same plane day after day.

It has the same problem.

But nothing happens until New Year's Eve?

I can't figure it out.

What was his schedule on the day of the crash?

Well, he's making flights all day long.

So the carbon monoxide is gonna build up in his system.

HUGHES: An individual's carbon monoxide levels will increase with intensity,

depending on the duration.

We had a pilot who was conducting multiple flights throughout the day

with only short intervals between each flight.

There's something else.

NARRATOR: As investigators reconstruct Gareth Morgan's schedule,

they remember they have to add one more piece to the puzzle.

BOSWORTH: An hour before he took off from Cottage Point,

Gareth Morgan was asked to move his plane off the dock

- to make room for another plane. - I gotta go. I gotta move my plane.

HUGHES: Maybe Morgan was exposed

to even more carbon monoxide gases while he moved the plane.

Exactly.

How long did that take?

27 minutes.

That's almost as much as an extra flight.

That's a lot more time in a plane.

NARRATOR: Morgan had to maneuver his plane away from the dock and around the bay

while another plane picked up passengers.

There's still a missing link.

These holes don't seem big enough to let in enough exhaust.

Why is that exhaust flowing into the cabin?

Maybe he had the windows open during the flight?

Good point.

That would create enough suction for the carbon monoxide to flow in.

(heavy breath)

BOSWORTH: Most pilots have their windows down

to get some ventilation into the cabin.

NARRATOR: Investigators revisit pictures they collected from witnesses.

BOSWORTH: This was taken earlier in the day.

It looks like he cracked the door

during the taxi into Cottage Point to get some air.

NARRATOR: The open door could have created a draft

that sucked the exhaust into the cabin through holes in the firewall.

But is a short taxi really long enough to be dangerous?

Hard to say.

Here's a short video from one of the witnesses

during the time the pilot moved the plane.

The windows are closed.

But check out the door.

An extra 27 minutes in the plane, with the door ajar.

That likely elevated the level of carbon monoxide in the pilot's system.

BOSWORTH: The investigation team had an hypothesis about how the door ajar

may have exacerbated the passage of carbon monoxide.

We needed to test this theory.

(clears throat)

(engine rumbling)

Okay. Initiating test number one, with the door closed.

(clacking)

NARRATOR: Investigators recreate the conditions of Gareth Morgan's plane

to see if concentrations of carbon monoxide

were high enough to incapacitate him.

We needed to use an exemplar Beaver aircraft with a simulated exhaust leak

and access panel bolts removed to test our hypothesis.

NARRATOR: They begin the test with the windows and doors closed.

BOSWORTH: First, we had to set a baseline level with the engine running.

We then removed the access panel bolts and simulated an exhaust leak

by feeding the exhaust from the engine directly into the engine bay.

55 parts per million.

There was no dangerous level of carbon monoxide in the cabin at that stage.

Okay. Let's clear the cabin and start again.

NARRATOR: To protect against carbon monoxide poisoning,

investigators agree to stop the test if the levels reach 120 parts per million.

BOSWORTH: We then tested with the door ajar.

It has to get to 70 parts per million.

And we saw that the levels increased.

(beeping)

NARRATOR: Within minutes, carbon monoxide in the cabin climbs to deadly levels.

BOSWORTH: We're at 144 PPM in here. Way too high. Let's shut it down.

Prolonged exposure to carbon monoxide levels greater than 144 parts per million

is dangerous to the occupants.

(engine quiets, shuts down)

NARRATOR: The tests are conclusive.

(exhales)

We did it.

It was a relief to see that our theory may have been proved

and confirmed that carbon monoxide could enter the cabin.

(plane drones)

NARRATOR: Investigators worry the same thing could happen again.

They track down other Beaver floatplanes that were serviced by the same company

that maintained the Sydney Seaplanes' fleet.

There's more than one plane with the same problem.

We inspected the access panels on three other Beaver aircraft,

and we were surprised to find

that there was one bolt missing from each of those panels.

BOSWORTH: It's unbelievable. It was the same in every one of them.

HUGHES: They have to be fixed. Immediately.

NARRATOR: The missing bolts are replaced in all the planes where they're missing.

As investigators try to determine how the accident could have been prevented,

- they're left with one last question. - Was this thing even working?

NARRATOR: Carbon monoxide detectors provide pilots with the opportunity

to detect exposure before they become incapacitated.

(heavy breath)

Was the carbon monoxide detecting equipment

- on the Beaver floatplane functioning? - Um.

So how does this one work?

Well it's supposed to turn a different color when carbon monoxide is present.

It's sun-bleached. There's no way it was working.

BOSWORTH: When we examined the carbon monoxide detector from this aircraft,

it was a beige color,

which meant it was unserviceable and not capable of detecting carbon monoxide.

You know, the detectors aren't even mandatory.

Not in Australia.

Not anywhere.

NARRATOR: The ATSB's final report highlights the critical importance

of audible carbon monoxide detectors.

HUGHES: As a pilot myself, I strongly encourage all pilots

to carry active carbon monoxide detectors every time they go out flying.

MORGAN: I have carbon monoxide detectors in my home.

They're very loud and they're not expensive.

(plane drones)

This should be mandatory in all small planes.

(heavy breath)

NARRATOR: The crash at Jerusalem Bay

raises awareness of the deadly threat carbon monoxide poses to aviators.

(heavy breath)

HUGHES: It was fulfilling to be able to identify important safety issues

in the hope that we can prevent such a tragic accident

from occurring again in the future.

But it was also rewarding to provide the family and friends

- some degree of resolution. - GARETH: Watch your step.

MORGAN: I've had many people, particularly after his death,

say the marvelous experiences they had as passengers with Gareth.

He really touched people with his humbleness

and his sense of dedication to his profession.

And that's very much the human being that Gareth was.