Original subtitles

A thousand metres above the frigid North Sea, disaster strikes.

A helicopter is crippled in the middle of a sudden storm.

The pilots struggle for control as it sinks helplessly towards the sea.

They're far from land, off the radar screens;

no one knows exactly where they are.

In the days that follow,

investigators search for the truth hidden in this tangled wreck.

The cause of the crash shocks those involved,

and reveals a hidden danger that reaches far beyond the North Sea.

- 3,000? - We're not getting any oxygen!

- We have the terrain alarm. - Aero Peru 603...

We are in an emergency.

The need for oil drives men to some of the most unpleasant places on Earth.

This is one of them.

The North Sea divides Britain from mainland Europe.

It's a shallow sea and the cruel winds that race across it

can whip up enormous waves.

The sea is cold, grey and violent.

But there's oil out here,

and so dozens of drilling platforms and thousands of men

must face whatever the weather throws at them.

The only efficient way to get the men out there is by helicopter.

The flights are rough and long, up to 500 kilometres each way.

After years, the trip has become largely routine,

the danger below forgotten by many.

What was that?

But on a cold January morning in 1995,

18 men flying over the North Sea were faced with a horrible question.

Mayday! Mayday! Mayday! Tail-rotor failure! Ditching!

Could they survive in this extremely hostile environment?

Oh, God! Ah!

January 19, 1995.

Commander Ced Roberts and First Officer Lionel Sole

work for Bristow Helicopters in Aberdeen, Scotland.

Their job is to ferry oil workers out to the oil platforms in the North Sea.

By mid-morning, they've completed one trip already,

and are getting ready to head back out.

Their helicopter is Super Puma 56 Charlie.

While it's being checked out and refuelled,

Flight Officer Sole checks the flight logs,

and Commander Roberts goes through the weather reports,

which are updated every two hours.

Oh, weather's okay. Good for January.

This is where they're heading: The North Sea.

The discovery of oil here in the 1960s

was a shot in the arm for the British economy.

Brent Crude, as the oil is known,

is a light, sweet crude, ideal for turning into gasoline,

and its price is a benchmark on the international oil market.

It helped turn Aberdeen, the Scottish port city closest to the oil rigs,

into a boom town, the European oil capital.

All the leading oil companies have offices here.

The city is focused on getting the black gold ashore.

Because the rigs are so far offshore,

and the weather so unpredictable,

helicopters are the only way to reliably ferry workers back and forth.

Hundreds of thousands of people make the trip every year.

The Super Pumas are one of the workhorses of the North Sea oil industry.

Used around the world by industry and military,

they're durable, tough, and made to withstand the elements.

There are more of these helicopters flying offshore here

than anywhere else in the world.

The passengers heading to the platforms today

gather in the heliport's departure lounge.

They all work for the Texas company Marathon Oil.

The North Sea has scores of oilfields.

They are divided up between several countries, including England and Norway.

The governments then sell the rights to drill to a variety of oil companies.

Marathon operates three platforms

in the so-called Brae Field, Brae East, Bravo and Alpha.

North Sea oil platforms are like cities that never sleep.

They stand on the seabed, held up by enormous legs of either metal or concrete.

Below each one, pipes snake out to the seabed.

Some straight down,

others fanning out at an angle for up to several kilometres.

The same platform may be extracting both oil and natural gas

at the same time.

Out here, you're surrounded by the sea with nowhere to go.

The weather is often horrible.

And the work on a rig can be rough, dirty and dangerous.

It's difficult to find and retain the skilled workers

needed to pull the oil from the sea.

So the platforms are built to keep the workers happy.

Movies, internet cafes, gym equipment,

even great food,

are all provided by management to ensure the men are entertained.

During 12-hour shifts, workers handle heavy equipment.

And deal with great heights...

...or great depths.

But there are strict rules, too.

To protect the safety of everyone onboard,

there's no drinking and smoking is severely restricted.

Mayday! Explosion or fire on the pipe or platform.

All personnel abandon.

One of Britain's worst disasters happened in the North Sea oilfields.

In 1988, on Occidental Petroleum's Piper Alpha platform,

the gas exploded and set fire to oil.

167 men died...

The potential for disaster is never very far away.

But on this January day, the Marathon Oil workers prepare as they always do.

All 16 are scheduled to spend two weeks on Marathon's Alpha platform,

followed by two weeks off.

To these men, getting to work has become routine.

But getting a ticket on this flight

calls for something a little out of the ordinary.

None of them is permitted to board a helicopter without first going through this:

helicopter underwater-escape training.

Their lives may depend on knowing how to get out

of a submerged helicopter or oil rig,

and knowing what to do once they find themselves in the chilly North Sea.

Several accidents over more than 20 years have driven home the point.

Training may help a worker survive.

Before they set off on every flight, they must watch the video:

How to Behave if There's an Emergency on Your Flight.

They've seen it all a thousand times.

In an emergency, if time does not permit,

just tighten your lap strap and brace for impact.

To exit through the windows,

pull the red tab to completely remove the rubber seal...

The passengers fasten their survival suits.

Made of GORE-TEX, these dry suits won't keep them afloat,

but are supposed to keep the water out if the workers are thrown into the sea.

Their bright colours are also designed to make rescue easier.

The trip to the Brae Alpha oil platform is 230 kilometres.

If all goes well, it will take little more than an hour.

Then, 120 miles out, they'll reach an area called the Gate.

That's where all the helicopters split up and go their separate ways

to the individual oil platforms.

Brae Alpha is about 40 kilometres from the Gate.

For part of the journey,

the radar operators at Air Traffic Control in Aberdeen won't be able to see them.

The reason why we lose low-level radar coverage out over the North Sea is,

in essence, because the Earth is round.

As a helicopter's flying outbound to an oil rig,

it's actually following the curvature of the Earth.

But radar pulses travel in straight lines,

which means that as they travel further and further away,

a gap opens up between the surface of the Earth and the radar waves.

If an aircraft flies into that gap, then it'll disappear from radar.

In the case of Aberdeen, a helicopter operating at about 2,000 feet

will disappear into that gap at about 80 miles.

It's a black hole, which Super Puma 56 Charlie is now entering.

The helicopter and the 18 men onboard are over halfway to the rigs.

And from this moment on, no one knows exactly where they are.

56 Charlie is a Super Puma helicopter

serving the North Sea oil platforms off the coast of Britain.

It's halfway through a long flight carrying 16 passengers

to the Brae Alpha oil rig.

The crew is getting concerned about what they see on their weather radar.

The forecast called for scattered clouds,

but the weather is changing fast.

What do you think about this cloud?

It's quite thin.

Yeah, but look. We're getting some cumulus too.

It's quite small. About 100 yards across?

- Yeah, but it's developing a bit. - Mm.

Cumulus are puffy white clouds like balls of cotton wool.

They're beautiful to look at, and usually harmless.

They only last between five and 40 minutes.

But helicopter pilots prefer to go above them if possible,

because the air inside and below gets very bumpy.

- Let's try to climb above it. Go to 5,000 feet. - Right.

Oh, look. There's a line of them.

All along the route, exactly where we're going.

Hmm. Yeah, we're not gaining anything by this.

- Let's drop back down to 3,000 feet. - Alright.

So far, the weather is nothing to worry about.

But over the North Sea, it can change suddenly.

This corner of Europe is where the warm winds from the Atlantic

meet the icy blasts from the Arctic and Siberia.

The warm water vapour condenses into clouds, cools, then sinks.

It creates strong winds, pushing the huge masses around.

The friction caused by this motion can make the clouds electrically charged,

and that electricity can be released as lightning.

What starts out as a placid day can end up in a violent storm.

It's now one hour after takeoff,

and 56 Charlie is approaching the Gate,

the point where helicopters begin their descent to the individual oil platforms.

They're 25 miles from their destination,

and the weather is starting to get worse.

Brae Traffic, 56 Charlie,

120 miles on the 056 HMR.

They make contact with Brae Traffic Watch,

located on one of the oil platforms.

It handles all the comings and goings of helicopters.

But Brae Traffic doesn't have radar.

It too has to rely on the pilots to tell them where they are.

Leaving 3,000 feet. Would you take the flight watch?

Roger, 56 Charlie. I have your flight watch.

Aberdeen information, Bristow's 56 Charlie at 120 miles.

Leaving 3,000 feet. Brae has the flight watch.

Roger, 56 Charlie. Continue with ferry traffic.

Quite suddenly, the weather has changed.

Instead of the harmless fluffy balls of cotton wool,

a line of dangerous cumulonimbus clouds is now blocking their path.

They rise up like huge white mountains, more than 10,000 metres,

far higher than the chopper can fly.

Underneath, they're dark and menacing.

Pilots try to avoid them at all costs.

Inside, gusts of wind can reach up to 100 km/h.

The turbulence can make the flight unpleasant,

but that's only part of the danger.

The cumulonimbus, that's the granddaddy of all clouds.

It stretches from round about 1,000 feet at its base

all the way up to 28-30,000 feet.

They are the most dangerous clouds that you'll come across,

particularly small aircraft like helicopters.

Within a cumulonimbus, you're going to find severe turbulence,

you're going to find ice and find heavy rain,

and, of course, you're going to find lightning.

Flying a helicopter, that's not where you want to be.

Lightning is one of the most powerful forces of nature.

Around the Earth, it strikes an average of 100 times per second,

each strike with the power of up to a billion volts.

Aircraft can't completely avoid it.

On average, every passenger jet will be hit once a year by lightning.

But the design of the planes helps prevent them being badly damaged.

Their bodies are traditionally made of aluminium,

which is a good conductor of electricity.

The lightning passes harmlessly along the fuselage and exits from the tail.

Helicopters use the same type of design to keep safe,

and helicopters need it in the North Sea.

With such stormy weather and so many helicopters,

lightning strikes are inevitable.

As they begin their descent,

the Super Puma enters the line of clouds that stands in their path.

- Bits of cloud coming up here. - It's okay.

It's still green. Let's carry on through that.

Green on the weather radar means there's rain,

but it's not heavy enough to worry about.

What the pilot sees is that it's simply like a television screen,

and on that television screen he has a map,

and overlaid on top of that map is a series of banded colours.

If there's no rain, he has a blank map;

if there's lots of rain and it's heavy, he has lots of red squares on that.

And that gives you an idea of the intensity and location of the rainfall.

On board 56 Charlie, the weather gets more intense.

They begin to get pelted by hail.

Hey, where'd this come from?

It's coming in through the vent.

It's like being inside a beanbag swamped by polystyrene balls.

It's so thick.

How come the engines are still running?

There can't be any air left out there. - No.

Now another problem.

We've got a hard-over on the ice detector.

- It's probably an ice pellet stuck in the probe. - Right.

The helicopter has an ice detector,

a probe outside the craft which is supposed to tell the pilots

whether there's ice on the blades.

But they think it's become jammed with ice and is giving a false reading.

And then... disaster.

- Bloody hell! - What was that? - Lightning. I saw it.

This is bad. There's something very, very wrong with this.

We'll have to go down, I'm afraid.

The helicopter has been damaged,

but they don't know how badly.

The entire body is shaking and vibrating.

The crew's first instinct is to get down to a lower altitude

in case the worst happens and they fall out of the sky.

Mayday! Mayday! 56 Charlie. Lightning strike.

Severe vibration.

Mayday! Mayday!

Forty kilometres away,

another helicopter is about to leave an oil platform.

Commander Brian Backhouse is loading passengers onto 56 Bravo,

and preparing to fly back to Aberdeen.

That's everyone. All set.

Suddenly the Loading Officer hears Lionel Sole's Mayday call on his radio.

Mayday! Mayday! 56 Charlie. Lightning strike.

Hear that Mayday, 56 Charlie?!

Gentlemen, my apologies, but we have to disembark you.

We have an airborne emergency on a sister aircraft.

Backhouse hurriedly unloads his passengers.

He intends to help if he can.

Meanwhile, a gale is steadily building up,

with winds in excess of 70 km/h.

The seas are mounting.

The crew of 56 Charlie are struggling to keep control of their crippled helicopter.

After the initial flash, though, the situation hasn't got worse.

The Grampian Freedom is a standby ship positioned near the oil rigs

to give oil workers a way to escape if anything goes wrong.

Her skipper, John MacInnes, hears the helicopter's distress call.

We increased, uh, the speed to full speed ahead.

Everybody was informed about the vessel,

uh, and told to get ready,

uh, for survivors to be taken aboard.

Back on the Bravo platform,

what was a routine flight for Brian Backhouse is about to become a rescue mission.

He intends to find the stricken helicopter and nurse it to safety.

If it crashes into the sea, he'll direct rescue ships to the spot.

But they're not sure where to go.

Let's go to the Gate and proceed from there.

At least they have a starting point.

The Grampian Freedom doesn't know where to go, either.

They're getting conflicting messages about where 56 Charlie is.

The helicopter's tiny size and the rough seas make it hard to find.

On the damaged helicopter, Commander Roberts briefs the passengers.

Gentlemen, you are obviously aware of the severe vibration.

We've had a lightning strike. So please, pull up your hoods,

zip up your suits and prepare for a possible ditching.

Countless hours of training

is supposed to have prepared all on board for a moment like this.

In a real emergency, how many will remember it?

1,200 feet. We're still flying.

Let's try to make it to Brae Alpha and land there.

Their destination, the Brae Alpha platform, is now only 11 kilometres away.

Three minutes have passed since the explosion,

and things don't seem to be getting any worse.

I'll just try a few small inputs to make sure everything's working.

Yes, we've got control in pitch. We've got control in roll.

And we've got control in yaw.

Tail rotor!!!

The helicopter is beginning to spin round,

a sure sign that something's happened to the tail rotor.

The only thing the pilots can do to stop the spinning

is to switch off the main rotor blade.

- Power off! - Engines off!

Ditching has become inevitable.

56 Charlie is falling fast.

More than 600 metres a minute,

with the main rotor acting like a kind of parachute,

the blades being turned only by the air that rushes through them.

Mayday! Mayday! Tail-rotor failure. Ditching.

Brace for emergency landing.

At this speed, they're about 40 seconds from hitting the North Sea.

The other pilots in 56 Bravo are searching in vain.

There's no sign of 56 Charlie in the sky or in the water.

Then they hear another distress call.

Mayday! Mayday! Tail-rotor failure! Ditching!

Mayday, Mayday, Mayday.

Relaying for 56 Charlie.

We have a suspected tail-rotor failure. He is ditching.

Commander Backhouse in 56 Bravo knows that he is closest

to the stricken helicopter.

Everything depends on him.

But he's not equipped to locate the distress beacon 56 Charlie will use when it ditches.

All he can do is search mile after mile of grey sea.

Back on the Grampian Freedom,

the crew begins searching the sea, as well as the sky.

But they know 56 Bravo can cover ground more quickly

than the enormous, slow-moving ship.

They do what they can and wait for better directions.

Floats! Floats! I can't find the floats!

- I got it! I got it! Just keep it at trim angle! - Right.

The pilots of 56 Charlie are about to attempt one of the most difficult manoeuvres:

ditching, or landing in the middle of the heaving sea.

Floats under the helicopter are meant to keep it from sinking.

If they're deployed too soon before touchdown,

the chopper may lose what little stability it has, and topple over.

Too late, and they won't inflate completely.

Instead of riding the waves, the helicopter will sink below them.

There's no second chance.

They time it perfectly.

We're down.

Seems quite stable.

They've landed safely, but no one knows if they will stay afloat.

Helicopters are top-heavy,

and they fear it could keel over and sink at any moment.

- Let's get outta here! - Do the doors!

They need to get the life rafts out,

inflate them and board them quickly.

They fear that if the helicopter rolls over,

it will trap them all inside.

- Lift that end! - Hold the rope!

You go back and help with the evacuation, I'm gonna shut things down here.

I'm gonna try one last mayday call.

But the evacuation doesn't go smoothly.

When they throw out one of the life rafts,

the strong wind blows it back against the helicopter.

They can't get into it. - We can't get this one down! Can we go out the other side?

Better we all stay together anyway! Off you go! Go on, go on!

Go! Mayday! Mayday!

56 Charlie. We are on the water, floating, manning the dinghy!

He doesn't mention their position.

Make room, I said! Make room!

The raft is dangerously overloaded.

There are 18 on board, and it's only meant for 14.

Water is already up to their ankles, and rising.

Once in the raft, they have no way of communicating where they are.

For the first time, the pilots are able to see what caused the disaster.

The rear-rotor-blade assembly and gearbox have broken off,

and are hanging down the side of the helicopter,

held on by just a couple of pipes.

No one realizes it yet, but in the rush,

they've forgotten to bring the distress beacon with them from the helicopter.

It sends out a signal that can be picked up by rescuers.

Forgetting it could mean the difference between life and death.

Two ropes attach the life raft to the helicopter.

They're meant to stop the raft from drifting away,

but they'll also drag them down if the helicopter sinks.

One of the passengers has a knife.

- Shall I cut the line?! - No, not yet!

We have a better chance of being spotted if we're close to the helicopter!

Problems mount.

The passengers are trying to raise the canopy to protect them,

but it gets stuck.

Without the canopy, they're at the mercy of the waves.

And then the helicopter itself becomes a danger.

When the doors were jettisoned,

they were supposed to be designed to slip down into the water and sink.

Instead, one of them, which has a jagged edge,

is floating on the surface and is heading straight for the raft.

The life raft has been punctured by the floating door.

Come on, bail! Bail with everything you got! We're gonna sink!

No, don't worry about it! We're not gonna sink!

We got double-layer rubber tubes here filled with air! It cannot sink!

One wave and we're under!

The pilots do their best to put on a brave face.

There are other helicopters and ships out there! They know we're down!

They heard our mayday!

The overloaded life raft is getting lower and lower in the water.

Inside, it's already waist-deep.

Now the pounding waves are pushing them beneath the sharp edges

of the drooping helicopter blades.

We need to get some distance! We'll have to cut the line!

There are supposed to be two safety lines connecting the raft to the helicopter:

one short, one long.

But the long line is broken.

The long line's been cut! It's been shredded!

You'll have to cut the short one!

The short line is the only thing attaching them to the helicopter.

If they cut that, they'll quickly drift away,

a tiny raft full of men at the mercy of the sea.

But if they don't cut it,

the jagged edges of the helicopter could tear their life raft to shreds

and sink them all.

Eighteen people have scrambled aboard a life raft

after their helicopter crashed into the North Sea.

The raft is overloaded.

It's been punctured by the jagged metal edges of the helicopter door,

and is getting lower and lower in the water.

They have to get away from the helicopter.

Flight Officer Lionel Sole takes the fateful decision and cuts the rope.

They begin to drift away into the storm.

The conditions are deadly.

Most of their survival suits are leaking freezing water.

For a person in the water, hypothermia can begin

when the temperatures of air and water added together is below 50 degrees centigrade.

In the North Sea in winter, the temperature is far below that.

Normal muscle and brain functions are quickly affected.

The core body temperature will sink,

followed by unconsciousness and death.

Their chances of rescue are slim.

No one knows where they are.

Just a tiny dot on a vast, turbulent sea.

Quiet, quiet! I hear something!

There's a helicopter!

The men are desperate.

This could be their last chance.

Quickly!

Pass me those flares! The flares in the pocket behind you!

We need help!

Here! Here! We're over here!

But it's all in vain.

The helicopter passes by.

The men can't believe it.

Their only hope is gone.

On 56 Bravo, Brian Backhouse can see only grey seas.

But suddenly, his co-pilot spots something.

Contact, right, 2:00.

Okay. Roger. Let's investigate.

Target, contact. Target confirmed. 56 Charlie.

Standby for position report.

Like a guardian angel,

56 Bravo hovers directly above the survivors for over an hour,

directing rescue boats and aircraft towards this tiny speck in the ocean.

He came in and hovered... fairly close,

because he wanted to count the number of people onboard the life raft.

So for a while, he was right over top of us and blowing us around a bit.

But as soon as he had gotten the information he wanted, he backed off,

and he was just marking the position for the rescue craft to find us.

First to arrive is the Grampian Freedom.

We had lookouts posted all around the vessel,

some on top of the bridge, on each wing at the bridge.

A helicopter came and he started crossing our bow,

which is not our procedure in that kind of situation.

Almost a mile away from the raft,

the Grampian Freedom launches its fast rescue boat.

The boat sets off at full speed to the rescue.

The rain and the waves make finding the raft difficult.

- Hey, hey, hey, hey! There's the boat! - It's coming fast!

No, no, no! Don't stick us!

Relax, boys. They know what they're doing.

Let's go! Quickly! Go!

The rescue boat throws a lifeline to the stranded men,

and they begin pulling themselves to safety.

But there's another challenge their training hasn't prepared them for.

We reached the, uh, the standby boat.

And you're looking at the hull, a huge steel hull,

you said, "I'm never gonna get up there."

But the crews are well-trained.

They wait for the swells to go up and down at the right motions.

And they have a large net hanging down the side of the boat,

and they said, "We're gonna come alongside,

we'll be on top of the wave and when we shout 'jump,' you jump and grab the net.

Don't look back, 'cause we'll be gone."

We came alongside, high up on the wave, grabbed the net,

the wave went back down, they were away and they pulled off,

and we just climbed the last few feet over the side, onto the Grampian Freedom.

Later that day,

a rescue helicopter winches up 14 of the survivors

and flies them back to Aberdeen.

Four of the men, however, never want to travel in a helicopter again,

so they refuse to leave the Grampian Freedom.

They're in for ever more misery.

They're buffeted by a force-10 gale

the whole of their long journey back to Aberdeen.

Through their skill and against all the odds,

Cedric Roberts and Lionel Sole have saved the lives of all onboard.

I must admit, at the time, I did think that was it, we were gonna die.

The whole world had changed from being really good

to being what I thought was a complete disaster at that time.

It was the worst situation I've ever been in, in the air,

and I was very worried that was gonna be it.

But the day after the accident, they came under suspicion.

Their report of what happened starts being questioned.

Lightning, notionally at least,

should not affect a very powerful North Sea helicopter.

This is the first time I can recall a lightning strike

having ended up with this kind of conclusion.

The experts are skeptical of the pilots' story.

No other helicopter is known to have crashed into the North Sea

because of lightning.

Perhaps there had been some mechanical failure.

There are even whispers of pilot error,

of recklessly flying into storm clouds.

The evidence to support their story

was now beneath the waves with 56 Charlie.

The Air Accident Investigation Branch,

Britain's air-crash detectives, begin searching for the truth.

It may look like a rig, but the Stadive is actually a ship,

mostly used for servicing oil platforms.

It has nine powerful engines which keep it stable in almost any weather.

And it carries miniature submarines for underwater exploration.

A day after the accident, it's brought in to find and raise the missing helicopter

from the bottom of the North Sea.

The investigation gets off to a good start.

Within a day, the television cameras onboard the Stadive's two submersibles

locate what's left of 56 Charlie on the seabed.

But raising it is a different matter.

They carry on working into the night.

Soon, several pieces of 56 Charlie have been recovered,

but still not the vital clue: the missing tail rotor.

Ed Trimble was the AAIB's lead investigator.

But the big problem was to recover the tail-rotor assembly.

Without that, the investigation was literally going nowhere.

We knew that the tail-rotor assembly,

uh, had been dangling over the side of the pylon as the helicopter had ditched,

and therefore had detached at some point

between the ditching and where we had caught up with the main wreckage.

Keeping the Stadive going would cost another £20,000 a day.

Ed Trimble rang his boss.

He was fairly skeptical of our chances.

Uh, he asked what I thought our chances were of finding the, uh, tail rotor, and I,

being an eternal optimist, said, "80%," to which he replied:

"I think you'd be very lucky if you had a 10% chance

of recovering the tail-rotor assembly in the North Sea."

Ed Trimble stays up all night,

relentlessly monitoring the underwater cameras.

I didn't want to be in a situation

where we would've missed any evidence of further wreckage in a particular...

any parts of the tail-rotor assembly.

Go get yourself a coffee, Eddie.

By the time, uh, 8:00 was looming,

I decided to go down to the galley to get a coffee.

And I couldn't have been away any more than maximum seven to 10 minutes

when I suddenly heard these...

tremendously excited shouts from our team.

I did it! Yes! Eureka! We found it!

- Hold position! - As I walked in, I ran in,

there, smack in the middle of the screen,

was the whole of the tail-rotor assembly.

And even at the first glance,

I could see that one of the tail-rotor blades showed clear evidence

of a lightning strike.

The crew was right.

The submarine's cameras reveal telltale burn marks on the tail-rotor blade.

A close look at the wreckage on the deck reveals

that two of the main rotor blades were also struck by lightning.

But it's this tail rotor that suffered the most damage.

Since lightning is not known to have forced a helicopter to crash into the North Sea before,

the question is: Why now?

Ed Trimble called in lightning expert John Hardwick

to discover just what had hit 56 Charlie.

What we wanted to do with this set of tests

was to take a set of tail-rotor blades from the Super Puma helicopter

and subject them to varying energy levels of simulated lightning strikes.

The lightning objectives at Culham

basically were to try and reproduce

the degree of lightning damage,

in order to identify what kind of level of energy was associated

with this particular strike.

This home video of the tests was taken by Ed Trimble.

Representatives of the company that makes the Super Puma were there too.

Hardwick ran the blade through several lightning strikes

until he was able to reproduce the damage found on the rotor blade.

To do it, he had to generate a simulated strike of enormous power.

Something far more dangerous than anyone thought the helicopter would be exposed to.

Something that wasn't supposed to happen over the North Sea.

There've been a few incidents over the years.

Minor strikes, a little bit of damage to the helicopter.

But we never expected anything as severe as happened on that day.

For one brief instant, it was more than all the electrical power

being consumed in the entire United States.

Some 30-billion watts.

And this enormous flash of lightning had happened over the North Sea,

where, each year,

almost three-million passengers fly unsuspecting to the oil platforms.

The helicopters we fly are certified to the highest standards.

It's the same as you'd get on a major airline that's flying transatlantic.

So we had no reason to believe that any lightning that we encountered

would do any severe damage to the helicopter.

Ordinary lightning wouldn't.

But this wasn't ordinary.

A lightning strike generates a huge pulse of energy.

We can detect these pulses of energy

via multiple transmitters and receivers that are situated throughout Europe.

The information is calibrated locally,

and once the position has been triangulated,

that's passed to the Met Office in London.

When the records were examined,

they showed something very peculiar.

This is what they think happened.

Inside cumulonimbus clouds,

tiny ice crystals are swept upwards by the wind currents.

At the top of the cloud, where it's much colder,

they combine with other crystals to form hail.

The hail, being heavy, plummets back to Earth.

On the way down, it hits the rising water crystals, causing friction.

The crystals become electrically charged.

On that particular day,

there was very little indication that there was any significance in these clouds.

We're flying along, everything just seemed very normal.

We went through what seemed to us,

by comparison to what was around that day, a fairly small cloud.

But there was suddenly a lot of snow and ice pellets in the air.

I've never seen as much in the way of soft hail pellets in my whole flying career.

And the worrying thing was that immediately we knew

that obviously there was a lot...

a high level of energy in that cloud

to produce that amount of soft hail,

which also meant there was a high chance of there being lightning there,

but by that time it was too late.

When a helicopter enters the cloud,

the sharp tips of its whirling rotor blades cut through these crystals,

causing more friction, more electricity,

until it's all released in a blinding flash.

The records show that the flash which hit 56 Charlie

had been the only one recorded over the North Sea that day,

caused almost certainly by the helicopter itself.

However, for some reason, nearly all the damage had been confined to the tail rotor.

What was it about the tail rotor that had made it especially vulnerable?

Then Ed Trimble made a remarkable discovery.

When the Civil Aviation Authorities certified the Super Puma as safe,

they had missed something important,

something which may have caused 56 Charlie to fall from the sky.

Safety investigators examine the wreckage of a helicopter

which crash-landed in the North Sea.

As they study the ruined aircraft more closely,

they uncover the cause of the accident.

When the British Civil Aviation Authority laid down the lightning safety standards,

they were looking at fibreglass blades,

then the normal material for helicopter rotors.

But in the 1980s, plane-makers began using the new composite materials,

like carbon fibre, which were lighter and stronger.

In particular, they began making the rotor blades

out of carbon fibre instead of fibreglass.

It was assumed that the same standards would apply equally to the new blades.

In the industry, that's known as "read across," and it's very dangerous.

In fact, it was the very design of these composite blades which brought down 56 Charlie.

Although made of carbon fibre,

composite blades have a metal anti-erosion strip glued on to protect the edge.

That's where the trouble starts.

Carbon is a conductor of electricity,

but it's a thousand times worse than aluminium,

so you get a thousand times as much heat produced.

The carbon blade gets very, very hot.

And when the current meets the metal strip running along the edge...

...there is furious arcing and sparking,

until finally part of the erosion strip explodes.

As little as 100 grams of the erosion strip flew off,

but it was enough.

Without its weight, the rear rotor was unbalanced.

That's what caused the vibration felt onboard 56 Charlie

immediately after the lightning strike.

Three minutes later, when Lionel Sole tested out the controls,

the unbalanced blades put the tail rotor under enormous stress.

The bolts holding it on snapped.

- We've lost the tail rotor! - Tail rotor's gone!

It was like a blowout in a car, only much, much worse.

Things, at that point...

were really very, very worrying.

Uh, we both knew what had happened. We'd lost the tail rotor.

And if you don't do exactly the right thing at that point,

your life expectancy is very short, it's seconds. We had to do the right thing.

We managed to point it into wind and there was quite a big sea building up.

And at 100 feet, I pull back on the stick to flare the helicopter...

...slow down its rate of descent,

and we were very fortunate at that point - a nice, friendly wave came along -

and as I levelled the helicopter, the wave came up,

we sat on the top of it and went down.

It was one of the best landings I've ever done,

but that was luck more than judgment.

As bad as it was, it could've been worse.

The two hydraulic pipes connecting the assembly to the helicopter did not break.

These two small-diameter pipes had held

the mass of the gearbox and tail-rotor assembly

dangling over the right side of the pylon.

Without the weight of the rotor assembly,

the helicopter would've tipped forward.

Had that tail-rotor gearbox and tail-rotor assembly

completely separated from the helicopter,

then all 18 lives would've been lost,

because the helicopter would've pitched down irrecoverably

and gone into the North Sea.

The investigators found the answer to the mystery of a helicopter crash,

but they stumbled across a bigger problem.

One that affects every air traveller.

Investigators believe that 56 Charlie's violent end

was caused by a savage lightning strike

greater than anything it was built to withstand.

And when the lightning hit,

it exposed a problem in the carbon-fibre blades that made them vulnerable.

The tremendous heat created where the carbon fibre met the metal erosion strip

could occur again.

And the same type of violent reaction could hypothetically take place

in any aircraft that has carbon fibre mixed with other materials.

Increasingly, aluminium is being replaced with carbon fibre.

The world's largest plane, the A380 Airbus, for instance, has over 20%.

What will happen if these planes encounter a monster lightning strike?

This was the investigators' biggest concern arising out of this Super Puma accident.

The findings were unexpected,

and treated with some skepticism.

Though the tests indicated that an unexpectedly large lightning strike hit 56 Charlie,

Britain's Civil Aviation Authority refused to accept it.

No action was taken to increase the safety standards

that these helicopters must meet.

I thought that the reaction was poor.

There seemed to be, uh, a real reluctance...

on their behalf to accept the evidence.

If Britain's air-crash detectives are right,

there is a real concern facing air travellers.

Flashes of lightning far greater than aircraft are supposed to encounter are possible,

and aircraft made of newer composite materials are at increased risk.

For the Super Puma, though, the lessons have been learned.

The design of the rotor blades has been vastly strengthened.

The erosion strips are now secured with heavy bolts.

And the pilots have been instructed to give storm clouds a wider berth.

The men who must fly these machines to work are prepared to accept the risks.

Well, I think the morning that we ditched,

we were very, very fortunate,

because the outcome could've gone horribly wrong.

But we survived. We got home.

My feelings that morning was: This could never happen to me.

Now when I fly in a chopper, especially in wintertime,

if it's gonna be buffeted about in the wind,

I sometimes get in the back of my mind: This can't happen to me again.

But we've all a choice. We've all a choice either to stop or we carry on.

And I'm still there 25 years later, still earning a living.

The crash of 56 Charlie was a hair-raising incident

that could so easily have ended in tragedy.

In the winter of 1995,

the skill of Commander Ced Roberts and Flight Officer Lionel Sole

saved the lives of their 16 passengers.

Roberts and Sole receive an award for their work.

The Guild of Air Pilots and Air Navigators recognized their skill and bravery

in the emergency landing.

Although we received a number of awards after the, uh,

the incident, um, from various organizations,

one thing I received, which is far more precious to me than any of them,

was from the daughters of one of my passengers.

It was this little card. It says, "Dear Captain Roberts,

I can't tell you how much I need to thank you after you saved my dad's life.

It took a lot of effort to try to keep calm while you were falling.

If you hadn't have got that helicopter in control,

my dad maybe wouldn't be here today.

Thank you very, very, very much."

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