Original subtitles

Narrator: 3,300 feet 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 toward the sea.

They are far from land...

Pilot: Mayday, mayday, 56 Charlie.

Narrator: ...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 is a shock for all those involved

and reveals a hidden danger

that reaches far beyond the North Sea.

Flight Attendant: Ladies and gentlemen, we are starting our approach.

Pilot: We lost both engines!

Flight Attendant: Put the mask over your nose.

Emergency descent.

Pilot: Mayday, mayday.

Flight attendant: Brace for impact!

Controller: I think I lost one.

Man: Investigation starting...

Man: He's gonna crash!

Narrator: January 19, 1995.

Commander Ced Roberts and first officer Lionel Sole

work for Bristow helicopters in Aberdeen Scotland.

Ced Roberts: I'll just sign this tech log, and I'll see you upstairs.

Narrator: Their job is to ferry oil workers

out to the oil platforms in the North Sea.

Man: Cheers, gentlemen.

Narrator: 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 refueled,

flight officer Sole checks the flight logs

and commander Roberts goes through the weather reports

which are updated every two hours.

Lionel Sole: The weather's okay.

Good for January.

Narrator: 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 boomtown,

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 the workhorses of the North Sea oil industry.

Used around the world by industry and military,

they are 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 oil fields.

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.

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, and great food

are 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 on board

there's no drinking,

and smoking is severely restricted.

Man: Mayday!

Explosion and fire on the piper platform.

All personnel abandon.

Narrator: One of Britain's worst disasters

happened in the North Sea oil fields.

In 1988,

on occidental petroleum's piper Alpha platform,

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 are 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 off an 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 all seen it a thousand times.

Man on video: 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...

Narrator: 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.

Man on video: ...the forward windows.

Narrator: Their bright colors are also designed

to make rescue easier.

The trip to the Brae Alpha oil platform

is 143 miles.

If all goes well, it will take a 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 25 miles from the gate.

For part of the journey,

the radar operators at air traffic control in Aberdeen

will not be able to see them.

John Miller: 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.

Narrator: 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.

Miller: If an aircraft flies into that gap,

then it will 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.

Narrator: It's a black hole

which Super Puma 56 Charlie is now entering.

The helicopter and the 18 men on board

are over halfway to the oil rigs.

From this moment on,

no one knows exactly where they are.

En route to the Brae Alpha oil rig,

the Super Puma crew becomes concerned

about what they see on their weather radar.

The forecast called for scattered clouds,

but the weather is changing fast.

Sole: What do you think about this cloud?

Roberts: It's quite thin.

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

It's quite small. About 100 yards across?

Roberts: Yeah, but it's developing a bit.

Narrator: Cumulus are puffy white clouds,

like balls of cotton wool.

They're beautiful to look at and usually harmless.

They only last between 5 and 40 minutes.

But helicopter pilots prefer to go above them if possible

because the air inside and below gets very bumpy.

Roberts: Let's try to climb above it.

Go to 5,000 feet.

Sole: Right.

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

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

Roberts: Yeah, we're not gaining anything by this.

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

Sole: Right.

Narrator: 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 vapor condenses into clouds, cools,

then sinks.

It creates strong winds pushing the huge masses around.

Friction caused by this motion can create electricity,

and that electricity can end up as lightning.

What starts out as a placid day can end up as 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 are 25 miles from their destination,

and the weather is getting worse.

Sole: Brae traffic, 56 Charlie,

120 miles on the zero 56 HMR.

Narrator: 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 has to rely on the pilots to tell them where they are.

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

Controller: Roger, 56 Charlie. I have your flight watch.

Sole: Aberdeen information,

Bristow's 56 Charlie at 120 miles,

leaving 3,000 feet.

Brae has the flight watch.

Controller: Roger, 56 Charlie.

Continue with Brae traffic.

Narrator: 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 30,000 feet--

far higher than the chopper can fly.

Underneath they are dark and menacing.

Pilots try to avoid them at all costs.

Inside, gusts of wind can reach up to 60 miles an hour.

The turbulence can make the flight unpleasant,

but that's only part of the danger.

Alex Hill: The cumulonimbus,

that's the granddaddy of all clouds.

It stretches from round about a thousand feet at its base

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

They are the most dangerous clouds

that aircraft can come across,

particularly small aircraft like helicopters.

Within a cumulonimbus,

you're going to find severe turbulence,

you're going to find icing, you're going to find heavy rain,

and of course you're going to find lightning.

If you're flying a helicopter, that's not where you want to be.

Narrator: Lightning is one of the most powerful forces

of nature.

Around the earth,

it strikes an average of 100 times every 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

keep them from being badly damaged.

Their bodies are traditionally made of aluminum,

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 they 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.

Sole: Bits of cloud coming up here.

Roberts: It's ok. It's still green.

Just carry on through that.

Narrator: Green on the weather radar

means there's rain,

but it's not heavy enough to worry about.

But soon, the weather gets more intense.

They begin to be pelted by hail.

Sole: Hey, where'd this come from?

Roberts: It's coming in through the vent.

Sole: It's like being inside a bean bag,

swamped by polystyrene balls.

Roberts: It's so thick.

How come the engines are still running?

There can't be any air left out there!

Sole: No.

Narrator: Now another problem.

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

Roberts: It's probably just an ice pellet

stuck in the probe.

Sole: Right.

Narrator: The helicopter has an ice detector--

a probe outside the craft

which is supposed to tell the pilots

if there's ice on the blades.

But they think it's become jammed with ice

and is giving a false reading.

And then...

Disaster.

Sole: Bloody hell! Roberts: What was that?

Sole: Lightning. I saw it.

Well, this is bad.

There's something very, very wrong with this.

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

Narrator: The helicopter is 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.

Roberts: Mayday, mayday! 56 Charlie.

Lightning strike. Severe vibration.

Mayday! Mayday!

Narrator: 25 miles away,

another helicopter is about to leave a different oil platform.

Commander Brian Backhouse

is loading passengers on 56 Bravo

and preparing to fly back to Aberdeen.

Brian Backhouse: That's everyone. All set.

Narrator: Suddenly, the loading officer

hears Lionel Sole's mayday call on his radio.

Sole: Mayday! Mayday! 56 Charlie.

Lightning strike.

Man: Hear that mayday? 56 Charlie!

Backhouse: Gentlemen, my apologies,

but we have to disembark you.

We have an airborne emergency on a sister aircraft.

Narrator: Backhouse hurriedly unloads his passengers.

He intends to help if he can.

Meanwhile, a gale is steadily building,

with winds of up to 60 miles an hour.

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 gotten any worse.

The Grampian Freedom is a standby ship

positioned near the oil rigs.

To give the oil workers a way to escape

in case anything goes wrong.

Her skipper, John Macinnes,

hears the helicopter's distress call.

John Macinnes: We increased the speed

to full speed ahead.

Everybody was informed about the vessel

and told to get ready for survivors to be taken aboard.

Narrator: 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.

Backhouse: Let's go to the gate and proceed from there.

Narrator: At least they'll 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.

Roberts: 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.

Narrator: Countless hours of training

are supposed to prepare everyone on board for a moment like this.

In a real emergency, how many will remember it?

Roberts: 1,200 feet. We're still flying.

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

Narrator: Their destination, the Brae Alpha platform,

is now only 6.5 miles away.

Three minutes have passed since the explosion,

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

Sole: 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!

Narrator: The helicopter is beginning to spin--

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.

Sole: Power off.

Roberts: Engines off.

Narrator: Ditching has become inevitable.

56 Charlie is falling fast--

more than 1,900 feet a minute.

With the main rotor acting like a kind of parachute,

the blades are turned

only by the air that rushes through them.

Roberts: Mayday! Mayday!

Tail rotor failure.

Ditching.

Brace for emergency landing.

Narrator: 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.

Roberts: Mayday! Mayday!

Tail rotor failure. Ditching!

Backhouse: Mayday, mayday, mayday.

Relaying for 56 Charlie.

We have a suspected tail rotor failure.

He is ditching.

Narrator: 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 carries.

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

On board the rescue ship Grampian freedom,

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

But they know helicopter 56 Bravo

can cover a bigger area much faster

than the slow-moving ship.

They do what they can and wait for better directions.

Sole: Floats, floats! I can't find the floats!

Roberts: I got it! I got it!

Just keep at a trim angle!

Sole: Right.

Narrator: The pilots of 56 Charlie

are about to attempt one of the most difficult maneuvers:

Ditching,

or landing in the middle of a 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 beneath them.

There's no second chance.

They time it perfectly.

Sole: We're down.

Roberts: Seems quite stable.

Narrator: They've landed safely,

but no one knows if they will stay afloat.

Helicopters are top-heavy.

They feel it could keel over and sink at any moment.

Man: Let's get out of here!

Man: Do the doors!

Narrator: 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.

Man: Lift that end.

Man: Hold the rope!

Roberts: You go back and help with the evacuation.

I'm gonna shut things down here.

I'm going to try one last mayday call.

Narrator: 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.

Man: We can't get this one down! Can we go out the other side?

Sole: It's better we all stay together anyway.

Off you go! Go on! Go on! Go! Go!

Roberts: Mayday! Mayday! 56 Charlie.

We are on the water, floating, manning the dinghies.

Narrator: He doesn't mention their position.

Sole: Make room! Make room, I said! Make room!

Narrator: 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 gear box 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.

Man: Shall I cut the line? Roberts: No, not yet.

We have a better chance of being spotted

if we're close to the helicopter.

Narrator: 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.

Man: Come on, bail! Bail with everything you got!

We're going to sink.

Roberts: No, don't worry about it.

We're not going to sink!

Sole: We've got double-layer rubber tubes here

filled with air.

It cannot sink!

Man: One wave and we're under!

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

Sole: There are other helicopters and ships out there!

They know we're down!

They heard our mayday!

Narrator: 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.

Sole: We need to get some distance!

We'll have to cut the line!

Narrator: There are supposed to be two safety lines

connecting the life raft to the helicopter--

one short, one long.

But the long line is broken.

Sole: The long line's been cut!

It's been shredded!

Roberts: You'll have to cut the short one!

Narrator: 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.

First officer Lionel Sole makes the decision

and cuts the rope.

They begin to drift away into the storm.

The conditions are deadly.

Most of their survival suits are filling with freezing water.

For a person in the water, hypothermia can begin

when the temperature of air and water added together

is below 58 degrees Fahrenheit.

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.

Man: Quiet, quiet!

I hear something!

Man: There's a helicopter!

Narrator: The men are desperate.

This could be their last chance.

Sole: Quickly! Pass me those flares!

The flares! In the pocket behind you!

Man: Come on! Spark the flare!

Man: Here! Over here! We're over here!

Narrator: 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 only see gray water.

But suddenly, his co-pilot spots something.

Co-pilot: Contact right, 2 o'clock.

Backhouse: Ok, roger. Let's investigate.

Backhouse: Target contact.

Co-pilot: Target confirmed.

56 Charlie.

Stand by for position report.

Narrator: 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.

Sole: He came in and hovered fairly close

because he wanted to count

the number of people on board 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 got the information he wanted,

he backed off,

and he was just marking the position

for the rescue craft to find us.

Narrator: First to arrive is the Grampian freedom.

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.

But the rain and the waves make finding the life raft difficult.

Man: Hey, hey, hey, hey! There's a boat!

Man: It's coming fast!

Man: No, no, no, no! Don't sink us!

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

Man: Let's go! Quickly go!

Narrator: 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.

Rob Buchan: We reached 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

in the right motions.

Roberts: And they have a large net

hanging down the side of the boat,

and they said, "We're going to come alongside,

we'll be on the 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.

Narrator: 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 more misery.

They're buffeted by an enormous gale

for the rest of their long journey back to Aberdeen.

Through their skill and against all odds,

Cedric Roberts and Lionel Sole

have saved the lives of all on board.

Roberts: I must admit, at the time I did think

that was it, we were going to die.

Sole: 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 that was going to be it.

Narrator: But the day after the crash,

they find their account of what caused the accident

under question.

Jim Ferguson: Lightning, notionally at least,

should not affect the very powerful North Sea helicopter.

Tony Jones: This is the first time

I can recall a lightning strike

having ended up with this kind of conclusion.

Narrator: The experts are skeptical of the pilots' story.

No helicopter is known to have crashed into the North Sea

because of lightning.

Perhaps there had been some mechanical failure.

There are even rumors 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.

A day after the accident,

the Stadive is 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 on board 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.

Ed Trimble: 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

had been dangling over the side of the pylon

as the helicopter ditched,

and therefore detached at some point between the ditching

and where we had caught up with the main wreckage.

Narrator: Keeping the Stadive going

would be costly.

Ed Trimble calls his boss.

Trimble: He was fairly skeptical of our chances.

He asked what I thought our chances were

of finding the tail rotor,

and I, being an eternal optimist,

I said "80%,"

to which he replied, "I think you'd be very lucky

if you've got a 10% chance

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

Narrator: Ed Trimble stays up all night,

relentlessly monitoring the underwater cameras.

Trimble: I didn't want to be in a situation

where we would have missed any evidence of further wreckage

and, in particular, any parts of the tail rotor assembly.

Man: Go get yourself a coffee, Eddie.

Trimble: By the time 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 ten minutes

when I suddenly heard

these tremendously excited shouts from our team.

Man: Yes! Eureka! We found it!

Trimble: 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.

Narrator: 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.

John Hardwick: 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.

Trimble: 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.

Narrator: This home video of the tests

was made 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.

Sole: 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.

Narrator: 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 3 million passengers fly to the oil platforms.

Sole: The helicopters we fly

are certified to the highest standards.

It's the same as you'd get on a major airliner

flying transatlantic.

So we had no reason to believe

that any lightning that we'd encounter

would do any severe damage to the helicopter.

Narrator: Ordinary lightning wouldn't.

But this wasn't ordinary.

Miller: 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.

Narrator: 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.

Roberts: On that particular day

there was very little in the way of indication

that there was any significance in these clouds.

Sole: We were 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.

Roberts: 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.

Narrator: 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 over the whole of 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 fiberglass blades--

then the normal material for helicopter rotors.

But in the 1980s,

plane makers began using composite materials,

like carbon fiber,

which were lighter and stronger.

In particular,

they began making the rotor blades

out of carbon fiber instead of fiberglass.

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 fiber,

composite blades have a metal anti-erosion strip

glued on to protect the edge.

That's where the trouble starts.

Hardwick: 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.

Narrator: 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 3.5 ounces 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 on board 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.

Sole: We've lost the tail rotor!

Roberts: Tail rotor's gone!

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

Things at that point were really very, very worrying.

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 a hundred feet, I pulled 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 leveled the helicopter,

the wave came up, we sat on the top of it,

and we went down.

And it was one of the best landings I've ever done.

But that was luck more than judgment.

Narrator: As bad as it was, it could have been worse.

The two hydraulic pipes

connecting the assembly to the helicopter did not break.

Trimble: These two small-diameter pipes

had held the mass of the gearbox and tail rotor assembly,

dangling over the right side of the pylon.

Narrator: Without the weight of the rotor assembly,

the helicopter would have tipped forward.

Trimble: Had that tail rotor gearbox and tail rotor assembly

completely separated from the helicopter,

then all 18 lives would have been lost

because the helicopter would have pitched down irrecoverably

and gone into the North Sea.

Narrator: The investigators found the answer

to the mystery of a helicopter crash.

But they stumbled across a bigger problem--

one that affects every air traveler.

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 fiber blades

that made them vulnerable.

The tremendous heat created

where the carbon fiber 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 fiber mixed with other materials.

Increasingly, aluminum is being replaced with carbon fiber.

The A380 Airbus, for instance, has over 20%.

What would happen

if these planes encounter a monster lightning strike?

This was the investigators' biggest concern

arising from the Super Puma accident.

The findings were unexpected

and treated with some skepticism.

Though the tests indicated that an unexpected 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.

Trimble: I thought that the reaction was poor.

There seemed to be a real reluctance on their behalf

to accept the evidence.

Narrator: If Britain's air crash detectives are right,

there is a real concern facing air travelers.

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 improved.

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.

Buchan: Now when I fly in a chopper,

especially in the wintertime,

if it's going to be buffed about with 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 here 25 years later,

still earning a living.

Narrator: The crash of 56 Charlie

was a hair-raising incident

that could have easily ended in tragedy.

In the winter of 1995,

the skill of captain Ced Roberts and first 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.

Roberts: Although we received a number of awards

after the incident 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."