All language subtitles for Air Disasters S18E02 The Heathrow Enigma 1080p PMTP WEB-DL DDP5 1 H 264-maldini_track3_[eng]

NARRATOR: January 2008, the
Boeing 777 is the gold standard

for commercial aviation.

For more than 10
years, the plane

has logged 2 million flights
without a single major

accident, but less than 1,000
feet above London's Heathrow

Airport, all that changed.

Hey, I can't get
power on the engines.

What do you mean?

It's not giving me power.

This can't be happening.

I thought if I
don't do anything,

then everybody will die.

Mayday.

Mayday.

Speed bird, speed bird.

NARRATOR: Whatever brought
down one of the world's most

technologically
advanced airplanes

can't be found at
the crash site.

And they had the pilots.

They had the passengers.

They had the aircraft.

They had everything there
except the thing that caused it.

That had disappeared
as if by magic.

WOMAN: Ladies and gentlemen
we are starting on our coach--

We lost both engines.

WOMAN: Put the mask
over your nose.

Emergency dispatch.

Mayday, mayday.

WOMAN: Brace for impact!

MAN:

MAN: He's gonna crash!

NARRATOR: British Airways
Flight 38, a 10 and 1/2 hour

journey from Beijing to London.

Captain Peter Burkill has made
this trip many times before.

I was operating
that really a lot.

It was one of my
favorite flights

because it was daylight.

You could see the views the
whole way along the route.

NARRATOR: Burkill and
first officer John

Coward both have
thousands of hours flying

the 777 under their belts.

PETER BURKILL:
It's a joy to fly.

She handles really well.

She's got modern equipment.

The computers are easy to use.

She's got the range, the
ability to do short haul

as efficiently as long haul.

NARRATOR: For these two as for
many pilots, a day in the job

consists of sitting in
the cockpit for long hours

as computers fly the plane.

Powered by two massive
Rolls Royce engines,

the Boeing 777 is one of the
safest planes in the industry.

Nick Harris is flying back to
London after a business trip

to China.

The good thing was that
it seemed to me that we were

coming in early into Heathrow.

I was looking forward
getting home to the family.

NARRATOR: Flight
38's destination

is Heathrow Airport, one of the
busiest international airports

in the world.

Nestled in the southwest
corner of London,

it's bordered by
the A30 motorway.

People who live in the nearby
neighborhood of Hounslow

are well accustomed to the sound
of jets taking off and landing.

The area is tightly packed
houses come into distant view

for British Airways Flight 38.

The autopilot is in
control as the crew

lines up with runway 2-7 left.

As it nears the
ground, the plane

is buffeted by some high winds.

Just a little turbulence.

NARRATOR: It's the first wrinkle
in an otherwise smooth journey.

It's not me.

That's the auto throttles
doing their thing.

PETER BURKILL: We were picking
up wind gusts for about 20

to 30 knots, and we were fully
aware that the auto throttles

would be able to cope
with that so they'd be

moving up and down quite a lot.

You might want to
keep the autopilot on

a little longer than usual
to let the wind calm down.

Will do.

NARRATOR: In turbulent
weather, the autopilot

can make faster
adjustments than the pilots

to keep a plane level.

1,200 feet above the ground--

You have to turn
that off for now, sir.

Sure.

Thank you.

NARRATOR: Two minutes
before landing, Coward

takes over flying the plane.

You have control.

NARRATOR: Just as the
two pilots had planned.

I have control.

PETER BURKILL: I had
a few seconds to spare

before clearance to
landing, and I was

just tidying up my map charts.

Speedbird 38, prepare
to land 27 left.

Clear to land 2-7
left, speed bird 38.

PETER BURKILL: I remember
looking out to see

if our gate was available.

500 feet.

500 feet.

Stable.

Well, sort of--

NARRATOR: Suddenly,
there's a problem.

Hey, I can't get
power on the engines.

It's not giving me power.

What's going on?

What do you mean?

PETER BURKILL: I was looking
at the engine instruments,

and they didn't make sense
to me because we were asking

for full power but the
engine instruments were

not giving us any power at all.

What's going on?

NARRATOR: Flight 38 is crippled
in the worst way imaginable.

It looks like we have
double engine failure.

NARRATOR: With neither engine
providing enough power,

the jet won't make
it to the airport.

With 152 people on
board, Flight 38

is falling toward
London with only seconds

until it hits the ground.

PETER BURKILL: This
can't be happening.

This is one of the most
modern jets in the world.

NARRATOR: In the cabin
there's no indication

that anything's gone wrong.

NICHOLAS HARRIS: On
approach to land,

everybody seemed
relaxed in the cabin.

We're just looking
forward to landing.

Airspeed low.

Airspeed low.

Airspeed low.

Airspeed low.

PETER BURKILL: And now I
was looking at impact point.

I could see a set of buildings
around the hat and cross

area and a petrol station.

I just knew if we
were hitting those,

then it was certain
100% fatalities.

That point I felt the weight
of my four bars on my shoulder.

I am the captain, if
I don't do anything,

then everybody will die.

NARRATOR: This
close to the ground,

Burkill doesn't
have many options.

He could take back control
of the plane from Coward

but doesn't think
that's the right move.

First decision really
was to not take control.

I remember looking over at John.

He was still flying
the plane well.

Good.

He's doing a good job.

He's doing what
I need him to do.

NARRATOR: Burkill knows that
even if they manage to clear

Hounslow, the jet
could still smash

into the busy A30
motorway or the antennas

at the edge of the airport.

PETER BURKILL: I thought
about raising the gear.

That's the biggest drag
on on a commercial jet,

but I needed the
gear to crash on.

We were going to impact,
and that was going to take

the brunt of the impact.

So I had to leave the gear down.

NARRATOR: With a crash imminent,
Burkill has only one move left,

but it comes with enormous risk.

PETER BURKILL: I knew who
I had about 15 seconds

to make a huge decision.

I needed to get past
those buildings.

It was obvious to me that I
needed to raise the flaps.

NARRATOR: Retracting the flaps
will reduce drag but also lift.

The plane will fly
further but drop faster.

Burkill must determine
which is more important.

I want her to discuss
it with the crew,

but this was all in
a matter of seconds.

I remember holding that lever
for a fraction of a second.

NARRATOR: He hopes
this move will help

his plane avoid catastrophe.

The effect was immediate.

NARRATOR: Now Burkill
makes the announcement

every pilot dreads.

Mayday.

Mayday.

Speed bird, speed bird.

It was hard, very hard.

I remember the couple of
impacts and the noise.

Good God.

The landing was hard.

Just a huge bang.

The noise, bits falling
off the ceiling.

Then I also became a
passenger because we were now

in an uncontrolled aeroplane.

We were sliding
along the ground,

and I didn't know what we
were going to hit next.

And then I thought
about my wife and kids,

and I said goodbye to them.

The lights went out.

I could hear the
wreckage breaking up.

And then we stopped.

When we actually
stopped, I was surprised

that I was still there.

And then I look around
the flight deck,

and I was more surprised
to see that all three of us

were unscarred.

Everybody stay seated with
your seatbelts fastened.

PETER BURKILL: And I quickly
became the captain again.

NARRATOR: The crew
switches off the fuel--

APU fire switch.

NARRATOR: Hydraulic and
electrical systems--

Control switches, cut.

Checklist complete.

PETER BURKILL: I then had
to look after my survivors.

And I thought 20% were dead
because this aircraft was

broken up.

This is an emergency.

Evacuate.

Evacuate.

NICHOLAS HARRIS:
The air stewardess

then took control completely.

Everybody unfasten your--

NICHOLAS HARRIS: As she opened
the door, I smelt the fuel--

We should hurry.

NICHOLAS HARRIS:
And realize that we

need to get off this aircraft.

NARRATOR: The big
danger now is fire.

Having survived the
landing, passengers

could be killed if flames
sweep through the jet.

Jump.

Jump.

I left all my luggage and
just got myself down the slide.

Jump.

Let's get out of here.

I went through the galley and
checked the right hand aisle,

and I was surprised
to see nobody there.

NARRATOR: Despite Burkhill's
fears, there are no casualties.

Outside in the cool January
air, the scale of the disaster

is clear.

The right wheel
had actually been

ripped off during the impact.

The engines were--
were just sad.

They were ripped apart.

The cowlings were--
were ripped off,

and the engines
were half buried.

It wasn't an aircraft anymore.

I now start to
realize that we've been

involved in a major accident.

I saw the damage to the
undercarriage and to the wing.

NARRATOR: The plane narrowly
missed the A30 and the antennas

at the foot of the runway.

It could have been
total devastation.

The impact had been on anything
other than soft mud and grass,

the likelihood of
a fire was immense.

NARRATOR: Given the
amount of damage,

it's incredible that only
47 people were injured.

I felt quite lucky
that I was still alive.

It was quite a surreal feeling.

NARRATOR: Investigators have
some early hunches about what

caused the engines to fail.

They also have plenty of clues,
but a key piece of evidence

is already missing.

NARRATOR: The crash of
British Airways Flight 38

dominates the news.

It's the most serious accident
at Heathrow in 30 years.

Heathrow Airport is
a very busy airport.

It is the main
airport in the UK,

so anything that happens
in Heathrow Airport

immediately hits the media.

NARRATOR: More significantly,
the 777 is one of the world's

most modern and reliable jets.

The accident unsettles
the airline industry.

The 777 is as safe
as an aeroplane can be.

It had such a superb
safety record.

What on Earth happened?

You don't like not knowing
whether it might happen

to the rest of your fleet.

NARRATOR: Investigators
quickly arrive on the scene.

Phil Sleight is
the lead engineer

for Britain's AAIB, the Air
Accidents Investigation Branch.

PHILIP SLEIGHT: When you
first approach an accident

site like this, the
first thought you've got

is, where do I start?

The plane landed about 1,000
feet short of the runway.

The landing gear is pushed
up through the wings.

The nose landing gear collapsed.

NARRATOR: Just hours after the
crash, investigators interview

the crew.

Captain Peter Burkill
has a firsthand account

of what happened.

I think I wanted
to talk about it

because I knew of the
innocence of the whole crew.

This isn't our fault. We
didn't do anything wrong.

But the engines weren't
giving us any more power.

Well, it looks like we
have double engine failure.

We tried to give them
more power manually,

but there was nothing.

NARRATOR: Burkill explains
that something had caused both

of the jet's Rolls Royce engines
to roll back at the same time,

robbing the aircraft of power.

PHILIP SLEIGHT: When
you hear something

of a double engine failure, you
start looking at what's common.

What could cause both engines
to fail at the same time?

So our first thoughts were that
it may have run out of fuel.

NARRATOR: A fuel
shortage is rare,

but it has happened before.

In 1983, a Boeing
767 ran out of fuel

flying over central Canada.

A mistake in converting between
and imperial measurements

left the plane with much less
fuel than the crew thought.

At 26,000 feet, they lost
power to both engines.

The captain was able to glide
the plane to a safe landing

at an abandoned airbase.

In the case of Flight
38, this theory

is immediately questioned.

PHILIP SLEIGHT: Jet
fuel has a certain odor.

Anyone who has worked
with an aircraft

will know the distinctive
smell of jet A1 fuel.

There was certainly a lot of
fuel leaking from the aircraft

from the rupture to the
bottom of the engines

when we arrived on site.

NARRATOR: A check of
the plane's dipsticks

confirms two of the tanks
did in fact have fuel.

PHILIP SLEIGHT: So
we knew that there

was plenty of fuel on
board this aircraft

to complete the flight.

NARRATOR: There remain several
other possible explanations

for such a loss of
power, and investigators

must tackle them all.

There is great confidence
that the mystery can be solved

as any and every piece
of evidence investigators

could ever want is
readily available.

They have access to the pilot--

I have control.

NARRATOR: The crew and most
importantly the entire plane.

PHILIP SLEIGHT: We were quite
fortunate to have the amount

of data that we had
on this aircraft

because the aircraft
remained intact.

We were able to interrogate
lots of computers

and also get lots of
data from the recorders.

Additionally, we had data
external to the aircraft

such as radar data and also the
radio transmissions as well.

NARRATOR: Mark Ford retrieves
the plane's flight data

recorders which promise to give
Investigators important clues.

He has another resource, the
QAR or quick access recorder.

While the black boxes are
in the rear of the plane,

the QAR is a data
recorder in the front

used mainly for diagnostics.

MARK FORD: It does have an
advantage over the flight

recorder though in that it
has a greater memory capacity

and can record
additional parameters

over and above those available
on the flight recorder.

You can recover the
data from a quick access

recorder within a matter
of minutes in some cases.

NARRATOR: Speed, altitude,
control settings,

cockpit conversations.

In all the various
recorders have preserved

1,400 different
pieces of data, which

should help the
investigators close the case.

But when they study the QAR
what they find is chilling.

MARK FORD: The quick
access recorder

data stopped about 45 seconds
prior to the accident itself.

Initial thoughts were that
there was an electrical problem

possibly that had affected
not only the QAR but possibly

the engines as well.

NARRATOR: Pilots don't
directly control the 777.

Instead their inputs
are sent to a computer.

Those signals are then relayed
to the engine's flaps and

other systems on the aircraft.

Pete, I can't get
power on the engines.

NARRATOR: A massive failure of
a plane's information systems

could explain why the
engine stopped working.

Perhaps the computers
that control them froze.

Farnborough is home to the AAIB.

The flight data recorder has
been sent here for analysis.

An electrical problem would
be recorded on this device,

but interpreting the
information will take some time,

time investigators don't have.

There are hundreds of
777s landing every day.

They need to find answers
before whatever brought

down Flight 38 strikes again.

While they wait authorities
turn their attention to the fuel

recovered from the ruined plane.

A bad batch of fuel could have
deprived the aircraft of power

just when it needed it most.

BRIAN MCDERMID: A fuel
can be contaminated

in many different ways.

It can be particle
contamination.

It can be biological
contamination,

and they can get into
filters to restrict the flow.

PHILIP SLEIGHT: We took several
samples from various points

within the fuel system so
not only from the fuel tank

itself but also from
remnants within fuel lines

and also within various
fuel components.

BRIAN MCDERMID: We managed
to trace the fuel back

through the documentation to a
shipment of jet A1, which came

from South Korea, and that
was shipped across in a tanker

to China and was
then transported

by pipeline to Beijing airport.

We compared it with over
1,200 other batches of fuel

in the UK, and it came
out to be very good.

NARRATOR: Investigators next
consider the possibility of

a blockage in the fuel tanks.

BRIAN MCDERMID: When
we're in the fuel tanks,

we did find a few
small articles.

One of them was a red scraper.

NARRATOR: The items were likely
left over from when the plane

was built seven years ago.

Obviously it's
not ideal to find

anything within a fuel tank.

We obviously looked
at to see whether this

would have had an effect on
the fuel flows of the engines.

The items were so
small, they would

not have caused a restriction.

NARRATOR: As the search
for answers continues,

a puzzling find surfaces.

Less than three years
before the Heathrow crash,

another 777 suffered a
serious mid-air problem.

After taking off in
Perth, Australia,

a Malaysian passenger jet was
climbing through 38,000 feet

when suddenly the plane's
autopilot pitched the nose up

and climbed steeply.

Calamity was only
averted when the pilot

took manual control of the jet.

They did manage to get
it safely back to base.

The investigators
established that this

was a computer problem.

NARRATOR: British
aviation authorities

consider that the
electronic brain

of one of the world's most
reliable jets might be faulty.

The Malaysian
Airlines aircraft was

really quite an unnerving one.

The investigators sort of
pulled out the files on it

and started looking over it
to try and get some clues.

PHILIP SLEIGHT: Did
we have a problem

with the electronic
control system causing

the engines to roll back?

NARRATOR: If flaws are found
with Flight 38's computers,

it means 777s around
the world could

all be disasters in the making.

This thought hangs
heavily over the industry.

When the readout of the
plane's flight data recorder

is conducted in
Farnborough, investigators

learn that the crash could
have been much worse.

There was very little I
could actually have done.

It looks like we have
double engine failure.

There was only 30 seconds
between when they were fully

aware of what was going on--

Air speed low.

PHILIP SLEIGHT: And the
accident was inevitable.

NARRATOR: Records show that
soon after the engines failed,

the plane started falling
faster than 1800 feet a minute,

a very steep descent.

But lack of power
was only one factor

working against the crew.

They had extended
their flaps on descent.

It helps control the
plane at lower speeds

by increasing lift, but the
extended flaps create drag,

which slows the plane down.

It takes more power to keep the
plane flying with a wider wing.

Air speed low.

PETER BURKILL: I needed
to raise the flaps.

I knew that by raising
it one notch to flap 25

would be the right thing
to do to reduce the drag.

That's what I had to do.

And what he did here
gave them a few extra feet.

Had the flaps been
left at flaps 30,

the aircraft would have
struck the ground just

before a set of ILS antennas.

NARRATOR: The plane then would
have slammed into the antennas,

sustaining even more damage
and increasing the chances

of serious injuries.

For their efforts, Burkill and
his team are considered heroes.

PETER BURKILL: Flying
is about teamwork,

and we had an outstanding team.

NARRATOR: There is no
doubt without the flight

crew's actions,
Flight 38 landing

would have been a catastrophe.

Now the recordings--

NARRATOR: As they continue
examining data from the flight

data recorders--

Continue right until
the moment of impact.

NARRATOR: Investigators are
no closer to solving the case.

MARK FORD: Analysis
of the flight recorder

didn't identify any particular
fault with the aircraft

electrical system that
would have resulted

in both engines rolling back.

NARRATOR: They are at least able
to determine why no data was

found on the quick access
recorder for the last 45

seconds of the flight.

It's not an electrical
fault as they first feared.

MARK FORD: The 45-second
delay in the QAR recording

was a result of the
fact that the QAR

doesn't record in real time.

It buffers the data
and then will record

approximately 45 seconds later.

NARRATOR: With all the
information from the plane's

various data recorders
now collected,

investigators have a precise
picture of what happened.

The jet was on the
proper course as it

made its approach to land when
things went horribly wrong.

PHILIP SLEIGHT: At 720 feet,
the right engine rolled back.

7 seconds later the,
left engine rolled back.

The autothrottle attempted
to command greater thrust.

It's not me, that's
the auto throttle.

But the engines
didn't respond.

I can't get power
on the engines.

NARRATOR: Well, electrical and
computer problems are ruled out

as causes of the crash.

The flight data recorders
do point investigators

to the likely source
of the problem.

Two most
significant parameters

from the quick exit recorder
with the fuel metering valves.

Both those valves
indicated that they had

opened the fully open position.

NARRATOR: The plane's computers
were calling for as much fuel

from the tanks as possible.

The valves were fully open,
but not nearly enough fuel

was reaching the engines.

A plane with plenty of
fuel and a working computer

system still crash
landed, and investigators

can't determine why.

They focus on the weather
on the day of the accident.

PETER BURKILL: It was a very
cold air mass over Siberia,

so we were aware of
the cold conditions.

But the flight was expected
to be smooth and also quick.

NARRATOR: The plane's path
took them high over Russia.

The outside temperature
went as low as -74 degrees

Celsius, -101 Fahrenheit.

It's a potentially
dangerous temperature

if not monitored closely.

With cold air masses,
you have to be very

aware of the fuel temperatures.

PHILIP SLEIGHT: When fuel starts
to freeze, it produces wax.

As the fuel temperature
drops, the wax

becomes greater
within the fuel itself

until it comes to a point
where it can no longer flow.

PETER BURKILL: We have
a fuel temperature gauge

on on the flight deck, which
is monitored at all times,

and I personally look at that
every time I do a fuel check

which minimum is once an hour.

Basically you don't
want to get it

below -34 degrees centigrade.

NARRATOR: While they were
cold, the temperatures never

dipped into the danger zone
where the fuel could wax

and clog the
system, and the fuel

temperature increased
significantly

as the jet approached London.

PETER BURKILL: We were
coming through 20,000 feet,

and I remember seeing
-20 degrees centigrade.

So it had already
started to warm up.

NARRATOR: Another potential
cause of the crash

is ruled out.

Investigators are now running
out of possible explanations.

And the expectation
from the media

and also from aviation
experts was that we would

have the answer within days.

REPORTER: But there
was no comment today

about the ongoing investigation.

PHILIP SLEIGHT: It very quickly
became apparent that that

would not be the case.

DAVID LEARMOUNT:
They had the pilots.

They had the passengers.

They had the aircraft.

They had everything there
except the thing that caused it.

That had disappeared
as if by magic.

NARRATOR: They turned
to a failure of the fuel

delivery system as a culprit.

To prove it was responsible,
they need to pinpoint anything

out of the ordinary about Flight
38 journey on January 17, 2008.

PHILIP SLEIGHT: It's a
daily flight operating

from Beijing to Heathrow.

We wanted to work out what
was unique about this flight.

Why this flight in particular?

If you've got a very puzzling
incident like the 777 accident

at Heathrow, you're going to
mine all the data you can.

Just put them
over there for now.

PHILIP SLEIGHT: So we
approached many operators

to obtain some data
of previous flights

so that we could
then do a comparison.

NARRATOR: Flight data is
collected from companies

around the world.

PHILIP SLEIGHT: And
we had something

like 144,000 flights in all.

NARRATOR: But it will
take months of work

to analyze this enormous
volume of information.

To study Flight 38's
fuel system more closely,

huge sections of it are
brought to the AAIB hangar

and reassembled.

BRIAN MCDERMID: It allowed us
to basically just sit there

and look at it and to
brainstorm and come up

with ideas as to what
might have caused it.

NARRATOR: McDermid and his
team consider all possibilities

from design flaws to
a malfunction specific

to this aircraft.

The examination comes up empty.

We carried out an
exhaustive and very

thorough inspection and
testing of the fuel system,

and we find nothing wrong.

NARRATOR: Frustrated,
investigators

are at a dead end.

PHILIP SLEIGHT: We kept
going through this cycle.

We kept going back over
what we'd done before.

Had we'd missed something?

And every time we
went back over,

we kept coming back to no.

NARRATOR: There was no trouble
with the plane's computers,

it had plenty of fuel and no
problems with the fuel itself,

but somehow when
it was most vital--

Mayday, mayday--

NARRATOR: The engines didn't
get the fuel they needed.

The AAIB detectives have
run out of suspects.

DAVID LEARMOUNT: There
was no clear explanation.

Nothing that you'd seen before--

It's not giving me power.

In any airplane, let alone a
777, could have explained this.

NARRATOR: Now they turn
away from the clues

they have to those they don't.

Phil started coming out
of a mantra, which was

a quote from Sherlock Holmes.

PHILIP SLEIGHT: Whatever is
left, however improbable,

must be the cause.

Has to be.

PHILIP SLEIGHT: In this case,
we always keep coming back

to what's there,
what could have been

there, that's not there now.

And we come back to ice.

Suspicion that the cause
of the accident was ice

grew stronger and stronger.

NARRATOR: But
investigators are faced

with a nearly impossible task.

How can they prove that ice
had brought down the plane when

the evidence they
need would have melted

by the time they arrived?

to work with
engineers at Boeing,

the company that built the 777.

If ice brought down Flight 38,
they need to prove how and why.

PHILIP SLEIGHT: We took the
pipes from the right side

of the fuel system, and those
pipes and those couplings

were used on the
test rig at Boeing.

NARRATOR: Ice in the fuel
lines has long been a concern

for jets of all kinds,
but decades ago, engineers

found an ingenious way to
deal with the ice forming

in the fuel of passenger jets.

The heart of the
system is the fuel

oil heat exchanger or FOAG.

Cold fuel runs
through thin tubes

which are surrounded
by the hot oil

used to lubricate the engines.

The purpose of
a fuel heater is

to heat the fuel up to prevent
icing of the delicate fuel

control system.

The FOAG is designed to
prevent exactly the problem

Investigators suspect
crippled Flight 38,

but it's also a potential
bottleneck in the system.

BRIAN MCDERMID: During
the fuel testing,

we were looking to
establish where we could get

a restriction that would
restrict the fuel flow to 6,000

per hour, and the only
place that we could get such

a restriction occurring
was on the face

of the fuel oil heat exchanger.

NARRATOR: Investigators
have to prove three things.

First, that substantial
amounts of ice

can accumulate inside
the fuel pipes.

Second, that the ice can
suddenly be released.

And finally prove that it can
block a device specifically

designed to melt it.

BRIAN MCDERMID: We use
different methods of controlling

the environment around the
pipes that range from dry ice

to cold fuel and to hot air
to simulate the environment

around the pipes
that the aircraft

experienced during the flight.

NARRATOR: After each
fuel cooling test,

investigators look
inside the pipes for ice,

but they can never
get much ice to form,

let alone block the fuel lines.

And the fuel temperature
was -30 degrees centigrade.

Very little ice would stick to
the inside of the fuel pipes.

NARRATOR: Investigators
know the temperature

on the accident flight
didn't get much colder,

so how had the ice formed?

PHILIP SLEIGHT: We still hadn't
answered the question of where

does the ice come from in
the first place and indeed

was it ice or was
there something

else that we've missed.

NARRATOR: Surprisingly, when the
fuel temperatures are warmer,

the breakthrough arrives.

If you have water in the
fuel, then that water will

freeze and form ice crystals.

And then when the temperature
gets to about -20 degrees

centigrade, then
those ice crystals

will start to stick together--

would also stick to the
inside of the pipes.

NARRATOR: Below -20 degrees
Celsius, minus 4 Fahrenheit,

any ice crystals in the
fuel are too cool to attach

to the pipes, but
in the sticky range

20 to -8 degrees Celsius,
minus 4 to plus 17 Fahrenheit,

slushy ice forms and sticks to
the sides of the fuel pipes.

So when we demonstrated
that ice could actually

build up and grow onto the
walls of the fuel pipes,

there was a certain
amount of surprise

as to how much
could actually grow.

And now we're
getting somewhere.

Well, the question
for us at this stage

was how could the ice
come off the pipes.

NARRATOR: Investigators think
they have the smoking gun.

All right.

NARRATOR: But they still can't
prove how a small bit of ice

could bring down a
$200 million plane.

They continue
analyzing thousands

of comparative flights to see
what made Flight 38 unique,

but after seven months, they
still can't crack the case.

MARK FORD: From 35,000
Rolls Royce powered flights,

it was less than 1% who
had the same features

as the accident flight.

NARRATOR: Then on
November 26, 2008, more

than 10 months after the crash.

The importance of
finding an answer

is underscored when the
elusive culprit strikes again.

Another 777 runs into
trouble 39,000 feet

above the United States
when one of its engines

simply stops working.

Fortunately in that
case, the engine recovered,

and the aircraft landed
safely at Atlanta.

NARRATOR: Even though it
didn't result in an accident,

it reinforces
concerns that there's

a potentially dangerous flaw
on every 777 around the world.

The incident captures
the attention

of the British Airways
crash investigators.

DAVID LEARMOUNT:
The Delta Shanghai

flight really was investigated
with huge interest.

The engines were Rolls Royce
engines of the same type.

So they immediately went looking
for evidence of same problem.

NARRATOR: And, in
fact, they do find

important similarities
between the Delta airliner

and British Airways Flight 38.

PHILIP SLEIGHT: The
aircraft had operated

a long sector from Shanghai
in China to Atlanta.

The fuel temperatures were
within the sticky range

that we are defined
during the research.

We were able to see that
the reaction of the engine

was very similar to that
of the 777 at Heathrow.

NARRATOR: Later examination
of the Delta flight

shows no evidence of any
electronic, mechanical, or fuel

system problems, strongly
suggesting that the culprit was

indeed ice.

When we heard about
the Delta flight,

we were more convinced
than ever that we

were on the right track.

Seattle continue their testing.

It's been a year
since the accident,

and the problem hasn't
been found or fixed.

They've run hundreds
of simulations

and spent millions of dollars.

They still can't get the
ice in the fuel lines

to clog the fuel
oil heat exchanger

and cause the kind of blockage
that brought down Flight 38.

PHILIP SLEIGHT:
We came to a stage

where we had not actually
come up with what

had caused this accident.

This time, the media and
also the general public,

there was a bit of
unrest as to why we had

not yet come up with an answer.

NARRATOR: Industry
pressure to resolve

this case is intensifying.

Investigators still need to know
what made Flight 38 different

from thousands of
others that had

flown under similar conditions.

To find out, they retrace every
moment of Flight 38's journey.

The voyage from Beijing involved
a gradual climb, a steady

cruise, and a gradual descent.

The fuel temperatures
fell and rose

accordingly, causing ice to
accumulate in the fuel lines.

That ice posed no danger
unless it was released.

Now investigators
study the fuel flow

and find that it was kept
steady for most of the flight.

The autopilot maintained
constant speed and low power

for hours, never demanding an
abrupt increase in engine power

until just before they
reached the runway.

PHILIP SLEIGHT: The
approach into Heathrow

was quite a turbulent approach.

And the engines were demanding
various levels of thrust power.

It's not me, that's the auto
throttles doing their thing.

PHILIP SLEIGHT: And there were
four changes in fuel flow, one

of which was a
very high fuel flow

of around about 12,000 to
13000 pounds per hour demanded.

NARRATOR: A closer review of
the American, Delta flight

reveals that its
engine rolled back

under the same circumstances,
a sudden demand for power

after a long period
of consistent speed.

Investigators are
now set to duplicate

these precise conditions.

They hope that by
reproducing the moments just

before landing, which was the
only part of the flight where

the crew suddenly
required more power,

they may finally get the
answer they're looking for.

The problem that
we were looking at

is very, very
difficult to replicate,

and during what was
one of the last tests,

we actually managed to get
all the elements together.

NARRATOR: After
simulating running engines

at constant speed, investigators
increased the power.

BRIAN MCDERMID:
We allowed the ice

to accumulate for
three hours, and then

the flow rate was increased.

NARRATOR: What happens next
breaks the case wide open.

In Boeing's Seattle lab,
investigators sudden demand

for more engine power
causes the fuel pressure

downstream of the fuel oil heat
exchanger to drop dramatically.

And when investigators
examined this vital component--

BRIAN MCDERMID: We
then saw that ice had

formed across the face of it.

We did it.

NARRATOR: Soft ice
that had formed deep

inside the fuel lines broke
free when the pressure

was abruptly increased.

It restricted the flow
of fuel to the engines.

Investigators have finally
found the Achilles heel

hidden deep inside the 777.

The tubes that bring the
fuel through the FOAG

jut out just above the
container of hot oil.

It's just a few millimeters
but is enough to prevent

the ice from coming in
contact with a hot surface

below and melting.

Now the ice doesn't
totally restrict

the fuel flowing through it.

It has some porosity.

So the fuel will
continue to flow through,

but the flow rate is much
lower than it should be.

NARRATOR: In all of the tests,
only one gave investigators

the result they
were looking for,

the one that exactly matched
the journey of Flight 38.

While the plane flew over
Russia, water in the fuel

turned to ice.

At -20 Celsius
minus 4 Fahrenheit,

it began to build up along
the inside of the pipes.

The steady speed of the aircraft
ensured this accumulation

was never interrupted.

Then as the plane
approached Heathrow,

turbulence resulted in
the first demand for power

since much earlier
in the flight.

It's not me.

That's the ultra throttles
doing their thing.

You might want to keep the
autopilot on a little longer.

Then things cascaded
into a serious problem.

The gushing fuel washed the
ice through the fuel system

until it built up against
the face of the FOAG

with disastrous results.

Pete, I can't get
power on the engines.

It's not giving me power.

NARRATOR: Facing a threat
no one knew existed--

Mayday, speed
bird, speed bird.

NARRATOR: The pilots didn't have
a chance to solve the problem.

But why had the
American Delta crew

been able to clear the blockage
while the British Airways

flight ended in
near catastrophe?

It's discovered that
after just a few seconds

of reducing engine power to
idle, the blockage in the FOAG

clears.

But this maneuver was not
available to the British

Airways pilots because they
were so close to the ground.

Soon after the Seattle
tests, Rolls Royce redesigned

the fuel oil heat exchanger.

So what Rolls Royce
did was to actually

remove those protruding tubes,
and you now have a flush face.

And they found that if they
flattened this surface, even

if ice crystals did
form in the fuel,

they'd gold straight down
the holes in the block.

Very, very easy fix.

NARRATOR: Other
aircraft manufacturers

are ordered to ensure
that their systems aren't

vulnerable to the same problem.

Peter Burkill, John Howard, and
the rest of the crew of Flight

38 received the British
Airways safety medal

for their performance
during the accident.

It's the company's
highest honor.

Crew have been presented
with an unprecedented failure,

and they did the best
they could in the time

that they had available.

The crew did as good
a job as they could,

and since they really only
had about 30 seconds to think

about what they were
going to do about this,

they couldn't have done
any better than they did.

NARRATOR: The ice that brought
down one of the world's most

sophisticated airplanes was
gone by the time investigators

showed up.

DAVID LEARMOUNT: Weird thing
about this investigation

was that the culprit
had fled the scene.

NARRATOR: The inquiry
into what happened

consumed thousands
of hours of manpower

and cost millions of dollars.

These people really pulled
out the stops to find out,

and the reason, we have to know.

NARRATOR: With
unrelenting diligence

and a little inspiration
from Sherlock Holmes,

the mystery was finally solved.

PHILIP SLEIGHT: Whatever is
left, however improbable,

must be the cause.