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1954.
And one of the world�s first jet airliners takes off from Italy.
The plane is the ultimate in high-speed luxury travel.
But just 26 minutes into the flight,
it explodes catastrophically.
35 people are dead.
The tragedy stuns a nation.
A team of investigators must solve the mystery
of why this state-of-the-art aircraft disintegrated on a routine flight.
What they discover in the wreckage
will cause a turning point in the history of aviation
and change passenger travel forever.
Disasters don�t just happen.
They�re a chain of critical events.
Unravel the clues and countdown to those final seconds from disaster.
subtitle by chochancuuDuc (hdvietnam) episode: Comet Air Crash
download for free at subscene.com or watch online on my YouTube channel: Shepherd German
Europe, 1954. Throughout the continent, there is a growing sense of optimism.
As the nightmare of WWII begins to fade, former enemies forge new links.
There's a spirit of enterprise.
Civil aviation is booming, boosted by technological advances
made during the conflict.
In just 2 years, the numbers of airline passengers
has nearly doubled.
9:30 am. Sunday, January 10th. Rome airport.
Here, a dozen planes come and go every hour.
On the tarmac stands flight 781 on route from Singapore to London.
The plane is a British-built de Havilland Comet.
It�s a marvel of its day, and the perfect symbol of the new technological age.
The Comet is the world�s first passenger jet,
and it�s having journey times around the world.
The pride of Britain sends a message of superiority
to every aircraft manufacturer in the world.
A dream comes true:
at Hatfield Airport, the Comet, the world�s first-all jet airliner.
Began 3 years ago, the airliner that makes every other passenger plane
out of date, will go into operation within 18 months.
The revolutionary design is based on de Havilland�s hard-won military expertise.
The plane is powered by four Ghost jet engines,
and carries 42 passengers and crew,
at up to 800km/h, almost twice as fast as its nearest competitor.
To help it achieve this staggering speed efficiently,
it flies at the height of up to 12000 meters, where the air is thinner.
Until now, such performance with the preserve
of military jet fighters.
20 months after the launch, there are 17 of these aircraft in service.
9 are owned by the British Overseas Airways Corporation, or BOAC.
And among them is flight 781.
9:40 am. BOAC engineer Gerry Bull inspects the Comet�s under-carriage.
He checks for fuel leaks, tire damage, and marks on the airframe.
He pays attention to
the aircraft�s high-tech
ultra-lightweight aluminium skin. It�s extremely thin
and vulnerable to damage.
We�re looking for its incidental damage, there was nonother sounds like we call
at that stage.
So, my own thought at the time we�re walking away is: we�ve got a clean airplane today.
At 10 pm, Bull completes his final checks.
The flight crew join him.
The captain is Alan Gibson. At 31, he�s one of BOAC�s youngest pilots.
Captain Gibson was, uh, a man of
very good ability, not a person who would
panic about anything, he was, you know, confident.
In Rome airport�s terminal, members of the new jet set enjoy breakfast.
Many are children returning to England for a new school term.
They�re excited about flying on the world�s first passenger jet.
Also on the flight is renowned BBC reporter Chester Wilmot.
He�s returning home after covering a tour of Australia
by the recently Crown British Queen.
Chester is a devoted man with 3 children.
He�s especially close to his 10-year-old daughter Jane, who was born deaf.
She is devoted to him, unaware that he�s one of Britain�s best-loved broadcasters.
10:05am, and the last two pieces of luggage are stored in the hold of flight 781.
The plane will be flying today with
29 passengers and 6 crew members on board.
One of the passengers is 23-year-old Bernard Butler.
Bernard is an electrical engineer who�s been working in Bahrain
to save money for his forthcoming wedding.
His fianc� is Pat Knight.
They�ve been engaged for 2 years and planned to marry in a fortnight.
I�d met to price nice dresses,
all invitations had gone now,
and we�d already received wedding presents. Everything was planned.
Bernard is returning home with a surprise.
He�s picked out the dress for Pat to wear at their wedding.
At 10:18am, all pre-flight checks are complete.
Captain Gibson signs to confirm that everything is in order.
Captain Gibson seemed very relaxed,
also, looking forward to getting home!
Flight 781 is just one of five BOAC services from Rome to London today.
An older generation of slower preperative airliners
make up the other flights.
At 10:19 am, a BOAC Argonaut,
also bound for London, thunders down the runway.
Captain Johnson is at the controls.
At 10:30 am. Eleven minutes after the Argonaut�s departure,
the Comet taxis to the runway. Gerry Bull salutes goodbye.
BA 781, it�s Ciampino control.
Control, this is flight BA 781. We�re cleared for takeoff.
Air traffic control ground permission for takeoff.
1 minute later, the high-tech plane takes to the air.
It�s a sunny day and conditions for flying are perfect.
The journey to London will be exactly 2 hours and 37 minutes.
The gleaming jet will arrive at London airport at staggering two hours
before the propeller-driven Argonaut.
Such speed is so far beyond anything produced by American rivals Boeing and Douglas.
The Comet�s manufacturer de Havilland
expect to dominate this booming market.
Throughout Britain, expectation is high, from Prime Minister Winston Churchill down.
It was
important from British point, you know, to have our aircraft in the air.
And an aircraft was far better than anything else. So it was a booster.
But since the Comet entered service,
20 months ago, there have been 2 accidents, with the loss of 54 lives.
In March 1953, one crashed on takeoff in Pakistan.
Two months later, severe weather was blamed for a second disaster in India.
As both accidents occurred in difficult conditions,
reliability of the Comet is not in question.
At 10:38 am,
flight 781 climbs to an altitude of 11000 meters,
twice as high as any other passenger aircraft.
To achieve this, while allowing passengers to breath comfortably,
the engineer operates a pressurization system from the cockpit.
As the Comet rises, the air pressure inside the cabin is maintained
at the equivament altitude
of 2.5 thousand meters, a level easily tolerated by the human body.
But for some passengers, adapting to this new sensation is difficult.
Soon though, they acclimatize and settle back into their seats for flight.
What they cannot know is that they will never make it into London.
1954. And a state-of-the-art Comet jet airliner
has taken off from Rome, on route to London.
On board are 29 passengers and 6 crew.
As flight 781 climbs,
Captain Gibson received the message from Captain Johnson in a slower Argonaut
that took off a few minutes earlier.
�George How Jig, receiving?�
Each pilot uses the plane�s callsign, �How Jig� for the Argonaut,
�Yoke Peter� for the Comet.
Hey Yoke, can you pass your flight on cloudlets, please?
Now the coordinate is 2000 feet.
- We�ll let you know when we pass through. - Roger, end.
At 10:42 am,
Captain Gibson contacts air traffic control.
The plane will fly Northwest, over the Italian coastline
high above the Mediterranean Sea.
Would you like some pizza?
At 10:51 am. Captain Gibson again radios the Argonaut.
- George How Jig from George Yoke Peter. - George Yoke Peter from George How Jig.
George How Jig, did you get my�
The message ends mid-sentence.
Yoke Peter, Yoke Peter, come in please!
When Captain Johnson gets no response, he contacts Rome airport.
We lost our contact with BA781, and then they seem to disappear. Can you read them?
At 10:56 am,
the airport controller tries to contact the Comet, without success.
They fear something is terribly wrong.
200 kilometers northwest,
on the island of Elba, a group of Italian are repairing their nets.
Among them is 33-year-old Luigi Papi.
As they work, something extraordinary happens.
I felt a break in the air, and then there was a ***,
and I heard a sound like thunder, but it was not like
any thunder I'd ever heard before.
They watch in amazement as flaming wreckage falls from the sky.
At 11:15 am,
air traffic control receives word that a plane
has crashed into the sea off the island of Elba.
It confirms their worst fears.
Gerry Bull hears the news.
The senior engineer said: There�s a bad news, Mr. Gerry.
And I looked him and he said: The Comet�s down.
It�s an emptiness,
you can�t really describe it. That says this, uh,
numbness, you get. And the next reaction, of course is,
is there something I didn�t do?
12 pm, Greenwich Mean Time. Chester Wilmot�s family arrived at Heathrow Airport
in West London
to welcome the BBC reporter home.
Pat Knight arrives with a friend after a 4-hour journey from Nottingham.
She�s looking forward to seeing Bernard again.
It was eleven months since I�ve seen Bernard,
and we�re so excited,
that he was coming to, and I was going to see him.
1200 kilometers away, a small fleet of little fishing boats
heads off the coast of Elba towards the crash site.
At first, we saw nothing.
Then, we saw a flock of seagulls which were packing at something.
So we headed straight for the seagulls, and that was where the plane
had crashed.
It�s a harrowing scene. Bodies and debris
float in the water.
Among the carriage is a white wedding dress.
1:30 pm. Flight 781
is now over an hour late.
Airport staff mark the plane as delayed.
Jane Wilmot keeps a close eye on the arrival board.
Jane suddenly notices that
all reference to flight 781 has been removed.
She decides to ask at the BOAC desk.
Edith Wilmot
is taken to a side room. Her children wait outside.
They still believe their father�s plane is delayed.
is delayed.
Minutes later, Edith returns, visibly shocked
and close to tears.
She tells her children
that Chester is dead.
Jane will never see her beloved father again.
The grave task of informing friends and relatives continues.
Patrice Knight can scarely believe what she hears.
They tell we it�s just come down. They didn�t know whether there were bodies
found or not.
And there was nothing we could do.
In an instant, Pat�s hopes for the future are destroyed.
In Italy, the fishermen begin a gruesome task of recovering bodies.
It was a big shock.
Every time we went near a corpse, you would shout �Come over here,
come over here!�, because they seemed still alive,
their eyes were open. But when we got near,
you could see they were dead.
In total, 35 passengers and crew
die on board Comet flight 781.
15 bodies are recovered.
There are no survivors.
The dead are carried to a small chapel in Port Azzuro.
Local people say prays,
children bring flowers.
The horrific crash is headlined news around the world.
The question on everybody�s lips
is how could the most advanced airliner in aviation history
just fall out of the sky?
Was it a tragic accident?
Or something more sinister?
In 1954, the mysterious crash of the Comet
dominates the thoughts of the British nation.
What could have possibly caused the most advanced passenger plane in history
to disintegrate in mid-air?
Within hours of the crash, a team of experts working for BOAC
begin a technical examination of the Comet fleet.
They must discover if there�s a floor in the design
or a manufacturing fault.
British�s position as the world leader in passenger jet travel
depends on it.
The inquiry that follows will turn into one of the most complex and important
in aviation history.
Now, by going deep into the investigation, we can reveal the critical chain of events
that caused the downing of flight 781.
Paul Withey is an aviation metallurgist.
For 6 years, he started the Comet investigation and is an expert
on this turning point in aviation safety.
Withey knows that with no established protocol for air crash investigation,
it was an epic task.
The difficulties they faced as an investigation team was to develop
a whole new series of techniques for looking into a major air crash,
they had to really invent tests, invent methods and doing things
as they went along.
But Withey needs to be sure that this landmark case
actually did get to the truth. Now, for the first time in half a century,
he will re-examine the vital evidence.
If he discovers their findings are wrong, it will rewrite the history of air crash investigation.
From the beginning, the inquiry team are faced with an enormous challenger.
In 1954, the investigation team had no blackboxes.
They had no flight data recorders, they had no way of
understanding what was going on in the plane at the time of the accident.
Their best clue,
the aircraft itself, lies at the bottom of the Mediterranean Sea.
Without the remains of the plane, the team know they must
unravel the mystery with the flimsiest of evidence.
With little to go on, the press
speculate that sabotage might be the cause of the crash.
These are early years of the Cold War, and there are fears that subversive
Communists may be responsible.
Sabotage, a bomb, and that were came out very rapidly, you know, it was�
it has to be, how did it happen?
A bomb could have been hidden onboard while the plane was taking on extra baggage.
It�s only a theory, but if true,
it would at least eliminate doubts about the safety of the Comet itself.
With a pride and prosperity of the nation
on the Comet�s success, a close eye's kept on the investigation
from the very top:
Winston Churchill himself.
If saboteurs are responsible, the investigators know they must come up
with hard evidence.
They know that flight 781 would have been flying at around 11000 meters
when something caused it to break off and fall from the sky.
The Italian fishermen provide a few clues.
I saw a huge ball of fire
rotating, plunging into the sea.
It left a huge, huge cloud of smoke.
Captain Johnson, pilot of the Argonaut, deepens the mystery.
The radio went dead in mid-sentence. Everything just cut out instantly.
But it�s the victims themselves
that provide the biggest mystery. Within hours of the crash,
Italian pathologist Doctor Antonio Fornari examines the bodies.
Despite Fornari's considerable experience,
he finds a pattern of injuries he has never seen before.
The victims suffered broken limbs
and damaged ribs, injuries sustained after death.
But what confuses Fornari is that many of the bodies
have fractured skulls, wounds he discovers
that were sustained before death.
He finds another puzzling clue: the lungs of almost
the victims are extensively damaged. Many have ruptured
like an exploding balloon.
To top it all, Fornari finds no evidence of a bomb blast.
It�s a strange perplexing picture,
and he�s baffled.
With so little evidence, the investigation
hits a dead end.
Concerned, Prime Minister Churchill summons his advisers and takes an unprecedented step.
Churchill commands the Royal Navy to retrieve the wreckage of flight 781
from the seabed.
His orders are simple: �Endeavour to locate
and salve Comet�.
The task however is anything but simple.
There has never been a salvage operation like it before.
The wreckage lies at the depth of 120 meters
and no one knows exactly where.
Today if there�s an aircraft
crashed in similar circumstances, the blackbox recorders
would help transponders
and would lead investigators, and the� and the recovery teams to the spot
where the aircraft was.
The Navy didn�t have that information.
HMS Wrangler, an anti-submarine frigate, searches an area of 260 square kilometers.
3 salvage vessels are on hand to help. They�re equipped with
the most up-to-date technology,
including an underwater camera and a deep sea observation chamber.
But progress is delayed by bad weather.
Then, on February 12th,
33 days after the crash, Navy experts identify the first piece of the Comet wreckage
on the underwater camera. Divers descend to the seafloor.
Over the next few weeks, small bits of debris
are sent back to England for examination.
Then, comes a major find. A large section of the rear fuselage is located
and brought to the surface.
Meanwhile in London, the Comet fleet sits idol.
BOAC hemorrhages cash at the rate of 50000 pounds per week.
With so much invest in the aircraft,
pressure builds to get the planes back into the air.
On March 23rd, ten weeks after the disaster,
the British government give the airliner the go-ahead to resume service.
At London airport, a Comet airliner about to leave for Johannesburg
taking out extra crew members.
Press and television attend the relaunch.
BOAC chairman, Miles Thomas, gives the Comet a public vote of confidence.
We obviously wouldn�t be flying the Comet with passengers� were we not wholly satisfied
that the conditions are acceptable for carrying passengers
anywhere in the world.
Wreckage from flight 581
arrives in England piece-by-piece. Investigators identify and mark every fragment.
In a hangar, carpenters has built a wooden frame of the Comet aircraft.
As the wreckage accumulates, they wire each piece onto this skeleton.
Now, with the entire Comet fleet back in service, it�s more important than ever
to find the cause of the crash. The lives of hundreds of passengers
depend on it.
April, 1954. While investigators urgently look for clues into the crash
of Comet flight 781,
the British government give BOAC the go-ahead
relaunch their Comet fleet. It�s a terrible mistake.
At 6:32 pm on April 8th, 16 days after the resumption of flying,
a Comet takes off from Rome, bound for Egypt.
14 passengers and 7 crew members are on board.
33 minutes into the flight, the pilot reports that he�s on course flying at 11000 meters.
It�s his final message.
A further 21 people are dead.
The news send shockwaves around the world.
Barely a fortnight after reassuring the public the Comet is safe to fly,
BOAC chairman publicly admits that he was wrong.
Obviously, we cannot
continue to carry the public in Comets until
this disaster is fully explained.
Similarities between the two accidents are uncanny.
Both planes were refueled and checked at Rome
by the same engineers, including Gerry Bull.
You just can�t except that
an airplane�s like this again, it�s gone all the same way, and you've
lost these people again.
Both aircraft were flying at an altitude of around 10000 meters.
Both crashed into the sea shortly afterwards.
It seems there must be a flaw in the aircraft itself.
Again, the British Navy looks for evidence.
They recover 5 bodies along with a few personal effects.
Churchill acts decisively.
He appoints the Royal Aircraft Establishment, Britain�s leading
aeronautical research center,
to investigate.
Heading the inquiry will be Sir Arnold Hall.
Hall has an impressive reputation. He�s a Cambridge scholar,
and one of the outstanding scientists of his generation.
Sir Arnold Hall is a brilliant scientist.
And he�s one of those people who would let the facts speak for themselves
and would make judgements based on facts, not on opinions.
Churchill instructs Hall: the cost of solving the Comet mystery
must not be reckoned in money nor in manpower. But even for a man as qualified as Hall,
it's going to be a tall order.
The second plane to crash rests under a thousand meters of water
and is impossible to retrieve.
The hope is that if they can establish the cause of flight 781�s crash,
it would explain why the second aircraft went down.
Over the next 4 months,
781�s wreckage is methodically pieced together
at Sir Arnold Hall�s headquarter in Farnborough.
It�s groundbreaking work.
Never before on that scale, an aircraft�s been reassembled by anyone,
and the investigation team had to learn how to do it and develop
the techniques and
tools to reassemble a very-badly-damaged aircraft.
As they examine each piece of debris, they find intriguing clues:
bits of carpet, pills from the first-day cabinet,
a corner of a mirror from the toilet, and scraps of passengers� luggage,
are all found waged in the rear end of the fuselage
under the root of the tail fin.
It suggests an explosion at the front of the cabin
that blasted personal belongings to the rear of the plane.
The question is: how
and where did the explosion start?
As the wreckage begins to provide some clues, so too do the victims.
Four of the bodies retrieved from the second crash
are flown to Britain for post-mortem.
The pathologist finds identical injuries to those of flight 781:
fractured skulls, and ruptured lungs.
Hall has a hunch. Could the entire plane
had bursted like a balloon?
After all, the pressurized cabin designed to keep passengers comfortably, would mean
that the aluminium skin of the Comet is highly stressed.
Any structural failure and it might simply explode as its owner called.
Such a violent decompression
as it�s called has never happened on a passenger plane before,
but Hall and his team believe this could explain that terrible injuries.
To test the theory, they stage a pioneering experiment.
The team built a Perspex model of the fuselage,
1/10th the actual size. The cabin includes 28 miniature seats
with 6 dummies.
The model is housed inside a pressure chamber.
When the pressure in the fuselage is increased
8 � pounds, the equivalent of flying at 12000 meters,
the team deliberately rupture the model.
A high-speed camera captures the results.
The rapidly-escaping air causes a tremendous release of energy.
Seats tear apart and fly through the air.
The dummies catapult vertically
and smash their heads on the cabin roof. It�s a graphic demonstration
of a phenomenon experts like Paul Withey understand only too well.
The pressure cabin exploding
is as same as a 500-pound bomb coming off inside the cabin.
The experiment appears to explain how the victims of both flights sustain
such horrifying head injuries.
Not only that, the sudden change in pressure would cause the air inside the victims
to expand rapidly, rupturing their lungs instantly.
If explosive decompression can explain what happened to both planes,
the team must discover exactly what caused the weakness
in the structure of the fuselage.
BBut a failure in the aluminium skin seems implausible.
The manufacturer�s own tests show the natural life expectancy of the fuselage
is over 10000 flights, many more than the number flown by the two crashed planes.
Nevertheless, Sir Arnold is not a man to leave any stone unturned.
He decides to put the entire airframe to the test.
Sir Arnold Hold
decides that this failure of the pressure cabin could be one of the possible causes,
and because he wanted to make sure that everything was looked at,
this was just one of the test that was performed.
Before testing begins, the team look closely at the Comet design.
They discover that to withstand the stress caused by repeated pressurizations,
the skin of the aircraft must be immensely strong. But it must also be
extremely light.
In order to achieve this, de Havilland developed a lightweight aluminium alloy skin
just over half a millimeter thick.
The Comet skin thickness
was as thin as the designers� dead go, to withstand the cabin pressurization
and it was fixed by how little they thought it could get away with.
Sir Arnold decides a test to assess the strength of the plane�s fuselage.
The experiment is on a completely different scale
to anything they have attempted before.
It requires the construction of a massive water tank,
measuring 34 meters long, by 7 meters wide
and 5 meters deep.
Working non-stop, it takes a team of engineers 6 weeks to complete.
The team of Royal Air Force, you know,
are working really had. They�re working 24 hours a day,
they work in shifts, then sleeping on site. They�re a very dedicated team.
By May 29th, it�s ready. The engines and cabin upholstery of the Comet
are stripped out. The empty plane is gently maneuvered into the water tank,
with the wings protruding on either side. Hydraulic rams move the wings up and down
to simulate flight conditions.
Engineers fill the tank and the plane with water.
When they are both full, they force more water into the plane,
pressurizing it as if it were flying.
After 5 minutes, engineers reduce the pressure.
Each test puts the same amount of strain into the aircraft
as a single flight at 12000 meters. Sir Arnold plans to test the fuselage
to destruction. It could take up to five months.
The experiment runs 24/7.
Using 1950s� technology, it�s a grueling task.
Today we wouldn�t do a water tank test, we�d actually use computer modeling
and computer simulation to understand how the aircraft would behave.
As the test continue, there are other lines of inquiring.
In mid-June, 5 months after the crash of flight 781,
the team assembled 2/3 of the fuselage onto the wooden frame.
Half a wing lies on the floor.
It�s now clear from the tears in the metal, that the aircraft
has indeed decompress violently and blown apart at the seams.
By following the fractures back to where they started, they think the initial failure
was probably at the front of the fuselage, somewhere between the cabin and the cockpit.
It seems as if the tail and rear fuselage
then came away from the main cabin. The rear wing structure followed,
and then the outer wing tips.
The cockpit broke away as the plane plummeted to earth, and finally
and finally fuel from the wings set the debris ablaze.
But the exact cause of the tragedy
is still a mystery.
Then, on June 24th, Sir Arnold Hall gets a call that changes everything:
the team running the water tank test has had a major breakthrough.
Less than a month after testing began, after the equivalent of just 3000 flights,
the Comet fuselage ruptures.
Engineers immediately drain the tank, and Sir Arnold Hall inspects the damage.
There is a massive tear in the aircraft skin, 2 meters long
and 1 meter deep. The tear follows the line of the plane�s windows and doors.
It�s a shocking but vital turning point, they have uncovered
a major weakness in the structure of the Comet.
The entire fleet seems to be fatally flawed.
I think everybody was thunderstruck, de Havilland certainly was thunderstruck,
because they didn�t expect a Comet airframe to fail so soon in its life.
But what caused such a dramatic failure?
There�s one prime suspect: a phenomenon known as metal fatigue.
It�s something Paul Withey knows well.
This is a piece of aluminium sheet, similar to that
was used in Comet skin but much thinner. One cycle of load
isn�t going to fail it at all, but if I repeatly load it like this�
Fatigue is caused when a metal
is repeatedly flexed one way and then the other.
Then you can just see it, about 3 or 4 milimeters across the sheet.
After a while, minute cracks start to form.
Cracks grew further across the sample.
The crack steadily increases in size,
and eventually the part fails.
But there are two problems with this explanation, metal fatigue leaves a tell-tale
microscopic pattern on the surfact of the metal.
Although in the 1950s,
technology for detecting this pattern is in its infancy,
none of the parts reclaim from the sea
seem to show any sign of it. Secondly,
before the Comet went into service, the manufacturers did extensive fatigue tests
to find out how the fuselage would behave under repeated pressurizations.
It passed with flying colours.
Sir Arnold knows he must come up with hard evidence to prove the theory.
He must find a part of flight 781 which shows signs of a fatigue.
The piece of evidence that Sir Arnold needed than all of the others
was a source of fatigue crack growth
that he knew was there in the airframe somewhere.
A single piece of wreckage is all that�s needed to validate the entire investigation.
But this crucial evidence still lies at the bottom of the Mediterranean Sea.
It's 1954,
and investigator Sir Arnold Hall believes that the cause of the two Comet crashes
is a rupture in the plane�s lightweight skin.
After unique pressure test
on the Comet�s cabin, the team examine the 2 meter split
that has ripped along the side of the fuselage.
They make some frightening discoveries: by tracing the tear back,
They find it starts at the forward escape hatch.
This is not surprising.
Stress to the aircraft
should be evenly spread throughout the fuselage. But when a door or window
is cut into the plane,
it weakens the structure and a stress concentrates
around the weakened areas.
To investigate further, they rig another aircraft
with strain gages to measure stress in the airframe.
The results are shocking: during flight,
the stress to the skin around the plane�s windows and doors
reaches 70% of its total strength, 4 times greater
than the rest of the aircraft skin. This is dangerously high,
and twice what the design is intended.
Then the team discover an even more worrying detail.
The supports around the windows are riveted,
not glued as designed. The problem is:
the rivets are punched into the metal, not drilled.
These techniques create tiny manufacturing defects, which were repeated flying,
can turn into fatigue cracks.
The presences of manufacturing cracks in a highly stressed area meant
that you are highlighted something suffer from fatigue failure.
Sir Arnold and his team know they�re getting close, but they have not yet
conclusively solved the mystery. They found no trace of metal fatigue
on any of the wreckage from flight 781.
It was vital that he found a piece of evidence
from the seabed that would tie the crash
to the accident investigation in an unequivocal manner.
Then, on August 12th,
7 months after flight 781 crashed, an Italian trawler snags a large piece of wreckage.
It turns out to be a section of the roof from 718�s fuselage.
The piece includes two small windows built for sending and receiving radio signals.
Sir Arnold Hall and his team inspect the wreckage at Farnborough,
and immediately find what they�re looking for:
a rivet hole in the corner of one of the windows shows a tiny crack.
When they put the piece together with the rest of the wreckage,
they find that all the cracks run back to this point.
They have their missing clue.
The future of the Comet, the world�s first passenger jet airliner, hangs up on the
outcome of the Court of Inquiry�
On Tuesday October 19th, after 6 months of grueling work,
Sir Arnold Hall presents his findings to the Court of Inquiry.
But one detail fascinates Withey.
In 1954, the techniques for analyzing metal fatigue were crude.
The final piece of wreckage was examined with an ordinary microscope, 658 00:44:49,,230 --> 00:44:52,940 and the team relied on experience to make their conclusion.
Today,
London Science Museum safeguards the crucial piece of wreckage.
Paul Withey goes to see the historic item for himself.
No one has ever used modern methods to re-examine the evidence.
Using 21st century know-how,
Withey wants to look again at the wreckage and check that Sir Arnold got it right.
In order to preserve the damaged section,
it has been mounted onto a plate.
Running from the rivet hole is the crack which is believed started the catastrophe.
To examine the damage in more detail,
Withey makes an impression
of the crucial area, using a silicone-based putty.
Then, at Imperial College London,
Withey uses an electron microscope
to examine the sample.
Magnifying the crack about 200 times, Withey shows what Sir Arnold would have seen.
This is the fatigue crack we saw on the
Comet skin, and Sir Arnold Hall and his team could see that using the
techniques of the day.
But zooming in further to 800 times,
Withey can see detail that Sir Arnold never could.
He finds a tiny manufacturing defect,
probably formed when the rivet was punched into the metal.
And it was that manufacturing defect that caused this fatigue crack to grow.
And this image here that shows that Sir Arnold Hall and his team were right,
it vindicates what you�re seeing that it was a fatigue crack,
and then grew to failure.
52 years after the most groundbreaking
and innovative investigation in aviation history,
Paul Withey has conclusive proof that Sir Arnold Hall�s results
are absolutely right.
Now, by rewinding the events leading up to that fateful crash,
and by following the evidence uncovered during the investigation,
we can reveal how flight 781 was downed.
10:31 am, January 10th, 1954. 26 minutes to disaster.
Flight 781 takes off from Rome airport.
The plane is designed with an exceptionally-thin aluminium skin.
Rivets punched into the aircraft during construction,
create microscopic manufacturing defects.
On each flight, the pressurization system put enormous strain on the fuselage,
causing stress to the skin, especially around the windows and doors.
Repeated pressurizations
turn the manufacturing defects into fatigue cracks that get bigger with every flight.
19 minutes to disaster.
Flight 781 climbs to 11000 meters.
As it ascends, the pressure increases
and the aircraft skin becomes more stressed.
At 10:51 am,
the Comet�s pilot, Captain Gibson, sends a radio message.
George How Jig from George Yoke Peter.
5 seconds to disaster.
A fatigue crack reaches 2 centimeters in length
and the aircraft skin rips apart.
At 10:57 am,
the shattered pieces of flight 781 fall from the sky.
35 people are dead.
On the island of Elba, lies a memorial to those who lost their lives over 50 years ago.
The pain of the tragedy will never be forgotten.
But the scientific understanding gains during the investigation is comfort to some.
4 years after the crash,
the Comet did fly again, but it never achieved the commercial success it once promised.
In the interim, American company Boeing develop their own passenger jet
and became the dominant force in the world�s aviation.
The de Havilland aircraft company went into decline,
and were eventually taken over.
Passenger air travel had changed forever.
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