All language subtitles for Mayday.S09E02.Alarming.Silence.1080p.AMZN.WEB-DL.DD+2.0.H.264-playWEB_track3_[eng]

For investigators
trying to solve a plane crash,

the most important tool
can be the black box.

It records every detail
in the cockpit...

Look at this.

Where's Charlie at?

...and tells investigators
about vital conversations.

Damn, it's starting to rain.

Northwest 255,
runway 3 Centre,
clear for takeoff.

But in the crash of Northwest
Airlines Flight 255...

I've never been to an accident
of that scale.

...it wasn't
what investigators heard
on the tape.

- Control...
- TCI was un-set.

It was what they didn't hear...
- Checked.

...that would lead
to an astonishing conclusion.

Mayday, mayday.

Detroit, Michigan.

August the 16th, 1987.

It's 8:00 p.m.,
and the city is sweltering.

Twenty-five kilometres
from downtown...

...Detroit Metropolitan Airport

is one of the busiest airports
in the United States.

More than 1,100 airplanes use
its four runways each day.

Today, one of those
is Northwest Airlines
Flight 255,

bound for Phoenix, Arizona.

Captain John Maus is in command.

A Las Vegas native,
57-year-old Maus
is a veteran pilot.

His first officer
is 35-year-old David Dodds,

of Galena, Illinois.

What don't you tell 'em
we're ready to go?

Both have years of experience
on this type of aircraft.

The MD-80 is also known
as the Super 80,

and is the second generation
of the DC-9.

The MD-80
was quite a bit longer,

it had more powerful engines,
it could carry more people.

For that reason,
it was a better money-maker

for the airlines
than the DC-9 was.

Look at this.

The sky
between Detroit and Phoenix
is filled with storms.

Several are moving quickly
towards the airport.

There's a line here...

For the crew,
it's been a long day.

...about 25 miles wide.

Well, if we get outta here
pretty quickly,
we won't have a delay.

They've already flown
from Minneapolis, Minnesota,

to Saginaw, Michigan,
and then Detroit.

Phoenix is their next stop
on the way to Santa Ana,
California.

If we wait
till after the storms here,

there'll be delays
going over to Waterville.

If they're delayed by weather,

they may not make
their final destination.

Let's get outta here
before it starts raining.

The plane's 149 passengers
are also eager to leave.

Paula Chican and her family
have been visiting relatives.

They're heading home to Arizona.

Her daughter Cecilia
is only four years old.

- Looks like bags are all in.
- Why don't you tell 'em
we're ready to go?

Ramp 255 at Delta 15, uh...

Flight 255
is running half an hour late.

Northwest 255 clear to go.

- Okay, we're clear to push.
- Let's do the checklist.

- Brakes.
- Set.

Windshield heat...

is on.

Boost pumps. We've got six.

Cabin-pressure controller:
Checked.

Auxiliary hydraulic pumps...
pressure:

On and checked.

Damn, it's starting to rain.

To beat the storms,
they need to leave immediately.

...beacons: They're all on.

Before Start checklist
is complete.

Flight 255 begins moving
from the gate to the runway.

Northwest 255...

But because of the weather...

Northwest 255,
now exit at Charlie,
runway 3 Centre.

...the ground controller
gives them a last-minute
runway change.

Okay,
out to Charlie for 3 Centre,
Northwest 255.

Charlie for 3 Centre, right.

Okay.

Ladies and gentlemen, uh,

we're currently number one
for departure.

We should be rolling
in a couple minutes.

Flight attendants, be seated.
Thank you.

Blacker than hell out there.

Where's Charlie at?

By the time they get
to the new runway,

they're 45 minutes
behind schedule.

Northwest 255,
runway 3 Centre,

clear for takeoff.

Within 17 seconds,

65,000 kilograms of passengers
and aircraft hurtle
down runway 3C.

But moments before liftoff,

Maus discovers he can't engage
the autothrottle.

It won't stay on.

TCI is unset.

His computer
isn't in takeoff mode.

They're on now.

Okay.

Clamp, 100 knots.

At 313 kph...

V1, rotate.

...the pilots angle
the plane's nose up
for liftoff...

...then something else
goes wrong.

Just under 50 feet
from the ground,

the aircraft begins rolling
from side to side.

Tower, lifeguard copter, 120.

It rolls left
and strikes a light pole.

Out of control, Flight 255
slams into the ground...

...skids along a highway...

...and disintegrates
when it hits an overpass.

I prayed
that everybody made it,

but I thought
it was just a small plane
'cause it happened so quickly.

I didn't know
it was a bigger plane.

And... it was just awful.

I saw the plane
come through the viaducts;
a big fireball.

When we got dispatched,
it was a rainy Sunday night.

And ten he said
there's an airliner down,
and our mood just changed.

And the one guy looked at me,
Dan, and said,
"Well, I hope it's a small one."

When we pulled up,

we saw the cockpit
and the word "West"
written on the fuselage.

We looked at each other and
he said it looks like a big one.

There's a trail
of scorched bodies and debris
more than a kilometre long.

Just minutes after impact,

paramedic Tim Schroeder
is on the scene,
looking for survivors.

I'd never been to an accident
of that scale.

We were struck
by the... the magnitude
of what we were seeing,

the large scale of it.

It was just...
it was almost overwhelming.

From the little
that's left of Flight 255,

it is unlikely
they'll find anyone alive.

I buddied up with Dan
and we both started entering
the wreckage.

It was probably a minute went by
and Dan actually heard, um,
a noise.

He asked me a couple times,
you know, do I hear anything,
and I said no.

And then finally I heard it.

And there was more
like a faint cry.

When I turned my head
to the right,

I saw an arm...
underneath the seat.

One, two, three, lift!

She was covered in some blood
and some soot.

Somehow,
four-year-old Cecilia Chican
has survived the crash.

But she's badly injured.

Tim Schroeder races her
to hospital.

We have a four-year-old girl
found alive in the wreckage.
She has a very weak pulse.

If Cecilia survived,

perhaps others have, as well.

Rescuers spend hours
looking through the wreckage
for more survivors.

But their efforts
will be in vain.

We actually covered
anything that...

was a body or a body part
with a yellow blanket.

It was just nothing but, like,
a sea of yellow blankets
basically.

Northwest Airlines said
154 passengers and crew aboard
the plane died in the crash.

Both Captain Maus
and First Officer Dodds
are killed in the crash.

Two other people died
when their cars were hit
by the plane.

This is the second-deadliest
airplane disaster
in U.S. history.

Recovering in hospital
with serious head wounds

is Flight 255's lone survivor,

four-year-old Cecilia Chican.

Despite her injuries,
doctors say she will live.

Maybe, uh,
God was on her side that night.

Within hours of the crash,

Investigator Jack Drake
and his team

from the National
Transportation Safety Board

begin looking for clues.

Drake is a former Navy pilot
who's been involved in hundreds
of crash investigations.

You know
when you're at a crash site,

because you get this combination
of burned plastic and kerosene,

and sometimes combined
with fire-retardant foam

that has
its own distinctive odour.

You know you've arrived
when you smell it.

Drake and his team
treat the crash site
like a crime scene.

Our team consisted
of 12 or 13 specialists,

some of whom go to the site
and some of whom
do their work elsewhere.

They set out to examine
every piece of wreckage

to discover what went wrong.

They have responsibilities
for looking at different parts

of the wreckage debris...

...and do qualitative analysis
of those parts.

We always look
for the recorders first.

They're frequently referred
to as black boxes,

although they're usually orange.

The information
is usually well protected,

because they're encased
in a steel box

that is both heat-resistant
and crash-resistant.

Since the 1960s,

commercial jetliners have been
required to carry flight-data
and voice recorders.

The CVR was first introduced
in Australia,

following the 1960 crash
of a Fokker F27.

The devices must be able
to withstand an impact
of 3,400 Gs

and temperatures as high
as 1,100 degrees Celsius.

The cockpit voice recorder
is intact.

But the flight-data recorder
suffered some damage
in the crash.

They may hold the only clues
that can help solve
this accident.

Both recorders are sent
to the NTSB lab
in Washington, D.C.

John Clark is Drake's
flight-performance engineer.

His first task is to make
a map of the debris
left behind by Flight 255.

When I first started
seeing the wreckage,

it, uh... your mind immediately
starts turning to, uh...

sorting out where it hit,
how it hit.

Not where the wreckage ended up,

but those first few inches
where the airplane
was coming down.

Clark looks for ground scars
and other impact marks,

and interviews witnesses
to piece together
where the plane fell and how.

And, uh,
that kind of gives you
a sense of those last moments,

what the airplane was doing
when it hit the ground.

Clark begins to understand
the final moments of Flight 255.

According to witnesses,
as it lifted off,

it couldn't climb and flew
in a nose-high position.

V1. Rotate.

That could indicate
that the plane didn't have

enough power
to get off the ground,

that it didn't have
enough speed,

or that high winds
prevented it from lifting off.

Witnesses provide investigators
with a critical clue.

You saw fire
coming from the engine?

Several, including
an air-traffic controller,

saw flames coming
from the plane's engine
before the crash.

Damn!
No!

The engines become
the first focus
of this investigation.

They looked for evidence
of an internal failure.

The plane suffered
an engine failure...

Investigators soon learn
that less than a month earlier,

one of the plane's engines
was damaged when it was hit
by a foreign object.

It was repaired
and being monitored by mechanics
to see how it performed.

The team studies the remains
of the engine for clues
that it had either caught fire

or shut down on takeoff.

Despite what the witnesses saw,

they find no evidence of fire
or of a massive breakdown.

The information suggested
that the engine operation
had been normal.

Clamp, 100 knots.

The flames were the result
of the fuel tank rupturing

after the plane hit
a light pole.

The fire didn't cause the crash.

If Drake and his team
are to solve this mystery,

they need to be certain
about what happened

in the last few seconds
before Flight 255 crashed.

Well, I think probably
the best physical evidence

is what was
on the flight-data recorder.

The flight-data recorder
doesn't tell you about weather,

it tells you
about aircraft parameters,

aircraft performance,
essentially, second by second,

even at quarter-second intervals
in some parameters.

But NTSB technicians
can't recover

all the information
from the recorder.

They send it to the manufacturer
to see if can recover
the lost data.

While he waits for news
about the flight-data recorder,

Jack Drake looks more closely
at the weather
on the night of the crash.

There was some convective
or thunder-shower-type activity
that had moved through the area,

and its impact on the accident
required a lot of analysis.

Drake wonders how the storm
affected Flight 255.

He listens to the cockpit
voice recorder for clues.

He discovers
the menacing weather
was a concern to the crew.

Let's get outta here
before it starts raining.

Jesus, look at this.

Drake sees
that there were several storms
along the flight path,

and they were getting closer
to Detroit.

There's a line here...

...and a line between these two.

Uh-huh.

And another one here
about 25 miles wide.

Thunderstorms can
create a very dangerous threat
to pilots.

Since there was severe weather
in the area,

we always worry
about microbursts.

Microbursts occur
when columns of air
shoot down to earth.

As a plane passes through,

winds batter it
from all directions,

making it difficult to control.

In a microburst condition,

you can get
very shifting winds,
and also vertical winds,

that will try to push
the airplane into the ground.

So you can get
a loss of airspeed,
a very rapid rise in airspeed,

and then also actually push
the airplane toward the ground.

And it requires
very aggressive flying
on the part of the flight crew.

This unusual weather condition
had killed before.

In 1985, a microburst
brought down a Delta Airlines
flight in Dallas,

killing 137 people.

At the time
of the Detroit accident,

there was no device at airports
to accurately detect
microbursts.

Instead, pilots relied
on reports from other crews.

Jack Drake discovers
that 27 minutes before liftoff,

Captain Maus
and First Officer Dodds
received such a warning.

Ground, this is 722.

You just had
a microburst out here.
The dust exploded down there.

Investigators suspect that a microburst

may have slammed Flight 255
to the ground
as it tried to lift off.

It was right after departure
when the accident occurred.

If they had struck
a very strong microburst,

that would be a candidate
for one of the possible causes.

Satellite images
taken at the time of the crash,

and weather data
from the airport's sensors,

show that there were storms
near the airport at the time
of the accident,

but there's no evidence
of a microburst.

Wind and rain, but nothing
that could be a microburst.

Around the time of the crash,

the airport's sensors did record
a dangerous gust of wind
on the runway,

powerful enough to set off
alarms in the tower.

Upon further investigation,

Drake discovers that Flight 255
was still at the gate
at the time of that alarm.

So the winds couldn't have
brought the plane down.

Sign beacons.

But they did have a huge effect
on Captain Maus's flight plan.

The crew's pre-flight
dispatch package stated

they would take off
from runway 21 Left.

But with the sudden change
on wind direction,

Ground Control sends Flight 255
to runway 3C,

the shortest
of three available runways.

Northwest 255,
now exit at Charlie,
runway 3 Centre.

Yeah...

Okay to Charlie for 3 Centre.

Northwest 255.

Charlie for 3 Centre, right.

Okay.

Controllers try to have planes
take off into the wind.

The additional wind flowing
over a plane's wings
gives it more lift

and helps it get off the ground.

Taking off into the wind
is safer,

but taking off
on the shorter runway

now means First Officer Dodds
must recalculate
the plane's takeoff weight.

If there's a runway change,

you have to determine
if the weight of the aircraft
will permit it to accelerate

and climb out safely;
and this varies,

depending on the length
of the runway, temperature,
altitude of the airport.

Perhaps First Officer Dodds made
a mistake in his calculation.

4044?
How can we be that light
for a full airplane?

If he did,

it could explain why the MD-80
wasn't able to make it
off the ground.

Runway 3C
simply wasn't long enough.

Using calculations based
on average weight of luggage
and passengers on board,

Drake's team confirmed
Dodds's estimate.

The plane weighed
144,047 pounds,

well below the allowable limit
for runway 3C.

It should've been able
to get off the ground.

Drake's investigation
has hit another dead end.

He and his team are running out
of possibilities.

Until technicians can decode
the damaged
flight-data recorder,

the team must rely
on the physical evidence

that's been found
at the crash site.

But when investigators study
the cockpit's centre console,

they're forced to consider
an almost unimaginable cause.

Is this the way it was found?

To get the plane
off the ground,

the flaps on the wings
should've been extended
to the 11-degree position.

But the way the flap handle
is damaged suggests

the plane's flaps were retracted
when it crashed.

The pin... had a left mark.

This happens
because the aircraft
comes to a very sudden stop,

and the handle jangles around
and...

and it's a metal-to-metal
contact

that's exaggerated
by the impact.

It won't stay on.

That indicator
was that the flaps were zero,
or fully retracted,

and the slats were retracted,
as well.

Flaps and slats are extensions

that slide out of the back
and front of the wing.

They make the wing bigger,

which increases the amount
of lift they can provide.

They must be extended
for takeoff.

If the slats are retracted,
for the most part,

with today's modern jets,
the airplane
is not capable of flight.

If the crew tried to take off
with the flaps retracted,

it would be
an astonishing blunder.

V1. Rotate.

But a pilot
who was lined up directly behind
Flight 255 on the runway

is certain the plane's flaps
were extended.

And you're sure
the flaps were extended?

Pilots in other aircraft
that were close to the point
of where the takeoff had begun

were telling us that
they thought the flaps and slats

were deployed
to a normal position.

Investigators can't be sure whether the flaps
were extended or not.

The clues they need lie
somewhere in the sea of debris
recovered from the crash site.

Eventually, investigators find
the evidence they need

inside a section
of the plane's left wing.

Each component
of the slat system
has its own drive system,

and one of those was interrupted

by the light pole
that passed through the wing.

Eighteen feet of the left wing
was severed.

The cable controlling the slats
was sliced in two

when the wing hit
the light pole.

Based on where the cable
was cut,

investigators can tell
whether the slats and flaps
were extended or retracted.

It severed two cables,

and if you lined up
those two severed ends,

it corresponded
with the slats being
in the full retracted position.

It looks increasingly likely

that the crew never extended
their flaps.

Only the damaged flight-data
recorder can verify this.

Fortunately,
technicians have finally been
able to rescue all its data...

...a digital history
of Flight 255's performance
until the moment of impact.

I knew that...

if we had a good recorder,
we were gonna get data back.

The flight-data recorders,
in combination,

give you that time history
that goes together
with the physical evidence,

or physical damage.

As expected,

the FDR confirms
what the evidence
has been showing investigators.

The flight-data recorders
told us that the, uh,

the flaps and slats
had not been extended.

It's a major breakthrough.

Drake now knows
what brought down Flight 255.

But the flight-data recorder
doesn't answer
a more troubling question.

So... why weren't
the flaps deployed?

For some reason,

a seasoned crew forgot one
of the most basic steps involved

in getting an airplane
off the ground.

Two months after the crash...

...Northwest Airlines
Flight 255's sole survivor,

Cecilia Chican,
is released from hospital.

We can't be sure
why the little girl survived.

She's a very little girl
buckled into a big seat.

And she was more protected
than adults that might've been
sitting around her.

So she was very lucky.

Jack Drake needs to know
what contributed to the death

of her family
and all the other victims.

He finds an important clue
on the cockpit voice recorder.

It shows that the last-minute
runway change

caused confusion in the cockpit.

Once the aircraft
began to taxi...

- Blacker than hell out there.
- Northwest 255,

now exit at Charlie,
runway 3 Centre.

Other activities
were introduced

that had the potential
to cause distractions.

Did he say 3 Centre?

3 Centre, yeah.
That's why I was thinking
we had to go that way.

I was thinking 21.

Well, they made a wrong turn,
which might've been confusing,

because they had to go
a different route.

Where's Charlie at?

Right at the end of this ramp.

- I think Charlie was--
- No, it is Charlie.

You sure?

I think so.

The crew got lost
on the way to runway 3C.

Ground, Northwest 255.

I guess we went by Charlie.
We're going to 3 Centre, right.

Northwest 255, affirmative,
make a left turn
at Foxtrot.

They finally got to the runway
45 minutes late.

Ladies and gentlemen,
we're currently number one
for departure.

Should be rolling
in a couple of minutes.

Flight attendants, be seated.
Thank you.

Brakes.
But Jack Drake finds
something missing on the CVR.

It seems the crew overlooked
a very important step.

We're okay for the...
centre runway, aren't we?

Before they got lost,

the crew of Flight 255 performed
a number of checklists.

But possibly due
to the confusion
of the runway change,

they seemed to have completely
neglected the taxi checklist.

They apparently
didn't consider the checklist,

and key in the checklist
is the configuration
of the aircraft for departure.

And the flight-data recorder
showed that was never done.

There are hundreds
of small steps
for a crew to take

to get a passenger jet
off the ground.

Most of them are covered
by checklists.

The checklist is a means
by which you ensure

that important items
are positioned or done properly.

- Transponder.
- Instead of doing it by memory,

and having the possibility
of a lapse of memory...

...flight crews use
a very rigorous
and regimented procedure

of following the checklist...

- Cabin-pressure control.
- ...to verify that each switch,

each dial, each lever
is in the proper position

before taking the runway
for departure.

The first item
on the taxi checklist is flaps.

One of the things
that would've been included
in their checklist

was to configure the slats
and flaps for low-speed flight.

But because they didn't run
the checklist,

the crew never set their flaps
to the takeoff position.

- I think Charlie was--
- No, it is Charlie.

You sure?

I think so.

They hadn't done
this checklist at the time
they normally would.

And as the activities piled up,

um, that were potential
distractions,

they were further
and further away from the point

at which they would normally
perform that function.

Their mindset was probably
that they had completed it.

The pilots got
an indication that their plane
wasn't properly configured.

During takeoff,
they couldn't activate
the autothrottle,

because their computer
wasn't in takeoff mode.

Another step covered
by the taxi checklist.

It won't stay on.

TCI is unset.

This should've alerted them

that they didn't perform
the checklist...

If it had occurred to them
at that point

that we might've missed
something else on the checklist,

that could've led
to a rejected takeoff.

They're on now.

Hundred knots.

Okay.

Apparently,
that didn't happen,

and so the takeoff
was continued.

...with disastrous results.

An alarm should've sounded
when the pilots tried to take
off with their flaps retracted.

But for some reason,
investigators can't hear it
on the cockpit voice recorder.

When it activates,
it alerts the crew
that the aircraft

is not in a configuration
that's safe for takeoff.

Maybe it went off
but we just can't hear it.

The investigation team
is determined to find out

why the takeoff warning
didn't sound.

Technicians analyze
the cockpit voice recorder
for more clues.

And they find something unusual.

They picked up, uh,
some annunciations on the CVR
that were not correct.

Stall.

Stall.

This warning
is alerting the crew that
the plane is about to stall.

But it should be coming
from two speakers
in the cockpit.

Stall.

Technicians notice
it's only coming from one.

Stall.

Stall.

As the airplane lifted off,
there was a stall warning,

and it has
a typical characteristic

of a sound like "stall-all,"

because there are
two annunciations,

and the purpose of that
is to provide redundancy.

But that redundancy
wasn't there.
We had a single "stall."

I went to an MD-80 sitting
on the ramp at Detroit.

And a captain took us
through the process
of checking out

to demonstrate
those different sounds.

Let's start
with the config warning.

The takeoff
configuration warning
is what would've alerted them

about the flaps and slats.

Flaps.

Slats. Flaps.

Can we get the stall warning
to sound?

Stall all.
Stall all. Stall all.

He activated
the stall-warning system
by a test switch,

and it said: "Stall-all."

The voice on the left channel
is slightly different

from the voice on the right,
as it should be.

But that's not what Clark heard
on Flight 255's voice recorder.

Can you make it sound
like this?

Stall.

Stall.

To get a singular stall,

he had to pull power
to one side or the other.

One way he demonstrated that
is he pulled
the P40 circuit breaker.

A circuit breaker
is the electrical switch

that protects the circuit
from damage caused by overload.

The P40 circuit breaker
is an important one
in this investigation.

It handled both
the failed takeoff-warning
and the stall-warning systems.

What struck me was he said,
"I hear people doing it.

I, of course,
don't do it myself,
but let me show you how."

And he reached around
behind him,

around behind the seat
and down low,

and pulled the P40
circuit breaker without looking.

And then, when he ran
the stall-warning system,
we got the singular "stall."

Stall.

Stall.

It's a major clue.

Clark could only reproduce
the strange-sounding
stall warning

by pulling
the same circuit breaker
that's connected

to the takeoff warning.

This tells investigators
that the breaker was tripped

when Flight 255 tried
to take off.

Then John Clark notices
something else
about the P40 circuit breaker.

You could see smudge marks
around the decals

on each side
of the circuit breaker.

It looked like fingermarks
where oil had built up,

and dirt and grime,
over the years.

So it told me
that circuit breaker

was being used routinely
by a lot of pilots.

Can you tell me
why that is so worn?

It turned out
that the takeoff-configuration
warning

could be a nuisance to pilots.

If you're doing
a single-engine taxi,

you have to push the throttle
up further to get a power
to taxi,

and you would set off
the takeoff-warning system.

So they would pull
the circuit breaker
to silence it.

It's irritating.
It's a warning.

It... it's meant to alert you.

And if it's going off routinely
all the time,

it gets on their nerves
and, uh...

so... apparently pilots
were routinely silencing
those takeoff warnings.

Investigators suspect
that the crew of Flight 255

tripped the breaker to avoid
the irritating takeoff warning.

And then, with the added delay
from the runway change
and the impending storm...

...they proceeded to take off
without doing
the taxi checklist.

That might explain
why the alarm didn't sound

when they tried to take off
with their flaps retracted.

We don't know if the pilot
did pull that circuit breaker
on that particular flight.

There was certainly one error
and the potential for two.

I think the extensive use
of the circuit breaker,

because of the smudge marks
around the circuit breaker
and the pilots' statements,

I think it's highly likely
that he did.

It appears
the downing of Flight 255
was caused by pilot error.

Now investigators
can accurately piece together

what happened that night
in Detroit.

But it would take another
shocking accident

for the airline industry
to learn its lesson.

Jack Drake's team
has discovered what caused
the crash of Flight 255...

...but cannot prevent it
from happening again.

One year later, in Dallas,

Delta Flight 1141
tried to take off
without their flaps extended.

The investigators
who had been working on
the Northwest crash are stunned.

I was very frustrated
to learn that...

that another airline
had done the same thing

in a different aircraft type
about a year later.

The Delta crash would uncover
potentially deadly flaws...

Okay, Before Start checklist,
battery. Uh...

...in the checklists
commercial pilots are trained
to follow.

The Delta and Northwest crashes
killed 170 people...

...and had
eerily similar causes.

In both disasters, the workload
in the cockpit increased...

Jesus... look at this.

Northwest 255,

now exit at Charlie, runway 3...

If we get outta here
pretty quickly,
we won't have a delay.

And in both,

the pilots failed to perform
vital elements
of their checklists.

It is very unusual for a crew
to not perform a checklist.

They have done it hundreds
upon hundreds of times.

Brakes.

Windshield heat... is on.

Cabin-pressure controller...
is checked.

The normal procedures, uh,
were a little bit
out of the norm.

And as a result,
it got overlooked.

To prevent this
from happening again,

aviation officials turned
to a government agency

that knows the importance
of clear procedures:

- Four, three, two...
- Discovery, you're go.

...one.

...NASA.

- So they're ready to go.
- Alright.

Jack Drake and his team wanted
the U.S. space agency

to help create checklists
that decrease the odds
of items being skipped.

Asaf Degani
was a research scientist
working with NASA.

After the accident,

he took on the project
of improving a flight crew's
pre-takeoff procedure.

We looked for any research
that was done on checklists
or procedures in general.

And, in fact,
we couldn't find anything.

So Degani
had to start from scratch.

But there are dozens
of different checklists
to examine.

Most of the ones on Flight 255
were printed on a single card.

They listed the tasks
the crew had to carry out,

but didn't give them
a way to keep track
of what and what wasn't done.

At the time
of the Northwest crash,

there were several types
of mechanical checklists in use.

The U.S. Air Force used
a scrolling checklist.

Once a checklist item
is completed,

the pilot scrolls
to the next one.

American Airlines used a system
that allowed pilots

to cover up completed items
with a plastic slide,

so only the non-completed items
would be displayed.

Asaf Degani set out
to see firsthand how pilots
were using checklists.

He wanted to make it less likely
for them to make mistakes.

He sat in cockpits and observed
42 different crews in action.

Degani concluded
that many checklists
were badly designed.

There's a certain flow
by which you go about
checking things.

And the idea is to prevent
the case where you're doing
one thing here, one thing there.

A checklist should have
a certain flow,

which is a logical flow and not
one which is kind of random.

And they're ready
and they're going through...

Degani also found
a much more serious problem
with checklists.

If pilots are interrupted,
they sometimes forget
where they left off.

Transponder...

checked and on.

And there's many cases
where people would do, A, B,
C, D, E,

an Air Traffic call would come,
they'd have to respond to it,
and that's an interrupt.

Northwest 255,
now exit at Charlie,
runway 3 Centre.

Yeah...

They would go back
to the checklist,

and skip a certain item
and continue on the list,

assuming that the whole list
was done.

People were very concerned
about that.

To ensure no steps are missed,

airlines train their pilots
to return to the top
of a checklist

following the interruption
and start over.

Again, Asaf Degani
sees a problem.

And we found
that if checklists are very,
very long and meticulous, um,

that's overburdening the crew
and they sometime would not want

to start again
from the beginning.

To address the problem,

Degani suggests changes
across the airline industry.

One of our recommendations
from the study

is to try to take
long checklists
and chunk them to small pieces,

so that if an interruption
happens,

then doing another
four or five items,

it's not a big effort,
as opposed to doing 20.

Degani even made recommendations

about the typeface
that airlines use

so they can be more easily read
by pilots.

Perhaps the biggest advance
to checklists is the move
from paper to computers.

Since, at the time, um,
computer technology was coming
into the cockpit,

it made a lot of sense to think
about electronic checklists.

Today, Degani and his team
are studying smart checklists

that keep track
of checked items.

They provide pilots
with a visual indication
of where they are on the list,

and in some cases,
verify that the task has been
correctly carried out.

An electronic checklist
shows you which item...

was completed
and which item was not.

Computerized checklists
are now slowly making their way

into the cockpits
of commercial airplanes.

They make it far less likely
that an accident
like Northwest 255

could happen again.

The FAA also ordered
a modification
to the alarm system

of all commercial jetliners
to prevent nuisance alarms.

The takeoff warning
was redesigned

so it could not sound
unless the plane
was actually taking off.

Jack Drake went on
to investigate hundreds
of accidents

over a 26-year career
with the NTSB.

The crash of Flight 255
taught him a valuable lesson.

This one
is a worldwide example of...

the importance
of following checklists

and configuration
being completed correctly
on every takeoff.

And so it became something
that was a part
of the training curriculum

in virtually every airline
around the world.

The case of Northwest 255
is no different.

It was a series of events:

runway change, task saturation,
an overlooked checklist,

a failed takeoff warning system.

Put all of those together,
those links in a chain,

and you end up
with the accident.

If you were to break
any one of those links,

the accident
wouldn't have happened.

Flight 255
will also be remembered
for its lone survivor,

Cecilia Chican.

She's never spoken publicly
about the death of her family.

But she's stayed in touch
with the people
who rescued her that day.

She's full of life,
and the conversations we have,

it's more about, you know,
her sports and her husband
and her vacations.

She just said maybe one day,

she'll come out and tell
the world what Cecilia is doing.

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