Original subtitles

We're going over!

NARRATOR: A Boeing 727 spirals out of control over Michigan.

You're watching the world spinning outside the window.

This would be sheer stark terror.

The air speed is 320, 350.

Come on! Come on!

No, no, no.

NARRATOR: Investigators tracked down pieces of debris--

Slot number seven.

Broken in two.

NARRATOR: And interview fellow pilots.

Off the record?

Off the record.

NARRATOR: They even risked their own lives--

OK, test number 9.

NARRATOR: To find out what caused TWA Flight

841's uncontrollable plunge.

You feel that?

Mayday, mayday.

It was insane.

My hands are still shaking.

NARRATOR: 44-year-old Captain Harvey Hoot

Gibson has just returned from the most

harrowing flight of his life.

Tell me what happened.

NARRATOR: A representative from the Federal Aviation

Administration takes his statement.

We were cruising over Michigan.

That sure is a strong headwind.

NARRATOR: Captain Gibson is a trained stunt

pilot who has a clean 16-year record

with Transworld Airlines.

Do a ground speed check, will ya?

Sure thing, Hoot.

NARRATOR: First officer Scott Kennedy has been

flying with TWA for 13 years.

Yeah, we're good to go up any time you want, Hoot.

NARRATOR: Flight engineer Gary Banks

is an Air Force veteran who's been

with TWA for the last 10 years.

BARRY STRAUCH: The crew of Flight 841

had just the right kind of experience

you would want for a 727 crew.

Center TWA 841, we'd like to try flight level 390.

DISPATCH: Roger, TWA 841.

Climb and maintain flight level 390.

KEITH SHIBAN: They were bucking 100 knots of wind

on their nose, so he was looking for better winds up higher.

The higher you go, you essentially go faster

through the thinner air, and that will hopefully

get to a better ground speed.

I can take that off your hands.

NARRATOR: 27-year-old Mark Moscicki is

today's lead flight attendant.

He and three other attendants look after the 82 passengers

on board.

MARK MOSCICKI: It was an evening flight.

It was leaving JFK.

It was the first time I had flown with this cockpit crew.

Everything was absolutely smooth.

NARRATOR: They're flying the narrow body

Boeing 727 aircraft.

KEITH SHIBAN: The 727 was massively overbuilt.

It was very sturdy airplane.

It was like driving a sports car or fighter plane.

It was very light on the controls.

It had that feeling that you could just

put it wherever you wanted it.

NARRATOR: After a 45-minute delay in New York,

the flight to Minneapolis will take about 3 and 1/2 hours.

BOB MACINTOSH: They program 39,000 feet

and got right up there.

And sure enough, they were gaining speed.

They were probably going to cut 10 to 15 minutes

off their en route time.

I'll do another ground speed check.

Power settings are adjusted.

Everything looks good.

NARRATOR: After meal service, Moscicki takes

a moment to eat his own meal.

MARK MOSCICKI: I sat on my jump seat.

Very shortly, however, there was a very abrupt

buffeting of the aircraft.

It wasn't turbulence.

What the heck?

BOB MACINTOSH: The captain noticed something was strange.

The wing had started to drop, and the autopilot

was compensating for that.

I got control.

BARRY STRAUCH: Disengaging the autopilot was the right thing

to do at that time.

That's the first thing you think of.

There's something wrong with the autopilot.

What's going on?

NARRATOR: Without any warning, the plane banks

hard to the right.

Airspeed 240.

Come on.

Level up.

But if the plane still doesn't respond,

then you're thinking there's something

wrong with the airplane.

The plane just kept rolling right,

and it started rattling really hard, too.

I would be trying the rudder, and

if that's not doing the jobs, I start

trying to fly with the engines.

But 727, the engines are all clustered together in the back.

That probably wouldn't help you much.

So this would be pure stark terror.

Shutting the throttles.

NARRATOR: The captain tries to slow

the plane to regain control, but the aircraft isn't responding.

Get them up.

Get them up!

NARRATOR: Desperate to slow the plane,

Gibson deploys the speed brakes.

Speed brakes are flight control surfaces that increase

drag and decrease speed.

You're going to put those out to try and slow yourself

down because really bad things are going to start happening

soon if you keep accelerating.

Come on! Come on!

NARRATOR: But deploying the speed brakes proves useless.

MARK MOSCICKI: I got up from my jump seat

to see if perhaps the engine was on fire, and I never made it.

We're going over!

NARRATOR: High above Saginaw, Michigan,

the Boeing 727 drops into an uncontrolled dive

and spins upside down.

Something was extremely wrong.

There seem to be no control of the airplane.

People were just absolutely terrified.

I certainly didn't think that we had wings left on the airplane.

TWA 841, this is center.

TWA 841, center?

Jesus.

Something is seriously wrong.

KEITH SHIBAN: You would have your hands full of airplane.

You're watching the world spinning outside the window.

You're being pressed by g-forces.

It also must have been insanely noisy.

It would have been very difficult to try

and troubleshoot the problem.

TWA 841, do you read me?

NARRATOR: The controllers watch helplessly as TWA

841 plummets toward the ground.

Once the nose comes down on an airliner,

they want to pick up speed in a hurry

if you pointed at the ground.

MARK MOSCICKI: I kept clenching my jaws

and biting my teeth to keep blood in my head.

The g-forces were so extreme I felt I was going to pass out.

KEITH SHIBAN: The blood is literally

being drained out of your head, and you

will first lose your vision.

That's called graying out, and then the next thing

is you black out, which is where you lose consciousness

because your heart just can't pump

the blood up to your brain against all

that force of gravity.

Air speed is 320, 350.

I can't. I can't.

NARRATOR: TWA 841 is spiraling toward the earth at a rate

of 540 feet per second.

BARRY STRAUCH: To feel 6 Gs, the only people

that would experience that would be military pilots.

You're going to feel an incredible weight on you

in every part of you, and whatever position

your body is in, your head or your arms,

they're going to stay that way.

So you're not going to be able to move.

I could see ground lights, and I knew that we were approaching

the ground very quickly.

At that point, you go from abject terror

into almost acceptance.

Oh, no, no.

Come on, baby.

Pull up.

We were falling so fast.

NARRATOR: Captain Hoot Gibson recounts

his recent nightmare piloting TWA Flight 841 over Michigan.

Air speed is 390.

NARRATOR: But Gibson isn't giving up.

Come on, baby. Pull up.

NARRATOR: He has an idea.

Put the gear down.

KEITH SHIBAN: If nothing else will slow you down,

the gear will slow you down, and hopefully

the plane holds together.

That's it.

That's it, baby.

What saved them was putting the gear down because otherwise

they would have been a big smoking

crater in a matter of seconds.

We're pitching up 30 degrees.

Now suddenly we were climbing.

It was like coming out of the bottom of a roller coaster.

KEITH SHIBAN: You would feel like you are being crushed.

The average person would feel like they weighed 900 pounds.

Scott, give me altitudes.

Gary, pitch and airspeed.

5,200 feet.

Jesus, which way is up?

Moon.

KEITH SHIBAN: It's pitch black, and you've just been spiraling

down towards the Earth.

And you're probably disoriented.

He sees the moon, and that's up.

Well, you can sort the rest out later

but get away from the ground.

NARRATOR: TWA 841 has come within seconds of impact

and now climbs back toward the night sky.

Airspeed is 160.

NARRATOR: Though the pilots are flying again,

they are not out of danger.

The steep climb is physically demanding,

and the crew struggles to maintain focus.

10,500, 11,000.

That's it.

That's it, Hoot.

Leveling 1-1-0.

This is your captain speaking.

As you've noticed, we've had a bit of a problem,

but everything seems to be under control.

We lost system A hydraulics.

Fluids are down.

Pressure is down.

NARRATOR: As the crew recovers from the terrifying incident,

they assess damage to the aircraft.

We got a flag for the lower yard damper.

NARRATOR: A deafening rattle makes a tense situation worse.

OK, I'm going to fly the airplane.

You guys start running the emergencies.

BARRY STRAUCH: He was a good captain.

He had them diagnose the problem while he

flew the airplane knowing that you can't do both effectively.

Turn pump emergency switches to de-pressurize

and check quantity.

The fluid is 0.

It's all gone.

NARRATOR: With a damaged hydraulic system,

the aircraft is severely impaired.

OK, we gotta land.

Detroit is our best option.

OK.

We're 60 miles out.

BOB MACINTOSH: When they decided to divert,

they selected Detroit with reasonable weather,

long runways.

It's a developed airport with crash, fire, rescue.

Center, 841.

Go ahead, TWA 841.

OK, listen, we had a problem.

We lost about 20,000 feet.

We need vectors to Detroit.

45 miles from Detroit now.

If you'd like to come left heading

1-6-0 vectors to Detroit.

OK, turn left 160, TWA 841.

Remove your glasses, earrings, and anything

else that might be sharp.

Place anything soft in your lap to cushion the impact.

NARRATOR: 30 miles from the airport, flight attendants

prepare the cabin for an emergency landing.

Passengers were amazingly quiet.

I mean, they looked at us for complete direction.

15 miles from Detroit now.

Nice and easy.

Give me flaps 15.

NARRATOR: Unaware of the extent of the damage, Gibson tests

the aircraft's controllability.

Flaps 15.

Whoa, whoa, whoa.

Detract the flaps.

NARRATOR: Extending the flaps causes the plane

to roll sharply to the left.

You are going to land without flaps at this point, which

means you're going to go very fast, much faster than you

would ever land this airplane.

Go in fast. There's no other way.

This is going to be our only approach.

NARRATOR: With ruptured hydraulics

and a compromised plane, the pilots of TWA 841

have only one shot at landing at Detroit Airport.

The landing checklist complete.

Coming through 200 feet.

I was pretty convinced that we'd

probably be scraping down the runway,

lots of sparks and flames.

50, 40, 30--

Brace.

KEITH SHIBAN: 220 knots in this case.

Just an insane rate of speed for a landing.

Reverse thrust.

Come on. Come on, stop.

Let's get these passengers off the plane.

KEITH SHIBAN: He's just put this badly damaged

airplane down at about 90 knots faster

than a normal landing speed.

This guy was good.

He was really good.

Hoot, it's unbelievable.

What the heck went so wrong with that plane?

Haven't the faintest idea.

NARRATOR: Investigators from the National Transportation Safety

Board arrive in Detroit to determine what

went wrong with TWA Flight 841.

They look in good shape.

Let's get the data on these.

NARRATOR: The flight data recorder and cockpit voice

recorder are removed from the aircraft and sent for analysis.

Let's check that out.

Slat number seven's missing.

NARRATOR: Slats and flaps are control

surfaces on the leading and trailing edges of the wings.

They are always extended in tandem.

Both devices increase lift at low speeds

during takeoff and landing.

That's pretty banged up.

NARRATOR: Investigators wonder why the slat came off.

The hydraulics lines are ruptured, too.

Logical out for a slat tearing off.

Looks like an actuator for the slat is damaged.

NARRATOR: The actuator is part of the mechanism that pushes

a piston to unlock the slat, allowing

it to either deploy or retract.

Let's get the actuator off the wing

so we can get a better look at it.

One of the interesting remnants of this inspection

was the number seven slat actuator.

Look at how it's broken.

There are no scrape marks inside either.

NARRATOR: Investigators uncover an important clue.

Slat came off in an extended position.

BOB MACINTOSH: Number seven slat actuator had broken,

the piston inside it was gone, and they could recognize

from looking at the opening of the fracture

that the piston had been in the deployed position.

NARRATOR: A slat should never deploy at cruising speed.

Maybe the slat extended by accident.

The only way to know for sure is

to test the hydraulic system.

BARRY STRAUCH: For the slat to have been deployed uncommanded

required a failure of the hydraulic system

and a failure of the locking mechanism.

I'll start with flaps 2.

Flaps 15.

Flaps 15.

Looks good.

Next, flaps 20.

Flaps 20.

NARRATOR: Investigators run through every flap

setting possible.

All right, let's wrap it up.

Everything's working fine.

BARRY STRAUCH: The functional test

demonstrated that the hydraulic system worked.

It did not cause an uncommanded slat deployment.

Here's what we got from Boeing.

NARRATOR: Did the locking mechanism on the 727's wing

somehow fail, releasing the slat?

For a slat to unlock accidentally,

the pen inside the actuator must be subjected

to more than 70 Gs of force.

70 G's?

There's no way the locking mechanism experienced

that level of stress.

BOB MACINTOSH: A 70 G pull through by an aircraft

just doesn't happen.

The investigators were faced with a serious challenge

of where to go next.

Take a look.

NARRATOR: Investigators get a break when

debris from flight 841 is recovered seven miles

north of Saginaw, Michigan.

Slat number 7.

Broken in two.

Look at this.

Here's the number 7 slat's T bolt.

NARRATOR: T bolts are part of the slat track assemblies.

The number seven slat T-bolt was attached

to the inboard side of the slat, which deploys

and retracts inside the wing.

Let's send this to the lab.

NARRATOR: They hope metallurgical analysis

will offer some clues, but an important question remains.

Why did the slat extend?

There's only one other way a slat could extend.

Through pilot action.

BOB MACINTOSH: This was something that had been

probably commanded in the cockpit,

and it was distressing to everybody.

NARRATOR: Why would a pilot do something

as dangerous as extending the slats at cruising speed?

Can't find anything in the captain statements

about slats and flaps.

NARRATOR: Investigators pore over the crew's statements.

They look for any mention that flaps and slats

were deployed mid-flight.

There's nothing from the other crew members either.

I have an idea.

Thanks for meeting with me.

NARRATOR: The NTSB consults with pilots

to learn why they might extend a flap or slat mid-flight.

Off the record?

Off the record.

Flaps, yes.

Slats, no.

Flaps?

NARRATOR: Investigators learn of an unauthorized procedure

used by some pilots that could save fuel and potentially time.

I thought that wasn't possible.

It is if you pop the breaker.

NARRATOR: The procedure involves deploying trailing

edge flaps by 2 degrees.

By pulling the circuit breaker for the slats,

the flaps can be extended while preventing

the slats from automatically deploying at the same time.

KEITH SHIBAN: It's one of those things everybody knows about,

but I've never heard anyone ever admit to it.

Ready?

NARRATOR: Investigators turn to the cockpit voice recorder

for evidence that TWA 841's pilots used

the unauthorized procedure.

PILOT: Let's get these passengers off the plane.

Hang on.

Did you start the tape at the beginning?

Yes, it's fully rewound.

Play it again just to be sure.

Let's get these passengers off the plane.

Plane's already on the ground.

NARRATOR: This can only point to one thing.

The pilots erased the tape.

The CVR contained no information

whatsoever, which was unfortunate to say the least.

We have to talk to Gibson.

NARRATOR: The team flies to California to question

Captain Gibson in person.

The Safety Board conducts public hearings.

They question the flight crew.

I told them I thought it was--

I said-- I said the airplane is going to roll.

And--

NARRATOR: The captain admits to routinely erasing the cockpit

voice recorder after every flight

even though that isn't a step on any checklist.

INQUIRER: Do you usually erase the recording?

I usually do.

Yes.

BARRY STRAUCH: It's just not credible that after the crew

had been through what they did, where they came within seconds

of dying, that the captain would erase the CVR as a matter

of habit or routine.

Something's wrong here.

NARRATOR: Captain Gibson's vague explanation doesn't

sit well with investigators.

Given what happened, they suspect the flight crew

attempted the unsanctioned procedure

and then tried to cover up their actions.

BARRY STRAUCH: The only reason he would erase the CVR was

to keep information from what he knew would be an investigation.

Investigators believed he had something to hide.

Maybe the FDR data can tell us more.

NARRATOR: The team studies TWA 841's flight data

to uncover any evidence that the crew attempted

a mid-flight flap extension.

Wow, it sure picks up speed.

In 44 seconds, the plane goes from 229 knots

to over 400 knots.

It's incredible.

Look at this.

NARRATOR: Close inspection of the data

gives the team an important clue.

That's odd.

Are those oscillations?

Yes, in the g trace.

NARRATOR: The g trace shows the level

of g-forces being put on the plane throughout the flight.

Let's get this section blown up.

BARRY STRAUCH: The g trace showed

the g-forces in the airplane were sort

of increasing and then decreasing

in a certain rhythmic pattern.

Very, very unusual.

The oscillations start at 39,000 feet just

before the upset.

They show up 1, 2, 3, 13 seconds before the roll starts.

It looks like the plane was really bouncing around.

What the heck?

NARRATOR: The data tells investigators

that the plane was moving erratically for 13

seconds before the first roll.

Here's a thought.

What if there's a flap and slat configuration

that could cause the vibration?

Let's find out.

We've reached 39,000 feet.

NARRATOR: NTSB investigators take an unprecedented risk

in an attempt to replicate the oscillations

recorded on TWA 841's g trace.

OK, we got more than a dozen configurations of maneuvers.

NARRATOR: They run a test flight to determine

if these anomalies resulted from a mid-flight slat extension.

Conducting a flight test would enable them to perform

maneuvers that could be compared to what the flight

data recorder recorded on 841.

229 knots.

OK, test number one.

Start by popping the breaker.

OK, slats are retracted.

Ready?

Flaps 2.

Flaps 2.

NARRATOR: Investigators try to match

the unusual oscillations by testing different flap

and slat configurations.

Test number two, flaps 5, slats remain retracted.

BARRY STRAUCH: NTSB investigators,

they'll do anything.

They love that stuff.

But I would have been pretty scared.

OK, test number nine, flaps 2, slats 2, 3, 6, and 7.

Flaps 2.

Ready?

You feel that?

NARRATOR: The flight test gives investigators

a tantalizing new lead.

BOB MACINTOSH: Investigators are very careful with flight tests.

To take the same aircraft, to record parameters carefully,

all those things have to factor into a flight test

in order to be of any use to the investigation.

Here's the data from the test.

Scenario number nine should match up.

NARRATOR: To confirm their results,

investigators compare the data with the FDR's g trace.

It's a perfect match.

BARRY STRAUCH: The flight test showed that extending the flaps

and slats would create in the airplane

oscillations found on 841.

So this was the test when the plane was shaking the most.

This is the one.

Flaps 2, slats 2, 3, 6, and 7 deploy and are

retracted 13 seconds later.

NARRATOR: They now have evidence that TWA 841's crew enacted

the unauthorized procedure of pulling a slat circuit breaker

and then deploying the flaps independently.

But if that's what the crew did, why did the slats deploy

and nearly bring down the plane?

What the heck?

KEITH SHIBAN: Those slats are going to shake because you're

going faster than the limiting air speed,

so I would expect it to get very noisy

and probably to buffet quite a bit.

NARRATOR: The test flight indicates

the slat circuit breaker was reset, which

caused the slats to deploy.

So we know the pilots popped the breaker

to enact the procedure, but why did they push it back in?

And why did it take the crew 13

seconds to realize the problem and then retract the slats?

NARRATOR: Investigators search for answers in all

of the crew's statements.

The lead flight attendant remembered

that the flight engineer was out of the cockpit

before the vibrations began.

Let me see that.

I'm going to take a bathroom break

and get rid of these trays.

MARK MOSCICKI: I noticed the cockpit door open,

and I saw the flight engineer coming out with the meal trays.

I didn't want him to think I was shirking my responsibilities.

I immediately met him.

Oh, let me get this for you.

Thank you.

MARK MOSCICKI: I was kind of surprised.

I'd never had a cockpit member actually bring

those trays back to the cabin.

They waited for us.

Well, that's it.

The flight engineer was out of the cockpit--

And out of the loop.

NARRATOR: Investigators now have a theory

about what happened in the cockpit

on the night of April 4th.

The flight engineer leaves the cockpit to return the trays.

With Banks out of the cockpit, Gibson launches

the unauthorized procedure.

The pilots deploy the flaps.

What do you say we get to Minneapolis a little quicker?

OK.

How are we going to do that?

Watch this.

Flaps 2.

Fancy trick.

Heard about it but I've never tried it.

Works like a charm.

BARRY STRAUCH: I could see the junior crew

member saying he's the boss.

Let's do it.

If he says it's OK, it's OK.

Today, that would be unthinkable.

Flight engineer returns and notices a breaker's popped.

What would any good flight engineer do?

He pushes it back in.

NARRATOR: Flight engineer Banks returns and notices the

slat circuit breaker is pulled.

He returns the breaker to the normal position

unaware that the captain had pulled it

deliberately to prevent the slats from extending

along with the flaps.

Exactly.

Normal operations resume.

With flaps set for 2, the slots extend automatically.

The cockpit begins to vibrate.

What the heck?

What did you just do?

What do you mean?

Just now, what did you just do?

The breaker was out.

I pushed it back where it should be.

Jesus.

Flaps up.

Flaps up, Scott.

Flaps up.

CAPTAIN: We're going over!

They bungled the maneuver.

NARRATOR: Investigators have figured out how TWA 841's crew

might have lost control of a Boeing 727,

but they're still missing a key piece of the puzzle.

How come slat number seven never retracted along

with the rest of the slats?

Metallurgical reporter is in.

NARRATOR: Investigators turn to results

from a metallurgical analysis of the T-bolt

from the number seven slat on TWA Flight 841.

They found some shearing.

Pre-existing metal fatigue.

NARRATOR: The team discovers a fracture in the T-bolt, which

would have caused the slat to sag on the inside

when extended.

BARRY STRAUCH: The slat is kept in the forward part

of the wing, which gets all of the air forces

as the airplane progresses.

At 0.8 times the speed of sound, that's

going to be enormous, enormous air pressure.

So all that air pressure twists the sagging slat.

NARRATOR: Slat number seven can no longer retract.

Under the extreme air loads of a diving plane,

it finally rips off.

Investigators finally understand how TWA 841 went

into a horrifying dive above Saginaw, Michigan,

on the night of April 4, 1979.

I'm going to take a bathroom break.

I'll grab these trays.

NARRATOR: Unaware the captain was conducting

an unsanctioned procedure, disengaging the slat circuit

breaker to deploy only the flaps,

the flight engineer resets the popped breaker.

What did you just do?

What do you mean?

NARRATOR: Precious seconds pass as the captain tries

to figure out what's happened.

Meanwhile, the aircraft flies at a high speed with its flaps

and slats extended perilously.

The captain, passengers, and flight attendants

talked about feeling the vibrations

in the airplane caused by extension of the slats

and flaps at 39,000 feet.

Flaps up.

Flaps up, Scott.

Flaps up.

I have control.

NARRATOR: The flaps and slats retract

except for the damaged number seven slat in the right wing.

BARRY STRAUCH: The number seven slat, if it's extended,

you're going to have more drag on the right side

than on the left wing, and that's going

to cause that wing to descend.

In other words, it's going to put

the airplane in a right turn, which is exactly what happened.

Come on, level up.

NARRATOR: But it's too late.

Little does the crew know slat number 7 is still extended,

keeping the plane in a roll.

We're going over.

NARRATOR: TWA 841's flight crew is unable to regain

control of the aircraft.

Then in a stroke of incredible good luck,

slat number seven rips off the plane just

8,000 feet above the ground.

BOB MACINTOSH: The departure of the slat

allowed the return of controllability

to the aircraft.

NARRATOR: With the wing symmetry partially restored

and the landing gear deployed, it's

just enough to slow the plane and allow the crew

to regain control and ultimately land

the battered 727 at Detroit.

Reverse thrust.

NARRATOR: The NTSB recommends additional warnings

to flight crews about the dangers of high speed

deployment of flaps and slats.

No punitive action is taken against the crew.

BOB MACINTOSH: NTSB conclusions are not a criminal thing.

They're not a blame thing.

They're trying to prevent the next accident

by offering up a probable cause that needs to be corrected.

NARRATOR: The pilots maintained their innocence,

claiming they did not deliberately

extend the flaps mid-flight.

Captain Gibson took it to his grave with him in 2015.

The other two guys aren't talking.

NARRATOR: Following this accident,

newer planes now come equipped with flight computers that

prevent the deployment of flaps and slats

above certain altitudes.

MARK MOSCICKI: There was speculation

over manipulation of controls, all that sort of thing.

I've given a great deal of thought over the past 41 years

and have come to the conclusion that I'll

never know what happened.