Original subtitles

We're going over.

A Boeing 727 spirals out of control over Michigan.

You're watching the world spinning outside the window. This would be sheer

stark terror.

Airspeed is 320.

350.

Come on! Come on! No, no, no.

Investigators track down pieces of debris.

Slot number seven.

Broken in two.

And interview fellow pilots.

Off the record.

Off the record.

They even risk their own lives.

Okay, test number nine.

To find out what caused TWA Flight 841's uncontrollable plunge.

You feel that?

It was insane.

My hands are still shaking.

44-year-old Captain Harvey Hoot Gibson has just returned from the most

harrowing flight of his life.

Tell me what happened.

A representative from the Federal Aviation Administration takes his

statement.

We're cruising over Michigan.

That sure is a strong headwind.

Captain Gibson is a trained stunt pilot who has a clean 16-year record with

Transworld Airlines.

Do a ground speed check, will you?

Sure thing, Hoot.

First Officer Scott Kennedy has been flying with TWA for 13 years.

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

Flight engineer Gary Banks is an Air Force veteran who's been with TWA for

the last 10 years.

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.

Roger, TWA 841, climb and maintain flight level 390.

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 you a better ground speed.

I can take that off your hands.

27-year-old Mark Mositsky is today's lead flight attendant.

He and three other attendants look after the 82 passengers on board.

It was an evening flight.

I was leaving JFK.

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

Everything was absolutely smooth.

They're flying the narrow-body Boeing 727 aircraft.

The 727 was massively overbuilt. It was a very sturdy airplane.

It was like driving a sports car or a fighter plane. It was very light on the

controls. It had that feeling that you could just put it wherever you wanted

it.

After a 45-minute delay in New York, the flight to Minneapolis will take about

three and a half hours.

They programmed 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 adjusted.

Everything looks good.

After meal service, Mositsky takes a moment to eat his own meal.

I sat in my jump seat.

Very shortly, however, there was a very abrupt buffeting of the aircraft.

It wasn't turbulence.

What the heck?

The captain noticed something was strange. The wing had started to drop

and the autopilot was compensating for that.

I got control.

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?

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'd 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 sheer stark terror.

Shutting the throttles.

The captain tries to slow the plane to regain control.

But the aircraft isn't responding.

Get him up! Get him up!

Desperate to slow the plane, Gibson deploys the speed brakes.

Speed brakes are flight control surfaces that increase drag and improve roll

control.

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!

But deploying the speed brakes proves useless.

I got off on my jump seat to see if perhaps the engine was on fire.

And I never made it.

We're going over!

High above Saginaw, Michigan, the Boeing 727 drops into an

uncontrolled dive.

and spins upside down.

Something was extremely wrong.

There seemed to be no control of the airplane.

People were just absolutely terrified.

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

TWA 841, this is center.

TWA 841, center.

Jesus. Something is seriously wrong.

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?

The controllers watch helplessly as TWA 841 plummets towards the ground.

Once the nose comes down on an airliner, they want to pick up speed in a hurry,

if you point it at the ground.

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.

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.

There's me at 320.

350. I can't. I can't.

TWA-841 is spiraling towards the Earth at a rate of 540 feet per second.

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, on 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.

No, no, no!

Come on, baby, pull up!

We were falling so fast.

Captain Hoot Gibson recounts his recent nightmare piloting TWA Flight 841 over

Michigan.

Airspeed is 390!

But Gibson isn't giving up.

Come on, baby, pull up!

He has an idea.

Put the gear down!

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.

You know, suddenly we were climbing.

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

You would feel like you are being crushed. The average person would feel

like they weighed 900 pounds.

Scott, give me altitude.

Gary, pitch and airspeed.

It's 200 feet. Jesus, which way is up?

Moon.

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.

You can sort the rest out later, but get away from the ground.

TWA 841 has come within seconds of impact and now climbs back towards the

night sky.

Airspeed is 160.

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 110.

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.

As the crew recovers from the terrifying incident, they assess damage to the

aircraft.

We've got a flag for the lower yard damper.

A deafening rattle makes a tense situation worse.

Okay, I'm going to fly the airplane.

You guys start running the emergencies.

He was a good captain. He had them diagnose the problem.

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

Turn pump emergency switches to depressurize and check quantity.

The fluid is zero. It's all gone.

With a damaged hydraulic system, the aircraft is severely impaired.

Okay, we gotta land.

Detroit is our best option.

Okay.

We're 60 miles out.

When they decided to divert, they selected Detroit with reasonable

weather, long runways. There's a developed airport with crash fire

rescue. Center 841.

Go ahead, CWA 841.

Okay, 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 160 vectors to Detroit.

Okay, 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.

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 a complete direction.

15 miles from Detroit now.

Nice and easy.

Give me flaps 15.

Unaware of the extent of the damage, Gibson tests the aircraft's

controllability. Flaps 15.

Whoa, whoa, whoa.

Track the flaps.

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 are going to

go very fast.

Much faster than you would ever land this airplane.

Going fast, there's no other way.

This is going to be our only approach.

With ruptured hydraulics and a compromised plane, the pilots of TWA 841

have only one shot at landing at Detroit Airport.

Landing checklist complete. Coming through 200 feet.

I was pretty convinced that we'd probably be scraping down the runway.

Lots of sparks and flame.

50.

40.

30.

Race.

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.

He's just put this badly damaged airplane down at about 90 knots

faster than a normal landing speed.

This guy is good.

He's really good.

Hoot.

It's unbelievable.

What the heck went so wrong with that plane?

I haven't the faintest idea.

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.

The flight data recorder and cockpit voice recorder are removed from the

aircraft and sent for analysis Let's check that out

Slot

number seven is missing

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.

It's pretty banged up.

Investigators wonder why the slat came off.

The hydraulic lines are ruptured too.

Logical outcome for a slat tearing off.

Looks like the actuator for the slat is damaged.

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.

No scrape marks inside either.

Investigators uncover an important clue.

Slat came off in an extended position.

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.

A slat should never deploy at cruising speed.

Maybe this slat extended by accident.

Only way to know for sure is to test the hydraulic system.

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.

Investigators run through every flap setting possible.

All right, let's wrap it up.

Everything's working fine.

The functional test demonstrated that the hydraulic system worked. It did not

cause an uncommanded slat deployment.

Here's what we got from Boeing.

Did the locking mechanism on the 727's wing somehow fail, releasing the slat?

For a slat to unlock accidentally, the pin inside the actuator must be

subjected to more than 70 Gs of force.

70 Gs?

There's no way the locking mechanism experienced that level of stress.

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.

Investigators get a break when debris from Flight 841 is recovered seven miles

north of Saginaw, Michigan.

Slot number seven.

Broken in two.

Look at this.

This is the number seven slat's T-bolt.

T-bolts are part of the slat track assemblies.

The number seven slat's 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.

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.

This was something that had been probably commanded in the cockpit, and

it was distressing to everybody.

Why would a pilot do something as dangerous as extending the slats at

cruising speed?

Can't find anything in the captain's statements about slats and flaps.

Investigators review 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.

The NTSB consults with pilots to learn why they might extend a flap or a slat

mid-flight.

Off the record.

Off the record.

Flaps, yes.

Slats, no.

Flaps?

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.

The procedure involves deploying trailing edge flaps by two degrees.

By pulling the circuit breaker for slats, the flaps can be extended while

preventing the slats from automatically deploying at the same time.

It's one of those things everybody knows about, but I've never heard anyone ever

admit to it.

Ready?

Investigators turn to the cockpit voice recorder for evidence that TWA-841's

pilots used the unauthorized procedure.

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.

The plane's already on the ground.

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 the team flies to california to question captain

gibson in person

the safety board

conducts public hearings they question the flight crew i

told him i thought it was i said i said the airplane's gonna roll and uh

The captain admits to routinely erasing the cockpit voice recorder after every

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

Do you usually erase the recorder? I usually do, yes.

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 manner of habit or routine.

Something's wrong here.

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.

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.

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.

Close inspection of the data gives the team an important clue.

That's odd.

Are those oscillations? Yes, in the G-trace.

The G-trace shows the level of G-forces being put on the plane throughout the

flight.

Let's get this section blown up.

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.

Oscillation starts at 39,000 feet just before the upset.

In short, 1, 2, 3, 13 seconds before the roll starts.

Wow, it looks like the plane was really bouncing around.

What the heck? 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 slap configuration that could

cause the vibration Let's find out

We've reached

39,000 feet

NTSB investigators take an unprecedented risk in an attempt to replicate the

oscillations recorded on TWA-841's G-trace.

Okay, we've got more than a dozen configurations and maneuvers.

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.

Okay, test number one.

Start by popping the breaker.

Okay, slats are retracted.

Ready?

Flaps two.

Flaps two.

Investigators try to match the unusual oscillations by testing different flap

and slat configurations.

Test number two.

Flaps five, slats remain retracted.

NTSB investigators, they'll do anything.

They love that stuff.

But I would have been pretty scared.

Okay, test number nine.

Flaps 2, slats 2, 3, 6, and 7.

Flaps 2, ready?

You feel that?

The flight test gives investigators a tantalizing new lead.

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 tests.

Scenario number nine should match up.

To confirm their results, investigators compare the data with the FDR's G-trace.

It's a perfect match.

The flight test showed that extending the flaps and flats would create, in the

airplane, oscillation sound on 841.

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

This is the one.

Flaps two.

Slats 2, 3, 6 and 7 deploy and are retracted 13 seconds

later.

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?

Those slats are going to shake because you're going faster than the limiting

airspeed. So I would expect it to get very noisy and probably to buff it quite

a bit.

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?

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.

I'm going to take a bathroom break.

I'll get rid of these trays.

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. I was kind of surprised that I had 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.

Investigators now have a theory about what happened in the cockpit on the

night of April the 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?

Okay. How are we gonna do that?

Watch this.

Flaps 2?

Fancy trick.

Heard about it, but I've never tried it.

Works like a charm.

I could see the junior crew members saying, he's the boss, let's do it.

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

Today, that would be unthinkable.

Flight engineer returns and notices the breaker's popped.

What would any good flight engineer do?

He pushes it back in.

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 two, the slats 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 how to push it back where it should be.

Jesus.

Flaps up.

Flaps up, Scott.

Flaps up.

We're going over.

They bungled the maneuver.

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 report is in.

Investigators turn to results from a metallurgical analysis of the T-bolt

from the number 7 slat on TWA flight 841.

Found some shearing.

Pre-existing metal fatigue.

The team discovers a fracture in the T-bolt.

which would have caused the slat to sag on the inside when extended.

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.

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 the 4th, 1979.

I'm going to take a bathroom break. I'll grab these trays.

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?

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 the airplane caused by extension of the slats and flaps at 39

,000 feet.

Flaps up. Flaps up, Scott.

Flaps up.

I have control.

The flaps and slats retract.

Except for the damaged number seven slat on the right wing.

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.

But it's too late.

Little does the crew know, slat number seven is still extended, keeping the

plane in a roll.

TWA 841's flight crew is unable to regain control of the aircraft.

Then, in a stroke of incredible good luck, SLAT number 7 rips off the plane

just 8,000 feet above the ground.

The departure of the SLAT allowed the return of controllability to the

aircraft.

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!

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.

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.

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.

Following this accident, newer planes now come equipped with flight computers

that prevent the deployment of flaps and slats above certain altitudes.

There was speculation over manipulation of controls, all that sort of thing.

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

and have come to the conclusion that I'll never know what happened.