Original subtitles

- Rotate.

(narrator): Just seconds after takeoff from Addis Ababa...

- Gear up.

- ...the pilots of Ethiopian Airlines Flight 302

are faced with an emergency.

- Master caution, anti-ice.

- You're literally fighting to maintain control of the jet.

- Stab trim cutout? - Yes, yes, do it!

- But the procedure they've been taught

for the Boeing 737 MAX 8...

...doesn't work.

- They knew what to do and they tried to do it.

- Investigators are astonished.

If the pilots knew the proper procedure,

why didn't it work?

- Boeing didn't say anything about the trim wheel

being difficult to move.

(whirring)

- Could the pilots have been misled

about how to save their plane?

- They still left the Boeing MAX unairworthy,

and it cost the life of my daughter and 157 people.

(intense music)

- Mayday, mayday!

(rapid beeping)

(indistinct radio chatter)

(electricity crackling)

(narrator): Boarding has commenced for 149 passengers

on a short flight from Addis Ababa, Ethiopia,

to Nairobi, Kenya.

- Perfect, thank you.

(man): This was really a UN shuttle flight.

There was a UN environmental conference

happening in Nairobi so,

there were about a couple dozen people on the plane

who were headed to that conference.

- All right, ground equipment is removed

and engine area is clear.

- The captain on today's fight is 29-year-old Yared Getachew.

- The captain was considered

one of the best pilots in the airline.

He had 8,000 hours

which was unheard of for someone that young.

- Before Start checklist complete.

Request pushback clearance.

- Ground, Ethiopian 302 requesting pushback clearance.

- 25-year-old Ahmed Nur Mohammed is the First Officer.

(man on radio): Ethiopian 302 you are cleared to push.

(Peter): Ethiopian Airlines was considered

the model airline in Africa.

It had the best run training school,

and it had a well-oiled system

for bringing new pilots into the airline.

(narrator): They're on a Boeing 737 MAX 8,

a brand-new passenger jet

that's already at the centre of a major investigation

in Indonesia.

(tense music)

- Five months earlier,

a MAX 8 crashed into the Java Sea

killing all 189 people on board.

That accident is still under investigation.

Just before 8:30AM,

Flight 302 taxies towards the runway

at Addis Ababa's Bole International Airport.

- Ethiopian three-zero-two,

cross runway zero-seven left at alpha

and hold short of zero-seven right.

(First Officer): Cross zero-seven left at alpha

and hold short, Ethiopian three-zero-two.

- Pre-Takeoff checklist, please.

- Landing lights.

- On.

- Among the passengers on today's flight

is 24-year-old Canadian, Danielle Moore.

She is travelling to the UN summit.

- She really astonished us when she told us that

she would be going to the United Nations

Environmental Assembly in Nairobi.

And she was selected out of a number of people.

We thought this was so tremendous.

- Flight 302 reaches Runway 07 Right,

the longest runway at the airport.

(First Officer): Ethiopian three-zero-two

ready for departure.

- Three-zero-two, clear for takeoff,

runway seven right.

Have a good flight.

- Ready? - Ready.

(uplifting music)

Takeoff thrust set.

Speed increasing.

(heartbeat pulsing)

(narrator): Flight 302 departs on time.

The 725-mile flight to Nairobi

should take just over two hours.

- The MAX 8 was designed for routes like this.

It's a short hop, quick turnaround plane.

It also had much more fuel efficiency

compared to the previous version of the MAX, about 20 percent.

(automated voice): V1.

- Rotate.

Positive rate.

- Gear up.

- Gear up.

(narrator): Less than ten seconds after takeoff,

the pilots get a stick shaker warning,

indicating that they're in danger of losing lift

and could stall.

- If you experience a stall right after departure,

it can be extremely serious.

- Captain Getachew reduces his plane's pitch angle

in an effort to prevent a stall.

(woman): If you are taking off and you get a stick shaker,

crews are going to be hesitant, you know,

to push their nose over

because they're close to the ground.

(beeping)

(First Officer): Master caution, anti-ice.

- Okay...

- When master cautions come on,

the first thing is to diagnose what's occurred

and consider what implications it has on the flight.

(sighs) - What's going on?

- Captain Getachew doesn't understand

what's behind the multiple warnings.

- There's a lot going on here

and it's a very distracting, loud environment

with the stick shaker going.

Where do you start

to deal with this complex emergency that you have?

- Flight 302 is only a few hundred feet off the ground

as the pilots struggle to understand the problem.

As far as passengers are concerned,

this is a routine takeoff.

(tense music)

(stick whirring)

- Okay, contact radar.

- Captain Getachew decides to continue climbing.

- If you have a problem,

the thing you wanna do is get it away from the ground

where you can sort through your problems.

- Radar, Ethiopian three-zero-two, good morning.

Crossing 8,400

and climbing to three-two-zero.

- First Officer Mohammed reports his altitude,

8,400 feet above sea level,

which is only 750 feet above the ground.

- Continue climb to flight level three-four-zero.

(First Officer): Climb to three-four-zero,

Ethiopian three-zero-two.

- Flaps up.

- Flaps up.

(narrator): Retracting the flaps

should help the aircraft climb...

...but it has the opposite effect.

1,500 feet from the ground,

the jetliner with 157 people on board begins to fall.

- We are having flight control problems.

(automated voice): Don't sink. Don't sink.

- You've gone from a series of cautions,

a series of system malfunctions,

now into a flight control problem

where you're literally fighting to maintain control of the jet.

- Passengers now sense that there is something wrong.

- One woman whose brother was on the airplane

and he called her soon after takeoff.

He knew something was wrong.

The plane was not climbing the way aircraft normally do.

- The 737's nose continues to pitch down.

- Trim...

- Captain Getachew uses the trim switch to level his plane.

The trim switch controls the position

of the horizontal stabilizer,

keeping the plane balanced during flight.

It can be used to adjust the pitch of the airplane.

Captain Getachew manages to raise the nose slightly,

but not for long.

The plane dips again,

bringing it closer to the ground.

(automated voice): Too low. Terrain.

(narrator): And the pilots are struggling.

(automated voice): Too low. Terrain.

- Now you start dealing with how do we regain control,

and to keep the nose up while we sort through this.

And that's where the time can become critical.

(music intensifies)

(straining) - Pull up. Pull up!

(narrator): Less than three minutes after takeoff

and only 1,800 feet above the ground,

the pilots of Ethiopian Airlines Flight 302

are desperately trying to get their plane to climb.

- Pull up!

- Okay, advise we maintain 6,500.

We have a flight control problem.

- They're trying to reach the minimum safe altitude

surrounding the airport.

(First Officer): Ethiopian three-zero-two,

we'd like to maintain 6,500.

We have a flight control problem.

- Say again?

- We have a flight control problem

and we'd like to maintain 6,500.

- Approved and report intention.

- We'll call you. Ethiopian three-zero-two.

(John): First and foremost they said,

"Okay, we have a flight control problem,"

and that says

get other airplanes away from me.

And that was a very appropriate thing to do.

- Set 6,500.

- 6,500 set.

(beeping) - Speed!

(narrator): As they fight to climb to 6,500 feet,

the plane's speed becomes dangerously high.

They try to raise the plane's nose further

to decrease speed.

- Pitch up with me.

- Even with both pilots pulling back on their control columns,

the plane refuses to climb.

- The forces necessary to hold that yoke are increasing

and they're increasing quite rapidly.

- Less than minutes into the flight,

Captain Getachew decides to turn around.

- Request a return vector.

- Radar, Ethiopian three-zero-two

requesting vector back to airport.

(Peter): There was a lot going on in that cockpit.

There were indicators going off

showing a disagreement in altitude,

disagreement in airspeed.

The stick shaker was going off.

So the best thing for them to do was to turn around.

- Confirm, do you want to hold or make an approach?

- Wish to commence approach. (beeping)

- Turn right to two-six-zero.

- Two-six-zero.

- The pilots have managed to get their plane

to 6,000 feet above the ground.

- Pitch up with me. Not enough pitch.

Not enough pitch!

- ...but now it starts to plummet.

(automated voice): Sink Rate.

(passengers screaming)

(air whooshing)

(Captain): Pitch up! Pitch!

(automated voice): Terrain, terrain. Pull up.

(Captain): Mayday! Mayday! Mayday!

(automated voice): Terrain, terrain. Pull up.

(pilots screaming)

(intense music)

(metal clattering)

- Flight 302 slams into the ground

just 30 miles from the airport.

It's the second MAX 8

to have crashed in less than five months.

- In today's world,

even a single accident is an extreme rarity.

To have two within five months, it is inconsistent

with the level of safety of modern airliners.

(melancholic music)

- Everyone wants an answer to the same question:

Is there something wrong with Boeing's latest jet?

- We begin tonight with the mystery

swirling around a deadly plane crash overseas.

The new Boeing 737 crashing

just minutes after takeoff in Ethiopia.

157 people were on board the flight

and there were no survivors.

- News of the Ethiopian Airlines crash

quickly makes headlines around the world.

- The phone rang and my wife answered it,

and I recall hearing her scream

and saying, "Danielle is dead."

My hearing her shriek

and saying those words, it was...

it was the death of me, too. I died.

This is the last thing that any father wants to experience.

- A team from Ethiopia's Accident Investigation Bureau

is tasked with finding out why Flight 302 crashed

just five minutes after takeoff.

- To make a crater like this,

the speed must have been tremendous.

- Much of the wreckage is buried in a crater

more than 30 feet deep.

(Lorenda): You can tell that it was in a high energy state,

that just due to it creating a crater,

that it had to have some kind of angle to it.

- The plane's two black boxes are quickly found.

The Ethiopian government decides to send them

to France's investigative agency to have the data downloaded.

In Indonesia, the investigation into the previous MAX 8 accident

is still underway as investigators get the news

about the Ethiopian Airlines accident.

- First time I heard about Ethiopian Flight 302 crash,

I was shocked, knowing that another 737 MAX has gone down.

- The Indonesian accident involves Lion Air Flight 610,

a MAX 8 that took off from Jakarta

with 189 people on board five months earlier.

- I was afraid that the accident was caused by similar issue

with the Lion 601 that we were investigating.

(beeping)

- The Indonesian pilots also began experiencing warnings

shortly after takeoff,

and also reported having flight control problems.

Following a series of altitude fluctuations,

the pilots attempted to return to the airport.

The 737 plunged into the Java Sea

11 minutes after takeoff.

The investigation into that accident

has zeroed in on an electronic system known as MCAS,

the Maneuvering Characteristics Augmentation System.

- It's a piece of software in the flight control computer

that directs the stabilizer to push the nose down.

- Investigators in Indonesia have learned that MCAS

was added to the MAX 8 to compensate for a design problem.

- In order to achieve the fuel efficiency

Boeing wanted to,

it needed to put bigger engines on the airplane

and in certain flight conditions,

the nose had a tendency to pitch up,

and that's why MCAS was introduced.

- If the system sensed the plane's nose

was pitched too high,

it would automatically adjust the plane's stabilizer

to lower the nose.

Indonesian investigators have determined that a faulty sensor

on the Lion Air flight led MCAS to conclude

the plane was climbing more steeply than it was,

causing it to activate repeatedly,

until the plane hit the water.

(automated voice): Terrain. Pull up.

- We found that there was some issue

with the design of the system.

(narrator): There are 387 MAX 8's flying worldwide

with another 5,000 on order.

It's rapidly becoming one of Boeing's

most successful airliners.

(Peter): The MAX 8 was the fastest selling aircraft

in Boeing's history.

Airlines were really drawn to the fuel efficiency.

- The pressure is on investigators to determine

if a flaw with MCAS also caused the Ethiopian accident.

(Lorenda): There was worldwide attention to this investigation.

The whole team was under a lot of pressure to get answers

and to find out what happened.

)

- Ethiopian investigators start with

the last people who spoke to the crew of Flight 302,

air traffic controllers.

- Thanks for your time.

Can you take me through the flight?

- Normal taxi and takeoff.

Nothing unusual until two-and-a-half minutes later

when they reported a flight control problem.

(First Officer): Ethiopian three-zero-two,

we'd like to maintain 6,500,

we have a flight control problem.

- They asked to maintain the current heading

and requested permission to hold at 6,500 feet.

- And you approved the request?

- I did, yes sir.

(narrator): All investigators know is that the pilots

had a flight control problem that developed early

and prevented the crew from continuing the flight.

- They're aware that they were dealing with

a flight control issue.

It would have been helpful if they could have identified

which control surface they were having the problem with.

- The team turns to Flight 302's radar track

to understand the sequence of events.

- Slow, shallow climb out.

Now, look here.

Instead of climbing, they lose altitude,

regain it, then lose more.

- Instead of continuing to climb or to maintain an altitude,

there was actually dips in the altitude.

- The radar data paints a picture

of a crew struggling to keep its plane in a climb.

(automated voice): Don't sink. Don't sink.

- They're trying to get to 6,500 feet

but never get higher than 6,200.

And they're starting to make a turn back to the airport.

Now they're in a dive,

descending at 33,000 feet per minute.

- The speeds were at the maximum for this aircraft.

The intensity inside the plane must have been terrifying.

- Let me see the Lion Air track please.

A slow climb,

a series of altitude fluctuations...

...a turn back to the airport, and a rapid descent.

They're pretty close.

- The fact that this plane crashed

almost immediately after takeoff in very similar circumstances

raised a lot of questions in everyone's minds.

- Investigators turn to a key piece of the wreckage

for confirmation that MCAS played a role in the accident.

- It's in pretty good shape. We got lucky.

- A jackscrew, the device that controls the position

of the plane's horizontal stabilizer, is recovered.

(digital blipping)

A ball nut moves along the jackscrew

to help adjust the plane's pitch.

- Five inches.

Full nose down trim.

- The evidence shows that the plane

went into its final dive because the stabilizer

had moved to an extreme nose down position.

- Full nose down trim is not something

that you ever see in the normal flight of a 737.

In the 15 years that I flew it,

I don't know that we ever got even close to full nose down.

- The Lion Air flight is identical.

A pitch trim of 1.5 degrees resulting in a rapid descent.

The pilots wouldn't do that.

- The jackscrew all but confirms

that Ethiopian Airlines Flight 302

and Lion Air Flight 610

had the same cause,

a malfunction of the plane's electronic MCAS system.

- That was literally the smoking gun

that definitively told them

what had happened to the airplane.

- There's now enough evidence

to convince aviation authorities around the world

that the MAX 8 presents a risk to passengers.

- We're gonna be issuing an emergency order of prohibition

to ground all flights of the 737 MAX 8.

- The question now facing Ethiopian investigators is

how could this have happened again?

- These documents came out four months ago.

- Following the accident in Indonesia,

both Boeing and the FAA issued bulletins

advising pilots of the steps to take

if MCAS began forcing the nose down.

The documents advise pilots to follow the existing procedure

for a malfunctioning trim system and disengage the autopilot,

set the stabilizer trim switches to cutout,

and to use their manual trim wheel

to counteract the automatic downward stabilizer movement.

- Boeing and the FAA felt that the airworthiness directive

was all pilots needed to be able to recover from

what they thought would be an extremely rare event.

- Did the pilots know about this procedure?

- You'd hope so.

(John): The airline has an obligation

to train the pilots

to ensure that there is a sufficient understanding

of what the information is trying to tell them

so that they act appropriately.

- We incorporated the Boeing bulletin

into our flight manual.

- Were your pilots advised of the revision?

- All our pilots were fully briefed, of course.

- The pilots of Flight 302

knew the procedure for disabling MCAS.

The question is, did they follow it?

- Here it is, let's load it up.

- The cockpit voice recording

from Ethiopian Airlines Flight 302

has been successfully downloaded by technicians in France.

- Okay, let's hear it.

(automated voice): V1.

(First Officer): Rotate. Positive rate.

(Captain): Gear up.

- Takeoff roll is normal.

(narrator): Investigators listen for clues that can explain

how MCAS brought down the plane.

(First Officer): Climb to three-four-zero.

Ethiopian three-zero-two.

(Captain): Flaps up.

- Flaps up.

(narrator): The MCAS system is designed to activate

only when it senses that three conditions are met:

nose up, flaps fully retracted,

and autopilot off.

(alarm)

- That's the autopilot disconnecting.

- Okay, so now they've met the three conditions

for MCAS activation.

- Investigators continue listening for evidence that

MCAS activated, pitching the plane downwards.

(Captain): We're having flight control problems.

- Right on cue.

(stick whirring)

(automated voice): Don't sink. Don't sink.

- He's losing altitude.

- Don't sink. Don't sink.

- MCAS is pushing the nose down.

(Captain): Trim...

Come on, trim with me. Trim up. Trim up, trim up!

Come on, trim up! (grunting with effort)

(narrator): Investigators hear the pilots struggling

to trim their plane nose up.

- So you begin to get this tug of war

between the pilot trimming nose up

and MCAS trimming nose down.

But MCAS is relentless. It doesn't stop.

- Trim! Trim up.

- The team then hears an exchange

that transforms the investigation.

- Stab trim cutout? Stab trim cutout?

- Yes, yes, do it!

- Stab trim cutout.

- Can you pause for a second?

- They did it.

They set the trim switches to cutout,

exactly as Boeing advised them to do.

(Lorenda): I think that's the surprise.

The crew attempted to do that procedure

and it wasn't successful.

- The autopilot disengaged. We heard the alarm.

They set their stabilizer trim switches to cutout.

Now they need to manually trim to get their nose back up.

Let's hear.

(Captain): Pitch up, pitch up, pitch up.

Do it with me.

(straining) Is the trim engaged?

(First Officer): No. Shall I try manually?

(Captain): Try it!

- The 737 has a manual backup

about how to move trim using cables.

And the wheel has actually got a handle in it

where you can manually trim it.

(straining) - It's not working.

- Not enough pitch. Not enough pitch.

(narrator): But the pilots are not able

to adjust the pitch manually.

- They don't physically have enough strength

to move the horizontal stabilizer

via the manual trim wheel.

- They're trying to do this.

- But it doesn't sound like it's working.

- And then they come up with a solution

that seals their fate.

(Captain): Put them up.

- No. Oh, no. No.

(narrator): Unable to pitch the plane up manually,

the pilots make one final desperate move.

They re-engage the automatic trim

to help move the stabilizer.

(Lorenda): Unfortunately, that wakes the beast.

And then it's gonna sit there

and it's gonna trim it down one more time again

so it works against them.

(automated voice): Caution. Terrain.

(Captain): Pitch up! Pitch up! Pitch up!

- There was no way to control the airplane.

The pitch was going to continue to go nose down.

(alarm beeping)

(automated voice): Caution. Terrain.

Terrain, terrain. Pull up, pull up.

(Captain): Mayday! Mayday! Mayday!

(pilots screaming)

(radio static)

- They knew what to do. They tried to do it.

- But for whatever reason, it didn't work.

(narrator): The Ethiopians have made a stunning discovery;

one they quickly share with the world.

- The crew performed all the procedures repeatedly,

provided by the manufacturer,

but was not able to control the aircraft.

- Stab trim cutout? Stab trim cutout?

- Yes, yes, do it!

- Investigators are left with a burning question.

- Stab trim cutout.

- If the pilots did what Boeing advised,

why weren't they able to pull out of the dive

that MCAS put them into?

(Captain): Pitch up!

(intense music)

- Investigators turn to the flight data recorder

from Ethiopian Airlines Flight 302

to better understand why MCAS was activated,

causing the plane to crash.

- Right here, ten seconds after takeoff.

Readings for angle of attack, airspeed, and altitude

begin to diverge.

- MCAS is only supposed to activate

when the MAX 8 reaches an extreme angle of attack,

or high-pitch angle.

(digital blipping)

A sensor on each side of the airplane

calculates the angle of attack

by measuring the plane's angle into the oncoming air.

- Sure looks like a sensor issue.

The captain's side can't be right.

- Absolutely.

- The data shows a steep spike

in the captain's angle of attack reading.

- That explains the stickshaker. - Yup, false alarm.

- The plane was never in danger of stalling.

The warning was triggered by faulty pitch data

from a malfunction in an angle of attack sensor.

- The captain's side shows a pitch up

of as much as 74 degrees.

The first officer's side is correct,

a steady 15-degree pitch.

- Investigators discover

the malfunction was only on the captain's side.

- So, up until this point, the flight is actually fine.

- On the Ethiopian airplane,

something happened to that sensor

just shortly after takeoff.

- So one faulty sensor brings down the plane?

(Lorenda): A single failure should not be catastrophic.

There should be backup, there should be redundancies

so if there is something that occurs within the system

that the crew should be able to counter it.

- The FDR data can show us when the MCAS activated.

- The team studies how MCAS behaved for Flight 302.

- Here, here, and here.

The plane pitches down even though the pilots

are pulling up on their control columns.

- The faulty sensor led to four separate activations

of the MCAS system,

driving the plane's nose down

as the pilots were trying to pitch up.

The fourth MCAS activation pitched the nose down

when the plane was only 6,000 feet above the ground.

It put the plane into a steep and rapid descent...

- Pitch up! Pitch up!

- ...from which the pilots could not recover.

(automated voice): Pull up.

(metal clattering)

(narrator): So why couldn't the pilots disable the MCAS

even though they followed the recommended procedure?

Investigators examine Flight 302's speed

leading up to the crew's attempt to override the MCAS.

- They lift off at 140 knots. Absolutely perfect.

But as they climb, their speed increases.

It reaches 340 knots

by the time they try to use manual trim.

The overspeed warning sounds here

and stays on for the rest of the flight.

(John): Normally, you would be in the 220-250 knot range.

This was a hundred knots plus faster than that.

- No wonder they couldn't move their trim wheel.

- The speed increased the air load on the stabilizer,

making it impossible for the pilots

to move it manually with their trim wheel.

(straining) - It's not working.

- Once you get to high speed,

you're no longer strong enough as a human to move it.

- Why such high speed?

- Have a look at their auto-throttle setting.

They lift off

with the auto-throttle in takeoff mode.

Right about here,

the auto-throttle should be pulling back from takeoff thrust

to climb thrust.

But that never happens. It stays at max takeoff thrust.

- Same sensor, I guess. - Uh-huh.

- The auto-throttle is also connected

to the left-side angle of attack sensor.

- Once the sensor failed,

that disabled the auto throttle system,

so the power stayed where it was.

- We're having flight control problems.

- As they dealt with the escalating crisis,

the pilots didn't notice that their thrust levers

remained at maximum takeoff power.

- 737s are very powerful jets.

And they will continue to accelerate very rapidly

if you don't reduce the power.

- Boeing didn't say anything about the trim wheel

being difficult to move.

- Or about airspeed.

- The Ethiopian investigators now turn their attention

to the advice Boeing gave pilots after the Lion Air accident.

- The Lion Air flight

had necessitated this airworthiness directive.

So the question becomes, was that enough?

- No mention of MCAS.

No mention of how much force may be needed to trim manually.

No mention of airspeed.

- That's a lot to leave out.

- The investigation has uncovered shortcomings

in the guidance Boeing provided following the Lion Air accident.

In Indonesia, investigators have discovered

that a maintenance error led to the failure

of the crucial angle of attack, or A-O-A sensor,

in the Lion Air Accident.

What caused its failure on the Ethiopian flight?

Investigators examine maintenance records

for any evidence of trouble.

(Lorenda): So the Ethiopian investigation did look into

the maintenance to the sensor. There was none.

It's the original install to the airplane.

- They do uncover several other maintenance issues

on the four-month-old plane.

- That's a lot of electrical faults for a brand-new airplane.

- The Ethiopian team suspects the A-O-A sensor on Flight 302

failed due to an underlying electrical fault.

The sensor failure is also being scrutinized by the NTSB.

- We also looked at how the A-O-A could fail

and what that failure would look like.

- That analysis is coming to a very different conclusion

about the origins of the failure.

(vehicle honking)

- 44 seconds after they start to roll,

this happens.

The captain's angle of attack, airspeed,

and altitude values deviate.

- The NTSB travels to Collins Aerospace,

the manufacturer of the angle of attack sensor,

and asks their engineers to look at the fault data

for Flight 302.

- Six seconds later,

the heater on the sensor goes offline.

(beeping) - Master caution, anti-ice.

- Okay...

- These simultaneous failures all point to one thing.

- The sensor broke off, it's the only explanation.

- To determine what could have caused

the sensor to break off...

- Have a look at this.

- ...they compare the FDR data to data from a bird strike.

- They're almost identical.

(Lorenda): The U.S. investigation side

felt that the data supported more of a in-flight impact

with the angle of attack sensor.

- The hazard posed by eagles and other large birds

is well-known at Addis Ababa's airport.

- The airport in Addis Ababa had had problems with bird strikes.

The airport had several mitigation strategies in place

because of that.

(automated voice): V1.

- Rotate.

- Collins Aerospace concludes that,

as Flight 302 lifted off the ground,

a bird struck the sensor, tearing the vane from the hub.

- Gear up.

(stick whirring)

- We are having flight control problems.

- Whether the sensor failed

due to electrical failure or a bird strike,

investigators now know why Ethiopian Airlines Flight 302

crashed shortly after takeoff.

- Here's the chain of events.

The failed sensor triggers a series of warnings and alarms.

- Gear up. (stick whirring)

(alarm beeping)

- The erroneous angle of attack data

causes MCAS to activate, pitching the nose down.

(automated voice): Don't sink. Don't sink. Don't sink.

- They do what Boeing recommends

and move the trim switches to cutout.

- Stab trim cutout? Stab trim cutout?

- Yes, yes do it!

- Stab trim cutout.

- But they're unable to manually trim.

The wheel is almost impossible to move.

They never recover.

(grunting with effort)

- Not enough pitch. Not enough pitch!

- It was very obvious to them

that they no longer had control of the airplane

and that they couldn't stop this.

Recovery was impossible.

- Pitch up! Pitch!

Mayday! Mayday! Mayday!

(emotional music)

(metal clattering)

(narrator): For the NTSB,

the MAX 8 accidents provided a valuable lesson

about assumptions made by aircraft manufacturers

regarding how pilots respond to emergencies.

- I think these two accidents

are gonna be the watershed events

on how we look at the human factors

for design and certification.

- As a result of the two accidents,

Boeing overhauls the MAX 8's MCAS system.

The MCAS system now relies on information from two sensors.

It will only activate once,

and it will not override pilots' ability

to control the airplane with the control column.

Boeing also offers pilots enhanced training

on the MCAS system.

Many feel the changes Boeing made to the MAX 8 came too late.

- Ethiopian 302 should have been prevented.

Boeing should have got to the root causes of the problems

on the Lion Air flight.

Boeing didn't.

- For the devastated family of Danielle Moore,

Boeing's greater failure

was not advising pilots about the danger of MCAS.

- The bulletin from Boeing

was not good enough to prevent an accident.

The plane was still unsafe.

And it cost the life of my daughter and 157 people.

- In November 2020, after a 20-month grounding,

the MAX 8 is cleared to fly.

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Subtitling: difuze