♪
DR. LIU [English Dub]: The plane was sinking deeper and deeper.
NARRATOR: In the heart of one of Asia's busiest cities,
rescuers rush to pull air crash survivors to safety.
INVESTIGATOR 2: Nothing wrong with this actuator.
NARRATOR: Taiwan's Aviation Safety Council
confronts some urgent questions about TransAsia Flight 235.
PETER: What were the flight crew doing?
Were there engineering issues involved in this event?
How on earth did it end up in this situation?
INVESTIGATOR 1: Take a look at this.
NARRATOR: A video surfaces that makes the disaster in Taipei
notorious worldwide.
PETER: It's quite harrowing because you're seeing the
final moments of a tragic event unfolding before your eyes.
INVESTIGATOR 2: What was happening on that plane?
[♪ theme music ]
♪
NARRATOR: Taipei, capital city of Taiwan.
Near its center, amidst soaring towers, lies Songshan Airport.
The next plane scheduled for departure this morning
is TransAsia Flight 235.
The TransAsia cabin crew is waiting for a
last-minute addition to the passenger list.
FLIGHT ATTENDANT: Welcome aboard. Row 19D midway down, aisle seat.
NARRATOR: Dr. Liu Chau-Hui has made it.
DR. LIU [English Dub]: It just so happened that particular flight
had a few open seats.
I was supposed to be on the later flight,
but I decided to get on the earlier one.
DR. LIU: Yeah. Is this me?
ANNOUNCEMENT: Ladies and gentlemen, make sure your seat backs
and tray tables are in their full upright positions.
Ensure your seat belt is securely fastened.
NARRATOR: There are three highly-trained pilots in the cockpit.
The first officer is Liu Tzu-Chung.
He has almost 7,000 hours of flight time.
FO. LIU: Oil pressure.
CAPT. LIAO: Check.
NARRATOR: Captain Liao Chien-Tsung is a former military pilot.
There's also a third pilot who's an observer on today's flight.
FO. LIU: Forty-five starter off.
CAPT. LIAO: Start lights off.
NARRATOR: TransAsia 235 is a commuter flight from Taipei
to the Taiwanese island of Kinmen,
just off the coast of mainland China.
Scheduled flight time is approximately one hour.
FLIGHT ATTENDANT: Would you like a paper?
DR. LIU: Oh, thank you.
NARRATOR: Dr. Liu Chau-Hui is returning home to Kinmen,
where he runs a medical practice.
DR. LIU [English Dub]: I usually took TransAsia
because their service was quite good.
When I'd get on the plane, I'd like to grab a paper
and catch up on the day's events.
FLIGHT ATTENDANT: The cabin's ready, sir.
CAPT. LIAO: Okay. Roger, thanks.
FO. LIU: Songshan ground, TransAsia 235 request taxi.
AIR TRAFFIC CONTROLLER: TransAsia 235, runway one-zero,
taxi via whiskey.
FO. LIU: Okay. Whiskey to one-zero.
NARRATOR: The ATR 72-600 is the latest, most advanced version
of the European commuter plane.
Its Pratt & Whitney turboprop engines
are extremely powerful and fuel-efficient.
PETER: It's a very popular aircraft, particularly because
it has attractive operating economics.
It's commonly used in short-haul regional airline operations.
NARRATOR: The pilots' digital displays create
what's known as a glass cockpit.
PETER: When people refer to a glass cockpit aircraft,
they're referring to not only the displays
but what often we're talking about is
an advanced-technology aircraft
with sophisticated automation capabilities.
FO. LIU: The electronic checklists switch automatically.
Once you complete certain parts it'll switch forward.
NARRATOR: The first officer briefs his colleague
on the cockpit's technology.
Hung Ping-Chung is an experienced pilot
who's learning this computerized system.
SO. HUNG: Can you do it manually?
FO. LIU: Well, you can, but when starting the engine,
for example, it'll go to the next page
once you close the bleed valves.
♪
NARRATOR: Songshan Airport sees six million passengers a year.
For air traffic controllers, that means
handling about 100 flights a day.
AIR TRAFFIC CONTROLLER: TransAsia 235, runway one-zero,
wind one-zero-zero degree niner knots, cleared for takeoff.
FO. LIU: Okay. Cleared for takeoff.
Cabin crew, prepare for takeoff.
DR. LIU: Have a great flight.
FLIGHT ATTENDANT: Thank you. Enjoy your flight.
NARRATOR: Just before 11 in the morning, Flight 235 gets rolling.
FO. LIU: Engine instrument check normal.
CAPT. LIAO: V-1. FO. LIU: V-1.
CAPT. LIAO: Rotate.
[plane engines revving]
♪
NARRATOR: The captain engages the autopilot
and sets his desired airspeed and altitude.
PETER: As soon as the aircraft has taken off,
they're going through a series of checklist items.
CAPT. LIAO: Gear up.
FO. LIU: Gear up.
PETER: I know they've got a particular climb profile,
and they're executing the after takeoff checks
and the initial climb checks to make sure
that all the systems are performing as required.
NARRATOR: Flight 235 climbs out over Metropolitan Taipei,
a densely packed city of more than seven million people.
Seconds later... the Master Warning sounds.
PETER: The Master Warning is indicative of
an emergency situation requiring an immediate response.
NARRATOR: TransAsia 235 has lost an engine.
The captain disengages the autopilot.
CAPT. LIAO: I have control. FO. LIU: You have control.
NARRATOR: In the cabin, engine noise suddenly drops.
[emergency warning tone]
The pilots need to get their plane back on the ground.
CAPT. LIAO: Heading mode.
NARRATOR: The captain wants a heading back to the airport.
FO. LIU: We're below 2500 feet. Turn to heading... it's...
CAPT. LIAO: Come on.
FO. LIU: Zero, zero-niner-five.
CAPT. LIAO: Check.
PETER: When you lose an engine in a twin-engine aircraft,
you need to be able to maintain your climb performance
and you need to be very careful that your airspeed
does not decay or reduce too much during that climb.
FO. LIU: Okay, engine flameout check.
CAPT. LIAO: Check.
NARRATOR: Speed and climb-rate are dropping fast.
FO. LIU: Watch the speed.
AUTOMATION: Stall. Stall.
NARRATOR: The stall warning means the plane is flying
too slowly to maintain lift.
PETER: The stall warning at low altitude is
a critical situation that no pilot ever wants to end up in.
NARRATOR: Flight 235 is less than a mile from the runway.
♪
NARRATOR: Passengers can now see that they're no longer climbing.
CAPT. LIAO: Terrain ahead.
SO. HUNG: You are low!
PETER: The stick shaker is a tactile alerting system
where the control column shakes or vibrates very noticeably.
It's a very salient cue to pilots
to indicate that you must intervene
to prevent the aircraft from entering a stall.
♪
NARRATOR: The situation is critical.
PETER: It's a highly stressful event.
FO. LIU: Tower, TransAsia 2-3-5, Mayday. Mayday.
Engine flameout.
NARRATOR: Songshan controllers fear the worst,
a crash in the middle of the city.
♪
FO. LIU: Engine flameout both sides.
SO. HUNG: How is this possible?
♪
NARRATOR: Flight 235 is now only 500 feet
above the streets of Taipei.
PETER: The crew were surrounded by high-density housing,
highrise apartment blocks, a heavily populated area.
You're really between a rock and hard place.
SO. HUNG: Impact! Brace for impact!
[passengers screaming]
CAPT. LIAO: Oh no! Pull up!
AUTOMATION: Terrain. Terrain. CAPT. LIAO: Oh no!
[passengers screaming]
♪
NARRATOR: All controllers can see is that Flight 235
has dropped off the radar.
They have no idea if anyone has survived.
AIR TRAFFIC CONTROLLER: Suspend all takeoff and landing operations.
Begin emergency procedures.
NARRATOR: After hitting an elevated highway in downtown Taipei,
TransAsia Flight 235 is sinking in the Keelung River.
DR. LIU [English Dub]: I could feel something was off.
I thought to myself: Why is there water where my shoes are?
♪
NARRATOR: Those lucky enough to survive the crash
are now at risk of drowning.
DR. LIU [English Dub]: I remember very clearly, I saw a woman who
I thought was an air hostess. I told her not to be afraid.
DR. LIU: It will be okay.
NARRATOR: The water level starts to rise.
DR. LIU [English Dub]: The plane was sinking deeper and deeper.
The temperature was very cold. I couldn't hear anything.
The water had drowned out all sounds.
[helicopter propeller beating]
NARRATOR: Then, passengers are relieved to hear
a welcome sound.
[speedboat motors]
Rescuers are on the way.
First responders climb onto the fuselage
and start pulling people from the wreckage.
DR. LIU [English Dub]: I just wanted the doors to open quickly
so that I could escape.
NARRATOR: The swift current of the Keelung River means
that shocked survivors won't be safe
until rescuers can get them to the riverbank.
The city of Taipei has never seen
an aviation accident like it.
Of the 58 people on Flight 235, only 15 make it out alive.
All three pilots are dead.
♪
Investigators from Taiwan's Aviation Safety Council
are anxious to start collecting evidence at the scene.
STEVEN [English Dub]: The most important thing for us
is to retrieve the black boxes.
However, we have to wait for the search and rescue to finish
before we can go in.
NARRATOR: For now, they have to be patient.
But a stunning piece of evidence has already surfaced.
INVESTIGATOR 1: Take a look at this. It just came in.
INVESTIGATOR 2: Can you put it up here for me?
What?
What was happening on that plane? Play it again.
PETER: It was quite extraordinary that the final
sequence of events was captured by
the dash cam footage in the motor vehicle.
It's quite harrowing because you're seeing the final moments
of a tragic event unfolding before your eyes.
INVESTIGATOR 2: Freeze it. Freeze it.
STEVEN [English Dub]: We were obviously really shocked,
wondering why the plane was flying in this way.
INVESTIGATOR 1: What do you think? Left engine? Control surfaces?
THOMAS: When you watch the video clip,
you know there's something wrong about the engine.
The prop seems very slow.
INVESTIGATOR 2: You can see the propeller blades.
They couldn't have been going at full speed.
THOMAS: I thought either the aircraft lost one engine
or either the flap or the aileron jammed during takeoff.
INVESTIGATOR 2: We need to study that wreckage.
♪
NARRATOR: Salvage crews pull what remains of Flight 235
from the Keelung River.
THOMAS: We recovered everything.
I think we finished the wreckage recovery
around noon-time the second day.
NARRATOR: There's no telling which piece of wreckage
might hold an important clue.
Investigators wonder if the flight control system
shows any sign of a malfunction.
THOMAS: So we have to examine that part of the wreckage.
INVESTIGATOR 2: Nothing wrong with this actuator.
THOMAS: We cannot find anything wrong with the actuator,
the linkage of the control.
We cannot find any abnormal situation
for the flight control system.
INVESTIGATOR 1: Control system seems fine.
NARRATOR: A search for any pre-impact failures
in the plane's hydraulic system also comes up empty.
INVESTIGATOR 2: Nothing wrong with the hydraulics.
Is this the left engine?
INVESTIGATOR 1: Yes.
NARRATOR: Investigators know from the dash cam video
that the plane was banked steeply to the left.
A mechanical fault with the left engine
seems like the next most obvious suspect.
INVESTIGATOR 2: We need to take a look inside. Get the borescope.
STEVEN [English Dub]: From a borescope examination,
we can see whether or not the compressor and turbine
are damaged on the inside.
Since the turbine rotates with extremely high speed,
if it is even slightly damaged
it will be completely destroyed.
NARRATOR: But the borescope examination yields no new clues.
STEVEN [English Dub]: The examination showed that
everything was in place, and all the moving parts
were still capable of moving.
INVESTIGATOR 2: Left engine completely operational. Ah. Strange.
NARRATOR: They need to explore other possibilities.
INVESTIGATOR 2: What about the right engine?
Let's go take a look.
NARRATOR: They study the right engine,
and what they find is mystifying.
INVESTIGATOR 2: Look at the blades. They're feathered.
NARRATOR: Feathered is a propeller's failsafe position.
When a propeller engine loses power in flight,
the blades automatically rotate parallel to the air stream
to reduce drag.
PETER: What an auto-feather does,
it changes the pitch of the blades
to reduce the drag on the blades
to make sure that the airplane's flying performance
is not degraded.
NARRATOR: The discovery only deepens the mystery.
INVESTIGATOR 2: Why would the right engine be feathered
when the dash cam video clearly shows the plane
banking to the left?
INVESTIGATOR 1: It doesn't make any sense.
INVESTIGATOR 2: Let's have a look.
THOMAS: When we discovered a feather of the propeller, we
know there should be something wrong about the engine.
INVESTIGATOR 2: Anything?
INVESTIGATOR 1: Nothing at all.
STEVEN [English Dub]: Both engines yielded normal results after examination.
They were both fine.
INVESTIGATOR 1: There's nothing wrong with this engine either.
INVESTIGATOR 2: If both engines were operational,
why did this plane crash?
NARRATOR: Investigators now have two related questions to answer.
What caused the right engine's propeller to feather?
[emergency warning alarm]
CAPT. LIAO: Terrain ahead!
NARRATOR: And why did the plane bank violently to the left
just before impact?
NARRATOR: At a Songshan Airport hangar, Taiwanese investigators
still have no explanation
for the crash of TransAsia Flight 235.
Video of the turboprop's fatal plunge into the Keelung River
has spread worldwide.
But clues to what caused the crash are in short supply.
INVESTIGATOR 1: Hello? Okay. Thank you. Sir, the FDR data's in.
INVESTIGATOR 2: All right. Let's have a look.
NARRATOR: Investigators hope the plane's flight data recorder
can tell them more.
♪
The FDR records dozens of performance parameters,
including fuel flow, engine temperature and propeller speed.
FO. LIU: Okay, engine flameout check.
CAPT. LIAO: Check.
NARRATOR: Investigators already know that
the right side propeller feathered before impact.
FO. LIU: Watch the speed.
♪
INVESTIGATOR 2: Let's see the operating systems of engine two.
NARRATOR: Perhaps the flight data can tell them why.
THOMAS: When we go through the data, for engine number two
we find some parameters were normal like oil pressure,
engine temperature, fuel flow.
INVESTIGATOR 2: The engine's completely fine.
NARRATOR: But one other piece of data
seems to tell a different story.
INVESTIGATOR 2: Take a look at this.
The torque is all over the place.
THOMAS: One parameter, the torque value, fluctuated.
NARRATOR: Torque is a measure of an engine's power
to spin the propeller.
It increases and decreases during flight,
but it's not supposed to fluctuate.
INVESTIGATOR 2: Why is it doing that? Pass me the schematic.
NARRATOR: They dig deeper, studying how
the Pratt & Whitney engine measures torque.
THOMAS: So we tried to find out the design logic
for the system.
INVESTIGATOR 2: What's the connection between the torque
and the feathered propellers?
NARRATOR: They learn that the engine's auto-feathering system
includes an electronic torque sensor.
It measures how much twisting force the engine is producing.
Extremely low torque indicates that the engine has failed.
So a low reading triggers the system to feather the propeller.
But they know the engine did not fail.
There seems to be only one way
to explain the unusual torque data.
INVESTIGATOR 2: Maybe the sensor is sending a faulty reading,
triggering the auto-feathering unit.
NARRATOR: They suspect the problem was not
with the engine itself but with the sensor measuring torque.
THOMAS: We figured out that that probably will be
the signal problem between the torque sensor and the receiver.
INVESTIGATOR 2: Send the sensor to the lab so we can analyze it.
NARRATOR: If they're right about the torque sensor failing,
then they'll finally have solved
the mystery of the feathered propeller.
But investigators are no closer to understanding
another mysterious aspect of this crash.
Why did a two-engine plane
with a feathered propeller on the right side
end up banking to the left?
Searching for an answer, they return to the flight data.
INVESTIGATOR 2: What do the parameters of the left engine say?
Can you show me the fuel flow, please?
INVESTIGATOR 1: That all seems fine.
INVESTIGATOR 2: The propeller speed.
NARRATOR: According to the data, the left engine
was in perfect working order.
STEVEN [English Dub]: Engine number one's performance was always good.
All its statistics were normal.
INVESTIGATOR 2: The power lever angle.
NARRATOR: But when they check the throttle settings,
they make a stunning discovery.
INVESTIGATOR 2: Unbelievable.
THOMAS: When we go through the FDR data, we find that the
power of the number one engine was gradually being reduced,
reduced and eventually being shut off.
INVESTIGATOR 2: The left engine was manually shut down.
NARRATOR: Investigators know the ATR 72
is not equipped with an auto-throttle system.
The throttles can only be moved by hand.
INVESTIGATOR 2: It had to have been shut down by one of the pilots.
THOMAS: So we start to wondering why the pilot
would shut down the good engine.
STEVEN [English Dub]: Honestly, at the beginning,
we did not understand how this could happen.
INVESTIGATOR 1: That's crazy.
♪
INVESTIGATOR 1: Let's take a look at the circuit board.
NARRATOR: Investigators examine the torque sensor
from the right engine of TransAsia Flight 235.
They're looking for any defect that could have caused
the propeller to feather in flight.
STEVEN [English Dub]: The lab used precise testing methods.
They made a cross-section of the circuit board
and looked at its image.
♪
INVESTIGATOR 1: Take a look at this. It's a broken solder.
NARRATOR: They discover microscopic faults in the circuit board.
PETER: And that was related to the soldering joints
in a particular circuit board being compromised
for reasons that were difficult to establish.
It was possibly related to some form of manufacturing defect
or something of that nature.
THOMAS: And that would be enough to stop
the transmission of the signal.
NARRATOR: With a broken circuit board,
the torque sensor couldn't do its job.
Even though the engine was turning,
the sensor couldn't detect any torque.
So the system automatically feathered the propeller.
PETER: The brain of the system thought that torque
had reduced below a pre-determined value,
which I think is about 18%,
and that is what triggered the auto-feather.
FO. LIU: Okay, engine flameout check.
CAPT. LIAO: Check.
NARRATOR: Finally, they understand
why the right side propeller feathered.
But they still haven't explained the crash.
The ATR 72 has two engines.
Losing propeller thrust in one of them
should not have been a catastrophic event.
THOMAS: They are designed to fly only with one engine.
CAPT. LIAO: Terrain ahead.
AUTOMATION: Terrain. Terrain. Pull up.
PETER: Pilots train for engine out operations regularly.
Typically, it's bread and butter for an airline pilot
to deal with an engine failure on a multi-engine aircraft.
NARRATOR: To figure out why 43 people died,
investigators must now answer a much more difficult question.
THOMAS: We still have number one engine produce power normally,
but for some reason the pilot decided
to shut down the good engine.
FO. LIU: Watch the speed.
THOMAS: We had to find out why.
NARRATOR: Investigators turn to the cockpit voice recording.
INVESTIGATOR 1: Okay. Ready? Let's hear what we got.
FO. LIU: Oil pressure?
CAPT. LIAO: Check.
THOMAS: The accident flight is very short,
less than three minutes.
So we listened to the CVR starting from
the takeoff roll to the end of the flight.
FO. LIU: Before taxi Checklist. Propeller brake?
CAPT. LIAO: Off.
FO. LIU: Nose wheel steering?
CAPT. LIAO: On.
FO. LIU: Procedure complete.
INVESTIGATOR 1: Checklist complete.
So far they're following procedure to a T.
THOMAS: You have to make your procedure very clear.
INVESTIGATOR 2: Let's see what happens closer to takeoff.
FO. LIU: Engine instrument check normal.
CAPT. LIAO: V-1. FO. LIU: V-1.
CAPT. LIAO: Rotate.
AIR TRAFFIC CONTROLLER: TransAsia 235, contact approach
on one-one-niner-decimal seven. Good day.
INVESTIGATOR 2: What's that sound?
INVESTIGATOR 1: It must be the engine two fault warning.
PETER: When the Master Warning first activated,
they were approximately about 1200 feet above ground level.
INVESTIGATOR 2: They're flying an ATR 72/600.
It shouldn't be a huge problem.
THOMAS: If they followed procedure, do everything correctly,
they should be able to fly back to land without any problem.
INVESTIGATOR 1: This is a crucial moment.
Let's hear what they're gonna do next.
CAPT. LIAO: I have control.
NARRATOR: Investigators hear the sound of the autopilot turning off.
INVESTIGATOR 1: He's disengaging the autopilot.
He shouldn't be doing that.
PETER: It's hard to understand why the pilot flying
disconnected the autopilot during an emergency situation.
He just made a difficult situation worse.
INVESTIGATOR 2: Keep playing.
[emergency warning alarm]
FO. LIU: Okay, engine flameout check.
CAPT. LIAO: Check.
PETER: Their attention will be directed to
the engine warning display, which in the ATR 72
clearly indicates which engine has failed.
THOMAS: There's a checklist procedure on the screen.
You follow it step by step.
NARRATOR: But instead of following the emergency checklist...
FO. LIU: Watch the speed.
NARRATOR: ... the captain does something inexplicable.
CAPT. LIAO: Pull back number one.
INVESTIGATOR 2: The captain is starting to shut down engine one
without fully understanding
what the computer system is telling him.
NARRATOR: Both engines are capable of producing power.
But because the right engine has feathered, it has lost thrust,
behaving like a car in neutral.
When the captain pulls back the left throttle,
he leaves himself with no thrust from either engine.
PETER: He didn't seem to fully appreciate
that that had ultimately resulted
in number one engine being shut down.
INVESTIGATOR 2: How could he do such a thing?
NARRATOR: Investigators have discovered
from the cockpit voice recorder
that the captain of Flight 235
shut down the plane's only working engine.
INVESTIGATOR 2: Why didn't the first officer stop him?
NARRATOR: They continue listening to the recording,
trying to understand why the captain's mistake
wasn't corrected in time.
CAPT. LIAO: I will pull back on engine one throttle.
INVESTIGATOR 2: He can't just say he's gonna shut down the engine.
NARRATOR: Pilots are supposed to run a cross-check,
where one pilot verifies the actions of the other.
PETER: When the pilot flying shut down the operative engine,
he did so very quickly
without discussing it with the pilot monitoring.
INVESTIGATOR 1: He's acting before even
confirming what the emergency is.
THOMAS: When there is a warning come up,
the procedure says you identify the problem before you act.
FO. LIU: No, wait a second. Cross-check.
PETER: The pilot monitoring, to his credit,
did try to stop the pilot flying
from manipulating the engine number one power lever,
and he announced he wanted a cross-check.
But there was no definitive confirmation from
the pilot flying that the problem was engine number two.
CAPT. LIAO: Heading mode.
NARRATOR: Instead, the captain interrupts the first officer
to ask for a new heading.
FO. LIU: We're below 2500 feet.
CAPT. LIAO: Come on!
FO. LIU: Zero. Zero-niner-five.
CAPT. LIAO: Check.
INVESTIGATOR 2: The first officer did tell the captain to wait.
He knows that the captain
was pulling back on the wrong engine,
and when he did try to question it
the captain just confirmed what he was doing.
PETER: All of a sudden they've got a dual engine failure,
and the pilot monitoring I think has been caught off guard,
and he's not really sure what's gone on.
[emergency warning alarm]
CAPT. LIAO: Restart the engine.
FO. LIU: I can't restart the engine!
CAPT. LIAO: Oh, wow. I shut off the wrong engine.
PETER: The pilot flying clearly has an epiphany
that they're in very dire trouble.
CAPT. LIAO: Restart the engine.
FO. LIU: I can't restart the engine!
CAPT. LIAO: I shut off the wrong engine.
STEVEN [English Dub]: It's very sad.
When I heard him say, "I shut off the wrong engine,"
I was completely devastated.
NARRATOR: By the time the captain realizes his mistake,
it's too late.
SO. HUNG: Impact! Brace for impact!
FO. LIU: Pull up! CAPT. LIAO: Noooo!
PETER: Unfortunately, neither crew member
actually followed the standard set of procedures
for dealing with an engine flameout after takeoff.
NARRATOR: Investigators now have
an even more puzzling question to answer.
INVESTIGATOR 2: Why didn't the captain understand what he was doing?
NARRATOR: The captain's failure to recognize the situation
and react properly ended up costing 43 lives.
He thought that the left engine had failed
when the aircraft was clearly telling him it was
the right engine that had a problem.
How could the captain have gotten things so wrong?
INVESTIGATOR 2: What was this captain's background?
NARRATOR: When they dig into the captain's history,
they make a disturbing discovery.
INVESTIGATOR 1: The captain failed one of his key training components.
PETER: The pilot flying's training records had indicated
that he was prone to being a bit anxious.
CAPT. LIAO: I have control.
FO. LIU: You have control.
PETER: Feeling a little bit overwhelmed in emergency situations
and had a tendency to prematurely respond
or act in that situation.
CAPT. LIAO: Pull back number one.
♪
INVESTIGATOR 1: He was also fired from his last job.
NARRATOR: Although the captain was an accomplished military pilot,
his civilian record is raising questions.
INVESTIGATOR 2: Maybe he wasn't used to the ATR 72/600.
NARRATOR: The records soon confirm that hunch.
Liao Chien-Tsung had logged relatively few hours
in TransAsia's newest commuter plane.
PETER: The captain in the left-hand seat had
approximately 5,000 hours total time,
and he had about 250 hours on the ATR 72/600.
FO. LIU: Wait a second. Throttle!
CAPT. LIAO: Number one feather shut-off.
NARRATOR: The ATR 72-600 is known for its advanced technology.
Investigators now wonder if this aircraft,
with its computerized glass cockpit, was too complicated
for a relatively inexperienced pilot to manage in a crisis.
CAPT. LIAO: Restart the engine.
FO. LIU: I can't restart the engine!
PETER: They can often be overwhelmed
with the huge volume of information.
They also have to consider the nature of the automation
and the modes that are presented to them.
So it's more challenging.
CAPT. LIAO: I shut off the wrong engine.
NARRATOR: Did information overload lead to the deaths
of 43 people in one of Taiwan's worst air disasters?
NARRATOR: Investigators need to know if the advanced technology
designed to help pilots in the ATR 72/600
may instead have contributed to the crash of Flight 235
by confusing the TransAsia captain.
INVESTIGATOR 2: Okay. Ready to fly out of Taipei?
INVESTIGATOR 1: Let's do it.
NARRATOR: To try to find out, they program a flight simulator
using the flight data from the downed plane.
THOMAS: We have weather information. We have FDR data.
We have CVR data. So we put those together
to duplicate the condition of the accident.
NARRATOR: The data lets investigators fly the exact same flight:
the same speeds, same climb rate,
and, 37 seconds into the flight, the same cockpit alarm.
INVESTIGATOR 1: That's the warning. Engine two flameout.
NARRATOR: The plane's computer instantly identifies
which engine has lost thrust.
INVESTIGATOR 2: Check autopilot armed. Run the checklist.
NARRATOR: The automated checklist pops up.
Clear, concise and easy to follow.
INVESTIGATOR 1: Up trim on engine one.
Auto feather on number two.
INVESTIGATOR 2: Check.
INVESTIGATOR 1: Engine two flameout confirmed.
INVESTIGATOR 2: Confirm. Secure engine number two.
NARRATOR: The checklist calls for the pilot monitoring
to reduce power in the feathered engine to idle.
The other pilot guards the working engine.
PETER: Then you would bring a condition lever
into the fuel shut-off détente,
which removes fuel from the engine.
INVESTIGATOR 1: Condition lever to fuel shut-off.
INVESTIGATOR 2: Check.
PETER: And then the engine will be secured and shut down.
INVESTIGATOR 2: Engine number two secured.
NARRATOR: Now powered by just one engine,
the plane keeps climbing safely on autopilot.
The computerized systems have helped
the pilots avoid disaster, exactly as designed.
PETER: It's quite manageable. The crew can continue the flight,
climb to a safe altitude, reconsider their options.
INVESTIGATOR 2: Now we just have to fly
back to the airport and land. I have an idea.
Let's see what happens if we just let the plane fly itself.
Reset from the start.
INVESTIGATOR 1: Resetting.
THOMAS: When we do the simulator test, we try to find out
what will happen if the pilots do nothing.
NARRATOR: Incredibly, the simulation shows that
even if there had been no pilot input at all,
the plane would not have crashed.
THOMAS: The aircraft will continue climb
and then fly with no problem.
So I think the aircraft was designed to handle
that situation, as long as we don't do anything wrong.
NARRATOR: Any doubts about the glass cockpit have now been erased.
The advanced systems of the ATR 72-600
did not lead to the crash of Flight 235.
There must have been some other factor.
Investigators study reports from previous incidents
where similar mistakes were made.
They suggest an intriguing possibility.
INVESTIGATOR 2: Interruptions and multi-tasking.
NARRATOR: Investigators know the captain's workload was high.
Taking manual control of the plane distracted him
from running a cross-check with his first officer.
INVESTIGATOR 2: He's multi-tasking.
[emergency warning alarm]
FO. LIU: Watch the speed!
INVESTIGATOR 2: He could have been suffering from change blindness.
PETER: Change blindness, people are focused or fixated on
another item or area of interest,
and so they miss what would be considered
a very distinguishable change in the environment,
but they don't perceive it.
CAPT. LIAO: I will pull back engine one throttle.
INVESTIGATOR 2: Even when all the systems were telling him
it was engine two, his perception told him
he was doing the right thing. Change blindness.
NARRATOR: The first officer even tried to warn him.
FO. LIU: No, wait a second. Cross-check.
NARRATOR: It seems the captain was blind to the clear warning
that his right engine had feathered.
Investigators finally understand
what went wrong aboard TransAsia Flight 235.
A microscopic crack in a circuit board
disabled an engine sensor
that led the system to wrongly determine
that the right engine had failed.
But that in itself wouldn't have caused the plane to crash.
INVESTIGATOR 2: This was a series of mistakes on the part of the captain.
When engine two feathered, the captain reacted
before he had properly assessed the situation.
NARRATOR: The captain should have followed a checklist.
CAPT. LIAO: I have control.
NARRATOR: Instead, he turned off the autopilot
and reduced power in the wrong engine.
CAPT. LIAO: I will pull back engine one throttle.
INVESTIGATOR 2: All we know for sure is he shut down
their only working engine.
By the time he realizes, it's too late.
CAPT. LIAO: Restart the engine.
FO. LIU: I can't restart the engine!
CAPT. LIAO: Wow. I shut off the wrong engine.
♪
INVESTIGATOR 2: Why did TransAsia hire this pilot?
NARRATOR: Investigators dig into
TransAsia's corporate background...
INVESTIGATOR 1: Check this out.
NARRATOR: ... trying to understand how a pilot
with such a poor record ever got through the door.
INVESTIGATOR 1: And this.
INVESTIGATOR 2: This company's been expanding rapidly.
NARRATOR: What they find paints a picture
of a growing company struggling to compete
with bigger players in the competitive Asian market.
PETER: A more regional operator like TransAsia Airways
appears to have struggled to certainly
recruit and retain the sort of expertise that airlines seek.
NARRATOR: The crash of Flight 235 would be
the last accident for TransAsia Airlines.
In November 2016, the company ceased operations
and went out of business.
PETER: There's a multitude of reasons that the board
decided to shut down the airline.
But there's an inescapable conclusion that
the adverse or poor safety performance of the airline
certainly had an economic impact on the airline.
NARRATOR: Even though TransAsia Airlines no longer flies,
air crash investigators hope that the tragedy of Flight 235
will serve as an important safety reminder
to pilots at other airlines around the world.
THOMAS: We all understand that pilots, they're human.
Humans make mistakes.
So that's why we design the standard operating procedures.
And the basic important thing is for people
just follow the procedure.