16-08. River Runway

babycarseattips

5/31/2025

Transcript

00:01Violent turbulence rocks Garuda Flight 421.

00:05Where did this come from? Strap in.

00:09The shaking was so violent, I almost lost control of the plane.

00:15Terrified passengers just want the nightmare to end.

00:19I was scared. Extremely scared.

00:22Instead, the white-knuckle ride gets much worse.

00:27Engine 1, flamed out!

00:30Engine 2, flamed out!

00:33You're in extreme dire circumstances when you have a dual-engine flame out.

00:37The 56-ton jet is falling from the sky.

00:41Please forgive our sins.

00:42Let us have the strength to save our passengers.

00:45I felt that death was really upon us.

00:48We were about to face our fate.

00:52And so, we prayed.

01:00A Boeing 737 cruises high above the islands of Indonesia.

01:01A Boeing 737 cruises high above the islands of Indonesia.

01:14The crew of Garuda Indonesia 421 is about halfway through a short domestic flight.

01:32We were at 28,000 feet on the way to Adi Sucipto Airport in New Jakarta.

01:40Captain Abdul Rozak is a senior pilot with Indonesia's National Airline.

01:46How does the weather look in Yogyakarta?

01:50His first officer is Harry Gunawan.

01:54Should be fine, but there might be a bit of rain.

01:58I had flown several times with Harry Gunawan, so it was nothing new.

02:03We knew each other quite well.

02:12Today, the cabin crew is responsible for 54 passengers.

02:19Madam, can I offer you a drink?

02:20Yes, I'll have tea, please.

02:22Tuhu Wasano has been a Garuda flight attendant for 16 years.

02:26Everything was normal.

02:27We offered food and drinks for the passengers.

02:28We checked the cabin, and we chatted.

02:29Suci Suhayanti is a senior government official, on her way to an important meeting.

02:47Because of work, I fly often, and I have done so since the 70s.

02:53I really love flying.

02:57The flight is a 60-minute trip from Mataram, on the resort island of Lombok, to Yogyakarta, on the main island of Java.

03:07January is the rainy season, when the weather is unpredictable.

03:11Let's avoid that sound.

03:13Say, heading 300.

03:16Patrol, Garuda 421, request heading 300 to avoid some weather up ahead.

03:23Garuda 421 confirmed, heading 300.

03:27Fly direct to Bravo Alpha NDB after clearing weather.

03:31Air traffic control authorizes a slight course correction to steer the plane around some looming clouds.

03:40The weather was just like any other afternoon.

03:43There was no turbulence.

03:45We could see from the cabin that it was bright outside.

03:47It was very normal.

03:51But soon, more large storm clouds appear in their path.

03:57What do you think?

03:59I could see the green, yellow, and red on the radar.

04:04And I knew that the safest route would be towards the green.

04:07I think we just veer a little to the left into that green gap.

04:13Should be fine.

04:15The weather ahead could make for a bumpy ride.

04:20Prepare the cabin for a little turbulence.

04:21Hopefully it won't be too rough.

04:22Yes, cabs.

04:23As a precaution, the passengers are advised to fasten their seatbelts.

04:24I never thought it was something unusual.

04:25I've been asked to put my seatbelt on many times before.

04:26I dont know if there is a seatbelts were at the roof.

04:27I thought it was a little bit dark.

04:28I had not seen that the seatbelts were at the top or under.

04:29It wasn't even that a seatbelts that I had to pass the seatbelt.

04:35I think we're just fine.

04:36I thought it was just that it appeared.

04:38I never thought it was something unusual.

04:40I have been asked to put my seatbelt on many times before.

04:46Those are at the top of the seatbelts, you cannot put it on.

04:49The seatbelts…

04:51BRUTA 421, request clear instant descent flight level 1916.

04:54Request the rest to descend to flight level 190.

04:57Garuda 421, you are cleared to 190.

05:00The Garuda flight is now set to begin its approach,

05:03so controllers clear them to descend.

05:09But moments later, the weather is suddenly much worse.

05:18Where did this come from?

05:21Well, we're in it now.

05:23Stop it!

05:28I had directed the plane towards the green.

05:32But as soon as I entered the cloud, everything went red.

05:40This was a massive supercell.

05:43It encompassed a large amount of area

05:47that the pilots were forced to navigate in.

05:50I was extremely surprised.

05:55We'd already entered the cloud,

05:57so like it or not, we had to go through the storm.

06:00The sudden turbulence is far worse than anyone in the cabin was expecting.

06:09We started to feel the plane shaking violently,

06:18and some people started to scream.

06:19The turbulence made walking impossible.

06:27The trays were flying around.

06:29I was afraid I'd fall on someone.

06:34I was afraid I'd fall on someone.

06:36The shaking was so violent, I almost lost control of the plane.

06:49The engines!

06:50The captain spots a serious problem.

06:51Yes, sir.

06:52Want to do a drop?

06:53Yes, sir.

06:54Want to do a drop?

06:55They're suddenly losing engine power.

06:56Increasing thrust?

06:57Nothing.

06:58Keep your eyes on them, sir.

07:00Moments later, the crisis gets even worse.

07:01Engine one flame down.

07:02Confirmed.

07:03And engine two flame down.

07:04And engine two flame down.

07:05Both engines have flamed out.

07:06The combustion process is almost all over.

07:09It's almost all over.

07:10They're all over.

07:11They're suddenly losing engine power.

07:12They're suddenly losing engine power.

07:13Increasing thrust.

07:14Nothing.

07:15Keep your eyes on them, sir.

07:16Moments later, the crisis gets even worse.

07:17Engine one flame down.

07:18Confirmed.

07:20Engine one flame down.

07:21And engine two flame down.

07:22Engine two flame down.

07:26Both engines have flamed out.

07:31flamed out, the combustion process extinguished.

07:35You're in extreme, dire circumstances

07:37when you have a dual-engine flame out.

07:40The plane now has no thrust at all.

07:45Inside, they've lost primary electricity.

07:48All systems switch to backup power.

07:52All of a sudden, the emergency lights came on.

07:55I was shocked to see that.

07:56Captain Rozak struggles to keep the plane steady

08:03as the altitude starts to drop.

08:06I immediately yelled for the emergency checklist.

08:09Emergency checklist.

08:10Perform engine flame out procedure.

08:13Engine start switches to flight.

08:15Engine start switches to flight.

08:16Start levers to cut off.

08:17Start levers to cut off.

08:18You take both start levers for both the number one

08:20and the number two engine and put them back in the run

08:23position, and then you wait to see if the engines light off.

08:28Time, 30 seconds.

08:33The restart procedure demands patience.

08:36We timed it for 30 seconds, as is the protocol,

08:41and waited for them to light up.

08:43After the timing, 30 seconds, it doesn't light up.

08:49Oh, it's good.

08:51I thought I probably wouldn't see my husband or children again.

09:00I was praying for God to help me because I wasn't ready to die.

09:09By now, the engines should have restarted.

09:12Relay filled.

09:13But both of them are still dead.

09:15Try it again.

09:16OK, let's go.

09:19Engine start switches to flight.

09:21Engine start switches to flight.

09:23The plane is now dropping 1,000 feet every 15 seconds.

09:27That's an extreme emergency.

09:29Time, 30 seconds.

09:32You have very little options, and immediate action is required.

09:36For the second time, the Garuda pilots try and fail to restart their crippled engines.

09:52Now, only minutes from hitting the ground, they're running out of options.

09:57After the engines wouldn't start a second time, I knew we still had our auxiliary power unit, the APU.

10:09The APU is a jet fuel powered generator that provides electrical power for the aircraft.

10:16The APU may be their only hope.

10:20Start APU.

10:21Start APU.

10:22Start APU.

10:23But as they try to start it...

10:25We've lost all power.

10:30...catastrophe strikes.

10:32When he tried to turn on the standby generator, everything shut down.

10:37OK, figure it out.

10:43Electricity was gone.

10:45Flight instruments, gone.

10:47Everything went dark.

10:49I had no tools to fly the plane.

10:55Controllers are stunned to see Flight 421 vanish from radar.

11:00Garuda, 421, do you read me?

11:03421, please report your position.

11:10Mayday, mayday, mayday.

11:12Garuda, 421, mayday.

11:16We were still within the severe turbulence.

11:18We had tried everything in the book.

11:20So my co-pilot grabbed the mic and yelled,

11:22Mayday, mayday, mayday.

11:24Mayday, mayday, mayday.

11:25Garuda, 421, mayday.

11:28But controllers can't hear the desperate call.

11:30Garuda, 421, do you read me?

11:33Please report your position.

11:38Mayday, mayday, mayday.

11:41They've lost all contact with the stricken plane.

11:44I heard, mayday, mayday.

11:47Then I overheard they were saying, no power, no power.

11:50No power, no radio.

11:55That's when I realized the plane had no working engine.

11:58Everything was off.

11:59No power, no radio.

12:03What do we have?

12:04We're just instruments only.

12:05They would have the standby attitude indicator or horizon,

12:09standby airspeed indicator, and a magnetic compass.

12:14We're in God's hands now.

12:21The pilots pray for help.

12:23Please forgive our sins and let us have the strength to save our passengers.

12:28I felt that death was really upon us.

12:34We were about to face our fate, and so we prayed.

12:39I was scared, extremely scared.

12:50I said some prayers.

12:51I asked God to help us.

12:52I prayed my last rites and begged for God's forgiveness.

12:56I kept praying and praying.

12:58That's all I could do.

13:05The 56-ton jet with no power is falling fast.

13:10But the pilots aren't giving up.

13:13Let's see if we can find ourselves in the airport.

13:15The airplane would be gliding.

13:16It would be losing altitude, but the airplane continues to fly,

13:20whether the engines are running or not.

13:22Confirm our optimal speed for drift down.

13:24Yes, sir.

13:27I actually couldn't see the standby instruments.

13:30They were so small, so I had to rely on my co-pilot.

13:36Drift down airspeed.

13:37Two, one, two knots.

13:39Two, one, two.

13:40Current speed, please.

13:42Two, three, five.

13:44You need to lose speed.

13:48It would be very challenging to try to land a 737 without power

13:54and without any type of assistance.

14:01At roughly 8,000 feet, Garuda Flight 421 finally escapes the storm.

14:08Okay, let's figure out where we are.

14:14But the captain's task still seems impossible.

14:19Landing a plane with no engines and no electronic guidance.

14:25I didn't even know where we were because my instruments were dead.

14:29We're near the solo river, sir.

14:35Where's the airport?

14:37Quickly.

14:38We're past it, sir.

14:40The nearest airport is now behind them and they're too low to circle back.

14:44They've missed their last chance for a controlled landing.

14:48We have to land somewhere.

14:50Let's see what we've got.

14:55The plane weighs 56 tons.

14:58You can imagine how fast we were descending.

15:02We had to decide in seconds where we could land the plane.

15:05Dropping lower and lower, the crew of Garuda 421 scrambles to find somewhere to land.

15:22Negative, too risky.

15:24Landing in the rice paddy could have cartwheeled the airplane.

15:28It could have made the airplane break in several pieces as well.

15:33With his plane falling fast and no other option in sight,

15:36Captain Rozak decides to do something few pilots have ever tried.

15:41Okay, the river then. It's our best chance.

15:44Yes, sir. Tell me what to do.

15:47No gear, no flaps. Watch my speed.

15:51The solo river is narrow and twisting.

15:53Ditching a 737 on it won't be easy.

15:55But I believe the plane would suffer less from the impact.

16:04And we'd have a better chance of surviving.

16:09But there's another obstacle.

16:11Bridge!

16:14Can we go under it, sir?

16:14No.

16:19I wanted to pass under the bridge,

16:20but I could make out that there were concrete pillars underneath it.

16:24Yeah.

16:263,000 feet!

16:28Captain Rozak makes a split-second decision.

16:31Let's circle around and put it down over there.

16:34Turn with me!

16:36Turning!

16:38Looping back could give them a longer stretch of river to land on.

16:42But they're running out of time.

16:43In order to turn, the aircraft relies on its hydraulic system.

16:49And the hydraulics need engine power.

16:52A large amount of force is required without hydraulics.

16:56It would be the equivalent of trying to drive your car without power steering assistance.

17:01Bank angle, sir!

17:03Look! I see, I see, I see!

17:06Keep turning, but we don't make the river!

17:08Turn hard!

17:09My co-pilot shouted out because he felt the turn was too sharp.

17:20But I told him we have no choice.

17:22If we don't do this, we will not make it to the river.

17:30For the first time, I saw a river, a bridge, and rice fields.

17:34But I was confused. There was no runway.

17:39I was confused.

17:45Speed!

17:47One time and zero, sir.

17:49That'll do.

17:49As they line up with the river, First Officer Gunawan notices another problem.

17:54There's another bridge!

17:56Altitude, 250!

18:00Bridge can't be more than 80 feet. We're good.

18:03It turns out I had to land the plane between two bridges.

18:06150!

18:07Warn the cabin! Brace for landing!

18:10Brace for landing! Brace for landing!

18:14Brace for landing! Everyone, brace for landing!

18:20Okay, okay, okay! Here we go!

18:2550!

18:2640!

18:28Help us, God!

18:2930!

18:3030!

18:3130!

18:35Face!

18:38From the beginning, I had left it all to God.

18:42I had no more fear.

18:44I had hopes that I could survive this, and that the passengers would be saved too.

18:48I had no more fear.

18:58Flight 421 hits the water at almost 200 miles an hour.

19:02The cabin of Flight 421 has been demolished.

19:17You okay?

19:18The cabin of flight 421 has been demolished.

19:33When the plane finally stopped after the emergency landing, I was very relieved and grateful.

19:39I wondered if there was blood on my feet.

19:50It turned out it was just water. I said, thank God I survived.

20:02I began the evacuation process. I helped the passengers who were near me at the front of the plane.

20:09Thank you, God.

20:18Let's check on the passengers.

20:24From the emergency exit, the station is the only one.

20:30Thank you, God.

20:33Let's check on the passengers.

20:36From the emergency exit, passengers can wade safely to shore.

20:42I was the last person to leave the plane.

20:47Of the 60 passengers and crew on board, all but one make it out alive.

20:54I'm very surprised there was only one fatality.

20:58It's a sheer miracle that more people did not perish in the accident.

21:04Despite the skillful landing, the sight of a 737 ditched in an Indonesian river is disturbing.

21:08As crews remove wreckage from the Solo River, the nation looks for answers.

21:24How could a state-of-the-art airplane simply shut down in mid-air?

21:29The job of figuring out what brought down Garuda Flight 421 falls to a team of Indonesian investigators.

21:46Their first priority is to recover the plane's black boxes.

21:52It will reveal all the information we need.

21:55All of the engine behavior, all of the pilot communications.

22:00So we really, really need this black box.

22:03While they wait for word on the flight recorders, investigators speak to Captain Rozak.

22:10Thank you for coming, Captain.

22:12They want to learn more about the pilot behind this landing.

22:17He has 14,000 hours of flying time.

22:20But getting here was not easy.

22:22Growing up poor, he sold vegetables in the streets of Jakarta.

22:27His family unable to afford school.

22:29My only chance for an education was to win a scholarship.

22:34There were thousands of people who applied to the National Flight School.

22:39And I was lucky enough to be one of the 56 students who graduated in my year.

22:44Captain Rozak quickly rose through the ranks at Garuda.

22:51I was extremely happy to join the biggest airline in Indonesia.

22:57It was a dream come true.

23:01So, can you tell me exactly what happened?

23:07I've never experienced an engine flameout before.

23:12I thought these engines could handle anything.

23:16My first big question is what caused the engines to flame out simultaneously.

23:22Why couldn't you relight them? We tried.

23:24Maybe they had a fault.

23:28Didn't make sense.

23:31The downed Boeing plane was equipped with two CFM-56 engines, one of the most advanced turbofan designs in the world.

23:42The power plant draws in cold air with a large fan at the inlet.

23:51A series of blades then compress some of the air before it's mixed with fuel and ignited in the burner.

23:58Combustion spins turbines in the core that drive the engine and push hot exhaust gases out of the rear nozzle at high speed.

24:05So, there's probably 4,000 to 6,000 CFM-56 in use at the moment.

24:10It's a very reliable engine and has a very good history.

24:15Let's take a look at the occurrence manual.

24:16Let's take a look at the occurrence manual.

24:26But as investigators learn, even the best engine isn't foolproof.

24:30There were some cases with similar aircraft where the engine flamed out.

24:41In 1988, TACA flight 110 got caught in a violent thunderstorm flying from Belize to New Orleans.

24:49Both engines on the brand new 737 flamed out.

24:52The pilot managed to make an emergency landing on a grass-covered levee.

25:01Investigators discover that in response to the near disaster with the TACA flight, the manufacturer redesigned the engine.

25:09A new design changed the shape of the spinner and increased the distance between the fan motor and the splitter to better deflect moisture from the core.

25:18They found that the dome shape worked better for both ice and hail.

25:24So, why did this redesigned engine now fail?

25:28See, it doesn't make any sense.

25:30I was surprised that the dual engine flame out occurred to the engine that has been modified for a precipitation.

25:40Engineers run a series of tests on the two engines.

25:43They're looking for any defect that might explain the mid-air failure.

25:54They find nothing. No mechanical faults of any kind.

25:59Everything seems to be good.

26:01My opinion was that the engine, including the modification, was working as it designed.

26:07So, my question was what caused the engine's flame out.

26:14At the crash site, a new development brings hope of finding some answers.

26:19Divers have recovered the aircraft's flight data recorder.

26:23Let's take a look at this.

26:29Investigators focus on the engine performance numbers.

26:33Now, check out the fuel flow, right here.

26:35The data shows that when the plane entered the storm, fuel consumption shot up.

26:41But despite the higher fuel flow, engine speed remained constant.

26:49And yet, the engine rotation remains the same and does not increase.

26:54It tells investigators that the engines were working hard, battling against the heavy rainstorm.

26:59Fuel flow would go up because of the ingested water, because it increased air density.

27:06And then suddenly, the engines died. What changed?

27:10The plane's engines were specifically designed to handle large volumes of water.

27:15Investigators see nothing in the data to explain why they suddenly cut out.

27:19What went wrong is still a mystery.

27:27But just as one lead fails to pan out, another turns up.

27:32Searchers pull the cockpit voice recorder from the mud of the Solo River.

27:40So, let's hear what was happening inside the cockpit.

27:46You plug in?

27:48Go ahead.

27:50Let's avoid that sound.

27:52At the start of the recording, the audio quality is good.

27:56Garuda 421, request heading 300.

27:59Yes, sir. One and two and one.

28:01Whoa.

28:03But soon, noise from the pounding storm makes it almost impossible to decipher sounds in the cockpit.

28:13Can you isolate the voices?

28:15Investigators can no longer make out what the pilots are saying.

28:19They were unable to filter the exterior noise out to listen to the conversation of the pilots because it was that severe.

28:27It was super, super loud.

28:30When we listen to the CVR, it's really hard to understand.

28:39Stop.

28:40Rewind.

28:41Try again.

28:46Then, in the last seconds of the recording, a non-human voice can be heard.

28:54Rewind.

28:56Rewind.

28:58Rewind.

28:59It's saying terrain.

29:01Rewind.

29:03Rewind.

29:04It's a ground proximity warning.

29:06Rewind.

29:08Rewind.

29:09Rewind.

29:10Rewind.

29:11Investigators have stumbled across a huge clue.

29:16Rewind.

29:17Rewind.

29:18Rewind.

29:19Rewind.

29:20Rewind.

29:21Rewind.

29:22Rewind.

29:23Rewind.

29:24At 18,000 feet, the on-board computer detected something solid below the plane.

29:32Something as solid as terrain.

29:34When I heard terrain, terrain, I was surprised.

29:37First, there was no terrain in the area.

29:41There's no amount of rain in the world that can trigger that warning.

29:46What was happening?

29:47Indonesian investigators struggled to understand why a terrain warning sounded aboard Garuda 421 when the aircraft was still at 18,000 feet.

30:03Amid the wreckage, the plane's nose cone, or radome, provides a critical clue.

30:08Come see this for a sec.

30:10It was beat up pretty bad.

30:12It almost looked like someone had gone out with a ball-peen hammer and took aggression out on the radome of the aircraft.

30:19Look at these.

30:20I'd never seen this before.

30:23There's only one thing this could be.

30:27Hail.

30:30It's now clear that the violent storm the crew encountered contained enough hail to damage the nose and to trigger the ground proximity warning.

30:39The hail was estimated to be the size of tennis balls, which is enormous and detrimental to the aircraft.

30:52Part of the engine's recent modifications had specifically to do with hail.

30:57The engine is designed to handle 10 grams per meter cubed, a fairly large amount of precipitation.

31:05Investigators wonder, did the massive storm throw more rain and hail than that at Flight 421's engines?

31:15They take the sound of the rain and hail hitting the Garuda cockpit at the moment the engines flamed out,

31:22and compare it with cockpit recordings of other flights hit by severe storms.

31:27The comparison shows that the Garuda flight flew into precipitation heavier than any storm ever recorded.

31:40The loudness of the storm, along with the engine's performance data,

31:44tells investigators how much rain and hail the 737 likely encountered.

31:48That's insane.

31:50And based on our tests, we conclude that the amount of ice was more than 18 grams per cubic meters.

31:59These engines were well in excess of the manufacturer's tested criteria.

32:06It was almost double the amount of precipitation, water and hail ingested into the engine.

32:11Investigators have compiled convincing data on what caused the dual-engine flameout.

32:16But to be absolutely sure, they want to put their analysis to the test.

32:23Engines power on.

32:29Okay, let's add some water and ice.

32:33The NTSC wanted to determine how much water was actually ingested and if the engine would continue running.

32:38So they went and sprayed to the inlet of the engine.

32:43The manufacturer's recommended to mount and the engine ran perfectly.

32:49Bringing it up now.

32:52They took the engine and increased the water flow into the inlet of the engine

32:58to what was calibrated that they had experienced during the flight.

33:02I think we have our answers here why the engines died.

33:17The engine test leaves no doubt.

33:20That was a big aha moment for them.

33:23Because adding the ice to the water caused the engine to finally stop.

33:27A violent storm combining heavy rain and giant hail extinguished both engines on Flight 421.

33:37But the investigation isn't over.

33:40There's another mystery still to solve.

33:43Why did Flight 421 fly into such a severe storm in the first place?

33:47Why were the 737's advanced navigation systems not enough to help the crew steer clear of dangerous weather?

33:57Investigators review the satellite weather data from the day of the crash.

34:02Let me just take a look at this radar map.

34:05Okay, so, your track took you straight into the worst part of the storm.

34:18Why did Captain Roszak choose such a dangerous route?

34:22The plane's weather radar should have helped them find a way around the storm.

34:26Why would you enter the storm?

34:29Why not detour?

34:30I think we just veer a little to the left into that green gap.

34:35We should be fine.

34:36Pilots were of the impression that they had an opening that went all the way through the weather.

34:42The radar showed green.

34:44We should have been safe.

34:47Why would your radar indicate a safe passage?

34:51I don't know.

34:53But suddenly everything changed.

34:54It seems the radar didn't pick up the danger ahead.

35:01Where did this come from?

35:04The alley that they were trying to go down closed up on them and was not the good flight path that they were hoping for.

35:12Investigators need to know why.

35:14Strap in.

35:14They consult a radar expert.

35:22It's where they entered the storm.

35:24And learn that pilots can face the dangers of something called radar shadowing.

35:29Radar shadowing is the radar's inability to identify other weather that could be in front of you that you're trying to avoid.

35:38Radar shadow?

35:39Radar shadows occur when precipitation is so severe, radio waves can't penetrate the skies ahead.

35:47A shadow appears on the pilot's screen as a dark gap.

35:51So it would be deceiving that you were flying into some good weather and in reality you were entering into another severe storm.

35:59The Garuda plane's dangerous flight path finally makes sense.

36:02So what you're saying is they sought refuge on the radar shadow.

36:11The crew didn't realize they were flying into weather severe enough to knock out their engines.

36:17But there's still one unanswered question.

36:20The hailstorm killed the engines.

36:22Sergeant APU.

36:23But what killed the 737's power supply?

36:28We've lost our power.

36:32The plane lost its electrical supply, which means there was no power left on board at all.

36:39We were very concerned and needed to find out why this happened.

36:44Why is it electrical?

36:45Investigators know that Garuda Flight 421 somehow lost all electrical power.

36:56If they hadn't lost power, they could have restarted the engines once they were outside the storm.

37:04What happened?

37:06But they still don't understand how that happened.

37:09Thanks for coming, Captain.

37:11Please have a seat.

37:12Investigators hope Captain Roszak can remember some overlooked detail.

37:16I just have a few more questions.

37:19Now, take us through exactly what happened after the engines flamed out.

37:25As soon as the engines died, we followed the relight procedure.

37:30Engine start switches to flight.

37:32Engine start switches to flight.

37:34Start levers to cut off.

37:35Start levers to cut off.

37:36They followed procedure to the pinny.

37:38Relight failed.

37:39When the engines didn't relight, they tried to start the auxiliary power unit to restore electricity to the entire plane.

37:47And then what happened?

37:50Disaster.

37:51Start APU.

37:53Start APU.

37:59We've lost all power.

38:00Unfortunately, after two attempts to restart the engines and trying to start the APU, it depleted the battery.

38:12Heavy-duty aircraft batteries almost never die mid-flight.

38:16So why did this one?

38:18The captain doesn't have the answer.

38:20But he does provide one very important clue.

38:23Is there anything else that you can remember?

38:27The battery voltage was low.

38:3022 volts.

38:35Even before we initiated the restart sequence.

38:39It seemed odd, but we didn't have time to think about it.

38:42When I was interviewing Captain Rozak, he mentioned the battery capacity was just 22 volts when he tried to revive the engines.

38:5822 is within the limit, but it's the lowest value.

39:02So it's considered to be weak.

39:04A fully charged battery and a 737 has 24 volts.

39:10Are you sure it's 22?

39:12Not 24.

39:1322 volts.

39:15I remember.

39:16Another 2 volts might have made the difference in getting the engine started, or it's getting the APU started.

39:26Four weeks after the crash, searchers pull what could be the last piece of the investigative puzzle from the Solo River.

39:32The battery from Flight 421.

39:37One of its 20 cells shows signs of damage from before the crash.

39:42Evidence that seems consistent with the captain's observations.

39:46We found the cell condition was one of the most damaged.

39:51And it's reduced the battery capability quite significant.

39:57But how significant was the damage?

39:59Was the battery too weak to restart a flamed-out engine?

40:06Investigators stage a test to find out.

40:08Let's start water and ice up to 18 grams per cubic meter.

40:13They replicate the flight conditions and follow the exact procedure the pilots used trying to restart their engines.

40:19Okay, initiate restart engine procedure.

40:28Engine start switches to flight.

40:30Engine start switches to flight.

40:31Start levers to cut off.

40:32Start levers to cut off.

40:33Start levers to idle.

40:35Start levers to idle.

40:3730 seconds.

40:3828, 29, 30.

40:48Okay.

40:49First attempt failed.

40:51Battery to 20 volts.

40:54Keep precipitation ready.

40:56And let's see what happens to the battery in a second attempt.

40:59All right?

41:00So we'll start timing once again.

41:02And we're going.

41:03Try it again.

41:04Engine start switches to flight.

41:06Engine start switches to flight.

41:07Start levers to idle.

41:08Start levers to idle.

41:10Time.

41:1130 seconds.

41:1428, 29, 30.

41:19Battery has dropped to 12 volts.

41:22Making it practically useless.

41:24And now try to start the APU.

41:29Start APU.

41:35We've lost our power.

41:36They had no chance.

41:37The restart procedure completely drained their faulty battery.

41:42It was not capable to support the engine restart in emergency conditions.

41:49Finally, investigators understand all the contributing factors that knocked flight 421 from the sky.

41:57I think we just veer a little to the left into that green gap.

42:00We should be fine.

42:01A shadow effect on the radar leads the crew to mistake the worst of the storm for a clear path.

42:10The storm hits them with hail so severe, the engines flame out.

42:14Perform engine flame-out procedure.

42:16Engine start switches to flight.

42:18Engine start switches to flight.

42:19Efforts to relight the engines drain valuable power from a damaged battery.

42:26Without power, with their plane dropping fast, far from any airport,

42:32it was only Captain Roszak's incredible airmanship that prevented a total disaster.

42:38In their official report, investigators recommend better radar training for flight crews to help them navigate extreme weather.

42:51They also call for new procedures for flying in heavy rain and hail with the CFM56 engine, such as increasing the throttle setting when entering a storm.