Mayday Air Crash Investigations - S09 E07 - Doomed to Fail
Category
📚
LearningTranscript
00:00Just minutes from Strasbourg Airport an Airbus A320 slams into a mountaintop.
00:17Determine for your position.
00:19There are survivors.
00:20I'm not panicking because I'm going to burn.
00:25But they are still in grave danger.
00:27It's bitterly cold.
00:30And what they don't realize is that no one knows where they are.
00:35They could be anywhere in there.
00:38Expect this in the jungle or the rainforest, but not in a highly populated area.
00:46Before investigators can begin searching for what caused the crash of Air Interflight 148.
00:52They must first find the plane.
00:57Just find the plane.
01:37One, two, four, a decimal nine or five. Thank you.
01:46Captain Christian Hecke and First Officer Joel Charubin are experienced pilots with over 12,000 hours of flying time between them.
01:57The flight is a short hop between Lyon in central France and the city of Strasbourg in the mountainous Alsace region.
02:07The French airline Air Inter caters mostly to business travelers and prides itself on being timely.
02:17Crews are motivated to avoid delays, as former Air Inter pilot Gerard Arnoux explains.
02:22We were famous for a very short turnaround. And the faster we flew, the better wages we got.
02:32Have we been flying for 35 minutes yet?
02:3941 minutes.
02:40The crew is flying an Airbus A320, one of the most technologically advanced commercial airplanes in the world.
02:52Even before takeoff, the pilots programmed the autopilot to land on a specific runway in Strasbourg.
03:01The cockpit of the A320 is also very different from other planes.
03:05Instead of analog gauges, the pilots look mostly at digital displays.
03:16Strasbourg, good evening.
03:18Runway News 05.
03:20Transition level 5-0.
03:22Wind 040 at 1-8 knots.
03:26Visibility 10 kilometers.
03:27A recording from Strasbourg airport informs the crew of a change in plan.
03:33Due to high winds and poor winter weather, they'll have to land on an alternate runway.
03:4005 in service.
03:42Not the one programmed into the autopilot.
03:4505.
03:45What sort of wind are they giving us?
03:4918 knots.
03:5118 knots.
03:55Captain Hecke doesn't like the idea of changing runways.
03:59No chance.
04:01He was hoping to use runway 23, an approach that provides the autopilot with a precise navigational fix.
04:09The new runway, runway 05, is surrounded by mountainous terrain that can interrupt radio signals sent to the autopilot.
04:22If we go with the runway 05 procedure, we...
04:27Oh, no.
04:30Captain Hecke suggests a compromise.
04:33I'm putting back runway 23.
04:35Otherwise, I couldn't make the ILS interception.
04:39He'll program the autopilot to fly towards runway 23.
04:45But near the airport, the captain will take over the controls and make a visual landing on runway 05.
04:53You're taking 23, then?
04:55Yes!
05:02Ladies and gentlemen, we are commencing our descent.
05:05We ask you to please return to your...
05:06Nicholas Skourias is a university graduate student.
05:12It was a quiet day.
05:15I was expecting to go to see my girlfriend in Strasbourg.
05:21So I was very happy.
05:23Roger 854, proceed to GTQ, air level 140, contact Reims.
05:32Delta Alpha, Strasbourg.
05:34Yes, we intend to proceed to do an ILS on runway 23, then an indirect for runway 05 after that.
05:43The Strasbourg controller considers the captain's plan.
05:48He warns that there will likely be a delay due to heavy traffic.
05:51Given that we're going to have three takeoffs on 05, you risk waiting in the stack at 5,000 feet.
05:57We're not going to mess about like that, descending at full speed.
06:00If they had wound us in their hands, crips!
06:08Delta Alpha, Strasbourg.
06:10I hear you.
06:11Aware of the captain's frustration, the controller offers assistance.
06:15If you want, I can take you with the radar to lead you to Andlow at 5,000.
06:19Andlow is a navigational point on the approach to runway 05.
06:23It helps pilots align the plane for landing.
06:27Yeah, that's good.
06:29Oh, yeah.
06:30Okay, then turn left to heading 230 degrees.
06:34148.
06:35Turn left to heading 230 degrees.
06:40There you are.
06:40That will save you some time.
06:45Since runway 05 doesn't allow for a full autopilot approach,
06:49the captain must calculate the angle of descent on his own.
06:54That makes 3,3 degrees.
07:043,3 degrees is a normal flight angle that provides a good slope for landing.
07:11Slowly.
07:12The good path.
07:14Ladies and gentlemen, we are continuing our descent.
07:18The flight from Rio to Strasbourg was quite short.
07:23I think 50 or 45 minutes.
07:26Nothing special.
07:27It was very natural and very ordinary.
07:34Turn left.
07:35Steer 90.
07:400, 9 or 0 degrees, Delta Alpha.
07:43The controller talks flight 148 through the last turn
07:46to align the plane with the runway.
07:48Now 25 kilometers away.
07:52Then, 1st officer Cheruban notices the plane is slightly off course.
07:59We're headed inside.
08:01You're inside there.
08:03You should have started with 070.
08:06Yeah.
08:10At least that much.
08:11The controller also notices that the plane is off course.
08:20Here on the air, Delta Alpha.
08:21It has missed aligning itself with Andlow,
08:24the runway's electronic guidepost.
08:28Delta Alpha.
08:29You're passing to the right of Andlow.
08:31Nevertheless, he authorizes the landing.
08:36Authorized for final approach, 05.
08:42Delta Alpha.
08:42The captain initiates the landing sequence.
08:46Flaps towards 2.
08:48Flaps towards 2.
08:51Flaps at 2.
08:53Gild down.
08:53Ladies and gentlemen, we are going to land in a few minutes.
09:07Hekay notices that the plane is traveling too fast,
09:10so he extends the speed brakes.
09:12They disrupt air flow over the wing,
09:14which helps create more drag to slow the plane.
09:18We have to watch our descent.
09:21Via approach axis.
09:22The 1st officer is more concerned with their horizontal position
09:25in relation to the runway.
09:27It was 60.
09:28Check it out.
09:31But before the crew can adjust their course...
09:35Man!
09:36Man!
09:36Man!
09:36Man!
09:36Man!
09:37Man!
09:38Man!
09:38Man!
09:38Man!
09:38Man!
09:38Man!
09:39Man!
09:39Man!
09:39Man!
09:39Man!
09:40Man!
09:40Man!
09:41Man!
09:41Man!
09:42Man!
09:52Delta Alpha, your position.
09:54Delta Alpha, Strasbourg.
10:03The crash is catastrophic.
10:06The A320 has flown into the side of a mountain.
10:12Delta Alpha, your position.
10:17Flight 148 is no longer on radar, nor responding to radio contact.
10:24An emergency is declared at Strasbourg Airport.
10:29This is the last hit we got.
10:30We're flying about 20 kilometers away from the airport.
10:34Officials need to pinpoint the crash site, but it's not as easy as it might seem.
10:39The airport's radar is not recorded, there has been no signal from the plane's emergency
10:44beacon, and surprisingly no one has reported seeing a plane go down.
10:49It could be anywhere in here.
10:54The proposed search area covers more than 20 square kilometers of dense forest just outside
10:59Strasbourg.
11:09Nicola Scoria survives the crash of Air Inter flight 148 with only minor injuries.
11:18I took off my seatbelt, I tried to find my suitcase in the lockers, but there wasn't any lockers.
11:36I realized that I was alive, it was a crash.
11:38I saw a fire in front of me, and I panicked because I said to myself, I'm going to burn.
11:48I went to the back of the plane, of what remained of the plane.
11:56I found some other survivors.
12:02I was afraid of the explosion, I was in panic.
12:05With the smell of leaking jet fuel in the air, the survivors move away from the burning
12:10plane.
12:16We stayed together, waiting for the first aid.
12:20But the wait will be longer than anyone might expect.
12:26The first reaction that we have after the crash was, okay, in half an hour, one hour,
12:35most and worst, okay, the rescue team will be here.
12:40And it wasn't here.
12:42One hour after the crash, rescuers still have no idea where the wreckage lies.
12:55Scorius and the others now face a new ordeal.
13:00Surviving sub-zero temperatures in a dark and isolated forest.
13:07Two and a half hours after flight 148 disappeared from radar near Strasbourg airport.
13:14The missing plane has still not been located.
13:18Amidst growing tension, the French Aviation Bureau, the BEA, sends in its lead investigator,
13:24Jean Paries.
13:25I immediately called my two main investigators, and we organized the GO team.
13:34And we got prepared to rush to the site as soon as this site was located somewhere.
13:40The delay feels like an eternity.
13:43A little bit surprisingly long.
13:45We can expect this in the jungle or the rainforest, but not exactly in a highly dense populated area like the Strasbourg area.
13:57With no help in sight, Scorius returns to the wreckage to look for more survivors.
14:04I think that some people that die could have survived if the first aid came sooner.
14:17Nearly a thousand people search for the missing plane.
14:23But three hours after the crash, there's still no sign of it.
14:27Frustrated, Scorius goes looking for help.
14:31He stumbles into a TV crew trying to find the crash.
14:35But with no wreckage in sight, they react with skepticism.
14:39They didn't expect survivors from an airplane crash.
14:44Hey!
14:45Hey, you have to believe me!
14:47They didn't believe that I was one of the survivors.
14:51But believe me, I was because my face was black due to the smoke, the curazine and so on.
14:59Come on!
15:00The journalists follow him back to the crash site, where they discover eight other survivors.
15:14Finally, the first rescuers arrive.
15:18The crash site is located near the top of the 2,500-foot Monsanto deal, 19 kilometers from the runway.
15:26They found us after four hours and 30 minutes.
15:33So, it was a mess.
15:35I was very, very disappointed that at 20 kilometers from Strasbourg, they couldn't find us.
15:44A total of 87 passengers and crew have died, including the pilot and co-pilot.
15:52The survivors begin to tell their stories.
15:55But no one reports anything that might explain why the plane crashed.
15:59I don't know what happened.
16:01We were landing.
16:02I lost all consciousness.
16:04We must have hit the trees.
16:10Bob McIntosh, an American NTSB investigator, arrives at the crash site.
16:15The BEA of France recognized the international attention would be on this accident.
16:23Even though it was a domestic accident, he invited a group of international accident investigators to come and participate.
16:30Welcome to the team.
16:32The first priority for investigators is to retrieve the plane's black boxes.
16:38We have not removed the recorders yet.
16:42With the boxes trapped in the burning tail section, any delay could prove costly.
16:50We're very anxious about the state of the tape inside.
16:56Would it be possible to use it?
16:58Will we get the critical information we need?
17:01In France, aviation accidents are also investigated by the justice system.
17:08Paris and his team are not allowed access to the site until judicial officials secure the black boxes.
17:14I had a visual picture of the gendarmes, a transport police standing around keeping us away from the wreckage for a while.
17:25And we're very suspicious of these international observers.
17:28Maybe we should wait.
17:29Even taking photographs, which was somewhat surprising to us.
17:34In a previous crash, the crash of Air France Flight 296 in 1988, investigators waited 10 days before turning the black boxes over to police.
17:47Rumors persisted that these boxes had been tampered with.
17:52This time, police are keeping investigators at bay.
17:55I can recall seeing the glowing embers and seeing the flight recorder sitting there and not being able to intervene and say,
18:04get that thing cooled down as soon as you can.
18:11After midnight, the boxes are retrieved from the plane and sent for analysis.
18:16Investigators can only hope it's not too late.
18:19It was extremely hot.
18:21They looked damaged and they looked burned.
18:30In the light of day, investigators get some of their first clues from the crash site itself.
18:36They discover why the plane's emergency locator beacon didn't send a signal.
18:41It was actually destroyed by the impact.
18:44The beacon is located inside the cockpit and is designed to start working after a crash.
18:51Its failure suggests an unusually forceful impact with the ground.
18:56We had this first feeling that the descent was abnormally steep.
19:01Investigators examined the engines to see if they may have stalled before impact.
19:05If you find the blades curved and a lot of wood sucked inside the engines, then you understand that the engines were working properly.
19:19And that's exactly what they find.
19:22The plane clearly had power, yet it plowed steeply into a mountainside without ever sending out a distress signal.
19:34Investigators are puzzled.
19:35They hope that the box which recorded the plane's flight data will help them solve the mystery.
19:47Those particular recorders had the best survival record of any recorders.
19:52They were the top of the line as far as survivability is concerned.
19:55The black box is designed to survive temperatures up to 1100 degrees Celsius for half an hour.
20:03The tape recorder inside is protected by a capsule filled with water.
20:12When the recorder heats up, the water turns to steam, absorbing the energy and actually vents out through a little hole in the crash enclosure.
20:21But when the flight data recorder is opened, investigators make a troubling discovery.
20:29DFDR was totally damaged. Impossible to read anything from it.
20:36It was subjected to heat beyond the 30 minutes.
20:40The recorder was just never designed to withstand that kind of sustained heat.
20:45And so we were very disappointed.
20:47There's now only one hope for recovering the plane's flight data.
20:52A device called a quick access recorder, or QAR.
20:56Maintenance workers use the QAR to access the plane's computers, but it also records some flight data.
21:03Unlike the black boxes, the QAR is stored near the cockpit.
21:07Quick access recorders are not protected at all.
21:11They're up in the front end of the aircraft.
21:13Typically in the electronics bay.
21:16They are generally destroyed just from the impact damage.
21:19Investigators are encouraged to discover that in this case, the QAR has survived.
21:24But on closer examination, their optimism turns to frustration.
21:28The last 20 centimeters of the tape were burned and stretched and were damaged to the point that we couldn't use them into a machine.
21:46We couldn't read it.
21:47Investigators are desperate to retrieve the data, so they take a chance on an experimental technique.
21:56Known as the garnet technique, a light is shone through a mineral lens made of garnet.
22:00Use a garnet stone to visualize the magnetic pulses that are actually recorded on the tape.
22:11The special lens helps the technicians differentiate between the positive and negative magnetic pulses,
22:17which translate as binary digits or bits.
22:21There are 768 bits per second, so that's a lot of ones and zeros.
22:27You have to be very precise in moving the tape under the lens or the garnet to make sure you don't miss a bit or read the same bit twice.
22:39So it's difficult.
22:41Analyzing the data is even more painstaking.
22:45It took about a day to read a second of recording.
22:51Any additional second recovered could reveal something that would make a difference.
22:58The effort to retrieve all the QAR data could take a month or more.
23:08In the meantime, the focus of the investigation shifts to the cockpit voice recorder.
23:13It was positioned just above the other black box.
23:18The cockpit voice recorder, which was just inches away but outside of the ashes, had air passing over it, survived.
23:27The recording reveals the captain's anxiety early on in the flight.
23:32You are taking 23 then?
23:35Yes!
23:37Investigators know that landing on runway 05 requires what's called a non-precision approach.
23:43That means pilots receive electronic guidance only on their horizontal position, left and right.
23:50They get no guidance when it comes to altitude.
23:52The non-precision approach is significantly less accurate.
23:59It's not really difficult, but they are less comfortable.
24:0205.
24:04What sort of wind are they giving us?
24:0618 knots.
24:08The non-precision approach increases the demands on the pilots.
24:12Investigators can also hear that the captain had concerns about landing on runway 05.
24:1648, Delta Alpha, UR number one with UR DME runway 05.
24:29Runway 05.
24:3210 knots ago.
24:35That won't work.
24:37It's a lot of distress over a non-precision approach.
24:41Wondering what can cause such distress,
24:43investigators research pilot training at Air Inter.
24:47They find that most pilots did not have extensive training making non-precision landings in the new A320.
24:56I think we should have had double the training compared to an older plane.
25:01Investigators ask the airline for detailed records on the pilots' history of runway approaches.
25:06They're intrigued by what they discover.
25:10Captain Hecke had landed at Strasbourg countless times, but he had never landed an A320 there using a non-precision approach.
25:27I'm not going to mess around like that, descending at full speed.
25:29Clearly, the captain was uneasy about having to execute a landing he had never made before.
25:36I think the captain was worried about making it in at a minimum amount of time.
25:41In the minimum amount of delay.
25:43Have we been flying for 35 minutes yet?
25:46And the co-pilot was worried about not getting in trouble by offending the captain.
25:51At least that much.
25:52More research into the pilots' work history offers yet another revelation.
25:58While the two pilots had flown more than 12,000 hours between them,
26:03they were both still relatively new to the highly advanced A320.
26:07It's 05 in service.
26:09The aviation community misunderstood the magnitude of changes brought by the new Airbus A320.
26:16The captain had only 162 hours in the A320, and the co-pilot even less, just 61 hours.
26:31Behind this accident scenario, there's an issue of confidence of the crew in themselves, in the aircraft.
26:4018 knots. No chance.
26:44They were not prepared, really, to fly in this kind of condition.
26:49They had warned us in advance.
26:51Cripes!
26:56Investigators conclude that the crew's training was insufficient.
27:00But that alone does not explain the crash.
27:04Merde!
27:05Merde!
27:06Merde!
27:07Merde!
27:08Merde!
27:09Merde!
27:10Merde!
27:12Merde!
27:14Merde!
27:16Investigators search for other factors in the crash of Flight 148.
27:20They review the conversations between the crew and air traffic controllers.
27:24If you want, I can give you radar headings and take you to Enloe at 5,000.
27:29Yeah.
27:31Yeah, that's good.
27:32The radar vector makes flying easier.
27:35The captain was happy because it was reducing his workload.
27:41Turn left, steer 90.
27:43With the controller's assistance, this landing should have been very simple.
27:48But when investigators reconstruct the plane's trajectory using radar information from various stations around the airport, they discover a shocking error.
27:56The zero-nine-zero heading started here.
27:58Zero-niner, zero-degrees, Delta Alpha.
27:59But it won't take them to Enloe.
28:00Last radar vector the controller gave was incorrect.
28:02It sent them...
28:04...closer to the mountain.
28:05There were, of course, because of following the heading they got from the radar vectoring, they found themselves in this undershoot situation.
28:10You're inside there.
28:11You should have started with 070.
28:12Yeah.
28:13Yeah.
28:14Investigators are also troubled by the controller's choice of words when he warned the pilots, incorrectly, that they were headed to the radar.
28:16Delta Alpha, you're passing to the right.
28:17Delta Alpha, you're passing to the right.
28:19You're passing to the right.
28:20Delta Alpha, you're passing to the right.
28:26Closer to the mountain.
28:28Closer to the mountain.
28:29There were, of course, because of following the heading they got from the radar vectoring.
28:32They found themselves in this undershoot situation.
28:34You're inside there.
28:35You should have started with 070.
28:36Yeah.
28:37Investigators are also troubled by the controller's choice of words when he warned the pilots, incorrectly, that they were headed to the right.
28:44Delta Alpha, you're passing to the right of Enloe.
28:48From the pilot's perspective, the plane was on the left side of the runway, not the right.
28:54It could only add to their confusion.
28:56Le contrôleur, en fait, bon, il a fait un...
28:59It was very poor guidance, because he didn't employ the usual terminology.
29:04Et il n'a pas utilisé la phraseologie standard.
29:08So...
29:11Investigators recommend that controllers use only compass points when giving directions.
29:16Never the words right and left.
29:21The controller's mistakes clearly brought the plane closer to the mountain.
29:26Turn left. Steer 90.
29:29But once again, investigators feel they don't have the whole story.
29:38It's not something totally abnormal to start a descent from this situation.
29:45Flaps towards two.
29:47Flaps towards two.
29:50It's not what you expected to do every day, but it's not outside the tolerance of the concept of this approach.
30:00Gilda.
30:00When investigators study the plane's reconstructed flight path, they discover something more alarming than the plane's horizontal misdirection.
30:11As it circled the mountain, the plane inexplicably entered a dangerously steep and rapid descent.
30:18Perhaps two and a half times the normal rate of descent.
30:23As lethal as that altitude.
30:27Without the steep descent, they would have cleared the mountain.
30:30If the vertical trajectory had been correct, they would have no problem at all.
30:38Finding the cause of that sudden descent is now key to understanding why 87 people died in one of the most advanced passenger planes on Earth.
30:47The descent was initiated at 1,800 hours, 19 minutes and 38 seconds.
31:04That is the point of no return.
31:08By studying flight 148's trajectory, investigators determined that the rapid descent began 60 seconds before the crash.
31:21There is no indication on tape that the descent was deliberate.
31:24How it happened and why the crew didn't notice is a mystery.
31:33It should be a no-brainer.
31:35Keep your track of the altitude.
31:36The cockpit altimeter gives pilots a constant readout of their altitude.
31:42Altimeter is a very precise instrument.
31:44They become very reliable.
31:46They're accurate between 5 or 10 feet.
31:48Ignoring it would be a major error in flying protocol.
31:56The recording reveals just one single remark from the crew about their descent.
32:02We have to watch our descent.
32:04It occurred 16 seconds before the crash.
32:07Watch our descent.
32:08The captain had just extended the speed brakes.
32:11The aircraft was accelerating abnormally.
32:14The captain started to realize there was something wrong with the descent rate.
32:19But the first officer changed the subject.
32:21The approach axis, we're hitting the axis a half point off.
32:26There.
32:27It was 60.
32:28It was 60.
32:29Check it out.
32:29There we are.
32:30We refocused the captain's attention on the lateral situation rather than the vertical situation, which was the main problem, of course.
32:43And they both failed to recognize the situation.
32:47I think they were planning that we're going to break out of the clouds so they would be able to see the runway.
32:53And they wouldn't need to do the full instrument approach.
32:56It was 60.
32:57Check it out.
32:57But the plane never left the clouds.
33:01There's an old adage in aviation.
33:03Rocks have been known to hide out in those clouds.
33:06Merde!
33:06It now seems clear that the crew was not monitoring their altitude closely enough.
33:13But a bigger mystery remains.
33:16We can only guess why...
33:17What caused that deadly descent?
33:25After months of work, investigators may finally have the answer.
33:29All the available flight data from the damaged quick access recorder has been recovered.
33:34We were very anxious to be able to read as much as we could.
33:40The data confirms that just before the crash, the plane was speeding towards the ground at an extremely high rate, 3,300 feet per minute.
33:51It also confirms that the angle of descent was dangerously steep, much greater than the 3.3 degrees selected by the captain.
34:01Decimal 3 degrees.
34:04That's quite a difference.
34:07Investigators now wonder, did the autopilot malfunction?
34:12Did it somehow fail to obey the captain's safe descent angle and send the plane into a deadly nosedive?
34:19What state was it in before the accident?
34:21Unfortunately, the flight control unit which houses the autopilot is too badly damaged to provide any definitive answers.
34:32We can never demonstrate that this FCU on this aircraft during this flight functioned properly or not.
34:41But then, when he returns to study the flight data, Paries discovers something that may finally reveal the cause of the crash.
34:51He notices a similarity between two key numbers.
34:54The plane's vertical speed, 3,300 feet per minute, and the intended flight path angle, 3.3 degrees.
35:01Coincidence?
35:08Paries uses a flight simulator to test a new theory.
35:12Can you show me a descent of 3,300 feet per minute?
35:15He believes that the similarity is no mere coincidence.
35:21On the autopilot, there are two descent modes, flight path angle and vertical speed.
35:29But they are both displayed on the same window.
35:33So, 3,300 is abbreviated to 33.
35:38Now, show me a flight angle of minus 3.3 degrees.
35:44The problem on this aircraft was that the two values were visible on the same window and controlled by the same knob.
35:543.3 degrees.
35:59Minus 3.3 degrees.
36:01Paries strongly suspects that the confusing display tripped up Captain Hecke.
36:07So, it wouldn't be hard to make that mistake, would it?
36:11The confusion is quite easy between the two modes if you don't do it carefully.
36:19If the captain failed to push the mode selector knob,
36:23then entering 33 would not have initiated a safe 3.3 degree angle of descent.
36:29Instead, it would have put the plane into a deadly rate of descent of 3,300 feet per minute.
36:35Two months after the crash, another air-intair plane enters a dangerously steep descent for the same reason.
36:49The crew only discovered the problem when they broke out of the clouds.
36:54Those pilots also confused the plane's flight path angle with its vertical speed.
37:01They were lucky enough to have a much higher cloud base, so they could correct the problem.
37:08Further research reveals an industry-wide problem with the A320.
37:13Many people confuse these modes, especially during training, and many of them fell in the trap, even after the training.
37:24Eager to test his new theory, Jean Paries programs a simulator with all the known data from Flight 148.
37:31He then inputs the same rate of descent he believes the air-intair pilots selected.
37:41If Paries is correct, the simulation will end with the plane hitting the mountain.
37:48But it doesn't.
37:49We're missing something.
37:50Strangely, this didn't lead to a crash.
37:54Every approach would overfly this obstacle by a significant margin.
38:01Have we factored in the wind?
38:03We started to work on other alternate hypotheses.
38:08Let's try again, but initiate the turn sooner.
38:12But nothing was really credible.
38:15No matter how hard he tries, Paries cannot simulate the crash.
38:22Unable to explain why, he turns to the plane's manufacturer for help.
38:27Thanks for bringing this to my attention.
38:29After much research, an Airbus designer comes to Paries with an explanation about a little-known element of the autopilot's design.
38:36In emergency situations where the A320 needs to change direction quickly, the autopilot is programmed to reverse the plane's direction at twice the normal rate.
38:48The reaction of the autopilot would be much faster.
38:52And these cases were typically when you were descending and asking the autopilot to climb, or climbing and asking the autopilot to descend.
39:03We immediately went back to the data at the very second at which the descent was commanded by the crew.
39:12Gear down.
39:13Paries discovers a tragic coincidence.
39:18Sadly, we found that at this very second, there was turbulence.
39:24There was an ascent.
39:26It's very slight, but there it is.
39:28The momentary turbulence caused the plane to climb slightly.
39:32And this led to a positive 600 feet per minute vertical speed for maybe half a second.
39:41It was during that same half second that the crew commanded the plane to descend.
39:45It was 60. Check it out.
39:47The autopilot read this as an emergency, requiring a blazingly fast descent.
39:52That could be it.
39:56Investigators now contemplate a terrible thought.
39:58Could a random gust of wind, hitting at exactly the wrong split second, have been the difference between life and death?
40:07Here it comes.
40:13And we've got a crash.
40:15Paries's theory explains every aspect of the crash.
40:18The crew's confusion with the autopilot display...
40:23Three decimal three degrees.
40:27...caused the plane to descend dangerously close to the mountain.
40:32Turbulence and an obscure safety feature brought it even closer.
40:37It was a fatal combination.
40:38It's a fascinating lesson about the random dimension of accidents.
40:47Half a second before, half a second later, they wouldn't have the accident.
40:53The discovery of a confusing cockpit display...
40:57...has enormous implications for the entire industry.
41:01The flight instrumentation of aircraft like the DC-10, MD-11s, the 7-4s and so on...
41:11...all the Boeing products and all the commuter products that were using that avionics suite...
41:16...had this vulnerability about it.
41:21Investigators now face a daunting question affecting aircraft safety around the world.
41:26If the design of the autopilot interface isn't changed, how many more people could die?
41:40There's mounting evidence that the design of the autopilot interface on Airbus A320s...
41:45...led the air interpilots to accidentally dial in a dangerous rate of descent.
41:50Three decimal three degrees.
41:53We felt a need to start the industry to work on this.
41:58The plane's manufacturer, Airbus, responds immediately.
42:03The main change, which was very quickly made, was to change the display window.
42:10With the new design, if a pilot selects a vertical speed of 3,300...
42:14...the entire four-digit number is displayed.
42:18So, the confusion between an angle and a vertical speed was no longer possible.
42:23For investigators, only one mystery remains.
42:32All Airbus A320 jets are designed to be equipped with a safety device...
42:36...known as a Ground Proximity Warning System, or GPWS.
42:39Which is a downward-looking, single-purpose radar...
42:44...that tells you how high you are above the ground, directly beneath the airplane.
42:48And if it gets to be, uh, too low, it'll set off a warning.
42:51Pull up, terrain. Pull up.
42:55Pull up.
42:56Pull up.
42:57But Captain Hekay...
42:58We have to watch our descent.
42:59...never received a warning for one very simple reason.
43:02His A320 didn't have that alarm.
43:05The first question, of course, was why the aircraft was not equipped.
43:26So, it's not part of the minimum equipment list.
43:32The Air and Terror Management had decided they did not like the false warnings...
43:40...that had been produced by GPWS equipment.
43:45Normally, most planes fly slower than 250 knots when under 10,000 feet.
43:52But we flew at 350 knots until the final approach.
43:56So, at those speeds, GPWS was always giving off false alarms.
44:09This decision, while legal, prevented the pilots from having one last line of defense...
44:17...before crashing into the mountain.
44:19It's impossible to imagine that the pilot wouldn't have pulled up if he'd heard the alarm.
44:28We should have a GPWS on commercial flights.
44:32In any case, yes.
44:33That's an obvious conclusion.
44:37The report will list these causes.
44:41Investigators conclude that there was no single cause for the crash of Flight 148.
44:47The tragedy involved an ill-fated combination of many different weaknesses in the airline industry.
44:57We made 35 or so recommendations, including pilot training about the ground proximity warning system, and so on.
45:09The recommendations lead to sweeping changes.
45:13Pilots must now have more A320 training before getting behind the controls.
45:22One of the two pilots now need to have at least 300 hours on the plane.
45:26They estimated that 300 hours were enough.
45:31Another change.
45:33The design of a more heat-resistant black box.
45:36The FAA did a test, did some studies, what the thermal characteristics of post-crash fires were.
45:43Came up with a value of 260 degrees C for 10 hours.
45:50Delta Alpha, your position.
45:53Air Inter Delta Alpha, Strasbourg.
46:00As a result of the Strasbourg crash, the A320 is now a safer plane.
46:06You can only get this change if there is what people perceive to be a good reason.
46:16And sadly, a good reason is still an accident.
46:21But improved aviation technology is still no substitute for well-trained, well-prepared pilots.
46:28There's an old axiom in aviation that you taught early on that never let an airplane take you somewhere
46:37that your brain hasn't visited at least five minutes ahead of time.
46:40This is an excellent example of a flight crew that didn't follow that particular axiom.
46:58As if it12, there has two levar company who can stay in the water,
47:12have some energy pre- sanitation.
47:14There may be two ram 약ri in the air of the Titanic.
47:15KeepSer practices and lock them into capacitances.
47:20For example, we definitely read aboutathy,