- 6 months ago
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00:01Staring down a thunderstorm above the North Sea.
00:04Take a look at that.
00:06I don't like it.
00:07A modern turboprop is struck by more than a million volts.
00:13After the lightning strike, you're obviously looking to see,
00:16have we been damaged?
00:18Damn it, the plane's not responding. Help me pull.
00:20You can fly an aircraft without a compass,
00:22you can fly an aircraft without a radio.
00:24We've been struck by lightning and are having controlled difficulties.
00:27But you can't fly an aircraft without functioning controls.
00:30But investigators can't figure out how lightning
00:33could have caused the plane to behave the way it did.
00:36Look at that.
00:37I mean, the elevators are trying to get the nose to pitch down instead of up.
00:40We've not come across an aircraft
00:42where there would be this difference between the pilot input
00:45and what the aircraft was actually doing.
00:47Oh, no!
00:49We're dropping!
00:50They were so distracted by that,
00:52they failed to see what was really going on.
00:56B-2, B-2.
01:01Oh, up!
01:02T-9, 1-0, internal to air.
01:07Contact you, contact you.
01:08I'm only six now.
01:09We have to hear off of at night.
01:11It's 6.45 p.m.
01:27Logan Air Flight 6780 cruises over the North Sea near Scotland.
01:35Let's get lower. Request Flight Level 110, please.
01:38Approach Logan Air 6780, requesting descent to 110.
01:456780, descent to 110.
01:48The plane is more than halfway through a 65-minute flight.
01:55Most of the passengers live on the Shetland Islands.
01:59All done. Yes, thank you. I'll take that.
02:02Many are returning home from holiday shopping in Aberdeen.
02:05Air travel is massively important to residents in Shetland.
02:11It's important for work meetings, it's important for sporting events, for holidays.
02:17It's the fastest way to travel off-island, so it's quick and convenient.
02:21The captain is experienced. He has more than 5,000 flying hours, and is the pilot flying tonight.
02:32Passing Flight Level 150.
02:34The first officer is monitoring the instruments and handling all communications.
02:39Approach Logan 6780, descending through Flight Level 150 for the ILS Runway 27.
02:45She has more than 1,000 flying hours.
02:50Crew had a good total experience.
02:53Of course, they didn't have a lot of experience flying the Saab 2000, but still, it was a normally experienced crew.
02:59The Saab 2000 is a twin-engine, high-speed turboprop.
03:06It's a plane that aviation analyst Hans-Peter Graf knows extremely well.
03:10The Saab 2000 is the most advanced turboprop, still existing and flying.
03:16It has such a jet-like performance, paired with low fuel consumption.
03:23And it had real good performance to fly in and out of mountainous terrain.
03:29They're travelling north from Aberdeen, Scotland, to Sumbra on the Shetland Islands,
03:35a remote archipelago prone to winter swalls and even hurricanes.
03:39Logan Air 6780, for your information, looks like the ATIS antenna at Sumbra has been struck by lightning,
03:51so the system's not functioning.
03:53I'll update conditions when I get them.
03:55OK, thanks for the update.
03:57There's been a lot of that so far this winter.
04:01The ATIS, or Automatic Terminal Information Service,
04:05provides pilots with continuous broadcast of essential information.
04:09It broadcasts weather and airport information every 30 minutes,
04:15on which the pilots will base their approaches and landings.
04:21Why don't you tune ATIS in anyway?
04:26Sumbra Information Tango, winds 290 at 3-4, gusting 4-7, visibility...
04:33Guess it didn't get fried after all.
04:35Gusting 4-7, it's going to get a bit rough on the way down.
04:39The winds at Sumbra Airport are blowing up to 47 knots, 54 miles an hour.
04:48The crew will be facing strong gale force winds while landing.
04:52I travel by air a lot, and it does get windy.
05:00We were expecting a little bit of turbulence on the way.
05:03We knew a flight of that size, it's a small flight.
05:05You do feel turbulence more than what you would on a bigger plane,
05:09but it was nothing unusual.
05:11The captain wants to be ready for any unpredictable weather thrown at them.
05:15Let's brief in case of a lightning strike.
05:18Copy that.
05:19OK. Ah, right.
05:21Instrument lights up full in case we get blinded.
05:24Torches are here and here on your side,
05:26and the emergency elevator trim switch is overhead.
05:29Any questions?
05:30No questions.
05:31The statistics suggest that a particular aircraft will probably get a lightning strike
05:36about one and a half times a year.
05:40You don't know when it's coming, of course,
05:42and the thing you're aware of is that these lightning strikes
05:46can affect the electronics and the avionics in the aircraft.
05:50The crew prepares the plane for the turbulence ahead.
06:18Let's get them buckled in back there.
06:2016 miles from Sombra Airport,
06:31Flight 6780 turns on to its final approach to the runway.
06:47Take a look at that.
06:50I don't like it.
06:55There's some bad weather developing off the end of the runway.
06:58Approach, northern 6780.
07:01There's a big storm cell on radar just off the runway.
07:03We might need to discontinue.
07:056780, roger.
07:07Let me know.
07:08All crews going into an airfield in these sorts of conditions will be wary of the thunderstorms activity around them.
07:17The pilots consider their options.
07:22How much fuel do we have left?
07:252,500 kilos.
07:26You want to head back to Aberdeen?
07:27Well, let's circle.
07:28Make another attempt.
07:33They abandoned the approach when they saw a lot of precipitation on their weather radar just ahead of them.
07:40Up drafts, down drafts, wind shears, which are not predictable.
07:45So you better go around and wait or divert to another airport.
07:50Logan, 6780.
07:51We're going to circle around.
07:53Turning 180 for now.
07:556780.
07:56Understood.
07:57Maintain 2,000.
07:58He obviously made the decision that at that time he would just turn away from the airfield
08:04and probably allow that weather to pass through and then have another approach.
08:15As the pilots circle for another landing attempt.
08:21Oh, crap!
08:23It sounded like a gunshot.
08:29It was just a very short, sharp noise and a flash.
08:33I thought at that point that it was something that had happened to the engines.
08:37If you experience a lightning strike, especially at night, it's a very bright light.
08:42You can smell a burn smell, ozone smell, and that sure is frightening or fearsome to every crew.
08:51Circuit breakers look fine.
08:54After the lightning strike, you're obviously looking to see, have we been damaged?
08:59Are the instruments still working correctly?
09:01And I have control.
09:04But something's wrong.
09:06The controls feel really heavy.
09:09Damn it, the plane's not responding.
09:11There must be a degree of panic will set in where the controls are just not responding.
09:19The plane isn't responding.
09:20Mayday, mayday.
09:21This is Logan Air 6780.
09:23We've been struck by lightning and are having control difficulties.
09:26Please clear the airspace.
09:29I knew that there was definitely something not right.
09:32I was terrified.
09:33Logan Air flight 6780 is in distress, 2,000 feet above the North Sea.
09:45Logan Air, Logan Air, this is Logan Air 6780.
09:48Please clear the airspace.
09:506780, copy.
09:52If you can, sails on board and fuel remain in.
09:5533 sails on board.
09:572,500 kilograms of fuel.
09:59Copy.
09:59All options are available.
10:01Do you want to land or divert?
10:05Without knowing what's wrong with the plane.
10:07It's really fighting me.
10:09It's too risky to attempt landing in a storm at Sombra Airport.
10:14We should divert back to Aberdeen.
10:15Better conditions.
10:16Agreed.
10:17Aberdeen Airport is 190 miles away.
10:21Let's try climbing to 4,000.
10:246780, we're going to divert back to Aberdeen.
10:27Something's wrong.
10:28I can't get the plane to climb.
10:31How's your side?
10:33It's really heavy.
10:36Trim's not doing anything either.
10:38If you grab on the yoke and the airplane is not responding,
10:42they realize, hey, there's something wrong.
10:44We need to do something.
10:50Finally, the crew catches a small break.
10:55Altitude is increasing.
10:56Keep on it.
10:59The plane is climbing, but not as quickly as it should be.
11:05The elevators might be damaged.
11:08In two minutes, the plane has barely climbed 2,000 feet.
11:12The first officer worries the lightning strike may have disabled their instruments.
11:17Aberdeen, 6780, what's our altitude?
11:20I'll show you approaching 4,000 feet.
11:25But the controller is getting the exact same readings as the crew.
11:30We're really not going anywhere fast.
11:32Pull!
11:33I'm almost all the way back.
11:35Let's face it, you can fly an aircraft without a compass, you can fly an aircraft without a radio, but you can't fly an aircraft without functioning controls.
11:43And then, the unthinkable happens.
11:48Oh, no!
11:50Come on!
11:51We're dropping!
11:54Flight 6780 plunges uncontrollably towards the North Sea.
11:58The flight went into that nosedive, so we knew immediately that something wasn't right with the plane.
12:086780.
12:103800 now.
12:12600.
12:133400.
12:14The pilots wrestle with their controls as the plane speeds towards the water at 350 miles an hour.
12:23You're descending.
12:252,000 feet.
12:271800 feet.
12:31The dive was so fast, you just felt like your heart was in your mouth.
12:35I had no idea how close we were to the sea, you couldn't see anything, it was just pitch black.
12:42It was terrifying, it was really scary.
12:441,500 feet, you're descending.
12:50Nothing's working!
12:51Come on!
12:53Pull!
12:55Up!
12:58The airplane is less than 10 seconds from impact.
13:03Must be incredibly frightening, because the pilots would be aware of their rate of descent, they would be aware of their altitude, and they would be aware of how much time left they had
13:14to effect a recovery.
13:15I love it, Andrew!
13:17Speed!
13:18Speed!
13:19In a last-ditch effort to save the plane, the captain increases engine power.
13:33We're climbing!
13:34So increasing the power may increase the amount of air flow over the wings and give you a little bit more lift to allow the aircraft to pull out of its descent.
13:44We were travelling at such a speed that when the plane started pulling up again, it was a kind of a sensation of being on a roller coaster.
13:56It was definitely a relief to start climbing after that nose pitch.
14:00The pilots have avoided near catastrophe, but now they need to get their plane back to Aberdeen safely.
14:10In the moments after that, we had a period of just terrible turbulence, the worst turbulence I've ever experienced.
14:16The man behind me started vomiting, everybody was kind of... The flight was quite quiet, though. It was kind of eerily quiet.
14:26Requesting flight level 240.
14:286780.
14:29Roger. Climber maintain.
14:31240.
14:35The controls are working better now.
14:42Ladies and gentlemen, this is the captain.
14:44It was at that point the pilot came on and told us we'd been struck by lightning and we were heading back to Aberdeen.
14:51We had some flight control issues.
14:54Everything is under control now.
14:55We'll be landing in Aberdeen in 15 minutes.
14:59And please expect to see some emergency services on the ground when we land.
15:03Not to panic. It's just a standard precaution.
15:08When you go through a moment like that, you...
15:11Yeah, you panic until you're on the ground.
15:14Let's fly a straight and approach.
15:21And get this plane on the ground as soon as possible.
15:23The pilots of Logan Air Flight 6780 are on final approach to Aberdeen Airport.
15:37Aberdeen 6780, established on the localiser runway 16.
15:41Not knowing which instruments they can trust, the pilots carefully configure the plane for landing.
15:48Flaps 35.
15:49Flaps 35.
15:54Control feels normal.
15:56Having avoided disaster twice already, their sole focus is to get the plane safely on the ground.
16:02130.
16:03Speed looks good.
16:05Decision height.
16:07Runway inside.
16:08Continue.
16:09The pilot came on and told us we'd be expecting a normal landing, but the emergency services would be on the runway.
16:16That's the way we weren't to be alarmed if we saw the lights.
16:31All right.
16:3250 knots coming out of reverse.
16:34Check.
16:35The landing was smooth in Aberdeen.
16:41I was just glad that we were on the ground.
16:43Happy to be on solid ground.
16:46Me too.
16:48I burst out into tears.
16:50It was relief more probably than anything.
16:52A little bit of shock probably too.
16:54It's up to investigators at the Air Accidents Investigation Branch, or AAIB, to figure out what went wrong.
17:09David Miller is the deputy chief overseeing the investigation.
17:13I decided that this would be a full investigation because of the closeness this aircraft came to disaster.
17:23We then dispatched a small team of investigators to the operator's base to interview the crew and to examine the aircraft.
17:34Very quickly, the flight data and cockpit voice recorders are recovered from the Saab 2000.
17:40Great work.
17:41Let's hope they can provide some answers.
17:45Let's hope.
17:46The normal process for an investigation is the investigators take the recorders, the copy voice recorder and the flight data recorder,
17:52bring them back to the laboratories and recover the data.
17:55Looks to be in pretty good shape.
17:57Unusually so.
17:58Yeah.
18:00Investigators need to confirm the crew's report of a lightning strike,
18:04as well as the flight attendant's account of seeing an orb of light pass through the cabin.
18:11All lightning is a rare and little understood phenomenon known to precede lightning strikes inside airplanes.
18:19All right.
18:27Well, there's no damage in the wingtip.
18:29Mm-hmm.
18:29A lightning can strike more or less anywhere on an aircraft,
18:35but it tends to strike on the leading edge of the wings, on the radome at the front of the aircraft.
18:45Soot marks on the radome.
18:48Investigators see signs of a lightning strike on the nose of the aircraft.
18:52Looks like some surface damage as well.
18:55Yeah?
18:56Yeah.
18:57The point of strike will often leave scarring, localised burning, sometimes a small hole.
19:05Right, let's see where an exit of the aircraft, then.
19:15Elevators look fine.
19:16Hang on.
19:25Have a look at that exhaust cone.
19:28Oh, yeah.
19:32That's where the lightning exited.
19:34Look at it. Parts of it completely melted.
19:36There was a little bit of burning damage both to the front of the aircraft
19:39and the exit point of the lightning strike,
19:41which was at the very tail of the aircraft where the auxiliary power unit exhaust was placed.
19:46Oh, crap!
19:50The team now knows how the lightning struck the plane.
19:56The controls feel really heavy.
19:59So one of the first things to go and have a look at,
20:01what was the effect of the lightning strike?
20:03Were the systems damaged? Were there malfunctions?
20:09Okay, you ready?
20:10The AAIB tests the plane's flight controls to see if they're working.
20:16Okay, check the rudder.
20:24Looks good. How about the elevators?
20:26Yeah, elevators are working, too.
20:35Everything checks out.
20:37Investigators are perplexed.
20:39If the plane was functioning properly,
20:42why did it become so difficult to control after the lightning strike?
20:46There were no abnormalities,
20:49no system defects that we could find either structurally or within the avionics.
20:54Beyond that, it looked like a completely normal serviceable aircraft.
21:01AAIB investigators interview the pilots of Flight 6780.
21:05When we're fortunate enough, as in these circumstances,
21:10to have a surviving flight crew,
21:11then their recollections are really important for us to understand
21:14exactly how the event progressed from their perspective.
21:19So what happened after the lightning struck the plane?
21:21After the lightning struck, the autopilot disconnected.
21:32I have control.
21:33The crew of the aircraft became aware fairly shortly after the lightning strike
21:40that the aircraft wasn't responding as they expected to their flight control inputs.
21:44And then what happened?
21:47We had control issues.
21:50The plane wouldn't climb.
21:51We tried everything and the plane wasn't responding.
21:56The pilot flying was finding that he was having to put an increasingly strong
22:01backward effort on the control column.
22:03to raise the nose of the aircraft.
22:05I can't get the plane to climb.
22:07How's your side?
22:09It's really heavy.
22:12Jim's not doing anything either.
22:13The aircraft wasn't responding the way that he expected.
22:17And then?
22:19And then we entered a steep nosedive.
22:21And the control issues continued.
22:31Nothing's working!
22:32Come on!
22:37Speed!
22:38Speed!
22:39It wasn't until after we'd increased power that we were able to get the aircraft under control.
22:52Really?
22:53Why did the crew believe that they had control restrictions and control problems
22:57when in fact testing of the aircraft showed that there were no faults?
23:07Let's have a listen, shall we?
23:09Puzzled by the crew's account of the incident on board flight 6780,
23:14investigators turn to the cockpit voice recorder for answers.
23:18It will answer many questions as to why things were happening the way they were
23:23and how the crew were working together and interacting together.
23:26Aberdeen Ground 6780, taxiing on whiskey for parking stand 7.
23:32But something's not right.
23:35Aberdeen?
23:37Now this is from when they landed back at Aberdeen.
23:39Right, can you stop it and go back to the top and play the game, please?
23:46Aberdeen Ground 6780, taxiing on whiskey for parking stand 7.
23:50That's all there is.
23:53Well, that's not going to help us very much now, is it?
23:57The CVR has recorded over the critical moments of the flight.
24:01It's a major setback for the investigation.
24:04We discovered that the cockpit voice recorder, which only lasts for 30 minutes,
24:08has been overwritten by subsequent events.
24:11So there was no record of the crew conversation
24:14and how they interacted with each other.
24:19And so you have to look elsewhere for that information.
24:26Right, this is what we know so far.
24:28The lightning struck, the autopilot disconnected,
24:32they had control problems.
24:33Then the plane did a nosedive.
24:36Well, let's review the data.
24:38Will the data recorder provide the answers they need to solve this case?
24:45Flight data recorders often add a level of detail
24:49that simply can't be gained from the witnesses themselves.
24:53And crucially, quite often the information that's gathered from a recording device
24:57offers a slightly different perspective
24:59to what we might get from personal recollections.
25:03Stop.
25:04This is where the lightning struck at 2,000 feet.
25:07Right, and then for the next two and a half minutes,
25:09there's a slow, uneven climb to 4,000 feet.
25:12And then they are in a very steep nosedive,
25:1520 seconds towards the North Sea.
25:21That's 9,500 feet per minute.
25:25Investigators are struck by how close the flight came to total disaster.
25:30It was seven seconds from plunging into the sea
25:33before they finally managed to pull out at 1,100 feet.
25:37The aircraft had a very high rate of descent in the moments
25:40before it reached that height,
25:41and so we were really very close to a very serious accident.
25:46What were the pilots doing to recover from the dive?
25:51Look at the control column data.
25:54Right after the lightning struck,
25:56the crew pulled back on the control column to pitch the nose up.
26:02I have control.
26:08Controls feel really heavy.
26:09Look at the line.
26:12I mean, they're having a very difficult time getting that plane to climb.
26:16We know from the data that the aircraft climbed to around about 4,000 feet.
26:21The pilot was finding that he was having to put an increasingly strong
26:25backward effort on the control column to raise the nose of the aircraft.
26:29And the aircraft wasn't responding the way that he expected.
26:33The FDR data confirms the pilots were tackling a control problem.
26:38But why?
26:40The captain said they were also applying pitch trim.
26:42Pitch trim moves the tail elevators up and down to maintain the pitch of the aircraft.
26:53Can we take a look at the pitch trim data, please?
26:56Right.
26:56Investigators make a puzzling discovery.
27:03Look at that.
27:05The elevators are trying to get the nose to pitch down instead of up.
27:08After the lightning strike, some unknown force was fighting the pilot's inputs to both the control column and the pitch trim.
27:18It's very difficult to imagine what, let's say, an 80-pound force feels like.
27:25Normal control pressures are much, much lower than that, in the order of sort of 10 to 20 pounds.
27:30So an 80-pound pull is really extraordinary and very difficult to maintain.
27:38Something's wrong.
27:40I can't get the plane to climb.
27:41How's your side?
27:43It's really heavy.
27:46Trim's not doing anything either.
27:48We found that although the pilots were applying a significant nose-up pitch control input by pulling the stick back towards them,
27:56the aircraft was actually trimmed nose down.
27:59Whatever was trimming the pitch control system was effectively overcoming the effort of the pilots.
28:10The crew said the lightning struck, the autopilot disconnected, and then they had control problems.
28:19Right.
28:20Can we take a look at the autopilot data, please?
28:24Finally, the team zeroes in on the answer.
28:29The autopilot was on almost the entire time.
28:34The pilots themselves were very clear in their recollection that it had disengaged.
28:38All of the evidence we had indicated that the autopilot had, in fact, remained engaged.
28:45It's no wonder the pilot had control problems.
28:48The autopilot was said to keep the plane at 2,000 feet.
28:51Right.
28:51And whenever the pilots tried to get the plane to climb, the autopilot would engage and bring the plane back down.
28:56Back to its assigned altitude.
28:59Investigators discover that after the lightning strike, the pilots were in a tug of war with the plane.
29:05I can't get the plane to climb. How's your side?
29:09It's really heavy.
29:12So we then had to look at why did the crew misunderstand the status of the aircraft.
29:19The A.A.I.B. contacts the captain of Flight 6780 to better understand why he thought the autopilot disconnected, when in fact it hadn't.
29:35The Saab 340.
29:36He said he assumed the lightning would disable the autopilot.
29:47The team learns the pilot trained for lightning strikes on another airplane, the Saab 340.
29:53To change from Saab 340 to the Saab 2000, you can say it's like changing from a motorbike to a bus.
30:00All systems are different.
30:03Performance is different.
30:06You're flying a totally different airplane.
30:09During the training on the Saab 340, the commander had experienced a simulated lightning strike to that aircraft, which caused both generators to fail.
30:22And in doing so, would cause the autopilot to disconnect.
30:27And I have control.
30:28So when the lightning strike happened for real, his first thoughts were, the autopilot has failed.
30:37The controls feel really heavy.
30:39I must control the aircraft myself.
30:42And in fact, the lightning strike had had minimal effect on the aircraft.
30:47Would you pull up the control data column again, please?
30:49If the lightning didn't disconnect the autopilot, investigators wonder why it remained engaged for more than two minutes, as the pilots struggled with the controls.
31:00Wouldn't the force applied to the control column and the pitch trim have overridden the autopilot?
31:07Now, in most aircraft, if the pilot intervenes on the controls and tries to apply a force against the autopilot, the autopilot is designed to disengage.
31:21One way of thinking about this is to imagine you're driving down the highway in a car on cruise control, and you're getting close to a car in front of you, so you press the brake.
31:31And what you expect to happen is for the car to slow down.
31:33You don't expect the cruise control to oppose the brake and add more power to maintain 65 miles an hour.
31:41But that's essentially what was happening in this case.
31:45The autopilot was attempting to keep the plane at 2,000 feet, despite all attempts by the crew to climb.
31:53It says here, applying an override force to the column will not cause the autopilot to disengage.
31:58In the Saab 2000, the autopilot would not disconnect when you exert force on the control columns.
32:07It's more.
32:09Pressing the main pitch trim switches also has no effect to cause the autopilot to disengage.
32:14The team is surprised to discover there is no force override for the autopilot in the Saab 2000.
32:25Something's wrong.
32:27I can't get the plane to climb.
32:28One thing the pilot would have done is as he pulled back, feeling the force on the control column,
32:33he would have used the switches on the control column to apply trim in the appropriate way.
32:38How's your side?
32:40It's really heavy.
32:45Trim's not doing anything either.
32:47But when the autopilot's engaged in this model of aircraft, the trim switches are inhibited.
32:53So no matter how much they've selected those trim switches, they were having absolutely no effect.
33:02Investigators soon discover that the Saab 2000 is unique.
33:06Look at that.
33:08It's one of the few planes in existence that doesn't have an autopilot override.
33:14Every plane has an autopilot override function, except for the Saab 2000.
33:23It just had a different design to all the other aircraft we were aware of.
33:28And really to discover that the autopilot had greater authority than the human pilots was a bit of a revelation for us.
33:38It still doesn't explain why the crew didn't know the autopilot was on almost the entire time.
33:44Would there be some sort of indicator in the cockpit?
33:48Yeah.
33:49I'll show you.
33:50Look over here.
33:52When the autopilot is connected, that will be a green AP.
33:58Well, what does the control panel look like when the autopilot goes off?
34:01Like this.
34:02When that autopilot is not connected, it will be a white AP, but the letters AP remain.
34:14That's it.
34:15That's it.
34:15It just goes from green to white.
34:16One could argue whether that visual clue is enough to warn the crew the status of the autopilot.
34:27And I have control.
34:30It's not as if the AP disappears when it's not engaged and appears when it is engaged.
34:35Oh, no.
34:37Come on.
34:38We're dropping.
34:39But all we have here is a colour change between green and white, and that sometimes is very difficult to perceive when you're in a high-stress situation.
34:53Investigators believe that the autopilot visual indication might have been too small for the pilots to see as they struggle to control their plane.
35:01Surely there would have been aural warnings.
35:12Yes, right here.
35:13It says the plane's computer would have sounded a caution chime.
35:16Yeah.
35:17Even if the pilots missed the visual indications for the autopilot, caution chimes would have alerted them when they adjusted the pitch trim.
35:26The captain never said anything about hearing any chimes.
35:29Right.
35:29So what's going on there?
35:31If they are trimming against the autopilot for more than 10 seconds, a chime will announce to say that there is a pitch mistrim situation.
35:50We see from the data that it's highly likely that the alerts would have occurred, but the crew don't recall having heard them.
35:57Nothing's working.
35:58Come on.
35:59Come on.
35:59Come on.
35:59Come on.
35:59Come on.
35:59So why did the pilots of Flight 6780 ignore all warnings telling them that the autopilot was in control?
36:09AAIB investigators have learned that after a lightning strike, the crew of Logan Air Flight 6780 didn't recall hearing audible warnings that the autopilot was engaged and set to maintain 2,000 feet.
36:21Lightning struck the plane.
36:22Lightning struck the plane, and for two and a half minutes, the crew struggled with the controls to get the plane to climb.
36:31Right.
36:32They were so distracted by that, they failed to see what was really going on.
36:37Could the stress have affected their perception of the situation?
36:41You have to bear in mind, of course, this was at night, in turbulent, poor weather, heavy rain, and the lightning strike would have been really quite bright, and the noise would have been alarming.
37:00So it's sort of understandable that their performance was degraded because of the stress situation.
37:09A couple of things happen when we get stressed, we tend to focus on fewer and fewer things, and we tend to not notice the other things, and that can be either visual cues or auditory cues.
37:27So we get what's called cognitive tunneling, and one aspect of that is inattentional deafness, so an alert might occur, but we might not hear it.
37:35It's very difficult for a crew to break the vicious circle of cognitive tunneling, where they're concentrating on one event and not looking at the bigger picture.
37:49The controls feel really heavy.
37:52But if the pilots were suffering from cognitive tunneling, how were they able to regain control of the plane?
37:58OK, look at this.
38:05The AAIB makes one last horrifying discovery.
38:10The only reason the autopilot ever disengaged was because of a random glitch in the plane's computer system.
38:19The reason for the disconnection was that there was a momentary loss of data to the AirData computer, and we know that's one of the conditions that would cause the autopilot to disconnect, and that's what caused it to disconnect in this case.
38:32Had the autopilot disconnected more than seven seconds later, the airplane would have gone into the ocean in a dive at over 300 knots.
38:45This wasn't a fatal accident by pure luck.
38:49Investigators believe they finally understand what caused the terrifying incident on board Logan Air Flight 6780.
39:02While circling away from a bad storm at Sombra Airport.
39:06Roger that.
39:07Well, wait until the storm's up.
39:09The crew is startled and disoriented by a lightning strike.
39:13In a moment of high stress, the captain believes the autopilot has disengaged.
39:21I have control.
39:23When it hasn't.
39:24The autopilot remained engaged and they didn't realise that was the case, so effectively from that point until it disengaged, they were fighting the autopilot.
39:34They wanted to climb, it wanted to descend, and because of the way the flight controls were configured, the autopilot was going to win.
39:40Engaged in a tug-of-war with the aircraft, cognitive tunnelling takes over.
39:47Something's wrong.
39:49I can't get the plane to climb.
39:50How's your side?
39:52The highly stressed pilots don't register the audible warnings telling them that the autopilot is still engaged.
39:58It's really heavy.
40:01Trim's not doing anything either.
40:02The final blow is a one-of-a-kind autopilot system without a force override.
40:10I have every sympathy for crews being startled when something unusual happens, whether there's an explosive engine failure or a lightning strike in this case.
40:18But the training must kick in, and the crew must revert to, in effect, as I say, sit on your hands for a few moments, make an assessment of what's happened, what's gone wrong, what's working, what's not working.
40:32And then deal with the situation from there.
40:35Oh, no! Come on!
40:38We're dropping!
40:43If it wasn't for a split-second fluke error in the computer system and the relentless efforts of the crew...
40:50Speed! Speed!
40:52Flight 6780 would have slammed into the North Sea at 380 miles per hour.
41:02I would say I was a nervous flyer for a couple of years, so I've just kind of gone through the motions of sort of building myself up to knowing that it's going to be fine.
41:12The final report recommends several safety changes to the autopilot system.
41:21We then made recommendations looking at how aircraft could be certified in future to make sure that no future design could be certified where neither operation of the control column nor operation of the pitch control switches would result in disconnection of the autopilot.
41:39For investigators, the lessons of Logan Air 6780 go beyond this one near tragedy.
41:51We can only go so far in educating human operators in how a system works.
41:56Ultimately, we have to recognize that they will behave instinctively, particularly when under stress.
42:01That's the real challenge for the future of automated systems.
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