Embed Size (px)
Citation preview
LOST: THE MYSTERY OF FLIGHT 447Final BBC Master, 21st of May 2009
Alternate Lines Recorded by Tony Stephens Highlighted in GreyReconstruction Captions (5) Shown in Red.
Time Code Sync1. 00:03 The early hours of the 1st of June, 2009.
2. 00:07 Air France Flight 447 from Rio de Janeiro to Paris, makes its final radio transmission.
3. 00:16 Then all contact - is lost.
4. 00:23 Flight 447 has vanished into thin air.
FRENCH OFFICIAL. We wait, we pray, we will know more this afternoon.
5. 00:37 Aviation experts are baffled.
MARTIN ALDER. Why would a well-operated aircraft with a well-trained crew suddenly disappear?
JOHN COX. The thing that we know is that we don’t know.
6. 00:50 The missing aircraft is a state of the art Airbus A330.
7. 00:56 It has never suffered a single passenger fatality.
TONY CABLE – The big question of course is, where is the aircraft?
8. 01:04 5 days later, the shattered wreckage is finally discovered, floating in the Atlantic.
9. 01:11 228 passengers and crew are dead.
10. 01:17 No-one has given a full explanation as to what happened.
11. 01:23 Until now.
12. TITLE LOST: THE MYSTERY OF FLIGHT 447
13. 01:37 One year after Flight 447 was lost, a 28 million Euro, Atlantic search operation has failed to recover the all-important black boxes.
1
14. 01:51 The missing Flight Data and Cockpit Voice Recorders, would provide the only definitive proof of the aircraft’s fate.
TONY CABLE. These have not been found yet, they’re clearly on the bottom with the rest of the wreckage, a very, very big handicap to the investigation.
15. 02:11 The official French investigation is not prepared to make its final report until the black boxes are found.
16. 02:18 Two interim reports set out a tantalising array of known facts, but are unwilling to draw specific conclusions.
With nearly seven hundred A330’s in service worldwide, passenger safety experts are impatient for answers.
JOHN COX. We move basically the population of the planet every three years. We, we just can’t accept unknowns any longer.
17. 02:52 This film brings together an independent team of leading air crash investigators.
Their combined expertise will provide the first credible solution to the mystery of Flight 447.
18. 03:07 With their own tests and simulations, they plan to piece together a convincing accident scenario - from the few clues scattered in the official reports.
19. 03:21 Veteran crash investigator Tony Cable will build a case from just a few fragments of evidence.
TONY CABLE. Any accident is a chain of events and each of the links needs to be in place.
20. 03:32 He will joined by an aviation meteorologist…
JOHN WILLIAMS. We really are limited to using mostly satellite data to understand what’s going on.
21. 03:41 …and a highly respected structural engineer.
JIM WILDEY. You’re going to be forced to just look at whatever recovered pieces of the structure that you have.
2
22. 03:51 Completing the team - 3 expert pilots, specialising in aviation safety.
MARTIN ALDER. It’s very unlikely that one single thing would bring down an aircraft.
PAUL COMTOIS. There’s an unfortunate alignment of many things that cause a problem.
JOHN COX. As you piece it together the weight and significance of each piece of that evidence becomes more and more clear and that’s how you develop the theory that leads to, to the truth.
23. 04:22 The investigation team faces a daunting challenge.
The lost aircraft left hardly a trace behind.
24. 04:38 Tony Cable is a veteran of 32 years in the UK Air Accidents Investigation Branch.
He was a senior investigator on the Concorde crash…
…and the Lockerbie bombing.
25. 04:57 As he kick-starts our independent investigation, he knows physical evidence is limited.
TONY CABLE. The normal way of investigating an accident of course is to look at the crash site and the wreckage. In this case it’s likely there’s only a small amount of floating wreckage.
26. 05:19 5 days after it disappeared, the first wreckage from Flight 447 was found …
...floating 750 miles off the coast of Brazil.
27. 05:32 But most of the aircraft had sunk, two and a half miles down to the ocean floor.
28. 05:40 Tony Cable’s task - to somehow make sense of the few fragments that were recovered.
TONY CABLE. It is possible if you know the wreckage, to work out quite a lot about how it crashed, whether it broke up in the air.
29. 05:54 The first thing to eliminate – the possibility of a terrorist attack.
3
30. TONY CABLE. The possibilities that immediately come to mind would be a bomb or a structural break-up.
31. 06:08 In the hunt for evidence of a mid-air explosion and break-up, Cable is joined by one of the world’s leading aviation safety consultants.
32. 06:18 For John Cox, the key technique is reconstruction.
JOHN COX. Dealing with wreckage is literally a jigsaw puzzle, but you don’t know how many pieces you have and you usually don’t have all of them.
JOHN COX. Are both wings attached to the airplane, is the nose there, is the tail there, the quote, “four corners”?
JOHN COX. You have to take what wreckage you have and reassemble it, so that you can then begin to understand the forces that were acting on the airplane in its last moments of flight.
33. 06:50 A similar jigsaw puzzle was solved in this way when TWA Flight 800 crashed off the coast of New York in 1996.
The aircraft broke apart in mid-air, then large fragments of fuselage floated slowly down to the water, without further major damage.
34. 07:10 The National Transportation Safety Board were able to conclude that a fuel explosion due to faulty wiring was the cause.
35. 07:18 Engineer Jim Wildey was Chief of the investigation’s Materials Lab.
36. 07:27 But with Flight 447, he faces a jigsaw with most of the pieces missing.
JIM WILDEY. In this case there is only a limited amount of structure that’s recovered, it fortunately does tell enough of a story to at least give a clue as to what’s going on with the airplane.
37. 07:43 Two of Flight 447’s four corners were recovered.
Wildey turns first to the nose cone.
JIM WILDEY. If this piece was to come off the airplane and float to the water by itself, it wouldn't be going fast enough so that when it hit the water it would be damaged really in any way.
4
38. 08:06 Instead, the nose cone shows signs of a high speed impact with the water.
JIM WILDEY. What we see here is that this piece has been flattened, it’s been crushed, it’s been torn, and so this is a very clear sign that this piece was on the airplane, when the airplane hit the water.
39. 08:23 It looks like the nose cone only broke off on impact.
40. 08:27 The second jigsaw piece - the tail fin – tells the same story.
41. 08:35 The official report suggests a mid-air break up could not have wrenched it from the fuselage like this.
42. 08:43 Only a massive impact - when the aircraft hit the ocean – would have sufficient force.
43. 08:50 Nose cone and tail fin suggest Flight 447 stayed intact, until it hit the water.
44. 08:57 The last piece of the puzzle – a floor section from the cargo compartment - can even tell Wildey which way the aircraft was pointing as it fell.
WILDEY. What we see here is curvature damage on both sides of this piece, with a fracture down the middle. This damage is consistent with the airplane hitting relatively flat and with very high hydraulic pressure coming up from below and deforming this piece in the manner that is shown here.
45. 09:25 Flight 447 hit the water intact and level.
JIM WILDEY. Whatever the cause of the accident is, it better take into account the fact that this airplane is hitting the water relatively flat at a high rate of speed.
46. 09:41 The first, solid conclusion.
47. 09:44 Flight 447 didn’t explode in mid-air - it simply fell out of the sky.
48. 09:55 But if there was no explosion – then what did happen?
49. 10:03 The investigators turn their attention to the safety of the aircraft itself.
5
50. 10:12 The A330 is a jewel in the crown of European aerospace giant, Airbus.
51. 10:18 With nearly seven hundred in service, there had never been a single passenger fatality before Flight 447.
52. 10:24 This history of reliability rests on a highly computerised flight control system – Fly By Wire.
53. 10:34 The design philosophy - that safety is greatly enhanced by automation.
JOHN COX. They’re highly automated, they’re fly-by-wire, they’re some of the leading edge technology in aviation even today.
MARTIN ALDER. If the pilot were to lose control for some reason the fly-by-wire system would save the aeroplane.CO-PILOT. V1, Rotate.
54. 11:01 Captain Martin Alder is a former chairman of the British Airline Pilots’ Flight Safety Group…
MARTIN ALDER. Gear up.
…and a highly experienced Airbus instructor.
55. 11:13 In the flight simulator, he shows how automation can keep an aircraft under control - even with no help at all from the pilot.
MARTIN ALDER. Well in a conventional aeroplane, instead of this side-stick, I’d have quite a big control column here. You need plenty of leverage to apply the mechanical forces you need to move the control surfaces to control the aeroplane.
56. 11:37 In a conventional aeroplane, the pilot pulls mechanical levers to operate a powered, hydraulic control system.
57. 11:45 But with Fly By Wire, the heavyweight gear is replaced by electronics.
58. 11:50 Now a flight computer carries out the pilot’s wishes.
59. 11:56 The computer keeps the aircraft under precision control during any manoeuvre - even a simple turn.
6
60. MARTIN ALDER. So if I want to go to the left, stick to the left. Round to the left.
61. 12:13 The Flight Computer adjusts the wing, and the aircraft rolls to the left.
62. 12:21 Ordinarily, this would cause the A330 to descend.So the computer compensates by increasing engine thrust and pitching the nose up to maintain a steady altitude.
The end result - totally automatic control.
MARTIN ALDER. I take my hands off, and there we are, it’s flying round, vertical speed zero, 25 degrees of bank, 240 knots. It’s going to fly around at 25 degrees of bank, and keep doing this until we get bored.
When auto-pilot is switched on, the plane literally flies itself.
MARTIN ALDER. Ninety-nine percent of the time when you’re sitting as a passenger flying at thirty-five thousand feet, the auto-pilot’s flying the aeroplane.
63. 13:12 CAPTION: RECONSTRUCTION
64. 13:13 Flight 447 would have been safely on auto-pilot as it headed out over the Atlantic.
65. 13:21 The pilots, settling in for the long haul…
…the aircraft, making continuous automatic adjustments…
…to keep them on course for Paris.
66. 13:42 Tony Cable tracks their progress…
…using Air Traffic Control transcripts.
TONY CABLE. The only thing to go on in this case in the early stage is to look at the last position report, which in this case is the last crew conversation with Air Traffic Control.
67. 14:03 Three hours out from Rio de Janeiro, Flight 447 was still on the intended flight path.
7
68. 14.11 CO-PILOT. AIR FRANCE FOUR FOUR SEVEN, by checking INTOL zero one three three, level three five zero, SALPU zero one four eight, next ORARO zero two zero zero, Selcall check Charlie Papa Hotel Quebec.
But at 1:35 a.m., all radio communications - ceased.
TONY CABLE. There is nothing to say what’s happened to it after that last position report.
69. 14:40 The last known position, 350 miles off the coast of Brazil.
70. 14:49 But now, the mystery deepens.
71. 14:52 For another thirty five minutes, Flight 447’s computer continues to send out automatic position reports, by satellite.
TONY CABLE. The reason for the automatic position reports is so that the operator can follow the progress of the flight and know whether it’s going to be early or late, to help with its scheduling effectively.
72. 15:15 Cable uses the automatic reports to track the flight’s further progress.
73. 15:24 The last location was at 02:10 am, 70 miles from where the wreckage was discovered. TONY CABLE. What the messages do show is a last automatic position report and then apparently the end of the flight.
74. 15:40 Something in Flight 447’s path brought it down.
Cable hunts for the cause…
…in the official weather report.
TONY CABLE. There was thunderstorm activity in that area, quite a large trail across the flight path at the time that AF447 went through.
75. 16:08 At 2:10 am, Flight 447 was in the vicinity of an Atlantic thunderstorm – 250 miles wide.
76. 16:22 But this fact raises a crucial question - that the official reports fail to answer.
8
77. 16:28 Why would experienced pilots - fly into a storm?
JOHN COX. The idea that a pilot would fly through a thunderstorm, absolutely not.
MARTIN ALDER. Highly improbable. Pilots, remember, are at the front end of the aeroplane, the first people to meet any accident, we have a great incentive not to meet accidents.
78. 16:50 Flight 447 must have flown into the storm by mistake.
79. 16:59 To find out why this happened, the investigation turns to John Williams.
…a specialist in aviation meteorology…
…at the National Center for Atmospheric Research in Boulder, Colorado.
80. 17:13 Williams has satellite images taken every half hour, to analyse how the storm developed as Flight 447 approached.
JOHN WILLIAMS. I’ll step through by thirty minute intervals and you’ll see these storm systems starting to grow.
JOHN WILLIAMS. This storm system is hundreds of miles across and maybe sixty miles wide.
JOHN WILLIAMS. Wow, look at the size of that growth right there.
81. 17:42 In daylight, the thunderclouds would have spanned the horizon, towering from the ocean to 50 000 feet.
82. 17:52 But in the dark, early hours of the morning, the Flight 447 pilots can’t see them.
83. 18:00 Instead, they must rely on their on-board weather radar.
84. 18:05 Radar waves reflect from water droplets in the clouds…
…allowing pilots to pick their way around any dangerous storms.
85. 18:19 According to the official reports, several other flights that night took the same route as Flight 447.
9
86. 18:26 But all these pilots saw the storm coming, and made detours of up to 90 miles to avoid it.
87. 18:35 But Flight 447 made only a minor change of course.
JOHN WILLIAMS. You can see that it had deviated a little bit off of its flight plan and that might mean that they were trying to deviate around some storms.
88. 18:49 This minor deviation leads Williams to a major breakthrough.
89. 18:54 He thinks Flight 447 was deceived - by a quirk of the weather.
JOHN WILLIAMS. What you can see is that there is a small storm between them and the large storm system, that as they approached it may have blocked their radar’s view of the larger storm system and the more hazardous storm system behind.
90. 19:16 If Williams is right, Flight 447’s radar was blocked by the smaller storm in their path.
91. 19:25 The beam can’t get through to detect the real threat……the 250 mile wide storm system behind.
92. 19:37 Supporting Williams’ theory, another flight crew that night reported that they only saw the danger when they increased radar sensitivity.MARTIN ALDER. You could find yourself in a position with this, with this absorption of the signal, where you, you, you are almost into the storm before the, the signal strength actually reflects the reality.
93. 19:58 It’s an important step in the investigation – filling a critical gap in the official reports.
94. 20:06 It’s possible that by the time Flight 447 saw the danger on radar - it was already too late to turn around.
MARTIN ALDER. You have no option but to take the least worst exit.
95. 20:22 The crew must ride out the storm.
96. They face two potential threats.
10
97. The first – lightning.
98. 20:42 Aircraft are struck once a year on average.
But modern airliners are protected against even the most severe lightning.
99. 20:56 This Boeing 747 incident was captured on a mobile phone.
100. 21:07 Spectacular – but the lightning passes harmlessly through the outer skin.
The 747 landed safely, with no significant damage.
101. 21:20 No modern airliner has been lost to lightning since 1963.
JOHN COX. The thought that lightning could have a, be a serious effect in the, in the accident of Air France 447 is extraordinarily remote, and there’s absolutely no evidence of it.
102. 21:45 The second threat – turbulence – is more serious.
103. 21:52 It’s caused by up-draughts…
…rising pockets of air, punching up through the storm towards Flight 447’s altitude.
The white areas, on John Williams’ map.
JOHN WILLIAMS. There’s one here and one here, just off the flight track of Air France 447.
JOHN WILLIAMS. Hitting an up-draught would be like a jack-hammer hitting you from below, it could really give the aircraft a jolt.
104. 22:14 CAPTION: RECONSTRUCTION
105. 22:17 As Flight 447 headed for turbulence, the automatic systems would have kept everything under control.
The pilot’s next move is standard procedure.
106. 22:30 Anticipating turbulence, he asks the passengers to fasten seatbelts.
11
107. 22:37 Then, as a safety measure, he dials in a slightly lower speed, to reduce the stresses on the aircraft.
108. 22:46 An automatic system called auto-thrust takes over.
MARTIN ALDER. The auto-thrust would reduce the power on the engines to slow down towards your target speed.
109. 23:02 Everything happens automatically.
So the pilot’s manual thrust levers…don’t move.
As turbulence hits, sudden up-draughts throw the aircraft up and down.
110. 23:18 But auto-thrust changes the engine power to compensate - maintaining the aircraft in a safe speed range.
111. 23:25 All the pilots have to do is monitor the instruments.
MARTIN ALDER. The systems automatically will tell you if they get out of limits, but you could be looking at the systems from time to time, just to check that they are well inside limits.
112. 23:40 The investigation has traced Flight 447’s progress to its last known position.
113. 23:47 They’re in the midst of a rapidly developing storm…
…that their radar detected too late.
114. 23:55 The pilots have no option but to ride out the turbulence.
But their automatic systems provide reassuring protection.
115. 24:06 It’s 2.10 am.
The evidence suggests that little more than four minutes later - everyone on board Flight 447 was dead.
116. 24:23 Automation gives the investigators a crucial window on what happened next.
117. Just after 2.10 am, the flight computer suddenly sent a torrent of automatic fault messages, to Air France in Paris.
12
118. 24:47 These so-called ACARS messages now form the central focus of the investigation.MARTIN ALDER. It really is the last Will and Testament of the aircraft.
119. 24:59 Flight 447 suffered 24 critical faults in just 4 minutes and 16 seconds.
MARTIN ALDER. You can just see an aircraft almost dying in front of you.
120. 25:11 The tantalising, cryptic messages are the only evidence that can cast light on Flight 447’s final moments.
TONY CABLE. As the last message from the aircraft, they may well tell a very great deal about what happened.
121. 25:26 Tony Cable decodes the data, to reconstruct events on a second by second basis
TONY CABLE. The first ACARS message that appears is auto-pilot off, and that indicates that the auto-pilot has disengaged on its own.
TONY CABLE. There is a master audio warning, which is a real attention getter.
122. 26:00 The pilot must re-take manual control.
123. 26:05 But now another critical message…
… Auto-Thrust Off.
TONY CABLE. It means that the system that normally automatically controls engine thrust to maintain air speed and altitude is no longer working.
124. 26:21 The alarms keep coming.
125. 26:28 The most critical safety features are failing - one by one.
TONY CABLE. It must have been a very busy and confusing situation on the flight deck.
126. 26:40 The automatic systems…are shutting down.
13
127. 26:47 Then - one final, ominous message.
TONY CABLE. The Advisory Cabin Vertical Speed message means that the pressurised cabin is descending at a high rate, in other words the aircraft is descending at a high rate.
128. 27:03 The last message came just moments before Flight 447 and its passengers hit the water.
129. 27:13 But what could have caused all the vital automatic systems to suddenly malfunction?
TONY CABLE. The reason for the auto-pilot kicking out is something that clearly needs to be established.
130. 27:30 Tony Cable scans the ACARS Messages, in search of the root cause.
131. 27:37 And he thinks the multiplying faults…
…can be traced to just one.
TONY CABLE. Pitot probe messages are particularly significant, it’s a very basic parameter for the aircraft.
132. 27:55 If Cable is right, this single, cryptic message means the automatic systems can no longer function –
…because the flight computer doesn’t know its most vital parameter.
Its airspeed.
133. 28:12 All airliners measure airspeed using pitot probes.
Forward facing, hollow tubes of metal, just below the cockpit.
In case of failure, there are three probes of identical design.
A supposedly fail-safe system – because the automatic systems can’t operate without them.
134. 28:36 But on Flight 447, the crucial pitot probe message says something went wrong.
14
135. JOHN COX. We know that the air speed indication systems, all three of them, were compromised. But how? Overcome by a sudden snap-freeze of pure supercooled water only to be found over oceans? – or a slow accumulation of the ice crystals that are to be found in relatively smooth-flying CirroStratus and CirroCumulus (i.e. high-level clouds that are made up solely of ice crystals)? These clouds can be quite dense but present little by way of turbulence/no hail / no lightning etc). Cs and Cc clouds can be found around storm cells – projecting extensively in all directions. It was in this type of cloud that most (if not all) of the prior Thales pitot incidents happened.
136. 29:01 Tony Cable plans to find out why this most critical of aircraft sensors…failed.
In the wind tunnel.
TONY CABLE. OK Cliff, can you take it up to, 30 knots we’ll try this time?
137. 29:17 A pitot tube measures the pressure of the air rushing into its open end.
The computer converts this pressure into a wind speed.
In this case – around 30 knots.
TONY CABLE. And now?
138. 29:35 But Cable can make the pitot tube malfunction - by just blocking the end.The measured airspeed drops to almost nothing.
TONY CABLE. Gone to zero? OK.
139. 29:48 At high altitude, the most likely way a pitot tube could get blocked – is by ice.
MARTIN ALDER. The pitot tube sticking out into the airstream means that it’s vulnerable to being hit by ice and rain. It’s a small device, small things pick up ice quicker than big things, so the pitot tube is a prime candidate for picking up icing.
15
140. 30:14 For this reason, the pitot tubes have a powerful heating element…
….supposedly able to handle any conditions an aircraft could encounter at altitude.
141. 30:29 But as the accident investigation reports concede, scientific knowledge of the conditions Flight 447 flew into…
…a storm at 35 000 feet, are worryingly incomplete.
142. 30:49 Did Flight 447’s pitot tubes meet a situation they were not designed to handle?
143. 31:03 Back at the National Center for Atmospheric Research in Colorado…
…meteorologist John Williams aims to calculates the actual weather conditions in Flight 447’s path.
JOHN WILLIAMS. One of the, the things that we’re interested in is what were the conditions at thirty-five thousand feet, what kind of ice or liquid was there at that altitude?
144. 31:30 Williams can work out the precise conditions at Flight 447’s altitude.
JOHN WILLIAMS. One of the first things we want to do is try to figure out what the temperatures were at that level.
145. 31:42 He creates a cross section, showing the temperature at different altitudes.
JOHN WILLIAMS. What it shows, starting at the surface and going up to the top of the atmosphere, they were flying at this level here and you can see that the temperatures were about forty below Celsius at the time and location of the accident.
146. 32:04 Minus 40 Celsius may seem extremely cold - but in fact it’s much warmer than is usual at 35 000 feet.
And, Williams thinks, just right for a highly unusual phenomenon.
JOHN WILLIAMS. What we’ve found out from this analysis is that it’s possible that there was super-cooled liquid water at the altitude of the aircraft.
16
147. 32:28 Super-cooled water is a strange quirk of physics.
148. 32:32 In 32 years’ experience, Tony Cable has never seen it up close.
149. 32:40 The water in these bottles is well below zero – the normal freezing point.
150. 32:50 But it’s still liquid.
151. 32:55 Ice crystals can only grow around tiny particles - and this water is extremely pure.
152. 33:04 But if Cable inserts a metal tube…
153. TONY CABLE. Hey!
154. 33:11 Instant, solid ice.
TONY CABLE. That is incredible.
JOHN WILLIAMS. The fact that air is really clean over the oceans suggests that if there is super-cooled liquid water in the atmosphere and an aircraft flies through that, those little droplets are ready to freeze as soon as they hit a surface.
155. 33:38 When hit by super-cooled water…
…a pitot tube could freeze in seconds.
MARTIN ALDER. It is possible that the aircraft encountered conditions which were more severe than those to which it had been designed. The pitot heads may not have been sufficient to cope with these severe conditions.
156. 34:02 The official reports agree that more research is required into super-cooled water at high altitude.
157. 34:12 And Tony Cable discovers that Flight 447 wasn’t an isolated pitot tube incident.
158. 34:18 A catalogue of failure has since come to light.
159. 34:24 From 2003, thirty-six frozen pitot tube incidents, involving A330s or the similar A340s.
17
160. 34:34 And in 2009, they were coming thick and fast.
TONY CABLE. It was in the order of one a week for getting on for two months in the period leading up to the 1st of June.
161. 34:43 All the failed pitot tubes met existing safety standards. But in late 2007, Airbus recommended a refit of all A330s, with uprated pitots.
162. 34:54 CAPTION: RECONSTRUCTION
163. 34:54 Air France was in the process of upgrading its entire fleet - when Flight 447 ran into the Atlantic storm…
164. 35:03 …still with old-model pitots.
165. 34:43ALT
All the failed pitot tubes met existing safety standards. But in late 2007, Airbus recommended a refit of all A330s, with upgraded pitots.
166. 34:54 Air France was in the process of refitting its entire fleet - when Flight 447 ran into the Atlantic storm…
167. 35:03 …still with old-model pitots.
168. 35:11 Our independent team believes they may have encountered super-cooled water..
…causing the pitot tubes to freeze.
169. 35:28 With no airspeed data, Flight 447’s automatic systems collapse
one…
by one…
by one.
170. 35:40 In total darkness, and heavy turbulence, the crew are forced to retake manual control.
JOHN COX. Pilots are the last line of defence, so when things go very wrong the last line of defence is the aviator.
18
171. 36:09 After more than 3 hours on auto-pilot, the pilots are suddenly faced by information overload.
JOHN COX. That crew faced an almost unheard of series of failures, one right behind the other, and for them to sort through it would have been very difficult that night.
JOHN COX. Why is the airplane doing what it’s doing, what are all these failures, why are they all coming at one time?
172. 36:22 Bombarded by faults – the pilot must cope with the most serious problem of all.
He must maintain speed - or they will go out of control.
MARTIN ALDER. The acceleration forces caused by the turbulence means that we might stall the aircraft.
173. 36:40 If Flight 447 slows down by just a few knots, it could go into the catastrophic condition known as a stall.
174. 36:56 Back in the wind tunnel - Tony Cable demonstrates how an aircraft’s wing can cease to function.
TONY CABLE. OK Cliff, you ready to go?
175. 37:06 An aircraft is kept aloft by smooth, streamlined airflow over the wings.
176. 37:14 If the aircraft slows down, the angle of the wing must be increased to maintain lift.
177. 37:21 But too slow, and there’s a critical angle, where the airflow breaks up.
JOHN COX. If you disrupt that flow the wing cannot produce lift. And that’s really all a stall is, is it’s a disruption of the air flow across the top of the wing.
TONY CABLE. If it slows down there’s a tendency for the nose to come up and at a fairly shallow angle the wings will stall, the air flow breaks down, there’s a loss of lift and the aircraft begins to descend.
19
178. 37:53 Stalled wings would mean a dramatic, uncontrolled descent.
At 35 000 feet, in heavy turbulence, even a very small reduction in speed would increase the risk.
MARTIN ALDER. Our speed range is quite limited. Typically it could be ten knots either side of the cruise speed.
179. 38:18 The pilots must somehow avoid slowing down - by even ten knots.
The only trouble is…
…with their pitot probes frozen..
– they have no way of knowing how fast they’re going.
JOHN COX. The ability for the crew to recognise if they were at the proper speed is going to be a much more complex problem now.
180. 38:46 A complex problem – but can it be solved?
181. 39:00 In the simulator, Martin Alder plans to recreate the known technical failures on Flight 447.
182. 39:10 Two experienced pilot instructors will attempt to maintain speed and avoid the stall - using standard operating procedure.
183. 39:24 Like Flight 447, they are cruising normally at 35 000 feet, at night, over the ocean.
184. 39:33 Alder triggers the storm.
MARTIN ALDER. Storm control. I like the look of that one, so now, activating…
185. 39:42 Thunderclouds loom ahead on the pilots’ radar.
CO-PILOT. Probably a line of thunderstorms…
186. 39:50 The Captain plans a detour, and prepares for turbulence.
CAPTAIN. So Turbulence Airspeed then, I’m selecting decimal seven six.
CO-PILOT. Check.
20
187. 40:02 As was likely on Flight 447, the pilot selects a slightly lower speed, to reduce stresses on the aircraft.
188. 40:11 Auto-Thrust automatically reduces engine power.
CAPTAIN. Hi Ladies and Gentlemen, the Captain speaking, we are just approaching an area where there are a few rain showers around, we’ve got the Seatbelts sign on for approximately ten minutes or so.
189. 40:28 As they edge around the storm, Alder triggers the critical moment of Flight 447…
190. 40:36 He fails the airspeed indicators.
191. ALT He fails all three airspeed indicators.
CO-PILOT. OK we have Nav ADR One disagree. We have unreliable airspeed.
192. 40:51 The automatic systems shut down.
CO-PILOT. We’re flying with no auto-pilot, or auto-thrust.
CAPTAIN. OK. Auto-pilot’s off, I have control.
CO-PILOT. You have control.
193. 41:03 If their airspeed drops by as little as 10 knots, they could stall - and fall out of the sky.
But the Captain relies on established standard procedure.
194. 41:16 He pushes the throttle levers - to set thrust at exactly 85%
CAPTAIN. And I’m selecting - I’ve got 85% set.
21
195. 41:30 Then, he raises the elevators…
…to pitch the nose up, at precisely 5 degrees.
With 85% power, and 5 degrees pitch up, they should always settle at the same safe speed.
MARTIN ALDER. It’s quite possible to fly the aircraft to actually quite high standards of accuracy, something in the region of about five knots or so of the, of the desired target speed would be quite achievable for most crews.
196. 42:02 Pitch and Power is the pilots’ lifeline.
They ignore any fault messages until they’re safely in control.
CAPTAIN. I’ve got 5 degrees on the standby, 4 degrees on the other.
MARTIN ALDER. Flying the aeroplane is the prime objective. No matter how attractive the messages might be to anybody on the flight deck, you both concentrate in ensuring that the person who should be flying the aeroplane is flying it, and flying it in the manner which is safe.
CAPTAIN. OK, so we’ve got what I think is basic control of the attitude, we’re bumping a little bit with the weather, but generally that’s safe.
197. 42:46 Maintaining Pitch and Power will get them to the nearest airport.
The storm has passed…
…the emergency is over.
MARTIN ALDER. That’s it, it’s finished.
198. 43:03 Martin Alder’s simulation shows that speed can be maintained even if all 3 pitot probes fail.
199. 43:03ALT
Martin Alder’s simulation shows that speed can be maintained even if the pitot probes fail.
200. 43:15 But was this standard pitch and power technique applied by the crew of Flight 447? And why didn’t they recover control?
22
201. 43:24 The official reports have no direct evidence….
… but former Airbus pilot John Cox identifies a crucial detail in the standard procedures.
JOHN COX. If they were just entering an area of choppy air, they may very well have been slowing the airplane down.
202. 43:40 CAPTION: RECONSTRUCTION
203. 43:42 When Flight 447 first entered the storm, they would reduce speed….
204. 43:50 … so auto-thrust decreases engine power automatically.
But it does not give the pilots an important visual signal. JOHN COX. The thrust levers themselves, the throttles, don’t move. Unlike some other airplanes where you can feel the throttle in your hand moving, with Airbus aircraft that throttle doesn’t move with auto-thrust engaged, so you have to look at specific engine power indications.
205. 44:18 The power indications are displayed here, on the central control panel.
But in John Cox’s scenario, the pilot doesn’t notice it.
JOHN COX. If you’re very task-saturated your concentration’s going to be directly in front of you. What’s the power output of the engines, you’re going to have to physically turn your attention and look to the centre console area.
JOHN COX. This is not going to be done as frequently as looking at, at the things right in front of you, it, it’s certainly going to be in the scan, the question is how often?
206. 44:58 Overloaded by fault warnings - the pilot overlooks the low power indication.
JOHN COX. Was this crew one that was very attentive and picked up this information very early, were they very slow to pick up the information? We don’t know.
JOHN COX. Were the demands so high that they were unable to, to keep up with it? We don’t know.
23
207. 45:23 Only Flight 447’s black boxes could provide conclusive evidence.
But now, Tony Cable discovers a worrying pattern, to support Cox’s theory.
208. 45:39 In 10 previous incidents of airspeed failure, the crews failed to increase thrust immediately.
TONY CABLE. In quite a number of them, it’s clear that the crews were very slow to get onto manual throttle operation.
209. 46:00 In 5 cases, crews did not take manual control of thrust for more than sixty seconds.
For Flight 447, that would spell rapid deceleration…
…and the risk of a sudden stall.
MARTIN ALDER. Ten to fifteen knots would not be unusual, if you decelerate at a knot a second it’s fifteen seconds. The aircraft would slow down to a much lower speed, and you could approach a stall quite quickly in that manner at altitude.
JOHN COX. There is a good possibility that at some point in the last four minutes that there was a stall event.
210. 46:39 A sudden and critical loss of lift from the wings.
But even in a stall, the aircraft can be saved.
Tony Cable explains the standard recovery technique.
TONY CABLE. The procedure is full thrust on both engines, reduce the pitch attitude and the aircraft will then resume normal flight.
211. 47:06 By pitching the nose down, the pilot restores smooth airflow over the wings, and escapes the stall.
212. 47:18 But Flight 447’s pilots may have found themselves - in totally unknown territory.
24
213. 47:14ALT
But a stall can be an extreme event. Flight 447’s pilots may have found themselves - in totally unknown territory.
JOHN COX. If they were in a condition that it fully stalled, oftentimes when the nose breaks they’ll roll off on a wing and, and that’s a, that’s a pretty aggressive manoeuvre when the airplane does that.
214. 47:39 If one wing stalls before the other, the aircraft rolls violently to one side...
215. 47:45 …more like a fighter jet than a passenger airliner.
216. 47:54 To recover from this stall, the Flight 447 pilot would require highly specialised skills.
217. 48:10 This is the National Aerospace Training and Research Center, in Pennsylvania.
218. 48:19 At the controls of his advanced simulator is Colonel Paul Comtois – a former US Air Force F16 Fighter Pilot.
He believes that taking an aircraft to the extremes is a skill that only comes from direct experience.
PAUL COMTOIS. We don’t fly around on auto-pilot a lot, we have a lot of, you know, hands-on stick time.
PAUL COMTOIS. Not only does it give you the experience to fly in that extreme manoeuvring envelope, it gives you the confidence to be able to do it as well.
219. 48:54 The simulator has the cockpit controls of a passenger airliner.
220. 49:00 But unlike conventional simulators, it moves like a fighter jet…
…spinning on three axes, to take pilots to the limits of human physiology.
PAUL COMTOIS. You learn not to believe your body, because your body will lie to you.
25
221. 49:17 Comtois is flying in the dark – with no visual cues from the outside world. Instead, he must rely on his instruments.
PAUL COMTOIS. I have flown on missions where I felt like I was in a hundred and twenty degrees of bank but I'm looking at that gauge and it’s telling me I'm flying straight and level.
222. 49:37 Instructor Glenn King is about to trigger a violent manoeuvre…
…like the stall that may have hit Flight 447.
GLENN KING. OK here comes a very high degree 40 degree pitch up – 50 degree pitch up attitude – the aircraft is rolling.
223. 49:51 The simulator sends Comtois into a head-spinning roll at 35 000 feet.
224. PAUL COMTOIS. You, you’ve got to unstall the airplane. The nose must go down.
225. 50:04 He has to get the air flowing over his wings.
By ignoring his own senses, and trusting the instruments.
PAUL COMTOIS. It’s a mental battle, because yes I am flying on that gauge but man, I don’t feel right.
226. 50:20 He’s regaining control – but the ground’s still coming up fast.
PAUL COMTOIS. I've got to be very careful for how much I pull back on that stick.
26
227. 50:30
The danger - he might stall again, as he tries to pull up.
GLENN KING. OK he started his recovery – you can hear the buffeting now, from the plane being loaded.
PAUL COMTOIS. You see how fast it is.
GLENN KING. That aircraft’s trying to G-load, starting to load up the Gs, the airspeed is very high.
GLENN KING. Recover, Paul.
PAUL COMTOIS. Phew!
GLENN KING. That’s a lot of altitude. And he’s flying again.
228. 51:04 Comtois finally recovers control.
But despite years of jet fighter experience - the Air Force Colonel lost 19 000 feet.
More than half his altitude in just 45 seconds.
229. 51:19 CAPTION: RECONSTRUCTION
230. 51:22 Most airline pilots have no such experience.
231. And Auto-pilot means they do little hands-on flying.
232. For Tony Cable, the case of Flight 447 highlights critical training issues.
TONY CABLE. It has raised the question, about whether the situation is actually being made worse by the increase in automation, whereby crews don’t get a great deal of opportunity to manually fly the aircraft.
233. 52:02 Paul Comtois agrees.
PAUL COMTOIS. The more we automate, the more we need to get back to the basics of flying. You know, when, when I'm flying that fighter to the edges I am physically hands-on with stick and throttle.
27
234. 52:21 Standard airline flight simulators don’t have the freedom of movement to recreate extreme manoeuvres.
MARTIN ALDER. Stalling is not something actually that’s taught to transport category aeroplane pilots. MARTIN ALDER. We’ve gone from pilots who’ve had experience of some of the more extreme manoeuvres, to pilots who very rarely see them.
235. 52:49 But the wreckage of Flight 447 suggests the pilots may have come close to saving their passengers’ lives.
JOHN COX. We know that based on the impact damage, that the airplane was nose-up, pretty close to wings level, with a high vertical sink rate when it hit the water.
236. 53:08 Did they somehow manage to get upright and level - before running out of time?
237. 53:19 Without further evidence - this is one question the investigators can’t answer.
238. 53:33 A year after the accident, the search for Flight 447’s black boxes continues.
239. 53:40 This is what the official investigation is looking for...
240. …but Flight 447’s black boxes stopped transmitting location signals after one month.
241. 53:56 They’re still lost - in an underwater mountain range, two and a half miles deep.
JOHN COX. The only way that we’re going to find complete and total understanding of what happened to that airplane is if we’re fortunate enough to get the cockpit voice recorder and digital flight data recorder.
242. 54:15 If the black boxes are recovered, they’re likely to prove there was no single cause for the accident.
MARTIN ALDER. In any of these accidents they are chains of unusual circumstances and it only requires one of those links in that chain to be broken, to prevent it happening again.
28
243. 54:33 From the existing, limited evidence, our independent team has linked together the possible chain of events. No single link is fatal in itself.
But together – they provide the most convincing solution so far to the mystery of Flight 447.
244. 54:56 Just before 2:10 am, Flight 447 flew into a 250 mile wide Atlantic storm.
A possible reason – it was hidden from the aircraft’s radar by a smaller storm.
MARTIN ALDER. We believe that the aircraft was probably in an area of turbulence, which would have been challenging to fly.
245. 55:20 The next link in the chain….
The storm clouds contained a rare form of water.
JOHN WILLIAMS. What’s possibly unusual in this storm is to have super-cooled liquid water this high up in the atmosphere.
246. 55:36 Then - another unforeseen event.
Flight 447’s pitot probes develop a problem.
247. ALT All 3 of Flight 447’s vital pitot probes - froze.
248. TONY CABLE. There is little doubt that the air speed systems failed in some fashion, probably due to icing, and that the aircraft went out of control from that point.
249. 55:58 The automatic flight systems failed….
..forcing the pilots to take back control.
JOHN COX. They were faced with multiple warnings, multiple system failures, at night, over water, unbelievably challenging environment.
29
250. 56:12 In similar, previous incidents, pilots did not take control of the vital thrust levers - as is standard procedure.
TONY CABLE. Crews can be very slow to get on to operating the throttles manually, which is very essential of course to maintain a decent air speed.
251. 56:35 If they lost too much airspeed, the potential high altitude stall would have been far beyond most airline pilots’ experience.
PAUL COMTOIS. If you’ve never been there and you don’t know what to expect, the results are going to be disastrous.
252. 56:50 But in the final struggle, it’s possible that the crew almost saved their passengers….
…before a second, and this time terminal stall.
JOHN COX. They were not successful in surviving the event.
253. 57:07 A compelling theory, based firmly on the available evidence.
But until the black boxes and their vital data are recovered, there can be no definitive proof.
Aviation experts will continue to be troubled…
JOHN COX. We do need to solve it, aviation does not do well with unsolved mysteries. We need to understand what happened that night out over the Atlantic.
254. 57:39 CREDITS
255. 58:09 END
30
