AF447 [Archive] - Page 12

surplus1

2nd Jul 2009, 21:41

The mystery continues to grow and the plot thickens.

We now have the much awaited Preliminary Report. You’ve all read it and so have I. It refines some information that we already knew, and introduces a new opinion that most of us did not seem to share before its release. The Board conjectures that the aircraft did not break up in flight but struck the ocean in a level attitude and right side up. That may be nice to know but it does not answer the question that we are all asking: Why did the crew lose control of this aircraft?

The evidence of compression is significant but it does not actually tell us if the entire aircraft stuck the surface at the same time, or perhaps only major sections of its structure, or if that actually occurred at all. Was it in one piece; two; three? No one knows.

As may have been anticipated, some of us are eager to embrace this new theory of belly impact, in what is assumed to be one piece, as factual; others, like me, remain skeptical.

While the Board has better data than we do, they do not have enough data to reach any definitive conclusions. Thus, they have been forced to form some opinions based on what little evidence they do have. What they have issued is an educated guess – an opinion – nothing more. We should all recognize that truth for the reality that it is.

Let us not forget that all AI Boards are composed of a number of committees whose membership includes a cross section of the “interested parties”. I do not question their integrity but neither do I ignore their humanity nor their often divergent agendas. We cannot ignore that potentially hundreds of millions of dollars may be at stake and dependent upon the final outcome of this investigation. I do not intend to infer conspiracy; I merely state the obvious.

Whatever the case, their renderings are always an opinion – including the final report – reached by consensus or majority vote. Keep that in mind as you think about what they have said so far at this early stage of the inquiry, as well as what they may say in the future.

The objective of all investigations is to determine within our capability – what happened. But, the true purpose of the investigation is to prevent a future recurrence of the event.

If we are to achieve the purpose, we must determine the factual cause beyond all reasonable doubt. Preliminary opinions are of little consequence; only those opinions supported by definitive facts are relevant. In that context it does not really matter whether this particular aircraft broke up in flight or struck the surface while intact. Whichever of these two things may have occurred, neither one of them is the cause of this accident. Each of them is no more than an after effect – a consequence of the cause.

What does matter is that control of this aircraft was lost while in flight. The crew most certainly did not land in the water - whether in one piece or fifty - because they had a penchant for boating. At this point in time that is all that we, including the BEA, actually know to be factual. The consequence of that loss of control was a fatal crash in which 228 souls lost their lives. The true cause of that loss of control is what the Board must ultimately determine. The rest is educated guess + not so educated guess.

Unfortunately, the location of the accident severely limits the data available to the investigators. If the recorders should not be recovered intact, this mystery will remain unsolved. Fate is the Hunter.

ECAM_Actions

2nd Jul 2009, 21:53

I find it sad with todays technology that the control centres along the route had no idea what was going on. I'm glad that I now operate in areas of good communication & radar coverage. There is no excuse......apart from penny pinching.Actually, "they" are looking, only "they" won't admit it. :ugh:

Do you really think the US *only* used satellites to "help" discover the crash site? That's no different to flying high over the area and using a pair of binoculars.

Think about it...

ECAM Actions.

Squawk_ident

2nd Jul 2009, 21:59

OK now we know this :
(Page 23 of the English report).
F-GZCP was programmed to automatically transmit its position approximately every ten minutes.

The crash likely occured within 10 minutes after the last position received.
So the -CP was right on track before the end of ACARS reception nearby TASIL. It's important because on French France2 TV an AF pilot came to speak about this report. The journalist asked him what was she doing there, but the captain could not answer because we can't know he said. All of us have read the IB/AF/LH crew comments on what was their experiences this night with diversions, either to West or East or both ways (AF459) with weather radar set to 160NM max. Following or previous aircraft started deviations well before TASIL around ORARO or even before to join the track only by/abeam ASEBA. I would be very interested to have the ACARS track of the 459 just to have a comparative idea.

Another matter is the very poor coordination between all the en-route sectors, Oceanic or not. I have a question about this.

Page 62 we can read

The aircraft's crew must establish contact with the receiving sector's controller (SAL) five minutes before passing above the control transfer point. However, for aircraft flying towards the north and those flying towards the east, the crews must contact the receiving sector ten minutes before the control transfer point to get a transponder code. This contact does not constitute a transfer of the control of the aircraft.

Can anyone confirm that SAL Control still have a working Radar? The 447 was supposed to be at POMAT at 0343 to get its squawk. even with no squawk allocated, the fact that no primary echo was detected would have been a matter to immediately start an emergency procedure.

Madbob

2nd Jul 2009, 22:05

I've followed this thread from the start but this is my first post and there have been many many well argued and articulated posts which I have followed closely.

The question which still puzzles me is why were there no voice tansmissions received by other a/c within VHF radio range of AF447? VHF ought to be good for range up to 100 NMs and there have been reports of other ac flying similar tracks to AF447 which were closer than that. Was no one monitoring 121.5?

If as now seems likely the ac remained substantially intact from cruising alt to SL the ROD can't have been that great so the crew ought to have had time to get out a distress call. Can anyone explain the lack of RT?

MB

falconer1

2nd Jul 2009, 22:09

surplus1 wrote

If we are to achieve the purpose, we must determine the factual cause beyond all reasonable doubt.

no, "beyond all reasonable doubt" is not possible in a lot of cases, and may not be possible in this case..

however, there is a lot of information already available in regards to the "most likely" cause of this accident, and that with a very high probability will be, that an aircraft had most probably encountered extreme weather and control over the aircraft most probably because of this extreme weather had been lost..

it is of secondary importance what additional difficulties had been encountered, like iced pitots, and whatever implications that may have had on the flight control system and the crews interaction..

Thunderstorms are killers, that's it, you may very likely lose control over the aircraft, your aircraft may ice up, you may lose important parts of your aircraft due to high loads, your aircraft may be "airconditioned" by huge hail, your engines may suffocate and die, you may break up in flight or being thrown out of the base of a CB with no room and no reference to recover..

and it makes no difference at all which type of aircraft it was..

so what we learn and should take away from this case already..

avoid CBs at ALL COST, that may help us

P.S.: all the speculation in the thread about pitots, and ALTN Law and what you have here, THAT is pretty useless, I agree, and will not help us..

WhyIsThereAir

2nd Jul 2009, 22:10

It appears that AF447 hit the water within about 30nm of the last position report. (The June 6 location is about 30' north, the currents from June 1-6 would make the location about 30' south.) The preliminary report would give us that the plane was intact and if not exactly controllable, at least not a lawn dart. We have no way to guess when things went really bad, but we know they started to go bad about the time of the position report.

How fast can you descend from FL350 and still have a mostly intact plane capable of a horizontal orientation by the time you get to the wet stuff? Alternately, assuming the engines shut down for some reason at altitude and wouldn't come back, how slowly can you go down? Keep in mind you want to hit ground within 30-100nm of the initial problem. (Why do I assume the engines shut down? Just because it means you aren't going very far; there is no proof or even indication that they actually did.)

SaturnV

2nd Jul 2009, 22:18

Madbob, LH507 flying 20 minutes ahead, monitored 121.5 the entire flight, and heard nothing from AF447.

SaturnV

2nd Jul 2009, 22:29

Whyisthereair,

Here is the plot of the search area for the pingers.
http://i136.photobucket.com/albums/q199/tahitiplage/SNAG-0315.jpg

The primary area being within the circle.

The search plot suggests that if AF447 deviated from the track, it deviated to the west. Such would be consistent with the pattern and sequence of wreckage and body recovery, given the drift.

320 driver

2nd Jul 2009, 22:44

ECAM actions:

Do you really think the US *only* used satellites to "help" discover the crash site? That's no different to flying high over the area and using a pair of binoculars.

Think about it...

Sorry, don't understand your point. What are you trying to say?

LeandroSecundo

2nd Jul 2009, 23:05

Hi,

Grayengineer:
This stall i really feel was at low altitude as if they were still flying and maybe looking to ditch. There is no evidence that they were not trying to ditch and this impact type certainly points to a possiblity.

If they were trying to ditch (a la Sully) certainly the passengers were fitted with their inflatable lifejackets .
So far .. no bodies were found wearing those lifejackets .. and the lifejackets found were not inflated.
So far I reject the possibility of a voluntary ditching .. and I don't reject big pieces of this plane falling from the sky ...
I'm more suspicious about the plane in one piece falling in the water.

Bye.

Will Fraser

2nd Jul 2009, 23:18

From one viewpoint, if the a/c was airworthy it could glide quite a ways, but to what end? Over the open sea there is no reason to forestall the inevitable contact with water. Give it time to configure with pilot selected drag for water landing. If it was airworthy and making power, try for diversion. If compromised structurally or power wise, and a water landing was inevitable, life vests would have been donned. If even an unsuccessful ditch, some would likely have survived, but there were no bodies with water in lungs. Multiple Tx would have been made, some signal sent.

If the BEA are correct and a/c was intact until hitting the water, the 'forte acceleration' would most likely have claimed all souls. As has been stated, the BEA's position just smells a little like an informed guess, a little different take on the data. Not as egregious as "It was Lightning", and also not as unbelievable as "they almost made it". I think the tailcone hitting first to disrupt the VS attachments is as good a theory as any. There is no real reason to believe the BEA would "shade" their comments, but neither would one expect them to aggressively push a position (absent good data) that would paint anyone in a bad way. Too many times, however, when "all reasonable doubt" is impossible to remove, it is the flightcrew that ends up holding the bag.

It isn't unreasonable to say that given the originating party, and a need to give the press something, AF looked at the ITCZ, ABI looked at the pilots, (and pitots), the pilots looked at the pitots, everybody looks at ACARS, and truth be told, I am avoiding looking at the pilots.

Smurfjet

2nd Jul 2009, 23:25

I fear this is now going badly for AI and all who promote FBW and the 'protection' offered by multi-redundant systems and software.

IF the a/c had been thought to have broken up at high or medium level due to 'exceptional' turbulence' then Force Majeure could have been declared.

As it is, barring some unknown other structural failure (HS or forward section separation?), it is looking as if all these 'protections' didn't. There is the bad news for a 'failsafe' design.

I sense this will reverberate heavily.

If ditching is one of the considered scenarios, no amount of AI and/or Software protection will make it safe, at night, in a thunderstorm, and most likely with heavy seas.

Let me backtrack.

It broke up either:
1-In flight
2-On impact

Since it seems the BEA is shying away from 1) (does not mean it is discounted) then 2) gives us 2 more options:

1-it impacted in some kind of a controlled fashion, including ditching. Given the circumstances, the chances of success were very slim.
2-It impacted in an uncontrolled fashion, and in this case the industry has to determine why (and software can be involved).

An old and bold instructor once told me that when the brown stuff hits the fan, it is too late for protections (meaning they are there to avoid, not save). Back to basics might give you a chance if you're lucky.

safetypee

2nd Jul 2009, 23:26

An initiating item in this accident appears to be the blockage of all pitot systems (weather related), which resulted in ADCs degrading / shutting down.
A significant, but not catastrophic problem for the crew is the loss of all airspeed indications. There is a crew drill and flight procedure for this, and based on other incidents it has been demonstrated that the aircraft can be flown with relative safety until the conditions improve – based on weather research, circa 5nm average.
However, it is not know if flight without airspeed in this instance was that easy, either because of the environmental conditions (severity / extent), crew capability / ability, or lack of other flight instrument displays.

The flight procedure relies on engine power setting and attitude information.
Power:- Other incidents had identified engine problems in similar conditions. However, these events were generally subsequent to any pitot (TAT) problems (ice shedding vs ice forming) and were cleared quite quickly. Even if the engines were damaged the aircraft could have glided for some time, the engines relit, and systems reinstated; thus the lack of engine power / setting information due to engine problems might be discounted.
Attitude:- There has been speculation about ADC - IR interaction leading to the loss of attitude information, but even with multiple ADIRS failure the ISIS should have provided an independent attitude display. However, airspeed – attitude interaction within ISIS should not be discounted.
Question – of the previous airspeed related incidents, how many aircraft has ISIS vs conventional stand by instruments?
Another possibility is an erroneous switch selection which resulted in the loss of all attitude displays.

Other airspeed incidents reported instrument indications and alerts which might lead the crew to mishandling the aircraft – over-speed / stall, and it is the result of these which could have developed the accident.
Over speed:- This condition might be detected by vibration – buffet or external noise, and up to a point, depending on trim state, the aircraft might self recover.
Stall:- In the event of slowing down without ‘protections’ (ALTN law) the aircraft could stall. As I understand there would be some AOA input (stall warning / stall annunciation?) yet at the same time an over-speed alert could be given due to the faulty ADC.
If the aircraft were flown into the stall then the (over) trimmed condition might further delay the recovery – a possible connection with the recent A320 accident, 737 accident (AMS), and GA incident (the latter two required forward trim to enable stall recovery).
Spinning is discounted as there is no supporting evidence; a spin requires stall and roll conditions to initiate it, also a combination of aerodynamic and inertia aspects which might be difficult to achieve/sustain (ALTN law has a strong roll centring force).

A stall could account for the subsequent high cabin rate and most aspects the impact description.
However, even in a ‘stable’, long duration stall – high rate of descent, it might be expected that the pitot functions and some instrument displays could be recovered as the ice melted. If ice crystals were the problem, then the aircraft only had to exit the conditions enabling the pitot heaters to regain their effectiveness - not a descent below the freezing level.

Thus the focus of attention might be on attitude displays, abnormal procedures, and the trimmed condition when flying without airspeed.

lomapaseo

2nd Jul 2009, 23:37

I had considered that a possible reason that no radio calls to nearby traffic were heard/made was probably because the crew were preoccupied with trying to save the aircraft first.

Again I can't conclusively agree yet that the aircraft made it down in one piece but will have to admit, with this boards validation, that the debris field does not show much scatter. If I continue to accept this I tend to conclude that the aircraft must be pretty rugged to make that drop in one piece.

Thus I am very interested in the nature of the aerodynamic upset that might have begun at altitude.

And as always the difference in this event between the chicken and the egg regarding the ACAR messages.

carry on:ok:

wes_wall

2nd Jul 2009, 23:45

fr8mastr
Of course its pilot error, has there ever been an Airbus incident/accident that was not?

BEA had its day in the sun, and still no clear indication what happened. Even BEA cannot say with any degree of certainty what the situation was, and understandability. So, give it some thought.

Cannot be pilot error, AF would have to assume responsibility.

Cannot be airplane, Air Bus et all now in the soup.

Airplane part(s) – hummmm.

ClippedCub

2nd Jul 2009, 23:49

What "kind" of force (s) would "grab" the V/S, ripping it of without touching the rudder?Inertial forces, but the afterbody failed around the vertical, i.e., the VS didn't depart the afterbody, the afterbody departed the vertical.

Assuming the report is factual, it could easily have been backed up with reversion of debris to find ground zero, and demonstration of each item showing signs of downward compression force along the length of the fuselage. That would be convincing analysis, yet it is missing in the report. Won't speculate on what that omission means though.

If they hit wings level, could imply they had attitude. If they had attitude, they could have gotten out of a stall if in one. Flat spin is another matter. Said impact heading was in direction of flight, though don't know how they could know that. Downdraft from the thunderstorm could partially explain crash location proximity to last reported position.

Not blaming this on the pilots, keeping an open mind, without prejudice.

augustusjeremy

3rd Jul 2009, 00:03

recording here:

http://www.fab.mil.br/portal/voo447/AUDIOS/020709/audio_020709.mp3

ClippedCub

3rd Jul 2009, 00:18

The TU154 animation is a characteristic of deep stall with T-tail. If the A330 found itself in full-on stall with attendant nose pitch up, they crew should be able to recover with just the horizontal. If for some reason that wouldn't work, alternating thrust and reverse thrust could rock you out. But of course the FADEC probably wouldn't allow reverse thrust with weight off wheels.

The tail should have been enough. Will pull some conventional tail, low wing, transport wind tunnel data when I get a chance.

infrequentflyer789

3rd Jul 2009, 00:23

If they were trying to ditch (a la Sully) certainly the passengers were fitted with their inflatable lifejackets .

Whilst I very much doubt this was an attempted ditching, the Sully comparison wouldn't prove it anyway, since his pax didn't apparently have lifejackets on, see eg.:

http://newsimg.bbc.co.uk/media/images/45381000/jpg/_45381535_ap_passengers466.jpg

ClippedCub

3rd Jul 2009, 00:44

FWIW, read something about finding a piece of trim from the elevator. Was that what we thought was an aileron segment earlier.

HarryMann

3rd Jul 2009, 00:45

FWIW

In free fall in a stable flat attitude at 205t, terminal velocity could be in the region 200 ft/s ~ 300 ft/s - at sea level density. (obviously back of a fag packet calculation, but might give an idea)

Thats as little as 2 minutes from cruise altitide

protectthehornet

3rd Jul 2009, 00:57

reason to delay ditching...
radio distress call...possibility of ship nearby etc

remain airborne as long as possible

of course, the middle of a storm is a tough place to be.

ClippedCub

3rd Jul 2009, 01:11

You can get a nose down moment from flaps and deploying the landing gear, more so from the flaps. Redistributing fuel, if possible, would help, but that's time consuming.

EGMA

3rd Jul 2009, 01:24

The real question is whether the pilot flew the aircraft into wx that it couldn't handle or the flight control systems gave the pilot an aircraft that couldn't be flown.

The rest is all consequential ...

safetypee

3rd Jul 2009, 01:27

ttcse re #2830 – “… sit with a long duration stall and not try to recover only because they lacked instruments …”
I did not intend my post to read that way.
The issue, as with the 737 accident/incident (and speculation on the A320 accident), is that with an ‘over-trimmed’ nose-up condition there may be insufficient nose-down elevator power to affect a stall recovery. The stall / trim condition might be further aggravated by the apparent aft cg.
I have sought further understanding in http://www.pprune.org/flight-testing/378395-a320-stall.html#post5019448

A characteristic of some FBW aircraft appears to be that in comparison with conventional controls there is a lack of control/trim-force feedback on the stick. Thus for pitch trim, the trim position (with respect to balanced flight – auto trim follow-up in normal law) has to be determined from a scale. Thus do pilots need to be aware a suitable trim range for stall recovery, and what effect has ALT law on this situation?
The above is far from fact, hence my questions in the other forum.

The crew might have been aware of a stall if the AOA provided an input for indication / alert.

Lightning6

3rd Jul 2009, 01:30

EGMA

3rd Jul 2009, 01:53

CC...Lowering of flaps and gear might have made a difference, presuming they were in a stall, but, given the time from altitude to surface, would that be your first decision? There was a hell of a lot going on up there, and apparently little time to make any logical decision. Don't get me wrong, your logic is good, but can you imagine the dramatic situation they were in?

Sorry, I have to disagree ...

If the main plane was still flying, flaps move the center of pressure forward, causing a pitch up; they permit a nose down attitude at low speeds for this reason.

And, yes, at FL350 the last thing I would think of is gear/flaps.

pacrat

3rd Jul 2009, 02:48

I am keen to understand more about the significance of the “Advisory Cabin Vertical Speed” transmitted at 0214.

Until a few seconds before this message all ACARS related to the suspected loss of reliable pitot information and sequenced deactivation of systems depending on it. Namely A/P , A/T airspeed displays and degraded control law etc.

There has been much discussion on the techniques of handling a loss of reliable airspeed. Power plus attitude maintained at cruise values would generally be expected to suffice and should not readily see the aircraft depart controlled flight. So do we assume that the aircraft should have been right side up and under some degree of control to this point?

But what of the “Advisory Cabin Vertical Speed” which the report states;

Symptoms: Flashing of the cabin vertical speed indicator on the SD’s PRESS page.

Meaning: This message indicates a cabin altitude variation greater, as an absolute value, than 1,800 ft/min for five seconds.

This is cabin rate, not aircraft rate. If the hull was still intact it suggest the Cabin Pressure Controller (lacking good altitude input) had perhaps lost control over pressurization. Did the crew, already facing a dire situation, become aware of a rapidly climbing cabin altitude and initiate an emergency descent?

Turn off track! Lower the nose, Thrust Idle and Speed brakes out!

That severely challenges the “maintain power and attitude for cruise” scenario.

With speed brake the already limited speed range between high mach stall and low speed stall is dramatically reduced. Without displayed IAS and considering the associated buffet and likely turbulence it would have been a difficult task for any pilot in their predicament to stay within normal flight parameters!

So was the “Advisory Cabin Vertical Speed” merely a further symptom of things going wrong or a contributing factor? Perhaps the straw that broke the camel’s back.

UNCTUOUS

3rd Jul 2009, 03:25

*twenty-four automatic maintenance messages were received between 02:10 and 02:15 via the ACARS system. These messages show inconsistency between the measured speeds as well as the associated consequences;

* visual examination showed that the airplane was not destroyed in flight; it appears to have struck the surface of the sea in a straight line with high vertical acceleration.

"Inconsistencies between the measured speeds" was adequately explained by OVERTALK in post 322 (http://www.pprune.org/rumours-news/376433-af447-now-

added-preliminary-report-17.html#post4978855) on 06 June.
i.e.
1. Port and starboard pitot and static sources will be recording significantly different speeds during a spin
2. A spinning aircraft will strike the surface in a relatively level attitude but also "in a straight line with high vertical acceleration."

Think we're back to a loss of control in coffin corner (for whatever reason).

ALSO RELEVANT (for explanations):

posts 324 (http://www.pprune.org/rumours-news/376433-af447-now-added-preliminary-report-17.html#post4978873),

#325 (http://www.pprune.org/rumours-news/376433-af447-now-added-preliminary-report-17.html#post4978877) and #2222 (http://www.pprune.org/rumours-news/376433-af447-now-added-preliminary-report-112.html#post5015371) and #2412 (http://www.pprune.org/rumours-news/376433-af447-now-added-preliminary-report-121.html#post5023126)

ClippedCub

3rd Jul 2009, 03:31

given the time from altitude to surface, would that be your first decision?

The Edwards' test pilots know to extend the gear for spin recovery last chance effort if all else fails, so there is some precedence. The finless B-52 guys figured out gear extension helped due to the aft bogey. Depends on the pilot and his knowledge of the depth of aviation that preceded him. But face it, if you're stuck in a stall, you'd be figuring it out real quick.

There is another precedence though from GA. They interviewed survivors after engines fell off of Buckers, before they cabled them in, asking why they didn't bailout. They replied they still had 3 axis control, where in straight and level descending flight, figured all was well, and didn't grasp the sink rate till they got low. Don't know if this is even applicable in this case, but thought I'd throw it out.

If the main plane was still flying, flaps move the center of pressure forward, causing a pitch up; they permit a nose down attitude at low speeds for this reason.

Flaps down cambers the airfoil and creates a nose down pitching moment in 2D. If that is reversed, then the B-2 would use down elevator for pitch up. Additionally, when applied 3D on an aft swept wing, the 2d effect
still applies, and the outer portion of the wing is making more lift aft of the aircraft cg producing a nose down moment.

The nose down attitude with flaps for landing is because the stall AOA is reduced flaps down.

ClippedCub

3rd Jul 2009, 03:37

Port and starboard pitot and static sources will be recording significantly different speeds during a spin

Additionally, pitots are accurate for small angles, below 10-15 degrees AOA. Much more than that and you need a flight test boom. Pitots would measure different pressures at high AOA for different waterline locations on the nose, even on the same side.

surplus1

3rd Jul 2009, 03:39

no, "beyond all reasonable doubt" is not possible in a lot of cases, and may not be possible in this case..

Thank you for your reply but, with all due respect, I disagree. The key word is reasonable. We can never be 100% certain and that is why the cause of every accident is always defined as "probable". With data from from the FDR and CVR we can determine the probable cause beyond all reasonable doubt.

I agree with all the dangers you articulate associated with the penetration of convective cells. However, your message infers that you are convinced beyond reasonable doubt that this aircraft did penetrade a deadly cell. With all due respect you have no verifiable data that supports that hypothesis. It is only your assumption.

We do know, beyond all reasonable doubt, that the crew lost control of the aircraft at some point between INTOL and TASIL, but we do not know where that occurred nor why. We can logically presume, beyond all reasonable doubt, that they did not descend 35,000 ft with the deliberate intention of executing a water landing in the Atlantic ocean for the thrill of it.

We can also presume that an involuntary descent of approximately 7 miles in a large T-category transport aircraft, out of control, is most unlikely to have ocurred with no structural damage of significance prior to impact. Such a presumption is not logical. It is a fine aircraft, but it is not immune to structural damage in flight.

Only the FDR and CVR can definitively answer the questions that we all have. IF they are recovered and readable, it is only then that the various hypotheses can be developed into a scientific theory. The probable cause will then have been determined - beyond reasonable doubt.

Lightning6

3rd Jul 2009, 03:44

The Edwards' test pilots know to extend the gear for spin recovery last chance effort if all else fails, so there is some precedence. The finless B-52 guys figured out gear extension helped due to the aft bogey. Depends on the pilot and his knowledge of the depth of aviation that preceded him. But face it, if you're stuck in a stall, you'd be figuring it out real quick.

I appreciate what you say CC, but these were not test pilots, they were probably not in a spin, and to drop the gear in the possibility of a ditching is a no, no.

One Outsider

3rd Jul 2009, 03:48

UNCTUOUS, OVERTALK and Dagger Dirk are one person.

ClippedCub

3rd Jul 2009, 03:52

Agree L6. But to them dropping the gear would be to gain some control and not for a ditching. I can't imagine these 3 souls would have just ridden it down without reconfiguring. We don't know the sequence yet, maybe they spun, slung the engine/s, were able to recover somewhat, and couldn't unstall because of an aft cg of the reduced configuration. Could we tell if the engines departed through the boxes.

Lightning6

3rd Jul 2009, 03:56

WhyIsThereAir

3rd Jul 2009, 04:03

What we can perhaps say that we know with some decent probability at this point is:

- They were almost surely at a known location at 0210 (from the ACARS msg), and almost surely still at FL350.
- They hit icing conditions at about that time that knocked out some combination of the pitots.
- This had various follow-on ramifications in terms of cockpit messages and degraded protections, at the least.
- At some subsequent time they found themselves in the water, within about 30-40nm of their 0210 FL350 position.
- A normal descent from FL350 normally takes more than 30 miles.

We can suppose that:

- There is some indication that they may not have deviated around weather that other pilots that night did deviate around. (The 0210 position does not seem to indicate any deviation, and they were already into icing.)
- They did not deliberately intend to fly in icing conditions
- They may have encountered other weather conditions post-icing event
- They did not intend to land in the water in pieces
- They hit the water in a somewhat horizontal attitude (from the prelimnary report).
- From the 30nm distance made good, we can presume that descent probably began within 10-15 minutes (or sooner) of 0210, else they would have landed somewhere else.

This sequence brings up two questions that seem fruitful:

- What did they hit after hitting icing that caused them to lose control? Is there any answer more likely than another?
- What condition was the plane in as it descended? Stalled? Spinning? Under any sort of control? We certianly can't know, but is there one condition that is more likely than others, if we accept the report's assumption that they hit somewhat flat with some forward motion?

(Edited to change 'conclusion' to assumption' in terms of the BEA report suggesting the plane hit approximately flat.)

Lightning6

3rd Jul 2009, 04:11

WhyIsThereAir... if we accept the report's conclusion

The report is not a conclusion.

EGMA

3rd Jul 2009, 04:14

rottenray

3rd Jul 2009, 04:21

Piper Driver writes;
Piper_Driver
Yes - you need the engines or APU to maintain pressurization and ... a loss of pitot information as well as dual engine failure ... possible Stall/Spin situation they may have lost engine power. However I still see nothing to suggest engine failure was significant in the accident sequence.
It's unlikely but cannot be ruled out yet - and unlikely as it is, it could turn out to be true.

-- The A-330-xxx has proven itself as a frame which is reliable.
-- Air France has proven itself as a company able to hire, retain, and train excellent pilots.
-- The ACARS transmissions are intriguing but certainly not the "last word" regarding what AF447 experienced. ACARS is not rendundant like flight systems, and the "top" of the aircraft needs to be within 75 degrees of "up" for it to work - so we might not have ALL the transmitted messages regarding flight law, et cetera.

A loss of thrust after a serious upset *would* explain a lot - heavy plane, changing flight laws, degraded instruments...

And, of course, we need to consider all the time required to try to "fix" all the various things gone wrong - huge workload.

Simile:
You CAN clean the rain gutters, replace a sprinkler head or three, mow the lawn, pprune the shrubs, and sweep the driveway -if you plan to on any given Saturday.

But if someone knocks on your door and tells you that you have to get all those things done *immediately* it might make it hard to do any of them, even though you can do all of them "in your sleep," so to speak.

I think one thing we haven't considered in a logical manner in this thread is that the crew might have simply been overwhelmed.

Pilots are never overwhelmed - until they are.

No disrespect intended - but it is true.

I can hand you a list of 10 things to do and tell you to get them done in 10 seconds, and you will.

But should I hand you a list of 15 things to get done immediately, and then turn the lights out, and then start smacking you around, run a strobe light...

The end minutes of AF447 were clearly in the realm of test pilots, not line pilots.

Normally we speak of holes in Swiss cheese - I think here we are speaking of holes in Havarti.

My point is this: Even if we never find out what the actual cause(s) were with AF447, we should take some basic lessons from it.

Many of the respected pilots contributing to this thread have commented negatively on a lack of authorized hand-flying - this needs to change, as there is no substitute for a skilled pilot.

Many have commented on "shi77y" communications along that route. I believe them - and I don't know if this "brownout" exists because the countries won't spend the money needed for more powerful R/T units or whether it is due to weather conditions - but it clearly should be bitched about until it gets fixed.

I'm going to phrase this as "lightly" as I can.

Serious pilots need to hold Airbus accountable for many automation issues. I'm not - repeat, NOT - damning Airbus for their great innovations.

I'm simply saying that YOU should be holding their feet to the fire for every single thing you don't like about the software or the philosophy behind the software.

Personally, I'm in love with the man wearing the stripes in the pointy end, and the man next to him who might need to take over.

And, personally, I'm very hateful of anyone who even considers the possibility that a flight I'm on *should* crash every so many times, based on statistics.

JD-EE

3rd Jul 2009, 04:24

WhyIsThereAir
- At some subsequent time they found themselves in the water, within about 30-40nm of their 0210 FL350 position.

That inspired me to go looking at the raw reports such as the BEA report showed them. It appears somebody saved 3 bytes by not sending altitude at least as an FL. It surely would be nice to know it's altitude at 02:10:34.

JD-EE

ClippedCub

3rd Jul 2009, 04:29

CC The B-2 is not a conventional aircraft ... I have not flown that type and have no knowledge of its control regime.

For stall recovery in a conventional aircraft you need the tail plane flying first. i.e. elevator authority. If you get the main plane flying first you are going back in the stall ... stalls and flaps don't go well together.

EGMA, not trying to be critical, just relaying my understanding. B-2 was a bad example for the reason you cited, we'll use the before FBW, B-2 flying wing predecessor, and the flying wing Horton? glider. Stalling the tail is bad news and a stalled wing unloads the tail. We do flaps down stalls all the time. Never spun flaps down, and wouldn't want to, but it can be done. With flaps you get the slats on the A330, and wouldn't want to deploy them during out of control unless that was the last option. The Tiger Moth slats pop out in spins if they're unlocked, but that is a very low wing loaded airplane. But the F-4 slats come out during transonic manuevering. The A330 slats weren't designed for spins however.

EGMA

3rd Jul 2009, 04:41

I agree CC, I've only ever spun clean. I've stalled clean and dirty in a tee tail, I preferred clean; but then I'm an old (not bold) pilot.

Graybeard

3rd Jul 2009, 04:41

They would have stalled the A330 in all configurations of gear, flaps and cg in flight test back in 1994. How serious was the damage to the plane in the aft cg stalls?

A full stall series in a DC10, for example, will damage the ailerons and can tear the elevator counterweight horns right off.

For training or refresher, wiki has a fair description of spins and flat spins. The 65 to 90 degrees angle of attack of a flat spin is awfully similar to the BEA report of AF447.

GB

Mike HD

3rd Jul 2009, 05:07

According to CNN, "They have not found any clothing, he [air accident investigator Alain Bouillard] said, but was unable to say why."

BBC writes: "The French investigation appears to contradict earlier reports attributed to Brazilian pathologists. They said last month that the injuries sustained by the passengers whose bodies had been found suggested the plane had been in pieces before it hit the sea.
Mr Bouillard said France had not yet been given access to those autopsy reports."

The main characteristic that caught my eye with the Brazilian reports was that bodies were found "without any clothing", or "minimal clothing". (no link here, sorry) I'd posted before that it takes more than terminal velocity to strip people of their clothes - witness sky divers. I had concluded that the only way bodies could get stripped off their clothing is by getting ejected into air traveling at much higher speeds, e.g. Mach .8 or such. Which suggested that the plane did indeed break up at high speed and high altitude(?).

However, high speed and low altitude (ocean level) breakup of an AC could have the same result. This would require bodies getting ejected upward from the AC even as they had traveled downward (vertical component) at a high speed. Only some sort of rebound effect could explain that.

Or, is the phrase "without clothing" meant just like CNN reported, that there was no clothing (apart from bodies) found. Which, however, ALSO seems ambiguous. Does anyone have any better insight into this?

The BEA report does sound very convincing - I am trying to figure out how to account for other evidence within the context of that report. It sure would be helpful if the relevant agencies could get their acts together.

Mike HD

3rd Jul 2009, 05:35

"Perhaps many wet fabrics sink" - they do, and tend to drag you down. As I learned with training as a water safety instructor, needing to swim several lengths of an olympic pool with shoes, socks, jeans, and a sweatshirt. They REALLY drag you down. Which, BTW, removes you from the "wave action" you adduce:

" I imagine the attire of passengers traveling from Rio would be no challenge for waves to remove." Those waves must have very nimble fingers to unbuckle belts and unbutton shirts. And, perhaps undo shoelaces, too?

I didn't intend my question to be taken frivolously - if BBC or any such news agency perks their ears on something that had caught my eye - well, maybe there is just a tad of credibility to that?

Xeque

3rd Jul 2009, 06:21

I'm really confused now. From the London Telegraph:
Investigators said the Airbus "descended vertically" and dropped 35,000ft in a matter of seconds, hitting the water in its exact flying position.

Now, for an object to fall around 7 miles in 60 seconds it needs a terminal velocity in excess of 400 mph. The inferance that 'it fell in a matter of seconds' is that it completed the distance in less than 60 seconds putting it at or near supersonic speeds. And it pancaked, intact after all that?
I know that Mother Nature has her moments but I have never heard of a downdraft so powerful as to have accomplished this and if the aircraft hit the water 'in its exact flying position' then it certainly wasn't an engine assisted dive or do they mean it's position at 35,000 when the catastrophe struck?
What are the French trying to tell us here I wonder?

PJ2

3rd Jul 2009, 06:34

rottenray;
And, personally, I'm very hateful of anyone who even considers the possibility that a flight I'm on *should* crash every so many times, based on statistics.
You're not whistling Dixie.

This is not the thread to take further the excellent points you have raised and with which many cockpit crew will agree including myself, (now retired).

The points you raise have been discussed elsewhere at length and deserve greater exposure; this is not the first time they have been raised and should form the lessons this industry, including cockpit crews and their representatives, should take from this, and other recent fatal accidents.

Previous posts in this thread have made it clear that for those who fly the aircraft and for those who fly commercially, period, this is a serious discussion on fundamentals and not an uninformed, anti-Airbus rant. What needs saying applies equally to Boeings.

Nor does this focus on the crew of AF447. Few if any here would not be similarly challenged.

Well said, sir.

PJ2

EGMA

3rd Jul 2009, 06:44

I'm really confused now. From the London Telegraph:

Now, for an object to fall around 7 miles in 60 seconds it needs a terminal velocity in excess of 400 mph. The inferance that 'it fell in a matter of seconds' is that it completed the distance in less than 60 seconds putting it at or near supersonic speeds. And it pancaked, intact after all that?
I know that Mother Nature has her moments but I have never heard of a downdraft so powerful as to have accomplished this and if the aircraft hit the water 'in its exact flying position' then it certainly wasn't an engine assisted dive or do they mean it's position at 35,000 when the catastrophe struck?
What are the French trying to tell us here I wonder?

I think you'll find that is a media assumption ... if the SLF didn't have their life jackets on it must have been quick. Nowhere in the report does it mention a descent rate.

DingerX

3rd Jul 2009, 07:27

For those of you who have been with us for some time, here's some of what the report says that's interesting, or novel.

ACARS messages:

Anyone interested in the problems of sorting out the timing of ACARS messages should read the report, as it lays in out detail the logic behind the transmission order, and the shortcomings of using ACARS messages in this way. Faults are accumulated and transmitted in hierarchical order every minute. Warnings are transmitted in real time. Not every problem results in a fault, and not every warning corresponds to one either.

They do not have an explanation for the TCAS fault at this time.

The do have reason to suspect that the 30-second+ intervals in transmissions starting at 0213 are caused by an interruption of the satellite connection.

There's an automated position report at 0210. (this has been noted already here)

Weather:
at 0210, AF447 was in the middle of a mass composed of 4 CB cells that had grown together (an hour and a half before?), with tops around 52,000 feet.

Weather information:
There's one little note: the SIGMET that expired at 0200 may have contained an error:

WSBZ31 SBRE 311752
SBRE SIGMET 5 VALID 311800/312200 SBRE-RECIFE FIR EMBD TS FCST SW OF CLARK PSN/ PEPER PSN/ NEURA PSN AREA TOP FL350 STNR NC=
On peut s’interroger sur la validité de ce message, pour deux raisons :
ˆˆ la ligne AB est orientée sud-ouest / nord-est or, en pareil cas, on attendrait une mention SE OF ou NE NW OF, et non SW OF comme c’est le cas dans le SIGMET,
ˆˆ les images satellite pendant la durée de validité du SIGMET positionnent
la zone de convection plutôt au nord-ouest de la ligne AB qu’au sud-est.
Il est donc envisageable que ce SIGMET comporte une erreur, avec une
mention SW OF au lieu d’une mention NW OF. Dans cette hypothèse, le SIGMET 5 SBRE viendrait compléter la zone identifiée dans la FIR ATLANTICO, comme représenté par le tracé vert dans la figure ci-après

(I'm assuming for 'sud-est' on the second bullet, they meant 'sud-ouest')

Radar:
This has already been treated above. Other flights saw the weather on radar (when placed in the correct mode). AF has a detailed chapter on wx radar operation in their "supplementary aeronautical manual" which "is not imposed by regulation".

In short, we know that they flew into the middle of a huge thunderstorm without any meaningful deviation. The flight went down sometime thereafter. The interruptions in ACARS messages imply that an upset may have occurred as early as 0213.

Dani

3rd Jul 2009, 07:38

I think this thread goes lost even more after the first report from Bea.

Let me clarify the thing about "intact on impact":

Bea says that the A330 was "not destroyed in flight". They can tell by the damage scars on the debries they found.

Now, what does that mean exactly? It doesn't necessarily mean that the aircraft flew (controlled or uncontrolled) into the water. It merely means what it says: it was still one entity at the impact.

It's very unlikely that they ditched. It's very unlikely that they glided towards the water for any reason.

The most likely theory is still the one with the iced probes, the unreliable speed and the inaptitude to control it. They got some stalls and some overspeeds. They may have lost some critical control surfaces (remember: they only found the tail, but not the elevator or the wings), the aircraft got uncontrollable and fell down, everything between high and low speed.

This aircraft was still "complete" as a whole. But it was not controllable. That's what Bea wants to tell us. Nothing else, nothing more.

Dani

BOAC

3rd Jul 2009, 07:40

On the topic of 'translation', I have only the English report. Can anyone tell us (from the report) how the BEA appear to have deduced the 'heading' at impact (?if what I read here is correct!?) and how we all appear to have 'accepted' a near vertical descent rather than some sort of varying heading during descent - or even 'turn-back' - resulting in impact near the last known position?

TiiberiusKirk

3rd Jul 2009, 07:47

jeremiahrex (http://www.pprune.org/members/302838-jeremiahrex)

Quote:
While it is indeed possible to extend radar coverage to every part of the globe...
Not with ground/land based radar it isn't. Radar is line of sight and the earth is curved. Even at altitude, an aircraft will often be below the horizon WRT to the nearest land.

Rustum

3rd Jul 2009, 08:03

Leandro:

If as the BEA report suggest .. the plane don't broke in air before touch the water .. why no more ACARS messages durring the fall
No more defaults to be detected and send ... ?

Non-frequent SLF here (CPT to Europe maybe once/year), fascinated by the physics of flight; and I have learnt a mass of things about said physics and flight control systems by following this thread.

Some tentative questions: Is there a consensus that the ACARS messages were transmitted prior to the aircraft exiting normal flight? Is it possible that the ACARS transmissions occurred after that exit? In other words, things were already starting to go wrong in terms of normal flight and the ACARS were more or less transmitted at the same time, or that there was an overlap between transmission and sub-normal flight. Extending this further: the end of ACARS transmissions doesn't necessarily point to break-up at cruise level?

Thanks.

Dani

3rd Jul 2009, 08:10

Aircraft with unbalanced control surfaces (i.e. if you loose some of them), tend to oscillate between the extremes (speed and attitude). So they go nose up, speed decrease, stall, nose down, speed increase, overspeed. And so on. Until it hits the surface. How it hit we still don't know. But obviously just in a straight level, which is pure randomly, it could also have impacted nose down. It all depens in which phase of the oscillation it was.

Concerning the VS I don't know what you're refering to.

As I (and others) stated long time ago: The ACARS messages don't deliver the cause of the accident, but the outcome. As soon as the aircraft spirals down, you get these weird messages. So it's very well possible that they were created after the aircraft became uncontrollable.

Dani

thescouselander

3rd Jul 2009, 08:18

Hi all,

I've been lurking on here for quite a while but I though I might post on a though I had after reading all the posts on here and the report yesterday.

First off I'd just like to say I am not a pilot and I dont work in civil aviation. However, I am an engineer with 10 years experience and an aerospace background. Several years back I took part in 2 crash investigations regarding unmanned military aircraft.

The indications seem to be that the aircraft went into the sea at a high rate of speed but also it would seem it lost considerable altitude in a very short time. This does not seem consistent with the fact the aircraft met the ground in one piece - how could so much altitude be lost so quickly?

My suggestion is that the pitot tubes could have failed (iced up) quite some time before the accident or any indication of a fault. Suppose all three tubes failed at approximately the same time holding the readings for cruising altitude and speed. The consistency in readings may have got past the computer which may not have raised the fault.

In this eventuality is it possible that the auto pilot could have continued to operate on false information leading to gradual loss in altitude over a relatively long period and hence this was not noticed by the crew or ATC which would get altitude from the aircraft via secondary radar.

The pitot fault messages could have been caused as the pitot tubes began to de-ice as a result of the warmer air at lower altitude. If they did not de-ice at the same time this would cause the disagreement which initiated the fault.

After that the crew would have had a high workload and very poor situational awareness due to the instrumentation fault. Perhaps the presence of weather also blocked out the moonlight making any visual cues difficult to see.

Could the crew have flown into the sea at high speed if they had much less altitude than expected? Maybe the tail first impact suggests the only saw the sea at last minute and pulled up resulting in the tail striking the water.

Flintstone

3rd Jul 2009, 08:23

I'll take up only two, straightforward, points and leave the rest to m'learned friends.

.....ATC which would get altitude from the aircraft via secondary radar

Have you looked at where this occurred? What ATC radar?

Could the crew have flown into the sea at high speed if they had much less altitude than expected?

Do you not think they would have noticed the loss of >30,000 feet of altitude?

DingerX

3rd Jul 2009, 08:30

BOAC -- they didn't state anything of the sort. They had "ligne de vol".
They also provided their evidence.
From the evidence available, they could state two things:

A. The attitude of the aircraft relative to water at the moment of impact.
B. The vector of the aircraft at impact.

A. was more or less cabin level to the horizon (ligne de vol)
B. was far from gentle and largely vertical.

That's it.

Tagron

3rd Jul 2009, 08:31

I have been thinking on similar lines to Safetypee’s post 2839.

There have been a number of references in this thread to the QRH procedures for flight with unreliable airspeed. Some of the comments seem to imply this is an easy task- just set the power, maintain the pitch attitude and it will work out. I am not convinced.

This procedure may be fine in stable weather situations, but all the evidence suggests AF447 was encountering far from benign conditions.

Let us assume that around the major Cbs in the ITCZ there were significant horizontal and vertical windshears, a not implausible scenario. An encounter with a rapidly increasing headwind would result in a rise in airspeed, which would need to be countered by a reduction in thrust to avoid a potential overspeed, but the crew would have no means of identifying this need and the speed rise would go unchecked..
.
If the crew were attempting to use GPS or inertial groundspeed as their cue (because there was no alternative) they would likely increase thrust instead of reducing it . Hence the risk of an overspeed would be greatly increased.

Now run the converse scenario of an increasing tailwind. Airspeed falls, crew unaware ,so do not take corrective action, ground speed increases, so thrust is reduced, result is underspeed.

Add in a further possibility. If at the instant of A/THR disconnect, the system had already reduced or added thrust to counteract a speed excursion, crew action to set the QRH reference power could actually exacerbate the speed error.

In the vast majority of situations, one would expect these effects to be minor, transient and hence containable. Is it possible that in the weather situation in which AF447 found itself, the effects were major and cumulative, to the extent that a critical underspeed or overspeed
occurred ?

Even if this situation did not take place, it seems to me the crew had a major task on their hands that could have reduced their capacity to manage any other.event that might have occurred. It may not be necessary to speculate on the implications of Airbus Alternate Law -
the potential could be the same for all types. And I keep asking myself how well I would have coped.

LeandroSecundo

3rd Jul 2009, 09:00

Hi,

Eurocockpit - Archives (http://www.eurocockpit.com/archives/indiv/E009454.php)

Unfortunately it's in french.
The use of a translator (like Google) may help but it's not allway accurate.
For one who understand french .. it's nice to read.

Bye.

OleOle

3rd Jul 2009, 09:03

In this post http://www.pprune.org/rumours-news/376433-af447-now-added-preliminary-report-106.html#post5012151 you can see that the speed over ground was almost constant up to 2:10.

From that I would dare to conclude that the altitude was constant too.

BOAC

3rd Jul 2009, 09:18

They had "ligne de vol". - yes, but it appears to be an unfortunate expression with more than one meaning, and I feel they should have been more 'accurate'. We all 'deduce' the meanings from logic, but it is all about 'translation'

This from Google - Dictionnaire des sciences de la terre By Magdeleine Moureau, Gerald Brace

flight line: ligne de vol trace sur une carte de al trajectoire a suivre par un vehicule aerien

It doesn't help when even the French cannot agree! (Excuse the missing accents).

I have come to expect careful wording in accident reports, and to talk of high vertical 'acceleration' when presumably they mean deceleration (ie a 'hard impact') I find strange. EG do they mean they deduce it was Accelerating rapidly towards the water or is it as we actually 'understand' it?

starliner

3rd Jul 2009, 09:38

From the English BEA report p45:
"The first position message (AOC type message) was transmitted on 31 May at 22 h 39. On
1st June at 2 h 10 min 34, the last position received was latitude +2.98° (North) and longitude
-030.59° (West). The position transmitted was the aircraft’s FM position which, in normal
conditions, is close to the GPS position."

I am surprised by the news that the aircraft was set up to provide regular 10 minute AOC position reports via ACARS and yet no procedure appears to have been in place at AFR ops to react to the loss of these regular messages.

Flintstone

3rd Jul 2009, 09:38

Just not feasible for any number of reasons not least because pitot tubes don't feed the altimeters, static ports do.

As for the rest, a lengthy explanation would just derail this thread and there's been too much of that already.

YHM

Lemurian

3rd Jul 2009, 10:05

They had "ligne de vol".
- yes, but it appears to be an unfortunate expression with more than one meaning, and I feel they should have been more 'accurate'
Nothing unfortunate, it's in fact a rather accurate description of the aircraft attitude.
To illustrate its meaning, just imagine a tail dragger -a DC-3, for instance ; first it sits on its tail wheel and as it accelerates, the tail goes up from a forward pitch control input. There ! the aircraft is then "en ligne de vol".
That description is still used in flying clubs as to teaching take offs.

It doesn't help when even the French cannot agree!
There are two categories of Frenchmen :There are the French aviators and there are the French non aviators. And among them there are old French aviators and not old French aviators. Fortunately there are old French aviators who have French aviators' sons and daughters....:)

oleole

From that I would dare to conclude that the altitude was constant too.
It would have been a lot easier to read the report and see where they were cleared to FL 350 and also read their communications transcripts.

starliner
I am surprised by the news that the aircraft was set up to provide regular 10 minute AOC position reports via ACARS and yet no procedure appears to have been in place at AFR ops to react to the loss of these regular messages.
Good point. Problem is that these reports overlay on the incrusted routes on a screen.
First there are airplanes sharing the same route at about the same time.
Second, the dispatchers have to provide a lot of OPS requests on some 120 (a guess) long haulers at any given time.
Third, it is not really a monitoring system but a quick way of identifying who is talking, where he is and what his/her needs could be.
The fact that AF447 and AF59 were on the same route at the same time was, IMO, enough to hide AF447's position, unless the dispatcher specifically separates both traces from each other.
Another factor could also be that between 0330Z and 0415Z, there could have been a shift change at dispatch, with the normal hand-over tasks to the new dispatcher(s).
That the system could be improved for an irregularity alerting program is, again IMO, an absolute necessity.

320 driver

3rd Jul 2009, 10:11

BOAC

From a technical point of view they are quite right to use the term 'acceleration'. Acceleration is a change of velocity. It doesn't matter whether its an increase or a decrease (deceleration as you call it), from a technical point of view it is still referred to as 'acceleration'.

The situation you describe earlier, cyclic increase then decrease of attitude and altitude is fugoid oscillation. If the aircraft had been experiencing this then the flat attitude would have placed it near the bottom of one such oscillation, where it would have had a relatively high forward speed. The BEA appear to suggest it had low forward speed at impact.

JD-EE

3rd Jul 2009, 10:28

DingerX,

At the risk of being fined for extreme pedancy I note that a vector is a three axis plus magnitude item. They only defined approximations for one of the three (the vertical axis) and the magnitude. They did not define more than the rough plane (no pun intended) defined by the other two.

JD-EE

protectthehornet

3rd Jul 2009, 10:40

wondering

if the cbin rate was a climb and the crew didn't don their oxygen masks, couldn't they have become incapacitated *hypoxia* and then the plane, with its computer system failing due to pitot icing finally went out of control in the natural turbulence of a storm?

the more I read, the less I know.

320 driver

3rd Jul 2009, 10:45

It is entirely possible that an excess cabin altitude could have incapacitated the pilots. However, one would expect an ACARS 'Cabin PR : Cabin Excess Altitude' message if the cabin alt had risen to dangerous levels (ECAM triggers this warning at 9550ft plus or minus 350').

ralphie

3rd Jul 2009, 10:52

You seem a wonderful source of knowledge PJ2. I am sorry to hear that you are retired. I would love to hear that Airbus or Boeing or whoever would grab you as a fantastic teaching authority. That is the same for all other retired captains on this forum. The airline industry should be using you big time!!!

IcarusRising

3rd Jul 2009, 11:20

Can any one figure out why this aircraft ended up in this position and situation that accelerated the spiraling chain of events. Looking back at the satellite weather conditions in the area, I don't think any pilot in his right mind would plow along on the track the aircraft followed into disaster.

Why was the captain at rest, if he and the crew had done a thorough flight briefing and known that their track would take them through bad weather at a specific time window on this flight ?

How can two radars miss the weather if they were used properly unless the selector switch was turned to off at some stage !

I have been flying for 41 years and currently fly this amazing aircraft but I have always maintained a very cautious attitude to both my own and this aircraft's limitations, this attitude has served me well but I have noticed a complete state of complacency show its ugly head as far as young pilots sitting in the right seat or acting as cruise pilots. It is not uncommon for me to return from rest to find laptops out on the pull tray obscuring flight instruments or sorry animated discussions about work and pay conditions while the aircraft does her own thing an receiving looks of disbelief when voice my concern that monitoring aircraft flight performance and weather conditions mean just that and not getting sucked into complacency and side distractions. I am looked on by some crews as a relic and behind the times !

I have also noticed a general lack of respect for the power of weather and convective activity.

I hope positive lessons would be learned from this disaster and SOPS will start covering pilot cruise monitoring duties more extensively.

We have a duty to ourselves, our customers and this profession, to be vigilant at all times regardless of the level of automation available to us. Situational awareness and good judgment have never been more needed.

This chain of events for this accident seem to have started at flight briefing.

BOAC

3rd Jul 2009, 11:28

u674087

3rd Jul 2009, 11:50

Almost 1.5million views, 150 pages (plus those deleted) and although I may stand corrected, I don't recall anybody offering a theory anywhere near the preliminary report i.e. the a/c dropping out of the sky, in once piece, more or less straight and level with not much forward speed. I am also surprised at the lack of interest on the Yemenia thread, which even though as catastrophic has only attracted minimal media and PPRUNE interest.

This tells me that a) the BEA have got it wrong or b) even with all the experience of the contributors on this site, there is still some pretty important stuff that remains unknown in terms of airmanship, aerodynamics and structural integrity of a/c. Having worked in aviation for a very long time, I like to think that the answer is a).

The biggest bird I fly is a Twin Comanche, which is why I am an interested viewer only and choose to learn and not to comment... normally!

SaturnV

3rd Jul 2009, 12:01

On the condition of the bodies:

The BEA report only references the 30 bodies recovered by the French frigate Ventose. The other 20 bodies were recovered by the Brazilian Navy, and the initial body recoveries were by the Brazilian Navy.

The BEA characterizes the bodies recovered by the Ventose as "clothed and relatively well preserved." There is no characterization of the bodies recovered by the Brazilian Navy.

There is a possible undertone of frustration with the Brazilian authorities with respect to the bodies. Early on, the French complained about being excluded from the team performing the autopsies. The BEA report hints that the French are still in the dark, stating that the Brazilian authorities have yet to provide any autopsy results. (Some bodies have already been released to families for burial.)

The BEA report contains no information on how many of the bodies, well-preserved or not, are already identified. Once identified, passengers can be matched with assigned seats, and this can be a valuable data-point with respect to how the plane impacted.

And then there is the damage done to the VS by the Brazilians in the course of recovering it....

bud leon

3rd Jul 2009, 12:21

Like many others in this thread I have been lurking for some time but now I feel a need to post. I have an extensive background in emergency response, safety management and incident investigtion.

This thread is full of assumed minor detail and subsequent rather pointless analysis. But it seems to me there are some helicopter view issues which I feel would benefit from broad discussion and I feel are the real issues here.

I don't get the vibe that all that many here understand safety and reliability engineering. The first issue is my impression is that there is a common mode failure issue which deserves greater attention. Regardless of the real cause of this incident, my interpretation is too much depends on elements that can fail in the same way. Does anyone have a comment on that?

The second issue is that I am amazed it took so long to initiate an emergency response. While it might not have made a difference to lives saved, how can that be the case?

I expected more from the airline industry, I assumed things were more robust and I have lost some confidence.

Squawk_ident

3rd Jul 2009, 13:28

Thank you LeandroSecundo for having drawn our attention on this article. At the bottom it is indicated that a PDF conversion is available for download.

Eurocockpit - Archives (http://www.eurocockpit.com/archives/indiv/E009454.php)

I have translated 2 parts, one about a "NAV TCAS FAULT" alarm message that is "not fully explained" by the BEA. This might explained to the BEA how to explain what might be the reason and, two, a rather short description of the final "VERTICAL ADVISORY CABIN SPEED" ACARS warning message sent at 0214 by the plane.

1/BEA interim report page 51 (English)

NAV TCAS FAULT (2 h 10)

- - - Flag on PFD and ND
Meaning: This message indicates that the TCAS is inoperative. At this stage of the
investigation, this message has not been fully explained.

NAV TCAS FAULT RC proposition :

NAV TCAS FAULT: the Traffic Collision Avoidance System has failed because of the dysfunction of the ADR, due to the failure of Pitot, involves in the loss of this system by a failure of the transponder 1 (if selected - because of the ADR 1 failure) or transponder 2 (if selected - because of the ADR 2 failure). The loss of the mode C leads to the loss of the TCAS function.

2/BEA interim report page 52 (English)

ADVISORY CABIN VERTICAL SPEED (2 h 14)
Symptoms: Flashing of the cabin vertical speed indicator on the SD’s PRESS page.
Meaning: This message indicates a cabin altitude variation greater, as an absolute value, than 1,800 ft/min for five seconds

RC analysis :

2:14 UTC

No more failure message will be sent by the plane. Only two alarm messages are transmitted:

MAINTENANCE STATUS ADR2: the ADR2 has its degraded operation, which is only a confirmation of the situation resulting from the initial Pitot failure.

VERTICAL ADVISORY CABIN SPEED: the rate of variation of the pressurization of the cabin is abnormal. This message indicates a variation of the altitude of the cabin higher than 1800 feet/minute.

In a simplified way, the pressurization consists in “inflating” the cabin of a plane by admitting air from outside, heated by heat exchange with certain systems of the plane, and controlling the leak flow by means of a valve located at the back of the aircrafr. By doing this, the cabin is known as “pressurized” and the air that one breathes there contains sufficient molecules of oxygen to avoid the hypoxia which one would suffer with the altitude of cruising of the airliners. Fictitious altitude inside the cabin is thus lower than that of the plane. At an altitude of 35.000 ft (feet), the pressurization makes it possible to maintain the inside altitude of the cabin at around 8.000 ft. The parameter of evolution of this fictitious altitude of cabin is measured in feet/minutes.

Contrary to what could be thought, the message of alarm is not revealing of an explosive depressurisation since it is not an alarm “excess cab alt" that would have meant an excessive cabin altitude (higher than 9550 ft). It is actually an alarm message, materialized in the cockpit by the flickering of the Cabin V/S parameter on the pressurization screen, indicating that the altitude of the cabin is in evolution according to a variation considered to be excessive.
This variation can occur while the cabin is going up or down at more than 1800 ft/mn. Several cases of figures can thus arise:

-> The failure of the 3 ADR could involve the loss of the systems controllers of pressurization and let this one evolve abnormally.

-> The possible passage in overspeed of the plane, at the time of a loss of control, could have deteriorated and even tear off certain structural elements, creating a leak of pressurization then explaining the fast variation of altitude cabin, the latter being depressurized quickly before the possible rupture of the plane and the end of the transmissions following the disintegration of the aircraft.

-> The descent of the aircraft involves a descent of the altitude of the cabin ordered by the main controller of pressurization (the other being functionally on standby). It is what occurs with each descent so that at the opening of the door, on the ground, the outside pressure is the same than the one inside the cabin. There is thus a regulation of the descent of the cabin altitude as the plane goes down. If the plane would start a very fast descent, the controller of pressurization would try to reduce very quickly the altitude of the cabin. This variation is by design limited to 750 ft/mn, which cannot thus generate an alarm corresponding to a value algebraically higher than 1800 ft/mn. If the plane was not in descent but unfortunately in a fall, it would then join the altitude of the cabin before the controller of pressurization could sufficiently reduce the cabin. In this case, the pressurization would be reversed: the pressure outside the plane would become higher than that of the cabin. To avoid the implosion, “safety valves” and “negative relief valve” open in the event of negative differential pressure (0,25 psi). In this case, the rate of variation of the cabin follows the fall of the plane to minimize the difference in pressure and the rate can thus be much higher than 1800 ft/mn.

It is what the latter message transmitted by the plane could mean.

-> The loss of ADR SIGNALS, by rejection of the ADR following a partial or total internal failure, could have also involved the appearance of this alarm.

BJ-ENG

3rd Jul 2009, 13:31

From Air Safety Week (Sept 18th 2006), and although focused on T-tail aircraft incidents, some of the findings regarding vertical velocity/ trajectory under stall may be pertinent to the current discussion.

A Tale of Two T-Tails | Air Safety Week | Find Articles at BNET (http://findarticles.com/p/articles/mi_m0UBT/is_36_20/ai_n16729906/?tag=content;col1)

Re: MD82 crash (Preliminary) AUGUST 2006 (WCA708)

Quote (page3):

"the engines wouldn't have recovered until gulping much denser air at the lower altitudes, shortly before impact at their descent rate of over 7000ft/min."

...."According to the Flight Recorder, WCA708 descended at a high angle-of-attack "

Quote (page 4) :

"The descent from FL330 took 210 seconds. The debris field was only 200m long and 110m wide, indicating a near vertical descent with no forward airspeed. The crew had radioed that "both engines had flamed out" but they were merely locked back at flight idle."

4nsicdoc

3rd Jul 2009, 13:54

As a forensic scientist, I am intrigued that there has been no reporting of any histological exams of the remains of the victims, which would conclusively show whether an inflight breakup, with a resulting ejection of occupants, occurred. Subjection to ambient temperatures in the -40C range (which would be about right for that latitude in June) and a terminal velocity in the 190mph range at 30,000-35,000 feet would have resulted in almost instantaneous tissue freezing of all exposed flesh. The formula for deriving wind chill is:
T (wind chill) = 35.74 + .6275*(ambient)-35.75V^.16 + .4275*T(ambient)*V(airspeed)^.16.If your calculator is in your flightbag, the result is a windchill of about -300C.With rapid onset cooling of that magnitude, several things would be readily apparent upon microscopic examination; e.g., water transport effects (dehydration) extracellular ice formation with mechanical crushing damage to cells, intercellular ice formation damage, cell darkening and twitching if the cooling rate was>25decC/min, which it surely would have been.
Of course, knowing the mechanism of the injury says nothing about the ultimate cause of the loss of the aircraft, but knowing might narrow the possibilities.

barrymah

3rd Jul 2009, 14:12

LeandroSecundo - For one who understand french .. it's nice to read.

True, like the original bea report.

I make just one extract; which might be used as a 'health warning' for some posters....

"Nous nous contenterons donc, pour notre part, de reporter les éléments factuels que nous avons pu recueillir et de modestement proposer quelques mesures correctives ou recommandations qui, en l’état actuel de nos informations, nous sont apparues - a minima - pertinentes !"

We (eurocockpit) will restrict ourselves therefore to reporting the factual elements we have been able to gather (from the bea report) and makes some modest proposals for corrective actions which seem to us to be, at minimum, pertinant in the context of the information we presently have.

Well said.

Xeque

3rd Jul 2009, 14:19

The descent from FL330 took 210 seconds. 3 and a half minutes. In other words the terminal velocity of most objects due to gravity.
Now, as has been asked many times in this long and sometimes exasperating thread, why? The airframe is said to have remained intact. But, after the initial burst of automated messages, there was no verbal or electronic contact from the aircraft.
We have an object that appears to have fallen from the sky with normal, gravitational terminal velocity. We have no contact from anyone or anything inside it. There was no attempt (it appears) to prepare for a crash landing in the ocean.
The only explanation that makes sense to me is that they were all incapacitated at the moment of catastrophe whilst still in the cruise.
Now, what to infer from that? I have absolutely no idea and I would suspect that no-one else has either.

stadedelafougere

3rd Jul 2009, 14:22

In the lights of this catastrophe, Airbus seams willingfull to enhance air-to-ground communications to reinforce "flight data recovery" as they announced yesterday.

Airbus has launched a study for reinforcing flight data recovery, including, but not limited to, extended data transmission for commercial airliners, so that in the event of accidents, critical flight information can still be recovered and released to the investigating authorities.

Tom Enders, President and CEO of Airbus commented: “Gathering information from accidents is vitally important to further improve the safety of flying. Various technical means for reinforcing flight data recovery and data transmission to ground centres are principally available. We will now study different options for viable commercial solutions, including those where our experience with real-time data transmission from our own test aircraft could support the further development of such solutions.”

The study will be conducted by Patrick Gavin, Head of Airbus Engineering, and Charles Champion, Head of Customer Services, and will need to address technological issues as well as data protection and privacy concerns. Airbus will include industrial partners, research institutions, and international airworthiness and investigation authorities in this study.

unclemohammed

3rd Jul 2009, 14:22

Follow on from post #2772 ( TU-154 flat spin accident).

From Air Safety Week (Sept 18th 2006), and although focused on T-tail aircraft incidents, some of the findings regarding vertical velocity/ trajectory under stall may be pertinent to the current discussion.

A Tale of Two T-Tails | Air Safety Week | Find Articles at BNET (http://findarticles.com/p/articles/mi_m0UBT/is_36_20/ai_n16729906/?tag=content;col1)

Re: MD82 crash (Preliminary) AUGUST 2006 (WCA708)

Quote (page3):

"the engines wouldn't have recovered until gulping much denser air at the lower altitudes, shortly before impact at their descent rate of over 7000ft/min."

...."According to the Flight Recorder, WCA708 descended at a high angle-of-attack "

Quote (page 4) :

"The descent from FL330 took 210 seconds. The debris field was only 200m long and 110m wide, indicating a near vertical descent with no forward airspeed. The crew had radioed that "both engines had flamed out" but they were merely locked back at flight idle."

Although this makes extremely interesting reading, i think that the T-Tail element of these aircraft mentioned is important. They have chracteristics in which the aircraft can enter a 'Deep Stall' in which certain configuration's of stall upsets can also lose all lift (whether negative or postive) on the horizontal stabilser and elevator as well as the wing. This renders the elevator as useless.

From my days at the flying school and physics lectures, i seem to remember that these upsets are impossible to retrieve from. All T-Tail types are affected, 1-11, MD80 series etc....

I think that AF447 will not have been affect by a 'Deep-Stall', due to the airframe characteristics, but stall scenarios are not fully tested by AB, for the obvious reasons.

I think the idea that big jets cannot (mentioned elsewhere in this thread) spin, is preposterous! The fact that one wing can lose lift quicker than the other one is a factor for all types IMHO and is a function of physics, not engineering.

Maybe there is an argument for can certain big-jet types flat spin, but how would we know, obv. it is not tested, and if types have spun before i could imagine the airframe not standing up to it. I think the idea, that the aircraft might have spun, should be given some creedence. Considering at one moment it was @ FL350, and within a short timeframe, in the water. This combined with BEA's fact (that is how i read it, not an assumption) that the aircraft hit the water relatively flat with a strong vertical acceleration (acceleration = rate of change of velocity over time), combined with a low forward speed, suggest's to me that a stall scenario occured.

Speculative questions from me include:

Why would a normal stall scenario cause this from FL350 or below? considering there might have been enough height to recover...IMHO there would be fugoid osscillation on attitude, splitting between excessive pitching moments in the vertical plane, possibly exceeding overspeed and stall

Given that the type possibly cannot 'Deep Stall' (given by research by test pilots on plenty of airframes), why is there less mentioned that the aircraft may have spun? See my comments above...

Just my two penneth worth...

Unc

Daniel_11000

3rd Jul 2009, 14:42

Reading the French report:, the a/c hit the water ‘en ligne de vol’, the English translation says ‘in a straight line’.
From my knowledge of French technical language, ‘ligne de vol’ means something similar to ‘cruise attitude’, if not even ‘horizontal flight’.
From my knowledge of the English technical language, instead, ‘straight line’ means a ‘linear ‘ movement, with no reference to attitude or altitude (i.e., an unspecified linear trajectory)
I suppose the original, non-translated ‘ French wording is to be considered but , if so, this leaves me with more doubts.
Can French and English mother-tongue friends help me on this subject?
Daniel

einhverfr

3rd Jul 2009, 14:45

First on the interface question.... An interface is just a set of means of inputs and outputs for interaction. Every airplane has an interface which consists of its instrument system and control inputs (yoke, sidestick, etc). These interfaces ARE important and one should not ignore the problem just because the interface is standardized.

Also I think that one legitimate concern about Airbus is that they have sold increasingly complex airplanes as requiring LESS pilot training. In fact, with added complexity, I think MORE training should be required.

Looking at the statistics, it seems however that airplanes are getting safer. One cannot argue that the A330 has a bad safety record at the moment, nor do other airbus planes. Certainly all Airbus planes to date have better safety records than the B747. However, PJ2 is exactly correct that a lot of the argument is prejudice from years of PR on behalf of those opposed to the trends.

This does not mean that this design, just like any other design, does not have it's compromises and problems. Every aircraft design has and it is trite to say or argue otherwise that "one design is superior to another". The record speaks for itself, and no one...absolutely no one, is casting an eye towards the most advance airliner in existence, the Dreamliner, and saying the same things and it is far, far more automated than any Airbus. Prejudice does this.

I dunno. I personally thought the possibility that a passenger might have been able to hack the flight control computers on the 787 might have removed the pilot even more from being in control..... The problem here was interfaces which should not have been available (there should be no access to flight control interfaces from the main cabin)!

edga23

3rd Jul 2009, 14:52

To Daniel 11000 (and all French non-speakers)
Yesterday, I heard an interview of the BEA director on the french radio France Inter. Directly questioned by the journalist about the meaning of his wording "ligne de vol", he clearly explained that the choice of his words was probably not the best, but that he clearly ment "normal attitude" meaning with "wings level" with "no significant roll".
So to close the dabate, and with French my primary language, and having heard the explanation on France Inter directly from the guy, by "en ligne de vol" he definitely ment "normal attitude, with wings level"

Tjosan

3rd Jul 2009, 14:56

From my days at the flying school and physics lectures, i seem to remember that these upsets are impossible to retrieve from. All T-Tail types are affected, 1-11, MD80 series etc....

That's why the MD 80's have ventral fins fitted to the nose section and also to
the outside of the engine cowling's i.e. to be able to handle or avoid a deep stall.

lomapaseo

3rd Jul 2009, 15:06

Again my problem with the subtle translation differences by whom ever between french and english leave me with questions.

1) I accept that the flight path of the aircraft could/would have been in a straight line for most of its descent . Does this match what the BEA meant?

2) I accept that the damages seen to the floating parts imply that they were within the fuselage section when it hit the water. Does this match what the BEA said?

3) I agree that the aircraft struck the water on its belly. Does this match the BEA report?

4) I can not conclude any words attributed to the report what the pitch, roll or actual heading of the aircraft was from the english words. Am I missing something? or are some posters assuming these axis?

5) Inspite of item (2) above is it possible that the aircraft might have broken into two or more large fuselage sections at altitude before hitting the water or do the BEA words preclude this?

Graybeard

3rd Jul 2009, 15:08

The ventral fins (strakes) were not new on the MD-80. They were first fitted on the DC9-50, for stability at cruise. All DC-9 are subject to deep stall. The DC9-80 was fitted with a stick pusher after it became uncontrollable in a deep stall in flight test, and they had to deploy the parachute to recover.

AF447 cg was near the aft limit. It is unknown what would have triggered its apparent flat spin, but it may have not taken a large event in severe turbulence.

Maybe a spin chute could have saved AF447..
GB

SaturnV

3rd Jul 2009, 15:11

ttcse,

one more 02.07 hours image for you/

This is the map of cloud tops with temps -75C or colder. France Meteo's analysis is that there were a few temps of -80C, which would correlate with CB cloud tops of 50,000 to 52,000 feet.

http://i136.photobucket.com/albums/q199/tahitiplage/SNAG-0323.jpg

"On constate qu’à 2 h 07 les températures les plus froides sont de l’ordre de
-75 °C à -80 °C, alors que la tropopause se situe entre les FL500 et FL520,
avec une température voisine de - 80°C"

edga23

3rd Jul 2009, 15:32

First I would wait the official results from the necropsies made by the Brazilian pathologists. Nothing has been made public officially, as far as I know.

Second, you find water in the lungs only if the person was breathing when submerged; they could have been killed instanly when the aircraft impacted. (and yes, I am an MD)

BOAC

3rd Jul 2009, 15:44

edga - have you studied the autopsy reports on the crash of the Air India following a mid-air breakup after a bomb explosion?

4nsicdoc

3rd Jul 2009, 15:54

Even if alive when hitting the water, a laryngeal spasm in reaction to the water can keep water from entering the lungs. That spasm can last quite some time. In the forensic sciences, we have a saying: "The absence of evidence isn't necessarily evidence of absence.

PJ2

3rd Jul 2009, 15:59

Dani;
It's very unlikely that they ditched. It's very unlikely that they glided towards the water for any reason.
Correct. That's exactly what the BEA is trying to convey: level aircraft attitude, vertical trajectory with possible slight forward and perhaps even aft, trajectory, (possible explanation of the condition of the one spoiler found - torn out by reversed airflow, as someone posited a thousand posts ago) - not a straight line down, in other words.

The following are some considerations of other system faults which would likely have developed in any such stalled condition. There is no evidence for these assumptions but they are reasonable, given the vertical descent scenario described by the BEA.

We don't have evidence but may surmise that with such high angles of attack, the engines would have flamed out, (for those not familiar with this and would question this, flameout would be due to the extreme angle between the engine intake cowling and the air passing "upwards" almost at right angles to the axis of the engine. As such, air would not enter the engine in a smooth path).

Therefore, (again an assumption based upon the BEA's scenario), once the stall was fully developed and as engines flamed out, electricity and hydraulics would be lost except for what was available from the two batteries. The APU which has it's own battery could nevertheless not be started both given the time available and the highly disturbed airflow which would obtain in the BEA scenario, (again, roughly perpendicular to the axis of the aircraft).

Under such circumstances (loss of electrical generation on both AC buses), the RAT would deploy but would not supply emergency hydraulic pressure for flight controls or the emergency generator due to the direction of the airflow.

Providing the DC Essential bus was powered by the batteries, the cabin pressure controller would be powered. I can't find in the AMM what powers the outflow valves themselves but one could assume it would be from either the AC or DC essential buses. Perhaps someone can determine this.

With a flameout, airflow from the engines to the two packs would be lost and the cabin altitude would, after some time had passed, slowly begin to climb.

Please NOTE: I doubt very much whether the "Cabin Vertical Speed" ACARS message was generated as a result of engine flameout and consequent loss of airflow to the cabin. Flameout would be an event which would have occurred much later in the accident sequence after the stall was fully developed, again as envisioned by the BEA. (to lay the logic of this out fully...loss of both engines does not cause an immediate loss of pressurization, nor does it even result in a high cabin rate of climb. By the time any significant cabin rate of climb obtained, the capability of sending ACARS messages would have long been lost).

NOTE: These are some considerations of other system faults which would likely have developed in any such stalled condition. There is no evidence for these assumptions but they are reasonable, given the vertical descent scenario described by the BEA.

Duck Rogers

3rd Jul 2009, 16:01

Interesting (to some) though the minutiae of drowning and/or asphyxiation may be we're heading too far into non-PPRuNe territory. Before I start hitting the 'Delete' and 'Thread Ban' buttons would somebody like to try getting this thread back on track?

Duck

steamchicken

3rd Jul 2009, 16:01

Impressive report; equally impressive how many people who were originally convinced that it must have broken up at altitude as a result of evil european computers, yadda yadda, are now even MORE convinced of this after it becomes clear that it didn't break up...all that cognitive bias stuff must be true after all.

ttcse

3rd Jul 2009, 16:03

Duck, I think there might be some confusion as to what is 'too far away from topic'.

Duck Rogers

3rd Jul 2009, 16:03

Not from where I'm sitting there isn't.

vovachan

3rd Jul 2009, 16:10

From my days at the flying school and physics lectures, i seem to remember that these upsets are impossible to retrieve from. All T-Tail types are affected, 1-11, MD80 series etc....

I wonder what the "raw" stall characteristics of an A330 are, sans electronic protections, and whether the manufacturer could have taken some shortcuts in that area, since the plane is "unstallable" anyway...

PEHowland

3rd Jul 2009, 16:12

TiberiusKirk (http://www.pprune.org/members/277090-tiiberiuskirk) said:

While it is indeed possible to extend radar coverage to every part of the globe...

Not with ground/land based radar it isn't. Radar is line of sight and the earth is curved. Even at altitude, an aircraft will often be below the horizon WRT to the nearest land.

Not true. Radar at microwave frequencies (1GHz+) is line of sight limited, but at HF (3-30MHz) propagation is either via refraction in the ionosphere to ranges between 500 and 3500 km (HF Over the Horizon Radar) or typically 0-500km when vertically polarised and over the sea (HF Surface Wave Radar). Thus it is indeed possible to extend coverage to every part of the globe, just not with the typical L-Band or S-Band ground based radars that you are probably familiar with. Several countries have operated or continue to operate HF OTHR systems, although none (as far as I am aware) are providing surveillance over the region of this crash.

Later edit: JDDE you replied (http://www.pprune.org/rumours-news/376433-af447-now-added-preliminary-report-148.html#post5039352) to the above message disputing HF Surface Wave Radar and telling me to learn more about antennas and propagation. I replied to your reply, but this was deleted by the mods. Suffice it to say that I have been a radar engineer for almost 20 years and worked extensively on both of the above technologies. Your comments on NVIS are nothing to do with the technologies I am referring to.

AstraMike

3rd Jul 2009, 16:16

At first I discounted the possibility, but I now have to admit it is beginning to fit, given what has been explained by the investigation.

I cannot help but wonder how many of the Airline Transport pilots here have ever encountered a Flat Spin and, in fact, how may might know anything about recovering an aircraft that just happened to enter such a spin, by mistake. Three dimentional filght (as Duane Cole would put it) is not something that is practiced in airliners, is it?

I dont know, but I doubt anyone has any data regarding the Airbus 330 in any kind of spin; something tells me such out of control excursions are considered a thing of the past, but to return to the point, a flat spin has a descent rate approximately 50% of a conventional spin. Thus, from experience, would not be surprised if the descent rate for the aircraft in question was around 4,000 fpm. Isn't that about 45 mph? I admit it could be more, but depending on many aerodynamic factors it could equally be less. I dont know because I have not deliberately spun an A330, nor have i heard of anyone who has, certainly flying through an area of active CB buildup could be considered a good place to start, especially if you have no reference to speed and found yourself distracted by warnings and without the autopilot so many depend upon these days.

However, impact at a speed in the region of 45mph might just fit with the damage evidence recovered to date, what else does? I submit a full spin descendibg at around 8000 fpm would be too fast to produce the evidence found, a spiral dive even worse and a low level stall just does not seem to explain the apparent torque involved in the removal of the vertical stabilizer, whereas a flat spin, just might. It just might answer other puzzels too

Equally, I suspect no one really knows the attitude of an A330 in a "flat" spin and you should not assume "flat spin" equalls flat or horizontal attitude; it is quite possible that the nose could be above the "horizon" and if that is so it is equally possible that the aft fuselage may contact the sea first...

Sorry, but I couldn't help myself...

Will Fraser

3rd Jul 2009, 16:27

The fuselage impacting 'flat' does not preclude any attitude up to flat impact, including nose up, as the 'tail' may have contacted first, destroying the tailcone and VS mounting hoops, releasing the fin from its forward mount. If there was rotational (radial) movement (not roll), that would explain the 'left' torsional component of the failure. Dragging the tail would slow horizontal velocity, derotate, and allow for a 'flat' aspect at contact (a la Schipol).

Having said that, irrespective of its possibility in fact, it is irrelevant.

The trail still needs unwinding to the moment of loss of control.

PJ2

3rd Jul 2009, 17:14

IcarusRising, post 2889; http://www.pprune.org/rumours-news/376433-af447-now-added-preliminary-report-145.html#post5038394;

It is not uncommon for me to return from rest to find laptops out on the pull tray obscuring flight instruments or sorry animated discussions about work and pay conditions while the aircraft does her own thing an receiving looks of disbelief when voice my concern that monitoring aircraft flight performance and weather conditions mean just that and not getting sucked into complacency and side distractions. I am looked on by some crews as a relic and behind the times !
Yep. I occasionally found the same scene upon return and had the same "relic" feeling. With reduced standards in terms of experience and training, I suspect we'll see much more of the behaviour you are describing, (casual monitoring, laptops out, discussing everything under the sun, etc)

ralphie;
I am sorry to hear that you are retired. I would love to hear that Airbus or Boeing or whoever would grab you as a fantastic teaching authority. That is the same for all other retired captains on this forum. The airline industry should be using you big time!!!
There are a lot of pilots contributing here and who are in the industry with the same and far higher qualifications than I who are retired or retiring and who, because airlines don't pay well enough to attract the kinds of mentors the business needs, are for the most part lost to those coming along. I had a contract for specialized flight safety work for a year and was deemed "too expensive" so that ended that.

We shouldn't leave the impression that the new pilots are a different breed - they're not. They're as keen and as safe as they can possibly be. The key is, they have to have experience in aviation, not in schools which give out airline pilot licenses after 250hrs of simulator and a bit of line training. That's where the problem is. Most guys in my group had thousands of hours before being hired. We sat in the Second Officer's seat for a while if we were lower time, and we learned from the guys up front - the good and the bad. There are schools that can give an MCPL but there aren't mentoring programs, and mentoring only shares attitudes and stories; one must "do", to gain experience and quite frankly because of the way airlines have treated pilots as "expensive resources which need to be beaten down", fewer and fewer young people are choosing the career.

From Eurocockpit "RC analysis, posted by Squawk_ident, post 2897 http://www.pprune.org/rumours-news/376433-af447-now-added-preliminary-report-145.html#post5038676;
-> The descent of the aircraft involves a descent of the altitude of the cabin ordered by the main controller of pressurization (the other being functionally on standby). It is what occurs with each descent so that at the opening of the door, on the ground, the outside pressure is the same than the one inside the cabin. There is thus a regulation of the descent of the cabin altitude as the plane goes down. If the plane would start a very fast descent, the controller of pressurization would try to reduce very quickly the altitude of the cabin. This variation is by design limited to 750 ft/mn, which cannot thus generate an alarm corresponding to a value algebraically higher than 1800 ft/mn. If the plane was not in descent but unfortunately in a fall, it would then join the altitude of the cabin before the controller of pressurization could sufficiently reduce the cabin. In this case, the pressurization would be reversed: the pressure outside the plane would become higher than that of the cabin. To avoid the implosion, “safety valves” and “negative relief valve” open in the event of negative differential pressure (0,25 psi). In this case, the rate of variation of the cabin follows the fall of the plane to minimize the difference in pressure and the rate can thus be much higher than 1800 ft/mn.
This scenario assumes that the engines are running all the way to impact. I doubt very much whether they were and explain why in post #2921, http://www.pprune.org/rumours-news/376433-af447-now-added-preliminary-report-147.html#post5038998

Xeque, post 2902 http://www.pprune.org/rumours-news/376433-af447-now-added-preliminary-report-146.html#post5038792;
We have an object that appears to have fallen from the sky with normal, gravitational terminal velocity. We have no contact from anyone or anything inside it. There was no attempt (it appears) to prepare for a crash landing in the ocean.
The only explanation that makes sense to me is that they were all incapacitated at the moment of catastrophe whilst still in the cruise.
Now, what to infer from that? I have absolutely no idea and I would suspect that no-one else has either.
Contact would likely not be possible. The chaos in the cockpit due to warnings and probable turbulence would occupy the crew for the first minute or two; dealing with a rapidly developing emergency and prioritizing actions, handling a degrading aircraft uncertain of airspeed and probably dealing with the significant shock of what was happening would not permit communications. As dozens of professionals here have pointed out, we "aviate, navigate and communicate" even in such rapidly unfolding circumstances.

As described in the post above, with the possible/probable loss of electrical power after the stall had fully developed, only VHF1 would be available. VHF 1 is usually set to 121.5 when a flight is handed over to air-radio (who in turn, communicate with the ATC unit doing the actual controlling) and, with no CPDLC (google "FANS"), all communications are done via HF communications. There is no way in the circumstances this crew was in, that they would be broadcasting in the blind on HF - they could have broadcast on 121.5 which other aircraft would have heard, but didn't. We can only surmise why but I highly doubt that they or anyone in the cabin were incapacitated due to pressurization issues. Determining if the masks deployed might possibly be done through an examination of the pins holding the doors closed in the overhead panel where the masks are stored - that would indicate that the cabin reached at least, roughly, just over 14,000ft but the BEA said nothing about this. There are such panels in the wreckage.

Will Fraser;
The trail still needs unwinding to the moment of loss of control.
We have at least some clues, but no evidence.

vovachan;
I too was somewhat surprised that other ac were deviating quite considerably to avoid the weather while AF447 seems to have flown in a straight line until the last known position. They never requested a deviation. What is the protocol in that area where comms are flaky if you lose contact with ATC - do you deviate anyway and hope for the best? Stay the course damn the CBs?
Frankly, while none of us was there, I was astonished when I saw the satellite maps of the area, that some course deviation did not take place, and that impression has been subsequently supported by the actions of other flights in the area. Conditions don't change that much in half an hour. I don't think it is wise or fair to begin building a picture of the decision-making process but it is one factor among many that requires examination in my view; - 'nuff said for now.

As far as deviating around thunderstorms in areas of "flaky" communications, you do what you have to do - deviate as necessary to ensure the safety of the flight. You light the aircraft up with all landing lights etc, broadcast intentions on the common frequency, perhaps climb 300 to 500ft if you're really uncertain about traffic and continue to broadcast while deviating. CPDLC is such an improvement in flight safety that it should be mandated by ICAO for all countries which serve communications for international flights.
PJ2

singpilot

3rd Jul 2009, 17:23

First off, THANK YOU DUCK!

This thread went seriously south at post #5.

They flew into a thunderstorm. The A330-203 was at max cruise altitude and at faster than normal mach (because of the high/heavy choice). Mach .82 and encountering moderate turbulence and most likely warming temps when they got a vertical gust of XX knots. Who knows, who cares. Iced pitots? Who knows, who cares, same result. The ADIRU's are programmed to 'fail' with a loss or gain of 60 knots, because that is thought to be impossible. They were entering an area of increasingly worse/impossible conditions for their planned performance prior to encountering/stumbling into a buildup.

The plane stalled. The engine/s probably flamed out/overtemped/burped because the inlet air also vectored off of normal due to the vertical gust. If only one was producing thrust, the plane may have even flatly spun, but it did so in a stalled condition. 208 metric tonnes falling from FL350 after a stall will look the same as a rock. They remained stalled all the way down. Vertical fin and pieces of a horizontal stab were found floating. How much tail remained on the way down? Who knows, not enough, obviously. None of this surprises me. The ACARS messages are nice to have, but fact is, they would be expected in this scenario.

I have flown this EXACT route several hundred times in 37 years, and no prudent aviator is going to ignore the weather in this region.

Sorry to be blunt, but anyone who has ever penetrated an active thunderstorm (for whatever reason) will do whatever it takes to never do it again.

Provided they survive their first encounter.

The Old/Bold rule.

Another small tidbit. Within an hour of the impact 7 other flights went within 100 miles of AF447 that night, and every night since, and not a single one of them has made CNN.

Sorry, I think Occams' Razor applies here.

PJ2

3rd Jul 2009, 17:35

singpilot;
Sorry, I think Occams' Razor applies here.
Yep, and it doesn't paint a pretty picture, frankly.
So there's everything to learn, and nothing to learn...depends upon who's doing the learning. There is the pitot issue and the response, and the broader issues of cascading failures possibly overwhelming crews. I don't think there are structural or engineering issues here. Also, there is some very good thinking along the way to 3000 posts which have been of some benefit to others in our profession.

Tailspin Turtle

3rd Jul 2009, 17:38

Based on my experience as an instrument and aerobatic instructor once upon a time, the easy way to replicate most of what I've recently read here is to lose attitude reference, enter a spiral dive, get going really fast (supersonic is not out of the question), finally figure out what level is, roll to level, and then pull as hard as possible because the altimeter is unwinding or you can see the water is nigh. The result is a high sink rate, wings level*, unsurvivable impact. *fuselage level too, perhaps, depending on the pitch rate of the attempted pullout versus the altitude remaining (added)

L337

3rd Jul 2009, 17:45

Sorry to be blunt, but anyone who has ever penetrated an active thunderstorm (for whatever reason) will do whatever it takes to never do it again.

Amen to that.

The most frightened I have ever been in an aeroplane is in the middle of a thunderstorm, going down. Because I thought I could get over the top of it. I did not get over the top, and because of the turbulence and buffet boundaries had to descend into it.

Only once. Never again.

The satellite weather trace makes the hairs on the back of my neck crawl.

BOAC

3rd Jul 2009, 17:47

The A330-203 was at max cruise altitude and at faster than normal mach (because of the high/heavy choice). Mach .82 and encountering moderate turbulence - I appreciate you do not fly the 330, but you may wish to note that flying at .82 instead of .8 reduces the max (and opt) alt by 2000' and puts it well BELOW 35000 at anything warmer than ISA+17 at the 0210Z estimated weight. I suspect there may be a strong element of 'too high' here with the ITCZ to penetrate - I'm not sure, of course, what manoeuvre margin the graphs posted a while back allow for.

Graybeard

3rd Jul 2009, 17:51

Thanks for the spin info, AstraMike.

If for some reason the cg were aft of the center of lift at time of stalling, the plane would tend to slide backwards, tail low, then level out as the tail gained lift, then do some other dance. I reckon it would be akin to a falling leaf in its maneuvers, rather than like a falling rock, which would indeed retard the descent.

As for stall and spin testing of the A330, I would be shocked if they didn't at least do heavy stalls, with a spin chute at the ready. I'm sure those test results are getting scrutiny right now.

GB

sirgawain123

3rd Jul 2009, 17:56

i´m just a chopper flyer with no experience in airliners, but having read whole thread, there is a question i would like any AB330/340 driver to answer:

With such a heavy aircraft operating near coffins corner, in case of loose of Airspeed indication, Does the SOP procedure (as i recall reading here) of flying a slight nose up attitude and fixed power setting help? or..would it help inducing a stall?

Does SOP for loose of speed indication require a fixed AOA and Pwr setting, or...are those parameters dependant on weight,speed, and height?

24victor

3rd Jul 2009, 17:57

From the English version of the prelim report;

The messages were at least five or six seconds apart, which can be explained by the limited rate of communication by satellite. There are two possible reasons for the longer gaps: either the aircraft did not have any messages to transmit, or it no longer had the means for doing so (loss of satellite communication performance, for example).

and

• the last message was transmitted to the aircraft at 2 h 14 min 28 s and was effectively received,
• the twenty-five messages transmitted by the aircraft were correctly received by the ground station,
• the gap observed between the message sent at 2 h 13 min 14 s and the one sent at 2 h 13 min 45 s is due, at least in part, to a temporary interruption in the communication link between the aircraft and the satellite,
• there were no satellite telephone communications during the flight.

It also clarifies that

17 The reception time given is that of the service provider’s server processor

The messages average six seconds between each one and this, as stated, reflects the timestamp applied at the SITA server, in other words the time received by the service provider, not the time generated.

If you look at the first fifteen messages you'll note they were all generated in the 0210 window, so the cascade was progressing very rapidly.

There are then four messages generated at 0211 and one, the NAV ADR DISAGREE, generated at 0212. Then come the biggies, the PRIM1 and SEC1 faults generated at 0213. There follows a maintenance status message on ADR2 and the CABIN VERTICAL SPEED advisory followed by an uplink message to the aircraft, probably an ACK of the last advisory, which was "effectively received".

The report noted that four transmit cycles were missed from
2h 13min 14s and attributes that, in part, to the aforementioned "temporary interruption" in the satellite link. No mention here of lack of messages to transmit. The most likely causes for this stated interruption (IMHO) would be temporary loss of power to the transmitter or, more likely, the SATCOM antenna being outside of its operating envelope. However, it was back and capable of receiving and transmitting an ACK up until at least 2h 14min 30s (as stated above).

Questions to the ACARS pundits;

1. Why the drop off in message traffic after the 0210 window
2. What is the interpretation of the 0211/0212 sequence
3. At what point would you surmise the upset may have occured.

Rgds.

24V

EGMA

3rd Jul 2009, 17:59

Regrettably 'singpilot' is probably right ...

What we should learn from this, apart from the bleedin' obvious, is that the ACARS weather reporting system needs to become a little more proactive. The absence of messages told us something was amiss, but we didn't wake up to the fact for 6 hours!

Not good enough in this day and age ... it wouldn't have mattered to AF, but what if 100+ had survived a ditching?

It doesn't need more ATC, the infrastructure is there already.

EternalNY1

3rd Jul 2009, 18:51

I have flown this EXACT route several hundred times in 37 years, and no prudent aviator is going to ignore the weather in this region.

Sorry to be blunt, but anyone who has ever penetrated an active thunderstorm (for whatever reason) will do whatever it takes to never do it again.

Provided they survive their first encounter.

The Old/Bold rule.

At this point, this would seem to sum the whole thing up nicely.

The radar returns showing CB tops above 50,000 feet along their route could easily put them in an impossible situation.

fantom

3rd Jul 2009, 18:54

I have diverted around Atlantic CBs by more than 100nm - with or without ATC permission. They can see where I should have been/was anyway.

If the aircraft had been spinning at impact I do not think the fin would have separated as it did; there would have been tortional evidence.

Any tps/structural engineers to back up my opinion?

f

Gringobr

3rd Jul 2009, 18:58

If any of the bodies had watches which stopped at the moment of impact, it might be interesting to know

overthewing

3rd Jul 2009, 19:03

Gringobr, interesting thought, but I'm not sure if digital watches get stopped in quite the same way as the old analogue ones that were so useful in detective stories?

JD-EE

3rd Jul 2009, 19:20

PEHowland commented:
Not true. Radar at microwave frequencies (1GHz+) is line of sight limited, but at HF (3-30MHz) propagation is either via refraction in the ionosphere to ranges between 500 and 3500 km (HF Over the Horizon Radar) or typically 0-500km when vertically polarised and over the sea (HF Surface Wave Radar).To get an idea of the technology (and impact) of over the horizon radar look up the Russian Woodpecker on Wikipedia. There are some nice pictures and pointers to other nice pictures of these abandoned steel yards. The green you see far far below in the Wikipedia pictures are tall evergreens to give you an idea of the scale involved. ( File:Woodpecker array.jpg - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/File:Woodpecker_array.jpg) )

You also need to study radio propagation and antennas a little more. The 0-500km use is called NVIS, Near Vertical Incidence Signaling. It's used for emergency communications quite a bit. It's achieved with low horizontal antennas. Vertical antennas or VERY high horizontal antennas, as with the Steel Yards, are the ones with the low angle of radiation needed for long distances.

JD-EE

edit - added URL.

augustusjeremy

3rd Jul 2009, 19:24

o PROBE PITOT 1+2 / 2+3 / 1+3 (9DA) (2 h 10)
ATA: 341115
Source: EFCS2
Identifiers: EFCS1, AFS
Class 1, HARD
This message, transmitted by the FCDC2 (EFCS2), means that the FCPCs (or PRIMs)
triggered one of the speed monitoring processes: they have detected a decrease of more
than 30 kt in one second of the “polled” speed value. The three ADRs were considered valid
by the EFCS2 at the time the monitoring was triggered, because the prior rejection of an
ADR would have generated a class 2 fault message and there would therefore have been an
asterisk in front of the source. In this case, the “polled” value is the median value.What I get from the text above is:

The BEA seems to admit that this fault might be generated by disagreement between ADRs although it states that such disagreement wasn't yet detected at the time the average of the speeds provided by the three pitots decreased 30kt in one second.

It is very interesting to notice that it is a class 1 fault report and therefore (I suppose) it was generated DIRECTLY by EFCS2 otherwise the term EFCS2 would be preceeded by an asterisc (*). So this fault would not come from the PHC

It might mean that only the speed component of (ADR1 ?) was contradicting the correspondent readings from ADRs 2 and 3 and that other ADR1 output, like altitude, AoA and so on was ok - Then making it possible to point to a probe specific problem - Or it might simply mean that the discrepancies among ADRs were sampled later.

24victor

3rd Jul 2009, 19:25

The FAA is busy positioning to get rid of area radar.....

24V

captainflame

3rd Jul 2009, 19:30

Has anyone read this ?

High Altitude Operations
Supplement #1 to the Airplane Upset Recovery Training Aid
Assembled by the Industry Airplane Upset Recovery Training Aid Team,
October 5, 2008

A MOST interesting piece of airline training litterature....

Put together by a team lead by 2 test pilots specialists at BOEING and AIRBUS.

Great stuff ! and note the date of this revision 2....

It's a bit thick to post here.:O

PPRuNe Towers

3rd Jul 2009, 19:33

But you can read it here:

http://www.flightsafety.org/pdf/AP_UpsetRecovery/AP_Upset_Recovery_Supplement.pdf (http://209.85.129.132/search?q=cache:vxyvIEHbItMJ:www.flightsafety.org/pdf/AP_UpsetRecovery/AP_Upset_Recovery_Supplement.pdf+High+Altitude+Operations+Su pplement+%231&cd=2&hl=en&ct=clnk&client=safari)

Or this link for the full spread of documentation and videos>

Flight Safety Foundation Airplane Upset Recovery Training Aid (http://www.flightsafety.org/upset_recovery.html)

Rob

EGMA

3rd Jul 2009, 19:44

If the aircraft had been spinning at impact I do not think the fin would have separated as it did; there would have been torsional evidence.

Where are the tps/structural engineers to back up my opinion?

I think you'll need a metallurgist and a structural engineer to determine how that VS separated. For what it's worth, I don't buy BEA's forward shear theory at impact.

It will be interesting to know the locations of the power plants, when they are eventually found. Relatively close together would imply she stalled in, widely separated would imply a spin. Not forgetting the fact that she still had another 3 miles to travel post impact.

WillRogers (I think) was right, will still need to know the cause of the upset; the consequences are all too obvious.

fantom

3rd Jul 2009, 19:57

OK,

If it stalled (for whatever reason) and then suffered double flameout due disturbed airflow to the fans then;

lost HYD due no engines/ RAT (which would not work if the aircraft was stalled/ Green HYD had no electrix for the G pump) / much the same for APU then;

had no flight controls (due no HYD);

could not be recovered by the crew in any circumstances.

Pitots + CB have got to be the ingredients and a stall to the sea the outcome.

f

marsk

3rd Jul 2009, 20:08

Hello all,

I've been following this thread since shortly after the accident happened. As a frequent flyer (100K+ miles a year on UAL alone) I have an amateur interest in aviation. My professional interest is in satellite observing systems, both on the development side and regarding technical and regulatory matters involved in getting the data from them out to the users. I am posting here in an attempt to find out whether there is anything that the satellite community in particular can do to help prevent a repeat of what happened here. My apologies in advance if this post is out of line with the purpose of the board.

Reading this thread has been very informative for me, so thanks to all of you who are sharing your knowledge with us. I understand that we still do not know exactly what transpired, and I don't have the qualifications to add to the speculation or hypothesizing about it. Without going into details about that or about who might be at fault, I will for now assume that weather played a primary role. My assumption is very simple: For some reason AF447 ended up in the middle of an active thunderstorm in circumstances that exceeded the combined capabilities of the aircraft and its pilots.

For areas beyond coverage of ground-based radar networks, the best source of information about convective weather is generally the geostationary satellite system. AF447 went down somewhere near 2 deg N, 30 deg W, in an area for which satellite coverage is provided by both the US (GOES-E operated by NOAA/NESDIS) and Europe (EUMETSAT's Meteosat-9). Being of a more recent generation, the Meteosat-9 imager is slightly more capable (12 channels, 15 minute repeat cycle) than the GOES imager (5 channels, 30 minute repeat). From cross-referencing the cloud-top temperatures measured from satellite with the ACARS messages, we now seem to believe that AF447 was in an area of (surrounded by?) Cb's topping out at 50,000+ ft when things started to go wrong. Since these satellite data are processed and disseminated in real time, in principle there ought to have been a way for the pilots themselves to know that, possibly and hopefully before actually finding themselves there. Assuming now that this was not the case, there are two possible reasons: 1. The data aren't acquired and processed fast enough to keep up with the convective development, or 2. The data are not made available to the flight crew.

Concerning the former, it is true that neither of these two satellite systems have image repeat rates meeting the formal requirements adopted by the World Meteorological Organization, namely 10 minute (or better). This can obviously be a problem for very rapidly developing systems and that may or may not have been a factor here. The next generation imager to be flown by the US on GOES-R in the 2015 time frame will - depending on scan mode - be able to provide full-disc imagery every 5 minutes. However, unless these data in some form actually make it all the way to the flight deck they may not be of much help in the kind of situation we are discussing here.

So my questions to those of you who fly transoceanic routes in areas of convective weather are the following:

1. Do you have in-flight access to geostationary satellite images (or to products derived from them, such as instability indices or cloud top temperatures)?

2. If the answer to 1. is yes: Do you consider this useful for instance when crossing the ITCZ? If not, what would you like to see changed in the data you have access to?

3. If the answer to 1. is no: Why don't you ? Is it a communications/aircraft systems issue? ... a data policy issue? ... due to fear of information overload?

Thanks for bearing with me here.

Squawk_ident

3rd Jul 2009, 20:11

If we accept the fact that the aircraft has not altered its course and stayed rather precisely on the UN873, and knowing what was the weather with CBs activity in this area (see various post s, sites or the report etc...) can we imagine one second that the radar might have become inoperative and, in this case, what would have been the various alerts received by the crew and what would have been the ACARS report(s). Sorry but i really can't understand what she was doing here. Also do any drivers here have already noticed one day that their wx radar was freezing or not answering etc...
Just trying to understand...

protectthehornet

3rd Jul 2009, 20:12

are as good as anyone posting here on pprune.

why go into a storm? only if they didn't know the storm was there would they go in.

wondering RADAR imperfections?

And speaking of upsets...wondering if you all remember the chinese 747, lost an engine in cruise...crew didn't notice...autopilot held altitude until airspeed was too slow...bam

they recovered and made a safe landing at KSFO...I personally saw what hapened to the horizontal stabilizer. I can imagine that the airbus 330 might not be quite as robust.

thoughts???????????

forget

3rd Jul 2009, 20:17

And speaking of upsets...wondering if you all remember the chinese 747, lost an engine in cruise...crew didn't notice...autopilot held altitude until airspeed was too slow...bam

Never mind the facts .......

About 1016 Pacific standard time, February 19, 1985, China Airlines Flight 006,
a Boeing 747 SP-09, enroute to Los Angeles, California from Taipei, Taiwan, suffered an inflight upset. The flight from Taipei to about 300 nmi northwest of San Francisco was uneventful and the airplane was flying at about 41,000 feet mean sea level when the No. 4 engine lost power. During the attempt to recover and restore normal power on the No.4 engine, the airplane rolled to the right, nosed over, and entered an uncontrollable descent. The captain was unable to restore the airplane to stable flight until it had descended to
9,500 feet. After the captain stabilized the airplane, he elected to divert to San Francisco International Airport, where a safe landing was made. Although the airplane suffered major structural damage during the upset, descent, and subsequent recovery, only 2 persons among the 274 passengers and crew on board were injured seriously.

barit1

3rd Jul 2009, 20:31

Never mind the facts .......

NTSB clearly attributes the upset to "not minding the store":

http://www.ntsb.gov/ntsb/GenPDF.asp?id=DCA85AA015&rpt=fi

FINDINGS:
...
8. AIRSPEED - NOT MAINTAINED - PILOT IN COMMAND

falconer1

3rd Jul 2009, 20:58

marsk asked

1. Do you have in-flight access to geostationary satellite images (or to products derived from them, such as instability indices or cloud top temperatures)?

2. If the answer to 1. is yes: Do you consider this useful for instance when crossing the ITCZ? If not, what would you like to see changed in the data you have access to?

3. If the answer to 1. is no: Why don't you ? Is it a communications/aircraft systems issue? ... a data policy issue? ... due to fear of information overload?

1. Guess most airlines do not yet have it. Those products are available already via satcom data to several bizjets and can be displayed via various means in the cockpit..as most modern airliners can be equipped the same way.. the technology is here and the providers of said products are here

2. It IS useful on a strategic level for weather zones as the ITCZ. Strategic meaning in this case, as being able to see developments hundreds of miles away, which is not possible with radar and plan accordingly

on a "tactical" level, i.e. weather avoidance 50 to 100 miles ahead radar still is more useful, but again, if the strategic avoidance is better with the sat products, your final tactical avoidance may be easier too and may yield better results at times..

3. There should not be any big data communication problems and looking at a sat picture should not pose any data overload..

so, yes, everybody should have it..

should make life out there a tiny bit easier

the technology is out there, no problems, and costs should not be an issue..

DingerX

3rd Jul 2009, 20:58

Marsk -- somewhere in this thread, someone with some experience points out that such real-time satellite data is not available on most flight decks.

Everyone reading the english version of the BEA report should check out the French version for the graphics (which presumably make up the bulk of the 10 megabyte difference in file size): there are some impressive reconstructions of the storms based on the 0207 and 0215 satellite shots, with the 0210 ACARS position report superimposed.

If anything comes out of this accident, I'm betting it's systematic training on the use of weather radar and making near-real-time satellite weather info available in-cockpit.

Another thing -- the report puts the CG at around 37-38% aft at the time of the accident. Any sort of spin I assume would kill the engines. Am I mistaken in assuming that, even if the RAT works there (which it's not designed to do), you'll be in direct law, where elevator control is by trim only?

also, JD-EE: Yes. Pedantry is appreciated! And to everyone else: professionals in the field call him William of Ockham, or just "Ockham", hence "Ockham's Razor." The name is based on his birthplace in Surrey. I understand that some of you might have wasted some time stooging about there. We have that in common.

Mad (Flt) Scientist

3rd Jul 2009, 21:10

Another thing -- the report puts the CG at around 37-38% aft at the time of the accident. Any sort of spin I assume would kill the engines. Am I mistaken in assuming that, even if the RAT works there (which it's not designed to do), you'll be in direct law, where elevator control is by trim only?

I believe that direct law still controls the elevator. It just has a very simple (hence "direct") control relationship between sidestick and elevator, whereas the various higher-order control schemes are a bit more sophisticated. What you're thinking of is the backup system if all the PRIMs and SEcs go u/s. (apologies for not using the precise terminology, I'm going to go find it now if I can)

OK, found it again, full explanation here (http://www.airbusdriver.net/airbus_fltlaws.htm) of the control scheme

DIRECT LAW
Direct law is the lowest level of computer flight control and occurs with certain multiple failures.

* Pilot control inputs are transmitted unmodified to the control surfaces, providing a direct relationship between sidestick and control surface.
* Control sensitivity depends on airspeed and NO autotrimming is available.
* An amber message USE MAN PITCH TRIM appears on the PFD.
* If the flight controls degrade to Alternate Law, Direct Law automatically becomes active when the landing gear is extended if no autopilots are engaged. If an autopilot is engaged, the airplane will remain in Alternate Law until the autopilot is disconnected.
* There are no protections provided in Direct Law, however overspeed and stall aural warnings are provided.
* The PFD airspeed scale remains the same as in Alternate Law.

augustusjeremy

3rd Jul 2009, 21:19

o ADIRU2 (1FP2) (2 h 11)
ATA: 341234
Source: IR2
Identifiers: *EFCS1, IR1, IR3
Class 1, HARD
This message has not been fully explained at this stage of the investigation. It was generated
by IR 2, but it is possible that the correlation window had been opened by EFCS 1 via a
class 2 message.Maybe the related message is

o FCPC2(2CE2)/WRG:ADIRU1 BUS ADR1-2 TO FCPC2 (2 h 10)
ATA: 279334
Source: *EFCS1
Identifiers: *EFCS2
Class 2, HARD
This message indicates that FCPC 2 no longer considers as valid the information that is
delivered to it by ADR 1 (via bus 2). The ATA code beginning with 27 indicates that the fault
was not detected by any other FCPC during the three seconds that followed (otherwise this
message would have been classified ATA 34). This message has not been fully explained at
this stage of the investigation.

switched roles ?

marsk

3rd Jul 2009, 21:34

DingerX wrote:

Marsk -- somewhere in this thread, someone with some experience points out that such real-time satellite data is not available on most flight decks.

Thanks. The fact that someone had already pointed out the absence of real-time satellite data had escaped me, but given much of the discussion of the limitations of the onboard radar I am not surprised.

falconer1 wrote:

1. Do you have in-flight access to geostationary satellite images (or to products derived from them, such as instability indices or cloud top temperatures)?

2. If the answer to 1. is yes: Do you consider this useful for instance when crossing the ITCZ? If not, what would you like to see changed in the data you have access to?

3. If the answer to 1. is no: Why don't you ? Is it a communications/aircraft systems issue? ... a data policy issue? ... due to fear of information overload?
1. Guess most airlines do not yet have it. Those products are available already via satcom data to several bizjets and can be displayed via various means in the cockpit..as most modern airliners can be equipped the same way.. the technology is here and the providers of said products are here

2. It IS useful on a strategic level for weather zones as the ITCZ. Strategic meaning in this case, as being able to see developments hundreds of miles away, which is not possible with radar and plan accordingly

on a "tactical" level, i.e. weather avoidance 50 to 100 miles ahead radar still is more useful, but again, if the strategic avoidance is better with the sat products, your final tactical avoidance may be easier too and may yield better results at times..

3. There should not be any big data communication problems and looking at a sat picture should not pose any data overload..

so, yes, everybody should have it..

should make life out there a tiny bit easier

the technology is out there, no problems, and costs should not be an issue..

Thanks. Given that a strategic deviation from the planned track should be less onerous in terms of time and fuel than a tactical one, there should be some value in having the satellite data available also for that reason. I hadn't thought of that.

My point was that the satellites (passive vis/infrared measurement) see something totally different from what the radar (active microwave measurement) depicts. The radar basically shows precip, the satellites show cloud top temperatures and in some cases pre-convective instability. Next generation geostationary satellites are planned to carry lightning mappers showing cloud-to-cloud lightning, thus providing yet a third source of information about convective weather. For the US this is considered a done deal, for Europe this could conceivably still fall apart due to funding issues.

The technology is clearly there so if cost is not an issue, what is preventing airline flight crews from having access to these data?

AMF

3rd Jul 2009, 21:59

singpilot

This thread went seriously south at post #5.

They flew into a thunderstorm. The A330-203 was at max cruise altitude and at faster than normal mach (because of the high/heavy choice). Mach .82 and encountering moderate turbulence and most likely warming temps when they got a vertical gust of XX knots. Who knows, who cares. Iced pitots? Who knows, who cares, same result. The ADIRU's are programmed to 'fail' with a loss or gain of 60 knots, because that is thought to be impossible. They were entering an area of increasingly worse/impossible conditions for their planned performance prior to encountering/stumbling into a buildup.

The plane stalled. The engine/s probably flamed out/overtemped/burped because the inlet air also vectored off of normal due to the vertical gust. If only one was producing thrust, the plane may have even flatly spun, but it did so in a stalled condition. 208 metric tonnes falling from FL350 after a stall will look the same as a rock. They remained stalled all the way down. Vertical fin and pieces of a horizontal stab were found floating. How much tail remained on the way down? Who knows, not enough, obviously. None of this surprises me. The ACARS messages are nice to have, but fact is, they would be expected in this scenario.

I have flown this EXACT route several hundred times in 37 years, and no prudent aviator is going to ignore the weather in this region.

Sorry to be blunt, but anyone who has ever penetrated an active thunderstorm (for whatever reason) will do whatever it takes to never do it again.

Provided they survive their first encounter.

The Old/Bold rule.

Another small tidbit. Within an hour of the impact 7 other flights went within 100 miles of AF447 that night, and every night since, and not a single one of them has made CNN.

Sorry I think Occams' Razor applies here.

I'm in agreement. The theory that something must have failed/iced over/ blah blah is being focused on by those who are ignorant of what an inadvertent CB or bona fide severe turbulence encounter can mean in terms of indicated air data and very real aerodynamics if you're too high and too heavy.

Everything about this event points to a loss of aerydynamics/jet upset, most probably due to convective activity, and not a coincidental instrument or mechanical failure. ACARS messages have only served as a tail to wag the dog for 80% of this thread, IMO. Like you say, those ACARS messages would be expected in that scenario.

CBs and airplanes don't mix, period.

augustusjeremy

3rd Jul 2009, 22:11

Like you say, those ACARS messages would be expected in that scenario.

With an ultra super strong phased array antenna capability.

Just imagine it sending data two, three minutes after the reported faults in the midst of a flat spin. :eek::eek::eek::eek:

Machaca

3rd Jul 2009, 22:17

Working links for Flight Upset Training Aid videos:

Part1 (http://www.tc.faa.gov/acb300/video/upsetrec1.wmv)

Part 2 (http://www.tc.faa.gov/acb300/video/upsetrec2.wmv)

Will Fraser

3rd Jul 2009, 22:19

In the absence of information another possibility? It is easier to assess the things that data suggest, especially when the alternative would be to impugn or call into question the skill of the crew, and that without data.

It is why I wanted there to be no Horizon on the panel, with it, one assumes there was a way out. I have been borne by winds that treated me and the a/c as if I was a feather, and landed white as a sheet. I resist the thought the crew may have entered a bad one, I know the feeling. Hope this isn't histrionic.

Will

falconer1

3rd Jul 2009, 22:55

marsk

The technology is clearly there so if cost is not an issue, what is preventing airline flight crews from having access to these data?

fresh sat charts in the cockpit ...

well, honestly have no idea??

you would not even need any big expensive "certified" installations, just take your lap top in the cockpit, most modern airliners have high speed data internet access via satcom, here you go...

beats me why it's obviously not yet the norm..??

but I am sure, nobody will leave home without it a couple of years from now..

Graybeard

3rd Jul 2009, 23:17

The newest Wx radars from Collins and Honeywell do automatic tilt and scan, and can see when the plane is headed into dangerous Wx. All the designers would have to do is to engage the Windshear Warning light when storm entry is imminent, to be sure the pilot has not turned down the intensity on his display to where he can't see what's coming, as related by ekLawyer in a prior post here.

Info on these radars is in Techlog.

Unfortunately, airlines have the frugal habit of buying only systems that have been mandated, and so 40-50 year old radars are still flying in revenue service.

It would be nice to know what system AF is flying on their A3xx fleets. They might be flying transceivers that are only 25-30 year old technology, as those meet the minimum requirement, and hence are basic fit on new planes.

GB

SaturnV

4th Jul 2009, 00:30

Graybeard, from the report

Air France Airbus A330 aircraft are equipped with the Collins WXR700X radar. The radar image is presented on the NDs superimposed on the other information. It can detect precipitations in liquid form greater than 1 mm/h as well as wet hail. Thus, cloud systems made up of drops of water starting from a certain size can be observed but the radar cannot detect dry particles of ice, hail or snow with a diameter less than three centimetres.

In use, the radar beam has a narrow aperture angle of 3.4°, which means that it is necessary to adjust the TILT (angle between the horizontal and the middle of the beam) accurately, in particular according to the maximum range selected at the ND (RANGE): 160 NM for look ahead, 80 NM for avoidance.
The GAIN adjustment (amplification of the return signal) is normally "calibrated" (in the CAL position) to prevent saturation. However, a manual selection can be made.

A turbulence detection function (for the zones of precipitations in liquid form) is available (in the WX+T or TURB position) in a radius of 40 NM, whatever the RANGE chosen at the ND.

When cruising above 20,000 ft, a slightly downwards adjustment of the TILT is recommended so that the ground echoes only appear on the ND at the limits of the furthest range markers.

SaturnV

4th Jul 2009, 00:34

p51guy, one co-pilot had 4,500 hours on type, >3x more hours on type than the captain. The other co-pilot had 800 hours on type. Hours are approximate.

Flyinheavy

4th Jul 2009, 01:46

I am following this thread like the first A447 Thread from the very beginning. I am amazed how this speculation of entering a "monster CB" is beeing posted in a nearly constant frequence. Untill now there is no evidence for this.

I have seen other maps showing A447 as already outside the weather at 0214UTC. As far as I have seen no mention to entering a CB has been written in the BEA report.

With a difference of about 20 minutes LH507 did fly the same AWY and only diverted by 10NM, if I remember well. Many of you were claiming, that this 'monster CB' would have to be avoided by a lot more.

I do belive only the DFDR could tell us that part of the story.

I personally saw what hapened to the horizontal stabilizer. I can imagine that the airbus 330 might not be quite as robust.

I really do have a problem with statements like this. I would not think we are comparing planes here. Are you aerospace engineer to have such a strong oppinion about the structural strenght of the A330's tailplane?

You may delete this, but I had to write this.......

AMF

4th Jul 2009, 04:08

Flyinheavy CB scenario

--------------------------------------------------------------------------------
I am following this thread like the first A447 Thread from the very beginning. I am amazed how this speculation of entering a "monster CB" is beeing posted in a nearly constant frequence. Untill now there is no evidence for this.

I have seen other maps showing A447 as already outside the weather at 0214UTC. As far as I have seen no mention to entering a CB has been written in the BEA report.

With a difference of about 20 minutes LH507 did fly the same AWY and only diverted by 10NM, if I remember well. Many of you were claiming, that this 'monster CB' would have to be avoided by a lot more.

I do belive only the DFDR could tell us that part of the story.

What are you talking about? Who says it would have to be a "Monster CB" to cause a jet upset for a high and heavy aircraft? 35000' is barely chest-high on an average CB, and moderate to severe turbulence can and does exist 5000' above a developing one, well in the clear of any visible cloud water vapor, and therefore even further above tops calculated by radar returns.

Every CB is a "monster" when it comes to potentially wreaking havoc with aerodynamics and air data. A 10-mile diversion is still a diversion. With developing CBs commonly having growth rates between 5'000 and 10,000 fpm (as measured by water droplets, which lag) a 20 minute difference in a convective, dynamic area can mean the difference betweeen safely transiting the area and having absolutely nowhere to go.

Furthermore, you don't have to be inside the contouring returns shown on airborne radar to experience localized areas of moderate to severe turbulence due to not only vertical, but also horizontal shearing in such a dynamic area, and anyone flying around them enough knows this. Developing cells, which often produce the worse updraft/turbulence, frequently offer little radar return at all compared to mature or dissipating cells nearby and have the fewest visual cues (like frequency of lightning) if its night or when the cells are obscured/imbedded.

The same goes for sudden and transitory temp increases aloft in these areas with such convective activity. Put the wrong combination of turbulence and temp together when you're high and heavy with narrow buffet margins/low performance/degraded maneuvering ability as limited by load factor, and the can of worms can quickly be well-opened.

Like someone else wrote..Occam's Razor. You can say there's "no evidence" for this yet jet upset is a very real thing with very real incidents and/or accidents, and the heightened potential for a high and heavy aircraft in an area of severe weather experiencing it is the 1,000 pound gorilla hanging over this event.

Otherwise, you accept that a sudden instrument or mechanical failure just happened to occur at that place and time (in the area of convective activity), was of a type that went around all engineering redundancies, and so sudden and catastrophic that the crew couldn't even transmit a Mayday. To believe that you have to ignore the 1,000 pound gorilla outside the window, and even though nobody makes mystery movies or CSI episodes about the obvious, it's still the high probablity reality compared to some obscure, one-in-a-zillion chance failure.

marsk

4th Jul 2009, 04:23

Flyinheavy wrote:
I am following this thread like the first A447 Thread from the very beginning. I am amazed how this speculation of entering a "monster CB" is beeing posted in a nearly constant frequence. Untill now there is no evidence for this.

I have seen other maps showing A447 as already outside the weather at 0214UTC. As far as I have seen no mention to entering a CB has been written in the BEA report.

...

I would be careful with using "other maps" - or in fact any maps at all - when you try to pinpoint exactly where the plane was with respect to the weather.

The time resolution of the imagery from the two primary satellites covering this area is 15 minutes for one of them (Meteosat-9), 30 minutes for the other (GOES-E). However, the nominal time for the images needs to be taken with a grain of salt. The reason is that satellite imagers are not snapshot cameras but actually use almost the whole 15 (or 30) minute period to acquire their images. I won't go into the details of all the possible scan patterns here, but the point is that the instrument looks at different regions within the overall image region at different instants during the image acquisition period.

So unless you have intimate knowledge of the file naming convention and the data acquisition pattern of the particular imager, you won't know exactly at what time the pixels you see near the last reported position of AF447 in for instance the 2:00 UTC image were really obtained. The offset between the time given on the "map" and the time of the A/C report could in the worst case be up to 15 (or 30) minutes. In terms of horizontal travel distance I'm guessing this could be anywhere in the vicinity of 100 to 120 NM depending on wind speed and direction - and even half of that could make a big difference with respect to being outside the weather or not.

Will Fraser

4th Jul 2009, 04:42

marsk

I agree and it isn't possible to 'shade' the last position relative to the red. Emphasizing or minimizing weather makes no sense. For me the flight and some very bad wx were in the same place at the 'same' time. "Having gotten through the worst" can mean absolutely anything. 'In what condition?' 'Is the position and the perimeter of the wx 'accurate'? 'Weather related' is absolutely the least value one might claim here.

Robert

I do think BEA have an attitude. I also think it is to be expected. The history says authorities put their heads together and share. The autopsy prohibition was harsh, to be honest. When the exact position of debris and pathologies are in, I believe BEA will backtrack, but they have a built in fallback, they weren't privy to all information. Ever CYA.

Dani

4th Jul 2009, 06:56

the plane may have even flatly spun

An airliner can not spin flatly. Even a normal spin is very unlikely. It's more of a spiral.

sky9

4th Jul 2009, 08:58

Just a thought from a retired Boeing pilot.

If the pitot tubes were blocked what is the effect on the actuation of the rudder, in particular if the ASI was indicating too low a speed would the rudder accept higher rudder pedal inputs than would otherwise be the case?

FoolsGold

4th Jul 2009, 10:18

>I do believe the French are trying to spin this,
quite probable
>and the US media is falling for it.
Possibly.

The interim report suggests some deep stall/flat spin situation that was entered due to some combination of weather, weight and balance, erroneous speed information. This slammed onto the water with high vertical velocity but little if any forward motion is said to be supported by the concave failure of the fuselage and the compressive failure of vertical structural members.

Are you able to list the counter-vailing indications and then list whether these indications are based on unsupported news reports or are more factually supported by direct observations.

Failure to inflate a life vest can be attributed to a high velocity vertical impact, a horizontal impact, disorientation due to stress, a conscious desire due to clear-headed decision, etc. Multiple failures to inflate a life vest are consistent with the interim report's views, but hardly substantial evidence of anything.

JuggleDan

4th Jul 2009, 10:20

Robert Campbell,

I'm having a hard time accepting the BEA report considering the forensic evidence. No clothing, Pink/magenta coloring of teeth, and other information from the Brazilians.The BEA did not use any forensic evidence, as it seems they did not have them.

320 driver

4th Jul 2009, 11:01

Dani

An airliner can not spin flatly. Even a normal spin is very unlikely. It's more of a spiral.

Upon what evidence do you base that statement?

Windshear

4th Jul 2009, 11:55

.. and despite of all this theory the flight crew sat back and said utterly nothing to anyone for some minutes, oh what a tangled web the authorities weave ..... Windy

DJ77

4th Jul 2009, 12:02

Precise calculations using the last ACARS position message coordinates (as reported by BEA) show that the crosstrack error (XTK) was 2.95 nm left of UN873 centerline.

Examination of the messages reception times and precedence, assuming equal transmission times, exclude the possibility that the a/c was on track and on course when the AP disconnected.

This can neither be explained by assuming they were using a tactical route offset since these offsets are only allowed right of track.

Hence, I tend to believe there is a strong clue that weather deviations had been in progress when the first cockpit alarms occured.

AstraMike

4th Jul 2009, 12:43

A good question 320 Driver, especially as an inadvertantly entered flat spin is about the only thing that could bring the aircraft to where it ended up at the minimal rate of descent required to produce the evidence found to date.

In other words, a flat spin is the simplest answer that fits the evidence as we know it.

I don't doubt that modern aircraft are supposed to be spin resistant and have all sorts of ways to prevent getting to a stall, but we all know strange things happen in the vertical and horizontal movements in CB buildups and it is not difficult to imaging how a storm could take over and induce a high angle of attack, perhaps yaw, the crew lose control and a flat spin result.

I wonder if either of the crew on duty had any spin recovery training at all? It used to be a requirement for a Private Pilot license, but I hear that is no longer so, perhaps because a spin is an out of control manoeuvre and training is all about control. Equally, who would have recognized a flat spin anyway - would the instruments tell you? How would today's AHRS electronic instrument sensors translate the forces of a spin? It used to be that the only dependable clues were the slip indicator and the rate of turn indicator (turn & bank) and airspeed...

I should add that a flat spin produces an extreme rate of yaw as opposed to a "normal" spin which might make one wonder about the Vertical Stabilizer and that in a spin, at least one wing is stalled, and the two wings are operating at very different angles of attack.

I could go on, but would not want to be distracting by throwing too much aerodynamic fact into the frey.

Graybeard

4th Jul 2009, 12:44

One of the Satellite plots I saw here showed them flying through the last bit of the storm in what could be interpreted as a hook, the classic signature of a tornado.

I thought also one of the other flights around that time had flown a left offset. Not so?

GB

AstraMike

4th Jul 2009, 12:48

at least they saw something they did not like and sought to avoid it?

BOAC

4th Jul 2009, 12:53

One of the radar plots I saw here showed them flying through the last bit of the storm i - let's get this straight one more time! You have NOT seen ANY 'radar plots' becuase there was no 'radar'. You have seen the last ACARS reported position superimposed on satellite images of upper cloud structure and GUESTIMATED flight path from then on. No one, including BEA, knows whether they were avoiding weather or not.

AstraMike

4th Jul 2009, 12:55

Person saying it can’t be done is liable to be interrupted by persons doing it.

AstraMike

4th Jul 2009, 13:03

We do know their track and had they continued on track have a good idea where they would have gone. We would also seem to suppose that the last reported position supports the idea that they did not deviate from track, although none can say this for sure, it is not an unreasonable assumption especially as following aircraft heard nothing from them at all and a deviation is usually announced as a courtesy to others, of whom there were several who found deviation an appropriate exercise.

takata

4th Jul 2009, 13:12

DJ777:
Wx deviations ?
Precise calculations using the last ACARS position message coordinates (as reported by BEA) show that the crosstrack error (XTK) was 2.95 nm left of UN873 centerline.

Examination of the messages reception times and precedence, assuming equal transmission times, exclude the possibility that the a/c was on track and on course when the AP disconnected.

This can neither be explained by assuming they were using a tactical route offset since these offsets are only allowed right of track.

Hence, I tend to believe there is a strong clue that weather deviations had been in progress when the first cockpit alarms occured. Hi DJ777,
If you were using Google-earth for the calculation, as I did two weeks ago, you will notice that the flight plan "flat line" and the flight plan "at altitude (35,000 ft or 10,670 m)" is somewhat slightly moving to the west, making a 2.68 NM separation from the "flight plan center line". The last positional report (2.98, -30.59) is taken from the aircraft GPS which also may be rounded for ACARS sendings and could be affected by another error margin added to GPS one. The other positions (0200, 0150, 0140) that I reported are extracted from BEA reconstructed flight plan as the real coordinates are still waiting to be published yet.

Looking at the map I did from the Meteosat-9 image, which was part of the preliminary documents (6 June) from Météo France in BEA site, one may notice that the 0210 event is taking place exactly where the top of the CB was the coldest at 0208 (then the highest) but nobody can say for sure how it was pictured by the radar below @ FL350. From the last BEA report, it is described that this image was the situation at 0208 instead of 0215 because the area pictured was scanned at this time:
http://takata1940.free.fr/images1/af447meteo.jpg

One may look also at the CB animations made by Météo-France and notice that before departure time and during meteo briefing, this CB wasn't formed:
- Les conditions météo dans la ZCIT vues par Meteosat
(infrarouge, du 30 mai 0h TU au 4 juin 0h TU);
=> Hourly meteo map animation:30.05.09, 00.00 to 04.06.09, 00.00:
http://www.bea.aero/fr/enquetes/vol.af.447/anim4jours.centre.01062009.p12.avi (http://www.bea.aero/fr/enquetes/vol.af.447/anim4jours.centre.01062009.p12.avi)http://www.bea.aero/fr/enquetes/vol.af.447/anim4jours.centre.01062009.p12.avi

- Zoom du 1er juin de 0h à 3h45 TU:
=> 1/4 hour meteo map animation: 01.06.09, 00.00 to 01.06.09, 03.45:
http://www.bea.aero/fr/enquetes/vol.af.447/anim.01062009.00h00.03h45.p14.avi (http://www.bea.aero/fr/enquetes/vol.af.447/anim.01062009.00h00.03h45.p14.avi)http://www.bea.aero/fr/enquetes/vol.af.447/anim.01062009.00h00.03h45.p14.avi

S~
Olivier

takata

4th Jul 2009, 13:48

tubby linton:
One thing that has been puzzling me in the list of failure messages from the aircraft is the reference to FPV flags on both PFD. and no mention of FD flags.
Hi,
It seems to me that both FD were flaged on both PFD respectively at 02.11.00 and 02.11.15 one minute before the FPV flags (02.12.10 and 02.12.16). No?
S~
Olivier

DJ77

4th Jul 2009, 14:26

If you were using Google-earth for the calculation, as I did two weeks ago, you will notice that the flight plan "flat line" and the flight plan "at altitude (35,000 ft or 10,670 m)" is somewhat slightly moving to the west, making a 2.68 NM separation from the "flight plan center line".

Hi, Takata. I didn't used Google (btw, I don't believe it is strict conformal mapping).

I used the official coordinates of the waypoints, the BEA published position received at 0210Z (2.98, -30.59) and Sodano's formulas witch are, I remember reading somewhere, the recommended formulas to use with navigation computers and WGS84.

About satellite weather images, I just understand they are no to be taken as snapshots, so I won't imply anything unless I learn more. However, I think we can see on your map where the following LH flight crossed through the storm.

DJ

augustusjeremy

4th Jul 2009, 14:57

Juggle Dan,

The link on my previous post is the report to Dakar, that BEA said did not happen...Rob21,

Juggle Dan seems to express an acknowledgment it did indeed happen.

Brazil on its side has to admit that there are some officials - "Joe Bean", for instance - that could let all the stuff to the pros downstream instead of showing up personally in live tv with an eye at voting ballots.

You can see that after that episode the airforce and navy officials dealt with the problem in a much more professional way. :ok:

SaturnV

4th Jul 2009, 14:59

Three more images.

The first is the meteorological data reported by EU0046, which had AMDAR installed. AMDAR reports basic meteorology every seven or eight minutes. EU0046 flew through this thunderstorm complex about 30 minutes prior to AF447, at 32,500 feet. (To me, the track looks to be a bit to the left of AF447.) BEA and France Meteo have superimposed the track of EU0046 as of 0206 hours on the satellite image for 0152 hours. As I read the explanation en francais, the text in the box is representative of the CB at 0144 at that position. "La position de l’observation la plus représentative de l’amas est celle de 1 h 44 TU matérialisée par un carré"

(I am guessing that EU is LAN Ecuador.) The BEA report states that BEA has not completed its interviews with the crews of flights other than IB, LH, and AF that flew this route that night, so there presumably will be further reports of actions taken (deviations) or not taken.

http://i136.photobucket.com/albums/q199/tahitiplage/SNAG-0329.jpg

The second image is duration of the coldest temperatures at the top of the CB complex. The abscissa is time from 0007 to 0207. The ordinate is temp in C.

http://i136.photobucket.com/albums/q199/tahitiplage/SNAG-0330.jpg

The third image is the areal extent of various temperature levels within thin the CB complex. The ordinate is 1000 sq km, the abscissa is time from 0007 to 0207.

http://i136.photobucket.com/albums/q199/tahitiplage/SNAG-0331.jpg

Green-dot

4th Jul 2009, 15:00

Equally, who would have recognized a flat spin anyway - would the instruments tell you? How would today's AHRS electronic instrument sensors translate the forces of a spin? It used to be that the only dependable clues were the slip indicator and the rate of turn indicator (turn & bank) and airspeed...

Apart from instrument indications, due to loads, the crew on the flight deck would have been thrown violently forward and to the left or right, depending on direction of the flat spin. Perhaps unable to move at all for periods of time if the rate of spin was high enough.

takata

4th Jul 2009, 15:12

Rob2: To clarify

The link on my previous post is the report to Dakar, that BEA said did not happen... Hi Rob2,
Then, the clarification should be much more detailed than that as, again, I'm suspecting some bad translations and press fuzz over everyone declarations considering what the BEA actually said.

1. Brazilian ATC transcripts are part of the BEA report, Annexe 3, pages 98-101, French document. This brazilian tape dialog is in the BEA report. Then, the BEA can't claim this dialog doesn't exist when it is printed in its report, right?

2. Origin of misunderstanding:
a) Brazilian ATC, for unknow reason(s) under investigation, forget to include DAKAR ATC when the flight plan was dispatched to all concerned air controls, but DAKAR (GOOO) was rightly inserted in the flight plan delivered by Air France to Brazilian ATC.

b) As a consequence of a), DAKAR ATC could not create AF447 on its system because they lacked the informations (like aircraft immatriculation, codes, etc.). After Brazilian calls, DAKAR created manualy this flight on their system, but without the necessary flight plan informations.

c) As a consequence of b), AF447 ASD-C could not logon to DAKAR and was rejected at 0133, 0135 & 0201. At the same time, DAKAR radio problems (confirmed by other flights) prevented that any contact could be made between DAKAR ATC and AF447.

d) as a consequence of c), no contact being ever made between DAKAR ATC and AF 447 meant that no official transfer existed between Brazilian and Senegalese controls. The Brazilian control was still in charge of the flight until the flight could make a contact with its next ATC.

3. It doesn't mean that ATLANTICO didn't give DAKAR AF447 estimated time to TASIL with speed and altitude.

S~
Olivier

einhverfr

4th Jul 2009, 15:39

I say again, don't get too wrapped up in simplified theories about pitot tubes.

Indeed, I haven't been able to find any previous case of an airliner being downed in cruise phase by obstructed pitot tubes. There have been cases where uncommanded descents have occurred, but no actual crashes. IMO, pitot tubes are likely to be a factor, but one which can only down a plane in cruise phase when combined with other factors, some of which may be more serious than the pitot tube icing itself.

"This problem has been known for 15 years" is something that gets repeated a lot, but even granting such a point (and IMO the problem has been known for a lot longer), in 15 years, it has not resulted in a problem similar to this one.

SaturnV

4th Jul 2009, 15:44

takata, I see no reference that Atlantico asked AF447 to contact Dakar.

01:35:15 AF447 -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.

01:35:38 Atlantico Acionamento do código SELCALL

01:35:43 AF447 -AIR FRANCE FOUR FOUR SEVEN, thank you. [This is the last radio communication from the crew.]

01:35:46 Atlantico -Welcome, maintaing flight level three five zero,
say your estimate TASIL?

01:35:53 Atlantico -Say your estimate TASIL?

01:35:59 Atlantico -AIR FRANCE FOUR FOUR SEVEN estimate TASIL?

01:36:14 Atlantico -AIR FRANCE FOUR FOUR SEVEN say your estimate
TASIL? [This is Atlantico's last attempt to communicate with AF 447.]

Dakar apparently made no attempt to contact AF447 before 0354, when Dakar told Cape Verde it would attempt to contact. It appears that Dakar actually made no such attempt, because Cape Verde subsequently asked Dakar at 0408 where was AF447? and Dakar then asked AF0459 to try and contact AF447. (One has to wonder about the capability of Dakar control.) The BEA report acknowledges that the record is still fragmentary, but the published record includes no information of an attempt by Dakar to establish radio contact with the crew.

AF447 did not provide an estimate for Tasil in the selcall message,and did not reply to subsequent requests from Atlantico for the estimate. Were they considering a deviation after Oraro, and thus re-estimating Tasil? Aside from the SIGMETS, at 0031 dispatch sent the following message:
“BONJOUR AF447
METEO EN ROUTE SAILOR :
o PHOTO SAT DE 0000Z : CONVECTION ZCIT SALPU/TASIL
o PREVI CAT : NIL
SLTS DISPATCH”,

augustusjeremy

4th Jul 2009, 15:50

a) Brazilian ATC, for unknow reason(s) under investigation, forget to include DAKAR ATC when the flight plan was dispatched to all concerned air controls, but DAKAR (GOOO) was rightly inserted in the flight plan delivered by Air France to Brazilian ATC.a) The FAB states it is a periodic flight plan and that it was sent to DAKAR ATC

b) The FAB also states that there is an agreement between Brazil and Senegal providing that after three minutes from the estimated time for a given a/c to enter the area under DAKAR jurisdiction from the Brazilian one and vice-versa, the control is considered to be transfered to that jurisdiction without any further communication. And as DAKAR ATC didn't seek any information from ATLANTICO long after that estimated time the flight already was, officially, under DAKAR FIR control.

AstraMike

4th Jul 2009, 15:55

"from instrument indications, due to loads, the crew on the flight deck would have been thrown violently forward and to the left or right, depending on direction of the flat spin. Perhaps unable to move at all for periods of time if the rate of spin was high enough."

Why all the violence? Surely there is enough in the turbulance to satisfy your worst nightmare? In a spin the bigger the airplane the less violently it behaves - to a point and, by the way, centrifugal force builds in a flat spin with both wingtips pulling towards the horizon, which is why it is a spin and not a continuing roll.

If you think about what you wrote there is little difference between what you say and what might be found in severe turbulance - I might submit that you could stall an airliner and enter a spin, in conditions of severe turbulance, without even noticing any change to your discomfort and the real point is that there is little, if anything, that will tell you something else has happened - except, perhaps, systems will start shutting down.... including engines, at the high angles of attack associated with the situation. So it is not impossible that some of this might be passed along via ACARS and much of it... not.

Ciao

serpilot10

4th Jul 2009, 16:00

http://www.aviaciondigitalglobal.com/newsFiles/20090702022842-4.pdf

takata

4th Jul 2009, 16:11

SaturnV:
takata, I see no reference that Atlantico asked AF447 to contact Dakar.
Yes, you are totally right, my bad. I kept note too fast and it was a communication between Atlantico and Dakar, not with AF447.

When one take a step back, this event happened in this area at the worst place possible. No radar coverage and exactly at the juncture of two ATC on separate continents with poor communications. I'm not blaming the Brazilian or Senegalese but this was not the best place to lose an aircraft for hours.

S~
Olivier

John47

4th Jul 2009, 16:16

There has been some discussion about why the a/c appeared not to have diverted around the CB.
The Captain had carried out sixteen rotations in the South America sector since 2007 and the co pilot had performed 39 rotations on the South America sector since 2002. Both I think would be use to avoiding CBs.

I see that
1.9.1. p 33

At 1 h 35 min 38 s, the ATLANTICO controller sent a SELCAL call.
At 1 h 35 min 43 s, the crew thanked the controller.
At 1 h 35 min 46 s, the controller asked them to maintain an altitude of FL350 and to give a
TASIL estimate.
Between 1 h 35 min 53 s and 1 h 36 min 14 s, the ATLANTICO controller asked the crew
three times for their estimated time passing the TASIL point. The crew did not answer.

It appears that there were no further voice communication after that time, only ASD-C and ACARS.

I wonder whether the problems they experienced may have started just after 1 h 35 min 43

JuggleDan

4th Jul 2009, 16:19

takata,

Thanks for correcting me. Indeed, the interim report fully details the various communications that took place, and I don't think the BEA is denying them in any way.

However, the interim report states that (English version p.32):
At 1 h 46, the DAKAR controller asked the ATLANTICO controller for further information regarding flight AF447 since he had no flight plan
During the press conference, the BEA slides (http://www.bea.aero/fr/enquetes/vol.af.447/presentation.du.rapport.d.etape.20090702.pdf) stated the following:
No transfer from ATLANTICO to DAKARFrom the Journal du Dimanche (http://www.lejdd.fr/cmc/societe/200927/af447-pas-d-explosion-en-vol_225297.html) (beware, French tabloid...), it seems that this point was strongly emphasized during the press conference:
The aircraft was neither in contact with Dakar nor with Brazil, "said Alain Bouillard." This is obviously today among our major concerns and areas of investigation. We want to understand why it took so long between the last radio contact and the initiation of the searchFrom then on, the meaning was slightly changed from repetition to repetition, from copy to paste, and from translation to translation as below (http://www.estadao.com.br/noticias/cidades,controladores-do-brasil-nao-avisaram-o-senegal-sobre-o-voo-447,396790,0.htm):
Brazil ATC did not notify Senegal regarding flight 447From then on, the saga could live a life on its own...

takata

4th Jul 2009, 16:34

John47:
I wonder whether the problems they experienced may have started just after 1 h 35 min 43 It may be infered that communication problems started at this point because she didn't answered those three calls from Brazilian ATC. But her SATCOM worked fine until 0214 and nothing from the flight parameters published may imply that she had other trouble than communication ones until 0210. Beside, communication issues are usual and nobody worried seriously about it. Aircraft are routinely suffering radio problems mainly due to the ITCZ weather. Routine issues are killing awareness, then no alert was issued until very late.
S~
Olivier

DJ77

4th Jul 2009, 16:55

The AF crew probably switched too quickly to selcall watch after it tested OK and did not hear the controller's request.

I wonder why the BEA report does not states whether Atlantico tried to raise AF447 on selcall, during or after their three unsuccessful attempts to get their TASIL estimate, or just dropped the concern.

SaturnV

4th Jul 2009, 17:20

DJ77, possibly because Atlantico was talking with Dakar at the time about AF447.

At 0135, Atlantico is giving Dakar AF447's flight plan including an estimate for Tasil at 0220. At 0135:45, Dakar says to Atlantico, "-Ok, call you back, please." At 0135:46, Atlantico replies, "-Ok, ok, no problem."

Dakar called Atlantico back at 0140, and created a virtual flight plan.

About 2 1/2 hours later, things get stirring in the various ATCs over the lack of contact with AF447, which by this time should be under control of Cape Verde ATC. The concern is initiated by Cape Verde, and as the printed transcript does not convey inflection, one can't say whether Cape Verde was a bit incredulous about Dakar's que sera que sera insouciance.

The BEA report contains this paragraph re: Dakar.
"At 5 h 09 min 15 s, the ATLANTICO controller asked the DAKAR controller if he had any news of flight AF447. The DAKAR controller replied that he hadn’t and then the ATLANTICO controller requested confirmation that the flight was already in the SAL FIR. The DAKAR controller replied: "yes, no worry". He also confirmed that SAL had not established contact with flight AF447."

einhverfr

4th Jul 2009, 17:21

Carjockey:

Well I would like to believe that, but without benefit of CVR/FDR, just how did BEA establish this "fact"?

By carefully analysing the wreckage. However, this makes sense to a large extent. The previous choices were breakup in flight or high-angle, high-speed impact. A belly-first impact would show quite patterns in the aircraft debris.

vittorio66

4th Jul 2009, 17:32

The BEA says:
last radio exchange between the crew and Brazilian ATC occurred at 1 h 35 min 15 s. The airplane arrived at the edge of radar range of the Brazilian control centres, at 2 h 01, the crew tried, without success for the third time, to connect to the Dakar ATC ADS-C system,
No ATC messages were received or transmitted by F-GZCP. Only three attempts were made to connect up to the Dakar centre ADS-C system and were recorded on 1st June at 1 h 33,
1 h 35 and 2 h 01.

What was the last known crew action? At 2h01z or at 1h35Z? It seems that during the emergency initiated at 2h10z the crew took no action, what leads to the possibility of crew total incapacitation (depressurization, or any gas like CO???). Its a possibility to be investigated? This could explain why the flight did not any evasive action to the weather conditions and also the way it impacted the water. This is also coerent with no preparation to any emergency.

DJ77

4th Jul 2009, 17:51

SaturnV, Thank you for your detailed explanations. Actually, I didn't looked closely at the part of BEA's report regarding ATC communications, but I understand BEA's concerns about the apparent delay to scramble emergency researches.

augustusjeremy

4th Jul 2009, 18:06

o FCPC2(2CE2)/WRG:ADIRU1 BUS ADR1-2 TO FCPC2 (2 h 10)
ATA: 279334
Source: *EFCS1
Identifiers: *EFCS2
Class 2, HARD
This message indicates that FCPC 2 no longer considers as valid the information that is
delivered to it by ADR 1 (via bus 2). The ATA code beginning with 27 indicates that the fault
was not detected by any other FCPC during the three seconds that followed (otherwise this
message would have been classified ATA 34). This message has not been fully explained at
this stage of the investigation.

Faulty ADR1 data was detected only by FCPC2 (PRIM 2 ?).

Regarding correlation of messages maybe a given system reporting an external fault (class 2) probably predicts but doesn't command an specific class 1 message.

Which means that a class 2 message may be followed by a class 1 message giving a different diagnostic to the first message.

Once again it is important to notice that apparently only PRIM2 reported the ADR1 fault - Would it be enough to rule out ADR1 to the other PRIMS ?

vovachan

4th Jul 2009, 18:22

The ill-fated Pulkovo 612 crew did not even realize they were spinning until they fell from the clowds and saw what was going on. Before that moment they seemed to think their instruments had gone crazy.

So the forces generated can't be too severe.

takata

4th Jul 2009, 18:24

vittorio66:
This could explain why the flight did not any evasive action to the weather conditions and also the way it impacted the water. This is also coerent with no preparation to any emergency.ACARS are only maintenance messages. So, they won't tell us a lot about what the crew did or did not. Possibly some messages were triggered by crew troubleshooting after 0210. But the aicraft is also fully monitored. Then, until the SATCOM failed, we should be aware that no decompression happened and no poisonous gas was released in the cabin.

"No preparation for an emergency" is not exactly what the BEA mentioned from what was recovered so far. The point was that no life jacket was discovered "inflated" (implying no crash survivor), and this point was particularly weak as nobody would inflate its life jacket until clearing off from the aircraft. It seems way too early to extrapolate the situation of the aircraft passengers and crew before it crashed without knowing a lot more about the forensic evidences or recovering the CVR/FDR.

S~
Olivier

funfly

4th Jul 2009, 18:38

takata (http://www.pprune.org/members/303403-takata), thanks for your last answer. It brings me on to a more relevent point.

There is obviously going to be political mileage in the pitot tube situation.

Consider, the aircraft was on a stable cruising stage at a pressure setting (i.e.not altitude). The pitot tubes may or may not have been iced up but whatever the case this can not have been the catalyst of the disaster as there would have been no obvious indication of this to crew or instruments as the difference pitot/static would have remained the same.

If the pitot heads were iced then they wouldn't have had any adverse effect until speed or FL changed.

In fact the information transmitted about differing pressures between l & r pitots give a very good indication that both were operational.

threemiles

4th Jul 2009, 18:39

(I am guessing that EU is LAN Ecuador.)

EU denotes a European aircraft for AMDAR purposes. Coding does not allow to identify operator to avoid spotting. Altitude report is most likely height over MSL, thus 325 may be something different in FL (FL310,330).

einhverfr

4th Jul 2009, 18:53

A few thoughts after reading the BEA report.....

First, the last ACARS positional message (around the beginning of the rapid degradation of the situation) seems to occur inside a region of strong convection within the larger meso-scale convective system. At this point, I think it is reasonable to ask why pilots flew into "that weather." Does AF require sufficent WX radar training? Are proper procedures (and training) in place to help pilots avoid at least the worst of the weather? From the available data, it does not appear that any weather avoidance was taken.

Secondly, could strong updrafts be a major factor, up to and including the final descent and crash? As I understand it, aircraft stalls are a function of angle of attack, and pitot tubes don't function well at high AoA values. A 50kt updraft at a speed of 447 kts (mach 0.78 at fl350) would add about 6.4 degrees to the angle of attack. (Showing my work: Inverse sine of 50/(447^2 + 50^2)^0.5... is roughly 6.4 degrees) Even with a 3 degree angle of attack, this puts the plane close to an angle where the pitot tubes become unreliable even without icing. Depending on the automated response to the angle of attack, this could get worse very quickly. The main point is though that any pitch up may have rendered the pitot tubes unreliable even without blockages. Oddly this gets back to what Tim Vasquez wrote about turbulance being the primary factor on his list shortly after the incident. In short could a strong updraft have caused a lack of reliable airspeed indications, degraded controls, etc?

Thirdly, what woud the autopilot have done in a strong updraft before disconnecting?

Fourth, assuming AoA was reduced by pitching the nose downward (possibly restoring airspeed data), what would have happened when the airplane went from a strong updraft to a strong downdraft? Could this have also caused a stall of some sort via too low of an AoA?

So this leads to a couple of other questions that are now lurking in my mind:

1) Can we shelve the idea that pitot icing was a factor at this point and focus more on AoA issues?

2) Could the Cabin Vertical Speed advisory have referred to a falling descent? Could this be some sort of stall?

vittorio66

4th Jul 2009, 18:59

Thank you Takata for some explanation, still I have few doubts, referring to the l/jacktes there is no evidence so far that the bodies recovered by the Frigate Ventose had the l/jackets doned , they stating "Clothed and relatively well preserved" no mention what so ever to L/J.
I beleive even if one had the L/J on would tell the investigators that pax where informed or some problem on the A/C.
This what I'm referring as an emergency on board.
About ACARS in the report state that "F-GZCP was programmed to automatically transmit its position approx. every ten minutes"....
Air France received total 26 messages 2 belonging to the previous flight about toilet and 24 received June 1st between 2:10:10 and 2:14:26.
They shouldn't have received also the position more frequently than only one time since the airplane was set to an automatic transmission ?
Also other aircrafts same type had similar situation encountering turbolence but the pilots were able to handle the emergency , the other aircraft did also sent ACARS or were programmed to send them ? Would not beneficial for the investicgators to compare "if possible" ACARS from other planes.
By now I guess you know I'm not a Pilot , I work in transportation field as well but in a different element Water not Air but this unfortunate event opened my eyes about things that I took for granted and now I'm finding out are not.

safetypee

4th Jul 2009, 19:00

IMHO the speculation on a spin, flat or otherwise, is misplaced. There is little evidence to support this; all we have is that the aircraft was most likely in a level attitude moving forward as it hit the sea – nothing of what happened in-between, time scale – when, how or why.

I would like to see referenced evidence of any large aircraft in a stable spin; incipient, yes I would accept. I do not know of any such event and this is not for the want of being in conditions conducive to a spin in commercial aircraft.

Aircraft are built and certificated to withstand inadvertent Cb encounters; they do not automatically stall, nor is a spin an automatic consequence of a stall. Large aircraft tend to depart controlled flight relatively gracefully in comparison small aircraft or high performance fighters. The engines do not flame out in Cbs without other contributions, and all aircraft, with their natural stability can transit the relatively short duration of these events in a reasonable stable manner when the controls are used to maintain attitude.

funfly re #3010, the pitot tubes incorporate a leak path – drain hole. See previous posts for likely icing mechanisms. Drain hole blocked = over pressure - higher airspeed. Pitot blocked (before the drain) = ambient pressure – lower airspeed. All other combinations – fluctuating airspeed.

SaturnV

4th Jul 2009, 19:20

threemiles, thank you.

Is the flight number 0046 also masked; i.e., 0046 is not the actual flight number?

This flight would have preceded LH507 by about ten minutes, and LH507, flying at FL350, deviated west of the track by 10 NM after passing ORARO.

surplus1

4th Jul 2009, 19:42

That's exactly what the BEA is trying to convey: level aircraft attitude, vertical trajectory with possible slight forward and perhaps even aft, trajectory, (possible explanation of the condition of the one spoiler found - torn out by reversed airflow, as someone posited a thousand posts ago) - not a straight line down, in other words.

As usual your post is relevant and well thought out. I don’t argue with your hypotheses but let’s take this a little farther if I may. For starters, I will assume that the BEA report is accurate, i.e., the aircraft struck the ocean in a ‘level attitude” with a near vertical trajectory. Why?

I would suggest that a ‘near vertical trajectory’ (descent) – in a level or flat attitude - is not possible unless both wings are fully stalled – the aircraft isn’t flying, it is falling and there is very little ‘forward motion’. I would postulate further that in such a prolonged “stall” condition a spin of some type, would almost certainly develop. If there was a “spin” there would also be rotation. If there was a conventional spin, the nose would be down – unless the ‘spin’ was a “flat spin” – in which the tail could be down and the nose up with reference to the horizon. The BEA made no mention of “rotation” on impact.

I do not understand how an aircraft can descend with a vertical trajectory if it is not spinning. I do not understand how it can “spin” without rotation. Even if the stick was held full nose up after the stall and throughout the descent, I do not see what wound keep one wing from dropping off at some point and producing a conventional nosed down spin. However, a rearward cg or some other factor could induce a "flat spin" - and that could fit the scenario implied by the BEA.

There has been considerable debate as to whether an airliner can enter a ‘flat spin”. The answer is: YES. How do I know this - Historical record from prior accident(s). [See BOAC 911 and Vladivostok Air 352]

We all know that a “spin” by definition, requires at least two elements: 1) the wing must stall [and remain stalled]; 2) there must be rotation (about the aircraft’s cg.), [and a near vertical descent will follow].

According to NASA, there are four (4) categories (modes) of “spin” classification:

NASA Spin Mode Classification

Spin Mode .................. Angle-of-attack range, degrees

Steep .................................20 – 30
Moderately steep ................. 30 – 45
Moderately flat .................... 45 – 65
Flat .....................................65 - 90

By definition, a “Flat Spin” = A spin in which the tail of the aeroplane drops and the machine rotate (http://en.mimi.hu/aviation/rotate.html)s in an almost horizontal pane. The nose may be slightly below or above the horizon. A rearward CG will augment the tendency to flat spin. The following video illustrates an unrecoverable flat spin in a fighter aircraft.

http://www.youtube.com/watch?v=z7VS9_Ce0sg (http://www.youtube.com/watch?v=z7VS9_Ce0sg)

I am not aware of any transport category airplane that can recover from a fully developed spin - especially a flat spin, or retain its structural integrity within one, given the forces that are experienced.

I do not see how, as inferred by the BEA report, a near vertical trajectory of descent, implying alpha of 65 to 90 degrees, could occur in anything other than a flat spin. Perhaps you or someone else could enlighten me if that is wrong.

In the BOAC 911 accident (a 707-463), it was determined that the aircraft entered an area of extreme (clear air) turbulence. The vertical fin failed and was torn from the aircraft taking other parts of the empennage with it. Subsequently the severe yaw tore the engines from their mounts and the remainder of the structure entered a flat spin until impact. [You have previously posted a photo of that aircraft in descent]. A military fighter sent to search for the wreckage also experienced extreme turbulence – with recorded 9g positive and 4g negative - and temporary loss of control. Its pilot was able to recover but that was a fighter aircraft. IMHO, Airliners cannot survive such forces intact.

In the Vladivostok Air accident (TU-154), the stall was induced by pilot error during the approach and the aircraft entered a flat spin, in which it remained for 22 turns until impact. Unlike the Boeing, this is a “T-tail” aircraft with engines mounted on the rear fuselage (which would likely negate their separation), plus T-tails are susceptible to deep stalls. Also, that aircraft was much closer to the surface when the stall occurred.

IF AF447 entered extreme turbulence, it would have experienced very high g forces, both positive and negative, in rapid succession and most probably stalled. It is likely there would have been severe skidding and slipping as well – all induced by the turbulence. Its pilots would not have been able to prevent this – once the area of turbulence had already been entered. A spin could have resulted – which might have caused the VS to separate – thus creating a “flat spin”. The fin didn’t have to separate by itself – the entire aft tail structure could have separated – somewhere behind the pressure bulkhead. The centrifugal forces would most probably immobilize the crew at least initially.

If there was a flat spin, it is probable that not only the VS could have separated but, the engines would not only have flamed out (as you correctly surmise) but might likely (one or both) have been torn from their mounts – by extreme yaw when the fin/tail separated, or by centrifugal force of the flat spin.

Just as extreme turbulence or a complete stall could disrupt airflow to the engines, [I]could it not also disrupt airflow to the pitot tubes and thus generate the loss of dynamic pressure and the associated errors/warnings (unreliable airspeed, etc.,) [as opposed to icing]? Could not extreme turbulence independently exceed the limitations of the Autopilot and cause it to disconnect - absent other factors? Other components, such as the spoiler to which you refer, may also have been partially deployed and separated.

If either pilot was holding the side stick when the extreme turbulence occurred – could it not have raised his arm violently (negative g) and induced an unintended control input? Anyone who has had an inadvertent encounter with severe turbulence should be able to readily imagine what might happen in extreme turbulence.

At FL350 a CB with tops at FL500 or 550 is quite likely to be capable of producing extreme turbulence. In severe turbulence you might have a change; in extreme turbulence that is improbable.

Do you as an experienced Airbus captain believe that the built in computer ‘protections’ could prevent the aircraft from exceeding either end of its envelope in extreme turbulence? I don’t have the knowledge to guess but I don't believe so. Those things just aren't designed for conditions that are never expected to occur - neither is any other part of the aircraft.

This [flat stall/spin] could then permit the remainder of the structure (fuselage and wings) to descend ‘in a near vertical trajectory’ and strike the ocean in a right side up ‘level aircraft attitude’ – mostly intact – thus explaining the observed ‘compression’ of some recovered parts.

For this to happen, it would seem that the aircraft would also have to exit the area of turbulence – otherwise there is only a 50/50 chance of the falling structure to have remained ‘upright’ during the descent.

The plethora of ACARS messages may have been related to effects triggered by the turbulence – not to pitot icing - and not causal of the incident. I respectfully submit that there is a difference between severe turbulence and extreme turbulence. In the latter the aircraft is not controllable – with or without computers IMO.

We do not know if the aircraft encountered either severe or extreme turbulence, but it is just as probable as any of the other hypotheses. There was certainly weather in the vicinity that could have produced either. IF this did occur, we could well have a logical (though not factual) explanation of everything else.

This is NOT intended to disparage the crew. We do not know if they deviated, if they never detected the wx, or why. There could have been a variety of reasons not related to any failure on their part. I am not willing to judge them without certain knowledge. I am also convinced that they did not intentionally fly into a CB - no matter who was on the flight deck at the time. They were not that inexperienced.

If the ultimate loss of the hull did occur as a consequence of an encounter with extreme turbulence, that in no way reflects negatively on the design or structural integrity of the A-330. No airliner is designed to operate in extreme turbulence. That is why the possibility of such an encounter must be avoided at all cost.

The BEA’s assumption that compression damage observed in the wreckage indicates that the aircraft was “intact on impact” may only be partially correct. Some major parts of the fuselage may well have been intact and the wings still attached at impact. That however, does not preclude separation of other parts in flight. To bluntly state that there was “no break-up in flight” appears to be premature at best. The terminology is highly ambiguous.

Obviously, this is conjecture – but so is everything else that we have explored to this point, including the Preliminary Report

IO540

4th Jul 2009, 19:46

Secondly, could strong updrafts be a major factor, up to and including the final descent and crash? As I understand it, aircraft stalls are a function of angle of attack, and pitot tubes don't function well at high AoA values. A 50kt updraft at a speed of 447 kts (mach 0.78 at fl350) would add about 6.4 degrees to the angle of attack.

I don't think so. If you fly, on autopilot holding a constant pressure altitude, into an updraught, the AP pitches the aircraft down, to maintain the pressure altitude. Your airspeed increases - possibly a lot.

Thirdly, what woud the autopilot have done in a strong updraft before disconnecting?

It will pitch the nose down, and the airspeed will increase rapidly.

Whether the AP will disconnect just because of the updraught, I have no idea but I doubt it.

surplus1

4th Jul 2009, 20:08

Whether the AP will disconnect just because of the updraught, I have no idea but I doubt it.

Like everything else, the AP has limitations. If those limitations are exceeded, whatever the reason, it will disconnect.

Squawk_ident

4th Jul 2009, 20:09

Not at Mach 0.82

Here is a recap from AFR447 actual or estimated. I have put the distance between them.

FEMUR: ACTUAL 0113 (COM at 01.14.31) DIST to INTOL 154NM: 20 Minutes
INTOL: ACTUAL 0133 ( COM at 01.35.15) Estimating SALPU at 0148 and ORARO at 0200
INTOL-SALPU is 122NM 15 minutes and SALPU-ORARO is 122NM 12 Minutes.

ORARO-TASIL IS 119NM and it should be about 11 minutes flight time, the ETO TASIL would have been at/around 0211 not 0220.

Knowing that the last radio contact with AFR744 was just after the SELCAL check at 01.35.43 and that no ETO TASIL was provided to Atlantico, we have to think that Atlantico has given an estimated time based on its own calculation to Dakar.
Another thing is that AFR447 would not have called over SALPU and ORARO but it is compulsory reporting points. Either contact was kept after INTOL with the AF447 and something is missing in the Radiocommunication transcript published in the Report, or contact was lost just after the SELCAL check and Atlantico would have tried to contact him repeatedly and it would be said in the Report.

If my calculation is correct It would mean that crew would have drastically reduced its speed after INTOL.

AirRabbit

4th Jul 2009, 20:11

I’ll try this one more time…
The ventral fins (strakes) were not new on the MD-80. They were first fitted on the DC9-50, for stability at cruise. All DC-9 are subject to deep stall. The DC9-80 was fitted with a stick pusher after it became uncontrollable in a deep stall in flight test, and they had to deploy the parachute to recover.
1) The “strakes” mounted on the DC-9-50 were not mounted for stability at cruise. They were added to the DC-9-50 to improve airflow up and over the fuselage and around the vertical stabilizer to improve directional control during approaches. Up to the addition of the strakes, the DC-9 had a “rudder limiter” system installed that dropped a bracket around the rudder actuator in the tail that prevented the rudder from being displaced more than plus/minus 8 degrees either side of center (as I recall) when the flaps were retracted. On the other end, when flaps were extended, this “rudder limiter” was retracted out of the way, allowing the rudder surface to be displaced plus/minus 30 degrees either side of center (again, as I recall). The pilot annunciator panel had a “blue” advisory light that illuminated saying “Rudder Unrestricted” that had to be illuminated prior to initiating the approach, or the approach had to be flown at substantially higher approach speeds because of the potential limitation of the rudder. This system is still on the DC-9s - 10, 20, 30, and 40 series.

2) While the DC-9 was initially prone to the same malady that befell the French Caravelle – that of deep stall blanking out the tail sufficiently that elevator authority was lost. Therefore, McD widened the horizontal stabilizer, including the ends of the elevators, allowing both to extend out into the airflow that did exist beyond the “blanked out” areas in a deep aerodynamic stall. They also added a 3000 psi assistance to place the elevators into a full nose down position when either flight crew member pushed the control column full forward. Not only was this system successful, it was so successful that the first few pilots landing on contaminated runways and desiring firm nosewheel contact with the surface and pushed full forward on the control column to get it, found themselves “wheelbarrowing” with only the nosewheel on the runway – that is, they actually had so much lift on the tail they actually lifted the main gear off the runway surface!

3) Any “stick pusher” that may have been installed would have been for flight testing only, and I'm not at all sure that ever happened. I am not aware that there was ever a production DC-9 delivered with a stick pusher – they relied on the wider horizontal stabilizer and elevator and the 3000 psi hydraulic system to ensure the elevators were properly positioned to “nose down.” You can still see flight crews testing this system today when taxiing out behind any DC-9 series airplane.

ttcse

4th Jul 2009, 20:43

safetypeeI would like to see referenced evidence of any large aircraft in a stable spin;Lookup Pulkovo 612, a TU-154 I believe.

Apparently stalled then spun from FL390 while trying to fly higher over convective activity but simply entered at a higher level. Very interesting transcript of cockpit conversation can be found.

safetypee

4th Jul 2009, 20:48

surplus1, in recognizing your conjecture I believe that some of the emphasis and the correlations with previous accidents are misplaced; I covered some of these points in #3014.

You discount a stable stall condition where the wings remain relatively level. I proposed an hypothesis leading to this scenario in #2825 http://www.pprune.org/rumours-news/376433-af447-142.html#post5037329
Note that the A330 is reported to have good roll centering in ALTN law, which even with a roll oscillation could result in a ‘level’ attitude and a high descent rate. Hitting the sea at 100kts in a stalled condition, where pitch control might be non existent for a flare is still very fast.

The stalled condition above is not the same as the spin conditions which you and others relate too – the example, and ideas elsewhere invoke the loss of the fin which so far has been shown to be unlikely. Similarly, the example of a T tail stall is not applicable here, but I will check ttcse's reference.

I do not discount control mishandling which could have resulted in a stall / spin, but without evidence, this line of thought cannot be progressed. Also, whilst attesting from experience of Cb test flights, the levels of turbulence can create many hazards, they do not in themselves cause the type of upset or failure which you discuss.
In general, the certification requirements provide for a range of extremes associated with inadvertent Cb encounter, which are based upon extensive aviation history (and accidents). As yet, we only have evidence of the aircraft being close to Cbs and not actually in one.

Many big IFs lead to a range of alternative situations, each viewed by many people with their own views, and unfortunately at times, with bias (but not apparently in your post).
IMHO your analytical logic fails with the assumption that the pitot systems would see different air masses on each side of the aircraft. From experience of tests and often due to the architecture of the pitot systems (cross balance pipes) this occurrence is most unlikely. Also, IF the comparator software detected a cross system failure, then a subsequent comparator failure might then be comparing ‘same side’ systems for the next reported ‘failure’.

Litebulbs

4th Jul 2009, 21:09

That post was like a breath of fresh air. It pulls you back to the FACT that aircraft are fundamentally well designed and safe. Problems may have occurred in the past with T designs, but experience through accidents has allowed procedures to be established, to correct any latent faults in that design.

Large twins have never suffered fatal aerodynamic problems whilst in the cruise, no matter what the weather was doing.

Rananim

4th Jul 2009, 21:13

If either pilot was holding the side stick when the extreme turbulence occurred – could it not have raised his arm violently (negative g) and induced an unintended control input?

I think this may be central and am surprised that it hasnt be discussed more.Sidestick issues(sensitivity,size,position)in turbulence deserve greater focus.

JD-EE

4th Jul 2009, 21:55

DJ77 said: Precise calculations using the last ACARS position message coordinates (as reported by BEA) show that the crosstrack error (XTK) was 2.95 nm left of UN873 centerline.At further risk of being a pedant here I note from the BEA report's ACARS transcripts that the report was in 100ths of a degree latitude and lognitude.

That is a six tenths to 12 tenths of a mile possible error from the truncation or round off process that took place. You quoted an unjustified level of precision there. However, even with that error band it was very slightly to the left of track when you'd expect any pilots even minimally weather aware to be somewhere else.

I also note that altitude, which would be nice to know at this time, was left off the report.

Further I did not see in the report a definitive statement whether the ACARS antenna was an omnidirectional component of the SatCom antenna or whether it had to be precisely aimed at the satellite. That would give an important resolution to the 4 minute give or take a little ambiguity about when the problems started that exists.

If the antenna is omnidirectional or in an omnidirectional mode for ACARS then for transmissions to cease at 0214 one might hazard to guess they were already in trouble at 0210. If the ACARS antenna requires accurate aiming then they were not in trouble until 0214 when they'd have been nearly out of the storm unless they'd become disoriented and turned sharply.

I've been yelled at on this list for presuming both of these antenna propositions. With what I know about SatCom I am inclined to suggest ACARS transmissions would not need a directional antenna to work.

JD-EE

mm43

4th Jul 2009, 22:10

Squawk Indent

If my calculation is correct It would mean that crew would have drastically reduced its speed after INTOL.INTOL to TASIL is 364NM and irrespective of the SALPU ORARO intermediate reporting waypoints, the ETA TASIL was 0220z based on M0.82 FL350 OAT 45°C. This gives a GS of 477NM -10KT headwind = 467KT.

BEA have previously published the auto SATCOM 10 min reports transmitted from departure Rio de Janerio up to and including 0210z. Checking the A/C positions would tend to suggest that there was an easterly component in the headwind and the A/C had drifted nearly 3NM left of track by 0200z. Reference to the MET data published by BEA would also confirm an increasing east component in the wind closer to TASIL.

ATLANTICO requested ETA TASIL from AF447 following the by INTOL SELCAL check (01:35:43). There has been no evidence presented by BEA to suggest that ATLANTICO actually tried to SELCAL the aircraft when not receiving an answer to the requested time at TASIL.

The requested time for TASIL would suggest that ATLANTICO did not require reports at either SALPU or ORARO - probably due to no known conflicting traffic.

Other than ACARS messages that indicate the SATCOM ANT was still locked to the satellite at 0214z, and the rejected attempts by AF447 to log on to DAKAR ATC, the only other recorded contact with the A/C was the last squawk received at 0148z when approx 250NM from SBFN secondary radar.

0201z was the last rejected log on to DAKAR ATC, and it is reasonable to assume that FLT OPS were normal at that time, and there is no evidence to suggest that speed had drastically been reduced after INTOL.

mm43

Rob21

4th Jul 2009, 22:15

I understand Air France should be on "alert" or "high concern" mode after receiving all those ACARS (all Ambar and one RED?).

But Air France, along with French government and coordinated with Brazilian authorities, only launched the "a/c missing" alarm after AF 447 had no fuel to continue flying. I know this is SOP, but after all those ACARS, shouldn't AF have jumped on all the radios, SATCOMs, phones and tried to have any info about AF 447 with various ATCs? Maybe they did...

Maybe if Brazil, Senegal and Cabo Verde had received from AF info about those ACARS, the search effort maybe would have started earlier.

But the world only knew about those ACARS on the next day, when it leaked to the press.

I don't think it is fair to "imply" Brazil was "late" in launching the rescue efforts.

The search a/c were flying with 300 ft ceiling before sunrise, all ships in the area were alerted, to include fishing boats...

I believe that if Brazilian Air Force and Navy had known about those ACARS earlier, the search would have been directed to a more specific and smaller area.

I don't understand BEA's attitude towards Brazil, but in the FAB (Brazilian Air Force) web site it is very clear that all the procedures related to flight coordination with AF 447 were conducted as usual with all flights on that same route, day after day, week after week...

Someone can be so kind and tell me what am I missing here?

Thanks

Graybeard

4th Jul 2009, 22:16

Safetypee: IMHO your analytical logic fails with the assumption that the pitot systems would see different air masses on each side of the aircraft. From experience of tests and often due to the architecture of the pitot systems (cross balance pipes) this occurrence is most unlikely.

There are pitot-static systems, but I've never seen cross-connected pitot systems, or (cross balance pipes). If you remember from the prior diagrams, Pitot tubes 1 and 3 are on the left side of the lower nose, while #2 is on the right side. Each feeds only its own pneumatic to digital converter.

There is a cross-connected static port on each side of the fuselage that feeds each of the above converters.

Three pitot tubes; six static ports, unless I've lost count..

GB

threemiles

4th Jul 2009, 22:42

Is the flight number 0046 also masked; i.e., 0046 is not the actual flight number?

Correct, it is not a flight but an aircraft designator

From the little information available it is very likely it belongs to a LH 744

JD-EE

4th Jul 2009, 22:43

Surplus1 your comment below got uneducated little me thinking:
I would suggest that a ‘near vertical trajectory’ (descent) – in a level or flat attitude - is not possible unless both wings are fully stalled – the aircraft isn’t flying, it is falling and there is very little ‘forward motion’. I would postulate further that in such a prolonged “stall” condition a spin of some type, would almost certainly develop. If there was a “spin” there would also be rotation. If there was a conventional spin, the nose would be down – unless the ‘spin’ was a “flat spin” – in which the tail could be down and the nose up with reference to the horizon. The BEA made no mention of “rotation” on impact.

You also mentioned the T-tail shadowing. I know enough to be dangerous so I immediately flashed on T-tail shadowing when reading the above paragraph. In a nose high attitude with the wings stalled creating a lot of turbulence might that provide some degree of shadowing that would prevent the VS from doing its job and straightening the plane out?

I'm wondering more than thinking I've solved anything. It might explain why the VS stayed attached until contact with the water, as the BEA report suggests.

JD-EE

JuggleDan

4th Jul 2009, 22:43

Squawk_ident and others,

For some some reason, the transcription of the AF447-related radio communications was not included in the English translation of the BEA interim report (maybe another cause for misunderstanding).
For full access to these transcriptions (most are in English, a few are in Portuguese), please check annex 3 of the native version of the BEA interim report here (http://www.bea.aero/docspa/2009/f-cp090601e1/pdf/f-cp090601e1.pdf).

safetypee

4th Jul 2009, 22:46

Graybeard, (#3028), thanks for the reminder. I was probably being carried away by the ‘logic’ of the argument.
However, even if my thoughts on pitot systems are corrupted by my experience in developing another type (it most probably was a static error in a sideslip), the magnitude of the differing inputs required by the ‘digital’ comparators in the A330 might be more than is feasible in turbulence. Relatively a lot of dynamic pressure for the reduced static pressure at altitude?
Also, depending on the system architecture and input mechanism, and the way in which the ADC uses static pressure, the resultant airspeed should still be a function of the difference in total (pitot+static) and static pressures; thus there could be some ‘logic’ in this area.

JD-EE, if you consider a stalled situation or any other low speed scenario, then the aerodynamic forces on the fin would be quite low anyway, and thus it would not require any protection from the low-set horizontal tail.

Green-dot

4th Jul 2009, 23:15

Why all the violence? Surely there is enough in the turbulance to satisfy your worst nightmare? In a spin the bigger the airplane the less violently it behaves - to a point and, by the way, centrifugal force builds in a flat spin with both wingtips pulling towards the horizon, which is why it is a spin and not a continuing roll.

If you think about what you wrote there is little difference between what you say and what might be found in severe turbulance - I might submit that you could stall an airliner and enter a spin, in conditions of severe turbulance, without even noticing any change to your discomfort and the real point is that there is little, if anything, that will tell you something else has happened - except, perhaps, systems will start shutting down.... including engines, at the high angles of attack associated with the situation. So it is not impossible that some of this might be passed along via ACARS and much of it... not.

Referring to an accident report I have read, conditions of a large airplane in a flat spin can be violent. The following involves such an airplane roughly in the weight class of the A330 (but with a different planform).

In this accident one crew member of a crew of two survived because he was able to eject, the second crew member did not eject. The violence during the flat spin was the likely cause of the failure to eject.

Quoting the report:

"The airplane started to roll slightly, and when the pilot put in a little aileron to correct the roll. it yawed violently to the right. The pilot pulled the left throttles to idle, and was trying to advance the right-hand throttles to stop the yaw, but the airplane was out of control. The airplane rolled rapidly to the right and during the second rotation, the left wing separated at the manufacturing splice.

The pilot remembers:

"At some time during those violent maneuvers, I encapsulated, which was the first step in the bail out procedure, I expected the co-pilot would have done the same. The airplane settled into a flat spin and the forces became strong and almost constant, pushing us forward and to the side. I was having a hard time trying to keep my feet back against the heel kickers."

The pilot reported that he seemed for a period to be unable to move in the capsule due to loads throwing him forward and to the left. Finally he pulled the right handle of his escape capsule and encapsulated ballistically and was able to complete his ejection. In statement and testimony, the pilot indicates extreme forces were holding him forward and to the left during the period after loss of control of the airplane and until his own ejection was completed. The following three quotes from his statement indicate the severity of these forces:

"For the next few seconds I seemed unable to move in the capsule; the loads being somewhat oscillatory, throwing us forward and to the left. During this period of time I tried to talk, thinking that I had a hot mike; but I could only hear myself grunting under the excitement and extreme forces that seemed to be excerted on us and throwing us forward and to the left. Since it is mandatory for succesful completion of ballistic encapsulation and ejection from the airplane that the seat be moved to the full aft position, the gas pressure must overcome any forward forces. (Manual encapsulation under these conditions would be extremely difficult, if not impossible.)

Post crash capsule analysis (of the co-pilot) indicated that the relief diaphragm which releases the gas overpressure when the seat reaches a full aft position had been ruptured. This could have occurred as the result of gas pressure building to the limit when the system attempted to move the seat back against extreme forward forces. Had the latter occurred, no further opportunity for ballistic encapsulation would have existed. Even though moments of lowered force levels may have allowed successful ejection by one crew member, an unfortunate timing for actuation of the ballistic cycle during this forward force by the other may have resulted in the seat failing to retract precluding further possibility of escape.

It should be noted that the airplane remained in a flat spin, which would impose forward forces on the crew, from shortly after loss of control until ground impact. It is concluded that this was a likely cause for the co-pilot's failure to escape."

End of quote.

It took 76 seconds from the beginning of the event at 25,000 ft until the moment of impact on the ground. These 76 seconds included 16 seconds of level flight.

Because this was a test aircraft it carried an instrumentation package and its associated data recorders and telemetry equipment. Therefore, lots of data was available to the investigators.

http://www.pprune.org/5010930-post2070.html

JD-EE

4th Jul 2009, 23:17

mm43 noted:

Other than ACARS messages that indicate the SATCOM ANT was still locked to the satellite at 0214z, and the rejected attempts by AF447 to log on to DAKAR ATC, the only other recorded contact with the A/C was the last squawk received at 0148z when approx 250NM from SBFN secondary radar.

ACARS is a VERY low bandwidth operation. It does not need any appreciable power. Nor does it need an aimed antenna to transmit data to a satellite, even in a Clarke orbit. It needs a little more than the 5 watt hand held equipment used by some ham radio operators in coordinated demonstrations with ham radio operators on the ISS for voice communication demonstrations.

The distance is greater. That would require more power. The data bandwidth is much smaller than the FM voice. That would require less power. It's not quite a wash. An omnidirectional antenna is not necessarily needed. Several ACARS-like systems exist in the Maritime service that use virtually handheld sized equipment with omnidirectional antennas to talk to geosynchronous satellite with a data rate running below a couple hundred bits per second.

Therefore requiring the antenna to be "aimed at the satellite" is pushing my credibility limits. Even if there is only one satcom antenna I more than one or two people here know whether the ACARS transmissions use the SAME satellite. And if not it's as easy to shift a steered phased array antenna to omnidirectional to reach the ACARS bird as it is to try to aim at it.

This list is full of people asserting the SatCom antenna is fully aimed with a narrow beamwidth to reach the satellite for ACARS transmissions AND people who assert equally strongly that ACARS uses an omnidirectional antenna, which apparently must be part of the one antenna labeled SatCom aboard the aircraft.

So I simply contend that if thei aircraft entered an out of control spin we do not know when within at least 4 minutes since we do not know beyond a doubt whether the antenna is omnidirectional or not.

The one or two people here who DO know must be terribly frustrated with those asserting otherwise. Hopefully this clears up why some people are still asserting both positions as of the last time I presumed the antenna was directional after getting screamed at for presuming it was omnidirectional.

I do know, beyond any doubt, that I can communicate with a satellite with a device smaller than an iPod at a sufficiently low data rate. I designed the famn dool thing in 1978 for an unnamed agency through a cutout agency.

JD-EE (We all knew who. And it had a TLA in the US.)

tquehl

4th Jul 2009, 23:23

This thread has now digressed to T Tail deep stall concerns. I do have a few questions I feel are valid to be answered by those in the know ans Airbus drivers.

For the record, I am a Boeing/Douglas/Learjet/Embraer pilot and other assorted airframes with over 17K hours in jets worldwide.

My question involves control by the flight crew in the cockpit. I have had the privilege of the famous "Hoot" Gibson on my jumpseat and have discussed the departure from controlled flight over Lake Michigan, in the US, in the late 1970s. He alluded to the fact that that he lost over 20K feet in altitude, broke out of the bottom of the clouds, saw the Moon and pulled "hard". Hard being about 6 Gs. He told me they bottomed out at about 2700 feet. The airplane and passengers all survived, although well shaken up.

My question now to the Airbus gurus here is does the airplane allow you to exercise your piloting skills to maximimun advantage in an untrained and or unplanned situation? Remember, I am a Boeing/Douglas guy. Can you pull as hard as may be required? The difference between hitting the ground/ocean and recovery may well be pull hard on the horizion.

I will leave this open for discussion. Obviously the TWA aircraft under Capt. Gibson's command survived a 6 g recovery. The B-727 was never designed for this load factor, and the airframe in question was retired.

I do not want to hear BS about airframe certifiaction standards, comparrison in G loadings, etc. I will supply a link soon to the TWA incident, but I would hope that all professional aviators on this thread are aware.''

Over

DJ77

4th Jul 2009, 23:44

JD-EE about my crosstrack error calculation:

You quoted an unjustified level of precision there. However, even with that error band it was very slightly to the left of track when you'd expect any pilots even minimally weather aware to be somewhere else.

You are right, I should have given a range, about 2.6 to 3.2 nm, to my XTK result. The intention was to give those willing to check it what I found using all the available digits. Not a good idea, I admit.

My point is not to throw a judgment on the position relative to the weather. It is that the a/c was not riding on the airway centerline with the AP in NAV mode straight into the storm, as have been suggested earlier. The pilots almost certainly attempted deviations. I don't pretend this is a big piece of information either.

JuggleDan

4th Jul 2009, 23:50

I understand Air France should be on "alert" or "high concern" mode after receiving all those ACARS (all Ambar and one RED?).What we know yet is even more intriguing than that. From an article published in "Le Canard Enchainé" (French investigative newspaper) on June 24, it seems that when they received the ACARS messages, the AF maintenance center sent a maintenance team to wait for the plane. If I got it right, this was no emergency measure (at the time, they didn't know the plane was missing yet), but rather regular maintenance routine for loss-of-airspeed problems.

I don't understand BEA's attitude towards Brazil, but in the FAB (Brazilian Air Force) web site it is very clear that all the procedures related to flight coordination with AF 447 were conducted as usual with all flights on that same route, day after day, week after week...I can't speak for the BEA, but I tend to believe their attitude is due more to clumsiness and lack of diplomatic skills than to anything else. Be assured that a lot of people here in France are fully aware that Brazil did A LOT for the search and rescue operation, for the subsequent retrieval of bodies and debris, and for public information too.

There is one point, though where I strongly agree with the BEA: at some point, a plane with 228 souls aboard went missing, and because of a mix of various reasons (including the fact that ACARS messages are apparently not used for this purpose), nobody even noticed it :ugh:
I am not accusing anyone, as this is not and should not be the point: I just think that what happened should be examined from a standpoint of flight safety, so that one may try to fill up the d***ed Swiss cheese holes.

Will Fraser

5th Jul 2009, 00:07

JD-EE

Relative to 'rotation'. The BEA's conclusion that the VS was with the a/c until impact, and that it failed 'forward', with a 'left torsional component' implies a rotation of the airframe to the right before impact. As the a/c went in, its velocity in all vectors subsided, the abrupt halt to a rotation to the right would have provided the 'left torsion', IMO. I still believe the VS failed at altitude, but from the statements of BEA, there's your rotation. Obviously not in Pitch, though, sorry if you knew that.

Will

vovachan

5th Jul 2009, 00:27

It is mentioned in the BEA report that AF447 tried three times to log on to Dakar ATC using ADS-C messages. Does it necessarily require human intervention to send those msgs, or, like ACARS, this is something automatically generated?

I am wondering if the fact those msgs were sent really proves there was someone alive\conscious in the cockpit at the controls at that time, or it proves nothing at all? I am really struck by the absense of signs of life in the cockpit after 1:36

727gm

5th Jul 2009, 00:30

Another crash that began with a departure from controlled flight in IMC, a low-tailed, heavy jet, that never regained control, and crashed intact, was N827AX: DC-8 Mishap on 12 Dec 1996 N827AX -Stall Recovery in Mountainous Terrain (http://www.apstraining.com/article9_fci_training_aug03.htm) ASN Aircraft accident McDonnell Douglas DC-8-63F N827AX Narrows, VA (http://aviation-safety.net/database/record.php?id=19961222-0)

Will Fraser

5th Jul 2009, 00:39

Pictures of a/c freefalling in a flat aspect are intimidating, the XB-70 and the 707 over Fuji aren't what comes to mind when entertaining the concept. What is surprising is that the airframe reaches a relatively reasonable 'stability' though certainly not what the designers had in mind. I think given those pics (and others) it suggests that larger a/c have a more inherent integrity of flight envelope. In my experience, the larger the a/c, the more 'benign' the recovery from 'unusual' attitudes. I think given the short time since the accident, BEA had a lot more they could have written, but for many reasons, held off. One assumes they didn't have all the pertinent recovery and pathologies data as well.

Will

WhyIsThereAir

5th Jul 2009, 00:45

From the English version of the BEA report:

The first position message (AOC type message) was transmitted on 31 May at 22 h 39. On 1st June at 2 h 10 min 34, the last position received was latitude +2.98° (North) and longitude -030.59° (West). The position transmitted was the aircraft’s FM position which, in normal conditions, is close to the GPS position.

(Emphasis added)

Note here that the ACARS positions are presumably NOT gps positions. They are CLOSE TO gps positions.

What is "close"? Within an inch? Within 5 feet? Within a mile? Within 10 miles?

Unless that can be answered I'm not sure that the position being 2.71284635 miles to the left of the theoretical track means anything.

Graybeard

5th Jul 2009, 00:46

For JD-EE and others: look at Product Lines (http://www.rockwellcollins.com/ecat/at/xxProductList.html?smenu=3)

The CMU-900 and the IGA-2100B - SATCOM Intermediate Gain Antenna (http://www.rockwellcollins.com/ecat/at/IGA-2100B.html?smenu=101) would be the items of interest.

These may not be the units fitted to the AF fleet, but would be representative of the technology.

GB

Arnold E

5th Jul 2009, 00:55

Has there been any ifo published anywhere that indicates if there has been any positive results in the search for wreckage on the sea floor? I saw a report in the newspapers here in Oz on friday that the search for the pingers would only continue for another 11 days (now 9 days) Would the search for other wreckage continue? Without being able to examine a large amount of wreckage and preferably the FDR and CVR, then it would seem to me that we are not realy going to learn much from the loss of this aircraft.

tquehl

5th Jul 2009, 00:57

Within 30 meters, repeatable is " normal GPS" accuracy. This is not WAAS accuracy.

Will Fraser

5th Jul 2009, 01:03

vovachan

What seemed immediately incongruous to me about ACARS was that a/p tripped out (as it is programmed to do), because of exceeded limits reached by the a/c in auto flight. Nothing particularly dramatic about that, but even in turbulence, the a/p has generous +/- parameters, and it seems odd the pilot(s) would let the a/c get that rambunctious so as to require auto disconnect rather than manual disconnect sometime prior.

The a/c appears to have transited the wx when ACARS transmits a/p disc, A/THR drop, again why wait, if it appears inevitable hand flying will be necessary, being in turbulence, why hesitate?? One risks the instability of turbulence of course, but adjusting to minor out of trim state could be done earlier with a manual disconnect. Another question might be, is their record of aircrew briefings on the pitot unreliable a/s, and how often is it briefed especially prior to an ETOPS over water, night, wx impacted flight?

grizzled

5th Jul 2009, 01:47

The absence of communication from the flight deck, or any known attempt at communication, from 0136 onward does not necessarily correlate to there being “no problems”. IMO there is merit in the suggestion by some that given the known circumstances in this case, the lack of comms could in fact be an indicator of problems.

If anyone wishes to discuss / debate the above I'd be happy to do so on JB.

Grizz

TheShadow

5th Jul 2009, 01:57

I am really struck by the absence of signs of life in the cockpit after 1:36
Are we inferring a Helios 737 replay here? If the flight crew was insensible then it's likely that all on board were. If the aircraft then flew on into a CB, suffered an upset and nobody was conscious to manually intervene, it could be just a variation on that theme. Time of useful consciousness at a cabin of FL350 is a mere few seconds. However ACARS recorded no loss of pressurization, so what other form of subtle incapacitation is there, other than poison? Both crew fell asleep perhaps and woke with a start at autopilot disconnect - after entering a large cu-bubbly?
.
Not sure whether or not there's any other evidence to deny flightcrew disinvolvement as a theory (or for that matter, any viable scenario - short of an MS990 replay - in which it could play out). However it could also explain why no significant diversions around heavy weather along track were carried out.
.

Lightning6

5th Jul 2009, 02:01

The absence of communication from the flight deck, or any known attempt at communication, from 0136 onward does not necessarily correlate to there being “no problems”. IMO there is merit in the suggestion by some that given the known circumstances in this case, the lack of comms could in fact be an indicator of problems.

Whilst I agree with you to some extent, HF comms are notoriously inconsistent, especially in a storm situation (Possibly).

Will Fraser

5th Jul 2009, 02:06

Are there programmed alerts and mx transmissions that would in any way suggest that the crew was attempting 'recovery' eg overloading, rapid and multiple control limit excursions? Additional over limit/rate excursions beyond a/p limits? Anything? Or would all those be in the CVR/FDR?? I simply get the notion that for some time, the pilots were out of the loop in every way. I haven't seen this addressed, but with the last post of grizzled, It just seems things for four minutes just got worse and worse.

I've asked before, but can a 330 Captain characterize for us what the 'transition'/ reversion process a/p to pilot involves? Seems that so much confidence is placed in the a/c, the possibility of letting slip the in and out of transfer training may be a bit out of balance. Are there displays that cue the pilot 'what's left'? Not just 'what's gone'?

grizzled

5th Jul 2009, 02:12

Lightning6

5th Jul 2009, 02:29

Lightning6 -- Agreed. Your comments about HF are of course correct. Having said that there were other aircraft on the same assigned HF frequencies, some of which would likely have heard any attempts at HF contact by AF447. And some of those same aricraft were well within VHF range of AF447.

I take your point grizzled, the supposition that they had just had a selcal check previous to apparent loss of HF comms leads one to believe that HF comms was probably not a problem, even if they had gone onto standby, they would probobly have got the selcal, presuming the controller tried contacting them on selcal. Selcal being more unreliable as vocal HF transmissions.
I would imagine whatever was going on up there, comms would be the last thing they would have considered. No 1 consideration is to fly the a/c.

WhyIsThereAir

5th Jul 2009, 02:51

From the BEA report (and confirming what has been posted here before in many ACARS analyses):

F/CTL PRIM 1 FAULT (2 h 13)
Meaning: This message indicates that FCPC1 (PRIM 1) has stopped functioning.
This shutdown could be the result of a command or of a failure.

F/CTL SEC 1 FAULT (2 h 13)
Meaning: This message indicates that FCSC1 (SEC 1) has stopped functioning.
This shutdown could be the result of a command or of a failure.

So this is a possible indication of the crew alive and functioning as things go bad.

DCrefugee

5th Jul 2009, 03:09

When is anyone going to use the phrase "false sense of security" to help understand the lack of communication from AF447's cockpit after it flew beyond ATC radar range?

JD-EE

5th Jul 2009, 03:10

Graybeard - thank you, sir, for the pointer.

The antenna has greater than 6dBiC gain. So those who who declare steered and those who declare omnidirectional both have something on their side.

If I may riff on this a little, the dBiC specification basically refers to gain over a hypothetical purely isotropic circularly polarized antenna. Circular polarization avoids the Polaroid (tm) Sun glasses effect. Isotropic means the reference antenna pattern is a sphere. A pure hemisphere pattern would give exactly 3dBiC gain. So the antenna is somewhere betwen 60 degrees and 45 degrees beamwidth and aims itself roughly at the satellite. If they were using classical service they were sitting close to directly under the satellite per this link. Classic services coverage - Support - Inmarsat (http://www.inmarsat.com/Support/Coverage/Aero_classic.aspx?language=EN&textonly=False) If they were using SwiftBroadband service they were off at an angle of about 55 degrees from vertical relative to the satellite. SwiftBroadband Coverage - Support - Inmarsat (http://www.inmarsat.com/Support/Coverage/SwiftBroadband.aspx?language=EN&textonly=False)

So if they were using the classical Inmarsat modes they would not lose coverage in a flat spin until the equipment ceased to function. If they were on either the bird over Africa or the one South of Mexico then they'd have intermittent coverage that would depend on their spin rate.

Now can we determine which mode they used? If they support the Internet service I suspect it would be the SwiftBroadband service the antenna would be setup to support. Although being electronically steered it might be able to track the satellite adequately for communications through some pretty awesome gyrations if they were slow enough. If it was GPS aided tracking would be a slam dunk. If the integrated SatCom equipment that steers it is dumb enough then it'd lose track fairly easily with a high rate of spin.

I must admit that I was thinking "aimed" in terms of the antenna I was used to which had a much narrower beamwidth and tracked relatively reliably down to at least 7 degrees from the horizon. It used operator input for approximate position and aimed itself from there with a tracking algorithm that would uncomfortable once the gyros providing basic antenna stabilization became upset. But then, ships don't generally go into aircraft type spins. It was perfectly adequate for a ship in a pretty heavy storm.

If I had to put money on it I'd say that pretty close to 0214 and before 0215 the plane had met its fate.

Again, thanks for the pointer. It answered a lot of questions.

JD-EE

JD-EE

5th Jul 2009, 03:19

grizzled. in a single acro-breviation, 'SelCal'. Visit its page on Wakipoodle for a quick upgrade on the concept.

JD-EE

philipat

5th Jul 2009, 03:35

Why did the VS, as reported, appear to have broken away on impact from aft. Also other sections appear to have been ripped away from reverse forces. Is this consistent with the aircraft having been in a flat spin and, as chance would have it on the day, hitting the water tail first?

Just a question to the better informed.

WhyIsThereAir

5th Jul 2009, 04:15

I have reservations about a flat spin with no forward motion; but with the information publicly available it may be impossible to rule it out. Some mode where the plane spiraled in, nose up, seems a bit more consistent with what the BEA is really describing. At a rough guess (very rough, but the best possible with the public data) the plane probably needed about equal forward and vertical speed, say 100-150 MPH each way. And a small bit of leftward force at impact.

The BEA analysis of the tail separation and the "vertical acceration" they describe for the other damage seems to be at odds. The VS needs a strong force to the front of the hull, yet everything else is described as having a force downwards. But this might not be a contradiction if the plane came in at 45 degrees forward and down, and hit somewhat tail first. (Flight angle 45 degrees downward; pitch maybe 5-20 degrees nose up.)

Breaking the tailcone from HS impact with the water could pull loose the VS. This could also account for the damage to the bottom of the rudder. The remainder of the body slapping into the water and being arrested by the wings, combined with the forward motion, would provide the moment to pull loose the VS in a forward direction. Spiraling or turning moment to the right will throw the VS over the left side, as described. Slapping the body into the water will provide the "vertical acceleration" for the other damaged items, but there should also be evidence of some forward acceleration as the forward motion is arrested.

And possibly there is. If you carefully examine the picture of the galley tray rack, you will see that many of the right rails are bent down, but not the corresponding left rails. This implies that the trays were thrown to the right side and not straight down, or both rails would be damaged equally. (The bottom two rails are damaged on both sides, but that is understandable as things piled up.)

Question: where was this galley unit located? Is there any indication that the right of the tray rack would have been forward?