AF447

[Flintstone]

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]

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]

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]

A other analyse ..

Hi,

Eurocockpit - Archives

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]

In this post http://www.pprune.org/rumours-news/3...ml#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]

Originally Posted by Dinger

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]

ACARS Position Reporting

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]

scouselander

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]

BOAC

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]

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]

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]

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]

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]

now retired PJ2

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]

Why ?

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]

[quote=Icarus]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.

Do you know the flight path "the aircraft followed" for a fact?

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 ?

Do you know he was?

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

Do you know they did 'miss' it?[/quote]

I have no issue with the rest of your post.

[u674087]

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]

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]

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]

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


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.