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-   -   AF 447 Search to resume (part2) (https://www.pprune.org/tech-log/449639-af-447-search-resume-part2.html)

gums 23rd Apr 2011 20:05

AF 447 Search to resume (part2)
 
Part 1 of this thread can be found Here


Need some of you "bus" drivers to clue me in re: autopilot authority and inputs.

If the pitot-static inputs go tits up, what happens? The B-2 crash was a result of several sensors being filled with water and the jet tried to climb like hell just after WOW. Seems like an "attitude" control law would have helped those two guys.

So my theory all along is the pitot-static system went south and the crew didn't react properly and/or the autopilot didn't revert to an "attitude" mode. Sheesh. All of us that have flown into CB's or had a pitot-static ice problem and simply held attitude and didn't chase speed or altitude until we figured out our problem. Keep wings level and a semblance of level attitude.

In several instances I was glad that the Viper control laws were gee- command and roll rate. Let go of the stick and the jet would try to keep trim gee and zero roll rate. I have a hard time with all the "control laws" for the "bus". Glad I am not/ was not a pilot of the beast.

HazelNuts39 23rd Apr 2011 20:19


Did all Tx (ACARS) arrivee via FIN??
The BEA report #1, 1.16.2.4 states that after 2:10 all ACARS messages passed through the same satellite:

The messages received on 1st June after 2 h 10 all transited via the same satellite (Atlantic Ocean West, operated by the Inmarsat Company) and SITA’s ACARS network.

bearfoil 23rd Apr 2011 20:42

Hazelnuts39

Yes, of course, the ACARS that were released to the public. That is not demonstrably untrue, it merely would mean that the repeated ACARS stream broadcast after the antenna interruption by the SATCOM antenna/System had restarted with the first of the ACARS stream we have. (The "Overlap").

I have wondered why we see no activity of ACARS prior to those we have in the public domain. Weren't these released by a whistleblower, and if AF had those streamed by the Fin (VHF) that weren't released, why would they release those? I was given to undertsand that ACARs tx of preference is VHF (cost??). Golly, that is complicated, though, surely if they existed, BEA would release all the ACARS from this flight?

This of course means that 447 was airborne and Txable SATCOM if there was a repeat Tx by the flight. It would certainly allow that the pilots may have taken a breath prior to re-engaging the A/P?? Well, I am certainly beyond my expertise here.

JD-EE 23rd Apr 2011 20:59

HN39, just a short note, when I was developing some software for Inmarsat-M SatCom terminals I communicated regularly with AOW from Torrance through the ground station in Goonhilly. That gives you some notion of the theoretical coverage range. (My antenna was aimed below the horizon for the typical ACARS antenna though.)

bearfoil 23rd Apr 2011 21:00

I have wondered since the outset why there are no ACARS alerts via Satellite between the last two on the ramp at RIO, and the ones beginning at 0210.

Wouldn't there be at least a few? 447 was no virgin, and she must have had reportable defects prior to "The Sky is falling" at 0210. Or is radio abandoned at the intervals I would question?? Irrespective of antenna issues, what explains the dearth of ACARS coms??

JD-EE 23rd Apr 2011 21:05

Bearfoil, you are reaching way too far. You are presuming the airline is so cheap they'd send messages via HF rather than SatCom when the plane is SatCom equipped. And I am not at all sure HF would be even pennies a message cheaper. It would certainly be less reliable without some serious Automatic Link Establishment sort of technology. HF propagation is not necessarily a hands off operation without such technology.

You have a habit if making unsupported and too often unsupportable assertions. And you are back to your mantra that you said you never discuss, "the VS er Fin came off the plane and caused the accident." This gets REALLY tiresome, sir.

I'd also like to note that there was a previous trouble message included in the logs - one of the potties had a problem.

HazelNuts39 23rd Apr 2011 21:05


Originally Posted by bearfoil
if AF had those streamed by the Fin (VHF)

The fin has HF1/2, whereas VHF1/2/3 are on the fuselage.

mm43 23rd Apr 2011 21:08


Originally posted by bearfoil ..

I have wondered since the outset why there are no ACARS alerts via Satellite between the last two on the ramp at RIO, and the ones beginning at 0210.
There was a LAV fault reported, and don't forget the AOC position reports were every 10 minutes via ACARS.

JD-EE 23rd Apr 2011 21:08

HN39, I'd also note that you ain't gonna stream via VHF out where the plane was no matter WHERE its antenna is. 100nm is about it for VHF give or take a factor of two. (I'm not going to bother to go look it up on the nomographs I have.)

bearfoil 23rd Apr 2011 21:25

For goodness sake. This thread is 100 percent conjecture and partial repetition of BEA regurgitatae...... The Potty pressure valve bollux and the Audio panel glitch were rampside, if I'm not mistaken, and frankly what is tiresome are people who eat mush blindfolded, without palpating it at least.

The audio panel was mel, I don't think the lav was important enough to make the list. The radio selects were of no small concern.

This entire exercise is nothing more than an intriguing diversion. To think any real results are to be found here is absurd. The reality of the exercise is what is elusive. The pilots knew. They knew. The a/c and ground support failed them, and by extension, all those in their loving and skilled care.

What is beyond tiresome is most here taking themselves far too seriously.

There are a few here for whom I have utmost respect, and frankly more for their grace than their respective expertise, inspiring though that be.

If anyone here thinks I am serious beyond an informed speculation and earnest question or two, please read me with tongue in cheek, as intended.

Christ on a freaking crutch.

ACLS65 23rd Apr 2011 21:35

JD-EE

"HN39, I'd also note that you ain't gonna stream via VHF out where the plane was no matter WHERE its antenna is. 100nm is about it for VHF give or take a factor of two. (I'm not going to bother to go look it up on the nomographs I have.)"

Where AF447 was it was out of range of VHF and ADS-B, and didn't have HF ACARS. It doesn't look like their is much amateur monitoring of ADS-B in that area.

In terms of previous ACARS messages I suspect there would have been VACARS transmitted via VHF3 prior to SATCOM.

The A330 Comm manual says that "ACARS normally transmits via VHF3. It automatically switches to SATCOM when VHF3 is not available."

Not quite sure if that means ACARS switches automatically when it is no longer receiving ACARS msgs via VHF3, or if by unavailable they mean something else.

mm43 23rd Apr 2011 22:25

Mr Optimistic posted a message at #9 in this thread, but has subsequently withdrawn it. The question posed was, "Is Svarin's analysis of the ACARS messages accepted?"

With the thread otherwise engaged, potty/lav included, I think the substance of what Svarin had to say in post #3858 and post #3863 in Part 1 of this thread has been overlooked.

In essence, the A/P and A/THR disconnected due to UAS. Cockpit activity is evidenced by -

2:12:10 WRN/WN0906010211 341200106FLAG ON CAPT PFD FPV
2:12:16 WRN/WN0906010211 341201106FLAG ON F/O PFD FPV

Two pages not normally selected in the cruise.

Secondly, the A/P was reconnected 3 minutes after the UAS in what was apparently an unstable situation -

2:14:20 FLR/FR0906010213 22833406AFS 1,,,,,,,FMGEC1(1CA1),INTERMITTENT

possibly causing a pitch up command, a situation around which an Airworthiness Directive was issued this (northern) winter regarding A/P reengagement after an UAS condition.

I think that Svarin is probably correct, and I know that he has meticulously examined each of the ACARS messages and sought rational explanations for all. The answer was found in the "detail".

The CVR will be necessary to confirm what was going on prior to 0210.

Machaca 23rd Apr 2011 22:49

From EASA AD No.: 2010-0271 (22 December 2010):

REASON
http://i337.photobucket.com/albums/n...271_Reason.jpg

http://i337.photobucket.com/albums/n..._Prodedure.jpg

Khashoggi 23rd Apr 2011 23:02

Assuming AF447 was intact on hitting the Ocean surface, could you explain the disparate condition of the floating wreckage by considering that the Ocean surface was not flat but instead had large wave action?

The BEA thinks there was low forward velocity, but a fuselage hitting a line of waves could cause multiple impacts, and various breaks and ejection of components under varying impact loads.

There was wx in the area, so presumably the Ocean wasn't smooth as silk that night??

Mr Optimistic 23rd Apr 2011 23:05

mm43
 
Sorry, thought my post was contentious (not a pilot so cautious). Svarin's post seemed informative but don't understand why after nearly 2 years anything new is coming from the ACRAS messages and if it is new why so little attention is given to it.

HazelNuts39 23rd Apr 2011 23:21

Maybe there is a difference between AP disengaged, AP lost, and AP off?

broadreach 23rd Apr 2011 23:30

Machaca,

Note the date of that!

EASA AD No.: 2010-0271 (22 December 2010)

Would there have been an AD along similar lines available prior to the accident?

Machaca 23rd Apr 2011 23:33

khashoggi - A very good point and quite correct. Yes, the irregular surface of the ocean did indeed play a large part in how the airframe and its contents were damaged and to what level.

It was discussed many moons ago in an earlier thread. Sadly, many have forgotten or disregarded much of the valuable and substantiated input that has been provided over the last 22+ months. Yet some proffer curious scenarios as if they were never contemplated beforehand. :ugh:

I don't know why it is so difficult for some to envision how a galley can be ejected relatively undamaged in such an impact with the sea.

Machaca 23rd Apr 2011 23:45

broadreach - AD 2010-0271 does not supersede any previous AD's.

jcjeant 23rd Apr 2011 23:55

Hi,


It has been identified that after such an event,if two airspeed sourcesbecome similar while still erroneous,the flight guidance computer will:
Do any one know the date and what event ... when this was identified ?

Turbine D 23rd Apr 2011 23:58

Bear

Contained within the OnPoint Program is the real time diagnostic program. There are two levels, Standard or Comprehensive, the Comprehensive can be custom designed to whatever the aircarrier would like. For what we would be interested in, the Standard program will show fault alerts, exceedance alerts and would notify the aircarrier of "critical" detected anomalies. The Comprehensive program would do the same as the Standard program but also would diagnose (diagnosis done by GE) the fault alerts and would detect all anomalies. So the data transmitted by each engine to GE & AF would depend on which program AF selected.

The data sent in either case would show all the key engine operating data, N1 and N2 speeds, oil quantity & temperatures, EGT readings, fuel consumption, air pressure entering the combustor, high vibrations, etc. The detected critical anomalies would include high EGT, flame out/compressor stall conditions, fire, commanded engine thrust levels outside normal operational conditions, etc.

I don't know what AF signed up for, but the data is very comprehensive and dates to the very first flight of the engine sending the data.

Sorry for the delay, but we have had bad weather here today...

jcjeant 24th Apr 2011 00:03

Hi,


Assuming AF447 was intact on hitting the Ocean surface, could you explain the disparate condition of the floating wreckage by considering that the Ocean surface was not flat but instead had large wave action?

The BEA thinks there was low forward velocity, but a fuselage hitting a line of waves could cause multiple impacts, and various breaks and ejection of components under varying impact loads.

There was wx in the area, so presumably the Ocean wasn't smooth as silk that night??
I think it was already posted :)

3.32


Smilin_Ed 24th Apr 2011 00:04

Qantas Upset
 

Do any one know the date and what event ... when this was identified ?
Wasn't that after the Qantas upset?

mm43 24th Apr 2011 00:22

HN39;

Maybe there is a difference between AP disengaged, AP lost, and AP off?
What point are you trying to make? I assume it is in relation to the AFS part of the message.

In the ACARS list there is mention of a "possible loss of signal" with the satellite. The actual fault received at 2:14:20 was probably initiated in that 2:13:16 ~ 2:13:41 time slot.

Turbine D 24th Apr 2011 00:31

gums

Here is what can happen when the pitot tubes start to ice over and the pilots respond to the false (higher) speed/climb rate readings by throttling back. In this case it is pre-computer age.

http://www.airdisaster.com/reports/ntsb/AAR75-13.pdf

However,


All of us that have flown into CB's or had a pitot-static ice problem and simply held attitude and didn't chase speed or altitude until we figured out our problem. Keep wings level and a semblance of level attitude.
seems so right, if one recognizes the situation.

CONF iture 24th Apr 2011 03:13


Originally Posted by Smilin_Ed
Wasn't that after the Qantas upset?

No, QF72 upset was not related to Unreliable Airspeed Indication.

jcjeant has a very valid question :
Which event was identified to justify the publication of the AD 2010-0271 and the related red OEB called Loss of AP and A/THR associated with alternate law reversion ... ?

HazelNuts39 24th Apr 2011 03:22

mm43;

I was wondering whether an AP that had disengaged automatically, but had not been selected OFF, could still be the identifier in the FLR message (without having been re-engaged).

gums 24th Apr 2011 04:00

Salute!

Thanks, Turbine.

The procedure outlined in machaca's post seems very reasonable. And I doubt that the AF crew re-engaged the autopilot if it had kicked off for whatever reason, especially in turbulence.

Many of us on this forum have experienced turbulence beyond the definition "moderate", heh heh. Last thing we did was have "otto" try to "help". I tend to go with the FBW systems, as they seem to avoid huge control surface movements, but apply the commands much quicker than we humans. The Viper felt about like a F-111 down low on a bumpy day. Nice soft ride for a "light" jet.

Waiting for the recorders' story.

slats11 24th Apr 2011 04:09

Svarin

Gentlemen,

it is obviously difficult for most internet-age people to read beyond a few lines of text with any effectiveness
With all due respect, I don't think this is really fair. All of us have been generous with our time and contributed what expertise we have in order that we may collectively understand what happened here.

Naturally, we will all tend to focus on different aspects and different phases of this disaster - depending on our area of special interest or expertise. When all you have is a hammer......

Clearly you have detailed understanding of the flight control systems and the ACARS stuff - areas that are pretty much meaningless to me. Others have displayed very detailed understanding of radio capabilities and satellites. It is not that I am disagreeing with any of these people, or not bothering to read their posts (interesting even if beyond my understanding). I am simply talking about something different.

So I am not disputing your proposed explanation - I can't. Rather, I am proposing that there are likely to have been additional significant human nature issues prior to the upset, and that these may have played a contributory role.

The fact that this scenario has never happened previously despite many hundreds of thousands of operation of this model aircraft, and the fact that we still don't really know what has happened despite thousands of posts and countless thousands of hours of speculation means that the exact sequence of events is likely to be complex and non-intuitive. There is likely to be a complex interplay of factors (aircraft and personnel) that combined on this particular occasion to produce a unique outcome.

Please, this is not a pissing contest. Nor should it be seen as an opportunity to denigrate others. Surely that is disrespectful to those that lost their lives, as well as to those here seeking to advance our collective knowledge. When (if) we know all, then it may appear to have been somewhat arrogant or naive to believe that there was one single factor (to the exclusion of everything else) responsible here.

HazelNuts39 24th Apr 2011 04:13

CONF iture;

RE jcjeant's question;

BEA report no.2, after analysis of thirteen events of losses of or temporary anomalies in indicated speeds, states:

In seven cases, the autopilot was reconnected during the event. In two of them, the re-connection occurred when the two speeds were consistent with each other but were erroneous;
and:

The reappearance of the flight directors on the PFD when two air speeds will be calculated that can lead the crew to rapidly engage the autopilot. However, these speeds, though of the same order, can be erroneous and weak and thus lead the autopilot to command movements of the flight control surfaces that are inappropriate for the real speed of the airplane.

Machinbird 24th Apr 2011 05:43


...can be erroneous and weak and thus lead the autopilot to command movements of the flight control surfaces that are inappropriate for the real speed of the airplane.
For those that remember the X-31 accident previously provided as a reference, does this sound familiar?

Khashoggi 24th Apr 2011 06:55

Machinbird, thanks for the reference...

X-31 airdata icing fubars the flight computer.
X-31 Crash

Looks like a pancake (~low[non-existant] horizontal component, large vertical, minor yaw from FL200 to Edwards) to me:

http://www.check-six.com/images/Cras...1-95Aerial.jpg

grizzled 24th Apr 2011 07:16

slats11...

Well said.

Svarin 24th Apr 2011 10:29

slats11
 
I said :


it is obviously difficult for most internet-age people to read beyond a few lines of text with any effectiveness
slats11 said :


With all due respect, I don't think this is really fair.
You are right. It was not. I regret it came across as a personal slight. Please accept my apologies.

I read your post in full by the way :O

henra 24th Apr 2011 10:43

svarin:

02:14:20 - .1/FLR/FR0906010213 22833406AFS 1,,,,,,,FMGEC1(1CA1),INTERMITTENT

The failure has AFS (Auto Flight System) as its identifiers. AFS is Airbusese for Autopilot. But wasn't that A/P OFF at the beginning of the sequence ? And it was turned OFF by the aircraft itself, following Pitot probes failure. And now we find it as the identifier in an FMGEC fault, which means AFS detected a fault in FMGEC1. Who turned the A/P back ON and reactivated it ?
Good catch !!

Obviously this message never received the attention it maybe warranted..

Even looking at BEA's comment on this item reading a bit between the lines it becomes clear there might be something to it:

From BEA's second interim Report:

FMGEC1 (1CA1) (2 h 13)
ATA: 228334
Source: AFS
Identifiers: -
Class 1, INTERMITTENT
This message cannot be the trace of a reset which, in particular, excludes the
possibility of a manual shutdown. This message could be the consequence of
inconsistency between the two channels in the FMGEC (COM and MON). Such
an inconsistency could be the consequence of erratic input parameter values.
In any event, the effects of such a message could only be the disengagement
of automatic systems, whose associated
cockpit effect messages had already
been transmitted at 2 h 10.
The “INTERMITTENT” nature of the message means that the problem lasted for

less than 2.5 seconds.

Between the lines I read that this indeed seems to indicate that automatic systems have been disengaged. Which in turn could imply they had been re-engaged before after the first disengagement which triggered the 210 ECAM's.
The AD might indeed closely be related to this accident.

The ACARS message regarding Cabin Vertical speed is dated 1 min later than this. Which would mean that they were most likely not at CRZ altitude when the AFS was potentially re-engaged.
This would point indeed to two upsets:
Initial upset caused by UAS, recovered at an intermediate altitude (soemwhere between 10000 and 20000ft) which matches previous UAS incidents quite well btw.
A subsequent upset caused by the AFS mislead by the still unreliable but now consistent speed.
Question arising from this scenario: Down to which altitude could pitot icing be expected?
Anyway, this scenario could explain the tragic difference to the previous incidents.

Svarin 24th Apr 2011 10:58

A/P ON at 0213
 
Regarding this message :

2:14:20 FLR/FR0906010213 22833406AFS 1,,,,,,,FMGEC1(1CA1),INTERMITTENT

BEA reported :


In any event, the effects of such a message could only be the disengagement of automatic systems, whose associated cockpit effect messages had already been transmitted at 2 h 10
To this should be added, from the same report, that a cockpit effect will only appear once in a given CFR/PFR. What we deal with is a CFR (Current Flight Report). I take it then that a A/P OFF message will not be repeated, since it was sent around 0210.

It is unfortunate that BEA would only give this item of information in that particular, obscure way. They essentially repeat themselves. However, reading between their lines would mean that A/P went OFF again without an ACARS message being transmitted (already done). So A/P had to be turned ON after 0210.

Another information hidden in this sentence from the report is that the list of cockpit effects produced by this failure is included in (but not necessarily identical to) all cockpit effects already sent from 0210.

In addition, would AFS catch a fault in FMGEC if it was still OFF (kicked off by the system itself). In other words, does the AFS as identifier positively ascertain that A/P was ON at the time the message was concatenated ?

My answer is yes, through all accumulated knowledge, but I do not have a positive answer, officially written in a book. I believe yes, it fits with all the rest (and I mean all the rest), but then... I am not defending that case in a court of Law, lucky me.

I would have expected BEA to answer that particular question, one way or the other. I guess they will do it now, and prove me wrong...

(Simultaneous with henra)

Chris Scott 24th Apr 2011 12:45

Cabin Crew
 
slats11 & Mr Optimistic,

Been de-camping for last 48hrs, so now trying to catch up with this freight-train again... You've been discussing cabin crew activity/position.

Of course they MIGHT have been recently dealing with pax dinner. 0200z is 2200L at Rio. They were 3hrs30 into the flight, but it was a big load. If pax finished, crew dinner (cabin and/or flight-crew) might have been still under way.

[Just as an aside, I was once served dinner on an A320 and, as the steward lost his balance, the meal tray collided gently with the throttles. No harm done until he panicked and whipped the tray backwards, depositing its contents (including curry & rice) all over the centre pedestal!]

It can take the CC a long time, from the receipt of a command to secure the cabin, to complete the task. The most compelling evidence I've seen that they had not completed that task was the excellent picture posted by Shadoko, here, of one of the galley catering-cannister stowage units. The latches that must be closed to secure the cannisters are plainly open. Any proximate cabin crew member worth his/her salt would have secured them before sitting down, if severe turbulence was expected.

Mr Optimistic 24th Apr 2011 13:41

CS: OK, thanks. Seems clear on that point at least!

Edit: Though I wonder if that is consistent with the early best-fit scenarios with the weather, ie that the a/c was at the far end/about to exit a Cb. Suspect that can't be right as there would have been warning before the 'event'.

CONF iture 24th Apr 2011 14:03

HazelNuts39,

Thanks for the references from the BEA report, I didn't remember them.
Still, I think the AD is more specific :

However, in some cases, the AP orders may be inappropriate, such as possible abrupt pitch command.
Are you aware of such specific concern among the 13 events ?
Why that AD so late (DEC 2010) when the 13 events were already known for a while ?
Any possibility for another ... event to justify the making of such AD ?


Originally Posted by 'PJ2"
I'm not sure what to make of "c", (in the sense that I would have expected not a pitch angle protection active, but an AoA protection active input.

I don't have an answer to that question, but that reminds me the 'Anti pitch-up compensation' which was partially responsible of the QF72 upset.
Who was aware of that 'compensation' ... before it was mentionned in the ATSB report ?
I had personaly never seen anything on it in any FCOM or other VACBI.

Just to say that there is so much unknown or/and untold on those airplanes ...

Pugachev Cobra 24th Apr 2011 14:54

X-31 Crash Video
 
UAS due to icing in the Kiel probe causes X-31 flight computer anomaly.


In case someone haven't seen it yet.


The 43-minute mission was nearing its conclusion when ice began forming on the X-31's pitot tube. The ice caused incorrect airspeed information to be sent to the craft's flight control computers, which were responsible for reconfiguring the aircraft for lower speeds. The result was a series of sudden, uncontrollable oscillations in all axes. The aircraft then pitched to 90 degrees angle of attack, and Lang was forced to eject as the X-31 crashed near the northern boundary of Edwards Air Force Base.
From: NASA - Dryden Flight Research Center - X-Press: January 2004


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