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AF 447 Thread No. 7

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AF 447 Thread No. 7

Old 28th Feb 2012, 00:00
  #761 (permalink)  
 
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@RR_NDB:

Unfortunately ADR 2 (RH PFD) is not recorded.

As mentioned in PAR 1.11.3 Interim report #3 the non-volatile memory in the salvaged computers
could give some more information.

From the FD engagement FDR traces and the information mentioned by HN39 (Page 44),
a little information about the status of ADR2 can be extracted.
(as far as I understand the sytems)

Before that one should know that a FMGEC needs at leats 2 valid ADR inputs to engage the FD.
-besides other AP/FD Common conditions -

Before @02:10:05 AP2 was engaged, this means (by engament logic)
FMGEC #2 was master, #1 was slave.
@02:10:05 AP drops off, Air speed of ADR 1 and ISIS(#3) are normal; FMGEC switchover is visible at the peak in FDR trace (FD2).
Suspect ADR 2 was the median speed at this time and lost (also due to other events at this time)
~02:10:10: Both FD (FMGEC) not available, also ADR#1 60Kts and ISIS(#3) 140Kts are to far apart.
~02:10:20: FD's available because ADR#1 and ISIS(#3) are nearly the same (but wrong) value 90Kts.
~02:10:25: FD's for a brief moment unavailable (although ADR#1 and ISIS(#3) are nearly equal (but wrong) at 110/100 Kts.
~02:10:30: FD's available, ADR#1 and ISIS(#3) in agreement (still wrong). Status ADR#2 (RH PFD unknown untill:
@02:10:40: There's a peak in both FD FDR traces, meaning they both switch over to
the other FMGEC, ADR#1 and ISIS(#3) are far apart, this means ADR(#2) must have been available again and its value in agreement with ADR(#1) = 215 Kts OR ISIS(#3) 120 Kts,
to become the 2 valid sources for FMGEC.
Unfortunally at that time they switch over to ADR#3 as faulty source for RH PFD!

From 02:10:47 untill 02:11:35 ADR#2 must have been available but not displayed on the RH PFD.

~02:11:45 the captain is entering the cockpit and would have seen 35 Kts on the LH PFD, 0 Kts on ISIS and SPEED FLAG on RH PFD.

After that all the speed indications where going up and down, FLAGS etc.
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Old 28th Feb 2012, 15:01
  #762 (permalink)  
 
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BEA testing software

@ChristiaanJ
I understand your argumentation, and I don't want to worry anybody. But today our forum wants to understand what was wrong in the AF447, and the Crew actions seem so crazy, that we must get sure that nothing wrong stays in the first levels inside of inside ... and that the BEA will be able to search the solution (if exists ) there too .

Originally Posted by ChristiaanJ
roulishollandais,

We seem to be on slightly different wavelengths.....

A CMM is aimed at the maintenance engineer who gets a supposedly faulty piece of equipment dumped on his bench, and has to find and fix the supposed fault, and then recertify the equipment as airworthy.

It is not aimed at either a pilot or (in the olden days) at a flight engineer, who don't necessarily have the specialist engineering background to 'decipher' electronic circuit diagrams or test specifications in a document like the CMM.
They refer to the functional documentation (aircraft flight manuals, etc.).
Originally Posted by RR_NDB
Is this a concern in order to understand reasons of PF persistent NU?

Mismatch between sides are recorded?

BEA published information mentioned this?

If existed a mismatch how we could learn what PF saw?

If this specific point was covered earlier, please inform the link, if possible

Last edited by roulishollandais; 28th Feb 2012 at 15:07. Reason: wrong attributed quote
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Old 28th Feb 2012, 16:30
  #763 (permalink)  
 
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Re: RHS not recorded

Is this a concern in order to understand reasons of PF persistent NU?
Yes, before switching to ADR3 the speed information displayed on the RH PFD will be 'unknown'. thereafter the information could be extracted from ISIS (share the same Pitot and static lines).
Was he following -wrong- FD orders, when this was available?

Mismatch between sides are recorded?
No, LH and (ISIS or Standby) are recorded.*

*Edit: BEA#3


Speed parameters

The calibrated airspeed recorded in the FDR is that displayed on the left-hand PFD, unless it is invalid
(if the speed is less than 30 kt, in which case the SPD flag replaces the speed
scale).
In this case, the airspeed recorded on the FDR is then that displayed on the righthand PFD.

BEA published information mentioned this?
Yes. PAR 4.3 of BEA Interim report #3

If existed a mismatch how we could learn what PF saw?
See previous post, I guess somebody can derive - possible FD orders-,
out of information from FDR traces.

If this specific point was covered earlier, please inform the link, if possible.
I don't know.

Last edited by A33Zab; 29th Feb 2012 at 09:30.
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Old 28th Feb 2012, 17:07
  #764 (permalink)  
 
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"Flying the FD" (FD commands are computed in exactly the same way as the AP commands) just after the AP has disconnected seems, to me, the height of folly.
I hope pilots are aware of that.... several posters here seem to not understand that.....
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Old 28th Feb 2012, 18:47
  #765 (permalink)  
 
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Actually the 'FD commands' immediately available after an A/P disconnect under normal circumstances are intended to be valid. That is how you would normally transition to hand flying the aircraft.

A/P disconnect was not the cause of any erroneous or misleading FD commands. When the A/P disconnects as a result of 2 or more ADR's going on the 'fritz', the FD's are automatically removed, but the buttons NOT automatically deselected (even the light in the button stays on).

It's the intermittent default FD commands that that 'pop up' in a UAS situation like this that are not to be blindly trusted. That is why, in the interest of avoiding this source of confusion, the FD's are to be deselected manually in an UAS situation.

There are other situations, e.g. PRM breakouts, where the FD's are deselected, because the existing or default vertical guidance may not be compatible with the PRM breakout procedural requirements. Has nothing to do with the A/P being disconnected. Has to do with being a pilot.

This is not your "grandfather's" FD-109.
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Old 28th Feb 2012, 19:12
  #766 (permalink)  
 
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Oke, howdy.

For the thick and the less than quick, like me, what do you have to describe as to the initial PF inputs post a/p? Bonin 'saw' (via BEA) ND and RR, to which he responded per report. PJ2 early on initiated a very important discussion that weeded out most here as to what the manual response should have been, eg, do nothing, maneuver, or deselect FD, and call the book. Arrest any poor trend? Attitude, Airspeed?? Pitch/Power?

I think, imo, Bonin did the right thing, which evolved, for reasons as yet undetermined, into a "climb" into the sea. There is a beginning to everything, where do you sense this point to be? For instance, the VS was "selected" by the a/c, at 5000fpm down. Since the a/c was rolling to the right, I assume the a/c was commanded so by the a/p, or the airmass was insinuating itself into the flight path. What gives?
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Old 28th Feb 2012, 19:19
  #767 (permalink)  
 
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Howdy Lyman,

I'm only speaking to the way the system works.

I have no idea what motivated the PF.

(The FMA is your friend. )
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Old 2nd Mar 2012, 13:02
  #768 (permalink)  
 
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Transient in Feedback Systems (I)

Hi,

Feedback loops are designed (and potentially capable) to improve a System.

For example, the AS probes in auto mode receives just the required electric power.

Feedback loops are designed with "time constants" and eventually with techniques like hysteresis. The engineering takes into account essential aspects like stability, etc.

I posted some comments assertively saying the AS probes the industry is still using, are "subheated".

I am based in several facts and i can discuss each one when necessary.

I have six questions to the Pilots (daily facing UAS threaths) and to the Technicians here:

1) Is the power being applied to the AS probes enough in order to their proper operation?
2) The delay between a sudden atmospheric temperature drop and the "reheating" of the probes could explain the "failures" leading to UAS?
3) The differences between US and FR probes may be explained by "different" time constants?
4) Is the max power sufficient to provide a safe operation in most environments?



5) Is there "recording capability" in current Systems in order to analyze the UAS incidents more precisely?

6) Could be better to enter WX using MAX instead of AUTO? (Operating "open loop")?



This content i posted first in another thread related to AF447.

Last edited by Jetdriver; 2nd Mar 2012 at 13:16.
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Old 2nd Mar 2012, 13:29
  #769 (permalink)  
 
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Subheated AS probes

Hi,

One may ask:

What is the importance of this issue?

AS data affects the Stability of the System.


The importance is clearly recognized by the Designers in applying triple redundancy.

IMHO is unacceptable the FACT they are "failing" almost SIMUTANEOUSLY.

Redundancy is not the solution to elements that "fail together"

IMO this configures a SERIOUS and PERSISTENT "DESIGN FLAW" or even, ERROR

AND VERY PROBABLY WILL BE CONSIDERED THE TRIGGER OF AF447 CASE.

The industry was receiving persistent warnings on this and the crew of the previous incidents were capable to deal with and landed.

Murphy Law in this case used the "industry failure" and put other slices of the cheese in the "proper alignement"
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Old 2nd Mar 2012, 14:28
  #770 (permalink)  
 
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The importance is clearly recognized by the Designers in applying triple redundancy.

IMHO is unacceptable the FACT they are "failing" almost SIMUTANEOUSLY.

Redundancy is not the solution to elements that "fail together"



IMO this configures a SERIOUS and PERSISTENT "DESIGN FLAW" or even, ERROR
I do not agree

Redundancy is more than duplicating a single system (even though there are multiple similar components). It also considers multiple systems which can take over and mitigate the failure condition and still provide safe flight and landing.
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Old 2nd Mar 2012, 14:50
  #771 (permalink)  
 
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Redundancy

Hi,

Redundancy is more than duplicating a single system (even though there are multiple similar components). It also considers multiple systems which can take over and mitigate the failure condition and still provide safe flight and landing.

I fully agree with your comment above!

I do not agree
Please, clarify where is the discordance. Component level redundancy? Module level? System level?
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Old 2nd Mar 2012, 14:58
  #772 (permalink)  
 
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F-GZCP last flight

Hi,

Redundancy is more than duplicating a single system (even though there are multiple similar components). It also considers multiple systems which can take over and mitigate the failure condition and still provide safe flight and landing.
Did F-GZCP provide the resources to?
.
.

Did the man-machine interface provide the tools to allow the crew to even understand TIMELY the first priorities?

Last edited by RR_NDB; 2nd Mar 2012 at 17:03. Reason: add ?
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Old 2nd Mar 2012, 17:37
  #773 (permalink)  
 
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RR NDB

Please, clarify where is the discordance. Component level redundancy? Module level? System level? Please, clarify where is the discordance. Component level redundancy? Module level? System level?
ans. System level

Did the man-machine interface provide the tools to allow the crew to even understand TIMELY the first priorities?
That is the most important part of the investigation's report to provide comparitive prevention strategies (in any aircraft) via system design and/or training against a repeat accident where airpseed is temporarily lost for any reason.
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Old 2nd Mar 2012, 17:48
  #774 (permalink)  
 
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If the redundance is at system level, and the three sensors are identical, redundancy is absent.

Thales had corrosion problems at the drain, I do not recall if they rose to the level of AD. Regardless, the probes performed sufficient to satisfy the certifications protocol, and that is acceptable. After the fact does not obtain to this crash.

Redundancy had thorough airing in BA038, where BOTH engines failed, within seconds of eachother. The Heat exchangers were found to be of insufficient design. Instead of changing engine manufacturers, the Heat Exchangers were modded. An AirSpeed sensing SYSTEM that relies on three identical probes is a single system. IF there are mitigating procedures that can provide AS in a transient system failure, well and good. However, focussing on the probes only is missing the point at large, eg: system FAIL.
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Old 2nd Mar 2012, 18:00
  #775 (permalink)  
 
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Probes as the trigger factor

Hi,

However, focussing on the probes only is missing the point at large, eg: system FAIL.

Your comment and the one from lomapaseo motivates me to say:

A probe "failure" exposed a much more serious issue at System level.

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Old 2nd Mar 2012, 18:16
  #776 (permalink)  
 
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HHi RR NDB.

I would suggest further, that in this particular case, had only ONE Pitot tube been installed, the outcome may have been different.

One only need review the computers trail, the Pilots' confusion, and the lack of a co-ordinated plan to conclude that in this case, had the system failed completely, directly, (and REJECTED, with prejudice) in transient fashion, a single probe would have come back alive and been correct, no "voting", no indecision?

The AS system here seems over-reliant on decision making made at the electronic level, excluding the handling pilots, and causing delay.

At the least, had a separate "system" been installed, one that had a shrouded probe that came alive when the first failed, a new and reliable sense of AS would be available.

The focus on redundancy is a fool's errand, when a "sequential system(s)" is a separate and independent source. Even BUSS fills this need, a separate system, one that can replace indefinitely a system that causes problems whilst one waits for it to become reliable.

The longer these UAS events pertain, the more foolish the authority appears.
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Old 2nd Mar 2012, 18:28
  #777 (permalink)  
 
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Lyman sayeth:
The focus on redundancy is a fool's errand...
All I have to say is that it's a damned good thing there are two wings!
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Old 2nd Mar 2012, 19:10
  #778 (permalink)  
 
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Bureaucracy

Hi,

The longer these UAS events pertain, the more foolish the authority appears.


Bureaucrats are prone to be lazy. Their "time constant" are much bigger than the good Technicians SELF MOTIVATED.

PS

Kelly Johnson put an angel to fly in 60 days. Yet taxiing:

The sailplane-like wings were so efficient that the aircraft jumped into the air at 70 knots (81 mph)
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Old 2nd Mar 2012, 21:14
  #779 (permalink)  
 
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Hi Organfreak

At some point, system utilization must merge, or we end up with something, you know, Rutanesque.

Some would have said (and still say) "Thank GOD for two TRENT700s. (BEA038)." Where the neck narrows, there is the executioner's blade.

RR NDB. (re Kelly Johnson). Where are these giants today? Gone. What we have left are committees, ffs. risk/benefit. Over-reliance on the ability to disappear and blame others. COMMAND? gone.

Captain Hank, on his Stratocruiser, "This is not a god damn Democracy!"
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Old 2nd Mar 2012, 21:16
  #780 (permalink)  
 
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Shrouded probe

Hi,

At the least, had a separate "system" been installed, one that had a shrouded probe that came alive when the first failed,...
LOL,

I am sure the issue can be fixed without this...,

LOL

Anyway i maintain what i did write earlier:The design (in respect to AS) seems ridiculous

And maintaining this during many years was the trigger for System stability issues at that night *

(*)

K.I.C.S. Keep It Complex Stupid

M.I.C.S. Maintain It Complex Stupid
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