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AF447 Thread No. 3

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AF447 Thread No. 3

Old 13th Jun 2011, 14:24
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Regarding pitot freeze modes:

Syseng68k

Totally concur.

After looking at the design and mechanics of current pitot designs, I would be very surprised if the drain hole had actually blocked, since the hole itself is in the main body of the probe and likely to be well heated. The probe tip is obviously the most 'cooled' part of the assembly and therefore the most susceptible to icing.
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Old 13th Jun 2011, 14:27
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safetypee, I do agree, that's why I am asking again and again : Why don't we have access to those data ?
They are only data, why are they so secretive and so partially presented and so, in such a confused manner ?

3D animation is available too ...
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Old 13th Jun 2011, 14:36
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"Finally, there has been some speculation that the pitot issue bay have been drain blockage leading to an increase in airspeed indication... where is this imaginary event coming from? Does anyone here rationally think that the BEA would not mention this? "

BEA left out a great deal, though including some milestones in their report. I am unwinding the flight from THS NU 3 degrees, backwards, and find that a possibility exists for unreliably high ias. With aft fuel for trim, wouldn't the HS be expected to provide less NU force for a given cruise velocity? So I am merely pondering the existence of a need for augmented NU from HS. If ice crystal blockage, I am thinking the Drain would pack first, increasing Pressure in the Tube, which the AD would read as increased a/s? The events that are most important may appear to be sequenced in the BEA note, but they are loosely organized v/v Time points (From 2:10:05). So 275knots may have been the "start" of uas, but that may not mean that the actual peak airspeed was not higher? Having not included a great deal in their note, no one can then select such an early "read" from a later Report, and claim "manipulation". That is merely an extension of their evident desire not to give up "too Much".

Understandable, I think.

If not due to speed, why was the HS trimmed for that much NU? Or, is that a normal cruise Trim for the reported mach?
 
Old 13th Jun 2011, 14:42
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Cool

Hi,

Not sure I agree or understand all this. My take on the pitot
probe fault
modes and their results would be:
Honestly I do not think the pitot had a fault
The pitot worked exactly as expected by their certification
They do not have a fault
They were used out of the domain of specifications and certification
It's exactly the same Airbus tell about their plane:
Our aircraft and systems worked as expected ..
The aircraft had no fault.
Of course if you go out of the certification specifications ... you can have some weird outcomes ....
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Old 13th Jun 2011, 14:44
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jcjeant

"That's not seat TV screens installed in the Air France A330 ?
This in flight video system (info channel about the flight) was functioning or not"


I would have thought that in ALT2 the entertainment system would have been o/s.
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Old 13th Jun 2011, 14:44
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GY, “The probe tip is obviously the most 'cooled' part of the assembly and therefore the most susceptible to icing.”
Not necessarily so for ice crystals. Some regulatory thoughts on probe icing.
The small ice crystals might either block the tube because of the density of an accumulation – jam up, or some crystals melt and act as the glue for others to adhere to – an ice or ice / water block.
Thus the coolest point of a probe may not be the most likely place for ice crystal icing; the crystals tend to bounce off a cool dry surface.
The mechanics of the icing also depend on the crystal size or mass, the airflow path before and in the probe, and the anti-ice heating capability - heat flow.
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Old 13th Jun 2011, 14:57
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Bear:

You are assuming the THS trim was 3 degrees at the start of the incident, but that is NOT stated.

What we have is this:

The airplane approached the ORARO point. It was flying at flight level 350 and at Mach 0.82
and the pitch attitude was about 2.5 degrees. The weight and balance of the airplane were
around 205 tonnes and 29% respectively. Autopilot 2 and auto-thrust were engaged.
So we have a pitch trim of +2.5 degrees @ 205t and 29%. Anyone know what the THS would be at for this configuration? These are the start conditions.

Following this we are told speed was reduced to 0.8M at 2h08m07.

At 2h10m05 the AP and then AT drop. We are then told PF made a left NU input... climb to FL375..

At 2h10m51 we are told TO/GA was demanded and PF maintained NU inputs. Only NOW is the THS mentioned: The THS passed from 3 to 13 degrees NU in about 1 minute...

Assuming (ouch) this note is in chronological order, the THS trim was at +3 degrees at 2h10m51 and THEN increased. We don't know what it was at 2h10m05.

Honestly, I find the ability to somehow reorder or overlook significant parts of the timeline frustrating. I realize we are all trying to make sense of what little data we do have, but much of what is being thrown out here is such a jumble of the details we ARE TOLD in the BEA note, that it becomes an exercise in futility.

Unfortunately I can only conclude that there is an attempt being made to fit the foot to the shoe and not the shoe to the foot.
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Old 13th Jun 2011, 15:04
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Wrg:adiru1 bus adr1-2 to fcpc2

Savrin, this is from the June 2009 report:
Quote:
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.

This is from the 30 November 2009 report: Quote:FCPC2 (2CE2)/WRG:ADIRU1 BUS ADR1-2 TO FCPC2 (2 h 10)
ATA: 279334
Sou rce: *EFCS1
Identifiers: *EFCS2 Class 2, HARD
It is possible to explain this message by the rejection of ADR 1 by FCPC 2. It is correlated with the MAINTENANCE STATUS EFCS 1 and EFCS 2 messages.

Neither believes this is a wiring problem. What makes you insist WRG means wiring rather than warning? I realize there are WRN and WRG messages. There does not seem to be a distinction between them as listed by BEA.

A coincidence that would cause an AIRINC bus to quit working in only one direction would be surprising. And if it's not an AIRINC bus (or multiple AIRINC busses) then it's a multipin connector with inputs and outputs on the same connector. Why would only one direction fail? Why would it fail only in modest turbulence and not be discovered before that turbulence? That's too many hard failures at once for my tastes.

No doubt this is a wiring (WRG) problem, either internal in the PRIM2 or in the wiring from ADR1 ARINC BUS 1-2 from terminal to PRIM2 (includes, as JD-EE is correctly stated: the multi-connector). Wiring problems are rather easy to detect, send a test signal and compare with what is returned. It’s all day routine and takes place all the time, devices in control or in standby.
This is a class 2 maintenance message, no big deal if solely reported, it’s still receiving input data from ADR2 & 3
Trouble Shooting Manual is clear, replace FCPC2 = (PRIM2) and if fault persist check wiring from terminal to FCPC21]

Not easy to say in relation to the other problems. [B]“Need more data to compute!” e.g. what was crew-action on ECAM warnings, They should X-check speed and isolate ADR in error. Though job with 3 unreliable speeds but had to make a decision otherwise PRIM (in control) will make a decision which data to be used. BEA report doesn’t mention crew action on warnings neither which PRIM was in control. They only stated ADR 1 was rejected by PRIM in control.

Although only 1 PRIM is in control at a time, other PRIMS do X-check each other, if they disagree with output they will report (not mentioned in ACARS List) and probably transfer control to another consistent PRIM. PRIM 1 and SEC 1 messages most proberly be due to crew action, no correlated fault)

Could PRIM2 be in NORMAL LAW and others in ALTERNATE LAW, Very unlikely because ADR DISAGREE (due to PROBE PITOT 1+2,2+3,1+3) results in ALTERNATE LAW for all PRIMS.

And even when PRIM2 was in control and the only one in NORMAL LAW, ADR data is used for protection, IR/ accelerometers for feedback and control is by AP or SS both in NORMAL as in ALTERNATE.
Software or even program bugs? Very unlikely after all those years! few incidents where reported due to intermix of mod status ADIRUs and/or PRIMs, as far as I know never with disastrous outcome.
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Old 13th Jun 2011, 15:05
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Somewhere in the cobwebs of this old brain it seems that temperature is a big player to get true mach, especially up high. An SR-71 buddy of mine reminded me of this awhile back, but what do WE know? And ask a few Concorde pilots about this. So if the Airbus wants to use only dynamic and total pressures to calculate mach, I am wondering a bit.
You are right, air temperature is required, for accuracy. In the old days
of mechanical instruments, machmeters had only pitot and static input ports
and made assumptions about air temperature vs altitude. Non linear
cams and levers then translated that to mach dial reading, with the temp
parameter effectively factored in from the altitude capsule.

When air data computers arrived, it became much easier to plug the
temperature into the equation, as a synchro or pot input. The driver for
this being the need for much greater accuracy of measurement. Even
some of the earliest electromechanical adc's had tas and mach capability,
so not such a new idea....

Edit:

Went back to check and could not verify it. Referring to Collinson,
there's no mention of temperature in Mach calculations. You definately do
need temperature for true air speed calculation,, but can't confirm the
mach case. Perhaps someone else has more info ?...

Last edited by syseng68k; 13th Jun 2011 at 19:46.
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Old 13th Jun 2011, 15:13
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safetypee:

Thanks for the link. Here's what I read:

Modes of failure:
MODE 1:the Pitot tube is filled up with water. Pitothead obstructed by ice, the drain holes is free of ice. The airspeed indication is low or invalid.

MODE 2:The Pitot head and the drain holes are obstructed by ice. The Total pressure is trapped in the probe. The airspeed indication do not follow the barometric altitude
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Old 13th Jun 2011, 15:26
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safetypee, re # 1918: In an ADC, the temperature, (TAT or SAT) is used to compute TAS from the sound speed and Mach number.
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Old 13th Jun 2011, 16:03
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WRG

A33Zab : thank you for this

No doubt this is a wiring (WRG) problem, either internal in the PRIM2 or in the wiring from ADR1 ARINC BUS 1-2 from terminal to PRIM2
Now this is very interesting :

Could PRIM2 be in NORMAL LAW and others in ALTERNATE LAW, Very unlikely because ADR DISAGREE (due to PROBE PITOT 1+2,2+3,1+3) results in ALTERNATE LAW for all PRIMS.
Do you remember the timing for ADR DISAGREE in this accident sequence ? Time-stamp from CMC says 02:12 if I remember correctly. Can you tell us more about the difference between NAV ADR DISAGREE and F/CTL ADR DISAGREE ? Which system declares disagreement ?

Software or even program bugs? Very unlikely after all those years!
I never said it was likely or probable in general, quite the contrary. I said it was likely in this instance.

How many successive software versions for the PRIMs ? Last time I checked, I thought I saw version number 19.

Again, this is a highly reliable and efficient aircraft. Its design philosophy has certain consequences, however. These consequences are not about safety, but about who can be deemed responsible for what.

Herr Professor Schmid wrote about this much better than I could :
Pilot or Computer in Command
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Old 13th Jun 2011, 16:37
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Hi Svarin,

Thanks for that link to the very interesting document by Rechtsanwalt Prof. Dr. Ronald Schmid, Frankfurt am Main.

The aircraft designer must therefore, if necessary, even dispense with technical advances in order to ensure that the aircraft remains operable, comprehensible and thus controllable by the human being. Under no circumstances can technology be permitted to filter or block out information, much less take action on its own.
I agree with him completely. If Airbus FBW in ALT LAW doesn't have the same stall protection as Normal Law, then pilots should have the natural "elevator feel" returned to them, by disabling the auto trim function.

Last edited by rudderrudderrat; 13th Jun 2011 at 16:49. Reason: spelling
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Old 13th Jun 2011, 16:39
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Tech forum

eSpoiler

Has this information been compared to the details of the accident released so far and in particular the time line provided by the BEA?
As you will be able to read in the many posts this was considered and discussed in detail. The discussions are deep and here concentrated in all technical aspects of the tragedy.
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Old 13th Jun 2011, 18:05
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"...You are assuming the THS trim was 3 degrees at the start of the incident, but that is NOT stated..."

Yes, I am, and no, it's not. BUT,

"...At 2h10m51 we are told TO/GA was demanded and PF maintained NU inputs. Only NOW is the THS mentioned: [B]The THS passed from 3 to 13 degrees NU in about 1 minute..."

I know you read it this way, (three degrees @ 2:10:51),

I read it:

"Three degrees at 2:10:51 LESS "About a minute". This makes the Three degrees time @ +/- 2:09:51.

Since we are entertaining a loss of airdata @ 2:10:05, and the PF immediately input NU, it is illogical to assume the THS only Started its Trimming excursion at @ 2:10:51. . . If not, I defer to your conclusion.
 
Old 13th Jun 2011, 18:10
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"The aircraft designer must therefore, if necessary, even dispense with technical ...("ADVANCES"**)... in order to ensure that the aircraft remains operable, comprehensible and thus controllable by the human being. Under no circumstances can technology be permitted to filter or block out information, much less take action on its own."

**Dispense with .....

How about unwinding a few prior? (existing "advances")

IMAO, The one basic and glaring error in the "Philosophy" of fbw as practiced by the folks @ Airbus, is the following:

NORMAL is Rules based, and these rules are explicit. Flying is situational, and the computer doesn't have the capability to program for all of them.

Especially when the rules are not immediately available to foster "Situational".

Some problems require a format that is as yet u/a in the world of cyber.

Thought, Both Abstract and Intuitive.

A belief is a conclusion based on data. Faith is a format based based on Intuition, and "feel". When my beliefs are dashed, I rely on my Faith, which is in me, and my F/O.

The Wall of misunderstanding twixt the engineer and the Pilot will keep killing people until both understand the other. Please stop stubborn Pride from putting people at risk.
 
Old 13th Jun 2011, 19:35
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Ecam view

In image below I tried to show you ECAM WARNING AREA as it would looked like.
(As far as warnings are known to the public!)
I did priortized them as if they occured at the same time.
Only 7 lines (boxed in image) are in direct view, the header only of warnings not in view are in the overflow area at the RH side.
If crew action is performed and warning is cleared this line is removed (transferred to Status page) and lines in ECAM Warning area scrolls up.
MW and Cautions and aural sounds appear in real time with 1 sec. interval.

Flightphase Cruise, in other flightphases ECAM crewactions might differ
If QRH is leading crew action * REFER TO QRH/OEB PROC * is shown.

Flags on FFD are not shown and svoice from STALL can occur at same time as warningssounds.
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Old 13th Jun 2011, 20:21
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WRG

WRG

A33Zab : thank you for this


Quote:
No doubt this is a wiring (WRG) problem, either internal in the PRIM2 or in the wiring from ADR1 ARINC BUS 1-2 from terminal to PRIM2
Don't forget to mention connector, pins & s'u'ckets!

Now this is very interesting :


Quote:
Could PRIM2 be in NORMAL LAW and others in ALTERNATE LAW, Very unlikely because ADR DISAGREE (due to PROBE PITOT 1+2,2+3,1+3) results in ALTERNATE LAW for all PRIMS.
Do you remember the timing for ADR DISAGREE in this accident sequence ? Time-stamp from CMC says 02:12 if I remember correctly. Can you tell us more about the difference between NAV ADR DISAGREE and F/CTL ADR DISAGREE ? Which system declares disagreement ?
Flight Computer Data Concentrator 2 (FCDC2) aka EFCS2 is the detector for NAV ADR DISAGREE and declares ALT 2 LAW.
A F/CTL ADR DISAGREE msg doesn't exist, only NAV ADR DISAGREE.

From the report:

"The combined triggering of these monitoring processes has the following effects:

at the level of the EFCSs:
switch to alternate 2 control law,
unavailability of the rudder deflection limitation function which occurs, when applicable, ten seconds later."

Last edited by Jetdriver; 14th Jun 2011 at 03:37.
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Old 13th Jun 2011, 21:45
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Originally Posted by CONF iture
safetypee, I do agree, that's why I am asking again and again : Why don't we have access to those data ?
They are only data, why are they so secretive and so partially presented and so, in such a confused manner ?

3D animation is available too ...
Why should the BEA release such materials prior to the publishing of a report when practically no other accident investigation bureau does? I don't see you lambasting the NTSB or AAIB for not releasing data until they're ready to!

Originally Posted by rudderrudderrat
I agree with him completely. If Airbus FBW in ALT LAW doesn't have the same stall protection as Normal Law, then pilots should have the natural "elevator feel" returned to them, by disabling the auto trim function.
You're proposing a design change based on a single incident. Don't you think these scenarios have been played out to determine the design parameters? I suspect that the reason trim remains a sidestick function in Alternative Law would be in the case of an incapacitated crew scenario, where the remaining pilot has elevator and trim in their stick hand and throttles in the other, rather than having to dance between the stick, throttles and trim wheel with only two hands. What you're in effect proposing is a straight drop to Direct Law upon loss of air data.

Originally Posted by bearfoil
The Wall of misunderstanding twixt the engineer and the Pilot will keep killing people until both understand the other. Please stop stubborn Pride from putting people at risk.
But bear, as yet there's no evidence of a "wall of misunderstanding" in this accident because we don't have all the facts, yet you and many others (barely any of whom are current Airbus pilots) are pronouncing it as if you have the facts in your hands rather than simply regurgitating prejudice.
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Old 13th Jun 2011, 21:55
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Originally Posted by DozyWannabe
I suspect that the reason trim remains a sidestick function in Alternative Law would be in the case of an incapacitated crew scenario, where the remaining pilot has elevator and trim in their stick hand and throttles in the other, rather than having to dance between the stick, throttles and trim wheel with only two hands.
How do you cope with rudder trim?
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