GarageYears

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.

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 ...

bearfoil

Garage Years

"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?

jcjeant

Hi,

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 ....

promani

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.

safetypee

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.

GarageYears

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:

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.

A33Zab

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.

syseng68k

gums, 1842
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 ?...

GarageYears

safetypee:

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

Modes of failure:

DJ77

safetypee, re # 1918: In an ADC, the temperature, (TAT or SAT) is used to compute TAS from the sound speed and Mach number.

Svarin

A33Zab : thank you for this

Now this is very interesting :

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 ?

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

rudderrudderrat

Hi Svarin,

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

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.

RR_NDB

eSpoiler

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.

bearfoil

"...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.

bearfoil

"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.

A33Zab

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.

A33Zab

Don't forget to mention connector, pins & s'u'ckets!

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:

DozyWannabe

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!

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.

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.

rudderrudderrat

Originally Posted by DozyWannabe
How do you cope with rudder trim?