Unreliable Airspeed Indications on Modern Aircraft
Its interesting that prior to the Malaysian B777 upset near Perth in Aug 2005, Boeing did not provide a QRH item for this, as due to design features,it was deemed that it was impossible for this to happen. They do now apparently.
Did Airbus always provide this guidance? Perhaps their design differs.
Looking at the FCTM, following the QRH and then doing nothing may put you deep in the do-do.
"Apply the initial actions of the UNRELIABLE SPEED INDICATION QRH procedure from memory as they quickly provide a safe flight condition in all phases of flight and aircraft configuration."
"After applying the QRH procedure, and when the aircraft flight path is stabilised, attempt to identify the faulty ADR(s). Once the faulty ADR(s) has/have been positively identified, it/they should be switched OFF. This will trigger the corresponding ECAM procedure, which should be applied."
CL thrust and 5 degrees at say 2000ft below Max Alt in convective WX, that does not leave you long to troubleshoot ! :o
This may be one of those situations where blindly following the QRH may have caused more trouble than good.
"The unit operating by gyroscopic principle and driven by airflow or an electric motor, which provides heading (direction) references relative to a preset heading in degrees of the compass. Also for the flux unit detector which senses the earth's magnetic field and uses this data to correct for gyro drift. Typical parts are gyro, rotor, bearing, etc."
WRT elucidation of what the ACARS messages meant in detail from our esteemed colleagues earlier. I gather the ISIS fault may have resulted in loss of ATTitude information from the standby instruments. Someone said they would try to work out exactly what would have been lost from the PFD - but I haven’t seen any post in relation to it since. I believe that IRU’s continue to send valid data if faults only lie with AD part of ADIRU’s. Presuming that main displays loose airspeed , possibly ALTitude also. But would they still have had ATTitude cues on main displays?
PJ2,
I do share your concerns, but unfortunately I do not have an answer to your rightly pointed doubts.
I hope someone in this forum may enlighten us, because I see no point on discussing unreliable airspeed procedures, without any kind of attitude display...if that was the case.
theamrad;
Unless there is more to the ATA codes than those who have already done some translating here we may be stretching the limits of available information.
I am certain that there are many more Class 3 maintenance messages available but so far we have not seen any.
In short, you ask good questions (as many here have) but given the information we have, the questions can't be answered with any accuracy.
aquadalte;
Quote:
I see no point on discussing unreliable airspeed procedures
Precisely. While we have some tiny specifics, everything remains possible, despite Mr. Occam.
jauh;
Quote:
It would be nice if people actually read stuff instead of just posting - we've gone over the same points here at least three to four times already
Doh!..My constant complaint! - can you believe people don't read previous posts?, sorry! I got greenspinners but missed yours, thank you. I think that clarifies the unit referenced - did it clarify the "cabin vertical speed" message too? Tx...
aquadalte;
Notwithstanding greenspinner's excellent work, the list of ACARS messages you've quoted from the AvHerald differs in the details from the ones posted and examined here:
02:10Z:
Autothrust off
Autopilot off
FBW alternate law
Rudder Travel Limiter Fault
TCAS fault due to antenna fault
Flight Envelope Computation warning All pitot static ports lost
02:11Z: Failure of all three ADIRUs
Failure of gyros of ISIS (attitude information lost)
02:12Z: ADIRUs Air Data disagree
02:13Z:
Flight Management, Guidance and Envelope Computer fault
PRIM 1 fault
SEC 1 fault
02:14Z:
Cabin Pressure Controller fault (cabin vertical speed)
I tend to share your scepticism over the AvHerald interpretation. It appears not to be a logical as that presented by greenspinner (Occam's Razor here) but also it is not internally consistent.
Why would an ADR disagree message come after failure of all three ADIRUs? They can hardly be disagreeing (a less severe kind of failure) after they have failed (which generally means a 'hard' failure), I also don't see how they could take two minutes to "disagree" after "all ports were lost".
Quote:
Originally Posted by JRF
How can anyone rule out a bomb in this day and age? ... other forms of breakup/fire/explosion theories
Again, I am not saying this is the case. Is there a reason why it can not be the case? Rule it out please!
The main way to "rule it out" right now, based on the limited information confirmed, is that the sequence of ACARS messages which appears to correspond to the progressive event(s) which resulted in the loss of the aircraft are dominated by systems connected with flight controls, auto-flight and navigation.
The only message which could be even tangentially related to a bomb or catastrophic structural event appears to be the last one - the cabin vertical speed one - which could be related to explosive decompression or to loss of cabin structural integrity.
that implies that any structural failure occured as a consequence of the preceding event, and was thus a symptom and not a (primary) cause.
Last edited by Saab Dastard : 6th June 2009 at 01:39.
Reason: Tidying up
I think it is very important to disagree with any and all presented information until we know it is from the primary source and the primary documents, (the Airbus 330 TSM, MMEL, etc) or has been established as irrefutable. The ACARS documents are good but we dont' have the originals.
I think it is wise to reserve judgement on an "expert's" interpretation and prefer a "college of experts" such as reside here, all disagreeing until "what is" is no longer disputable. I think because of the circumstances, any evidence must meet particularly high standards and theories/conclusions wholly avoided. Hind-sight bias is still an operating factor.
Ok PJ2 – not being totally familiar with the airbus I had thought it might be possible to pull more detail out – but looking back over your second last post and this mornings posts again – I understand the situation re available codes exactly now. Sorry for hashing over the same stuff again.
it is known and agreed that ISIS consists of a gyro system among other sub-systems. That's why it is sorted at 34-22 Directional Gyro & Indication. But there is an Air Data part as well. And an AP interconnect. And GPS, ....
To me, the actual message does not indicate that the gyro of ISIS is broken, which in turn means that its Attitude Indicator would be lost.
The ATA code just tells that there is some problem with ISIS, but not which one. Could have been the ISIS display or the air probe inlet clogged or... except we can decipher
Quote:
1,,,,,,,ISIS(22FN
which I am not sure about, hence my questions which I am sharing with PJ2.
Unfortunately my next access to AMM / TSM has to wait until Monday. And yes, I do read almost every single post, including yours. :-)
So, pitot/static are two complete different systems?
And you are a pilot?
Or a "couchpilot"?
When discussing a tragedy like this
"down to basic"!
20 computers are controlling an airplane!
But the "basic" is the pitot/static-system!
I think it is very important to disagree with any and all presented information until we know it is from the primary source and the primary documents, (the Airbus 330 TSM, MMEL, etc) or has been established as irrefutable. The ACARS documents are good but we dont' have the originals.
I think it is wise to reserve judgement on an "expert's" interpretation and prefer a "college of experts" such as reside here, all disagreeing until "what is" is no longer disputable. I think because of the circumstances, any evidence must meet particularly high standards and theories/conclusions wholly avoided. Hind-sight bias is still an operating factor.
Concur, but in addition to hind-sght bias the thread inevitably suffers from recentism, especially when a recent post appears to be more readily understood than an earlier, or when the earlier information is distributed over several pages.
This may indeed be a case where the forum format is weak - in that good information gets ignored by even the most well-meaning poster, who reads (or remembers) inevitably the more recent data preferentially. A wiki-type format - where the information is more of a living document - would have strengths in a case like this (after all, the "real" investigators use report drafts, not emails back and forth, to arrive at a final agree and reviewed version...)
One question I have - there has been some discussion of the A330 (specifically) and other Airbus (due to the all-operators telex AB sent out) unreliable airspeed procedures. Does anyone have access to a public domain source for these (obviously the A330 is the ideal case there). I will confess to an ulterior motive, not entirely related to this thread, but I think such items would be of value here as well.
I think it was the AeroPeru B752 accident in '96 that led to Boeing introducing the Unreliable Airspeed Memory Items & checklist (the checklist already existed when I did my initial back in 2004)
Airbus is recommending/reminding operators and crews of the Unreliable airspeed checklist based on their preliminary findings.............
What my wife calls me is strictly between she and I.
Again, my writing confuses. I'm well aware of the systems you describe and have used those "20 computers" and the 330's hundreds more many times - but, (and it's a very small, fussy point), one cannot use, (as the AvHerald apparently did), the term "pitot static port" meaningfully, especially with reference to ATA numbers - there are no such things; - they should know better, frankly but there it is. There are pitot tubes or probes, and there are static ports, which are separate inputs which comprise the pitot-static system into the 3 ADIRS as I'm sure you know. That's all I meant.
i joined this forum because of the catastrophy we re going trough.i m a former B747 100/200/300 AF captain.i flew many times from DKR to EZE with our s cargo planes.at that time we had only AVQ 10 radar WX.monochrome of course.
so to say that we were experienced enough to do the job ..
as a senior captain,i trained a lot of F/O not to care about the position report in case of WX deviation.who cares?you are on your own.there s no radar coverage.what you need is common sense.............enough fuel .
for the rest you can easily deal with your T CAS.
and if you have any delay for your next position dakar control don t bother
what you said in a trhead above is terrific.
quote.......................................
It doesn't take a genius to conclude that the line is not only hoping for, but trying to lay the foundation for, pilot error.
How convenient, predictable, and deceitful.
For an aircraft that makes much of its automation, to the exclusion of the necessity for brilliant airmanship, only to see such aircraft dump the flight on the humans when it can't keep up seems, what, ironic??
.................................................. ............................................
i said the same things; in a french forum.i was kicked out.whathever
fortunetly the NTSB seems to be in
best regards
In a way you are right.
The B-747 and the Sikorsky-S61
have combined pitot-tubes.
Therefor the confusion.
Pitot+static in on tube.
Thats what Clinton+Obama flies around with.
Lower than 50000 ft.
in that good information gets ignored by even the most well-meaning poster
Touché. We've all had both sides of that experience - we work hard to put something together we think is pretty and helpful, and voilà, 3 pages later it virtually doesn't exist for someone not reading back. BTDT.
On the Airbus AB, I know of no sites; only the AD's I think are available.
I note that very quickly after the TAM A320 accident at Congonhas, Airbus issued a Telex AB cautioning crews to ensure that the thrust levers were both set to IDLE even if one reverser was locked out. I wonder what the present Telex AB means? Perhaps that question has already been answered somewhere but we'll have to wait a bit longer.
connector;
She's well thank you and very tolerant...has to be - married a pilot.
You're right - I had forgotten about the combined pitot-static tube, thanks.
PJ2: Nobody knows anything that detailed yet so on what basis would such an AD be issued?
Digging might get you amazing results if you have time and patience. Background section of the related DGAC AD (2001-354) might be the right way.
Connector: Thanks Mad(flt), for your EASA - AD list. But thats not how the system works. Maybe it shows up next week.
In terms of how the system works, it is easy to explain to those fortunate enough not to deal with regulatory bodies - an SB from Airbus is already in the works and that triggers an AD from DGAC. If DGAC is in hurry they can issue an AD very quickly but I strongly doubt in this happening ahead of Airbus . That IS how it works, with any regulatory body (FAA, EASA members, TC, CASA and the others).
Besides, compliance date for that AD was 6 years ago (in 2003) so AF already replaced all the pitot tubes, at least once. Second replacement, mentioned today, might require more info - like a new urgent SB from Airbus or an even faster AD from DGAC.
Has AF revealed whether or not the crew requested and received extra fuel for weather contingencies, as the Iberia crew reportedly did? I've read both long threads completely, but if this answer was posted I didn't see it.
IMHO, the failure of IR1, IR2, IR3 and ISIS was at 02H11m. Jauh, If you're a pilot, you should know that, that is enough to turn an A330 (or any other heavy aircraft at night, in clouds and without a clue of what is going wrong with your aircraft), into a flying brick.
In those message reports there are warnings (WRN) and there are failures (FLR), and the above said components were allegedly failed on that report.
I also think that the Cabine pressure V/S advisory, means both CPC's were off and that message was a warning that Cabine Pressure could only be Manually Controlled.
To look for the reason (or reasons) of those failures is just another discussion, because for me, what this failures mean is that there is no reason to be discussing unreliable air speed indications once you have no ATTitude to grab to.
I must tell you that it is very disturbing to imagine the failure of all ADIRU plus ISIS. I never though this would be possible. Pitot and Static failures would only fail the ADR part of the ADIRU's, therefore one would still be capable of maintaining unreliable speed procedures (and attitude). There must have been something very disturbing and very grave to breack all of those components. Even the Emmergency Electrical Configuration status would leave you with one AP operational...
I got greenspinners but missed yours, thank you. I think that clarifies the unit referenced - did it clarify the "cabin vertical speed" message too? Tx...
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