PPRuNe Forums

Go Back   PPRuNe Forums > Flight Deck Forums > Tech Log
Forgotten your Username/Password?

Tech Log The very best in practical technical discussion on the web


Closed Thread
 
Thread Tools
Old 28th Feb 2012, 22:23   #1401 (permalink)
 
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,122
tly

roulishollandais

Better still with two only Pitot Tubes ! These two, if designed differently, but to spec/reg, will never fail simultaneously, the fail chain cannot be identical. It does not eliminate failure, only failure in concurrent fashion.

Anomalous design.

Three of the identical design/manufacture are three blind mice, identical triplets.

Reasonably stupid.
Lyman is offline  
Old 29th Feb 2012, 00:45   #1402 (permalink)
 
Join Date: Jun 2009
Location: somewhere
Posts: 400
Amount of probes

Quote:
will never fail simultaneously
They didn't fail and certainly not simultaneously. if they clogged up for more than 10 sec. at the same time
the ADR DISAGREE message would have been displayed at ~ 02:10:15 ISO 02:12:xx.

First RH(FO) Pitot freezed up, 5 sec. later LH probe, a few sec. later STBY probe which returned to normal value for a brief moment.
@02:10:20 LH and STBY returned - but faulty -.
@02:10:40 LH was back on line (correct displayed) and 5 sec. later also RH probe. (FDs returned and needs 2 valid speeds)
At that time they switched over to ADR3 as source for RH PFD,

IMO If they didn't had done that action they would have had proper and coherent speed displays on both LH as RH PFD. (35 sec. after start of event)

ADR3 returned at 02:11:10.
ADR 1 returned in ~30 sec., ADR 2 in ~35 sec. and STBY in ~1 minute.

loss of speeds thereafter caused by hi AOA & NCD ADIRU output.

@RRR:
Don't know what you mean with 'sub'heated, its self temp. controlled.
The heat applied is inversely proportional to the temperature of the probe.
A33Zab is offline  
Old 29th Feb 2012, 11:01   #1403 (permalink)
 
Join Date: Jul 2009
Location: France - mostly
Age: 74
Posts: 1,689
Quote:
It does not eliminate failure,...
Right, so survival will always depend on correct application of the appropriate procedure. Would it be very difficult to have the pitch and power appropriate for the flight condition displayed on the ECAM? Would an "Ice particle detector" be useful?
HazelNuts39 is offline  
Old 29th Feb 2012, 14:36   #1404 (permalink)
 
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,122
Hazelnuts39

Right. Full circle then. There have been dozens of theories, and points of view, not to mention politics. You bring us back to the fundamental focus of this crash. If it is to be instructive (at such a cost), we need to address some few things.

BUSS not important? Do posters here dismiss its possible ability to save the flight from the Sea? Add BUSS, and the a/c lands in Paris. Add PITCH/POWER, CRM, high altitude upset training (or at least emergent resources to instruct),(check lists to address it), the pitots are less important. Things break, but procedures are developed for that eventuality.

Particle ID? Perhaps a high speed version of a Particle separator? Design makes progress, but the impetus for change is lessened when players seek scapegoats.

We will see how far the authority goes to be aggressively honest, in the interests of the pilots and the passengers. If this is but a reprise of Rudder hardover, fuselage fracture/disintegration, and several iterations of a fundamental flaw must ultimately goad the players into change, it will be sad. Also, not unexpected.
Lyman is offline  
Old 29th Feb 2012, 15:06   #1405 (permalink)
 
Join Date: Jun 2009
Location: somewhere
Posts: 400
HI HN39,

I suppose you mean translating the UAS Pitch/Power table into a formatted ECAM message?

Then the parameters required are: FL, Flight mode (CLB, Cruise or Descent), GW and F/S config.

- FL comes from Air data (or GPS ALT have to be used)
- GW normally comes from FCMC (Fuel Control Monitoring Computer),
FE computation is used if both FCMC fail. so available.
- F/S Config wouldn't be any problem.

- how would it determine Flight mode?
A33Zab is offline  
Old 29th Feb 2012, 15:10   #1406 (permalink)
 
Join Date: Oct 2011
Location: Lower Skunk Cabbageland, WA
Age: 64
Posts: 276
Talking I keep saying this; don't read

Everybody's got an opinion. I've got a bunch of them!

I hope that they fix every single possible thing that might have
contributed to the confusion and crash, no matter how tentative. Sure, that would cost lots of $$$, but the mass extinction of 228 lives is just unacceptable. The bottom-line-calculations of cost-benefit-analyses are, to me, an obscenity.

Flying has famously gotten more and more safe, in statistical terms. But for me, the sheer horror of this kind of death trumps everything else. It's still not safe enough for me.
Organfreak is offline  
Old 29th Feb 2012, 15:45   #1407 (permalink)
 
Join Date: Jul 2009
Location: France - mostly
Age: 74
Posts: 1,689
Quote:
Originally Posted by A33Zab
I suppose you mean translating the UAS Pitch/Power table into a formatted ECAM message?
No, I would think more like a back-up for the UAS 'memory item':

IF in TOGA: .... TOGA/15
ELSE, below FL100: CLB/10; above FL100: CLB/5
THEN: Refer to QRH
HazelNuts39 is offline  
Old 29th Feb 2012, 15:47   #1408 (permalink)
 
Join Date: Mar 2000
Location: canada
Posts: 150
It costs a bit more to avoid (divert around) CBs. But it's SOOOO much safer. You don't get ice on your pitot tubes when in the clear. And you get home in one piece. Some people just don't seem to get it. Unbelievable!!!!!!!
thermostat is offline  
Old 29th Feb 2012, 17:15   #1409 (permalink)
PJ2
 
Join Date: Mar 2003
Location: East of the sun, West of the moon
Posts: 2,151
thermostat;

There is no evidence that AF447 was flying "through a CB". There is often (but not always) some turbulence associated with cloud but the levels of vertical 'g' shown in the traces are not significant in terms of "CB" penetration...they're pretty ordinary levels. I've seen much worse, in cloud and clear air.

Before the conclusion is drawn that the statements below advocate "flying into/through thunderstorms", some appreciation of the entire issue of weather and radar-use is required.

On the day of the accident as part of the initial responses on PPRuNe I posted a long discussion on the use (and abuse) of radar, here.

One of the first principles of the use of any radar by flight crews is to know that it does not paint ice crystals, therefore if one cannot see over-hangs or thin cloud composed entirely of ice-crystals, (almost certainly the case here), one cannot avoid flying through such weather, nor is avoidance always necessary. It depends more on the potential for turbulence than it does avoiding "all cloud", (FYI, all cloud above the freezing level is ice crystal; one does not/cannot avoid all cloud, ergo one cannot avoid flying through ice crystals).

The problem of momentarily blocked pitot tubes is extremely rare. Appendix 7 of the BEA Second Interim Report, which see, lists the events which occurred to Airbus. I have had such an event but on a B767 so it happens but given the millions of ice-crystal-cloud-penetrations that occur each year without result, "avoiding all cloud" isn't realistic. Clearly, avoiding all CBs is mandatory but that is well understood and the techniques for avoidance known.

Hello HN39;

If I may be forgiven as I know this has been discussed many times in previous threads, but for the benefit of those who may not have come across the discussion, regarding the UAS Memory items the A330 Flight Crew Training Manual states, in part:

PART 1: MEMORY ITEMS
If the safe conduct of the flight is affected, the flight crew applies the memory items. They allow "safe flight conditions" to be rapidly established in all flight phases (takeoff, climb, cruise) and aircraft configurations (weight and slats/flaps).

The memory items apply more particularly when a failure appears just after takeoff. Once the target pitch attitude and thrust values have been stabilized, as soon as above safe altitude, the flight crew will enter the 2nd part of the QRH procedure, to level off the aircraft and perform trouble shooting. This should not be delayed, since using the memory item parameters for a prolonged period may lead to speed limit exceedance.

PART 2: TROUBLE SHOOTING AND ISOLATION
GENERAL
If the wrong speed or altitude information does not affect the safe conduct of the flight, the crew will not apply the memory items, and will directly enter the part2 of the QRH procedure.


Note that the FCTM makes it clear that troubleshooting, "...should not be delayed since using the memory item parameters for a prolonged period may lead to speed limit exceedance."

For others, (as I believe HN39 knows this), a pitch attitude of 5 at FL350 results in a climb of about 900 to 1500fpm with commensurate very gradual loss of airspeed/energy. While this doesn't lead to a stall, any pitch attitude higher than 5 will result in a loss of energy, a 15 pitch attitude, which is unheard of in a transport aircraft at cruise altitude, will rapidly lose energy and airspeed as seen, thus the FCTM admonition to get the QRH out quickly and set pitch/power according to the tables.

The memorized items never call for a 10 or 15 pitch attitude but the attaining of such attitudes may not have been intentional and may be the result of over-controlling; - there was an almost-instant rearward stick movement to 10+ with a commensurate pitch attitude achieved of about 12 initially, going to 17-18 within about 30" of the UAS event.

If one changes pitch attitude and/or power from what was stable flight prior to the UAS event, except for using GPS groundspeed as indicated in the QRH checklist (below the memorized items), there is no way to tell how much energy is being lost with higher pitch attitudes, and one will quickly lose "where one is" in terms of airspeed/energy levels, so it is urgent that pitch/power be set quickly if one is going to alter pitch attitude at all.

Part 2 of the QRH Procedure looks something like this:





In my opinion as a (retired) A330 captain, the "safe conduct of the flight" was never an issue with regard to AF447, (and wasn't with all other similar UAS events).

However, "safe conduct" is a subjective, not objective decision-point in a critical drill/checklist and I think that is a problem that can lead the crew into an inappropriate and unnecessarily quick response.

A loss of airspeed indication is not an emergency, nor was immediate action required, especially of kind executed here which was uncoordinated, unilateral actions (meaning the absence of the use of SOPs) by the PF which went unchallenged by the PNF.

As discussed previously, all the crew had to do was to maintain pitch attitude and power setting as per the UAS QRH checklist while the abnormality was announced by the PF and the QRH called for so that precise pitch and power settings could be determined. There was no need to set a different pitch attitude at all.

I think this is partly 1) a drill/checklist problem, 2) partly a training problem and 3) partly a cockpit discipline problem.

1) the drill/checklist is poorly-written and confusing as to correct response, 2) their UAS training was done quite some time prior to this event on an A320 simulator, with the UAS occuring right after takeoff (requiring TOGA/15) and not at cruise altitude which didn't require any action at all as the "safe conduct of the flight" was not in question, and 3) the cockpit discipline matter has been thoroughly discussed but there was a leadership-followership issue which was (and still is) a problem when two F/Os are in command of the flight, and the captain did not address how drills would be handled.

Last edited by PJ2; 29th Feb 2012 at 18:38.
PJ2 is offline  
Old 29th Feb 2012, 19:11   #1410 (permalink)
 
Join Date: Oct 2011
Location: Lower Skunk Cabbageland, WA
Age: 64
Posts: 276
PJ2:
Quote:
There is no evidence that AF447 was flying "through a CB".
Really? Now re-reading the entire Interim Report #3!
Organfreak is offline  
Old 29th Feb 2012, 19:31   #1411 (permalink)
 
Join Date: Oct 2011
Location: Lower Skunk Cabbageland, WA
Age: 64
Posts: 276
Replying to myself:

You are correct! Unless this, on p. 72, means something:

Quote:
Note: at around 0 h 30 the crew had received some information from the OCC on the presence of a convective zone linked to the ITCZ between SALPU and TASIL.
Plz pardon my ignorance.
Organfreak is offline  
Old 29th Feb 2012, 19:54   #1412 (permalink)
PJ2
 
Join Date: Mar 2003
Location: East of the sun, West of the moon
Posts: 2,151
Hello Organfreak;

Re "ignorance", no worries! I've made some glaring errors in this discussion in the past!

Re CBs, there was indeed a lot of convective activity in the SIGMETS for the ITCZ (Refer to Tim Vasquez's fine work in the early threads) and there were diversions on the part of some of the flights doing the crossing that night. But there is always convective activity in the ITCZ and almost always there are ways through it...done it dozens of times, although on the Pacific. One just watches the radar like a hawk, changing scales, changing tilts to "take slices" of the moisture levels and potential clearances of the tops, turns down the lighting and watches outside. When one is "in cloud", (ice crystals) it is rarely turbulent but sometimes a few bumps occur.

It can be quite misleading to look at a satellite image of such convective activity, superimpose AF447s route on top and conclude that they went through CB's, (not saying you're saying this, just saying you can't judge/conclude what any one aircraft/crew may have encountered/experienced by looking at such large-scale images). There are no conclusions to be drawn from the fact that the flights before and after AF447 made slight diversions.

I wouldn't for a moment say that the circumstances the crew faced were straightforward or just a bit more than routine. They would be quite disconcerting, which is the reason both training and SOPs are emphasized...to keep the process slow, deliberate, disciplined and on-track so that mistakes aren't made in procedure. "Doing nothing" accomplishes two things...it calms one to permit assessment and action according to SOPs, and it prevents one from making irreversible mistakes (like shutting down wrong engines, etc). Except perhaps for the rejected takeoff and (obviously) TCAS/GPWS/Stall warnings, there are no events which require immediate, instant actions on the part of the PF alone. Loss of airspeed indication is not an emergency, it is a minor abnormal for which there is ample guidance and resources.
PJ2 is offline  
Old 29th Feb 2012, 20:47   #1413 (permalink)
 
Join Date: Jul 2009
Location: France - mostly
Age: 74
Posts: 1,689
Hello PJ2;

Thank you for pointing out that I was mistaken when I referred to the memory items. I regret that I didn't think a bit longer before writing that quick reply to A33Zab's post.

Of course one would hope that after AF447 no flight crew will ever be as ill-prepared for an UAS situation at cruise level. But, if I may rephrase my original question - would it help prevent future accidents if sophisticated Flight Guidance and Aircraft Monitoring systems, having rejected three sources of airspeed information as unreliable, and 'knowing' conditions such as configuration, weight and altitude, provide more specific information as to the appropriate response?
HazelNuts39 is offline  
Old 29th Feb 2012, 21:01   #1414 (permalink)
 
Join Date: Oct 2011
Location: Lower Skunk Cabbageland, WA
Age: 64
Posts: 276
Thanks, PJ2, for an erudite and thorough reply.

I think I (and likely many others) may have been led astray by the BBC documentary that came out before the recorders were found. In it, a hotshot meteorlogist spent quite a bit of effort in demonstrating what he thought the weather was, based on satellite images.

And of course (not addressing CB now) there was the reported "whooshing sound" in the cockpit picked up on the CVR, that BEA speculated was probably ice crystals.
Organfreak is offline  
Old 29th Feb 2012, 22:27   #1415 (permalink)
Moderator
 
Join Date: Apr 2001
Location: various places .....
Posts: 5,334
Link to Thread No. 2
john_tullamarine is offline  
Closed Thread
 
 
 


Thread Tools


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT. The time now is 15:10.


vBulletin® v3.8.7, Copyright ©2000-2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
1996-2012 The Professional Pilots Rumour Network