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AF447

Old 24th Jun 2009, 06:08
  #2241 (permalink)  
 
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AMF:
It's a assumption to believe the autopilot did so as a result of equipment malfunction, and it was the first recorded ACARS message. If AP parameters (say, pitch, roll, trim limits due to altitude hold, etc) were exceeded and it thus disengaged, what were the forces acting on the aircraft that caused those exceedences?
"first recorded ACARS"... no, they are unsorted and should be sorted in order of priority, plenty are triggered at the same time.
AP & A/THR are kicked off because the aircraft go to ALERNATE LAW2 as a consequence of the unreliable AIR DATA, etc. No exceedences of forces acting on the aircraft are needed to do that, but it certainly won't help for crossing a [undetected?] tropical CB.
See above post, the ACARS are now published in their integrality.

S~
Olivier
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Old 24th Jun 2009, 06:25
  #2242 (permalink)  
 
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Eurocockpit reports another AF document pointing at a known problem with pitot probes:
French version: page 1, page 2
English version: page 1, page 2

Note that this AF maintenance from Aug. 2008 states that:
The purpose of this NT is to gather information in order to confirm the involvement of pitot probes in case of "NAV IAS discrepancy"
At the time of the creation of this NT, a case on THT and six cases on A340 AFR have been reported
Furthermore, if I'm not mistaken, several warnings reported in this note are found in the ACARS messages received from AF447
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Old 24th Jun 2009, 07:57
  #2243 (permalink)  
 
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How to access the Air France documents

The links in the post above don't work, but if you click on them, then copy and paste the address into the address bar and hit return, you will see the document. The address still looks the same, but it is not linking from a "foreign" site if you do this and hence is OK.
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Old 24th Jun 2009, 08:43
  #2244 (permalink)  
AMF
 
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takata Quote:

"first recorded ACARS"... no, they are unsorted and should be sorted in order of priority, plenty are triggered at the same time.
AP & A/THR are kicked off because the aircraft go to ALERNATE LAW2 as a consequence of the unreliable AIR DATA, etc. No exceedences of forces acting on the aircraft are needed to do that, but it certainly won't help for crossing a [undetected?] tropical CB.
See above post, the ACARS are now published in their integrality.

S~
Olivier
My point being, crossing a (undetected?) tropical CB would, in addition to acting on all the aircraft's axis, also raise hell with the air data, especially in terms of miscompares. A 100mph vertical gust equals about 9,000 fpm. In a fast-building CB the measured-by-water droplet vertical velocities can approach twice that....18,000 fpm, and the real updraft speed (since droplets move more slowly) even higher.

There isn't an aircraft designed that can cooly transition though something like that even with all systems functioning. Inadvertent CB Penetration 101 includes not only disabling any altitude hold fuction and accepting altitude deviations, but also accepting radical airpspeed fluxuations, not only because the indications may or will become unreliable in relation to true aircraft speed, but also because the multiple Air Data systems may become unreliable in relation to each other due to unequal forces acting on the aircraft.

Meanwhile, with these unreliable and conflicting indications, a hand flying pilot, possibly in severe turbulence, must still maintain the reality as it exsists out on the wing...airflow somewhere between low-speed buffet and mach buffet, with the margins between them fairly close at high altitude. Overspeeding is a world of hurt just as big or bigger than stalling. And at high altitude and weight the pilot must stay within those close buffet margins while not executing anything near the rolling action he could at lower altitudes to deviate his course around more weather or counteracting turbulence and/or dutch roll. To do so at that high altitude risks a load factor-induced stall through a raised low-end buffet margin.

Worst of all, all those conditions can and do exist in the clear air above developing CBs, and inside those that don't contain enough moisture at that paint clearly or produce icing of any significance.
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Old 24th Jun 2009, 09:30
  #2245 (permalink)  
 
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Is there suggestion of an unrecoverable upset ?

I start by announcing that I am just a 200 hr Cherokee driver.

Is the suggestion that severe weather/turbulence/updraft etc caused by a CB and with the aeroplane in "coffin corner" of the flight envelope caused an upset ?

Is there then postulation that the upset was of such a magnitude that even when the aeroplane got to (say 10,000 ft) a level where the available speed range was greater and manoeverability and controllability higher it could not recover ?

Is this hypothesised to be through speed / attitude ?

I thought only the "T" tails (discovered I think by G-ARPY) got into a locked in unrecoverable condition.

These are questions so be nice to me please.

Dave

Last edited by Dave Gittins; 24th Jun 2009 at 09:33. Reason: carp spelling
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Old 24th Jun 2009, 09:38
  #2246 (permalink)  
 
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I agree with you desitter. Finding pieces and personal items from Air India to hand in to authorities was hard for me. Posting photos of seats etc from AF must be unbearable for relatives and doesn't add to any professional understanding.
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Old 24th Jun 2009, 09:47
  #2247 (permalink)  
 
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Yes, there have been suggestions/speculation in these pages & elsewhere since day 1 that a high alt. upset might have occurred..

Aircraft of this type can remain out of control, in other modes than the 'T-tailed deep-stall'... e.g. the spinning characteristics are not explored fully during flight-test.
And of course, if IMC instruments are not all available, even a spiral dive can easily become critical.

Reading an assortment of the past posts should give you a good background to what might be possible or not

Last edited by HarryMann; 24th Jun 2009 at 10:44.
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Old 24th Jun 2009, 10:16
  #2248 (permalink)  
 
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AMF

Nice scenario ... for Hollywood.

Last edited by DJ77; 24th Jun 2009 at 10:17. Reason: cosmetic
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Old 24th Jun 2009, 12:09
  #2249 (permalink)  
 
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DJ77

You have to chill mate.
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Old 24th Jun 2009, 13:59
  #2250 (permalink)  
 
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AMG65 and AMF
You have to chill mate.
No overheat here. And I do not mean anything personal.

But AMF's description should be supported by references to theoretical or experimental studies or even personal experience (if any). Otherwise, it looks like fiction.

See, for example, Tim Vasquez's analysis: no updraft higher than 40kt (about 4000 ft/mn), not "18000 ft/min, even higher" as mentioned, and no heat sink signature observed.

Of course, I don't intend to suggest that the pilots were not faced with a very severe situation flying in (or close to) bad weather without reliable airspeed indication.
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Old 24th Jun 2009, 14:31
  #2251 (permalink)  
 
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Hi there.
The more I think to the debris location and to the last minutes of the AF 447, more confuse the whole picture becomes. Here is an agregated map from different sources (brezilian AF, NESDIS and OSCAR/NOAA, tim Vasquez analyze,...).
http://img199.imageshack.us/img199/6099/crashsite2k.jpg
OSCAR - Ocean Surface Currents Analyses - Realtime
QuikSCAT
The surface current and wind fields are derived from satellite observation from June the 1st to June 12 (see Quickscat and NOAA databases): the currents rotate between 3N and 4N from a S-SW-->N-NE direction to a S-SE-->N-NW direction and remain <0.10m/s. The drifting buoys can give clues for the following days. The wind was oriented to the west, between 4-5 kts and 15 kts. You can get clues about the offshore swell via EVISAR/ASAR (S-SW-->N-NE direction).
Atlantic Ocean / Swell animation from ENVISAT ASAR instrument / Movies / View / Data / CERSAT - Le CERSAT
I don't get this:
If the AF 447 had been in nominal cruise speed between 02:10Z and 02:14Z (above mach 0.8 ?), it would have been too far to the north to explain the first body/debris location of June 6 ? (to be found where they were found, they would have to drift toward the west, but in this area, the currents and the swell were oriented toward the N-NE).
Would it suggest that between 02:10Z and 02:14Z, the AF 447 was already in big trouble, loosing rapidly altitude, that it never got out from the mesoscale convective system and crashed just after the last ACAR between the two red points ? (possibly just exiting the MSC system)
Under this hypothesis, the drift between June 1-June 6 (from crash area to first boby/debris) would have been largely smaller in 5 days than the drift between June 6-June 9 in 3 days (then from June 10 and June 15, at W-NW of TASIL in the search area, is oriented toward the NW. The satellite time series show that the current speed increased a bit between 6 and 12 but only to reach 0.12 m/s: it does not explain the different drifts by far): does it suggest that the bodies and debris (recovered between the 6 and 9 of June) were initially dispersed ?
Hope these are not silly/already answered questions.
Jeff
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Old 24th Jun 2009, 16:32
  #2252 (permalink)  
The Analog Kid
 
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Originally Posted by DJ77
See, for example, Tim Vasquez's analysis: no updraft higher than 40kt (about 4000 ft/mn), not "18000 ft/min, even higher" as mentioned, and no heat sink signature observed.
Some of you will be familiar with Ewa Wisnierska being sucked up into a thunderstorm on her paraglider in Australia a couple of years ago:

"Ms Wisnierska's top speed of ascent was clocked at 20 metres per second and her descent at 33 metres per second by an on-board tracking system"

Perhaps by chance she hit the upper limit quoted above. Perhaps it's not the upper limit.

8-10 m/s isn't unheard of even when simply thermalling in the core under a decent cu on a good day in the UK. Only twice that - 20m/s = roughly 4000ft/min - therefore seems pretty low for a supposed upper limit in the ITCZ.
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Old 24th Jun 2009, 16:42
  #2253 (permalink)  
 
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the system ..not F/Os

As I have said a few times I am not critical of the newer F/Os, but more a possible system that has degraded the skills that pilots used to aquire over time.

There is a recent article in the latest FRAeS magazine 'out of the fog ' by a Capt Robert Scott.

I wont reproduce it here, and I do not know if he wrote this after the AF accident but I suspect not as it was the May issue, however it talks in great depth about over-reliance on automation and the complacency and confusion that can exist in cockpits today.

The very thing ie automation, that was supposed to reduce the workload of the pilot and reduce accident rates, has possibly caused the rate to flatten out, as loss of control and other issues appear to occur more.

I have no axe to grind against any pilots, we are 'but a product' of the systems that train us.

Perhaps the training needs to be directed in another way in the newer generation of jets.

That is probably what I am trying to get at.

hope that is clearer? W
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Old 24th Jun 2009, 18:36
  #2254 (permalink)  
 
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woodja51

I tend to agree with you about the pilots being a product of a ''system''.

How many lessons have you had in extreme turbulence flight?

In off airport/forced landings?

In ditching at sea, at night?

How to avoid bird strikes?

I know I've had to seek out the answers to the above on my own time. I learned to fly in 1975....old school by most standards of today.

And its all about money. I've offered to at least one of the 4 airlines I flew for some extra stuff in the training of pilots. NOPE...costs too much and the FAA doesn't require it.

We won't really know what happened with air france...but I know how to make things better...but planes won't carry as many passengers, fuel use will be up, training costs will double.

oh, and the chairs will be more comfortable!
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Old 24th Jun 2009, 19:05
  #2255 (permalink)  
 
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We won't really know what happened with air france...but I know how to make things better...but planes won't carry as many passengers, fuel use will be up, training costs will double.

oh, and the chairs will be more comfortable!
At the end is always a matter of costs....make it safe as much you can within the rules...do not make it safer if is not required by regulation. Even if it is technically achievable.
Make sure to make the C class guys very comfortable on their chairs...
I do not want to start a huge argument, but the fact is that we cannot design full proof systems and we have to accept a failure rate...which in aviation is 10^9...can we design better systems? Yes! The benefits will overcome the costs? As today the answer is no.
FSLF
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Old 24th Jun 2009, 19:13
  #2256 (permalink)  
AMF
 
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DJ77 quote..

AMF

Nice scenario ... for Hollywood.
If you think that's a "Hollywood" scenario, then it tells me you're seriously lacking in knowledge when it comes to high altitude aerodynamics and experience with regards to hand-flying jet aircraft near the upper edge of it's envelope and the danger that lies just outside it, as well as obviously not very familiar with operating in close proximity powerful CBs on a routine basis.

If you're another person who seriously understimates their power, then my hope is that you're not one of those pilots who also do because at some point in their past they flew through some heavy rain at a mid or low altititude rain and it all turned out Ok.

If you think it's a "Hollywood" scenario, point out where I'm wrong in what I posted regarding the aerodynamics or the effects of CBs on aircraft. Aviation accident lists are full of aircraft that went outside the boundaries of the first, or inside the danger zone of the 2nd, sometimes both.
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Old 24th Jun 2009, 19:23
  #2257 (permalink)  
 
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Worried I AM

Been a lurker here for a few years now and no longer sitting up the pointy end i am seriously concerned about what i am reading here.

Never been a V1 Positive Climb Gear Up Autopilot On pilot - and yes i tended to hand fly up to cruising height and on the way down from TOD around 95% of the time and occasionally in the cruise too where there was more to do than fly straight and level for and length of time and yes i have had the CSC (that should give you a hint - along with the lovely Tartan skirts) come on the flight deck to see/ask why things were not as smooth as normal. I am seriously worried about the hands on skills of the people who are flying me about now. Doubly so as i cant now get on the FD. And yes i have been there as a retiree (i know I hat(ed) being back in the cabin) too when the F/O and then the Cpt took rest mid Atlantic on a 747-400 on a LHR to LAX flight. This was after having to abort and return to LHR on the previous day due to C/B's on the main and aux bus tripping. Then while the passengers were put up close to LHR the crew were bussed 60 miles away to get what must have been minimum rest at best - all from your Fave Airline :-I did have a wee shot of i think a 310 and i found that quite strange being used to the other style of fly by wire aircraft. Yes i have sat reading the Guardian and the Telegraph on many a Transatlantic flight and yes we had an open cockpit policy ask and generally FD visits were more than possible for sure they helped to relieve the boredom. My nasty weather experiences have mostly been in FL slaloming round the thunderheads in VFR conditions and we always ADVISED a 20/30 degree course change to avoid weather and never once had a problem from ATC and of course some in Europe too on the Ski flights. I am rambling. It would appear - please dont take this the wrong way - but the skills are gone/going fast from the job now - pilots are increasing 'just' monitoring systems and dont have the skills or the experience to take over when the shit hits the N1. Also it would appear that we are entering a period when the experienced captains are retiring to be replaced by people who jump from a PPL into a ATPL without any real flying skills. Is this fixable i cant see how - maybe others can see a solution. Flying now is a worry to me and when i hear rubbish from the flight deck like "sorry our departure was late but we will make it up as we cross the Atlantic" aye right quickly file a new flight plan with .85 as the new cruising speed and "sorry we did not make up time crossing the Atlantic but we will get a straight in to NY" again utter rubbish - a downwind landing against the existing traffic flow - and when I look out the window and see the air brakes at half cock and after 30 mins they are still like that - then i mention this to the FA and get told its ok sir the Captain knows" and watch her walk down to the aft galley pick up the inter phone and immediately the speed brakes are closed as the SB handle gets latched in the closed position properly- i do wonder where this industry is going.
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Old 24th Jun 2009, 19:34
  #2258 (permalink)  
 
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woodja51: There is a recent article in the latest FRAeS magazine 'out of the fog ' by a Capt Robert Scott.
Is there any online link to this? I keep finding Robert Scott the early 1900's Antarctic explorer instead.

I think you make some very good points, regarding the complexity of modern FCS, and a probable drift of skills more towards computer operator/systems diagnostician than reflexive pilot.

One key question will be whether situation was one that anyone, pilot or computer could have recovered from. It is possible that it was a recoverable upset per some of the other A330 upsets, made worse by weather, information overload, etc.

Another possibility is that the situation was completely beyond anyone's ability to recover from and the similarities to the other A330 upsets is only a component of the issue or coincidence (for example probe icing followed by structural failure).

I will try and find the doc again, but it that really put the loss of computers/automation/instruments into perspective for me, it mentioned that one way if you have conflicting information was to compare air speed to cockpit wind noise. How quickly things can get back to basics, and imagine that mid storm, mid crisis.

If we forgoe the piloting skills we reach the other extreme that is 2001-esqe. "Please save the plane HAL. I'm sorry Dave, I can't do that."

Somewhere in between is the fine balance that gives us the benefits and minimizes the risks.
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Old 24th Jun 2009, 19:35
  #2259 (permalink)  
 
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Statistical failure-rates

@ FrequentSLF:

Accepted catastrophic failure-rates are actually much higher:
The 10E-9 - figure is the failure-rate of _one_ system leading to a catastrophic failure.
Given an error-(failure-)chain, the accepted probability is 10E-6. This accident is most probably in this category.

The source is AMC 25.1309. ("Acceptable means of compliance to Certification Specification 25")
I cite the explanation:
In assessing the acceptability of a design it was recognised that rational probability values would have to be established. Historical evidence indicated that the probability of a serious accident due to operational and airframe-related causes was approximately one per million hours of flight. Furthermore, about 10 percent of the total were attributed to Failure Conditions caused by the aeroplane's systems. It seems reasonable that serious accidents caused by systems should not be allowed a higher probability than this in new aeroplane designs. It is reasonable to expect that the probability of a serious accident from all such Failure Conditions be not greater than one per ten million flight hours or 1 x 10-7 per flight hour for a newly designed aeroplane. The difficulty with this is that it is not possible to say whether the target has been met until all the systems on the aeroplane are collectively analysed numerically. For this reason it was assumed, arbitrarily, that there are about one hundred potential Failure Conditions in an aeroplane, which could be Catastrophic. The target allowable Average Probability per Flight Hour of 1 x 10-7 was thus apportioned equally among these Failure Conditions, resulting in an allocation of not greater than 1 x 10-9 to each. The upper limit for the Average Probability per Flight Hour for Catastrophic Failure Conditions would be 1 x 10-9 , which establishes an approximate probability value for the term "Extremely Improbable". Failure Conditions having less severe effects could be relatively more likely to occur.
Thomas
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Old 24th Jun 2009, 19:39
  #2260 (permalink)  
 
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I do wonder where this industry is going....

Maybe it's contracting.
Boeing and Airbus would never agree, but will the 90% of pax travelling on family trips always be there? When one can see one's granny in Australia large as life (yuk) every day, where's the incentive to fly sardine class for 20+ hrs?
I'm a veteran but I feel a revolution is in the air.
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