AF 447 Thread No. 11

[CONF iture]

Ten lines later it says that the A/THR was disconnected immediately after take off
To disconnect the A/THR is not to inhibit it in the way to prevent Alpha-Floor to trigger.

and twenty one lines later it records that between 50 and 40 ft AGL the CdB confirmed that the A/THR was disengaged.
To disengage the A/THR is not to inhibit it in the way to prevent Alpha-Floor to trigger.

As I understand it, alpha floor is an A/THR dependent function.
Yes, but Alpha-floor could trigger whatever the status of the A/THR ... unless one of the steps to prevent Alpha-Floor to trigger has been applied. It appears that none of these steps were applied.

So you accept that he meant to make the demonstration without alpha floor and the record shows that he took action to inhibit alpha floor
It was his intention, but the record does NOT show such action.

why didn't he fly the demonstration in a manner consistent with his intent and earlier actions?
He was simply too fast to meet the criteria for a voluntary Alpha-Floor inhibition.

[Owain Glyndwr]

@Confiture

Yes, but Alpha-floor could trigger whatever the status of the A/THR ... unless one of the steps to prevent Alpha-Floor to trigger has been applied. It appears that none of these steps were applied.OK, but for my information what would these additional steps have been?

Following on from that, would these steps have been known to the pilot? If they were then why did he not apply them if his intent was to make the demonstration with Alpha -Floor inhibited? If he was unaware that he should take these extra measures then he made the flight believing that he had inhibited it. In which case my question:

- why didn't he fly the demonstration in a manner consistent with his intent and earlier actions? remains valid.

too fastAt 118 kts????

[Chris Scott]

Quote from gums:
Later jets had an auto throttle system ( Hornet), and I am not sure of the implementation. Most Nasal radiators and some of us in the SLUF and Viper flew AoA on approach and cross checked the speed to make sure we had the correct configuration.

"Nasal radiators"? LOL!

So the A-7 Corsair was nicknamed SLUF? We have a civil a/c - very much not FBW - that used to be called FLUF, until they really stretched it and put weird bananas on the wingtips. (Also referred to as the "crab")

OG,

Something about "....where angels fear to tread"...? ;)

[Chris Scott]

Quote (http://www.pprune.org/tech-log/511119-af-447-thread-no-11-a-37.html#post8144119) from vilas:
The change to AOA protection mode disengagement was done through MOI in 2005. With this software change AOA protection is no longer active when alpha is less than alpha prot and side stick has not been deflected since the last autopilot disconnection.

Quote from my response:
Have you quoted the MOI in 2005 verbatim? If so, in an identical repeat of the A340 AIRPROX of 2001, it would have prevented the engagement of AoA mode (referred to by the AAIB as AoA protection Law). Taken literally, that would represent a radical inhibition of engagement, not an additional means of disengagement.
If, on the other hand, "is no longer active" actually means "will disengage", it would be an additional means (condition, or criterion) for disengagement. But it would not apply if either sidestick had been moved during a period of hand flying. That would seem odd, but perhaps I'm overlooking something.

Reply from vilas:
...I have quoted the MOI verbatim.

Thanks, vilas. Like OwainG, I am not familiar with (or have forgotten!) the term "MOI", but I presume it's a publication for informing operators of technical mods?

In my response, I overlooked a second possible inference that might be made from the MOI. I refer to this mid-sentence phrase:
"...AOA protection is no longer active when alpha is less than alpha prot ..."

Does it mean that, by 2005 (about 4 years after the A340 AIRPROX), AI had discontinued the phase-advanced engagement of AoA mode ("AoA protection Law") cited in the AAIB Bulletin of 2001? Page 11:

"Ten seconds after the autopilot disengaged, the corrected or phase-advanced angle of attack (a computed parameter which is is not recorded but can be calculated by [AI] from the DFDR data) reached the 'alpha prot' value. This [AoA] excursion beyond alpha prot caused a change in the pitch flight control law from normal law (Nz law) to angle of attack protection law (AoA law). If both sidesticks are at neutral, the AoA protection law seeks to hold the [AoA] constant at alpha prot until a sidestick pitch command is made."


Quote from HN39 (my emphasis):
My understanding is that activation/deactivation of any protection is recorded by the DFDR by a dedicated discrete parameter changing from OFF to ON, from ZERO to ONE, or whatever, and vice versa. I think it would have been a very strange omission if overspeed protection had been activated and caused the pitch-up and the AAIB report had made no mention of that fact.

Thanks for making that point.

[DozyWannabe]

@OG - the only person claiming that the (permanent) disconnect didn't happen is one Christian Roger - SNPL member, card carrying member of the "cover-up" conspiracist crew, and member of Asseline's legal team.

It would appear that CONF iture is quoting assertions from this man's report as though they are fact.

However - this of course has nothing to do with the subject at hand, so moving swiftly on...

[vilas]

Chris&OG
Modification operational Impact

[gums]

Yeah Chris and others, the A-7 was truly called Sluf for Short Little Ugly "Feller". And staying off-topic a bit, we pilots in the first F-16 unit voted on "Viper". USAF didn't want a jet named after a reptile, so it became "Fighting Falcon" ( a civilian jet already had taken "Falcon").

The Sluf stick had a grip which contained force tranducers, and they used one for the prototype Viper FBW system with extra transducers. What they did was provide "augmented" commands to the control surfaces, and on check flights I could hold the stick between my knees and command roll and pitch by twisting the grip. So we were well on our way to FBW bacg in the late 60's. Pretty sure the Hornet has similar implementation, although their stick moves like the 'bus.

As Doze has iterated, pure "force feedback" has been absent for many years except a few implentations that use cables or pushrods for a limited number of surfaces. So anyone wishing for the "old days" are SOL. Only the Phantom and VooDoo had a pnematic bellows that kept you from pulling too hard at ridiculous high Q that the heavies cannot imagine, heh heh. Otherwise it was springs and things resembling shock absorbers to slow down rates and keep us from ripping the wings off.

I am still shocked that the AoA limits on the 'bus aren't active as long as the sensors are deemed reliable. So I learn a lotta stuff much of my time here.

Secondly, the overspeed "protection" features seem excessive, but the critical mach seems to be the "driver". I have also learned here just how close to edge of the envelope the thing flies. Surprised me, as we cruised well below our critical mach in the sub-sonic A-7 and A-37.

[Owain Glyndwr]

Something about "....where angels fear to tread"...? ;)

Eyes wide shut - but not foolishly I hope ;)

[Owain Glyndwr]

@vilas
Modification operational Impact
Thank you, but a little more detail would be helpful since I cannot trace anything on the 'net'
Do you have a URL where the whole article can be read? Who is the MOI published by?
Airbus? or is it an unofficial document of some sort?

[Winnerhofer]

1.12.4.2.1 3 Flightdeck Seats

On the RH-seat, there were no seatbelts fastened whatsover.

The most plausible scenario:
When Dubois asked Bonin if he had a licence -"T'as le PL, toi?" - just before he exited the flightdeck, Robert was already sitting on the LH-seat.
The hashed - censored DCVR- omits the fact that all 3 were discussing the answer of the licence and the only word that officially was allowed to come out was Dubois' reply of "Bon".
What followed before "Bon" and shortly after "Bon" is censored.
Bonin was napping when the A/P cut-off and in the ensuing alarms, panicked and accidentally used the S/S to pull himself out of his reclined position.
This caused the violent NU.
The following 3 minutes, absorbed by panic and impending tragedy, he didn't have time to adjust his seat or to stick one of his belts on.
Dubois wasn't seated on the jumpseat but someone else, most probably Mme Bonin.
This could further explain why Bonin refused to relinquish his grip on the S/S as matter of pride.
Dubois was seated with PAX when he felt the NU and swaying.
He didn't hear the buzzer because he wasn't in the CRA.
What were his first words as entered the flightdeck?
Not "what's up guys?" but "what the hell are you doing!"

[A33Zab]

vilas is correct.

The documents entitled Modification Operational Impacts (MOI) are provided for information only.
MOIs are issued to inform operators, particularly operators'
flight operations and training departments, about the impact the referenced modification and/or Service Bulletin (SB) has on the operation of the aircraft as described in the flight operations documents mentioned in the MOI.
The MOIs particularly describe the impact a modification or a SB has on the FCOM.
Unless specifically listed in the MOI, other flight operations manuals may be affected without indication in the MOI.

MOIs provide a generic and non-customized technical description of the modification/SB, and briefly describe the associated operational impact.
Operators can use MOIs as support material to decide whether to apply the SBs to their fleet.
Operators can also use the MOIs as advance operational information in anticipation of an SB retrofit.
In all cases, the MOIs are to be used for information only, and the contractual flight operations manuals remain the support documentation of reference for flight crews.

[Owain Glyndwr]

@A33Zab
MOIs provide a generic and non-customized technical description of the modification/SB, and briefly describe the associated operational impact.
Operators can use MOIs as support material to decide whether to apply the SBs to their fleet.
Operators can also use the MOIs as advance operational information in anticipation of an SB retrofit.
In all cases, the MOIs are to be used for information only, and the contractual flight operations manuals remain the support documentation of reference for flight crews.

Thank you A33Zab, that is very helpful and new to me.

Presumably, since the MOI is advanced operational information there will be an official accompanying SB and an FCOM change if and when the modification is fitted? Does anyone know of such a change so we can study it in more detail?

[DonH]

Thank you A33Zab. Finally we have something to chew on!

As O.G. has respectfully asked vilas, is there a source? To me, this reads like an individual Operator's term and not something from Airbus.
A key statement is, "In all cases, the MOIs are to be used for information only, and the contractual flight operations manuals remain the support documentation of reference for flight crews."

I'd flown Airbus from 1992 on, for fifteen years and had never heard of the term. I know of ATB's, (Aircraft Technical Bulletins), SB's, (Service Bulletins), OEB's (Operational Engineering Bulletins, which are issued for immediate action due safety relevance), and those more closely associated with the regulator such as SAFO's, (FAA), AD's, (regulator/manufacturer) and so on. Encountered here and then not defined for others, the term "MOI" remained a mystery.

By the description, I understand that an "MOI" is for flight crew information only and as such is advisory, where (as described) a non-technical description of the more formal SB may be desired for quick distribution. Of course, it is understandable that each carrier may have its own informal distribution network where terms may differ between Operators where they are not part of the continuing airworthiness process.

As such, I doubt if an MOI would be proprietary in the same way an Operator's AOM may be so it would be of interest to have at least a hint of what the actual document stated.

[vilas]

donH
MOI is Airbus term for any modification carried out by them. Published for the operator.

[DonH]

Thank you vilas, much appreciated! As you see, I haven't run across the term in all my Airbus travels. There will be many Airbus terms published/not published by individual operators which do not have continuing airworthiness import but are for aircrew information. This one, I had not ever seen in our own operation. That resolved, is it possible to reproduce, as much as may be possible/desireable, some of the "MOI"?

[Owain Glyndwr]

@vilas
MOI is Airbus term for any modification carried out by them. Published for the operator.

So is there a formal AI mod and an associated FCOM change?

[vilas]

OG
Yes, that is correct.

[Owain Glyndwr]

vilas
Yes, that is correct.

So may we know what it is please?

[mm43]

You said the chicken died a horrible death!

"That is correct, Sir!"

Then please describe the injuries inflicted.

"It's all in the MOI, Sir"

Who's death? The chicken or - :ugh:

[chrisN]

Winnerhofer you surmised that “Bonin was napping when the A/P cut-off and in the ensuing alarms, panicked and accidentally used the S/S to pull himself out of his reclined position.
This caused the violent NU.”

This is not consistent with Bonin’s first stick actions, discussed at length on previous threads. IIRC, first he countered uncommanded roll by vigorous side movements and accompanying (I believe unintended) minor pitch variations in both directions but on average slightly nose up (the famous “stirring mayonnaise”).

Only after getting the roll under control did he initiate major nose-up movements, and even then not entirely consistently.

It has been done to death before.

[CONF iture]

the only person claiming that the (permanent) disconnect didn't happen is one Christian Roger - SNPL member, card carrying member of the "cover-up" conspiracist crew, and member of Asseline's legal team.
It would appear that CONF iture is quoting assertions from this man's report as though they are fact.
Time after time you demonstrate how little you know about the Report, the Official one, but keep pretending quoting stuff that is simply NOT in it.
Move swiftly out at your own pace ...

Following on from that, would these steps have been known to the pilot? If they were then why did he not apply them if his intent was to make the demonstration with Alpha -Floor inhibited? If he was unaware that he should take these extra measures then he made the flight believing that he had inhibited it.
Those are not extra measures, they're only different. As per CVR the pilot did not elect to permanently inhibit Alpha-Floor, but only temporarily by inhibition upon activation. Doing so is only possible if AoA has already reached 15 degrees, but at the time TOGA was manually applied by the pilot, the AoA had not yet reached such angle.
Too fast he was.

[Owain Glyndwr]

Confiture
Those are not extra measures, they're only different. As per CVR the pilot did not elect to permanently inhibit Alpha-Floor, but only temporarily by inhibition upon activation. Doing so is only possible if AoA has already reached 15 degrees, but at the time TOGA was manually applied by the pilot, the AoA had not yet reached such angle.
Too fast he was. OK, so in your view he intended to cancel any thrust increase from Alpha-Floor if it triggered but this intention was overtaken by events when he applied TOGA thrust too early (for Alpha-Floor to trigger that is).
This would seem to make any consideration of the part that Alpha-Floor might play in this affair totally irrelevant.
That take us back to the conclusion that he intended to make this demonstration in manual flight, taking on his own shoulders the responsibility for energy management and relying entirely on his own experience, skill and judgement.

[Clandestino]

@Chris - I think we do know that Alpha Floor was not a consideration for the pilot of AF296, as he *disabled* A/THR (and thus A. Floor) by holding down the disconnect switches to perform the flypast.

Actually, problem is mistranslation of section 2.2.3.2. - it deals with what was planned and disabling of the alpha floor certainly was but it was never executed - chalk one up for sloppy execution. Section 2.3 clearly states Alpha floor was disabled as the result of RA going below 100. Now if anyone thinks exact mechanism of disabling alpha floor is of concern in the accident where narrowbody full of passengers was deliberately flown below 100ft at 120 kt and idle thrust - feel free to entertain me further.

On the RH-seat, there were no seatbelts fastened whatsover.Corrected in the final report; after further analysis lap and crotch strap were found to be fastened.

By the description, I understand that an "MOI" is for flight crew information only and as such is advisoryIt is advisory only but it's for operator information and it is up to operator to determine what info (if any) from MOI will be distributed to flightcrews and means of promulgation.

[CONF iture]

This would seem to make any consideration of the part that Alpha-Floor might play in this affair totally irrelevant.
Never said it was either.
I was simply pointing out the misinformed comment made by Dozy, which shows how Habsheim, the Report, or the airplane, are still nebulous.
Any Airbus incident accident report contributes (or not ...) to develop the knowledge on that machine. Habsheim is no exception.

[Chris Scott]

ventus 45,

Thanks for that.

Judging from the example in the link you provided, an MOI is pretty much at the opposite end of the spectrum from an OEB (Operational Engineering Bulletin), in that it seems to be a broad-brush, glossy document prepared weeks or months in advance to hand out at a flight-ops symposium (in this case by a senior AI pilot to CAAC flight ops people at a "workshop" [sic!] in Beijing).

Also, the document is nowhere appended with the MOI term, merely with "...confidential and proprietary document". Can you explain the basis on which you selected it as an example?

[A33Zab]

A340 (MOI dated 04 AUG 2005 FCOM rev. 20) and A330 (MOI dated 18 NOV 2004 FCOM rev. 16) makes reference to the AP disconnect.

A330 (MOI dated 01 FEB 2006 FCOM rev. 19) makes reference to the "sidestick neutral or forward for 0.5s while AoA<AoAprot"

an identical MOI for A340 is not listed.

Several SBs are involved since subtypes have their own SB number.

For A340-2/3xx SB 27-4131 may be involved since this SB mentions "an improvement in AoA phase out logic" without specifying the improvement in detail.

[Owain Glyndwr]

Thanks A33Zab

[Chris Scott]

ventus 45,
Thanks again - I simply hadn't got to Page 22. Still wondering if that glossy document is itself an MOI, or repeating information previously promulgated in a specific document called MOI.

A33Zab,
Seems the plot is still thickening on these matters...

Quote from Clandestino:
"Now if anyone thinks exact mechanism of disabling alpha floor is of concern in the accident where narrowbody full of passengers was deliberately flown below 100ft at 120 kt and idle thrust - feel free to entertain me further."

Very much associate myself with that sentiment, My base training at Blagnac with AI in March 1988 - around the same time as the Habsheim crew - naturally included that part of the flight envelope. The differences from Habsheim included: safe altitude, no rushed manoeuvering and energy disposal to botch, and NO PASSENGERS. Seeing the Habsheim video a few months later suspended belief, but suggested the protections had worked well.

It is human nature, however, to want to understand the detail of the main factors in any departure.

[llagonne66]

Chris,

The document is a presentation made to CAAC, illustrated with an image taken out of a MOI.
MOIs respect the general "look and feel" of Airbus' Flight Ops documents.

[CONF iture]

Seeing the Habsheim video a few months later suspended belief, but suggested the protections had worked well.
But the FDR data show that the System had no intention to deliver Alpha Max ...

[aircrashesandmiracle]

Quote from Clandestino:
"Now if anyone thinks exact mechanism of disabling alpha floor is of concern in the accident where narrowbody full of passengers was deliberately flown below 100ft at 120 kt and idle thrust - feel free to entertain me further."

To which Chris Scott commented:
Very much associate myself with that sentiment, My base training at Blagnac with AI in March 1988 - around the same time as the Habsheim crew - naturally included that part of the flight envelope. The differences from Habsheim included: safe altitude, no rushed manoeuvering and energy disposal to botch, and NO PASSENGERS. Seeing the Habsheim video a few months later suspended belief, but suggested the protections had worked well.

As shown in my piece on the subject NEW A320 CRASHES AT AIR SHOW (HABSHEIM 1988) (http://chrisbart.com/?page_id=239) in Air Crashes and Miracle Landings the situation was worse than "less under 100 ft" would suggest as the trees in front of them were 40 ft high. It points out that although the captain had performed the "stunt" many times it would have been in the safe conditions mentioned by Chris Scott.
Though the engines did spool up from idle (though not in time), the manufacturer did take measures to improve their reaction time following the disaster. In view of the many other negatives, that improvement might not have been enough, but worth bearing in mind.

[Chris Scott]

Quote from llagonne66:
The document is a presentation made to CAAC, illustrated with an image taken out of a MOI.
MOIs respect the general "look and feel" of Airbus' Flight Ops documents.

Thanks for confirming that an MOI is not a glossy brochure! "No 35811" suggests they may appear at a rate of more than one a day?

If anyone can provide access to a sample, I think several of us here would appreciate it.

[DozyWannabe]

But the FDR data show that the System had no intention to deliver Alpha Max ...

*sigh* - If we clear this up now, can we get back on topic?

Right CONF - we know, as you repeatedly point out, that the system's Alpha Prot computations allow for an AoA just (probably just a fraction of a degree) shy of true Alpha Max. This is probably to provide a little extra safety margin - after all we are talking about the boundary of stall here. Your contention is that if the protection wasn't there, Capt. Asseline had the skill to finesse that extra fraction of a degree and cleared the trees. Am I correct so far?

So - let's look at some other evidence. Leaving aside the rather dubious notion of performing that maneouvre with passengers aboard in the first place (for which AF should be - and were - censured) - Capt. Asseline elected, having found himself off course (expecting the paved runway), fast and high, to fudge the approach rather than turn around and try again. This rather correlates some of the anecdotal evidence we have of the guy being somewhat arrogant. The mistranslation I've been working from regarding disabling of A/THR (and thus A. Floor) means that while fudging that approach, Capt. Asseline forgot to follow the protocol and did not cross-check with the crew. This arguably makes him both arrogant and incompetent - and it also demonstrates that his handling skills were not particularly well-developed. He then allowed the engines to spool down, and the aircraft to drop below 100ft - leaving an aircraft that was carrying passengers low, slow and out of options. Arrogant, incompetent *and* careless - qualities reflected in the judicial decisions that went against him.

Arrogant, incompetent and careless pilots have a nasty habit of getting people hurt and killed - and there is no mitigating excuse in the world that can counter the *facts* described in the paragraph above.

There - Habsheim is now discussed for the umpteenth time on a thread that bears little relation to the subject at hand. Permission to move along?

[Winnerhofer]

http://www.flightglobal.com/blogs/learmount/assets_c/2013/03/Pre-flight%20checks-thumb-500x156-174893.jpg

[CONF iture]

Right CONF - we know, as you repeatedly point out, that the system's Alpha Prot computations allow for an AoA just (probably just a fraction of a degree) shy of true Alpha Max.
2.5 deg is NOT a 'fraction of a degree'.

This is probably to provide a little extra safety margin - after all we are talking about the boundary of stall here.
The 'little extra safety margin' is already in Alpha Max, that is why Alpha Max is Alpha Max and not Alpha Stall.

Your contention is that if the protection wasn't there, Capt. Asseline had the skill to finesse that extra fraction of a degree and cleared the trees. Am I correct so far?
You are NOT.
The contention is that such supplementary restriction is NOT mentioned in the FCOM and not even in the BEA Report that had the duty to list it at a contributory factor.

Arrogant, incompetent and careless pilots have a nasty habit of getting people hurt and killed - and there is no mitigating excuse in the world that can counter the *facts* described in the paragraph above.
You can even call him criminal if you wish but not before ALL facts are put on the table.

*sigh* - If we clear this up now, can we get back on topic?
As you obviously don't know the Report, it would be hard to 'clear anything up'.
You don't have to stick around either ...

[DozyWannabe]

CONF - he wouldn't have cleared the trees anyway, and even if he had, he'd still probably have ended up losing his licence on the basis of the video evidence.

Where do you get 2.5 degrees from?

[CONF iture]

CONF - he wouldn't have cleared the trees anyway
You certainly do not have the knowledge to state so.
The BEA had the necessary tools to get some numbers.

and even if he had, he'd still probably have ended up losing his licence
Who cares ?
I'm not reading Paris Match here, I am interested in the technical side.

Where do you get 2.5 degrees from?
*sigh* - From the documentation you don't read but still think entitled to make statements on ...

[Clandestino]

Please explain why you dismiss, for the 15th time at least, a vertical descent rate of 10,000 ft per minute (about 100 kts) does not qualify as a valid speed for angle of attack vanes.1. no swiveling pitot probes generally and on 330 in particular 2. trigonometry.

The 'bus and my little jet 40 years ago used, and still uses, the "q" for "gains", which limits the rate of control surface movement accordingly.Well, that's the beauty in simplicity of the Airbus FCS: it doesn't need q. Pilot inputs G demand, elevator moves to meet it (as measured by IRS) and that's all there is to it. No need for taking q from ADC or elevator pitots to adjust stick stiffness, there is just non-adjustable spring. You might have all air data shot up and still have G command and protection - that's what is meant by obscure (to some) term "Alternate law". Of course, simpler means cheaper but also means there are far less components to break down.

Much ado has been made around here about complexity of reconfiguration laws and how to enter and exit protections. Operationally, all conditions listed in FCOM are of not much significance. What to do if your controls have gone alternate in flight? Nothing, keep on flying as you were. Just don't perform windshear or GPWS escape with full stick back, keep an eye on the airspeed, OK? How much stick and for how long is needed to combat the unwarranted alpha prot pitching you up? Who cares, push the stick to get the attitude you need and prot disconnection will take care of itself, it is meant to be instinctive and it is.

In your eagerness to respond in a single post to several pages and many contributors, you have a tendency to select snippets of text out of context, and comment rather dismissively on them. In doing so, you misrepresent the contributor's argument. (I'm wondering if you suffer from a short attention-span - not unusual in hot-headed youth...)I'm sorry Chris, if my caustic style caused you to believe I was going for a cheap shot here. To make my position clear: I do not find any of the theories that there was anything remotely rational in CM2's action and it was just misunderstanding and misapplication on his part plausible. He meant just to return to altitude? He busted it by a couple of thousand feet. He followed the flight directors? He pulled whether they were there or not. He was cognitively overloaded? For a while the only thing picked up by the CVR is stall warning. The aeroplane developed roll oscillation? Oh sure: maximum amplitude 11°, period approximately 10 seconds, damped actively and completely in 1:30 min. He tried to perform UAS procedure for very low level in cruise? He didn't say so and was persuaded by CM1 to ease a bit anyway but stall warning sent him into another pull-up frenzy.

Now let's have a look at the general state of the aviation safety; despite all the doom-sayers that overuse of automation is going to be the end of us all, year after year we are enjoying the record lows of accident rates, so we must be at least doing something right. Of course, not all or even the most of improvement in the safety record is attributable to automation but there is no evidence it reduced safety, especially if besides the dry statistics we choose to pay attention to all too numerous incidents where automation went ballistic and pilots saved the day, often without anyone noticing except their colleagues informed via internal safety bulletins. So if we (and I mean we as aviation community, not as PPRuNers) want to improve the chances of everyone landing safely by applying the lessons of AF447, we better make sure we understand what really happened, lest we apply the cures that are inappropriate and can turn out to be poisonous.

I do not know what made the whole crew to act as they did but I am pretty sure there are two things that won't prevent AF447-like accident from reoccurring: more raw data manual approaches and more practice in unusual attitudes recovery. Practicing any of them involve preparation and anticipation, things sadly lacking in AF447 case where onset of the trouble was very fast. Again: issue with AF447 is not the pilot unable to handfly the aeroplane; it was pilot unable to understand the situation, implication of his actions and pretty precisely handflying just the wrong way, while his assisting pilot was, unfortunately, as lost as him. Nothing of it can be prevented by practicing eye-to-hand coordination in friendly skies. Also this kind of reaction is very rare and trying to present AF447 as typical of the current state of affairs is misinformed at the best.

I have mentioned that this is just another child-of-the-magenta case and this might be too imprecise; despite significant differences (performance and aerodynamics vs. lateral navigation) both AF447 and AA965 are subsets of the same archetype of accidents: pilots who find themselves on unfamiliar territory, are unable to recognize where they are and how to return to normal, eventually performing the action that results in their premature termination. That is absolutely not to say they were bad pilots: I'm pretty sure if they were presented with the scenario of their final flight, they would vehemently deny they would ever act according to it. As many around here very well know, difference between thought process in the air and on the ground is stupendous, especially at 4AM. Our unfortunate colleagues were suddenly thrown on scales and found lacking and even after final report we are not much smarter regarding what was missing.

[DozyWannabe]

You certainly do not have the knowledge to state so.
The BEA had the necessary tools to get some numbers.

To what end? He wasn't censured for failing to clear the trees, he was censured for taking unnecessary risks by improperly conducting an approach, then making a pig's ear of the approach itself - putting him (and his passengers and crew) low and slow with absolutely no safety margin whatsoever.

Who cares ?
I'm not reading Paris Match here, I am interested in the technical side.

Then your criticisms of the BEA are unwarranted. They are tasked with providing a technical explanation of what happens in an accident and hopefully formulating recommendations to prevent a recurrence of that accident - nothing more.

What you're demanding - either computations or practical demonstrations to show at what pitch angle the aircraft could have cleared the trees with the airspeed at that point, or indeed if the extra 2.5 degrees (by your reckoning) could have made any difference - does not fall within that remit.


*sigh* - From the documentation you don't read but still think entitled to make statements on ...

I do have the manuals and FCOM kicking around somewhere, and I'm as interested in the technical side as you are - a reference would be handy.

[rudderrudderrat]

Originally Posted by Clandestino
1. no swiveling pitot probes generally and on 330 in particular 2. trigonometry. The pitots don't measure the angle of attack!
Itr's the AoA vanes which swivel.

[BOAC]

rrrat - I eventually found the thread trail (25 Oct) you refer to! I think Clandestino will recognise his error in the light of day and realise he has been confused by the IAS inhibition on the stall warning. Indeed, 100kts TAS is well enough to register an AoA on a balanced probe (I assume they are balanced?), even allowing for density, I would reckon.

[rudderrudderrat]

Hi BOAC,
I think Clandestino will recognise his error in the light of day
Unfortunately, I don't think so as this is his 16th attempt (according to his count.)
It will just be another page of copy and paste of random parts of incomplete quotes.

[Winnerhofer]

@ Clandestino
Again: issue with AF447 is not the pilot unable to handfly the aeroplane; it was pilot unable to understand the situation, implication of his actions and pretty precisely handflying just the wrong way, while his assisting pilot was, unfortunately, as lost as him.

This is exactly the problem with AF's training whose safety record speaks unenviable volumes.
The problem is that AF haven't undertaken the recommendations of the ISRT because of the entire way that AF is run by having overpaid and underworked Generals with no Corporals.
This is reflected by the numerous incidents post-AF447 which indicates that safety culture doesn't run in AF veins.
Now here comes the rub: since 2012, AF has hired A342 instructors from the Estérel squadron at Airbus' behest to retrain AF instructors but so far in vain.
Worse, AF's parlous finances makes it even harder to get on with safety.
I expect DL or SU to leave SkyTeam.
Now watch this space: SU to join SkyTeam...yep Putin's heart pounds for Merkel.

[Chris Scott]

Quote from BOAC (my emphasis):
rrrat - I eventually found the thread trail (25 Oct) you refer to! I think Clandestino will recognise his error in the light of day and realise he has been confused by the IAS inhibition on the stall warning. Indeed, 100kts TAS is well enough to register an AoA on a balanced probe (I assume they are balanced?), even allowing for density, I would reckon.

I'm hoping to find time to answer the rest of his post later (got a car to wash), but I respectfully suggest that you two may be missing Clandestino's point here.

His key word is "trigonometry". Think about it. Compare the pitch attitude of the aircraft, and therefore the pitots, with its steeply-downward trajectory. Haven't got time to check the figures right now, but, although the vertical component of its trajectory is (say) 10,800ft/min (180ft/s, or just over 100kts TAS), the pitot tube is at more than 90 degrees to that.

That's why - I think - he made a cryptic, light-hearted reference to "no swivelling pitots... on 330" (i.e., they DON'T SWIVEL...)

Hope this helps.

[vilas]

Chris, OG, HN39DonH
I can see the discussion has changed track. However I am producing the MOI for your information.
MODIFICATION OPERATIONAL IMPACT (M.O.I)
Aircraft Type
A340
SB Number
27-4101, 27-4116, 27-4131
Modification Number 48753
Modification Title
FLIGHT CONTROLS - FCPC - INTRODUCE NEW L16 SOFTWARE STD ON FCPC HARDWARE 2K0
Issue Date 04-AUG-2005
This information was initially introduced by:
Doc
Volume 1
Volume 2
Volume 3
Volume 4
QRH
FCOM
REV20
OEB
TR
FCOM sections impacted:
Volume 1, Volume 2, Volume 3,Volume 4
QRH. FCOM
1.27.20
OEBs or TRs cancelled by this modification:
Doc
Volume 1, Volume 2, Volume 3, Volume 4, QRH
OEB
TR
Summary of Operational Changes:
This modification consists of introducing the new L16 Software Standard on the Flight Control Primary Computer (FCPC) hardware 2K0. This software introduces a new condition that enables the aircraft to leave the Angle-of-Attack protection.
STLS (FS/EGM) MOI: 48753 (A340) Page 1 of 2
AIRBUS
1 ROND-POINT MAURICE BELLONTE
31707 BLAGNAC CEDEX FRANCE
TELEPHONE 05 61 93 33 33
TELEX AIRBU 530526 F
Modification Operational Impact
STLS (FS/EGM) MOI: 48753 (A340) Page 2 of 2
Description of Operational Changes:
In-flight experience has indicated that strong gusts of wind could unduly activate the Angle-of-Attack (AOA) protection. Therefore, this new FCPC logic is implemented to easily enable the aircraft to leave the AOA protection, when this protection is unduly activated.
With this new standard, the AOA protection is no longer active , when alpha is less than alpha prot, and the sidestick has not been deflected since the last autopilot disconnection.

[CONF iture]

To what end? He wasn't censured for failing to clear the trees, he was censured for taking unnecessary risks by improperly conducting an approach, then making a pig's ear of the approach itself - putting him (and his passengers and crew) low and slow with absolutely no safety margin whatsoever.

Technical side is my concern, not Asseline, will you ever get it ?

Then your criticisms of the BEA are unwarranted. They are tasked with providing a technical explanation of what happens in an accident ...
Ok then where's the technical explanation on why the System refused to deliver Alpha Max ... ?

I do have the manuals and FCOM kicking around somewhere, and I'm as interested in the technical side as you are
If you were you would read the Report first before spreading disinformation.

[RetiredF4]

A330 AOA Vanes (http://msquair.files.wordpress.com/2010/03/aoa-rs-probes-a330.png)Chris Scott
His key word is "trigonometry". Think about it. Compare the pitch attitude of the aircraft, and therefore the pitots, with its steeply-downward trajectory. Haven't got time to check the figures right now, but, although the vertical component of its trajectory is (say) 10,800ft/min (180ft/s, or just over 100kts TAS), the pitot tube is at more than 90 degrees to that.

What's the point there? In the worst case The AOA vane would be stuck at the maximum AOA (design value). Who cares if that is 30 or 60 degrees, it would be stalled anyway. That is at least true as long as the jet is not stalled inverted.
Or do we have any evidence, that the vane would reverse its travel against the airflow?

If the trigonometry concern is for the pitots, then it may be again fair to ask, why besides the AoA a speed indication is needed to determin wether you are in a full stall.

[rudderrudderrat]

Hi Chris Scott,
although the vertical component of its trajectory is (say) 10,800ft/min (180ft/s, or just over 100kts TAS), the pitot tube is at more than 90 degrees to that.
I completely agree. So why would you want to turn off the stall warning when stalled like that?
The 60 kt logic is to prevent false warnings on the ground when the AoA vanes could take up any random position at low speed. Why keep the 60 kt logic when airborne?

[HazelNuts39]

Why keep the 60 kt logic when airborne?To meet a certain vane angle accuracy requirement, I guess.

At FL410, ISA - 35C, for example.

[rudderrudderrat]

To meet a certain vane angle accuracy requirement, I guess.
At FL410, ISA - 35C, for example.
Thanks for that HazelNuts39.
I didn't know that an A330 was capable of flying with an IAS <60 kts.

[HazelNuts39]

I didn't know that an A330 was capable of flying with an IAS <60 kts.At less than 1 g, sure it can do that. Without stalling too.

The point is that the manufacturer of an AoA sensor can guarantee a certain accuracy only within a certain envelope. Outside that envelope any value derived from the sensor must be considered inaccurate and unreliable.

[rudderrudderrat]

At less than 1 g, sure it can do that. Without stalling too.
How long can you maintain FL 410 at less than 1 g?
Outside that envelope any value derived from the sensor must be considered inaccurate and unreliable.
Even though the speed sensor is in error?
Brilliant logic! Best not tell the crew they are stalled then.

[HazelNuts39]

Even though the speed sensor is in error?
You need a bit of hindsight to know that.
Best not tell the crew they are stalled then.There were much more powerful indicators to tell the crew they were stalled. They were all ignored, just as the stall warning itself.

[RetiredF4]

HazelnutsThere were much more powerful indicators to tell the crew they were stalled. They were all ignored, just as the stall warning itself.

Hold the horses!
At the moment we are discussing the inconsistency of the stall warning, right?
Due to an airspeed, which was inconsistent in itself?
And therefore rendered an available AOA indication as unreliable?
And therefore caused the aural stall alert system to tell the crew "end of stall"?

And you think, that is a logic system in itself and not worth improving?

[HazelNuts39]

Due to an airspeed, which was inconsistent in itself?Was it inconsistent?

And you think, that is a logic system in itself and not worth improving?When did I say that?

[RetiredF4]

Quote:
Due to an airspeed, which was inconsistent in itself?
Was it inconsistent?

First due to icing, later due to the high AoA


Quote:
And you think, that is a logic system in itself and not worth improving?
When did I say that?

I'm sorry if i misread your posts, but yes, you sound like you do.

[HazelNuts39]

Years ago I proposed that, if the AoA signal is lost while stall warning is active, the stall warning should continue until a valid AoA signal indicates that the AoA is less than the stall warning threshold.

However, one needs to be very careful avoid that the cure is worse than the disease. The whole issue is somewhat trivial compared to the need to avoid getting to an AoA of 42,5 degrees in the first place.

[BOAC]

until a valid AoA signal indicates - to the best of my knowledge, 447 never 'lost' a valid AoA signal?the need to avoid getting to an AoA of 42,5 degrees in the first place. - agreed.The whole issue is somewhat trivial - no - the lack of stall warning when the Captain arrived in the cockpit was non-'trivial'.

[HazelNuts39]

to the best of my knowledge, 447 never 'lost' a valid AoA signal?The ADIRU determines the vane angle from the sensor 'resolver' values. Possibly it applies a calibration of vane angle vs body angle of attack for the flap/slat configuration. If the airspeed is less than 60 kt CAS, the ADIRU transmits the value NCD (No Computed Data) instead of the AoA value (as I understand it). The stall warning function resides in the FMEGC which uses the AoA values it receives from the ADIRU's.

The stall warning was lost after the captain arrived in the cockpit.

[BOAC]

Probably. That sounds suitably over-complicated.

So it never 'lost' a valid AoA SIGNAL as far as we know.

[HazelNuts39]

That sounds suitably over-complicated.Perhaps some PPRuNers tend to over-simplify?

So it never 'lost' a valid AoA SIGNAL as far as we know.If you insist on having the last word, I'll leave it at that.

[RetiredF4]

Hazelnuts39
The ADIRU determines the vane angle from the sensor 'resolver' values. Possibly it applies a calibration of vane angle vs body angle of attack for the flap/slat configuration. If the airspeed is less than 60 kt CAS, the ADIRU transmits the value NCD (No Computed Data) instead of the AoA value (as I understand it). The stall warning function resides in the FMEGC which uses the AoA values it receives from the ADIRU's.

HN, the logic and function of the stallwarning is understood. The question after AF447 is, wether this arrangement to use the speed signal as the only authority to verify the correctnes of an AOA over the total AOA regime is a clever one. I can understand that some input like speeds are necessary to compute the exact angle of attack. But what sense does that make in extreme AOA conditions, where high raw AOA data show the jet in the stalled condition anyway? Why not implement a logic, where an AOA value above the highest stall onset AOA bypasses the above logic and thus keeps the stall warning active? it cant be rocket science to do that.

To clarify my thoughts a simple example out of daily life. I'm wearing glasses like many people do. When i enter a moist room coming from the cold outside the glasses fog up. Instead of closing my eyes and being blind it has itself proved appropriate to remove the fogged up glasses and work with whatever eyesight is left.

[HazelNuts39]

Why not implement a logic, where an AOA value above the highest stall onset AOA bypasses the above logic and thus keeps the stall warning active? I'm not a systems expert and have to leave the reply to your question to them. Considering what modifications are necessary to implement the BUSS, it sounds to me like a major redesign of the the whole system.

[HazelNuts39]

ventus45,

even simpler would be providing an AoA indicator that shows a flag when AoA=NCD.

[CONF iture]

The stall warning was lost after the captain arrived in the cockpit.
How long after exactly ?

[OK465]

even simpler would be providing an AoA indicator....

....*sigh*

[A33Zab]

even simpler would be providing an AoA indicator....


AoA indicator was(is?) optional, what are the arguments to NOT opt for the AoA indicator?

@HN39:
Not to be picky but stall warning resides in FWC (Flight Warning Computer) not in FMGEC.

[DozyWannabe]

Ok then where's the technical explanation on why the System refused to deliver Alpha Max ... ?

Because to the best of my knowledge nothing in the documentation ever implied that Alpha Prot, or even Alpha Max, were the equivalent of Critical AoA.

If you were you would read the Report first before spreading disinformation.

I'm not "spreading disinformation", and I challenge you to prove anything I've said recently to be wrong. I have not yet been able to source an English language version of the final report, and thus have to work from extracts.

[jcjeant]

This is the final report BEA for the Habsheim crash (in french .. never seen it released in english so far)
Zippyshare.com - Rapport BEA Habsheim.pdf (http://www75.zippyshare.com/v/55826267/file.html)

[john_tullamarine]

Folks,

We've had a few complaints about introducing Habsheim in this thread. If folks see a need to discuss, please raise a second thread to keep the two easier to follow.

[gums]

Thanks, JT. Was wondering how we got that except is does concern the alpha "protections" and such.

Glad to see a few that "believe" in a decent AoA indication that could have the "limit" AoA clearly marked for the pilot. The ones I flew really helped on approaches. You could compare the alpha with the calculated approach speed for your weight and configuration. Simple procedure and helped a lot on short fields and such.

Ditto for a basic HUD. I do not understand the "HUD resistance" here by several heavy pilots that seem to tolerate MFD's that are crowded with data and tapes and.... From my time in two great jets with HUD's, I truly believe the AF pilots would have seen what was coming before they went thru the stall envelope. Especially so if an AoA indication was there "hooked" to the flight path vector. And remember that the flight path vector is independent of any air data, so frozen or stuck aero sensors are non-players.

Such inexpensive displays that "help" pilots at low cost and not millions of lines of code and..... And still thinking about Asiana in this regard.

[HazelNuts39]

A33Zab,

Thanks for correcting me.

[gums]

As a matter of fact, our pioneer FBW system did not have a stall or AoA warning.

We had a "slow speed" warning based on aero data if below 120 knots with gear up. Otherwise nothing. The limiters ( called "protections" by the 'bus community) were active for AoA all the time if weight off wheels. In short, we could "pull" as much as we wanted, but the FBW system limited our max AoA depending on configuration. Didn't care about airspeed if gear up or WoW switch not compressed.

I never worried about ":floors" or "protect" or any of that. Just flew like we used to when the Earth was still cooling and everything worked out, except it was very hard to stall.

[roulishollandais]

I already gave the link but it seems ppruners did not search it. The text is from the MIT about the HUD presented par the courageous French test pilot and test engineer, professor at Ecole Supérieure d'Aéronautique Gilbert KLOPFSTEIN† Massachusetts Institute of Technology Charles Stark Draper Laboratory

MEMORANDUM

TO: Distribution FROM: Dunbar. C. Collins DATE: 20 october 1972 SUBJECT: Demonstration of the French Thomson - CSF, All Weather Approach and Landing Monitor (TC-121) Heads Up Display

On September 25, 1972 a technical presentation and flight demonstration of the subject system was given to interested MIT personnel by Mr. G. Klopfstein, Engineer in Chief of a technical mission from Ecole Nationale Superieure De L'Aeronautique of France.

The mission crew has been demonstrating the system in a French Nord 262 twin-engine turbo prop for the past month to pilots/engineers of USAF, FAA,NASA, Pan American, and the like.

MIT attendees were:

J. Nevins* C. Collins* (Pilot A) I. Johnson* J. Dunbar* (Pilot B) M. Connelly* J. Allen* G. Edmonds* B. DeWolf* A. Chavlagon J. Sciegienny N. Polner I. Levin

*Participated in flight demonstration

Technical Presentation (approx. 1 1/2 hours): Mr. Klopfstein discussed the systems design philosophy, derived the desired display parameters and generally described the system’s hardware elements, performance capabilities and operating techniques. Unfortunately, time did not permit a detailed technical description or discuss ion of system performance. Mr. Klopfstein promised that this data would be transmitted to us. When it is it will be circulated to the interested parties.

This system presents a novel solution to the problem of displaying to a pilot, in a simple manner, all the necessary para* meters for achieving trajectory control without exceeding the aircraft operational constraints.

It was shown that relatively few parameters, i.e., flight path angle, angle of attack and energy margin indication can provide more useful information than many parameters normally displayed (pitch attitude, rate of climb, RPM, power ratio, airspeed, etc.).

The advantages cited were simplicity and reliability which provide ease of training, safety during emergencies, improved cruise flight control and marked improvement in landing performances, i.e., a reduction in landing point dispersion from 600 meters to 60 meters in evaluation flights by a French test group.

Manual control with this system is reported to be as accurate as automatic control in all weather conditions in cruise, landing or taxi operations.

Some points resolved in the presentation were:

1. The primary inputs for trajectory control and energy management can be provided by a vertical gyro for pitch angle, a local angle of attack sensor (linear relationship to true a) and vehicle X, Z axis accelerometers. These are the elements of the CV91 visual guidance display. Fig. 1 shows the CV91 “black box”. The system reportedly sells for approx. $10 000. The VOR-Localizer capture function requires additional ILS inputs, radio altitude, heading and roll angle which are embodied in the TC121 display.

2. The system is self corrective for headwind component during final landing approach but a curved flight path trajectory results. This may be avoided by manual compensation (holding velocity vector up - runway for headwind) or by setting a console control to the value of the reported wind to bias the velocity vector marker.

3. Pilot induced oscillations are minimized in that flight path angle response to pitch inputs is a smooth first order curve.

4. The angle of attack display provides much better lift control than that achieved through an airspeed display. Angle of attack is measured more accurately than airspeed and also eye discrimination of 1/20° can be attained with the collimated display.

5. Minimum landing point dispersion and consistent touch-down velocity is best achieved with a two-slope trajectory, one of 2 –3° and a final of 0,6 –1.0°.

Operations oriented descriptions of the TC 121 and CV9l are contained in the Thomson - CSF brochures available from J. Nevins, Ext. 8-1347. Selected excerpts from these brochures are attached. A written transcript of the technical presentation has been promised to MIT.

Flight Demonstration (approx. 1 1/2 hours): Two flights were made to enable the MIT pilots to evaluate the system and to provide a TV monitor of the TC12l pilots display for a number of observers. A 20minute warm-up/alignment of the inertial system was required prior to the first flight and a 1 to 2 minute hold for realignment during the ramp stop, engines running, between flights. The inertial system used for this demonstration is also used in French fighter aircraft and is classified.

Cockpit configuration of the system displays included:

a. A linear scale instrument, located in the cockpit, which displayed flight path angle and potential flight path angle markers against a calibrated pitch scale. (fig. 3)

b. A co-pilot station, glare shield mounted CV 91 visual guidance display (Fig. 3, shown in retracted position).

The CV 91 is used to facilitate visual approach on runways without glide path facilities.

Symbology:

The flight path marker is manually set to a desired flight path angle by means of a selector switch on the center console. There were no angle calibrations on the display, nor horizon. The size of the cross is a reference value.

c. A pilot station, overhead-mounted, all weather TC 121 Heads Up Display. This station was off limits to guest pilots due to possible collision of HEAD and HUD.

The procedure followed was to demonstrate the bas ic concepts of the system on the linear instrument and then to familiarize each pilot with the control-display response of the CV 91 from the co-pilot' s seat.

The pilot varied power, lowered flaps, dropped the gear and simulated engine failure to demonstrate ease of energy management. In each case the lowering of gp marker supplied a simple, natural cue for response. i.e. increase power if available or lower g marker by pitching down until g and gp are aligned. The MIT pilots easily established climbs and descents at selected angles and adjusted power accordingly for energy equilibrium (T = D).

Although overshoot of power settings was noted on the display the changes in configuration and trajectory were accomplished with little airspeed variation (1 to 2 knots).

Pilot induced oscillations appeared minimal.

Control of velocity vector was simple and positive. Angle of attack control by power management was also exercised and found to be easily performed. The use of the velocity vector as an aiming device was also demonstrated during a descent through clouds by pointing it at a hole, and following through. The same principle can be applied in mountainous terrain.

An ILS approach and landing on Runway 11 was demonstrated by the pilot. Surface wind was approx. 240/15 Kt. Subsequent landings by MIT pilots were made on Runway 29.

The primary pilot tasks were:

1. Accomplish turn on to final approach

2. Establish glide path by holding velocity vector on the runway threshold (glide-path pre-set to 2 ½° )

3. Make heading corrections to align flight path with runway center line (strictly visual) .

4. Adjust power to approx. align gp and velocity vector,

5. Keep angle of attack within reasonable limits.

6. Cut power fully at pilots command (approx. 60 ft. altitude) and flare by pitching up to align velocity vector with far end of runway.

7. Maintain direction and velocity vector aim point until touchdown.

First approach (pilot B) was flared too early and touchdown was attempted by the standard method of “feeling for the runway”. The touch-and-go landing was completed by the pilot.

Two More approaches were made with the CV 91 used for both glide path and flare. Both touchdowns were smooth with landing point as targeted.

Pilot A then made 4 approaches and landings with consistently good results.

The system really facilitates the visual approach - there is no unnecessary jockeying of controls or preoccupation with altitude, airspeed, rate of descent, power setting, etc.

The aircraft was very stable.

Crosswind was no problem.

The CV 91 display brightness was adequate for the variations in background encountered, mainly cloudy with fair to poor visibility. Brightness is adjustable. The field of view, a 90 mm pupil, seemed adequate. There was no vibration and no appreciable obstruction of forward view.

The format is simple and easy to interpret.

Although we would have preferred to fly the TC l2l display to view the more complete symbology, we feel that the CV 91 flight adequately demonstrated the basic concepts.

It is suggested that altitude below 1000 feet be displayed digitally in 10s of feet similar to the flight path angle display on the TC121.

In summary, the system offers a number of advantages. It provides an on-board capability for making precision (visual) approaches to non-instrumental landing sites. It provides flight performance cues which do not exist in the ordinary flight director attitude displays. It has particular value for off-nominal flight conditions, i.e. in the event of an engine failure the pilot has the cues to enable him to immediately assume the proper pitch attitude which will result in the best engine-out climb speed. It may have great value in application to the military tactical environment in a forward area where a minimum amount of navigational and landing aids would be available, It certainly is an excellent prototype flight test tool.

Distribution

Attendees plus R. Duffy H. Hagan N. Sears H. Trueblood D. Fraser P. Felleman Prof. T. Sheridan Prof. P. Whitaker Prof. R. Curry

[A33Zab]

What I found shocked me.


What exactly shocked you?

[Turbine D]

Boeing 737-800 ILS HUD Landing

B737-800 ILS HUD - YouTube

I believe this is the BAE System's HUD. Although the camera is shaky, the HUD contains all the seemingly important instrument information (nearly 60 pieces of information is presented) while looking out the windscreen. The symbology pretty much matches the heads down primary display. Alaska Airlines, and some Southwest and American 737s have HUDs, but maybe not all aircraft are equipped.
HUDs are standard equipment on the Boeing 787s, both LH and RH seats.
As I understand it, the idea is for the PF to look through the center of the HUD and fly the flight path symbol, but incorporate the side displays in his periphery vision as to how they maybe changing.
I am not sure an installed HUD would have been the answer at the KSFO Asiana landing without an operating ILS system, but a VMC approach mode might be available on the HUD, but flight path only indication.

[OK465]

Brit, Oz, NZ? (they all sound the same to me :})....

But in any case whoever it is has opted for the AOA display. :)

[Turbine D]

OK465,

They are all US airlines.:)
Alaska Airlines were very proactive on HUDs because of the weather conditions (poor visibility) experienced on their routes among other reasons.
You noticed the AoA display!:ok:

[OK465]

Listen again. :)

Notice the flashing AIII....the mode they eventually reverted to is the default IMC mode, lowest mode level, and is the same mode that would be in use during visual VMC approaches or NPAs, though without necessarily the ILS capture they have.

Something's not tuned or selected compatibly with AIII moding.

[Lonewolf_50]

HN39
The whole issue is somewhat trivial compared to the need to avoid getting to an AoA of 42,5 degrees in the first place.
Seems to be a wetware issue, not a hardware issue, nor a software issue. ;)

Also true, and not just for an A330.

[Turbine D]

OK465,
You are correct .
I thinking the AIII mode flashes when it is available but not selected. I also think in the video they switched to the IMC mode to reduce clutter.

[gums]

Thanks for the graphics, Turbine.

As with modifications of the military HUD symbology, I feel they are trying to portray too much info, and some will be overwhelmed by trying to keep up with all the stuff. So I prefer "de-clutter" options and a simple glance at basic gauges as part of the cross check.

I include a video that has lessons for the Asiana crew. If you don't have Quicktime, there are free viewers out there. So download and view at your leisure. The incident was "severe" structural problem, so I flew a very high approach speed ( about 30-40 knots above normal) and made a shallow approach to avoid a normal "flare". I didn't get slow like Asiana, but we shared too low of an approach angle and it almost bit me. But using a bit of power I corrected at the end and made it to the end of the runway. In that configuration you lose roll authority if getting slow and/or pulling back for touchdown. So actually seeing your "impact" point with the velocity vector can really help. just looking thru the windshield might not be enuff.

Reason for the approach is this:

http://sluf.org/misc_pages/rightwing.jpg

Video is here, and note last 30 seconds of the approach.

http://www.sluf.org/warbirds/lef-landing.m4v

Confirmed user and believer of the HUD.

[Chris Scott]

Quotes from Clandestino (Nov 15 (http://www.pprune.org/tech-log/511119-af-447-thread-no-11-a-40.html#post8156336)), replying to my post of Oct 25 -

(1) "I'm sorry Chris, if my caustic style caused you to believe I was going for a cheap shot here. To make my position clear: I do not find any of the theories that there was anything remotely rational in CM2's action and it was just misunderstanding and misapplication on his part plausible. He meant just to return to altitude? He busted it by a couple of thousand feet."

It's not your position I took issue with (on the contrary) - merely your misinterpretation of mine. My suggestion of an initial "knee-jerk" reaction implies, by definition, an absence of rationality. Explanation is not justification.

(2) "Again: issue with AF447 is not the pilot unable to handfly the aeroplane; it was pilot unable to understand the situation, implication of his actions and pretty precisely handflying just the wrong way..."

So he handflew in the wrong way, but not because he was unable to handfly? He knew that he wanted to maintain altitude but felt it necessary to keep pulling back on the stick to achieve such?

(3) "Nothing of it can be prevented by practising eye-to-hand coordination in friendly skies."

I could not disagree more. All that needed to be done in AF447 was to keep the wings level, and MAINTAIN a suitable pitch attitude and thrust for high-altitude cruise. If you are accustomed to monitoring and understanding your a/c in all flight phases, you may learn ball-park figures even without ever disengaging the AP. But there are at least two snags to that as a policy.

Firstly, you will not learn the very gentleness of any corrections that need to be made on the side-stick if you unexpectedly find yourself without the AP at high altitude. (Rather like driving a car at over 200 kph.) Secondly, human nature means that hands-on practice concentrates the mind in a way that mere observation does not. (The seat-of-the pants sensation when you over-control the stick concentrates it even more.)

The ball-park figures for PITCH attitude in different flight phases soon sink in, particularly if you turn off the FD, crew workload permitting. That's why you need to do it in your "friendly skies". The numbers may be something very roughly like the following, but you will soon learn them for your particular Airbus:
Cruise = +2.5; Step-climb on schedule (initially) = +4 (~1200ft/min); Descent at idle (initially) = -1; Low altitude Hold (level) at about Green-Dot speed = +5; Level flight Flaps 1 "S" speed (i.e., slats only) = +8; 3-degree glide-slope at the same speed and config = ...? ;)

(4) "Also this kind of reaction is very rare and trying to present AF447 as typical of the current state of affairs is misinformed at the best."

Well, I agree that the three main L.O.C. cases we have been discussing the last few months have involved different pilot reactions to problems in the cruise, but all have been seriously deficient:
A340 AIRPROX - no sidestick action for about 17 seconds during an FBW-induced, undesired zoom-climb;
AF447 - consistent back-stick causing a zoom-climb until and after the a/c entered a super stall;
AF A340 (Serious Incident, 2011) - inappropriate back-stick, causing AP to disengage, and initiating a zoom-climb that exceeded +2G twice, stalling the a/c.

(5) "...both AF447 and AA965 are subsets of the same archetype of accidents: pilots who find themselves on unfamiliar territory, are unable to recognize where they are and how to return to normal..."

Quite. And, as you imply, this is not a problem unique to Airbuses, nor even to fly-by-wire.

[vilas]

Chris
Pilots without jet experience have to undergo ELT MCC as part of Airbus type rating where Absolute raw data flying without ATHR, AP, FD, FPV is taught.It includes executing SIDs,Arrivals,Approach and landings. Out of eight sessions 6 are to be flown manually. So 447 pilots were not strangers to raw data flying.

[Chris Scott]

Hello vilas,

That's good news as far as it goes. But if hand flying raw-data - with and without FPV, and with and without A/THR - is limited to your first jet conversion - which is a very intensive experience, covering a bewilderingly wide sylabus of unfamiliar exercises and new technical concepts - the learning curve you climbed during those six sessions will fade away unless your airline sanctions the disengagement of different combinations of automatics at suitable times during revenue flights. Frankly, simulator time is now so expensive that it would be unrealistic to expect airlines to schedule it during recurrents - unless it was combined with other failure exercises. :}

During the first few years as a copilot you slowly adapt to the demands of the routine chores, and much of what was covered in the conversion is gradually forgotten. That is particularly unfortunate if you happen to be on long-haul, and lucky to get your one landing a month. Six-monthly checks are formalised, and the areas to be covered in the next programme are promulgated in advance for study and discussion. Apart from the mandatory items, such as rejected T/O and EFTO, the exercises tend to revolve around the complexities of systems failures. In the LOFT exercises, use of automatics during problem-solving tends (rightly) to be emphasised. There is little or no "fat" in the simulator schedule to permit ad-hoc flying practice for youngsters (or the oldies).

In line operations, the selective withdrawal of automatics I'm advocating is done at the captain's discretion, and with prior agreement. It should not be done at times when PNF workload is already high, which of course is more likely when one of the pilots is relatively inexperienced. It would not be programmed, formalised, or recorded; just regarded as a routine interlude of enjoyable self-development for the PF.

My perception is that the above is frowned upon in many airlines.

PS
What the :mad: is "ELT MCC"? Too much jargon, vilas! Jargon is what professionals use when they are trying to withhold understanding from lay people, and impress newbees...

[vilas]

Chris
I mentioned before that UAS procedure was/is not given due recognition as a likely scenario. Even now it is more of Demo during type rating and rarely practiced thereafter. In 447 they did not apply correct procedure. Regular practice of raw data no doubt will increase confidence but ignorance of UAS procedure may not save the situation.

[Chris Scott]

vilas,

I think PJ2 illustrated here some time ago that the Airbus UAS procedure was confusing; even potentially misleading. One hopes it has now been clarified.

Pilots need to understand better the basic mechanics of how their a/c fly. I'm not talking about complex aerodynamics. For example, if you pitch your a/c up 5 degrees in the cruise, it will soon start to climb at that angle (before it slows down appreciably). That's about 4000 ft/min initially. Do youngsters realise things like that nowadays?

[vilas]

That's exactly what is taught in Entree Level/MCC training. Thrust attitude thumb rules for climb cruise descent and configuration changes are given. Differrent manuevres are practiced and finally approach/GAs are practiced.

[Chris Scott]

And how is this useful practice and instruction to be consolidated?

[AirRabbit]

During the first few years as a copilot you slowly adapt to the demands of the routine chores, and much of what was covered in the conversion is gradually forgotten. That is particularly unfortunate if you happen to be on long-haul, and lucky to get your one landing a month. Six-monthly checks are formalised, and the areas to be covered in the next programme are promulgated in advance for study and discussion. Apart from the mandatory items, such as rejected T/O and EFTO, the exercises tend to revolve around the complexities of systems failures. In the LOFT exercises, use of automatics during problem-solving tends (rightly) to be emphasised. There is little or no "fat" in the simulator schedule to permit ad-hoc flying practice for youngsters (or the oldies).

Very well said, Chris.


In line operations, the selective withdrawal of automatics I'm advocating is done at the captain's discretion, and with prior agreement. It should not be done at times when PNF workload is already high, which of course is more likely when one of the pilots is relatively inexperienced. It would not be programmed, formalised, or recorded; just regarded as a routine interlude of enjoyable self-development for the PF.

My perception is that the above is frowned upon in many airlines.

Even better-said!!

And I think that there are primarily 2 reasons for what we see today.

First – airlines are in the business of making money – and, as almost anyone can understand, training does not make money … it only costs – and those costs are both direct (instructor salaries, salaries of students, equipment and facilities costs, etc.) and indirect (loss of line flying – which is the only source of income, transportation costs of moving the “students” into and back home from the training site, costs of per diem, lodging, etc.).

Second – airlines are loathe to provide more training than is required by the regulations. Why? Certainly cost is a significant driver, but I’m of the opinion that conducting training beyond what is required by rule could be seen by some as management recognition, or at least suspicion, of the existence of a sub-par capability, attitude, or ability on the part of existing crewmembers. So, simply by having regulatory required standards, lessens the willingness of some to continue to provide training beyond that required by rules. Some airlines in the US have adopted training under what has been described by the regulators as a voluntary program which has a unique characteristic … and that characteristic is taking advantage of building a training program with “alternative” training goals, “alternative” standards, and uses “alternative” training equipment, which can be extended to “alternatively approved” intervals. Personally, I think this situation is one that has resulted in airlines being able to save significant amounts of money, prompting the appropriate industry training managers to go to great lengths to compliment the regulatory authority for such “forward thinking” … which, of course, does not hurt the professional aspirations of those few regulatory officials ultimately responsible for such authorizations. The problem is, as I see it – and I’m not alone - is that having multiple sets of “alternative” standards applicable to “alternative” programs, each using “alternative” equipment, to complete “alternative” task assignments, on “alternative” recurrent schedules results in a “drifting away” from standardized expectations of performance and capabilities of these crewmembers, particularly pilots … all based on the economic value being contributed to the airline bottom line.

I am not about to apologize for believing it appropriate that airlines pay their employees a just wage for the skills and abilities they must possess and demonstrate; that airlines should provide their employees frequent and meaningful training, both initially and on an appropriate recurring basis – using equipment and facilities that are appropriate for the tasks that must be accomplished; that airlines should provide equipment and facilities to provide transportation services to those who choose to use this particular method of transportation; that airlines should charge those who use those services a fee that will provide an adequate income to meet expenses AND meet whatever profit margin they deem appropriate. It simply cannot be expected that the employees, or the skills of those employees, should be expected to be sacrificed for competitive advantage over other similarly situated competitors. Of all of these components, the only ones that should be governed by rules and regulations are those of competency and capability – and they should be equally applied to all who choose to participate in this industry. To me, this means that the regulatory authority should require that all participants have, and be able to regularly demonstrate, that the required capabilities and competencies are, indeed, addressed and that each appropriate person has satisfactory knowledge and experience to regularly and correctly exhibit those competencies and capabilities whenever and where ever called upon to do so. Clearly, this cannot be done through the authorization of individually approved deviations from established standards – particularly when those specifics (and any differences) are maintained as “confidential.” The requirement should be – no MUST be – a single set of demonstrable proficiency standards, using demonstrably appropriate equipment, for all who are depended upon to execute the duties and responsibilities of appropriate crewmembers (both cockpit and cabin) involved in delivering these services to the traveling public. If the regulatory authority should NOT do these things … I wonder why it is that a regulatory authority is involved at all.

[vilas]

Chris
It is Entree Level Training/Jet Familiarisation/Multi Crew Cooperation. It can be consolidated during Refresher training and online but unless you know the symptoms and the correct procrdure of UAS you may not handle it competently and safely. Let us say a pilot is competent in hand flying but does not remember correct procedure of TCAS he can mess it up.

[Clandestino]

Glad to see a few that "believe" in a decent AoA indication that could have the "limit" AoA clearly marked for the pilot.What limit?

The pitots don't measure the angle of attack!What do they measure?

Indeed, 100kts TAS is well enough to register an AoA on a balanced probe 100 kt in which direction?

why besides the AoA a speed indication is needed to determin wether you are in a full stall.Really, why?

Why keep the 60 kt logic when airborne?Really, why?

At the moment we are discussing the inconsistency of the stall warning, right? What inconsistency?

Due to an airspeed, which was inconsistent in itself?
And therefore rendered an available AOA indication as unreliable? What occurrence are you discussing here?

And you think, that is a logic system in itself and not worth improving?Improved in what way?

That sounds suitably over-complicated. How would you simplify it?

I can understand that some input like speeds are necessary to compute the exact angle of attack.Why is it so?

Why not implement a logic, where an AOA value above the highest stall onset AOA bypasses the above logic and thus keeps the stall warning active?Really, why not?

no - the lack of stall warning when the Captain arrived in the cockpit was non-'trivial'.What occurrence are you referring to here?

I do not understand the "HUD resistance" here by several heavy pilots that seem to tolerate MFD's that are crowded with data and tapes and....What MFDs are crowded with data and tapes? How do you propose to reduce crowding?

We all now know, definitively, that (a) the AoA resolver outputs were available, and (b) that they were valid. Discarding them is unforgivable.Why every aeronautical power that be does not see that?

The “below 60kias” is a classic case of such an arbitrary false premise “knock out filter”.How many medium and heavy jets vent below 60 kias while airborne, ever?

That allows the aeroplane to tell a pilot, “Everything else, air-data wise, is tits up guys, but I still have valid AoA, any use to you ?TWA843

Cheap provocation, eh? Think again, gentlemen. All of these questions are answered many times during the course of 11 threads we had on subject yet same old opinions resurface again and again. Please put some effort in answering these, I would really like to know what you didn't understand last time and time before that and before that...


I never worried about ":floors" or "protect" or any of that.You were not supposed to return it to earth unscathed if everything went southward so not much point in having backup FCS modes. No ACES in passenger jets.

As I understand it, the idea is for the PF to look through the center of the HUD and fly the flight path symbol, but incorporate the side displays in his periphery vision as to how they maybe changing.Well... might be idea but it doesn't work out this way. I'd estimate the display to be 2 - 2.5 times wider than PFD and display being monochromatic aggravate the complete scan. It excels at visual approaches where any change in flightpath is immediately recognized as conformal flight path vector jumps around and that's the only thing you need to know besides speed. It is excellent for CAT3a approaches where there is not much scan anyway - you just make perfect doughnut with aeroplane symbol and guidance cue, shorten the speed error tape as much as possible, keep energy caret aligned with wing symbol using throttles (all of the symbols are concentrated in the middle of the HUD so you just stare straight ahead) and rely on F/O scanning classic PFD and HGS annunciator panel to shout "GUIDANCE" if things go pear-shaped.

My suggestion of an initial "knee-jerk" reaction implies, by definition, an absence of rationality. Explanation is not justification.It's not kneejerkiness I don't agree with, it's idea that pull-up-no-matter-what came initially from attempt to return couple of hundred feet lost on altimeters when speed correction went missing.

So he handflew in the wrong way, but not because he was unable to handfly?Exactly! He did not understand what happened despite uttering "We have no good display of speeds" so had no idea the best thing to do under the circumstances was...to do nothing. Pull was so consistent that it just couldn't be unintentional. Problem was within cognition.

He knew that he wanted to maintain altitude but felt it necessary to keep pulling back on the stick to achieve such?No. He didn't know anything. He wanted to pull-pull-pull for reasons he never verbalized. If he was afraid of overspeed and tried to trade speed for altitude, why going to TOGA? As soon as the AP dropped out, all the thinking on the FD stopped for good.

All that needed to be done in AF447 was to keep the wings levelDone.

and MAINTAIN a suitable pitch attitude and thrust for high-altitude cruise.Yes but this is all very well when you either know what happened or maintain presence of mind not to do harm when you are not sure what exactly you should be doing.

Firstly, you will not learn the very gentleness of any corrections that need to be made on the side-stick if you unexpectedly find yourself without the AP at high altitude.You suggest that A330 is sensitive beast that has to be treated gently. I say that it is exaggeration and you can throw her around hamfistedly at cruise altitude, in alternate law for 4 minutes with normal acceleration varying between +1.96 and -0.26G with end result being no worse than just utter mess in cabin and galleys.

How are we going to resolve this?

Well, I agree that the three main L.O.C. cases we have been discussing the last few months have involved different pilot reactions to problems in the cruise, but all have been seriously deficient: Why are we not discussing some other LOCs like Birgenair? 20 000 hrs could not prepare the skipper for simple recognition that rejecting the takeoff when airspeed is not working is a must or just to crosscheck the three ASIs. Or close call at EHAM where the guy who taught others how to perform V1 cut just couldn't make it properly when it happened for real? That's what AF447 is about: the crew that just couldn't perform when it needed to. It's very ugly picture and I understand the need to try to overpaint it with unrealistic theories about FBW or instrumentation.

Pilots without jet experience have to undergo ELT MCC as part of Airbus type rating where Absolute raw data flying without ATHR, AP, FD, FPV is taught.It includes executing SIDs,Arrivals,Approach and landings. Out of eight sessions 6 are to be flown manually. So 447 pilots were not strangers to raw data flying.Depends on what local CAA will allow, operator demand and training organization provide. In my case it was all spiced up by flying in direct law. It was piece of cake but then it was sim, not a real aeroplane over Atlantic at 4AM.

OK I'll give up quoting for a bit but when making sweeping statements about general flying capabilities of modern pilots, bear in mind that more than 30 other crews passed through same ordeal without a scratch and at least four of them were Air France.

[Machinbird]

You suggest that A330 is sensitive beast that has to be treated gently. I say that it is exaggeration and you can throw her around hamfistedly at cruise altitude, in alternate law for 4 minutes with normal acceleration varying between +1.96 and -0.26G with end result being no worse than just utter mess in cabin and galleys. Do that in roll direct and I suspect you will learn gentleness, and there might even be an additional mess in the cockpit.:}

Alternate1 and Alternate2 laws might work similarly in pitch, but they bear no resemblance in roll.

[gums]

In response to Cland, the three points where I was called out .....

a) Seems to be confusion here, even amongst the 'bus drivers about the various "alpha" limits or protections or whatever. And when one is the actual FCS limit. So if the FCS doesn't have an absolute AoA limit, then at least show the pilot the stall AoA.

My system had AoA limits depending upon A2A loadout, heavy iron on the wings or in landing configuration. We could only select the A2A or A2G limits, not the gear down limits.

b) Looking at my HUD video you will see what most considered the minimum displayed data for a safe and precise approach. The ILS cross bars are easy to understand. AoA bracket shows where you are and when aligned with the flight path marker( FPM), where you should be. Heading, altitude ( AGL or baro) and speed.

If you want some kinda "magenta line" to helpsteering , fine, but that can be a symbol that you keep aligned with the FPM. Had that on my A-7D, but no autopilot connection to anything. Viper was pure manual, as seen in the video.

c) We had one important backup mode - Standby Gains, which is extremely relevant to our discussions here the last three years. If air data was deemed unreliable the FCS used a fixed value for "gains". One with gear up, and the other gear down. Sure, if way off of the Q that the system used, it got touchy or sloppy. but very easy to fly, much like the "old days" when we didn't have all that stuff.

We did not worry about a myriad of alpha stuff, as we had one with gear up and the other gear down. Both limited the jet to stall AoA ( roughly). You could not command above those limits as the AF447 folks did. Could still run outta energy in a steep climb and momentum would allow the jet to exceed the limts because the flight controls could not react quickly enough ( very hard for our jet, and even more so for the heavies, IMHO).

Having an ACES II seat was very comfortable, and several of my friends are true believers. One, and main reason I never wanted to fly the heavies after getting out was the responsibility of many SLF behind me. If I screwed up, or the jet screwed up, so it was just me. Ain't gonna talk about that anymore.

.....and I assume Cland and maybe one or two others have bothered to look at my HUD tape of the emergency landing. Otherwise, much of my views could be misunderstood.

[BOAC]

Chris Scott - I have just found your post #800 buried in the grass at the bottom of a page (missed it previously). Your point about 'trigonometry' is irrelevant when we were talking AoA signals and is only relevant in terms of IAS which only enters the fray due to some software code. Therefore it would not matter if the jet was flying backwards or upside down - an airflow of that magnitude would, I suggest, generate a 'useable' AoA signal. Whether the designers choose to ignore that signal is another matter. That was one of the errors of design.

Clandestino said How many medium and heavy jets vent below 60 kias while airborne, ever? - not sure what 'vent' means here, but it does appear that the designers forgot this very important 'trigonometry' and that a jet in a fully developed stall can and did, in fact ?'vent'? below 60kts (IAS).

[Owain Glyndwr]

@BOAC

Firstly let me say that I am NOT arguing that the A330 design does not need any change - on the contrary I think the stall warning logic should be altered. However the discussion relating to validity or otherwise of the AoA signal does, I think, ignore some relevant facts:

Your point about 'trigonometry' is irrelevant when we were talking AoA signals and is only relevant in terms of IAS which only enters the fray due to some software code. Therefore it would not matter if the jet was flying backwards or upside down - an airflow of that magnitude would, I suggest, generate a 'useable' AoA signal. Whether the designers choose to ignore that signal is another matter. That was one of the errors of design.I doubt very much whether usable AoA signals would be generated if the aircraft were flying backwards or upside down, but I imagine you wrote that tongue in cheek ...
More to the point, if an equipment manufacturer declares in his formal paperwork that his equipment will work to specification only inside a given range of ambient parameters then the aircraft designer has no option but to conform to those limits. It is not a case of design error but one of a fully auditable certification trail.
The problem comes of course when the system sees input conditions which say that the operating limits of the equipment have been transgressed, but the measurement of those ambient parameters is itself false. To that extent Chris Scott's comment on trigonometry is relevant - the input data, in this case airspeed, was rendered false by the angle at which the airflow entered the pitots. Was it then a design error to fail to consider this case?

- not sure what 'vent' means here, but it does appear that the designers forgot this very important 'trigonometry' and that a jet in a fully developed stall can and did, in fact ?'vent'? below 60kts (IAS).I doubt very much that the designers "forgot" that an AoA in excess of 40 deg would give stupid speed signals, but they did of course fail to believe that a trained pilot would allow the aircraft to get into that state. Be fair, would you have believed it before publication of the AF447 final report? In which regard I would refer you an earlier posting, from PJ2 I think, that designers work on an assumption that the aircraft will be flown to a given set of rules, allowing for some sensible variations thereto, but not to any extreme one cares to dream up.

So what of their treatment of the stall warning which is, when you go back to basics, the reason for all this discussion?

With hindsight the logic is faulty, but I don't see any need to alter the logic governing validity of AoA signals which might well bring on other problems we know nothing of. Instead I would propose a change of stall warning logic so that if triggered by a valid AoA signal it should stay latched on until it received another valid AoA signal that stall conditions were a thing of the past. That would have avoided the confusion found in the AF447 cockpit for a minimal change to the aircraft systems. It would also, incidentally, bring the aircraft into line with the latest EASA requirements on the subject.

[BOAC]

Indeed "tongue in cheek".

I don't think I have ever argued that AB was partly 'responsible' for the accident due to the Stall warning 'logic', but just that it was significantly contributory. I agree people would not 'expect' the crew to take an airliner to these realms. However, why WoW was 'abandoned' I do not know - I thought it was a well-proven input? Surely the point is, Owain, that as far as we know there was a 'useable' AoA input available, probably throughout the episode, and indicating a stalled wing. The fact that 'trigonometry' rendered the USE of this signal impossible due to the IAS constraint is indeed relevant, but I cannot see why posters are going on about 'non-swivelling pitot tubes' etc etc. Surely we all understand why the IAS reading was invalid?

I agree with your last paragraph and if that is also the EASA thinking, then good, although as with all ever-increasing complexity of systems there may well be a hidden pitfall in that approach.

[Chris Scott]

BOAC,

The post of mine that you refer to was merely an attempt to explain to you and rudderrudderrat that you were misunderstanding Clandestino's cryptic remark about trigonometry, and taking seriously his reference to "no swivelling pitots". It was not a statement of my own opinion, merely an attempt to help you understand his point in his absence (for which, predictably, he has offered me not a word of thanks).

It's well known that Clandestino's style of response sometimes invites irritable misunderstanding by the passing objects of his contempt, myself included. Did my polite, but non-didactic, explanation go over your head? Should I have tried the long version?

(Ah, I see OG has done a far better job!)

[BOAC]

....and I hope you understood my t-i-c remark about there always being a reading from an AoA probe (given enough wind to 'swivel' - that's for real) regardless of 'trig'?

[Chris Scott]

Affirm, BOAC :ok:

[Owain Glyndwr]

BOAC

I don't think I implied that you were arguing about responsibility - if I gave that impression then my apologies. Nobody is going to contradict a statement about the S/W anomalies being a contributory cause though.

So far as WOW is concerned I don't think I have ever seen anything from Airbus on the subject - mostly the argument about it being 'abandoned' seems to emanate from PPRuNers speculating - but I stand to be corrected. What I would say is that leaving aside the AF447 affair, the existing logic functioned without complaint for several decades; why take the head off if it is working?

Now if your objective is to supply an AoA signal pure and simple and which is not going to be used as an input into some more flight critical system then I would agree there may be no need to complicate life by making that signal contingent on some other input - it being tacitly assumed that the aircraft will not be flying at a real 60 kts indicated or otherwise. Implicitly here I am taking the view that since airline pilots have been flying without AoA information since the year dot such information cannot really be classed as flight critical no matter how useful it might be in certain circumstances. [pace gums!]

I entirely agree your point about non-swivelling pitots etc.

To be clear, my remark about EASA requirements simply reflects the latest stall warning requirement CS25 207 (c) which, as I have said before, differs from the requirement applicable at the time the A330 requirements were frozen.

[gums]

Good thots, OG.

To be honest, I don't know when the Viper FCS ignored AoA or didn't. Best I have in documents is that it was used as long as we had WoW switch decompressed. When I did a tail slide one day all the warning lights came on ( AoA sensors at limits, calibrated speed below 120 knots) and without resetting them, I had complete control once the nose fell thru. Reset the FCS panel and fight was still on, heh heh.

OTOH, the A-7D and other jets displayed the AoA whether the plane had a FBW system or not. Viper didn't, as some folks the braket was a nuisance symbol in the HUD.

I learned in planes that had very clear warnings you were approaching a stall. In later planes, we had buffet and wing-rocking and such to let us know we were reaching the edge of the envelope. It was a different feel than when nearing critical mach, which usually exhibited stuff like aileron reversal, nose tuck and a pronounced "buzz" in the airframe as the shock waves formed.

So my thot is that a display should be available and right in front of the pilot whether the FCS or Otto is using it.

[DozyWannabe]

So far as WOW is concerned I don't think I have ever seen anything from Airbus on the subject - mostly the argument about it being 'abandoned' seems to emanate from PPRuNers speculating...

I'm wondering if that speculation stems from the 1993 LH A320 accident at Warsaw, where the WoW timing was not sufficient to allow deployment of spoilers:

Lufthansa Flight 2904 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Lufthansa_Flight_2904)

In response to that, Airbus reduced the required pressure on the WoW sensors, but they never abandoned it as a systems input.

OG, I'm almost certain you're correct in that the <60kts AoA NCD flag has nothing to do with determining air/ground mode - it's purely an attempt to enforce the AoA vane manufacturer's specified limitation of minimum 60kts airspeed for valid data, and prevent junk data from being used in FCS calculations.

[HazelNuts39]

Just a reminder - the Final Report para. 1.6.11 says it thus:
If the CAS measurements for the three ADR are lower than 60 kt, the angle of attack values of the three ADR are invalid and the stall warning is then inoperative. This results from a logic stating that the airflow must be sufficient to ensure a valid measurement by the angle of attack sensors, especially to prevent spurious warnings.

[BOAC]

...and should read If the CAS measurements for the three ADR are lower than 60 kt, the angle of attack values of the three ADR are considered to be invalid and the stall warning is then rendered inoperative. and hopefully re-thought, having seen vanes moving on walk-rounds in a stiff breeze! I'm sure the intention was well-founded, but hindsight tells us the application was not, and WoW would have been far better.

[DozyWannabe]

...and should read and hopefully re-thought, having seen vanes moving on walk-rounds in a stiff breeze!

With all due respect, there's a difference between "moving" and "providing valid data".

I'm sure the intention was well-founded, but hindsight tells us the application was not, and WoW would have been far better.

See above - I'd be surprised if WoW was not an input *in addition* to the <60kts IAS check, as opposed to "instead of". This is purely a way of preventing duff data from getting into the flight control systems calculations - entirely separate from air/ground mode determination.

[Owain Glyndwr]

Dozy
I'm wondering if that speculation stems from the 1993 LH A320 accident at Warsaw, where the WoW timing was not sufficient to allow deployment of spoilers:

In response to that, Airbus reduced the required pressure on the WoW sensors, but they never abandoned it as a systems input.

That of course is a totally different application. For the record (I don't want to introduce another thread drift) it wasn't that WOW timing was adrift.Rather it was that the aircraft touched down so fast that even when derotated there was so much residual lift with full flaps that there was not enough weight on the wheels to overcome the breakout friction and allow the WOW microswitches to 'make' AI did introduce a software modification as a result but I cannot remember the details.

[DozyWannabe]

@OG - check the Wiki link.

The spoilers [were] only activated if at least one of the following two conditions is true:

- there must be weight of at least 6.3 tons on each main landing gear strut
- the wheels of the plane must be turning faster than 72 knots (133 km/h)

Followed up with:

As a result of the accident, Airbus Industrie changed the required compression value from 6.3 tons to just 2 tons per main landing gear.

I remember the timing issue because the left gear touched down 9s after the right - it was the delay in the left gear getting the required compression value that caused the delay in spoiler deployment.

[EDIT : I'm aware that it's a totally different application, I was simply trying to distinguish the air/ground mode criteria, which are not relevant to AF447, from the AoA vane maker's specified NCD threshold of 60kts, which is. ]

[OK465]

Would anyone like to know how much ADR/CAS independent AOA the digital portion of the display seen in Turbine Ds HUD U-tube link will indicate?

Probably not. :}

[DozyWannabe]

Would anyone like to know how much ADR/CAS independent AOA the digital portion of the display seen in Turbine Ds HUD U-tube link will indicate?

I, for one, would!

In fact I'd be exceedingly interested to see how the interoperations between flight control systems (both traditional and FBW), warning/alert systems and AoA sensing equipment pan out on every type in passenger service when exposed to values as extreme as AF447.

I don't think it's a shortage of people wanting to know - I think it's more a shortage of willing volunteer pilots* to fly the profile!

* - Because most pilots don't have a death wish...

[Owain Glyndwr]

@Dozy

Nearly but not quite:

The logic to trigger deployment of reverse thrust and lift dumpers required either both mainwheels to be on the ground [signalled by position switches on the landing gear torque links], or one mainwheel on the ground and a rotational wheelspeed equivalent to a ground speed of at least 72kts. Brake application depended on mainwheels spinning up to 80% of a computed reference speed, which is normally the rotational equivalent of ground speed, with special treatment during the transitional touchdown "spin up" phase. Because of the excess airspeed, the aerodynamic lift was much greater than normal, so that the ground reaction on the landing gear was very low. Taken in conjunction with the flooded runway, this provoked aquaplaning of the tyres in contact with the runway, so that they never got up to the required rotational speed, and brake application and the application of spoilers/ reverse thrust was delayedChecking back on my source data another AI mod was to apply a small amount of dumper deflection immediately at touchdown, which killed enough lift to trigger braking but which was not enough to hamper a go around.

[Chris Scott]

Thanks for the quote, OG. Yes, one mainwheel has to suffice. Landing with residual bank (e.g., deliberately on the upwind main gear in a strong crosswind) provides routine ground-spoiler deployment, encouraging the downwind wheels to touch down in short order, even if the pilot leaves a lot of into-wind aileron applied (in the transition to ground law). The sudden loss of roll-spoiler effect is partly responsible, of course. With the nosewheels down, IIRC, nosewheel steering is not available above the 72 kt ground-speed, whether rudder-fine or tiller.

(Excuse the off-topic memoir.)

[Turbine D]

OK465,

I would like to know. I believe the green band is indicative of 3º at nominalized conditions on a B-737. The tick line near the top represents stick shaker AoA, approach to stall.

[OK465]

TD & Dozy,

it's sort of a trick question in that....

ALL AOA data, both HUD (BAE) & PFDs is independent of the 2 ADR modules. (However there are other HUDs that have that annoying ADR/AOA dependence for AOA display.) Same with FPVs. This aircraft PFDs always display it and have FPV capability regardless of type HUD.

The green band is the non weight based AOA for the weight based approach speed with appropriate flaps out. The tick is as TD says the onset of the shaker. The PFD also has a PLI (pitch limit indicator) that corresponds to the 'tick' AOA.

The maximum digital readout one can see in an FFS is around 30.5 degrees, this with BOTH ADR modules failed, no air data. I think it's limited by the fact the aircraft just won't sustain more than that, unlike the 330. However that could just be the point it pegs for any AOA above 30.5, until AOA is reduced, a system somewhat I believe like RetF4 envisions. I wouldn't trust the sim much beyond this point however....yet.

IMO, contrary to some opinion, it is emminently easy to utilize as a performance instrument, not a control instrument, the data is already in the box and it just takes some OPC pin activation and CDS enabling to display it.

And you don't have to ever look at it if it's otherwise objectionable to you. We know who you are.:}

[gums]

Some good points, Okie.

My aero understanding and actual college courses and actual flying with AoA indicators tells me that the "stall" or max L/D is pretty much the same as long as you don't have all the flaps and leading edge devices and such taken into account. Weight is not a factor, as the wing doesn't care according to the configuration. It's the lift curve for the configuration, not the weight.

IMHO, there's no reason to display the "bracket" as we had in the A-7D displayed all the time in the HUD. Wanna put it someplace on the crowded MFD, then fine. So in the Viper, we only got the AoA bracket with gear down for approach. And since we didn't have a lot of extra aero devices than flaps, the bracket gave a super reference for approach AoA that was fully compensated for weight, as we should realize that AoA for stall or such doesn't care about weight or gee.

Not to say that the AoA indication is a panacea, as it has to take into account of aero configuration. The display can be raw or it can be biased depending upon configuration. But it sure as hell tells you where you are and where you should be. Simple cross check with actual speed that you or your right seater calculated/looked up will help. Bit me in the butt one night on a slick runway when my trailing edge flaps were not fully deployed, but leading edge flaps were fine. So optimum AoA was higher speed than I should have been flying and I almost ran off the other end of the runway. BFD, lesson learned, as I had placed my trust in the "optimum" AoA for the approach.

The thing I keep harping on is that neat HUD that shows actual flight path vector based upon inertial data ( could be actual or a blend of pitch and some gyros). If I pulled and the FPM didn't move "up", then I was pulling too hard or was close to a stall. The pitch lines were also very comforting, especially for a night takeoff or for a carrier shot, because if that FPM was not above the "horizon line", then you were descending regardless of your basic attitude indicator display. I was taught, and flew many hours in bad weather and had to use the basic attitude and power specified/recommended. Then cross check for altitude and vertical velocity. Anyone here that didn't fly that way?

In almost 2,000 hours of HUD flying, I only had the FPM invalid once ( translate to 10,000 hours for you heavies). I knew it instantly and used the steam gauges to continue the takeoff. That was in Viper, as the A-7D used TAS and gyro attitude to provide a poor man's FPM.

I also experienced a static port freeze one day upon descending for a TACAN approach. Airspeed went to hell as I changed altitude, and altitude was frozen. BFD. I had that neat FPM and those pitch lines to tell me I was doing fine. Comforting. Set power per normal and come on down. I would have done the same thing without the HUD and inertial FPM, just as most here would have done. Basic airmanship and flying skills, ya think?

[Clandestino]

Do that in roll direct and I suspect you will learn gentleness, and there might even be an additional mess in the cockpit.

Alternate1 and Alternate2 laws might work similarly in pitch, but they bear no resemblance in roll.What relevance it has to AF447? For Finnegan's sake it didn't crash in spiral dive or rapid roll to ocean but in upright stall! That's what happens when you try to pull the aeroplane where she just can't go perfomancewise.

So if the FCS doesn't have an absolute AoA limit, then at least show the pilot the stall AoA.Herein lies the rub; on 330 it is very much mach and configuration dependent. No airspeed - no mach - no meaningful alpha limit.

If you want some kinda "magenta line" to helpsteeringWho gives a rat's stern about my wishes? I have commented on the way I performed visual (no steering cue) and CAT3a (cue required) approaches using head-up guidance system I.A.W. what my employer expected of me.

We had one important backup mode - Standby Gains, which is extremely relevant to our discussions here the last three years. If air data was deemed unreliable the FCS used a fixed value for "gains". Thanks, I stand corrected: Viper had degradation modes, different in details but principally similar to Airbus FCS laws.

We did not worry about a myriad of alpha stuffNeither need Airbus pilots as long as they don't bust the lift limit.

Both limited the jet to stall AoA ( roughly). ...on aeroplane supported by cropped delta of relatively low aspect ratio i.e. with far larger useful AoA span (per design and intended use) than moderately swept, high aspect ratio, supercritical, cruise optimized wing of 330.

Could still run outta energy in a steep climb and momentum would allow the jet to exceed the limts because the flight controls could not react quickly enough ( very hard for our jet, and even more so for the heavies, IMHO)It's hard to climb heavy steeply but if combat aircraft controls can not react quickly enough, what chances have the civil transport ones?

Otherwise, much of my views could be misunderstood.As someone who was using HUD in airliner for a while I agree it is quite useful but I don't think it would have saved the AF447.

not sure what 'vent' means hereTypo for "went".

it does appear that the designers forgot this very important 'trigonometry' and that a jet in a fully developed stall can and did, in fact ?'vent'? below 60kts (IAS).20/20 hindsight. No one has proven before that it can.

With hindsight the logic is faulty, but I don't see any need to alter the logic governing validity of AoA signals which might well bring on other problems we know nothing of. Instead I would propose a change of stall warning logic so that if triggered by a valid AoA signal it should stay latched on until it received another valid AoA signal that stall conditions were a thing of the past.Spot on. Instead of introducing WoW signal into stall warning logic and creating another possible point of failure, not completely dissimilar to one affecting Spanair 5022, this one could be done by simple software code change. However...

That would have avoided the confusion found in the AF447 cockpit for a minimal change to the aircraft systems...if there was confusion about everything else, at least actions on the stick show that CM2 firmly believed that stall warning can be resolved by pulling.

However, why WoW was 'abandoned' I do not knowIt was never there. If you already must have speed and mach input to calculate critical angle of attack, it makes sense to simplify it by just putting in a couple of lines of code that cut alpha readouts at speeds that are completely unsustainable.

but I cannot see why posters are going on about 'non-swivelling pitot tubes'I am just mocking the inability of some to understand pitot tubes reliably measure only total pressure resulting from airstream approximately parallel to aeroplane's longitudinal axis. Such a design has been with us since they have first been attached to aeroplane and everyone except a couple of PPRUNers finds it fine.

Surely we all understand why the IAS reading was invalid? Those who think IAS reading below 60 kt was really invalid - not.

In response to that, Airbus reduced the required pressure on the WoW sensorsI don't recall anything about this. What I remember is that post-Warsaw spoiler logic on 320 was changed inasmuch selecting reverse cracked open the spoilers thereby killing a bit of lift and compressing both struts. The rest remained unchanged and full deployment was still only available when both MLG WOWs detected landing. Way the Airbus spoilers designed, WOW signal is a must to prevent airborne activation of ground spoilers.

OG, I'm almost certain you're correct in that the <60kts AoA NCD flag has nothing to do with determining air/ground mode - it's purely an attempt to enforce the AoA vane manufacturer's specified limitation of minimum 60kts airspeed for valid data, and prevent junk data from being used in FCS calculations.Interesting... I'd like to hear more about about junk data when Airbus flies slower than 60 kt, I mean why is this problem not solved yet by introducing the alpha probe that can work reliably below 60 kt?

Basic airmanship and flying skills, ya think?Yes.

[DozyWannabe]

Spot on. Instead of introducing WoW signal into stall warning logic...

WoW is probably not part of "stall warning logic" outside of air vs. ground mode operation. The argument seems to be based on the misapprehension that the <60kts NCD flag was implemented instead of WoW to determine AoA vane validity, which is a fallacy. It is far more likely that both inputs are used.

I don't recall anything about this. What I remember is that post-Warsaw spoiler logic on 320...

I was going on the Wiki page, which stated:

As a result of the accident, Airbus Industrie changed the required compression value from 6.3 tons to just 2 tons per main landing gear.

[gums]

Me thinks that Cland and Gums are on the same page for most of the philosophy here.

I can also appreciate the enginnering inputs from Doze, but saw many well-intentioned "engineers" suggest inputs to our FBW system and other stuff that we operators threw out. They were mainly "protections" and such, including a FCS "pull up" if Hal thot we were gonna auger if we exceeded pitch and altitude and such trying to hit our target. (99.9% of we pilots threw the notion out. There comes a time when "pressing" just a little bit makes the difference, and ya take your chances.) So we opted for a big flashing "X" in the HUD when HAL thot we were pressing too hard. Ignore it at your peril, and I have HUD film of a friend that ignored and paid the the price.

The mentality ( attn Doze) that the system acted like it was designed has some problems if the aircrews don't fully understand the "system". And as I have oft-repeated, the 'bus reversions modes are complicated and should be more straightforward. The basic FCS system should be basic enough in the reversion modes to HELP the pilot and not confuse the pilot about what protection is still here and what isn't. And as Cland and I seem to agree, there's a huge role for basic airmanship.

@ Cland:

- AoA is, indeed, a factor at mach approaching "critical" mach and such. The airfoils nowadays are much smoother than the old ones I flew. Only flew three that had significant warnings you were gonna get into trouble. And I admit that I flew airfoils that could exceed the mach ( M=1.0) without losing control of the jet.

- Aspect ratio and the airfoil shape of four of the jets I flew definitely made thos jets more tolerant of doing strange things when flying at "the limit: as the AF447 were doing when things went south.

- Running outta "E" is still a player, and the Russian crash might show that when the crew did a go-around to an extreme pitch attitude. But that's another thread.

It took us some very extreme pitch attitude/power combinations to run outta "E", and then exceed the aero surfaces' capabilities to keep us under control. I just can't see such with the heavies without serious airmanship problems.

I appreciate the oppo to add to this discussion, and have learned a lot from the heavy pilots here.

[DozyWannabe]

The mentality ( attn Doze) that the system acted like it was designed has some problems if the aircrews don't fully understand the "system".

The "system" makes the A330 behave like any other aircraft. If you keep pulling up and let the speed decay, you will stall. F/O Bonin was a sailplane pilot of considerable skill - at some fundamental level, he understood this. If some folk want to make an argument that he was pulling up in the hope that Alpha Protection would keep him safe, they're welcome to it. But that argument chafes against the fact that as a sailplane pilot, he had to understand that if the aircraft was stalling and the increased thrust didn't help, then he had to get that lift from somewhere.

But he never acknowledged that the aircraft was stalled, despite the warning blaring in his ear for more than a minute. The horror afflicting the piloting fraternity is that he had all these indications and yet continued to pull up - a response for which there is no logical explanation. This accident is as inexplicable as it is horrific - something inside him kept telling him to pull up in the face of all the data he was presented with. I suspect that psychologists will be tasked with trying to provide an explanation until long after I'm gone, but it's not a case of being confused by the systems, it's a case of a pilot - for reasons that we'll never understand - pulling up consistently in the face of a situation where the precise opposite action was required.

[gums]

Only problem I have with your "analysis", Doze is that the jet flies like all the rest.

That is true if all you want to do is have auto-trim corrected for pitch attitude, roll limiting to 30 deg or so, and so forth. Mission requirements, I guess, as you have pointed out to me and others about my personal mission/operational requirements. All I can say was the thing flew like everything I ever flew until at the edge of the envelope, and then it excelled.

I shall never understand the continued back stick, so I guess I have to wait until we meet in that hootch bar in the sky one day where all we pilots wind up. Still makes me cry.

I also understand that many heavy pilots have never flown their jets close to the performance envelope WRT mach, AoA and so forth. So not interpreting mach/overspeed indications versus incipient stall is not a surprise to me.

[bubbers44]

I also flew sail planes and enjoyed the feeling of silent flight but it,as Sully and I feel, it doesn't help you much flying airliners. He landed in the river because he knew how to fly and saved everybody and was a hero.

I would hope all of us have the piloting ability to do what he did. Button pushers would not have a chance in his condition.

Kind of sad, isn't it? This is the new generation of pilots sadly.

[bubbers44]

The new pilots should force themselves to make them as good as the old guys and not rely on automation if it all fails. We could do it, why can't you?

[Machinbird]

Originally Posted by Clandestino in response to Chris Scott
You suggest that A330 is sensitive beast that has to be treated gently. I say that it is exaggeration and you can throw her around hamfistedly at cruise altitude, in alternate law for 4 minutes with normal acceleration varying between +1.96 and -0.26G with end result being no worse than just utter mess in cabin and galleys. Originally Posted by Machinbird
Do that in roll direct and I suspect you will learn gentleness, and there might even be an additional mess in the cockpit.

Alternate1 and Alternate2 laws might work similarly in pitch, but they bear no resemblance in roll.What relevance it has to AF447? For Finnegan's sake it didn't crash in spiral dive or rapid roll to ocean but in upright stall! That's what happens when you try to pull the aeroplane where she just can't go perfomancewise.

This the relevance.
Bonin applied excessive control inputs that the aircraft would have tolerated had it been in Alt1 law, but since it was in Alt2b, a roll direct law, the sensitivity of the roll channel was far higher than he expected and he set up a roll oscillation that lasted 30 seconds. During this same 30 seconds, he inexplicably pulled up into a climb that used up virtually all the aircraft's energy reserve above stall speed. In my opinion, this roll oscillation fits the general definition of a PIO.

What most readers here do not seem to appreciate is that a PIO event will grab 100% of your attention while it is in progress. My only experience with PIO was in an early visual simulator and it was brief and without consequence. Nevertheless, it made a deep impression. The best analogy to it was like unexpectedly tripping and beginning to fall and looking around desperately for a handhold.

In effect, while piloting an aircraft, the aircraft is your body. Would you be able to execute a checklist or maintain a scan while your body is falling out of control? This type of 'emergency' will cause a tremendous flow of adrenalin in those without prior experience. Will you be able to pilot rationally immediately after such an event? This is my take on the cause of AF447's loss.

[A33Zab]

'WoW' is involved in the FWC stall warning logic but here it is called flight phase [IN FLIGHT = flight phases 5,6 & 7).

!But that is not the issue!

All 3 ADIRUs did send an AoA SSM NCD (No Computed Data) signal, for the FWC this means there was no valid AoA to compare against a threshold which depends on Mach, S/F and SB config.
(Max AoA threshold 16.3º in S/F Config FULL (ALTERNATE & DIRECT ) and a fixed 23º in NORMAL)

Actually this philosophy is identical to Boeing T7 only the values are different.

Now if you want the system to be changed the solution has to be found in the ADIRUs NCD state within ARINC specification.
(in AF447 the measured air speed was sometimes 0kt - and even negative q -, just setting a lower value or 0kt would not have solved the issue here.)

For accuracy of the vane:
The AoA vane accuracy is shopchecked in a laminar air flow windtunnel at 100kt.
At an offset of 3º(+/- 0.2º) from original value the vane should return to original position within 0.25º with a max. overshoot of 0.5º to pass this accuracy check.

[Owain Glyndwr]

@ Clandestino, Dozy

I don't recall anything about this. What I remember is that post-Warsaw spoiler logic on 320 was changed inasmuch selecting reverse cracked open the spoilers thereby killing a bit of lift and compressing both struts.

That agrees with my understanding of information obtained from the horse's mouth.
The 'wiki' comment probably arises because the A320 oleo design was changed to reduce the breakout 'stiction', but that was done to improve the harsh taxy ride that occurred on some surfaces. As a byproduct it reduced the vertical force necessary to start the torque links moving from their fully extended position (used to signal WOW) but that was not its primary purpose.

A classic case of 2+2=4.5!

[Winnerhofer]

The forgotten report:

Suite Données Aux Recommandations De Sécurité

Hardly any of the BEA's recommandations have been implemented.
The report makes a scandalous read with the DGAC and EASA still passing the buck.

[Peter H]

While considering system updates, how about the generation of a message something like:
pitot redundancy lost, review UAS procedures
before the autopilot dropped out.

I don't know how long before autopilot drop-out it could/would have been generated, but it would surely have reduced the startle factor.

My guess would be 10s of seconds from the rejection of the unfrozen pitot to the divergence in readings from the other two pitots leading to the declaration of UAS.

[DozyWannabe]

My guess would be 10s of seconds from the rejection of the unfrozen pitot to the divergence in readings from the other two pitots leading to the declaration of UAS.

Nope, it's pretty much instantaneous in human terms. The software is checking and cross-checking several times a second - you'd be talking about maybe 2 or 3 seconds from initial icing-over to the systems detecting an extended discrepancy and disconnecting AP.

In the case of AF447 the point is somewhat moot, as the PNF is supposed to monitor ECAM and action things accordingly. The PF started pulling up almost immediately the AP disconnected without first assessing the situation. The cause of AP disconnect was right there in the ECAM - but it seems that the PF's instincts overruled his reason and training, and neither the PNF or the Captain could break through his panic.

[Peter H]

Peter H
My guess would be 10s of seconds from the rejection of the unfrozen pitot to the divergence in readings from the other two pitots leading to the declaration of UAS.

DozyWannabe
Nope, it's pretty much instantaneous in human terms. The software is checking and cross-checking several times a second - you'd be talking about maybe 2 or 3 seconds from initial icing-over to the systems detecting an extended discrepancy and disconnecting AP.

Sorry, surely there were two events involved, and it's the time between them we are discussing.

IIRC The first extended discrepancy resulted in the mis-diagnosis of the working pitot as faulty. The second extended discrepancy occurred when one of the two frozen pitots started to unfreeze.

[DozyWannabe]

IIRC The first extended discrepancy resulted in the mis-diagnosis of the working pitot as faulty. The second extended discrepancy occurred when one of the two frozen pitots started to unfreeze.

Where are you getting that information from? My understanding was that all three pitot tubes froze almost simultaneously in a matter of seconds, thus making the time discrepancy somewhat irrelevant.

The point I was trying to make was that the instinctive reactions of the PF were not in response to any specific warning, but a panic reaction to the situation - attitude, turbulence and aural warnings.

[HazelNuts39]

Peter H;

You mean these two events?

1.16.3 Analysis of functioning of systems
1.16.3.1 Analysis of the initial sequence
Analysis of the FDR parameters and of the data contained in the two FMGECs’ nonvolatile
memories showed that:
ˆˆ The ADR 2 speed fell between 2 h 10 min 03.5 et 2 h 10 min 05;
ˆˆ the ADR 1speed fell for less than one second from 2 h 10 min 04 s to 2 h 10 min 05,
causing:
yy the disconnection of the autopilot,
yy the triggering of “PITOT PROBE” monitoring in the FCPC causing the transition
to alternate 2B law;

[Winnerhofer]

I agree that the roll oscillation was a PIO.
I'm not so convinced that there is a big difference between alt 1a and 1b, though there certainly is some.
In alt 1a the airplane would have been inherently more roll stable and probably would not have required much correction to begin with but given a 3/4 stick input in reaction to an 8° bank angle (exccessive), a PIO is still possible

[hikoushi]

Personal opinion in response to the earlier post: in considering the possibility that the PF was so preoccupied with a roll PIO that he basically "tunnel-visioned" out his pitch situation (due to ALTN 2 law providing almost double the roll rates of ALTN 1 or normal law), his last comments on the CVR contradict that scenario. He states that he had the stick back the entire time, implying that that is exactly what he intended to do. Why he chose to do that we will never know. Whether his training or experience did not provide him the tools he needed, whether the design itself bears some blame, or whether he simply did not meet the challenge on that day.

One way or another, he used the best judgment he could manage at the time, and it steered him wrong. "But for the grace of God", any of us could be there in his place.

[mm43]

@A33Zab!But that is not the issue!Thanks for elaborating on the dependencies.
Owain Glyndwr in Thread No.8 - Page 47 (http://www.pprune.org/tech-log/482356-af-447-thread-no-8-a-47.html#post7210152) -
.... one doesn't calculate AoA from CL but CL from AoA. CL doesn't figure directly in assessment of whether the aircraft is near stall or not - that is a simple function of AoA and Mach Number. If AoA is measured (as it is) then at low Mach that is enough to determine stall margin. When at higher Mach the boundary needs to be adjusted (which is why a simple AoA gauge cannot function as a stall warning when airspeed information is lost), but even then it would be possible to work with a default value which, even if it did not prevent "stall", would serve to avoid the sort of shambles that we see in AF447. ... described it similarly.

I've said it before, and I'll say it again - this PF never registered the Law change and its implications, neither in pitch or roll attitudes. Startled by the A/P disconnect and oblivious to anything else but dealing with the roll, he pulled back in the belief that AoA Prot would keep the aircraft in a stable longitudinal configuration. Revealing a deadly lack of knowledge in the FCS dependencies. Nothing changed over the next 4 minutes.

[BOAC]

It seems Dozy and Lonewolf are intent on dragging the 447 AoA issue into the Asiana thread so I will bounce it back here No, no, no - the <60kts AoA NCD limitation was nothing to do with an air/ground assumption. It was simply an encoding of the vane manufacturer's specifications - i.e. that the vane could not provide reliable data without 60kts of forward airspeed.

My highlighting to show the flawed thinking which I assume existed at AB too.

[HazelNuts39]

Airspeed is derived from the differential between pitot and static pressures. Is there any airplane that derives it from static pressure alone?

Hindsight wisdom ...

[rudderrudderrat]

Hi HazelNuts39,
Is there any airplane that derives it from static pressure alone?
All aircraft have a device which measures rate of change of static pressure - it's called the Vertical Speed Indicator.
AF 447 had in excess of 10,000 ft per minute displayed (about 100 kts) - more than enough for the "60kt AoA vanes" to sense I would suggest.

[Owain Glyndwr]

BOAC

My highlighting to show the flawed thinking which I assume existed at AB too.


With all due respect to Dozy, using his terminology to infer AB's thought processes is rather a big assumption :D

[HazelNuts39]

rudderrudderrat,

please name an airplane that uses vertical speed as a substitute for airspeed

[BOAC]

rudderrudderrat- HN39 seems to have gone 'adrift' somewhere and I am totally confused by his reference to static pressures! Do we know which post he was referring to?

Owain - 'assume existed ' - why else pick '60kts of forward speed'?

On both counts we seem to be risking a trip to Oozlum land!

[Owain Glyndwr]

BOAC

My point, not very clearly expressed, was really that 'forward speed' is an expression of Dozy's; I am sure that AB's engineers knew and know very well that it is the total air speed over the vanes that drives them not forward speed alone. [and so does Dozy I suspect, it was probably just loose wording]

In normal flight the two speeds are identical to all intents and purposes, although not of course when descending at around 10000 fpm (100 kts) and a forward speed which is also around 100 kts. Which is where the confusion between HN39 and rrr starts :ugh:

Not worth flogging!

[HazelNuts39]

Furthermore ...

10,000 ft/minute TAS at FL 350 ISA + 11°C is about 54 kt CAS

[gums]

Good to see some re-hash of a few things, especially the AoA issues.

As far as the pilot actions go, all we know is what the pilot did. Until we all join him in that hootch bar in the sky to get his version of the story, we shall never know.

OG made a good point many threads ago, and recently referenced. AoA "protections" depend upon mach bias once getting on up there WRT mach. Otherwise, the raw AoA is a very good indication of your state. Due to our mission requirements, and our relaxed static stability ( actually negative) until 0.95M, that bias was essential. Doze and I have talked about this and seem to agree that our implementation was necessary. So I return to the discarding of AoA once the dynamic pressure inputs to the FCS were deemed invalid. And BTW, on my emergency landing HUD tape you will note that all the displayed data went to zero when I reached 60 knots. Hmmmm. Of course, we were in "direct law" once we had WOW.

I have always been puzzled looking at the FCOM re: flight control laws, as it appears the system abandons many limits and such at the very first reversion mode. Roll control is one biggie, as 'bird points out with possible PIO for the first 30 seconds or so. And then there's the AoA protection, and sensed dynamic pressure be damned. Too easy to see if the vanes are cranking out good data. Our system had the traditional vanes ( conical sensors with slots), but we also had a "hemispherical" probe that had holes drilled all over it. That probe had its own heater and provided differential pressures to the "air data convertor", which then provided inputs to the FCS and an output for display and to our weapon/nav systems.

It is too easy to retain roll control laws other than the 33 degree limit and such, and simply command zero roll rate if the pilot is not moving the stick left or right. just look at the Thunderbird solo pilot's routines and note that the sucker rolls inverted and then the jet just stops rolling with no wing rock. It was easy, as all you had to do was relax pressure. Since there is no completely "direct law" except for the elevator/THS, this implementation has always puzzled me.

I wonder if the original test pilots ever went thru all the reversion laws where they could "fail" the air data or this data or...... I also wonder if they ever asked to fly in our little jet and see what we had using a similar test setup.

too long, but I had to get this off my chest.

[rudderrudderrat]

Hi HazelNuts39,

Furthermore ...
"Time 2 h 11 min 58 - The vertical speed is around -15,300 ft/min."
That's around 80 kts CAS vertically - is that enough for you?

[HazelNuts39]

Hi rrrrr,

I thought we were discussing the moment the captain entered the cockpit and the stall warning stopped, which was at 02:11:44.

The stall warning operated again two times before 02:11:58.

[rudderrudderrat]

Hi HazelNuts39,

2 h 11 min 45 End of “Stall, stall” warning + cricket.
2 h 11 min 53 SV : “Stall, stall” + incomplete cricket.
2 h 11 min 55 SV : “Stall, stall” + incomplete cricket.

If you had just walked onto the flight deck and heard a continuous stall warning and observed the other flight information - I bet you would have diagnosed a stall.

[DozyWannabe]

My point, not very clearly expressed, was really that 'forward speed' is an expression of Dozy's; I am sure that AB's engineers knew and know very well that it is the total air speed over the vanes that drives them not forward speed alone. [and so does Dozy I suspect, it was probably just loose wording]

Correct - a poor choice of words on my part. I'm a software guy, not an aero guy. My apologies.

The point I was trying to make stands, however. Whether you're building a system of an electro-mechanical, analogue electronic or digital electronic nature, excluding bad data is paramount, because you can always plan a system that will work predictably with an input missing or invalid, but if you allow bad data in, you'll get bad data - and feedback - out (GIGO principle).

@rudderrudderrat:

I said in this thread, and the other, that:

I'd be very interested in seeing how all currently operating commercial airliners' sensory, control and warning systems behave when subjected to a flight profile that extreme - the problem is that no simulator can accurately replicate the conditions, and no test pilot in his right mind would risk flying that profile for real!

Because while it's all very well to hypothesise that the Captain might have diagnosed a stall earlier if the warning had still been sounding consistently, the fact is that we don't know how the systems on other aircraft behave when the aircraft is taken so far outside the expected flight envelope. To focus on that disregards the fact that the stall warning had been sounding consistently for around a minute without being acknowledged or acted upon by either of the flight crew present at the time. It also disregards the fact that the Captain was presented with unstable pitch tending towards nose-up, a rapidly unwinding altimeter and unreliable speed indications - would not these factors alone be enough to deduce a stall?

[Pugilistic Animus]

Pilots have overridden stick shakers and pushers before also

[A33Zab]

@RRR:



Furthermore ...
"Time 2 h 11 min 58 - The vertical speed is around
-15,300 ft/min."
That's around 80 kts CAS vertically - is that enough for
you?


Cool,
Now the system has 'valid' V/S and 'valid' AoA.
Could it calculate a valid forward speed? FPA?

At that time the V/S indication was degraded, in excess of 10.000 ft/min the V/S is ADR only [amber boxed digital V/S display] i.s.o ADR + IR.

[rudderrudderrat]

Hi DW,
but if you allow bad data in, you'll get bad data - and feedback - out (GIGO principle).
If someone could please explain how an A330 could ever have a CAS<60kts (at 1 g) whilst airborne - then I'll give up on this point.
If you are feeding "bad data" (intermittent / silent stall warning) onto the flight deck - then you'll probably get bad diagnosis out.

To focus on that disregards the fact that the stall warning had been sounding consistently for around a minute without being acknowledged or acted upon by either of the flight crew present at the time.
Please view http://www.youtube.com/watch?v=2QA65rDQ5y8
Audio clues tend to get filtered out by the brain during high work load. It is much better to use tactile (vibration / stick shaker).

It also disregards the fact that the Captain was presented with unstable pitch tending towards nose-up, a rapidly unwinding altimeter and unreliable speed indications - would not these factors alone be enough to deduce a stall?
Page 76 Interim report 3:
"In the absence of relevant information from the copilots, reading the information available on the screens (pitch attitude, roll, thrust, vertical speed, altitude, etc…) was not sufficient in itself for the Captain to become rapidly aware of the airplane’s situation. He did not then ask questions that could have helped him to understand the sequence of events.
The stall warning lasted 54 seconds continuously, during which time neither of the copilots made any reference to it. It is likely that the Captain heard this warning a few moments before coming back into the cockpit, but it is also likely that the multiple starts and stops added to the confusion and disturbed his diagnosis of the situation."

[CONF iture]

If you are feeding "bad data" (intermittent / silent stall warning) onto the flight deck - then you'll probably get bad diagnosis out.
It surely brought CONFUSION in the CPT's mind.
All AoA vanes were following a 100 knots airflow and they were all measuring an AoA greater than alpha stall. The STALL WARNING had no reason to quit.
The STALL WARNING logic is one of the contributory factors in this accident.

[Chris Scott]

Quote from Clandestino:
"I'll try different approach this time"

If this is a spot-the-difference test, Clandestino, I admit defeat. :bored:

As usual, you have quoted snippets of text - sometimes a phrase, rarely more than one sentence - and then dismissed them, in your instinctively adversarial style, without acknowledging their context in the writer's broader argument.

Before I respond to your latest rejection of such a policy, let me reproduce the key points of substance in our discussion about the possible merits of PFs routinely flying jet airliners, in what you neatly describe as friendly skies, with the AP disengaged, and also - where practicable - the A/THR and/or FD.

Clandestino (http://www.pprune.org/tech-log/511119-af-447-thread-no-11-a-40.html#post8156336):
"Again: issue with AF447 is not the pilot unable to handfly the aeroplane; it was pilot unable to understand the situation, implication of his actions and pretty precisely handflying just the wrong way, while his assisting pilot was, unfortunately, as lost as him. Nothing of it can be prevented by practising eye-to-hand coordination in friendly skies."

Me (http://www.pprune.org/tech-log/511119-af-447-thread-no-11-a-43.html#post8160812):
"I could not disagree more. All that needed to be done in AF447 was to keep the wings level, and MAINTAIN a suitable pitch attitude and thrust for high-altitude cruise. If you are accustomed to monitoring and understanding your a/c in all flight phases, you may learn ball-park figures even without ever disengaging the AP. But there are at least two snags to that as a policy.
"Firstly, you will not learn the very gentleness of any corrections that need to be made on the side-stick if you unexpectedly find yourself without the AP at high altitude. (Rather like driving a car at over 200 kph.) Secondly, human nature means that hands-on practice concentrates the mind in a way that mere observation does not."

The most recent reply from Clandestino (http://www.pprune.org/tech-log/511119-af-447-thread-no-11-a-43.html#post8162422):
(1) "Yes but this is all very well when you either know what happened or maintain presence of mind not to do harm when you are not sure what exactly you should be doing."
(2) "You suggest that A330 is sensitive beast that has to be treated gently. I say that it is exaggeration and you can throw her around hamfistedly at cruise altitude, in alternate law for 4 minutes with normal acceleration varying between +1.96 and -0.26G with end result being no worse than just utter mess in cabin and galleys."
(3) "Why are we not discussing some other LOCs like Birgenair? 20 000 hrs could not prepare the skipper for simple recognition that rejecting the takeoff when airspeed is not working is a must or just to crosscheck the three ASIs. Or close call at EHAM where the guy who taught others how to perform V1 cut just couldn't make it properly when it happened for real? That's what AF447 is about: the crew that just couldn't perform when it needed to."

Re (1), you have identified the very point I've been making: the PF needs to know how to avoid doing serious harm to the flight profile, and unnecessarily exploring the limits of the flight envelope.

Re (2), I am saying that, to maintain a safe and sensible flight profile at cruise altitude, you have to handle any large jet with kid gloves. What you may have to do to recover from an unusual attitude is another matter. The fact that airliners are stressed in extremis to about +3.75G and -1.5G is nice to know, but irrelevant to normal operations. The AF447 L.O.C. started with an a/c in normal, stable cruise-flight; albeit in routine, moderate turbulence. Notwithstanding Machinbird's and my own previously-stated reservations about the Airbus FBW downgrade combination of load-factor control in pitch with stick-to-aileron for roll, the only way to develop a scan and stick-dexterity that includes more than one parameter is to practise it regularly.

Regular hand-flying practice reinforces the understanding that in level cruise-flight, regardless of turbulence or windshear, any pitch attitude more than 2 or 3 degrees above or below the norm is unsustainable unless you want to climb or descend. Recovery from any startle factor would be quicker if the PF is confidently familiar with the sort of picture that needs to be maintained or restored on his attitude indicator, and how to achieve it. The same applies to thrust.

Re (3), this discussion clearly reads across to other types, many of which might be more of a handful at the beginning of a similar UAS event than the short-body A330 in Alternate 2B, with its advantage of retaining load-factor control in pitch. The two events you mention were on T/O, presumably involving the requirement for instant decision and rapid action? That did not apply in AF447 - quite the contrary. Excessive reliance on automation may well be eroding the basic instrument-flying skills that my generation, and our forebears, took for granted.

[HazelNuts39]

It is much better to use tactile (vibration / stick shaker).How about the airplane shaking so badly that the PNF couldn't hold a handset?

From the judicial expert's final report:

7.4.3.1.2 BUFFET ONSET ET DETERRENT BUFFET
Le Buffet Onset est un état transitoire qui n'a pu être identifié lors de la décélération a lktlsec, il a
été perçu lors d'une prise d'assiette franche vers 12°. Il consiste en une légère vibration
aérodynamique de basse fréquence (environ 4 à 5 Hz).
Le Buffet Deterreni est un phénomène totalement inconnu pour un pilote de ligne, seuls les pilotes
d'essai l'ont rencontré.
La dimension "Deterrent" c'est a dire Effrayant, Dissuadant est liée au Mach, cette dimension
diminue fortement dès que le Mach diminue.
Le Buffet Deterrent que nous avons subi est un phénomène impressionnant qui ne s'apparente pas
totalement à de la turbulence, il s'agit plutôt d'une vibration turbulente (passage à vitesse élevée sur
les bandes de ralentissement à l'approche d'un péage routier par exemple)
Le phénomène a été mesuré au centre de gravité et au siège pilote, il a été également évalué à la
partie arrière de la cabine.
L'effet 'Effrayant, Dissuadant" est très net au poste de pilotage, nettement moins au centre de la
cabine et important à l'arrière de la cabine.
L'intensité du phénomène est liée au mach d'une part et au taux de décélération (ici lktlsec). Les
valeurs étant différentes pour le vol AF447, il est probable qu'il y ait eu une diminution sensible et
rapide des effets, ce qui explique que l'équipage technique n'en ait pas fait état et que l'équipage
commercial n'ait pas appelé le cockpit à ce sujet.

GOOGLE translation (corrected to the best of my ability):

7.4.3.1.2 BUFFET ONSET AND DETERRENT BUFFET
Buffet Onset is a transient state that could not be identified during the deceleration at 1 kt/sec, it was perceived when taking the pitch attitude to 12 °. It consists of a slight aerodynamic vibration at low frequency (about 4 to 5 Hz).
The Deterrent Buffet is a totally unknown phenomenon for an airline pilot, only the testpilots have encountered it.
The dimension "Deterrent" that is to say Scary, Dissuading is related to Mach, this dimension strongly decreases when the Mach decreases.
The Deterrent Buffet we have suffered is an impressive phenomenon that is totally unlike turbulence, it is rather a turbulent vibration (moving at high speed over the 'deceleration strips' when approaching a toll road, for example).
The phenomenon has been measured at the center of gravity and the pilot seat, it was also assessed in the rear part of the cabin.
The effect "Scary, Dissuading" is very clear in the cockpit, much less in the center of the cabin and important in the rear part of the cabin.
The intensity of the phenomenon is related to Mach on one hand and the deceleration rate (here 1 kt/sec). Since the values ​​are different for flight AF447, it is likely that there was a significant and rapid decrease of the effects, which explains that the technical crew did not mention it and the cabin crew did not call the cockpit about it.http://i.imgur.com/enqIXyT.jpg?1

[Chris Scott]

Hi HN39,

Is there any chance you could improve the definition of that chart, please?

In the translation of the judicial report, I suggest that "important" may mean "considerable", or "significant", but one can see how easily any tranlation of empirical expressions can be misleading...

"l'approche d'un péage routier" means "the approach to a toll plaza" (i.e., at the end of a toll road).

In the very last sentence, my interpretation in English is slightly different from yours, as follows:
"The values being different from flight AF447, it is probable that there would have been a noticeable and rapid reduction of the effects..."

Now, can you confirm that the chart is from a post-accident flight test? In which case, was it considered that the "deterrent buffet" experienced on the test flight was LESS severe than on AF447, or MORE severe?

[HazelNuts39]

Hi Chris,

Thanks for your refinements of my translation. On many french 'peages' you pass a toll station at entry where you take a ticket, and again at the end where you pay the toll. The 'strips' are also present on lesser roads to force drivers to slow down before dangerous sections.

I reduced the size of the graphic only slightly, the resolution of the original is hardly better. The grid is 1 sec by 0.2 g, the scale markings on the left are from 1.0 to 1.4 g. The upper trace is for the pilot seat, the middle one near the center of gravity and the lower one in the rear of the cabin.

Yes, the judiciary experts participated in a test flight of an A340, an A330 rated pilot in the left seat and the Airbus pilot in the right seat. The testflight was preceded by a simulator session and the objectives were to evaluate:
-- experience "Deterrent Buffet"
-- for the three 'expert' pilots to appreciate manual piloting in normal, alternate and direct law at low and high altitude
-- apply the procedures for "IAS Douteuse" and "Stall Warning" at high altitude.

As to the test flight buffet being LESS or MORE severe as AF447 I leave the interpretation of the French text to you. In the "Commentaire d'experts" at the end they write:
"Le ressenti du deterrent buffet varie en cabine selon le positionnement des passagers. On ne peut pas affirmer qu'a l'approche du decrochage du vol AF 447, les conditions de vitesse et de taux de prise d'incidence aient genere de facon similaire les sensations du deterrent buffet. Celles-ci n'apparaissent pas de facon evidentes sur le FDR".

[Owain Glyndwr]

Hi Chris

I see I crossed with HN39 in cyberspace, but still :-

Now, can you confirm that the chart is from a post-accident flight test? In which case, was it considered that the "deterrent buffet" experienced on the test flight was LESS severe than on AF447, or MORE severe? I don't think you are going to do any better than section 1.16.4.2 of the final report. That says AI did special post-accident tests at as near as possible to the accident conditions and the test pilots established the AoA at which buffet reached deterrent levels.

If that chart is the result of those tests, as it presumably is, then it shows values appropriate to AF447, neither much more nor much less.

[OK465]

...the judiciary experts participated in a test flight of an A340...

Why a 340? Or maybe better put why not a 330?

[HazelNuts39]

Why a 340? Presumably because Airbus had one available and it is aerodynamically and systems-wise similar to an A330. One doesn't want to fool around in deterrent buffet in an airplane that is being readied for delivery to a customer.

[awblain]

While I'd agree that the A340 and A330 are - intentionally - very similar, this buffet appears to shake the cockpit much more than the cabin, yet is presumably excited by the air over the wings as the flow starts to change, rather than by the air over the forward fuselage.

As a result, the number and shape of the engines, affecting the airflow around the wing near the engines and the elastic and inertial properties of the wings, might be a relevant thing to look at. The weight distribution in the forward fuselage might matter too for how the cockpit wags around.

Presumably the test pilots were confident that the A340 results would apply to the A330, and convinced the investigators and the magistrates. Perhaps at 1-10Hz the differences are small - that certainly seems to be more of a shake than a bend.

If it's their own test A340, then it might also be safer to do this extreme test on board a very familiar aircraft.

[Winnerhofer]

Hazelnuts39 : votre thèse sur le buffeting me laisse perplexe.
So are you stating that the buffeting standard applied to all Airbus models is based on the A340?

[Bpalmer]

>The experts are surprised that the auto trim doesn't stop trimming the plane up once alpha prot is reached, as it is the case in ALT1.<
That functionality only exists in Normal law.
In Alternate law, (if airspeed is available) the protections will provide Low Speed Stability, which is essentially direct law pitch (pitch trim stops, the airplane's natural tendencey to pitch down if faster than the trimmed speed).
If there is no valid airspeed, then that can't work, and you're left with g-load demand with no bottom end.

[OK465]

The Airbus widebody family of flight test aircraft, the A380, A330 and the all-new A350 XWB, took off from Toulouse today flying together for the first time before continuing on separate flight test missions.

This is dated 20 Sept, 2013.

A350 XWB joins the A330 and A380 for an Airbus ?Xtra-widebody? family flight*| Airbus News & Events (http://www.airbus.com/newsevents/news-events-single/detail/a350-xwb-joins-the-a330-and-a380-for-an-airbus-xtra-widebody-family-flight/)

[DozyWannabe]

If someone could please explain how an A330 could ever have a CAS<60kts (at 1 g) whilst airborne - then I'll give up on this point.
If you are feeding "bad data" (intermittent / silent stall warning) onto the flight deck - then you'll probably get bad diagnosis out.

I'm pretty confident that the NCD value was to keep the FCS computations predictable and consistent - the FWC probably didn't come into it. I don't think the impact on Stall Warning was considered - and I'd be surprised if it was considered on other types either.

Audio clues tend to get filtered out by the brain during high work load. It is much better to use tactile (vibration / stick shaker).

You'd think so, but the record doesn't bear this out - shakers and pushers have been ignored or dumped pretty regularly. Even if we confine the data set to accidents after the launch of the A320, there have been more ignored shaker warnings than there have been ignored aural "cricket" warnings.

The STALL WARNING logic is one of the contributory factors in this accident.

No argument there, but let's not beat about the bush - it's a comparatively small factor when looking at the incident as a whole. Also, as I said before - we don't know how stall warnings on other types would respond when so far outside the accepted flight envelope.

[rudderrudderrat]

Hi DozyWannabe,
Even if we confine the data set to accidents after the launch of the A320, there have been more ignored shaker warnings than there have been ignored aural "cricket" warnings.
If you have a look at the CVR transcript from page 23 onwards:
http://www.bea.aero/docspa/2009/f-cp090601.en/pdf/annexe.01.en.pdf you will see that the "C-chord" (Altitude Alert) was on continuously until impact. It was only interrupted by "cricket" "Stall Stall" and GPWS warnings (higher priority).

The crew didn't acknowledge the continuous "C chord" (which could have been easily cancelled).
Does that, plus all the ignored "Stall Stall" warnings not suggest to you that they never "heard" any of the audio warnings?

[DozyWannabe]

Does that, plus all the ignored "Stall Stall" warnings not suggest to you that they never "heard" any of the audio warnings?

Of course it raises the possibility, and I'm not debating that aural overloading is a potential hazard. However, from BEA548 through NWA6231, Birgenair 301 and West Caribbean 708 - to name just a few, there are a slew of fatal accidents where a tactile shaker (or pusher) was either ignored or dismissed by the crew. I'm with you - theoretically, buzzing the stick in your hand should get through where aural warnings can't, but experience shows that if the situation is confused enough, it doesn't make as much difference as one might think.

[CONF iture]

it's a comparatively small factor when looking at the incident as a whole
Small or big, it is one more hole to line up for the accident to take place.

we don't know how stall warnings on other types would respond when so far outside the accepted flight envelope
And ... ?

If there is no valid airspeed, then that can't work, and you're left with g-load demand with no bottom end.
Which is totally aberrant.
The auto trim goes almost to the max value when it should have quit at the same time the AP and A/THR have.

[Bpalmer]

If someone could please explain how an A330 could ever have a CAS<60kts (at 1 g) whilst airborne - then I'll give up on this point.
If you are feeding "bad data" (intermittent / silent stall warning) onto the flight deck - then you'll probably get bad diagnosis out.


At extremely high angles of attack (e.g., 45°) the air striking the pitot tubes and the static ports (located well below the midline of the fuselage) approach the same angle. Indeed, at one point (at least), the error reported on the ISIS showed that the static pressure exceeded pitot pressure!
Since CAS is a measure of the difference between these two pressures, the airspeed indication will be erroneously low.
This happened as the stall deepened and the angle of attach exceeded 45°. You can easily correlate the periods of reduction in angle of attack during the descent with the stall warning sounding periodically.

[Bpalmer]

The auto trim goes almost to the max value when it should have quit at the same time the AP and A/THR have.
It should have quit based on what? Your opinion?
In the absence of airspeed to switch the pitch mode to the Low Speed stability(i.e., Direct law -trim becomes manual only), the pitch mode remained in g-load demand. As the g-load reduced due to the increasing descent rate when the stall happened, the flight controls atttempted to bring the g-load back to the commanded value in the only means it had: more elevator. When the elevator is held at other than neutral, the stab trims, and so it went.

[rudderrudderrat]

Hi Bpalmer,
Nice description of IAS.
CAS is IAS corrected for instrument and position /installation errors.

[Armchair]

Hi, Everyone. Been reading these 11 threads from the beginning of this tragedy. Finally registered in order to ask what (hopefully) is not taken as a stupid question: is the CVR audio purely mic driven or are the C-chord, stall cricket and other audio alerts wired directly into the box? I doubt they are wired in, but if it were the case and the electronics were going haywire, it could explain why the crew never acknowledged the alarms (requiring speaker failure) while still existing on the CVR... Speaking of that, I do still wonder why the BEA neglected to include the "one hour sleep" reference and if there is more to the "privacy" excuses re CVR, legit or not.

[Winnerhofer]

If only the BEA would release the DCVRs in their entirety but they didn't having bowed to pressures by Unions.
I've put forward what indeed really happened in terms of human interaction on the AF447 flightdeck only to see my posts deleted by dark forces.
It's difficult to fathom for for those who haven't lived in France to understand the strained relations the Unions have had with AF as well as overly-politicised appointements that are rewards for the party faithful.
A much better read than the BEA's report is the Judicial Experts' report.
A new panel has been selected for a 2nd Judicial Experts' report at Airbus' behest even though they were 98% happy with the 1st but now want to be 100% blameless with the 2nd report as it lays the foundation for the trial proper.
No trial can go ahead before the 2nd Judicial Experts' report is completed but the road will be a long one and the Investigating Magistratre is set to retire at year's end which will again slow the wheels of justice.
French trials for aviation accidents are endless.
For example, a chopper crash in in 2004 with 5 victims will reach trial in Jan 2014 after 10 years! Crash de l'hélicoptère d'Héli Air: jugement le 30 janvier | Nice | monacomatin.com (http://www.monacomatin.mc/nice/crash-de-lhelicoptere-dheli-air-jugement-le-30-janvier.1520539.html) but wait then there are appeals and appeals...

[DozyWannabe]

... but if it were the case and the electronics were going haywire, it could explain why the crew never acknowledged the alarms (requiring speaker failure) ...

I'm pretty sure (though not 100% certain) it's all mic-driven, with "hot mics" at the crew positions and one or more "cockpit area" mics. What I am sure of is that the electronics were not "going haywire", they behaved as designed throughout the sequence. The only technical issue was the icing over of the pitot tubes, and the ice melted, clearing the pitot tubes during the zoom climb.

Speaking of that, I do still wonder why the BEA neglected to include the "one hour sleep" reference and if there is more to the "privacy" excuses re CVR, legit or not.

CVR transcripts as appendices to investigative reports are routinely redacted. Redaction of material considered irrelevant to the actual conduct of the flight is commonplace, and the discussion of rest was part of a personal (i.e. non-essential) conversation. The talk of "one hour" rest did not, as I recall, refer to the total amount of rest the previous night, but to a different period of time. Another thing you'll routinely see redacted are expletives and unintelligible words.

@Winnerhofer - you do talk a lot of rubbish sometimes. First you claim the wife of the PF was present on the flight deck (for which there is no evidence), and now you're saying Airbus are aiming for a "blameless" report when there is no evidence to suggest that. What is suspect about the so-called "Judicial Experts" report is that it was performed at the behest of the SNPL.

[jcjeant]

What is suspect about the so-called "Judicial Experts" report is that it was performed at the behest of the SNPLOnce again I must remember you (it's tiring at the end to make the parrot) that this expertise is not related in any way to any union .. but it was requested by the judge who heard the case .. as French law requires to do in such cases
Those experts are independent and come from a pool of the judicial instances (and so .. are not "so-called" judicial expert :rolleyes: )
They are as independent as those of BEA Experts :ok:
I hope this help :)

[Clandestino]

Me thinks that Cland and Gums are on the same page for most of the philosophy here.Yes, when it comes to technical part: we agree that HUDs and alpha displays are useful. No, regarding the human factors involved in AF447; I do not think HUD would make a difference. From technical standpoint, crew had everything they needed to deal with the situation successfully, they were just so shocked they couldn't use any of it.

And as I have oft-repeated, the 'bus reversions modes are complicated and should be more straightforward.Some might find description complicated but I find their operation very simple; just keep on flying as you were. It's not as if Airbus pilots use their protections daily.

AoA is, indeed, a factor at mach approaching "critical" mach and such. The airfoils nowadays are much smoother than the old ones I flew.Not just that: even wings designed for similar missions have widely diverging characteristics near the envelope edge. 737NG has mach trim, 320 doesn't. 330 radically changes critical alpha at high mach, 320 not so. What impact does it have on line pilots? None whatsoever. Know your limitations and procedures. If you are going too fast, slow down but not so radically you approach stall. If your alpha is to high, reduce it in reasonable and timely manner. Fly the attitude. I guarantee you it works on Stinson Trimotor, F-16 and 330 despite never having flown any of them.

We could do it, why can't you?Only in your imagination. In real world there were quite a few pilots losing control of their steam gauged aeroplanes and there are many modern pilots who successfully returned their glass cockpit wonders to earth after major technical malfunctions. Implying all pilots today (except quinquagenarian and higher) can't fly in critical situations flies in the face of safety records and is off-scale hypocritical.

While considering system updates, how about the generation of a message something like:
pitot redundancy lost, review UAS proceduresDesign such a system and you'll get rich beyond your wildest dreams.

Point with unreliable data is that they cannot be machine-recognized and no amount of computing power can help it. Have a look at Aeroperu accident; the kind of false alerts they got and tried to resolve in vain.

In the case of AF447 the point is somewhat moot, as the PNF is supposed to monitor ECAM and action things accordingly. It's even more moot considering one of the few coherent and rational items on CVR is recognition that speed display has gone bad - from both sides of cockpit.

One way or another, he used the best judgment he could manage at the time, and it steered him wrong. "But for the grace of God", any of us could be there in his place.True! Especially bearing in mind it's one thing to consider the pitot blockade, reconfiguration laws, aeroplane energy state, warnings etc. sitting comfortably in front of the computer screen, quite another having it all thrown at you over the middle of Atlantic at 4 a.m.

I am saying that, to maintain a safe and sensible flight profile at cruise altitude, you have to handle any large jet with kid gloves.I was trying to point out discretely that you haven't read the part of AF447 report dealing with TAM incident which puts "kid gloves approach" straight into "old wives tales" category - something that has some basis in reality but through misunderstanding and misinterpretation diverges rapidly and significantly from it.

Regular hand-flying practice reinforces the understanding that in level cruise-flight, regardless of turbulence or windshear, any pitch attitude more than 2 or 3 degrees above or below the norm is unsustainable unless you want to climb or descend.Regular use of autopilot does not absolve the pilot from obligation to check instruments. Idea that you need to handfly to know your typical flight-phase-related attitude is so unrealistic it... sorry, I can't find the phrase in English.

this discussion clearly reads across to other types, many of which might be more of a handful at the beginning of a similar UAS event than the short-body A330 in Alternate 2B, with its advantage of retaining load-factor control in pitchThis discussion needed not read across to other types if folks would only read the effing report and see that there were many similar incidents on 330/40 fleet, with every single one having far, far better outcome, therefore making long, elaborate and usually just plainly wrong discussions on FCS degradation laws unnecessary - if one's intent is to get to what made the difference in AF447 case.

While I'd agree that the A340 and A330 are - intentionally - very similar, this buffet appears to shake the cockpit much more than the cabin, yet is presumably excited by the air over the wings as the flow starts to change, rather than by the air over the forward fuselage.
Airbus did effing fly 330 to check buffet levels, both waaay before AF447 and after. 340 test was not part of official accident investigation and only confirmed that 330 and 340 have very similar approach to stall characteristics.

[Winnerhofer]

@ Dozy : jcjeant is absolutely right.
Only the Juge d'Instruction has the power to demand un rapport des Experts Judiciares.
The judge ordered this because she would need 3 months of A332 sim to understand the intricacies so the Experts Judiciares is an ham-fisted shortcut.
What would really throw a spanner in the legal works is mounting pressure to get rid of the status of the Juge d'Instruction altogether and move an to an adversarial system by ditching the inquistorial one.
This was done in Italy in 1988.
Just for the record, over the last 30 years, the power of Juge d'Instruction has been eroded by endless reform so much so that it really be hightime to axe it.
Its survival was further damaged by the Outtreau Affair which was led by an incompetent Juge d'Instruction.

[Lonewolf_50]

BOAC: I said nothing about the WoW - ground issue, only a passing comment on a clipping/filtering of the AoA signal, and was making a different point, when Dozy chose to take a point out of context and run with it. Since he didn't bother to read the post for comprehension, I thank you for pointing out that step toward Oozlum land.
Gretchenfrage's point on the culture and cultural assumptions behind aircraft and system design are a point well made.

Look at the cultural assumption made in designing the A330, and the presupposition that no pilots will have the aircraft at 60 knots at altitude. (AoA signal clipped/filtered ... ) (LW_note in retrospect: Maybe I should have phrased that "henceAoA signal clipped/filtered) That pilots won't stall a passenger liner at 35,000 feet.

This cultural assumption leads to how the testing and training are developed and funded. 228 dead ... no Koreans at the helm.
The Korean bash that I responded to was what the point of my post was, not AoA/WoW interface or any of that.

Again, thanks for pointing out how far afield things can go when not correctly understood ... gee, I wonder if that isn't a metaphor for AF447 and the concept of pitch and power ... :p

@ Winnerhofer, axe grinding noted. :cool: Did your ancestors fight in the Schlacht im Teutoburger Wald. :}:cool::8

@ Piltdown Man:
Therefore the joint objective of all airlines should be to bring the teams skills of playing video games to the airline world.
Isn't that already happening?
I'll will suggest that the winning Korean team had a very flat command gradient.
You are probably right.
And if this attribute of a successful team can taken on board so to speak, then they'll be in a position to win in flying operations.
Indeed. There is one small problem with the template: in these RTS games, or MOBA games, everyone on the team is involved and has their attention keyed and alert states at a high level. Quite the opposite of automation dependent pilots with lowered alert states. :suspect:

EDIT to add:

Automation dependence and cockpit gradient problems are not unique to Korean operations, which is why I dragged AF447 into the conversation there about Asiana. I apologize if that wasn't clear.

[OK465]

340 test was not part of official accident investigation and only confirmed that 330 and 340 have very similar approach to stall characteristics.

(my bold)

Clandestino,

Why was that unofficial confirmation of 340 similarity even necessary?

What type of info would be derived from this consumption of jet fuel that would be useful with respect specifically to the 330....that couldn't be derived from a 330 test?

(Apologies for the short post.)

[HazelNuts39]

I fail to understand the bickering about insignificant details. The flight we are discussing was not a test flight and is not part of the investigation. The comité d'experts (two A330 captains, one B777 captain, one aeronautical engineer, and one maintenance expert, all five pilots) asked for a demonstration and hands-on experience of some flight characteristics that are common to the A330/A340 family of aircraft. They were happy with what they got, and described their observations with the usual caveats.

As to whether the buffet they experienced was more severe or less severe than that occurring during AF 447, one only has to compare the accelerations recorded near the center of gravity on the DFDR in the BEA report with those recorded in the demonstration flight.

If Airbus carried out additional test flights in an area that hadn't been explored earlier, that would have been with a minimum flight crew wearing orange suits and parachutes, without judicial observers at the controls or even on board.

[OK465]

I fail to understand the bickering about insignificant details.

The intensity of the phenomenon is related to Mach on one hand and the deceleration rate (here 1 kt/sec). Since the values ​​are different for flight AF447, it is likely that there was a significant and rapid decrease of the effects, which explains that the technical crew did not mention it and the cabin crew did not call the cockpit about it.

(my bolds)

I would still point to the same above phrase, questioned originally IIRC by Chris Scott.

That decel rate used is also used for the manual stall QTGs in the FFS, from which, among other things, the buffet levels are tuned. The entry rate dependent variation would seem to be of some 'significance'....at least training-wise if different in a 330.

One would think striving to avoid the training caveat: 'the same, except different' would not be unreasonable. Accuracy and fidelity for training or 'just' a 'gee-whiz' flight are not insignificant IMHO, especially if purported to apply over a broader range. Expert extrapolations with caveats, as valuable and as conducive to happiness as they may be, are still in this case, 340 to 330 extrapolations.

In 45+ years of flying, I have never discounted any detail.

[HazelNuts39]

Since the values ​​are different for flight AF447, it is likely that there was a significant and rapid decrease of the effectsFor the duration, as for the intensity, I invite you to look at the traces in the BEA Final report. Furthermore, it is not obvious on what information that statement is based. Maybe it would have been better to write: "... it is possible that there was a significant and rapid decrease of the effects, which could explain ...".

[DozyWannabe]

OK, so my bad on the "Experts" - however my suspicions over objectivity remain, as the usual suspects when it comes to Airbus-bashing seem to consistently refer to the report in favour of the BEA material.

[Owain Glyndwr]

however my suspicions over objectivity remain, as the usual suspects when it comes to Airbus-bashing seem to consistently refer to the report in favour of the BEA material.

Dozy,

I don't think you would include me as one of "the usual suspects"; at least I hope not!
Thanks to HN39 I have just acquired a copy of the Experts Report, and although I have not had time to read it in detail I have seen enough to convince me at least that it is a careful and objective description and analysis of the events and at least as 'good' as the BEA report.

[DozyWannabe]

No worries OG - perhaps my innate distrust of lawyers is somewhat overactive! :ok:

[Clandestino]

Why was that unofficial confirmation of 340 similarity even necessary? Beats me - it was for judicial purposes and I have not a slightest idea how French legal system works.

[Winnerhofer]

It is worth remembering that the the Judicial (Forensic) Experts' opinions are not binding on the judge.
Leurs avis ne s'imposent pas aux juges qui restent libres.

[Armchair]

Dozy, I suppose I should have said "the flight directors going haywire" (which we all know should have been turned off/ignored. Anyway, someone should confirm if the alerts are/are not hard-wired into Cvr so as to eliminate a potentially major flaw/reason the crew did not acknowledge stall. There was "ozone" smell in cockpit - shame if that were speaker unit and therefore...

Yes, I know it's a long shot, BTW.

[Clandestino]

No, it's a short one; it went no further than your foot. Alerts were picked up by CAM.

[CONF iture]

It should have quit based on what? Your opinion?
Stick neutral, the THS would still have tried to compensate to maintain 1G
At the time the AP and A/THR did quit, a sane degradation to Direct Law would have provided a welcome alternative.

[Chris Scott]

Quote from Clandestino:
"I was trying to point out discretely that you haven't read the part of AF447 report dealing with TAM incident which puts "kid gloves approach" straight into "old wives tales" category - something that has some basis in reality but through misunderstanding and misinterpretation diverges rapidly and significantly from it."

Setting aside your presumption that I hadn't read the reference to the TAM incident in the AF447 accident reports, are you suggesting that a "kid-gloves" approach would have been unsuitable in that case? Are you arguing that the extreme control inputs and attitude changes that the BEA describes were necessary and desirable to survive that UAS event? If not, just what point are you trying to make that places a "kid-gloves" recommendation into what you contemptuously describe as the "old wives' tales category"?

As a coplilot on B707s, I was on a flight where the AP went u/s before TOC out of Caracas for London at night. The captain and I took it in turns, of about 20 mins each, to handfly the a/c for about 7 hours. Fuel considerations necessitated step-climbs. It wasn't difficult, but it required unbroken concentration and - yes - a gentle touch. Our passengers didn't want (or need) to end up wearing the food that the flight attendants were serving them.

Quote from me:
"Regular hand-flying practice reinforces the understanding that in level cruise-flight, regardless of turbulence or windshear, any pitch attitude more than 2 or 3 degrees above or below the norm is unsustainable unless you want to climb or descend."
Reply from Clandestino:
"Regular use of autopilot does not absolve the pilot from obligation to check instruments. Idea that you need to handfly to know your typical flight-phase-related attitude is so unrealistic it... sorry, I can't find the phrase in English."

Never said it did. However, are you familiar with the concepts of "hands-on experience" and "human nature" ? Are you suggesting that a passenger who has never driven a car can take over suddenly and do as good a job as the driver, just because he has watched from the back seat? And in any case, are you suggesting that flight crews should and do spend hours monitoring every small change of attitude made by the AP?

[Winnerhofer]

TGl de Paris. N° Instruction : 2369109./52.N°du Parquet 0915408221

00:27:22 CDB : Ready

Echange de baladeur pour écouter un morceau de musique

01:05:06 PF : Réponse du mec qui n'a pas envie de s'enmerder

01:17:54 CDB : Bon faut savoir nager maintenant hein

01:18:58 PF : Ouais mais donne parce que je vais réactualiser les plages et tout le merdier, laisse, je vais m'occuper de ça

01:38:29 CDB : Ouais

Commentaires d'un article de magazine sur les paradis fiscaux

2:06:41.082 PF : Putain la vache

2:06:42,000 ? : Oh putain

2:06:42.911 PF : Heureusement qu'on est en 330

2:06:45.654 PF : On ferai pas les malins avec un 340...plein

[Winnerhofer]

Without the original and complete DCVR, we'll not be able to fully explain this crash.
Fragmented information relayed by the BEA isn't grounded on any evidence.
In this situation it's difficult to estimate to what extent the provided details agree with the facts, especially that the BEA rejects certain hypotheses without giving reasons such as on Bonin's licence which it backtracked in its 3rd intermediate report as opposed to the 1st interemediate report.
How does it explain its change of heart?
Now, the Judicial Expert's report provides more DCVR but too many pieces are missing from the puzzle.

New ECAM Warnings:
BEA FAULT
BEA REPORT 1 + BEA REPORT 3 DISAGREE

[Machinbird]

Winnerhofer
What law firm are you associated with?
Alternately, are you just one of those guys who likes to stir things up?

I was not enlightened as to the intent of your post 948 which appears to be additional irrelevant cockpit communication that the court has released. Just the kind of thing that BEA is supposed to remove from their report.

[Machinbird]

From the Norwegian B737 near stall event this telling morsel:
It's a pretty concerning incident. The sound of the trim wheel continuously running has been drummed into my head from Day 1 in the sim as a major cue that "something is not right" Too bad the A brand hasn't seen the value of this concept.

In the case of AF447, it is pretty evident that the crew was so stressed that they had turned their ears off.

Maybe the C chord tone is too overpowering when combined with other problems? Haven't flown it, so I have no idea.

[DozyWannabe]

Too bad the A brand hasn't seen the value of this concept.

Brand A do see the value of the concept, as there is an audible "bell" warning when the trim wheel is moving on the A300/A310 types - i.e. those with a conventional approach to trim.

Approach to trim use is somewhat different on the FBW types, in the sense that the automatic trim will be operating more often than would be the case traditionally, and a mechanical aural alert every time the trim wheel moves could be an annoyance or distraction. That said, an aural alert when trim exceeds a certain value could be a useful addition.

In the case of AF447, it is pretty evident that the crew was so stressed that they had turned their ears off.

Is it that specific? We've got plenty of examples where a stressful situation has caused crews to disregard aural, visual and tactile warnings.

Maybe the C chord tone is too overpowering when combined with other problems? Haven't flown it, so I have no idea.

In our sim experiments, the C-chord was certainly no more intrusive than STALLSTALL, but they were both certainly attention-grabbers!

[Winnerhofer]

BEA fails to mention if these guys were ETOPS-rated.
Show me the ETOPS!

[DozyWannabe]

Bonin's licence which it backtracked in its 3rd intermediate report as opposed to the 1st interemediate report...

In what way?

BEA fails to mention if these guys were ETOPS-rated.

I think we'd all have heard about it if they weren't! An A330 type certification pretty much implies an ETOPS certification, does it not?

[Winnerhofer]

Implies indeed and therin lies the nastiest of rubs.
It's a seperate rating with a specific exam ipso facto of A330 rating which is line-checked.
The TSB published the ratings of the SR111 crew with a specific reference to their respective ETOPS ratings.
The BEA hasn't come out with theirs yet....

[DozyWannabe]

The TSB published the ratings of the SR111 crew with a specific reference to their respective ETOPS ratings.

Well yes, the MD-11 is a trijet and therefore no such inference can be derived!

[Winnerhofer]

Forgot those trijets...TRITOPS!

[jcjeant]

Airbus trim wheels
Movement perfectly visible .. if you check it !
glbEWHiC5hs

[john_tullamarine]

Folks,

I've deleted some commentary in the last page.

Robust discussion is fine and that includes criticism.

However, savage criticism not backed up by objective, public domain citation is not fair play and will be removed.

[Machinbird]

Movement perfectly visible .. if you check it !Yes, but only visible in your peripheral vision or by turning your head.

Not so good when there are interesting things going on in front of you.

If you think about it, trim should only move as you accelerate/decelerate or change configuration.
You do not want it to make a run into one of the stops unknown and unseen.

[Machinbird]

In our sim experiments, the C-chord was certainly no more intrusive than STALLSTALL, but they were both certainly attention-grabbers!
The desired result from such warning sounds should be to alert the crew to a problem, but not to overburden the cockpit aural environment.

Instead of: STALL STALL STALL STALL STALL STALL with crickets interspersed
perhaps
STALL STALL STALL STALL STALL STALL STALL STALL STALL ..... with crickets
would be a better choice.

Maybe the warnings should be prioritized also. The C chord altitude alert should be a lower priority than the Stall warning.

After all, you can't fix the altitude until the aircraft is under control.

[Winnerhofer]

David ROBERT a réalisé au cours de ce stage le ler juillet 2007, un exercice STALL WARNING mais A l'issue de ce contrôle noté satisfaisant, son niveau professionnel ayant été jugé perfectible, David ROBERT a été convoqué à un entretien technique.

Robert underwent his STALL WARNING training but although he made it through his check, his professionalism was deemed to be improvable and was summoned for a technical interview.

Marc Dubois n'a jamais fait de stage spécifique " Commandant de Bord " ni chez Air Inter ni chez Air France
Chez Air Inter, il n'a été que co-pilote y compris sur A320.
Il est allé ensuite chez la Postale sur 737/200 et n'a été nommé CDB A320 chez AF que 29 mai 2001
Tous les CDB IT et/ou AF ont fait des stages spécifiques Commandant de Bord, indépendants de la qualif de l'avion sur lequel on va être qualifié en tant que tel.

Marc Dubois never underwent CDB (Commandant de Bord) training.
All AF & IT CDB regardless of their ratings had to undergo the CDB training.

[HazelNuts39]

Machinbird,

THe stall warning consists of a “STALL, STALL” aural warning, followed
by a characteristic cricket sound and the illumination of the Master Warning light. It has priority over the C-chord warning, so the C-chord is interrupted when the stall warning is active.

[Clandestino]

Once again, PPRuNe helps me understand why even DECs nowadays have to hop through "Reading comprehension" HR hoops.

Setting aside your presumption that I hadn't read the reference to the TAM incident in the AF447 accident reportsSorry; I stand corrected. Presumption was based on obvious signs you had no clue about it.

are you suggesting that a "kid-gloves" approach would have been unsuitable in that case?No.

Are you arguing that the extreme control inputs and attitude changes that the BEA describes were necessary and desirable to survive that UAS event? No.

If not, just what point are you trying to make that places a "kid-gloves" recommendation into what you contemptuously describe as the "old wives' tales category"?That talk about "oh-so-sensitive-controls-that-eat-inexperienced-pilots-for-breakfast-when-they-try-to-handfly-at-altitude" is total bollocks. If you haven't read and understood HTBJ, well there is TAM crew that has proven you can throw altn lawed A330 around and not even hurt anyone. Their actions were massively wrong but absolutely not fatal! AF447 was not downed by manual ineptitude but by sustained pitch-up input! CM2 wanted to climb and aeroplane just couldn't comply with demand because of gravity and air density.

However, are you familiar with the concepts of "hands-on experience" and "human nature" ?Both. PPRuNe constantly reminds me about the second one.

Are you suggesting that a passenger who has never driven a car can take over suddenly and do as good a job as the driver, just because he has watched from the back seat? And in any case, are you suggesting that flight crews should and do spend hours monitoring every small change of attitude made by the AP?I am suggesting these loaded questions just show popular prejudice of the way modern passenger aeroplanes are flown and have merely slight resemblance to reality.

[Winnerhofer]

Airbus rejected the findings of the Experts' report because one of the members was ex-AF with no Airbus experience whatsoever.
L’un d’entre eux, l’ancien pilote Alain de Valence a fait toute sa carrière chez Air France, qu’il n’a quitté qu’en 2007.
L?impartialité des experts mise en cause - Libération (http://www.liberation.fr/societe/2010/04/24/l-impartialite-des-experts-mise-en-cause_622557)

[Winnerhofer]

Experts Report (http://blogs.mediapart.fr/blog/buss/291113/experts-report)

[Winnerhofer]

The report that AF don't want you ever to read...
ISRT (http://blogs.mediapart.fr/blog/buss/291113/isrt)

[roulishollandais]

I don't want to regster on Mediapart or Liberation newspaper online. Did you find sure unknown informations in these three documents?

[A33Zab]

@Winnerhofer:

How to download the reports?
All I see is a picture of BUSS that I personally photographed and edited with additional information.

[Winnerhofer]

ISRT - AF447 (http://af447.over-blog.com/2013/11/isrt.html)

Fuller DCVR - AF447 (http://af447.over-blog.com/2013/11/full-dcvr.html)

[rudderrudderrat]

Originally Posted by Clandestino
Not just that: even wings designed for similar missions have widely diverging characteristics near the envelope edge. 737NG has mach trim, 320 doesn't.
Er..... What do you think the autotrim is doing at high Mach numbers?
Why do you think the speed limit in Direct Law is .77Mach.

[Chris Scott]

Clandestino,

Reading your most recent strictures, must admit I'm starting to wonder exactly what we are arguing about here. You seem determined to misinterpret and misrepresent my posts, and no doubt most readers will have lost any interest in our exchanges by now. The trouble is, your responses to my considered opinions are so terse, shrill, and contemptuous that - always up for a challenge - you give me little choice other than to reply.

Quote:
That talk about "oh-so-sensitive-controls-that-eat-inexperienced-pilots-for-breakfast-when-they-try-to-handfly-at-altitude" is total bollocks...
...there is TAM crew that has proven you can throw altn lawed A330 around and not even hurt anyone. Their actions were massively wrong but absolutely not fatal!

Actually, I commented that hand-flying even the B707 for hours at cruise altitude (in akin to "Direct Law", with no protections except Mach trim and yaw damper):
"wasn't difficult, but it required unbroken concentration and - yes - a gentle touch. Our passengers didn't want (or need) to end up wearing the food that the flight attendants were serving them."
Not sure if the TAM incident was during a meal service, but in any case you cannot remain standing on the floor of an a/c during negative G, and it's even difficult to remain in your seat if unbelted. Anyway, I'm glad you accept that their flying was less than ideal...

You would no doubt agree that the TAM crew grossly over-controlled the a/c, which I suspect was mainly due to a lack of familiarity with hand flying at cruise altitude. Fortunately, they didn't quite achieve +2.5g or -1G, so that element of the protections was not employed.

Quote:
If you haven't read and understood HTBJ...

Surprise! I read Davies's first edition around 1970. By the following year, I was a full-time co-pilot (we didn't have heavy crews in those days) on VC10s, cruising at M0.82 - 0.86 at up to FL430. A tad faster and higher than the A330. What were you doing in those days?

Quote:
I am suggesting these loaded questions just show popular prejudice of the way modern passenger aeroplanes are flown and have merely slight resemblance to reality.

Not sure about popular prejudice these days, but we certainly heard it when we launched A320 ops in 1988. If you are saying that my own suggestions for improving the handling skills of the present generation of big-jet crews have "merely slight resemblance to reality", you should bear in mind that - after five widely-differing jets during 17 years - my last 14-years' flying were spent on the A320. As you know well, but some of our readers may not, the A320 cockpit and FBW system is almost identical to the A330's, and the difference in speeds and altitudes negligible.

There have been few changes to the Airbus FBW cockpit in its 25 years of airline operation, but most airline pilots on jets today lack much of the jet handling experience that was second nature to my generation. They are highly orientated towards the handling of the automatics, and failures of all kinds are uncommon. That may even be a mixed blessing. There were already signs of this impending problem 20 years ago, and it is not restricted to FBW Airbuses. What I am advocating for pilots is the opportunity for self-development. If you are inclined to restrict yourselves to a role of simply programming and monitoring the automatics of flight, that is a mind-numbing task on long-haul that might as well be conducted from the ground. What do you do on a routine sector of 12 hours or more?

Anyone who has become detached for long periods from the pilot's primary task of maintaining a reasonable flight path, and has limited hands-on experience to fall back on, is less likely to act appropriately when something unexpected happens; i.e., more vulnerable to the startle factor.

[Winnerhofer]

Air France :

a) Did not correctly transmitted to the authorities reports on the in-flight incidents involving Pitot probes by Thales. .

b) Did not ask (or not with enough emphasis) Airbus replace these probes with BF Goodrich deemed much less susceptible to icing.

c) Did not ask for installation on its aircraft BUSS system while most other companies are equipped.

d) The procedure laid down in time for the treatment of cases of failure of the Pitot probes (UAS) was inappropriate.

e) It has not properly trained its pilots in the case of failure or recovery from the stalls.

Airbus :

a) The Pitot probes are the root cause of this disaster.

b) Their fault that generated the cascade of events bad decisions and pilot error that led to the fatal stall.

c) Airbus selected Thales probes, regardless of feedback.

d) Continued to install them on its aircraft at the expense of BF Goodrich probes (U.S. ) which are far less susceptible to icing.

e) As a system, the A330 is not tolerant to single failure of the Pitot probes, which is contrary to all the rules of reliability and dependability . For an event of this severity (catastrophic , in the sense of the term dependability , i.e. which can cause victims), the system must be fail-safe design (it must guarantee the safety of the flight despite the failure ), and even FS / FS that is tolerant to double down.

Namely redundancy probes (actually 3 ) is false redundancy since all the sensors are the same technology therefore likely to fail at the same time , under the effect of a single common cause .. . icing.

Strictly speaking the triplex systems are supposed to parallel the different technologies , in order to avoid simultaneous failures on common mode

[Chris Scott]

Hi Winnerhofer,

Thanks for your link to the "full" Transcription CVR from the Rapport d'Expertise of 2012 (sometimes referred to as the judicial report), and the Conclusions.

It fills in some of the "(...)"s in the transcript pubished in Appendix 1 of the BEA Final Report, and there are some split-second variations in timing. However, I've yet to find any evidence of supernumerary presence in the cockpit, which you claimed a few days ago?

Re your latest post, quote:
e) As a system, the A330 is not tolerant to single failure of the Pitot probes, which is contrary to all the rules of reliability and dependability . For an event of this severity (catastrophic , in the sense of the term dependability , i.e. which can cause victims), the system must be fail-safe design (it must guarantee the safety of the flight despite the failure ), and even FS / FS that is tolerant to double down.

I've never been involved in engineering or standards of certification, but venture to suggest that, as a system, the A330 and its crew is indeed tolerant to a failure of all 3 airspeed probes, provided the crew acts in a manner that might be expected of one which is properly qualified in terms of training and experience. Having said that, it is clear that the training, SOPs and the UAS drills/checklist left much to be desired.

Quote:
Namely redundancy probes (actually 3 ) is false redundancy since all the sensors are the same technology therefore likely to fail at the same time , under the effect of a single common cause .. . icing.

Yes, and this is not peculiar to Airbus, When we discussed this a couple of years ago on an AF447 thread, I commented that it had sometimes crossed my mind - during external checks on various a/c, incuding Airbuses - that the policy of mounting pitot probes and AoA probes symmetrically left and right invites the coincidence in timing of any icing problems. This tends to pertain to the #1 & #2 probes, with the #3 being asymmetric to them. One can understand the traditional philosophy of similarity of the two primary detectors, but it will be interesting to see if AF447 leads to a rethink at least in terms of the siting of probes, if not dissimilar specifications of the probes (and/or probe-heaters) themselves.

[AlphaZuluRomeo]

(Re)Marks: (reference: post #974)

Air France :
a) I cannot comment; if true, I (sadly) won't be entirely suprised. Let's say 1.
b) Wrong; AF asked; to say "not with enough emphasis" is hindsight. 0.
c) How is this relevant? Doesn't BUSS work @ lower than FL250 only? No one can tell a BUSS-equipped A330 would have met a different ending, this night. 0.
d) It may have been better worded (and was, since). But it was not inappropriate. 0.25 for the ink.
e) Agreed. Regarding stall recovery, it was not AF, it was industry-wide. 0.75.

Total: 2/5. Case lost IMO.

Airbus :
a) Wrong. First event in the chain does not equal to root cause. 0.
b) Wrong. Their fault didn't generate (in the sense of being responsible of). 0.
c) I cannot comment; if true, I (sadly) won't be entirely suprised. Let's say 1.
d) Is same than C. No point.
e) Wrong. 0.

Total: 1/5 (because I have no argument against/for this unique point). Case lost IMO.

It should be added that Airbus and Air France have deep pockets, and sprinkle a few coefficients on all this for a chance to win the day. :E

OTOH, thanks for you last links, will read that with attention a bit later :)

[Winnerhofer]

00:31:16 CDB: J'aime bien sentir la marche
(I like to feel the step)

This bit has been overlooked.
What he did was it that he yanked the S/S which which resulted in NU movement of the THS as shown on the DFDR.

[DonH]

Chris Scott;

Re, "However, I've yet to find any evidence of supernumerary presence in the cockpit, which you [Winnerhofer] claimed a few days ago?"

In the CVR record, there are some communications with the F/As. Such communications are routine and usually concern meals, anticipated turbulence, route information, passenger matters, etc. It would not be uncommon for an FA to be on the flight deck for a few moments for such communications. Many times such communications are done through the cockpit-cabin interphone system but of course the meals are always brought into the cockpit and inevitably a short chat takes place. Normal operations, (meal service, discussions regarding turbulence, etc) would not be "evidence of supernumerary presence".

It may be different in Europe, the US etc, (although I doubt it), but regarding ETOPS qualifications, pilots are trained and qualified for such operations but ETOPS is not an endorsement on the licence. Just as one is not "endorsed" for Category III operations, one is trained and qualified for such operations on the airplane one is operating. Such training and qualifications would normally only be part of the pilot's current qualification file and are not on the actual pilot's licence.

For the record regarding comments made elsewhere in re SW111, last time I looked, the MD11 was a 3-engine aircraft and ETOPS stands for "Extended-range Twin-engine Operational Performance Standards" and the TSB made no such comments regarding crew ETOPS qualifications.

[Chris Scott]

Hello Don,

Yes, the only exchanges I've seen so far fall into the category of short exchanges with flight-attendants in the two ways you describe. Pity that the CVR transcript does not distinguish between the different audio channels, i.e.: output from area microphone, inputs to pilots headphones, and output from pilots' headset-microphones.

BTW, do we yet know if the pilots' headset-microphones on the A330 in AF are permanently "hot", as on all British a/c (IIRC)?

[Mr Optimistic]

On the transcript, does the red sideline mean the stall warning is active and audible?

[Winnerhofer]

AF447: Ménage à Trop - AF447 (http://af447.over-blog.com/2013/12/af447-m%C3%A9nage-%C3%A0-trop.html)

[DonH]

Hi Chris;

I believe all A330 mikes (4 - two forward seats, two observer seats) are hot by design which I expect would include cabin interphone communications, (handset on the rear of the pedestal). It's reasonable to assume that the cockpit mike picked up pilot-FA communications in the cockpit.

From an earlier post, above, "There were already signs of this impending problem 20 years ago, and it is not restricted to FBW Airbuses.", yes indeed there were. In fact AW&ST ran a series of articles on automation in August of 1989 and in late January and early February of 1995. The problem was seen and being understood from the earliest days.

A discussion of why the problem not only continued to grow in breadth but also in depth, (ie., it got worse) is beyond the present thread's context and "charter" so to speak and each of us will have our own theories that I'll just touch on.

The trend itself was, and remains clear, however. I agree with come posters here who say that more manual flight training may not be the answer, although psycho-motor skills do need constant reinforcement to build muscle memory that can be quickly relied upon when rational thought and analysis can take more time.

To me it is separation of the cockpit from flying the machine that is the model for the separation of the vastly different human psychological-physical acts of button-pushing (which is "on-the-surface" cognitive activity, from arms-legs control movement, which (I would offer) is more on the autonomic side of human muscular activity. One no longer straps the airplane on so to speak, one sits "in" it and manages it and is placed psychologically "outside" of the machine.

We're not digital creatures and although we quickly adapt, there is what I used to call a "digital veil" between pilots and the machine that wasn't there in, say, the DC8 (or, I would hazard a guess, the VC10). I don't think the human factors which have evolved out of the past 20 years, of which this accident is but one example, have been examined nearly deeply enough - perhaps that is for all those safety conferences held around the world but I would like to have seen more from the BEA in this regard.

That said, I think automation is a far safer way to fly transports and given the numbers, crews have adapted to automation, "mode Normal", admirably.

But I can attest having experienced it, when it fails and the airplane (A330) is in the process of degrading itself to its next level of control as it adjusts to a system failure, it can be momentarily, very busy. One just has to let it do its thing and settle down.

As with the loss of airspeed information, generally one does not have to act swiftly, automatically but slowly carry out the Abnormal SOPs as has been amply described in these threads.

Anyway, enough drift.

[Machinbird]

On the transcript, does the red sideline mean the stall warning is active and audible? The legend is in the top right corner of page 10 of the DFDR document.
The red sideline indicates the stall warning is active and (presumably) heard on the tape. When the stall warning is not active, the C chord is active almost the entire remaining time (stall warning not active) except for a brief interval just after the Captain entered the flight deck when they transitioned the correct FL.

My thanks to HN39 for straightening out my misconception about the signals being interleaved. Stall warning has absolute priority while active.

[Mr Optimistic]

Machinbird, yes that is how I took it to be read. But what about all the 'stall inhibited' discussion and the discussion that the Cpt didn't have a chance to hear it other than 1 sec after he returned ? Also, a lot of dual input tussles: almost a continuous 'fight'.

[DonH]

Mr. Optimistic;

Re, "Also, a lot of dual input tussles: almost a continuous 'fight'. "

Yes, as we know from the threads, dual inputs are absolutely verboten in the Airbus. You either take control or leave it alone. If someone is doing something leading to an accident, one takes the airplane, and sorts it out on the ground later. The trouble is, the PF continuously interferred with what the PNF sensed and wanted to do and they failed to sort it out. Courtesy, arguing and timidness won out over training, SOPs, CRM and ultimately, survival in this accident.

[Winnerhofer]

AF447: A Disaster Foretold - AF447 (http://af447.over-blog.com/2013/12/af447-a-disaster-foretold.html)

[Winnerhofer]

All BEA annotations:

RAPPORT FINAL-050712-ARH.pdf (https://docs.google.com/open?id=0B_3H91SLUEGcVXdGXzdzdE43cjg)

[Chris Scott]

Quote from DonH (my emphasis):
I agree with come posters here who say that more manual flight training may not be the answer, although psycho-motor skills do need constant reinforcement to build muscle memory that can be quickly relied upon when rational thought and analysis can take more time.

There are certainly no easy solutions to the problem, which we and others recognize. However, in the many UAS events covered in the BEA AF447 reports, the PFs have had no alternative than to take manual control at short notice. Whether that sudden and unexpected transition initially involves action or inaction on the side-stick, it is going to be far less challenging mentally and physically if the PF has had fairly recent experience of hand-flying the a/c (also in C* law in this case) without FD in similar conditions, albeit with the advantage of an ASI.

Evidence suggests that the PF of AF447 tensed up, pulling the stick back inadvertently as he concentrated on controlling roll in roll-direct law. That would imply a lack of confidence in his ability simply to fly the a/c straight and level. Confidence, IMO, is enhanced by practice. Lack of confidence exacerbates the initial startle factor.

I've already covered the issue of familiarity with the effect of small changes of pitch attitude in recent posts. As we have seen on this thread, it is not only UAS that can lead to pilots losing control when the AP disengages at altitude.

[Winnerhofer]

Psychometrics
Bonin was exempted.
30 AF F/As were fast-tracked in 2008 onto the LH-seat.
Psychometric testing eliminates 70% of candidates.
Robert
Indeed, he was the odd-man out and the least incompetent.
He was alone i.e. w/o spouse or companion.
Yes, inhibitions based on courtesy meant that Robert and Dubois had no effective authority over Bonin.
Dubois was in an other World and plagued by strife on the home front.
The social interraction of the crew overruled CRM.

[Winnerhofer]

Quote:

Airbus l'a formellement contestée et des experts internationnaux seront nommés notammanet un Professeur suisse.
Elle est bourrée d'erreurs et de raisonnement qui ne tiennent pas la route.

Airbus has formally contested the findings of the Experts and new international panel consisting of non-French members have been appointed notably a Swiss Professor.
The Experts report is riddled with errors and reasoning that doesn't hold water.

The technical bit that Airbus has a bone about is that the report confuses AOA and pitch.

Now let de battle commence!

[john_tullamarine]

Thread #12 starts here (http://www.pprune.org/tech-log/539756-af-447-thread-no-12-a.html#post8476687)