Judd

I have been an avid reader of aviation safety reports for years. So much can be learned from them and retained for future events. Having also been in the simulator training game also for many years I have discovered that many pilots undergoing type rating training or re-currency lack interest or the motivation to study the various flight safety hand-outs I offered them. These are incident, technical articles and accident reports very much applicable to the type they will be flying.
Understandably these pilots just wanted to get through the course with the minimum of study and hand-outs which were not part of the course for a type rating were seen by many of them as unnecessary. I recall talking to one pilot who told me he felt that old accidents were no help in passing the course and ticking the boxes.

There is no excuse for lazy pilots many of whom are happy to spend hours of their time on social media but who seemingly couldn't give a rats for technical information that should be a part of their professional lives. With the advent of Pprune there is a plethora of excellent information on every facet of incident and accident studies especially through the hundreds of links. Yet I very much doubt that lazy pilots study these reports even though they may be flying the specific aircraft type.


OK, this rant has probably nothing to do with the Air France A330 tragedy but believe me there are pilots out there who couldn't care less about their own professional development as long as their automatic pilot works as advertised.

roulishollandais

@DozyWanabee
I used an ellipse of Law of flight change to emphasise the fact that the change of law is a worthful possible situation aswell as the other contexts from my list drifting tothe final minutes.

vilas

Generally it is believed that lack of experience is the problem. In this topic of stall alone we have seen that both experienced and inexperienced pilots have not only stalled the aeroplane they have not been able to apply correct recovery procedures. Experience is a very vague word. Mostly we log uneventful thousands of hours and that's how it should be otherwise the technology needs another look. But this innocuous experience does not give any confidence in dealing with abnormal situations. In aviation one does not learn through one's mistakes. So when it happens it is always first time. The confidence comes out of basic flying ability which does not require thousands of hours but sufficient practice depending on individual ability and good knowledge of abnormal procedures. Since we as a specie have no instincts in the air procedures are the only thing which saves the day for us. Everything we do in the air is acquired skill nothing is natural. There are experienced pilots who find it tough to do raw data ILS and there are others who cannot do visual approaches. It is because they never acquired the scan or the judgment. It all starts with simulator training. If not properly trained you cannot do it on line. If the SFO pilots would have tried as practice a visual approach some where else the result may have been same. With autopilot you are not handling the controls but scan is no different than manual flying. In some airlines with seniority pilots reach non judgmental stage where their checks become an exercise in ticking boxes. Nobody tells them anything anymore. Also with financial pressures airlines are reluctant to spend money on training. After all it is a business. Best airline is the one that stays afloat.

PJ2

Judd, villas, well said and I think on-topic insofar as we are digging around in human performance aspects of aviation accidents, which AF447 is, (again emphasizing that blame is not a part of this kind of examination). In this there are perhaps some commonalities between this and the Colgan accident at Buffalo, (I know this has been broached previously...just making the connection on "Thread 12").

A technical question regarding the Airbus which may have been answered in the other threads - IIRC there was mention that the stall warning could or should inhibit movement of the THS - I believe there was something in the Perpignan accident report about this. There is lots to think about in such a design - should it do so in Normal Law as well as the two Alternate Laws? However, were it to do so, would it limit elevator authority if it did not move in response to elevator demand as ordered by the stick? Would there be a need in "normal" flight for a THS setting of -13°? ...in Alternate Law?

It is hard to think of such a case at cruise altitudes, but what other considerations might there be that makes it a better idea to place limits on THS movement in certain phases of flight?

These questions will have been thoroughly thought through of course even if some might consider the design puzzling in the hindsight of the accident.

BOAC

- hi - missed you around here. Way back I suggested that THS movement should be STOPPED at some suitable angle and require an over-ride to continue trimming, this in the hope that 'automatons' might notice all was not well. I still think it is good idea. The over-ride option would cater for your concerns, I feel? It (the 'wake-up call') might have gone a long way to preventing the Turkish 737 AMS crash.

Owain Glyndwr

The Airbus FCOM says, for normal law [1.27.20 p2]


<When angle of attack protection is active, THS is limited between setting at entry in protection and 2 deg nose down (i.e. further nose up trim cannot be applied).>


The question is WTH was this not carried over to Alternate laws??? I believe it is carried over on the A320.

rudderrudderrat

Hi Owain,
I believe you are correct: FCOM OP-020, Flight Controls, Alternate Law
"At the flight envelope limit, the aircraft is not protected, i.e.:
In high speed, natural aircraft static stability is restored with an overspeed warning
In low speed (at a speed threshold that is below VLS), the automatic pitch trim stops and natural longitudinal static stability is restored, with a stall warning at 1.03 VS1G."

Since the aircraft is no longer "protected" in Alt Law, how did the certification process of A330 satisfy:
Section 5. Stability
26. Static Longitudinal Stability and Demonstration of Static Longitudinal Stability -
§§ 25.173 and 25.175. ?
http://www.faa.gov/documentLibrary/m...2025-7C%20.pdf

Owain Glyndwr

Hi rrr,


Well of course the document you reference is an AC not a requirement, but the answer to your question I think is that there is a Special Condition for A330/A340 certification against JAR 25.173 and 25.175 (EASA TCD A015 Annex; Special Condition F3):

infrequentflyer789

Exactly, so the question is does it meet the special conditions for certification.

The BEA had what I thought were some very interesting comments on this in the final report (had me chasing off for references), along with what I thought was a veiled / sarcastic criticism. However, I am reading that from the English, since my French (and knowledge of French diplomacy) isn't good enough to pick up the nuances in the original.

Since then I haven't seen the issue raised anywhere (not sure even on these threads) and notably not in any of the various presentations / articles from those who want to blame-the-plane, many of which have been linked here. Since most of those are in French, I have started to think it is either an artefact of my imagination, or one of translation. Even Winnerhofer's annotated BEA report didn't seem to pick up on it.

So the next question is why did you highlight (bold) the bit of the special condition that you did and not the, er, other bit ?

Owain Glyndwr

@infrequently flier



Well obviously the certificating authorities (all ten of them together IIRC) thought so!



Er - which other bit?
I highlighted the bold bit simply to emphasise that the stick force vs speed characteristics described in the FAA document rrr cited are not relevant to A330 certification

rudderrudderrat

Hi Owain,
Thanks for pointing out that you think there is a Special Condition for A330/A340 certification against JAR 25.173 and 25.175 (EASA TCD A015 Annex; Special Condition F3): which explains what the final (report Page 187) was referring to.

"When there are no protections left, the aeroplane no longer possesses positive longitudinal static stability even on approach to stall. This absence specifically results in the fact that it is not necessary to make or increase a nose-up input to compensate for a loss of speed while maintaining aeroplane altitude. This behaviour, even if it may appear contrary to some provisions in the basic regulations, was judged to be acceptable by the certification authorities by taking into account special conditions and interpretation material. Indeed, the presence of flight envelope protections makes neutral longitudinal static stability acceptable.

However, positive longitudinal static stability on an aeroplane can be useful since it allows the pilot to have a sensory return (via the position of the stick) on the situation of his aeroplane in terms of speed in relation to its point of equilibrium (trim) at constant thrust. Specifically, the approach to stall on a classic aeroplane is always associated with a more or less pronounced nose-up input. This is not the case on the A330 in alternate law. The specific consequence is that in this control law the aeroplane, placed in a configuration where the thrust is not sufficient to maintain speed on the flight path, would end up by stalling without any inputs on the sidestick. It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall."

I just wonder why the A330 in ALT Law wasn't designed to have the same positive static stability of the A320.

infrequentflyer789

Sorry, but no, it's not complete DCVR. Daily Mail is just referring to the Vanity Fair article already linked on this thread. No new information.

G-CPTN

Apologies if already posted.

From:- 'F***, we're dead': Cried Air France pilot minutes before plane crash on flight between Rio de Janeiro and Paris | Metro News

Wedge

I think that story arises out of this big feature in this month's Vanity Fair magazine.

Interesting stuff.

Should Airplanes Be Flying Themselves? | Vanity Fair

gums

I think I get what the "report" was getting at, but I also think it does not apply in direct law.

With gee and pitch rate components of the other laws, the jet is basically "neutral" for speed stability ( no "trimmed" airspeed as we old farts remember). So slowing up does not lower the nose as we were used to. And the converse for application of power regardless of engine mounting - you won't climb to maintain the "trimmed" speed ( actually AoA).

But this is the first I have seen for the jet not having positive static stability. I mean basic aerodynamic stability, unfettered by computers using rate and gee and air data sensors. My trusty Viper was no kidding statically unstable until above 0.9 M. We also did not have the plethera of alternate modes and sub-alternate modes - it was gee and AoA protections only. But like the 'bus, we were neutral WRT speed stability. Sucker would hold the trimmed gee until it reached 27 degrees AoA ( remember, we could trim for a gee).

Need Mssr Palmer here, or someone else to try "direct law" and set the THS, then let go of the stick.

infrequentflyer789

Yes, and that is what the BEA more or less said - the behaviour is not compliant with the regs, but it is ok (implied) because the certification authorities said so, based on special conditions.

I found it slightly odd that they put the onus on the opinion of the certifiers rather than say something more definite like "it is ok because it complies with special condition XY which replaces regulation Z", and it was that that had me going off looking for the actual special conditions when I read it.

My bad - I confess I skipped the detail from rrr's post because my understanding is that anything in that section of the regs is inapplicable because the whole section is replaced by the special condition - unsuprisingly because it is all around positive static longitudinal stability, which the fbw 'bus does not have.

The bit of the special conditions that got my attention was this:

ALT2B is, however, neutral stability and without speed protections, is it not ? BEA seems to think so, at least to my reading of 2.2.5 in the report (p186-7 in English pdf). Condensing a bit:

I've substituted "; i.e. that" for ". Indeed" at the end there, because it is one sentence in the original French and I think the intended sense is that they are specifying what the special condition is.

So, essentially, the behaviour of the a/c without protections was accepted by the certification authorities because of the protections. Now I thought that was a rather odd statement and possibly a veiled criticism of said certification authorities, but maybe I am the only one who reads it that way.

jcjeant

If it's one thing remind (and this is actually the most important) is that Airbus (or any other manufacturer) had not made ​​for fun to show they can do it .. but for sale
Having known that .. so they will make all this is necessary to achieve that goal even if it is necessary to take steps to adapt the certifications rules to their products (and so for the "derogations")

Gysbreght

No, that is not correct. You have to distinguish normal operation and operation with system failures. Alternate law is a rare failure condition which, by design, does not occur more often than once in 100,000 flight hours. At that level of probability, no airplane is required to meet the flying characteristics requirements of Subpart B. Those requirements, and the special conditions you reference, apply for the airplane systems functioning as designed, without failures.

jcjeant

Seems to me (from the BEA report) that the AF447 was all the way down ( the loss of speed indication was short) a airplane with all systems functioning as designed without failures even in alternate law
Alternate law is not a failure

Owain Glyndwr

Quote:

think I get what the "report" was getting at, but I also think it does not apply in direct law.

Gums, I agree – in direct law the conditions that gave rise to the special condition do not apply so the aircraft has to meet JAR25.173 and 25.175 as written. It is certificated, so it must meet those requirements, but this is not strictly relevant to the present discussion.
I must admit I struggle to get my head around statements like:

Quote:

This absence specifically results in the fact that it is not necessary to make or increase a nose-up input to compensate for a loss of speed while maintaining aeroplane altitude

I think I understood it eventually, but at first it seems counterproductive to apply a nose up command to compensate a speed loss.

Quote:

But this is the first I have seen for the jet not having positive static stability. I mean basic aerodynamic stability, unfettered by computers using rate and gee and air data sensors

I think the problem in part arises from the labelling of the FAR/JAR paragraph. When “static stability” comes up my mind (and maybe yours gums?) goes to considerations of short period response and return to the trimmed AOA after a disturbance. I don’t think there is any doubt that the ‘bus is stable or strongly stable in this respect in ANY law.
The FAR/JAR wording however relates solely to speed variations seen through stick movements and which involve excitation and damping of the long period (phugoid) dynamic characteristics. But the ‘g’ feedback in normal and alternate laws controls the aircraft to a steady flight path which takes away one degree of freedom and the phugoid disappears to be replaced (in speed stability terms) by a one degree of freedom convergence or divergence depending on where the aircraft sits on the (thrust – drag) curve. The conventional stick/speed relationships then do not apply; hence the SC, which says that:

Quote:

longitudinal static stability characteristics will need to be determined on the basis of the aeroplane's response to disturbances

Because of compressibility effects the (T-D) profile of a modern airliner in cruise is more like a bathtub than the classic parabola. At the high end of the speed range, where the aircraft is hovering on the edge of drag rise, the response to a speed disturbance will be stable. From there down to the minimum operational speed (say 1.3Vs) the aircraft will be marginally stable. It would be not until one gets below that that instability creeps in.
This might be seen as weasel wording, but given the probability of dropping to ALTN law (most pilots will never see it throughout their career we are told), a marginally stable aircraft which meets the book (just) in normal operating speed range might be considered acceptable even without protections.
Below 1.3Vs the aircraft is speed unstable and this is where the BEA comment to the effect that the aircraft might drift to stall even with zero stick input becomes valid. However, if one puts some real numbers into the equations one finds that in level flight it would take about twenty minutes to decelerate from 1.3Vs down to Vs. Put some mild climb demand into the sums so that the initial thrust deficit is greater and a very different story emerges – that deceleration could take twenty seconds rather than minutes. [My numbers might be challengeable, but I think the principle holds – if you start from a speed yielding nearly neutral stability the initial divergence rate will be very low]
So the ‘hole’ in the certification would appear to be that the static speed stability in a combination of alternate law and flight outside the normal flight operational envelope was not checked. [But note that FAR/JAR 25.175 does not apply to speeds less than 1.3VSR1 so if this philosophy was carried over to the SC there would be no hole].
The point I am trying to make is that an aircraft may be neutrally speed stable in response to stick inputs but might still be speed stable in response to atmospheric disturbances and it is this latter that is used to define whether the requirements are met.
Gysbreght, I agree that according to JAR principles the full handling requirements might not be applicable in a failure case (and jcjeant, ALTN is a consequence of some sort of failure so the probability principle applies) but you cannot abandon the handling requirements altogether, so there must be something there appropriate to the failure probability level. Since there are no specific requirements relating to ALTN, my guess would be that the normal requirements were applied, albeit with some less stringent interpretation. Others may wish to comment on the probity of more relaxed interpretation of the rules at a time when things are getting difficult!
I have some difficulty with the logic of the final BEA sentence in:

Quote:

The specific consequence is that in this control law the aeroplane, placed in a configuration where the thrust is not sufficient to maintain speed on the flight path, would end up by stalling without any inputs on the sidestick. It appears that this absence of positive static stability could have contributed to the PF not identifying the approach to stall."

He might have been unaware that the aircraft could be driven towards stall without any input from him, but why would he not be aware that maintaining up elevator for a prolonged period would drive the aircraft towards stall?