AF 447 Thread No. 7 [Archive] - Page 3

HazelNuts39

26th Nov 2011, 11:32

If the droplets don't freeze until they are behind the ice detector then is is possible that the ice detectors can't detect their presence in a similar manner?The referenced paper offers a number of arguments for the prevailing opinion that the high altitude power-loss events, and perhaps also the pitot problems, are caused by convective clouds containing a very high density of tiny ice crystals. The point I was making in my post is that the well-known Rosemount Icing Detector ( http://www.eol.ucar.edu/raf/Bulletins/B24/iceProbe.html) does not detect ice particles, since it is designed to detect super-cooled liquid water droplets. BEA says that the presence of liquid water at -40° C is unlikely, and must necessarily have been limited to small quantities. If there was liquid water in sufficient quantity to cause icing problems, I think it is highly improbable that it would have been missed by the ice detector(s). If your scenario was valid, how could they ever detect ice?

I don't think that you are correctly describing the cause of the ATR accident at Roselawn. IIRC, the theory is that the airplane encountered unusually large super-cooled droplets at relatively low altitude. Due to the large droplet size, the area of ice accretion extended beyond the deicing boots. While the ice on the boots is periodically shed by inflating the boots, the ice aft of the boots remained and formed a ridge on the upper surface of the wing just aft of the boots. This is just from memory, feel free to correct me. I don't see any connection to the functioning of an ice detector.

lomapaseo

26th Nov 2011, 13:40

mm43

Re post # 514
The "relative" part of your comment can only be answered subjectively on the basis that a small ice accretion will last a short time (seconds) and a larger one will last relatively longer, but still in seconds

OK it's seconds then:ok:. Since we are talking about AF447 the time to clear the ice and reestablish valid pitot readings is iimportant.

My feeling is that this time would not be expected to be much different than all the other inflight incidents, in other words seconds

Lyman

26th Nov 2011, 16:23

Dozy (cc Old Carthusian)

Re: Attitude and "climb".

Dozy, The Nose was actually Low by four degrees v/v flight path, so no goalposts were injured in the making of this post. The a/c was "climbing" nose low ........-4 degrees. The auto pilot will trip out with a NOSE Down of 9 degrees, so I offer this theory, try it on.

For thirty seconds prior to loss of Auto Pilot, the VS select shows 5000fpm down.

This value would trip the a/p due excessive Nose Down, so it is rejected by the FCM. Select/Reject for thirty seconds. NO ICE. The a/p eventually latches the excess (+9) value, and trips out at 2:10:05. NO ICE. As the a/p has tripped due to excess control (past limit), the LAW remains in NORMAL. For an additional ten seconds, the a/c is subject to turbulence that duffs the probes, simultaneously. NO ICE. With discrepant normed Speeds, the a/c degrades now into AL2 NO ICE. It is at this point The PNF announces, "We have lost the speeds, Alternate Law..." NO ICE.

For an updraft to lift this a/c (at the recorded rate) is remarkable. It also screws with the AoA vanes. As the Pitch decreases, the vanes read increasingly higher. PITCH at this point is not the a/c's problem, but AoA is. This is why the a/c initially did not "climb" with PF's aft pulled stick. The elevators were trying to catch up with the airstream, for the better part of ten seconds.

At the point that the elevators got back into the "loop" the climb was already breathtaking, and virtually unnoticed in the cockpit.

Were they in the cell? I believe they were......

EG: Can an aircraft climb rapidly with a Pitch displayed as 'Normal'?

Boy Howdy.

grity

26th Nov 2011, 17:45

Machinbird, All that you probably ever wanted to know about spring failures can be found here:thanks fore the link ,

if worn is the wrong word, then sorry I meant relaxation.... is it one spring for pitch or one for push and one for pull into the sidestick??? If I remember well gums has shown a diagram of the energy vs move of the sidestick in thread 3(?) with a kink in the line, so mayby there works more than one spring in each direction

Lyman

26th Nov 2011, 17:55

Read me a little closer, Doze. Whose elevator? Whose VS select?

A/P. Not PF. What are those oscillations in VS (SELECT)?

DozyWannabe

26th Nov 2011, 18:00

Lyman, my red line coincides with timestamp 02:10:11 - the A/P has been out for 6 seconds, and the PF sidestick trace has been registering significant nose-up inputs from the PF's sidestick since 02:10:05 (i.e. those same 6 seconds).

mm43

26th Nov 2011, 18:17

grity;

Back in AF447 - Thread No.5 Post #229 (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-12.html#post6568978) A33Zab posted a graphic of the SideStick and a brief description.

Here's the same graphic again.

http://i474.photobucket.com/albums/rr101/Zab999/SideStick.jpg

Lyman

26th Nov 2011, 18:18

I think this thread is behaving worse than 447.

@2:10:08 "I have the controls". The climb started well before the PF had the stick. And VS SELECT was oscillating independently. Notwithstanding the aircraft captured 5000fpm instantaneously?

Pitch and VS (actual) track together? The graph is eating Wheaties, or was put together by Michael Mann.

grity

26th Nov 2011, 18:55

how works the mechanik of the rod-spring at the kink of 6.5 mm ??? (1/3 pull)
that is +/- the pitch aerea the PF hold the stick during the climb....

also from A33Zab:

http://i474.photobucket.com/albums/rr101/Zab999/SSForce.jpg

mm43

26th Nov 2011, 20:41

Lyman;

I've expanded some of the FDR traces and in the case of the Pitch attitude one have added the Elevator and Stabilizer positions (inverted) for easy comparison. Immediately above is the Normal acceleration trace.
http://oi44.tinypic.com/1zr2m2p.jpg
My summation is that the aircraft responded very well to the PF's inputs (as represented by the Elevator and Stabilizer positions) after the A/P hand-off, but just prior to, the turbulence had created a pitching moment that didn't correlate with the vertical speed. Hence the A/P disconnect.

The UAS was a secondary.

EDIT: Patently not true, as the RTLU was locked at 02:10:04.5 in response to the ADRs rejecting the two speeds recorded, or more precisely the Mach value of one of them. The two airspeeds recorded were still valid at this time; however, a false value point is present in the recording of the Mach. The low sampling frequency makes it impossible to determine the duration of the disturbance in the measured values; however, it is likely that it corresponds to when monitoring was triggered. (BEA Interim Report No.3)The UAS was the primary reason for A/P disconnect.

EDIT #2: An interactive version of this graphic with vertical/horizontal Cross Hairs and additional time marks and scale is available here. (http://countjustonce.com/af447/af447-fdr-data-xhair.html) You can also expand your browser page using Ctrl + and return to normal with Ctrl 0.

Lyman

26th Nov 2011, 20:55

Yes, I know. Thanks.

Machinbird

26th Nov 2011, 21:11

how works the mechanik of the rod-spring at the kink of 6.5 mm ??? (1/3 pull)
that is +/- the pitch aerea the PF hold the stick during the climb....

Grity, the way this is commonly done is two springs, one for the initial slope and a second that has a certain amount of freeplay to generate the steeper slope.
One of the guys with maintenance experience will have to tell us the specifics of the A330 feel system, but if you will note, there are two spring cartridges in the pitch channel. This may be a redundant design with two identical sets of spring cartridges, or a non-redundant design with one spring cartridge doing the first slope, and the second cartridge (with built in freeplay) doing the second slope. Each cartridge would contain at least two springs (nose up and nose down).

DozyWannabe

27th Nov 2011, 02:05

...but just prior to, the turbulence had created a pitching moment that didn't correlate with the vertical speed. Hence the A/P disconnect.

The UAS was a secondary.

Are you disputing the BEA's findings?

At 2 h 10 min 05, the sudden drop in the measured airspeeds, likely due to the obstruction of
the Pitot probes by ice crystals, caused autopilot and autothrust disconnection (the thrust was then locked) and the change in the flight control law from normal to alternate. The presence of turbulence, shown by the inputs by the AP to control the roll in the previous seconds, led on disconnection to the airplane beginning a roll to the right of up to about 8°.

According to the BEA, the turbulence was responsible for the roll, but the A/P disconnect was initiated by UAS - this makes sense as moderate turbulence should not be enough to cause A/P disconnect.

@Lyman - The graph comes from BEA Interim#3 page 111 - I just did a screengrab and moved the relevant traces next to each other (vertical movement only - no horizontal) in the same way I and airtren have done before so that the graphic does not take up more vertical space than it needs to. This is basic pixel-pushing of the kind I've been doing since I was 11 years old. You can print that page and draw the line with a ruler and it will tell you the same thing. I've done it again here with the sidestick trace included just so you'll know I'm not fiddling you:

http://i1088.photobucket.com/albums/i331/turricaned/fdr-pitch-vs-pf.png

The pitch up and climb was initiated by the PF's sidestick input - whether he manipulated the controls before, simultaneously or after he said "I have control", that stick was halfway back for 2 or 3 seconds before the aircraft started climbing.

Lyman

27th Nov 2011, 03:16

Doze. Check your RED VERTICAL LINE. You will notice it is at 2:10:10.

The initial PULL UP by the PF (F/O) is at 2:10:07. The START of the RED STICK TRACE. In the seconds before a/p disconnect, the Nose dropped 4 degrees, and the a/c was climbing at 1000fpm. It is this AoA increase that dropped her speeds (all three) beyond the 30 knot/second threshold, and caused the speeds loss: but after the disconnection. BEA re: ICE is "LIKELY" wrong.

Of Importance is what the a/c has done prior to 2:10:05. BEA wrote at first that the cg was at 37. They changed that later, in a follow on, to 28. If I had bet my life on their written data, I'd be dead.

DozyWannabe

27th Nov 2011, 03:36

I had it at 2:10:11, but whatever...

You can't keep bashing away at this, the data is there. The A/P commanded nothing untoward, the pitch-down and roll was induced by turbulence and the climb was as a result of sidestick input.

The *very* start of the PF's sidestick trace is unfortunately obscured by the data points of the PNF's sidestick trace. The "zipper" could be many things - I suspect it's wonky data (it looks too uniform to me to be anything else), but, for the sake of argument it could alternatively be pitch corrections made by the autopilot in MANAGED mode to maintain assigned altitude in turbulence. In any case, the vertical speed and altitude traces show that there is no major deviation from assigned altitude during the time it is happening, and even *if* the autoflight was commanding one of these corrections when it tripped out (which doesn't tie in with the trace - at 2:10:05, it's commanding 0 ft/sec), then a small pitch correction is all that is needed to bring the nose back up. But this is not what the PF does - he pulls back and holds it there for several seconds and commands a climb.

The CG readings given in the interim report #3 (which was the first issued with actual data) are 27.5, 28.7 and 29.1% MAC respectively. Where do you get the other number from? If it's from an earlier report it would have been an estimate because they had no data - hardly their fault.

Lyman

27th Nov 2011, 03:45

2:10:11 or "WHATEVER"? Are you kidding? Your line is off by six seconds, and your time index is completely WRONG. Check mm43's graph. Do you dispute that the a/c had dropped 4 degrees in PITCH as she climbed (ACTUAL) at 1000fpm? Look a little closer. Please remember that to climb with nose low requires more vertical than the actual rate of the airframe. This is what duffed the three speeds simultaneously, and by the same value, imho. A computer computation of the discrepancy would result in the descent rate due PITCH to be overlimit. This bounces the A/P. The speeds follow.

DozyWannabe

27th Nov 2011, 04:09

mm43's graphs are from a different page than mine, and have had more editing done to them, but for whatever reason, unless i'm reading the graph completely wrong, the pitch attitude only dropped below 0 degrees at 02:10:03 and was on it's way back up at 02:10:05 (AP disconnect - though mm43 has it at approx 02:10:04.7 - perhaps he's privy to better information than me). This has all the hallmarks of a minor turbulence encounter, but the climb proper is started between 02:10:10 and 02:10:11 *as a result of the pitch up ordered by the PF's sidestick*. On this the graphs do not differ.

mm43

27th Nov 2011, 07:00

Dozey;

1.. The RTLU was locked at 02:10:04.5, and
2.. The aural autopilot disconnection warning (cavalry charge) was heard at 2:10:04.6.

We are "splitting hairs", but they're all that's left to split!

DozyWannabe

27th Nov 2011, 13:27

@mm43

That's fair enough, but I don't see how that contradicts what the BEA are saying about UAS being the reason for autopilot disconnect as opposed to turbulence. Even if that is disregarded completely it doesn't support the hypothesis that an autopilot that disconnected between 02:10:04.5 and 02:10:05 ordered a climb that did not begin until 02:10:11 (not that said hypothesis is one of yours).

As I said, it looks to me like the autopilot disconnected in the middle of one of it's turbulence encounter compensation inputs when the nose was on the way back up (i.e. not on the way down as Lyman hypothesises), but the real beginnings of the zoom climb are clearly ordered by the PF's sidestick input.

On autopilot disconnect, the aircraft locks thrust at the last setting (as you say) and holds the pitch where it was being commanded at point of disconnect (in the middle of the correction) allowing time for elevators to return to neutral, which is borne out by the graph settling at 2 degrees nose up for a couple of seconds (just short of the 3.5 degree pitch it was holding before) before the nose-up commands from the sidestick begin to take over and progressively increase pitch attitude to 11.5 degrees nose up.

Machinbird

27th Nov 2011, 14:58

Just my personal opinion, but if we really want to get to the core of the nose up control input, I think we have to look at PF's control problem.
Something along the lines of what he did versus what he should have done. If Grity's chart of control motions is accurate (and not overly interpolated/smoothed) then PF used an inappropriate control strategy.

Having never flown an Airbus, I'd like to hear from those that have, regarding control strategies used in Normal Law, and Direct Law.

For example, from the videos recently posted, it appears that the majority of Normal Law control inputs are pulses away from neutral, but sometimes in two axes simultaneously.

Is direct law also done with pulses, or is it a continuous input? (I have to assume that Alt2 Law experience with mixed control modes is very unusual/scarce.)

As I mentioned in an earlier posting, Grity's chart shows a lot of diagonal control inputs along the NE-SW axis. I really think PF was having difficulty separating his lateral inputs from his pitch inputs, probably due to an improper stick grasp.

I'm posting grity's image again below for convenient reference.
http://i.imgur.com/X3HIW.png

rudderrudderrat

27th Nov 2011, 16:23

Hi Machinbird,
Is direct law also done with pulses, or is it a continuous input?
In ALT Law, it has to be flown like any conventional aircraft in roll. The control input has to be held against any roll tendency until the load is trimmed out. Since there is no aileron trim, you have to use rudder in order to be stick free. It would appear that PF was attempting to fly the aircraft using large pulses when he was in roll direct.

(I have to assume that Alt2 Law experience with mixed control modes is very unusual/scarce.)
Most of my ALT LAW practice in the sim was at low level.

TTex600

27th Nov 2011, 16:59

Machinbird, after taking a second look at grity's graph, and assuming that the data contained therein is correct; I make this conclusion - Something is lying to us.

The graph shows an initial move out of center, followed by three complete left/right reversals including two up/down movements in 11 seconds. That amount of movement in that time frame is IMO almost impossible based upon my time spent handling the A320 SS. In other words, the Bus SS is not a cheap video gamer's joystick. The spring loading and damping would make that amount of movement quite difficult.

Secondly, that amount of movement would be on a scale never before ordered by the PF prior in his career. If I have followed the timeline correctly, the aircraft was relatively stable when the a/p and a/t dropped off line. This graph indicates that the PF began this series of SS movements within two seconds of a/p a/t disconnect. The aircraft does not appear to have been in an upset at that time, so what caused the PF to almost immediately begin a series of spastic SS movements? These movements are not compatible with normal hand flown inputs.

We are left with resolving a series of over exaggerated control inputs with a relatively stable aircraft. Either the data is corrupt, or the PF made completely inappropriate control inputs, almost impossible control inputs. ...........OR, the PF was just hanging on. Or, the aircraft was upset more than I realized from reading the data.

Regarding control strategies, I find that small deflections, held for longer time spans work better than short higher magnitude deflections.

FWIW, the 320 requires very minor control inputs when flown a/p, a/t, f/d's off.

gums

27th Nov 2011, 17:14

Salute!

I believe the stick inputs being awry due to spring failure or degradation is a red herring. The pilot commanded and the system responded best it could with screwed up speed and disregard for AoA limits.

The chart of the breakout forces was a surprise to me and I had missed that if posted before. The breakout force is lots lower than the Viper. Ours was 1 lb for roll and 1.75 for pitch. Secondly, the gradient for max command is lots steeper. For example, ours was about 7 pounds to command 2 gees. Then the curve got steep and a 9 gee command was about 31 or 32 pounds.

Secondly, my understanding from looking at the roll laws is the roll command works the same in "alternate" as in "normal". The only difference I see is the max roll angle allowed in "normal", not the command, but actual body-referenced roll angle. So what I see is what I was used to - let go of the stick and the roll command is zero deg/sec. Am I missing something?

As the Bus drivers are now finding out, there are "hidden" aspects of the control laws. Same as we had in the Viper. For example, no stick pressure in roll and zero roll rate command. Not so fast! Turns out that there are flight dynamics which are not completely corrected for. Look at the pic on my profile bio. With that LEF up I had to apply almost full left stick to stay wings level ( it was a control surface limit, and the engineers told me that I only had about a pound or two of authority or would have had to bail). The zero roll rate "law" didn't work. We also saw this when dropping a heavy store from one wing. We had to apply aileron pressure to stay wings level on the pullout and we had thot the jet would maintain zero roll rate. Same deal with allowable control surface deflection.

Only thing that puzzles me is the pilot having to apply roll in the first place. Could be a spoiler or aileron wasn't moving correctly, and a determined manual input was required to override the deflection limits. Same as I had to do with the LEF failure. And remember, control surface movement rates and such use dynamic pressure for "gains". What does the system do when dynamic pressure is deemed unreliable by the system?

later,

Organfreak

27th Nov 2011, 17:17

@TTex600:
I'm going to repeat my possibly stupid questions that I asked the other day:
1. What about a broken longitudinal transducer?
2. Were all four transducers found?
3. Have they been verified as working properly at the time of the accident?

If there were to be such an (outrageous) finding, that one was broken, this might explain the unexplainable.:8

Lyman

27th Nov 2011, 17:23

Simply put, The Pitch was below cruise for nine seconds from 2:10:00.

It reached its lowest value (4.5 degrees ND) just as the a/p tripped out.

As it increased, the aircraft was still in descent.

At 2:10:07 PF input back stick, after the a/c had started to climb.

The airframe was out of phase v/v ascent/Pitch for nine seconds.

The PF inherited an airframe in phugoid oscillation.

How many times had PF been handed an a/c out of autopilot? As many as he had landings logged, most likely. His stick work is a copy of the two vids grity has posted, perfectly acceptable, when approaching to land.

His elevators were following the airframe at first, from his display.

The autopilot could not keep up with the turbulence, and tripped out. Out of this trip came airflow that sensed airmass inconsistent with the airspeed prior to its disturbance, and so the airspeeds were lost.

In two seconds, the handling pilot was given an impossible task. True to form, just as the Airbus got into hot water, it changed the "rules", and took a powder. So now, the Pilot has a very long list of things to learn, or die. Not the least of which is to acclimate to a Stick that has morphed into a goblin in ROLL, and a PUSSYCAT in PITCH. Has he trained for this?

I think NO. As someone has said here, put a single engine pilot in a twin, and pull an engine at liftoff. What are his chances? Not good.

At 2:10:00, the a/c started a phugoid. Was it speeds? No, I think airmass related. Had it been speeds, I think the engines would have been throttled, and they remained at cruise level. And if not speeds, then ICE is not a player.

For good or ill, in my opinion, this flight was out of control when the Pilot's input doubled PITCH, at 2:10:11. One can insist it is complex, and it may be, but had PF had a current Attitude display, and listened to PNF......

DozyWannabe

27th Nov 2011, 17:36

The other explanation is adrenalin. The "startle response" is quickly gaining currency as the biggest potential killer in line flying. With Colgan 3407 you have two tired pilots, one of whom is shocked into pulling up into a stall when the stall horn sounds. West Caribbean 708 had a Captain who was convinced he had a double flameout and concentrated on that, pulling up all the way into the ground. Birgenair 701 had a captain who focused on the initial overspeed warning to the exclusion of all else and pulled the aircraft into a stall.

Then you have success stories - US Airways 1548, BA038, Aloha 243 and United 232 as a few examples where in all cases the crew kept calm, overrode their internal panic switches and found a way to resolve things.

Whether you're flying, driving, doing your job or whatever - after doing it for some time things become routine - if something happens to break that routine then you have to keep your head about you and logically focus your way out of an event, but you've got millions of years of evolution behind the human brain which triggers a "fight or flight" response. Sometimes it works to the good and people have found almost superhuman resolve in themselves to get the job done, but sometimes it does not - people freeze or try random combinations of things they half-remembered in training or heard on the line with tragic results. It's all part of being human and training must address that.

Remember that the this was the PF's first day back on the job - he had just ended his holiday in Brazil and his wife was down the back - if there's a situation more conducive to be startled and try absolutely *anything* to keep that aircraft at the assigned cruise level, I can't think of it.

@Lyman - a phugoid cycle is something that happens over longer periods of time than the turbulence encounters the aircraft was experiencing. Remember JAL123 and UA232 - with dead flight surfaces the cycles happened over the course of about a minute and a half, so it was about 45 seconds of slow climbing followed by about 45 seconds of slow descent. The turbulence encounters and autoflight corrections we're talking about here were on the order of a few seconds at most. The pitch attitude was increasing at A/P disconnect as a result of one of those corrections, and stopped short of 4 degrees nose up because of the A/P disconnect. The elevators don't remain in the position they were in when A/P disconnects, they are set to match the last requested flight path angle, which was about 2-3 degrees nose up.

mm43

27th Nov 2011, 17:48

@Dozey;

You are right regarding the A/P disconnect. The RTLU locked because the ADRs disagreed, and I have made an edit to post #526.

I am not going to get into the argument regarding the cause of the climb, other than to reiterate that the elevator and THS responded to the PF's SS stirring and the aircraft pitched into the climb almost immediately at 02:10:09.

Lyman

27th Nov 2011, 18:15

So, a robust updraft. Very warm, sufficient to corrupt Mach value? Unless the increase in VS is due baro, then it is airmass. The point is, the a/c was out of phase, and the pilot was given an a/c that was climbing with the NOSE showing low. His Pull was additive to an input made by AutoPilot("STALLSTALL"), and the confusion began. Yes, he should have been "ready", and managed a better get than he did.

The problems encountered were not complicated, but the timing was.

TTex600

27th Nov 2011, 18:27

How many times had PF been handed an a/c out of autopilot? As many as he had landings logged, most likely. His stick work is a copy of the two vids grity has posted, perfectly acceptable, when approaching to land.

Those two videos show but one pilots control technique. I bet you a cup of coffee that they could have both kept their hand off of the SS and the end result would have been the same. In other words, the Bus doesn't require that kind of SS input in/on final. The pilot was working too much. Those little corrections he made were not likely necessary because the Bus will stay where you left it, and/or return to where you left it without any input. Once you learn too let it correct itself in roll on approach, you find yourself making very few roll inputs.

DozyWannabe

27th Nov 2011, 18:34

...and the pilot was given an a/c that was climbing with the NOSE showing low.

It depends on your definition of "climb" - it looks like the tail-end of a small pitch correction due to turbulence that would have ended maybe a second later than it did due to A/P disconnect - the aircraft's pitch attitude was increasing, but all the evidence suggests it was not about to climb significantly, it was simply trying to regain the assigned flight level and pitch attitude.

The pitch attitude was lower than it should have been at A/P disconnect, but it was a matter of 2 degrees - it briefly settled at 2 degrees nose-up after A/P disconnect. That kind of difference is barely noticeable on a modern PFD, let alone steam gauges - it was two points in the blue. It certainly does not require half back stick to correct, which is what the PF did.

He may have mentally been correcting for the bump they felt at disconnect, even though the autopilot was ahead of him - seeing the ADI pointing into the brown for a second might have been a shock. This is where Human Factors comes in. For those who aren't pilots but can drive, would you say you take more care when driving with your loved ones in the car than you do on your own? I know I do. See someone driving erratically or dangerously when you're on your own and it's tempting to just go past him. Do it with family in the car and I'm inclined to leave him to his own devices and back off because it's more than just me at stake. Professional airline pilots live with the knowledge that there are hundreds of people behind them who are depending on their skill - that's part of the job and why I respect them so much. If you're flying a jet that nevertheless has family on board? All of a sudden instincts start to cloud rationality and there's an emotional pull there too (which is why the Aeroflot crash with the children in the cockpit is to my mind the saddest aviation story I've ever heard).

His Pull was additive to an input made by AutoPilot("STALLSTALL")

No - the autopilot disconnected at 02:10:04.6 as mm43 has it. PF inputs begin at approximately 02:10:07 (by your own statement) and the first STALLSTALL does not sound until 02:10:10. There is no "additive input" to the autopilot from the sidesticks.

The problems encountered were not complicated, but the timing was.

It happened in a matter of seconds, no doubt - but the control inputs the PF made were completely disproportionate to what was required from the outset.

Lyman

27th Nov 2011, 19:06

At long last I believe we are closing in on what may be a lay solution. As such, it is of little value, save for some sort of truce. It also may be as close to a resolution as anyone gets, including BEA.

2:10:04.7. A/P quits. Here, the Nose is 4.5 degrees lower than what it should be. With MASTER CAUTION and CAVALRY CHARGE, the PF is brought up short, from whatever his status was, re: SA. A quick glance at PFD, if not already looking, shows NOSE LOW, and VS in descent, perhaps 500fpm. 2:10:07, and he inputs back stick with a ROLL LEFT.

The a/c has started to climb at a/p quit, and there is not a reason to doubt his input causes sufficient NOSE UP to trigger STALLSTALL. His next inputs are NOSE DOWN, so he 'gets it'. The rest depends on what he sees on his screen, feels, (The g is <1 until after his input), and decides. (Hears?).

If there is mitigating data, sufficient to establish his inputs were based on data not seen here, I propose there is a 50/50 we will never see it. That is the way of the world; life is harsh, and seldom "fair".

At long last the discussion is where it should have been from the outset.

With NOSE DOWN, I would submit that it takes a healthy Updraft to cause such an ascent as we see just prior to a/p loss. Was it sufficient to cause the accident? Was there ICE? or only variable TEMPS and a bumpy airmass?

It's been a real slice.

DozyWannabe

27th Nov 2011, 19:15

No Lyman, the nose was on the way *back up* when the A/P disconnects. The PF may have *seen* the brief turbulence induced nose-low attitude and might have been trying to correct for it but there was no major updraft. The aircraft climbed because the PF's response was incorrect - in a perfect world he would have waited a few seconds to get a feel for what the aircraft was doing before trying to join in.

Hypothetically speaking - put yourself in the PF's position. You have not been trained in manual handling at altitude, most of the 2,000-odd hours on your flight log have been completely uneventful (and not to mention automated), you've been on holiday with your wife and you're now returning home with her in the passenger cabin. The Captain has nominated you as the relief pilot despite being the junior flight crew member on board - you're on top of the world. Suddenly you get an autopilot disconnect alarm followed by an alarming bump in which the ADI showed the nose dipping below the horizon for a second or two. What do you do?

We'd all like to think that we'd be calm and rational and behave as if this was any other flight - but all of a sudden one of your best days has turned into your worst nightmare.

Machinbird

27th Nov 2011, 19:25

my understanding from looking at the roll laws is the roll command works the same in "alternate" as in "normal". The only difference I see is the max roll angle allowed in "normal", not the command, but actual body-referenced roll angle. So what I see is what I was used to - let go of the stick and the roll command is zero deg/sec. Am I missing something?

Gums, What you wrote is correct for Alt1 Law but not for Alt2 Law. Alt2 Law is roll direct, i.e. aileron deflection proportional to stick deflection.

Organfreak, There is a reason each transducer on the stick has its own control mechanism, it is redundancy. That redundancy undoubtedly carries through in the software design of the "Bus" so that it can recognize a bad transducer, but don't ask me details because I don't know. At this point, all I know is that it would be extremely out of character not to cover that potential problem.

but the control inputs the PF made were completely disproportionate to what was required from the outset.
Dozy, I agree with this summation

or the PF made completely inappropriate control inputs, almost impossible control inputs. ...........OR, the PF was just hanging on
TTex, he was essentially reversing his roll input every two seconds. Maximum control input pretty well corresponds to maximum wing down. Just hanging on is probably as good a description as any. Over time the intensity of his inputs begins to decrease as he began to get the "touch".

PF was definitely driving a lateral oscillation by means of his excessive control inputs. This period where he is struggling with roll is when the aircraft became committed to a nose up attitude.

So why didn't PNF at least coach him back on altitude? All I can conclude is that both of their scans were in the toilet. "GO Down" , YGTBSM. :yuk:

In ALT Law, it has to be flown like any conventional aircraft in roll. The control input has to be held against any roll tendency until the load is trimmed out.
Thanks Rudderrat. I just wanted to be sure. No lateral pulses then in Alt2.

Organfreak

27th Nov 2011, 21:03

Machinbird wrote:
Organfreak, There is a reason each transducer on the stick has its own control mechanism, it is redundancy. That redundancy undoubtedly carries through in the software design of the "Bus" so that it can recognize a bad transducer, but don't ask me details because I don't know. At this point, all I know is that it would be extremely out of character not to cover that potential problem.

Thanks for addressing my question/speculation. I had assumed, apparently wrongly, that there was one TD for each direction of stick travel. Your contention that they are redundant rings true. Damn, and here I thought I'd come up with The Answer. :O

A33Zab

27th Nov 2011, 23:56

2 identical rods are installed in each SS.

http://i474.photobucket.com/albums/rr101/Zab999/ArtRod.jpg

Machinbird

28th Nov 2011, 03:33

A33Zab, Thank you for posting the drawing of the spring rod (or cartridge).
It appears to be an elegant design in that the same springs work in compression during both extension and compression of the cartridge. Additionally, it appears that one of the springs is of a non-linear design and does not follow Hooke's Law. :ok:

Machinbird

28th Nov 2011, 04:16

The PF inherited an airframe in phugoid oscillation.
Lyman, not really possible in an Airbus in Normal or either of the A330 Alternate Laws. The flight control system, by managing g, sets a stable flight path on the average.

A phugoid oscillation is a relatively slow oscillation at ~constant AOA, where potential and kinetic energy trade back and forth, but that isn't the way the 'Bus flight control system works.

HazelNuts39

28th Nov 2011, 09:01

Back in june i posted the A330 phugoid ( http://www.pprune.org/6545690-post596.html) that results when the system in normal law enters high AoA protection and maintains AoA equal to alpha-prot (as in the TC-JDN airprox incident).

grity

28th Nov 2011, 10:29

Machinbird A33Zab, Thank you for posting the drawing of the spring rod (or cartridge).
It appears to be an elegant design in that the same springs work in compression during both extension and compression of the cartridge. Additionally, it appears that one of the springs is of a non-linear design and does not follow Hooke's Law. I like this forum very much for such a design-picture, thank you A33Zab

but machinbird I am shure, there is a smal mistake in the drawing both springs will work in hook´s law, but the bigger(purple) spring IMO is a few mm shorter than shown, there is more space on the yellow side..... so first you press the weaker green spring and later you have to ad the hooks force of green and purple

so we have a redundant system with two catridges, well gums it can be a herring but if one of the green spring was broken then I am shure this is not easy to detect on the taxiway, the SS feels full ok for left/right/up+down and only the force for 1/3 pull is half of normal........ remember we search for the smalest possible defekt who can explains the action of the PF shown on the FDR!

If Grity's chart of control motions is accurate (and not overly interpolated/smoothed) then PF used an inappropriate control strategy. the basis of my chart was the datas shown in interimreport3 s.29 (F/O pitch and roll command position) I used 2 valus/sec put both together for 2D and smoothed a splinline over it.... so it is little interpolated but not much,

it looks not as he has made pulses ore something like this in this time.....

much more interesting for the control strategy is if you overlay the sidstickway with the left/right asceleration, which was also left-right-left-right-left in this 10 sec with values +/- 0.1 g

Machinbird

28th Nov 2011, 14:58

but machinbird I am shure, there is a smal mistake in the drawing both springs will work in hook´s law, but the bigger(purple) spring IMO is a few mm shorter than shown, there is more space on the yellow side..... so first you press the weaker green spring and later you have to ad the hooks force of green and purpleGrity, it is quite possible that you are correct and there is actually some spring freeplay that is not shown in the drawing. It is also possible to make a non-linear compression spring by wrapping the spring in such a way that the adjacent loops make contact in only a portion of the spring and thus effectively shorten the active portion of the spring. The guys who make springs can do it very consistently, even with 50 year old equipment.

Machinbird

28th Nov 2011, 15:14

HN39,
Thank you for the reminder on how you cannot forget completely about the phugoid on an Airbus in Normal Law.

In the AF447 case, the phugoid did not apply since as soon as the AP dropped, it was not in Normal Law. And before the AP dropped it was not in high AOA protection.

HazelNuts39

28th Nov 2011, 16:03

In the AF447 case, the phugoid did not apply since as soon as the AP dropped, it was not in Normal Law. And before the AP dropped it was not in high AOA protection. Agreed entirely. My intent was no more than to provide an illustration to your post #553.

HazelNuts39

30th Nov 2011, 19:59

Does anyone know what the parameter 'TLU Position (DA)' shown on page 112 of IR no.3 (English) stands for? Since with 1300 recorded parameters it is inevitable that the report must necessarily involve a selection of the relevant parameters, showing this parameter means that somebody thought this one might be relevant.

On page 89 we read at 02:10:18: "The ‘TLU 1 availability’ and ‘TLU 2 availability’ parameters become NOT AVAILABLE" and the traces of these parameters are shown on page 107. Since this time roughly corresponds to the end of the initial 10 second speed monitoring process, I thought that TLU could stand for RTLU (Rudder Travel Limiter Unit). But what then is TLU position?

mm43

30th Nov 2011, 21:17

From page 40 -
* the loss of the normal law between 2:05:10 and 2:10:06. The position of the rudder limiter, set by the rudder travel limiter unit (RTLU) is locked at 2:10:04.5 and this function is recorded between 2:10:17.5 and 2:10:18.5.
NOTE: The report uses "stuck" instead of "locked".

From page 89 -
* 2 h 10 min 18 - The ‘TLU 1 availability’ and ‘TLU 2 availability’ parameters become NOT AVAILABLE.

From page 112 -
* TLU 1 and TLU 2 parameters repeated, and at 2:10:08 the Side Slip from IRS becomes ACTIVE.

I suspect this is related to the Yaw Damper.

I've previously commented that the Rudder Pedal demands (up to RTLU limit) had the Yaw Damper output algebraically added.

HazelNuts39

30th Nov 2011, 22:08

The french text is quite clear:
La position du limiteur de débattement de la gouverne de direction (RTLU) se fige à 2 h 10 min 04,5 et l’indisponibilité de la fonction de limitation de débattement de la gouverne de direction est enregistrée entre 2 h 10 min 17,5 et 2 h 10 min 18,5.
What about the changes of 'TLU position' before 02:10:04.5?

mm43

1st Dec 2011, 08:20

I translate the original as follows:-

"The position of the rudder limiter of the rudder (RTLU) is frozen at 2 h 10 min 04.5 and the unavailability of the rudder travel limiting function is recorded between 2 h 10 min 17.5 and 2 h 10 min 18.5."

Do you believe that the wording used in the French version effectively means that, "The RTLU is locked at the allowable deflection for the last valid Mach speed"? If so, that statement matches the operational description of the device.

In respect of the earlier variations; would seem that there were some short-term Mach fluctuations prior to the defining one.

HazelNuts39

1st Dec 2011, 08:53

Hi mm43;

Thanks for sharing my curiosity. I think your translation is perfect and, yes, I believe it means what you say (i.e. the 'freeze & latch' corresponds to the CAS & Mach at 02:10:04,5). The "short-term Mach fluctuations prior to the defining one" must have been pretty large, and must have come from a different source than the recorded CAS & Mach. Then there is the value itself, which doesn't correspond with IR #2:
1.12.3.5.5 Examination of the Rudder Travel Limiter Unit (RTLU)
The RTLU was found in its place in the fin and disassembled. An examination was performed at the manufacturer’s and showed that it would allow travel of the rudder measured as 7.9° +/- 0.1°. As an example, at FL350, this travel is obtained for Mach 0.8 +/- 0.004, corresponding to a CAS of 272 +/- 2 kt.
Note: the maximum travel of the rudder is calculated in relation to the airplane configuration, its speed and its Mach number. This travel can be commanded between 4 degrees and 35 degrees.

mm43

2nd Dec 2011, 07:38

Hi HN39;

Thanks for the reply. I will answer the PM in due course.

Looking at the Yaw Damper trace, I believe that the maximum rudder angle allowed by the Yaw Damper (+/-4°) was not exceeded, but whether the damper was acting correctly is another matter.

The DA displayed by the TLU is rather puzzling. Perhaps the TLU angle doesn't represent the actual rudder angle, but there doesn't seem to be a valid reason for that to happen. As the AMM doesn't shed any light on the situation, we may just have to wait for the BEA to explain exactly what was happening.

As you have already pointed out, if the deviations shown in the TLU traces are to believed, where did this Mach data come from?

Having searched the various definitive sources and found nothing, I reverted to the Cathay Pacific notes originally compiled by Andy Tracey and came up with this for Yaw (http://countjustonce.com/a330/a330-flight-laws.html#yaw) and another for ALT-2 (http://countjustonce.com/a330/a330-flight-laws.html#alt2).

EDIT : Basic control schematic
http://oi40.tinypic.com/2hncsad.jpg

roulishollandais

3rd Dec 2011, 16:50

@Lyman
"His Pull was additive to an input made by AutoPilot"

Forget !
Impossible . :ok: You know : BZ said : pilots are only housekeepers, cow-boys or fools ! It would be a real algorithm bug in AB philosophy to add a computer and a human input !:=

VNAV PATH

3rd Dec 2011, 18:15

BZ , himself , a cow boy , cutting telepheric lines in Alps with a Mirage 3 .

Short memory Bernie ! :ugh:

Organfreak

3rd Dec 2011, 18:44

For the uninitiated, is that post supposed to mean anything in particular? :ugh:

Zorin_75

3rd Dec 2011, 20:02

For the uninitiated, is that post supposed to mean anything in particular? In the 60's Bernard Ziegler's F84 collided with the line of a cable car in the Alps, killing 6 people. It's routinely dragged out to serve as proof that anything Airbus is inherently evil. Link (news.google.com/newspapers?id=QTVYAAAAIBAJ&sjid=TPcDAAAAIBAJ&pg=7179%2C6821564)

Organfreak

3rd Dec 2011, 20:28

@Zorin:
Ah! The light dawns. Thanks!

Lyman

3rd Dec 2011, 22:05

Bon Temps Rouler....

ne plus plus. At handoff, the airframe was rotating up, as the ascent diminished, (The PITCH on PFD showed 0, four degrees 'low'). My surmise is that the PF's initial NU input created an unwanted PITCH moment (Normal Law, protected), and that caused the STALLSTALL, (the first WRN, a 'transient'). Still sufficient for the highest g accel, though.

Lonewolf_50

5th Dec 2011, 14:36

Lyman, for what it's worth ...

IF you are a pilot flying on instruments,
AND
you (or your friend HAL) make a pitch input that causes the nose to go up ...
AND IF the nose goes higher than you intended it to to go when you or HAL made that input
THEN
you use your hand on the flight controls to make an immediate counter correction that is usually accomplished in two parts (particularly if your task is to fly smoothly in order to keep your passengers as comfortable as you can)

a) first you stop the pitch rate (and you watch all of this on your attitude indicator/AH) and
b) make a second correction to return the nose to the pitch you actually desire for the flight conditions or performance you wish to complete your mission, or the segment of the mission you are on.

As an adjunct:
IF during this process you find your aircraft to be rolling beyond the AOB you desire (which I think would be "wings level" or "0" degrees AOB)
THEN you use that same hand to stop roll, and work the wings back to level via small corrections, or one larger correction. Given what A330 experienced pilots who have posted here have shared, at that altitude the small corrections might be the better technique, as they adivse us that the A330 is sensitive to input in that flight regime when hand flying.

ASIDE: Any pilot who cannot correct for pitch and roll at the same time by referencing his attitude indicator cannot be considered to be qualified to pilot a passenger jet. I am sure both of the pilots in that cockpit had demonstrated time and again that they could make such an input in two axes successfully. I seriously doubt AF would have hired them had they not been able to. The answer to why neither did in this instance, particularly the pilot who handled the controls at the handoff from HAL to Human, remains incompletely answered to my eye, other than to consider comfort with the aforementioned sensitivity to input. What did he see?)

So, even if the plane at hand off was in a non stable state -- which is part of your point -- a change in nose pitch, or a continuation of a nose pitch change in one direction or another is not necessarily a fait accompli if the pilot whose hand is on the stick flies in accordance with standard instrument flying principles, principles he had previously shown he could apply consistently. (For this and other reasons the "pitch and power" chorus has been singing in three part harmony on these forums since about 01 June 2009 .)

Your analysis of what the pitch result was, in and around that point in time, must to be complete (IMO) include a consideration of what flying performance was desired at the time.

At the altitudes in this event, 11 degrees nose up borders on an unusual attitude, for the flight condition and peformance desired on that leg of the mission: straight and level.

Lyman

5th Dec 2011, 16:11

"The aircraft did not immediately respond..." BEA

This plays Hell with your primer, Lonewolf. Notwithstanding the Pitch was four plus degrees low on the pilot's AI. The STALL WRN suggests an AoA of extreme value, v/v cruise, and the a/c was maneuvering out of phase with its attitude, eg, Nose Low, and ascending.

At the very least, we suspect the airframe was not consistent with a ho hum cruise, and the a/p (imo) quit due controls/response out of limits. To include airspeeds discrepant: either disagree or simultaneous migration past a/p limit value. (30 knots < second and continuous). See the Mach variations as described above.

The only aspect consistent with a STALL Warning, at that speed, is AoA/Mach disagree, which is consistent with the accepted wisdom, here, as I see it, but not enough acceptance/credence is lent to the conditions extant at a/p loss/handoff/HAL malfunction.

It is troubling that without the conditions leading up to handoff, so many here have arrived at conclusions. You suggest a lack of skill is responsible.
The DFDR is reporting Inertial data, not what PF or even you would be seeing at the beginning (or 'continuation' of UPSET).

It is vital that the conclusion be exculpatory of the Bus. If due Weather, then the a/p v/v limits in stink is suspect. If a/p exceeded, the Bus is painted as poorly designed. How handy for a baby pilot to put them into the wet.

My starting point is that the crew inherited an upset airframe. The autopilot's limits are well past what is technically accepted as "Upset" in the regs. So naturally, ICE and inexperience are the uniform of the day.

The story is here, in the start, not at the (actual) STALL.

Organfreak

5th Dec 2011, 19:02

What blows my mind is your willingness to set aside the fact of (at least) 37 previous incidents of ice-caused UAS using a known-to-be-defective pitot. Instead you become an intellectual contortionist, sir.

There are plenty of confusing factors to this accident without all this stuff you're coming up with.:sad:

Lonewolf_50

5th Dec 2011, 19:38

Lyman, taking a plane that is not stable, if HAL did something odd, is roughly the same as taking the plane from another pilot who is flying badly or has vertigo. If you fly in multi-crew aircraft, I run with the assumption that the above is one of the tasks that you are required to do, and trained for.

If you are not trained to do that, one wonders "Why not?"

I refer you again to my old refrain: what did he(PF) see? Though the betting money is on all of the AH's working, the PNF did switch sources to a different inertial gyro for one reason or another.

What was that reason?

More than one possible answer, and since they didn't verbalize why that was done, the why is left open to some question. Those who have flown the A330 may be able to offer better estimates that I, so I won't attempt to.

Nothing further.

Out.

HazelNuts39

5th Dec 2011, 21:27

... what did he(PF) see? Though the betting money is on all of the AH's working, the PNF did switch sources to a different inertial gyro for one reason or another.
The PNF was apparently looking at all three displays between 02:10:25 and 02:10:36:
Reading the three instruments (the two PFD’s and the ISIS), the PNF noticed that the
airplane was climbing and asked the PF several times to descend.
Subsequently he made following selections:
02:10:40 F/O on ADR3
02:10:44 F/O on IR3
02:12:15 CAPT on ADR3
02:12:19 CAPT on IR3
02:13:25 CAPT on ADR1

Machinbird

6th Dec 2011, 00:55

The PNF was apparently looking at all three displays between 02:10:25 and 02:10:36:
Reading the three instruments (the two PFD’s and the ISIS), the PNF noticed that the airplane was climbing and asked the PF several times to descend. Subsequently he made following selections:
02:10:40 F/O on ADR3
02:10:44 F/O on IR3
02:12:15 CAPT on ADR3
02:12:19 CAPT on IR3
02:13:25 CAPT on ADR1
Logically, PNF wanted to be sure that PF was flying with information that looked good to PNF and so that he, PNF, could be sure of what was appearing on PF's panel. (Since monitoring the PF's PFD was a bit of a stretch for PNF.)

Obviously PNF trusted the ADR3/IR3 data and likely didn't understand why PF insisted on flying around with his nose in the air.

Then later, to ensure that he could also conveniently read the ADR3/IR3 data on his PFD, he switched his displays to the same data sources. (Despite the loss of redundancy.)

That is my take on these actions. Sorry about all the acronym soup.:confused:

HazelNuts39

6th Dec 2011, 07:30

It seems to me he primarily switched the Air Data source, just taking the Inertial Reference along without any particular reason.

Lonewolf_50

7th Dec 2011, 14:39

Thank you both for your thoughtful estimates. :ok:

scrunchthecat

8th Dec 2011, 03:38

Popular Mechanics has a new article on its Web site today discussing "What Really Happened Aboard AF447." The article includes the final conversations of the crew, along with analysis. According to the PM version, the captain does finally realize the plane is in a stall, and in the last seconds tries to point the nose down, but they run out of time.

Print - What Really Happened Aboard Air France 447 - Popular Mechanics (http://www.popularmechanics.com/print-this/what-really-happened-aboard-air-france-447-6611877)

AlphaZuluRomeo

8th Dec 2011, 11:22

An even fuller picture emerged with the publication of a book in French entitled Erreurs de Pilotage (volume 5), by pilot and aviation writer Jean-Pierre Otelli, which includes the full transcript of the pilots' conversation.
I disagree. Having read the book, I commented it here (http://www.pprune.org/6748867-post1229.html).

The "picture" in Otelli's book indeed adds some points to the data contained in the BEA's last interim report, but on the other hand it lacks of data/information on some other points.
=> Describing it as "fuller" is in my opinion a bit of an overstretch, and carries implicitely the impression that some things are "hidden" by "the authorities" (BEA), which constitute a polemic, not a fact.

---------

The quoted article lacks some nuances (which can be of importance, when really wanting to understand). Let's try to correct some of that:

02:06:50 (Bonin) Va pour les anti-ice. C'est toujours ça de pris.
Let's go for the anti-icing system. It's better than nothing.
"It's better than nothing." feels pessimist. The exact translation for that exists and is used in french: "C'est mieux que rien". That's not what the pilot said.
"C'est toujours ça de pris." is optimistic. They turned on the anti-ice, as a precaution against potential icing conditions. They didn't turn on the anti-ice as a mean to try to limit an already bad known problem.

02:08:07 (Robert) Tu peux éventuellement prendre un peu à gauche. On est d'accord qu'on est en manuel, hein?
You can eventually pull it a little to the left. We're agreed that we're in manual, yeah?
In french, "éventuellement" means eventually in the sense of "possibly". Not in the sens of "in the end".

02:10:31 (Robert) Tu redescends... On est en train de monter selon lui… Selon lui, tu montes, donc tu redescends.
Descend... It says we're going up... It says we're going up, so descend.
The BEA report differs :
2 h 10 min 33: (PNF) Selon les trois tu montes donc tu redescends
=> According to the three you’re going up so go back down
"Les trois" (the three) is important, it means the PNF refers to 3 indications (either the 3 ADIs, or the ADI and the V/S and the altimeter)

...

I leave it there, just wanting to try and convince you:
1/ to read the article (it's interesting in quoting extensively Otelli's book, only published in french AFAIK)
2/ but to exercice caution. The advertised "full transcription" (and implicitely "full explanation") is marketing to sell paper... ;)

Cheers
AZR

Lyman

8th Dec 2011, 17:22

At the crucial moment of a/p loss, the airframe was climbing, and the Nose was Pitched down. Added to that, the bank angle was about 8 degrees Right wing low (turbulence?). The a/c had it right, they were in a robust upwelling, an updraft, and the Nose was commanded down, though the a/c still climbed. We do not know for how long the a/p had been maneuvering in this fashion, though it can be said that the pilots themselves, in discussing temps and calling the back for a HU on turb tells us it was not new.

It is this possibility that has been actively ignored. I believe the PF made a correction in Pitch that was perhaps the opposite of what was needed. Climbing in the airmass, a NU creates more climb, in g and in VSI.

Much is made of their presence in a cell, though the possibility of a robust UD is dismissed?

The column may have been 120 knots. If so, this plays havoc with airspeeds, AoA vanes, and 'feel'. The airspeed in descent could have been twice that reported by the DFDR. "I think we have crazy speed..."

As with any epic disaster, those whose fingerprints are on the investigation call the shots. Though BEA have not done so, the focus is on the 95% of what is utterly irrelevant to the disaster.

What caused the climb to Stall is virtually ignored, and when addressed, data is ignored, and the audience is expected to sign on.....

I think PF did fly attitude, more's the pity. And Power was not a player, not at first.

HazelNuts39

8th Dec 2011, 18:50

I think PF did fly attitude
time ........ attitude
(hh:mm:ss) ... (deg)
02:10:05 ....... 0
02:10:18 ...... 11
02:10:25 ...... 12
02:10:49 ....... 6
02:11:07 ...... 17.9

Which attitude?

Organfreak

8th Dec 2011, 19:21

Lyman claims that the aircraft was climbing, nose down. I have two questions:
1.Is that supported by the reported data?
2. How is that even possible?

HazelNuts39

8th Dec 2011, 19:30

1.Is that supported by the reported data?
No, the V/S was going through zero, decreasing
2. How is that even possible? It is possible, if the airmass is rising fast enough.

Wings were level, rolling right, 8 deg 2.5 sec later.

Lyman

8th Dec 2011, 20:34

Hazelnuts39 Pls. take note of the VS and the Attitude, two seconds prior to a/p loss.

Note that in two seconds the actual VS had changed from 500 fpm up to a like number down. That is remarkable, and the a/c was at what weight?

The Nose was in transit as the VS reversed, and they were not in tune.

I think the a/p was attempting to rate the UPDRAFT with elevators, and it eventually required too much ND (v/v AoA) to keep up (level). The Screen reported ND at handoff. Not Level.

Have you a reference for the deflection of Vanes due airmass? That geometry is beyond my current take. Something was causing the Vanes to read crazy high, and it was not 'cruise Nose'.

HazelNuts39

8th Dec 2011, 21:24

Note that in two seconds the actual VS had changed from 500 fpm up to a like number down. That is remarkable, ...The change corresponds to a normal acceleration of 0.85 g, well within the ICAO “light” turbulence criterion of 0.5 g peak to peak. (3.5 seconds of normal acceleration of 0.85 g changes V/S downwards by 1000 fpm.)

Have you a reference for the deflection of Vanes due airmassThe vanes are shown on the same page 42 as AoA IRS1,2,3.

mm43

8th Dec 2011, 22:00

Relevant graphics from the BEA's IR#3 that I posted on page #27 of this thread are available as a "cross-hair version" (http://countjustonce.com/af447/af447-fdr-data-xhair.html). Enlarged with additional scaling and timing marks, the chances of getting the actual up/down rates etc. will be improved.

ChristiaanJ

8th Dec 2011, 22:22

Really nice one, mm43,
Unfortunately, can't save it in an off-line format, and the cross-hair pointer doesn't show any data.

Give us a clue on how to use it?

CJ

mm43

8th Dec 2011, 23:11

@Christiaanj;

With the enlarging of the graphic, additional scale marks have been added, along with an overlaid time scale in each section. The adding of the cross-hairs enables a closer examination of any points of interest with the x:y co-ordinates now easily readable.

To save for offline use, right click outside the graphic (pale blue background) and Save As (webpage complete). The javascript file that generates the cross-hairs will also be saved.

DozyWannabe

9th Dec 2011, 00:28

Hmm - if work lets up I might have a play with that JavaScript, see if I can't tart it up a little. :)

So - based on mm43's web graphic we have:
The pitch attitude *bang on zero* at disconnect
Importantly however, trending nose-up
Followed by the last A/P command bringing the pitch attitude to about +1.5 degrees NU
A wobble in V/S around the time of disconnect, but *well within the tolerances for "MODERATE" turbulence*
A very clear difference in elevator response from 02:10:08 onwards, possibly indicative of manual control
A/P elevator control has a max NU of 0.6 (correcting for the bump beginning at 02:10:00) and a max ND of 0.5 - compare this with a max NU of 2.1 and a max ND of 0.6 under manual handling

I still see an aircraft that was relatively stable for the turbulence they were in until the PF starts overcontrolling.

Pali

9th Dec 2011, 05:53

How stable is this Airbus? What would happen if the PF wouldn't touch the controls for a while until all the instruments would be functioning and a/p could be switched on again?

HazelNuts39

9th Dec 2011, 08:49

What would happen if the PF wouldn't touch the controls for a while ... In the two seconds between A/P disconnect and the PF's first control input, the FCS commanded elevator nose-up which returned pitch to almost normal and normal acceleration to approx. 1 g.

RetiredF4

9th Dec 2011, 12:31

@ mm43
Excellent work, i hope we see more of it, especially the times when the stall warnings happened.

Hazelnuts
In the two seconds between A/P disconnect and the PF's first control input, the FCS commanded elevator nose-up which returned pitch to almost normal and normal acceleration to approx. 1 g.

I tend to disagree.

At the very moment, when the autopiloit disconnect occurred, we have the following values:

-vertical speed zero with tendency to decrease
-normal acceleration .85 g`s (@mm43, i think your labeling is off by one, the line you labeled 0 should actually be 1 g)
-pitch attitude 0°
-AOA 2.25°

The moment the AP drops out and stick is in neutral , NZ-Law will maintain flightpath / 1 g with reference to the flightpath, the aircraft was in at AP disconnect. (Whatever position intended by the AP before does not matter any more).

That would be a descent under the above recorded parameters.

franzl

grity

9th Dec 2011, 13:14

RetiredF4 but if you extrapolate the rollrate of 4 deg/sec to the right between 2:10:05 and 2 :10:07 you will only a short time descent peacefully before you dive.....

HazelNuts39

9th Dec 2011, 13:18

RetiredF4;

I simply read the traces. After Clandestino in post #393 (p.20) (http://www.pprune.org/tech-log/468394-af-447-thread-no-7-a-20.html#post6814745) I'm not so sure about Nz law maintaining flightpath / '1g' in turbulence.

Lyman

9th Dec 2011, 15:10

The point I am making is this: Whilst the airframe accelerated upward, the Nose Pitched Down. It is at this exact moment that the a/p quit.

The Nose is "trending" UP, the VS is trending DOWN, and that signifies...

"MANEUVERING"

For five seconds, the airframe is not stable v/v level, speed, or acceleration. Well and good to pontificate re: what PF must do, but this massive airliner is spunky as a little Robin, and that ain't right.

"I have the controls...." Whether OR NOT the PF knows the genesis of disconnect, he is well within his rights to assume the a/p has left because of control demands, not ICE. At this point, he does not know, and after two plus years on, neither do we.

I sense HN has some misgivings about a/p in the stink. So did Smilin Ed, and so do I. The A/P has quit, the a/c is wanting management, and the Bus has reverted to "Other than NORMAL LAW". Free to STALL, you're on your own. The BUS has left the building.

Make NO mistake, what the pilot does now is the precursor, and (I think) the procuring cause of manually induced UPSET and LOC. Is there a 'sit on your hands' command for the AUTOPILOT? Thought not.

Wanting to establish a 'normal' flight path is a natural for any pilot flying an airliner. Perhaps there is a flaw in the training concerning this situation.
NOT "I have the Controls", but instead "monitor the Stick, No Touchee".

Wait, what good is there in 'monitoring' something that does not move?

RetiredF4

9th Dec 2011, 15:20

Hazelnuts
RetiredF4;
I simply read the traces. After Clandestino in post #393 (p.20) I'm not so sure about Nz law maintaining flightpath / '1g' in turbulence.

I do the same, but then lets see what Clandestino wrote:

............Sidestick neutral iz not 1G it is 0G.

There is one word missing at the end, it is 0 g change. As the basic and overall topic of Nz-Law is to maintain a flightpath ( = flightpath stable = 1 g flight ) the sidestick in neutral commands no deviation from this 1 g flight, which means no loadfactor change at high speed or no pitch rate change in low speed.

Sidestick command does not order G in absolute terms. It adds G demand to already measured, therefore if hit by updraft giving you 1.3G, pull on the stick that would give you 1.1 absolute from straight and level will now result in 1.4 pitch up. Push giving 0.9 would now be 1.2.

He is wrong there. What he might be is referring to s the fact, that a dampening input is added to the normal LAw command.

LTTM- TURBULENCE DAMPING FUNCTION (bolding by me)

General:
The purpose of the Turbulence Damping Function implemented in the Electrical
Flight Control System is to damp the structural modes induced by atmospheric
turbulence.

Architecture
The Turbulence Damping Function consists of two lanes:

Longitudinal lane. The longitudinal Turbulence Damping command is computed by the FCPC1 (FCPC2 as a redundancy) as a function of the Nz accelerometer information. It is added to the normal law command and transmitted to the associated elevator servo-controls.

Rear lateral lane
The rear lateral Turbulence Damping command is computed by the FCPC1
(FCPC3 as a redundancy) as a function of the informationof a specific Ny
accelerometer located at the rear bulkhead level. It is added to the normal law command and transmitted to the associated yaw damper.

To sum it up, if the SS is in neutral (= 1 g flight) and turbulence is disturbing the flightpath away from this one g flight, an opposing command is added to the existing 1 g flight command or like Clandestino likes to put it to the 0 g- change command).

If not hands off, but with a SS command of 1.2 g an updraft and thus increase of commanded g change by .4 g (which would give us 1.6 g) would stimulate the system to counter this increase by adding up to the commanded 1.2 g, thus maintaining the ordered 1.2 g of the SS as close as possible.

Any deviation from the flightpath (1 g with hands off, ordered g change with SS or AP inputs) will be opposed by the dampers by an respective counter action command within the capabilities of the system.

Let´s face the fact, anything else would be not helpful at all.

That the SS command adds to the already existing g, thus the SS command not giving a specific amount of flightpath change (load factor change at high speed, pitch rate change at low speed) is against any basic principle the C* law is funded on. But anybody feel free to point me to some reference here. Imho such an aircraft would not be controllable.

In the discussion there were also comments concerning load factor demand in high speed and pitch rate in low speed. Some here seem to believe, that in low speed the aircraft keeps the last pitch, if the stick is in neutral.
The aircraft will maintain a given flightpath, if we intend to change that flightpath with a SS input the gain will be load factor change at high speed and pitch rate change in low speed, but it still will maintain flightpath and not pitch in low speed with SS neutral (assumed that no protections are involved).

Again feel free to correct my research here.

When discussing the crew actions, their motivation of those actions and the resulting aircraft behaviour, which again constitutes an feedback channel to the crew, it is of immense importance to know how the systems work.

franzl

RetiredF4

9th Dec 2011, 16:02

A319/320 description Nz Law

Manoeuvre demand law as basic flight mode
- neutral speed stability with full flight envelope protection
-Vertical load factor control proportional to stick deflection : C* law
- independent of speed, weight, center of gravity ;

stick displacement : Nz = n Nz = n + 1g
stick neutral : Nz = O Nz = 1g

C* = q + K_C* x delta_Nz
q = pitch rate
delta_Nz = incremental load factor
K_C* = C* crossover gain - chosen to balance q and delta_Nz contributions

Flight path stability instead of speed stability
- control inputs are made to alter the flight path, not to hold it.

Medium-term flight path stability :
- maintenance of parallel trajectory 1g in pitch even after atmosphere disturbance.

C* (pronounced "C Star") is the popular name for a control law in which Nz (g) and pitch-rate feedback are blended. (In the late 60s and early 70s, Nz feedback was called the C law. NASA space shuttle approach studies added pitch-rate feedback, which was called C*.) At low speed in a C* airplane, pitch rate is primary; at higher speeds, g is primary. The changeover is transparent and occurs at about 210 knots in the A320 ("Fly-By-Wire for Commercial Aircraft: The Airbus Experience," C. Favre, 1991).

4.3.4. Longitudinal static stability. The A320's C* pitch control law is a manoeuvre demand law: the pilot's control inputs are interpreted as a demand for a given level of manoeuvre rate and the control system provides the surface deflection needed to generate this rate. Releasing the side-stick commands flight path stability.

. C* (pronounced ‘‘C-Star”) is a term that is used to describe the blending of the airplane pitch rate and the load factor (the amount of acceleration felt by an occupant of the airplane during a maneuver). At low airspeeds, the pitch rate is the controlling factor. That is, a speciﬁc push or pull of the column by the pilot will result in some given pitch rate of the airplane. The harder the pilot pushes or pulls on the column, the faster the airplane will pitch nose up or nose down. At high airspeeds, the load factor dominates. This means that, at high airspeeds, a speciﬁc push or pull of the column by the pilot will result in some given load factor.

And who likes to dig deeper and compare it to the 777, can read here. (http://www.pprune.org/tech-log/470643-b777-pitch-control.html)

Going back to my armchair again:O

franzl

mm43

9th Dec 2011, 17:02

Originally posted by RetiredF4 ...

.... i think your labeling is off by one, the line you labeled 0 should actually be 1 g

Thanks for pointing that out. The graphic label now reads 1.0 (1,0)

Lyman

9th Dec 2011, 17:08

Evidence. Three seconds prior to a/p disconnect, the airframe was subject to a robust Updraft (from DFDR). The FPC ordered Nose Down, to arrest the ensuing ascent (climb). This is of record.

After this event, the a/p quit, and PF took control.

Still looking for direct evidence of ICE, not unsubstantiated opinion.

OK465

9th Dec 2011, 17:30

Some here seem to believe, that in low speed the aircraft keeps the last pitch, if the stick is in neutral.

SS neutral at low speed = zero pitch rate demand

What you see at lower speeds (ALT2) with speed bleeding off and with a 'hands off' neutral SS is essentially pitch attitude maintenance while the FPV (if selected) gradually drifts lower (not FP maintenance) as AOA increases.

(No turbulence damping in ALT2.)

:)

mm43

9th Dec 2011, 19:17

Originally posted by Lyman ...

Still looking for direct evidence of ICE, not unsubstantiated opinion. The following may help your search for evidence:-
http://oi39.tinypic.com/juxp8y.jpg
Then review the CAS trace in BEA's IR#3 - second from top on page 112. I'm sure you will note the increasing CAS during the climb

Lyman

9th Dec 2011, 19:25

447 entered an updraft, it is on record. after exerting its influence on her, she started to climb, and reached a VS of 500fpm. What was the velocity of the updraft? 500fpm? Hardly. let's be conservative and call it 60 knots, vertical. Before the airframe rises, the pitots are sampling the airflow. If 60 knots on the nose, the IAS is 60 knots increased. If on the tail, 60 knots reduced. How about straight up? 30 knots less, and sampled simultaneously by all three probes. This is enough to cause the a/c to reject NORMAL LAW, and degrade to ALTERNATE. It also explains some Mach deviations reported in the DFDR. After sufficient time to outwait a possible anomalous loss of AS, the A/P is commanded to quit, after the RTLU locks.

Now this does not solve the problem of what happened, but it does suggest that perhaps an obsession with ICE may want a look. It may also call to question the reliance on this autoflight system in a cell.

VGCM66

10th Dec 2011, 03:45

Air France 447 Flight-Data Recorder Transcript - What Really Happened Aboard Air France 447 - Popular Mechanics (http://www.popularmechanics.com/technology/aviation/crashes/what-really-happened-aboard-air-france-447-6611877)

The best so far and probably a synthesis of what the final BEA report will say. So helplessly sad. :ugh:

jcjeant

10th Dec 2011, 05:03

The comments reading is interesting
I notice that many are pointing to the dual input system and again yoke versus side stick and also the lack of CRM

HazelNuts39

10th Dec 2011, 10:12

The vertical wind speeds in this graph have been derived from the recorded AoA, pitch attitude and the aircraft horizontal and vertical speed components. The calculation is very sensitive to small errors in AoA and pitch attitude, and should therefore perhaps not be taken too seriously.
http://imgur.com/XvEwhhttp://i.imgur.com/XvEwh.jpg

Lyman

10th Dec 2011, 15:56

HazelNuts39

I take your point re: sensitivity. Such vulnerability to errors of small magnitude is out of context (sic) for any graph of windspeed. One is tempted to say that the nomenclature is reversed, and that the airmass is the line "Aircraft". However, to claim the airmass line as the a/c would involve a belief that the v/s of this airframe is ridiculously responsive to airmass, let alone controls.

So the graph is essentially useless, imo. A response of airframe of even 500fpm to an updraft of 2500fpm is to stretch, especially when considering the a/c is in sensitive airspace, and in autoflight. Also consider the airframe, per graph, is responding far too quickly to light forces, and reversing out of all sense of Physics.

Do you take my point? The airframe is climbing at a rate completely inconsistent with the data. No updraft of 2500fpm will cause this aircraft to leave its cruise level with a functional (sic) autopilot latched. Nor will it cause said autopilot to command 4.5 degrees nose down (-1 degree PITCH) from cruise (+3.5 degrees) at Mach .80.

All this well before disconnect, no PF touching anything.

mm43

I am not saying there was no ICE. I am proposing that the loss of autopilot and the degrade to AL was caused by loss of AS, actual, as a result of Updraft. Once in the climb, in warm wet air, the airframe, including Pitot Probes and Statics, may well have ICED. I believe that it was likely, even. I also think that it was not consequential, since Airspeeds returned quickly. At that point, however, the Airspeed was remarkably lower, due Updraft, AoA, and climb gobbling up energy.

gums

10th Dec 2011, 16:03

Excellent post, Retired. And coming from an old stick-and-rudder-and-AoA dude, heh heh.

- As with the 'bus, our Viper control inputs resulted in close to "absolute" rates and gee, and were not "additive". The 'bus has some attitude and roll values added that we didn't employ. e.g. Pitch gee is biased for pitch attitude up to "x" degrees of pitch in Normal law. Gee is also adjusted for bank angles up to "x", so making a level turn and keeping the jet level is easier than what we had in our little jet. This aspect of the Nz laws helped us enter the dreaded deep stall at extreme pitch attitudes, as relaxing stick pressure resulted in a continuous one gee pitch command and the jet didn't go over the top in a ballistic trajectory at zero AoA or gee.

- The discussion about blending pitch rates with the gee command is a good one. Our laws reflected that, especially in landing configuration when rate dominated gee command. We also biased the AoA curves to provide us the "feel" of a conventional jet where you trimmed/commanded for an AoA. In other words, the neutral speed stability had to be overcome.

- Both of the above made the Viper feel like a much larger jet. Going thru turbulence and thermals at low altitude/high speed was very smooth. Was like an old Cadillac with the "soft" suspension versus the teeth-splintering up and down ride.

- The dynamic and static pressure inputs influence body rates due to the "gains" that are used for control surface deflections in magnitude and rate. As I have pointed out before, the Viper used fixed values for the gains when the air data was deemed unreliable. Seems the 'bus gives up and tells the pilot - "you have the controls". Heh heh.

MM43's input on handling the frozen sensors hits home for this old dinosaur. Had the static ports freeze up once in the SLUF and was descending for the approach in weather. Hmmmmm... I am not going down and speed is building up. Since we had an inertially-derived vertical velocity in the HUD, it was obvious I was going down and I checked groundspeed ( also inertially-derived), Clue light comes on and I realize I had frozen static pressure. BFD and waited for the radar altimiter to kick in at 5,000 feet and then the ice on the ports finally melted, so things were back to normal.

Lyman

10th Dec 2011, 16:10

gums

And certainly without PAR, eh?

HazelNuts39

10th Dec 2011, 19:18

So the graph is essentially useless, imo. I'm really relieved to read that.

Hamburt Spinkleman

10th Dec 2011, 20:02

It is apparent that HazelNuts39's graph is based on sound method and best available data.

To dismiss it because it does not support a theory, seemingly based on numbers that have been pulled out of a hat at random, is foolish.

gums

10th Dec 2011, 20:28

@ Lyman

No PAR, just ol' Gums and the ILS radio stuff and some skill and cunning. Oh yeah, no PNF to worry about.

OTOH, worst WX I ever landed in was a PAR, and a crusty Navy Chief talked me down in 100 and a quarter official, but more like 50 and an eighth. Call it WOXOF, if you will.

BraceBrace

10th Dec 2011, 21:08

I might be making a totally stupid remark, but the "wind chart", even though it's not reliable, made my mind think "physics of flight".

Don't know the A330, neither how silent/loud it is and how loud changing airplane velocity is. These "speed of airflow" changes are not always created by changes in airplane speed, but also by violent up- or downdrafts. I wonder if, even when the airplane reduces its speed in reality, the sound of increasing violent updrafts could've created a false sense of speed.

On the other hand you have the physical characteristics of low speed stall (low speed because the "stall" protection is here primarily a low speed protection), which in my brain has always been a "silent" maneuver because of low speed. Yes buffet will be there, but it can also be a characteristic of higher speed flight.

If that is the case the "initial pull" seems logical because the physical environment gives you the impression of being in an airplane that increases speed. Add a "stall" warning on top, and confusion can be total. Sense and computers give totally opposite impressions to the pilot and it is only the "wind sound level". We all know the problem of visual illusions, however they can also be physical.

Clandestino

10th Dec 2011, 22:19

The rear lateral Turbulence Damping command is computed by the FCPC1What is FCPC1 and which aeroplane has it installed?

our Viper control inputs resulted in close to "absolute" rates and gee, and were not "additive". Because you had G-trim, very useful feature for tactical fighter, absolutely unnecessary for aeroplane that spends 90% of its time in straight and level.

RetiredF4

10th Dec 2011, 23:34

Clandestino
What is FCPC1 and which aeroplane has it installed?A330 /340

You ask for others or you are testing?

GENERAL DESCRIPTION A330/340 Flight Controls

The surfaces are controlled by three types of computers, depending on their
functions:
- the Flight Control Primary Computers ( FCPCs ) ( 3 per A/C ),
- the Flight Control Secondary Computers ( FCSCs ) ( 2 per A/C ),
- the Slat and Flap Control Computers ( SFCCs ) ( 2 per A/C ).
The FCPCs and FCSCs enable to control the aircraft in the roll, yaw and pitch
axes.

and so on....

As said before, it is useless to discuss matters without having basic knowledge of the systems.

mm43

11th Dec 2011, 00:53

@Lyman

I know you have "pulled" a post where you accepted that ICE was a factor, though stated again the inability of the A/P to maintain altitude in what appears to have been a fairly steady updraft (+/- turb) for about 25 seconds prior to A/P disconnect.

The A/P was pitching the aircraft ND in an attempt to maintain assigned ALT, and clearly from the graphics, the RVSM parameters were being exceeded. Perhaps the A/P disconnect was for that cause, and the UAS just happened along with the rising "warm/wet" air. The RTLU "latch" could only have been caused by the "speeds", and coincidentally the RVSM and UAS issues collided - time wise.

hillberg

11th Dec 2011, 01:17

After reading the "talk in the cockpit" I thought why are the hand control sticks not linked together mechanicly:rolleyes:-So each pilot can feel & see the input of BOTH controls, Not, One pulling to climb-One pushing for Air speed. With HAL 5000 on the fritz with frozzen petots :=,Looks like a major design screw up in anyones book.:ugh:

DozyWannabe

11th Dec 2011, 17:42

To dismiss it because it does not support a theory, seemingly based on numbers that have been pulled out of a hat at random, is foolish.

That's our Lyman! (ba-dum-tish!)

In all seriousness though, what Lyman is not taking into account is the time factor of the calcuations for those readings and traces. One of the things I noticed on my A320 sim trip was that when an altitude capture is selected, the V/S display on the FCU module will initially display a surprisingly high value before it settles - I believe this is because the value is computed in real time and relates to what the V/S *will be* if the current pitch and thrust commands are maintained - of course, when the autopilot stabilises pitch after the initial pitch-up or -down, this value becomes something more realistic.

My theory is that the values on the trace are also calculated in real-time and those large bumps just before disconnect are a result of what the V/S *will be* if the current trajectory is continued, the pitch is retained and/or corrections are not made. The autopilot was engaged long enough to ride out the bump but did not have enough time to return the pitch attitude to 4 degrees nose-up, eventually coming to rest around 1.5 degrees nose-up. The aircraft would have regained cruise level on it's own, but slightly more slowly. Everything that happens after then (including the elevator movements that command the zoom climb) are a result of the PF's overcontrol of the sidestick.

I suspect that what may have spooked the PF was not something he saw that we don't know about, but something we do know about - namely this "bump" just before disconnect, which briefly brought the pitch attitude below 0 degrees. The residual autopilot command was enough to bring the nose back above zero, but I think he mentally programmed himself to correct it manually and unfortunately overcooked it. From then on they were in the zoom climb and things quickly stopped making sense for him.

@hillberg - read the thread from the beginning, it's always going to divide people but it has already been covered to death here and elsewhere.

hillberg

11th Dec 2011, 19:14

TSB reports over threads ,A **** load of "Computers" & No "pilots" and control "Inputs" that have no feed back from PIC & SIC, A flawed approch to innovation in flying.

A33Zab

11th Dec 2011, 20:11

Assembled from separate logical snippets.......(could be not complete!)

http://i474.photobucket.com/albums/rr101/Zab999/A33APFDATHR_COND.jpg

HazelNuts39

12th Dec 2011, 09:51

My theory is that the values on the trace are also calculated in real-time and those large bumps just before disconnect are a result of what the V/S *will be* if the current trajectory is continued, the pitch is retained and/or corrections are not made. Based on the close correlation of normal acceleration, V/S and altitude (each being either the time-derivative or the integral function of one of the others), I don't think the traces support that theory.

According to FCOM 1.31.40 p.15 description of indications on PFD: The displayed vertical speed information is normally based on both inertial and barometric data.

DozyWannabe

12th Dec 2011, 11:08

We'd need someone more qualified to confirm, but moderate turbulence by any definition should not be enough to take out autopilot/autothrust and I don't think it did in this case.

The climb was caused by the human and not the computer, depite Lyman's ever more bizarre protestations.

@hillberg - we're not going into the force-feedback loop again if we can help it - suffice to say there are as many valid reasons for dropping it as there are for keeping it, so it becomes a matter of personal preference.

jcjeant

12th Dec 2011, 13:16

DW
@hillberg - we're not going into the force-feedback loop again if we can help it - suffice to say there are as many valid reasons for dropping it as there are for keeping it, so it becomes a matter of personal preference.

I do not think whether it's a matter of preference by anyone
This is something that can affect (in some cases) the (safe) conduct of flight
In fact .. there are currently two systems (the yoke and the sidestick) with or without feedback
There are questions about these two systems concerning the conduct of the flight and one of the two will prove better than the other
It's to weigh the advantages and disadvantages of each and make the best choice for flight safety

AlphaZuluRomeo

12th Dec 2011, 13:17

According to FCOM 1.31.40 p.15 description of indications on PFD:
The displayed vertical speed information is normally based on both inertial and barometric data.

Hi HazelNuts39,

How come there is a trace about that in the FDR, the choice being:
V/S from AirData
or
V/S from Inertial

(i.e. no choice "V/S from both sources").

Thanks :)

Hamburt Spinkleman

12th Dec 2011, 13:54

Vertical speed is derived from the IRs with the barometric input providing a damping function. If the IR becomes invalid the V/S indication changes to pure barometric. This is indicated by an amber box around the digital V/S display.

I seem to remember the intertial V/S being considered invalid above a certain value. 10 000 ft/min is what springs to mind.

A33Zab

12th Dec 2011, 13:57

Inertial V/S data actually seems to be a hybrid signal (IR & Barometric),
as posted earlier by Takata in august 2011:

http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-85.html#post6624383

Lyman

12th Dec 2011, 14:09

Dozy Wannabe

1. Interesting concept: "Anticipatory Instrumentation". Extrapolation is of limited value, and not to be relied upon.

2. The Updraft could easily have been well in excess of 10k fpm. I used 5000 as a low, and conservative, value.

3. VS not reliable via IR. Airspeed not reliable via IR.

4. In airdata compromised situation, you believe the Baro VS? Let alone a smoothed combination of the two? Especially in the presence of rapidly moving temps and pressures?

5. There is a good deal more evidence to support UPSET caused loss of speeds, than ICE.

6. For that matter, there is plenty of evidence to suggest the upset was caused by this environment, as well as UAS.

7. At Loss of Auto, the airframe was losing altitude, and vertical acceleration. Combined with Nose Low on the screen, what would you do? Wait, right, ask your advisors/instructors?

Challenge. Describe the accelerations on the Pilots' bodies as a result of this maneuvering.

HazelNuts39

12th Dec 2011, 15:29

I seem to remember the inertial V/S being considered invalid above a certain value. 10 000 ft/min is what springs to mind.The V/S trace seems to confirm what you remember. Would you have a reference for it?

rudderrudderrat

12th Dec 2011, 18:49

Hi DozyWannabe,
we're not going into the force-feedback loop again if we can help it It's not so much the force-feedback - it's the control surface displacement feed back loop that is missing.

Please see page 7 of http://www.easa.eu.int/rulemaking/docs/npa/2011/NPA%202011-09.pdf

“c) The use of side stick controllers together with electronic flight control systems which provide control augmentation and control deflection limiting systems could affect piloting awareness that the aircraft is approaching a control limited flight condition. It may be that return to normal flight condition and/or continuing of safe flight needs a specific crew action. In these circumstances a suitable flight control position annunciation is required to be provided to the crew, unless other existing indications are found adequate or sufficient to prompt that action.
(2) CS 25.777 Cockpit controls
Side stick controller force-deflection characteristics in pitch and roll together with displacement sensitivity and gains need to be evaluated. The intention is to show that normal inputs on one control axis will not cause significant unintentional inputs on the other. Consequently a new paragraph CS 25.777(i) is proposed requiring a suitable assessment.”

jcjeant

12th Dec 2011, 19:00

Dunno if it was posted before ...

DÉROULEMENT DU VOL
L’élaboration du déroulement du vol est basée sur l’analyse de l’enregistreur de
paramètres, le compte rendu équipage et les données radio-radar fournies par
la DSNA.
Le 14 Juillet 2010, l’équipage du vol AF 7567 DR effectue le vol Ajaccio-Orly.
La situation est fortement orageuse en région parisienne.
Vers 12 h 49, en approche vers Orly et en contact avec Paris ACC, l’aéronef rencontre
de très fortes turbulences au niveau de vol 180. Elles sont qualifiées par l’équipage
« d’extrêmes » près de l’attente d’OKRIX : l’avion subit un gradient de vent vertical
de 25 kt en deux secondes environ et des facteurs de charges compris entre - 0,03 g
et + 1,89 g en vertical et - 0,15 g et + 0,18 g en latéral. Ces valeurs de facteurs de
charges sont importantes mais toutefois à l’intérieur de l’enveloppe de certification.
La vitesse passe de 202 kt à 178 kt (Vs1g + 7 kt).
Les conséquences de ces turbulences sont une augmentation de l’incidence de
l’aéronef. Cette dernière atteint une valeur de 13 degrés environ. La protection en
incidence Alpha Prot de l’Airbus A321 se déclenche et le pilote automatique (PA)
se désengage. Le contrôle de l’appareil est repris manuellement par le copilote qui
amène les manettes de poussée en position TOGA (butée) et agit sur le manche.
L’aéronef subit des variations d’assiettes comprises entre - 10° et + 14° et également
du roulis entre + 2° et - 46°. L’équipage désengage l’autopoussée. Cette dernière
ainsi que le pilote automatique sont réengagés ultérieurement.

Crude Google translation ......
HISTORY OF FLIGHT
The development of the flight is based on the analysis of the recorder
parameters, reporting crew and radio-radar data provided by
DSNA.
On July 14, 2010, the crew of flight AF 7567 DR Takes Flight Ajaccio-Orly.
The situation is very stormy in the Paris region.
49 to 12 h, on approach to Orly Paris and in contact with ACC, the aircraft encounters
very high turbulence at flight level 180. They are qualified by the crew
"Extreme" about pending OKRIX: the aircraft was a vertical gradient of wind
25 kt in about two seconds and load factors between - 0.03 g
and + 1.89 g vertically and - 0.15 + 0.18 g and g laterally. These values of factors
charges are important but still within the certification envelope.
Speed increases from 202 kt to 178 kt (kt VS1G + 7).
The consequences of this turbulence is an increased incidence of
the aircraft. The latter reached a value of 13 degrees. Protection
Alpha Prot impact of the Airbus A321 is activated and the autopilot (AP)
disengages. The control of the aircraft is taken manually by the co-pilot
bring the thrust levers in TOGA position (lock) and acts on the sleeve.
The aircraft sustains variations of plates between - 10 and + 14 ° and also
Roll between 2 ° and - 46 °. The crew disengaged the autopoussée. the latter
and the autopilot are rehired later.

http://www.bea.aero/docspa/2010/f-zb100714/pdf/f-zb100714.pdf?PHPSESSID=e38d9ab268c55a3eec74fa196764388a

Hamburt Spinkleman

12th Dec 2011, 19:39

Hazelnuts39

The topic came up in a discussion with a tech rep some time ago. The discussion had veered off the main topic at that point so I didn't pursue it any further.

Thinking about it a bit more, 10 000 ft/min seems a bit low as a cut-off value. I would expect the IRs to be able to provide valid data at higher vertical speeds.

With regards to the PF and the V/S display, there are two slighly different layouts of the display. One where the only visible part of the pointer is the one covering the V/S scale, and one where the full lenght of the pointer is visible.

I do not know which version AF has, but if it is the first one the position of the pointer is less obvious when pegged at one end of the scale.

http://i42.tinypic.com/27wymtx.jpg

grity

12th Dec 2011, 20:12

HN39,The vertical wind speeds in this graph have been derived from the recorded AoA, pitch attitude and the aircraft horizontal and vertical speed components. The calculation is very sensitive to small errors in AoA and pitch attitude, and should therefore perhaps not be taken too seriously.how sensible is your calculation for smal changes in AoA? the elevator flys about 0.1 sec behind the wing, if you fly with CAS 250 into this sort of fast increased updraft the elevator had ca.160 feet/min lower updraft than the wing-----> the result in AoA is about 0.2 deg aditional-diference between elevator and wing

the bird pitch up, as if you pull 0.2 deg, if he fly into this strong updraft

(and visavers pitch down 0.2 deg if you fly outta)

is your calculation so sensible that this effect plays a role???

Lyman

12th Dec 2011, 20:54

grity

along those lines, which surface has the greater moment arm to affect Attitude? And how is this accomodated?

Up Elevator. Per PF

HazelNuts39

12th Dec 2011, 21:13

Grity,

The sensitivity of the calculated updraft velocity to errors in AoA or pitch is evident from the formula given in the header of the graph. For example, for GS + HW of approx. 500 kt, the updraft velocity changes by 88 fpm for 0.1 deg error in the recorded AoA.

Quite another matter is the pitch response of the aircraft when traversing an updraft zone of increasing or decreasing vertical velocity. That effect exists and has been discussed on an earlier AF447 thread, but is smaller than you suggest: The updraft increases about 2000 fpm in 5 seconds, and 40 fpm / 500 kt is about 0.05 degrees. The actual effect is even smaller due to the downwash behind the wing and other damping effects.

A33Zab

12th Dec 2011, 22:49

It's not so much the force-feedback - it's the control surface displacement feed back loop that is missing.

The F/CTL page - showing the control surfaces position - was automatically callled and in view on the System Display @ triggering of the F/CTL RUD TRV LIM FAULT (02:10:19).

Which could be in compliance with:

“c) The use of side stick controllers together with electronic flight control systems which provide control augmentation and control deflection limiting systems could affect piloting awareness that the aircraft is approaching a control limited flight condition. It may be that return to normal flight condition and/or continuing of safe flight needs a specific crew action. In these circumstances a suitable flight control position annunciation is required to be provided to the crew, unless other existing indications are found adequate or sufficient to prompt that action.

Next,

(2) CS 25.777 Cockpit controls
Side stick controller force-deflection characteristics in pitch and roll together with displacement sensitivity and gains need to be evaluated. The intention is to show that normal inputs on one control axis will not cause significant unintentional inputs on the other. Consequently a new paragraph CS 25.777(i) is proposed requiring a suitable assessment.”

Not very demanding IMO, SS is equipped with dampers, springs (Roll) & spring rods (Pitch) in all axis.

Lyman

12th Dec 2011, 23:40

For me, the supposition that aft stick at a/p release was inadvertent was put to bed long ago. I have to give a minimum amount of credit to PF, and I do believe still the a/c required aft stick as well as Roll left at drop.

An aircraft in an updraft will drop her nose, and in a downdraft, the reverse. By herself, it is basic to the geometry of the architecture. I could not tell you whether or how much attention was paid that fact by the software, (DOZY?). But in this a/c, if in an UP with the kind of energy I believe was in play, her Nose wanted down on the natch. The a/p may have "known" this, but it would not have abated at a/p quit. This may have been a major player in the PF's insistence on Nose UP, when in fact, Nose Down would be needed. Nose down is also contrary to g demand in PITCH, and the PF may have had help in Pitching this mama UP. NO?

Machinbird

13th Dec 2011, 00:51

Lyman, your constant restating of your theory is somewhat annoying to me. Saying the same thing many times does not make it correct. Flying at night, in turbulence, should not be overly challenging. If the aircraft needed a bit of nose up at AP disconnect, then 1/2 to 3/4 seconds of aft stick would have been sufficient. What PF was doing must have been quite different.

From the control position graphs of the first 10 seconds, PF was badly over-controlling the aircraft in roll. The energy and force required to make these lateral control inputs were likely substantial.

The Airbus stick is angled forward in its neutral position (to discourage cross channel inputs I understand). I suspect that with the drag from the roll channel viscous damper, PF could not get adequate leverage on the stick to keep up with his perceived need for fast lateral input. Once the stick is canted back towards vertical, there is higher mechanical advantage available. Please note, I am only discussing the control inputs up to the stall. Afterwards, there were different reasons for his aft stick input.

If someone (perhaps A33Zab) could come up with the force/velocity characteristic for the lateral channel viscous damper, then we could look at the energy and force required to make those lateral inputs. It might be very educational when looked at in terms of human energy expenditure.

Old Carthusian

13th Dec 2011, 04:13

grity

13th Dec 2011, 08:21

HN39, the pitch response of the aircraft when traversing an updraft zone of increasing or decreasing vertical velocity. That effect exists and has been discussed on an earlier AF447 thread, but is smaller than you suggest: The updraft increases about 2000 fpm in 5 seconds, and 40 fpm / 500 kt is about 0.05 degrees.I mesured in your calculation at 2:10:13 increases of updraft 1000 fpm in 0.7 seconds, that was my base for delta AoA ca. 0,2 deg

but you are right this is not so much......

VGCM66

13th Dec 2011, 23:44

AF447's initial altitude drift went virtually unchallenged (http://www.flightglobal.com/news/articles/af447s-initial-altitude-drift-went-virtually-unchallenged-360432/)

:(

Machinbird

14th Dec 2011, 03:17

I must confess a certain scepticism about such a suggestion. It suggests, to my mind, an unfamiliarity with the controls worthy of a tyro which whatever his reactions I don't think we can claim the PF to be. One shouldn't get too wrapped up in trying to find a mechanical explanation (red herring fillets). Rather there should be more examination of the psychological elements of this accident.
OC, So what are your thoughts about the following definition?
Pilot-induced oscillations, as defined by MIL-HDBK-1797A,[1] are sustained or uncontrollable oscillations resulting from efforts of the pilot to control the aircraft and occurs when the pilot of an aircraft inadvertently commands an often increasing series of corrections in opposite directions, each an attempt to cover the aircraft's reaction to the previous input with an overcorrection in the opposite direction.Do only tyros experience PIO? Was the aircraft's sustained roll oscillation before the stall a PIO? Had PF ever flown in Alt 2 Law at altitude?
Why would a somewhat experienced pilot be unable to fly smoothly?

Lyman

14th Dec 2011, 13:04

VGCM66

Thank you sir. In your link, we read an opinion from BEA as to what the crew "concluded". On its face, this statement is preposterous, since it imputes conclusions to the pilots based only on comment they made earlier. No one in public knows what the pilots were thinking, and BEA, having tipped their hand, may know, and appear to be rigging the playing field.

BEA present it as fact.

This release contains condemnation of Airbus and the airline sufficient to confirm my proposal. Read it with care, allow for some interpretive changes, and the accident falls to Airbus almost completely.

This fatal wreck happened in the ten seconds post a/p loss, and the pilots, though involved, were not entirely responsible. One needs to take the BEA with generous portions of salt. What about "Rapid Climb", and "the aircraft was not immediately responsive" sounds familiar? Think of another similar incident, one with a better outcome.

@Machinbird. Your cite of PIO is instructive. You neglect another form of out of sync C/R.

Autoflight induced oscillation. AIO.

VGCM66

14th Dec 2011, 14:26

I have a long flight ahead of me today.

I'll be back.

Machinbird

14th Dec 2011, 15:17

@Machinbird. Your cite of PIO is instructive. You neglect another form of out of sync C/R.

Autoflight induced oscillation. AIO
Lyman, I generally disregard your theories since they are normally composed of 2/3 reasonable fact and 1/3 something pulled from behind the refrigerator. My intent in responding is to separate my comments from yours on this occasion.

Judging from where the Autoflight system dropped the aircraft (essentially on altitude, essentially on speed, essentially level) and the fact that the Autoflight system dropped completely out at the cavalry charge, your comment would seem to have no merit. Oscillations generally have a characteristic frequency. What characteristic frequency do you suggest for this phenomena?

DozyWannabe

14th Dec 2011, 15:18

Lyman, you're going so far off the deep end by coming up with these ever more elaborate excuses as to how it must have been the aircraft's fault that you have now officially transited the boundaries of known space into la-la land as far as I'm concerned.

You're trying to parlay the autoflight's interrupted response to a comparatively large bump from turbulence - of which not one cycle was completed before the PF took control - into a hitherto-unknown phenomenon that you've just invented. I mean, extrapolation is one thing - but what you're suggesting has not only never been known in the hundreds of thousands of hours the type has been in service, but completely contradicts the evidence at hand.

HazelNuts39

14th Dec 2011, 16:26

Lyman,
You repeatedly attribute statements to BEA that I'm unable to find in BEA's publications: "The aircraft did not immediately respond..." BEA One needs to take the BEA with generous portions of salt. What about "Rapid Climb", and "the aircraft was not immediately responsive" sounds familiar?

ChristiaanJ

14th Dec 2011, 16:28

Autoflight induced oscillation. AIO
ROFLMAO....

Thanks for confirming, once more, your total ignorance of basic aircraft stabiliy, and automatic flight control system design and testing.

Hamburt Spinkleman

14th Dec 2011, 16:44

I am also curious where those quotes come from. A word search of the BEA reports and press releases reveals no such quotes contained in any of them.

Old Carthusian

14th Dec 2011, 23:51

Machinbird

15th Dec 2011, 02:14

Machinbird
Whilst I do not doubt the phenomenon exists I was reading your post as an indication that you believed the design of the sidestick played a part for inducing the oscillations. This is what I was questioning. All evidence from the Airbuses flying is that the sidestick is a reliable and useful input device with very little in the way of vices. The more I see of the evidence the less it appears that the machine had any role in the accident. There is no 'smoking gun' as it were; just pilots who were not adequately trained or prepared for what should have been a recoverable situation.
Let me re-state the theory (And at this point it is just a theory.)
The AF447 PF made too large of an initial lateral control input and ended up sending the aircraft into a roll oscillation which can be seen in in the BEA charts. He attempted to 'get ahead' of this oscillation by making even more rapid control deflections, but ended up continuing to drive the oscillation. In his frantic attempt to move the stick even more rapidly against the drag of the roll viscous damper, he brought the canted forward stick back from neutral into the nose up direction to obtain better mechanical advantage (since the stick being vertical gives him a greater lever arm). This response would be automatic if he was concentrating on his roll control problem.

I agree that the sidestick can be an accurate, useful, and safe means of control. However, the A320 does have occasional problems with roll PIO. Perhaps the A330 does as well in the correct circumstances-like in roll direct mode at altitude.
When a pilot encounters PIO, one of the natural reactions is to believe that the control system is malfunctioning. Most of us would find this extremely disconcerting. It would be good for a double dose of adrenalin.:eek: An experienced pilot would change his control strategy to break the oscillation. An inexperienced pilot would likely continue the oscillation until he tired of the effort of driving it. That is what the BEA charts seem to indicate. (And as the roll oscillation began to get under control, so did the nose attitude.)
PIO is a complex condition and should not be blamed on just the sidestick design. If roll PIO was a player in this accident, then the fixes are relatively simple. Roll direct is an infrequent operational mode. Roll direct at altitude will be even scarcer. It is entirely possible that only a small percentage of pilots employ "high gain" control strategies that would trigger a roll PIO. BTW the C-17 aircraft was very late in its development cycle before its roll PIO characteristic was identified and corrected.

Training to avoid "high gain" control strategies would help pilots avoid PIO. Perhaps we need a PIO training device to teach pilots how to avoid it.:} Meanwhile, "mayonnaise stirring" should definitely be avoided on Airbus type aircraft.

Old Carthusian

15th Dec 2011, 09:08

Machinbird
I see what you're driving at now and as a mechanical explanation of the exact process it certainly has merits. However, I suspect that the reaction of the PF would have manifested itself in a similar manner no matter what the input mode. This was not a pilot who was thinking clearly or logically and this was not a crew that was following any known procedure. The proper management of the flight deck was missing and whilst I like the mechanical process you lay out I don't see it as having anything to do with the development of the accident other than the in the most peripheral way.
A330 pilots who have commented on the flight characteristics of the aircraft on these threads indicate that the aircraft is a very stable machine which quickly recovers a stable flight regime even in ALT2. The aircraft seems to be designed to help the pilot as long as the pilot trusts the aircraft.

Lonewolf_50

15th Dec 2011, 12:35

A330 pilots who have commented on the flight characteristics of the aircraft on these threads indicate that the aircraft is a very stable machine which quickly recovers a stable flight regime even in ALT2. The aircraft seems to be designed to help the pilot as long as the pilot trusts the aircraft.
They have also commented upon how challenging hand flying A330 at altitude is.

Machinbird's point on "control strategy" strikes me as well made. His theme takes us back to currency, familiarity, and training in the modes of hand flying a pilot may be exposed to.

Lyman

15th Dec 2011, 14:33

For what it may be worth, and I have no illusions, imho, Machinbird is spot on. BEA, having assembled an "HF" group, is attempting to shepherd Opinion in the direction of events that came after the initial blunders, and the aircraft's shortcomings. With a focus on the initial ten seconds and the initial climb, comes widening culpability for the airframer.

BEA quotes: Keep looking, and in their discovery, one may get a picture of how BEA is manipulating the facts.

"ICE, NOT ICE". @Alpha Zulu Romeo. On the contrary, the ICE issue is perhaps the single most important factor in the solution of this mystery.
"ICE", if proven, deflects focus away from the airframe's inabilities to deal with loss of Speeds.

If "NOT ICE", we need to look at AIRBUS' blunders in providing a straightforward solution to Autopilot/Pilot transition, rather than an after the fact publication of accidental and in service mitigations and recoveries. All the defense on this thread of how simples it is to recover an a/c from uncued maneuvering and loss of indications will not hide the fact that there are some obvious and systemic problems with this aircraft.

There is a reason the a/p is disconnected prior to landing, and hazards of airmass therefrom. Generally, the a/p should be disconnected when entering turbulence as well. Better to not let the a/c try to solve something it cannot fix.

ChristiaanJ

15th Dec 2011, 16:38

Generally, the a/p should be disconnected when entering turbulence as well.
Better to not let the a/c try to solve something it cannot fix.Lieman....,
We got that sorted on Concorde about forty years ago....

http://www.concordesst.com/inside/cockpittour/flightcontrols/pictures/ap13.jpg

DozyWannabe

15th Dec 2011, 16:58

@CJ :

No point wasting your breath (or fingers), he's long since stopped taking any notice of anyone saying anything that does not fit his theory, and cherry-picking bits from other posts that he can somehow twist and work in there.

His argument seems to be that there's a massive cover-up going on - to whit, the BEA are steering the outcome to "pilot error" because they aren't taking into account the shortcomings of the aircraft based on a bunch of things he just made up.

(Not to mention ignoring facts like the existence of autoland since the '60s...)

There's no "TURB" switch on the Airbus FBW series autopilot as far as I'm aware, but the established procedure seems to be to engage the "Mach/Speed" mode when encountering turbulence, as it monitors airspeed much more strictly - discussed here:

http://www.pprune.org/tech-log/468099-flying-turbulence-a320.html

Of course that's not particularly relevant to this case as they had no speed data and thus no A/THR, and even beforehand the thrust remained fairly stable.

Organfreak

15th Dec 2011, 18:23

DW, I too have long-ago lost patience with Lyman's fantasies (quit reading them) BUT!: :uhoh:

I too believe that BEA will make sure that the pilots are blamed. France cannot afford any other outcome. ("Billions and billions.") There is plenty of evidence, though somewhat subject to argument (of course) that there are interface problems with the design, as well as the well-known pitot problem.

Lyman

15th Dec 2011, 19:40

Gents. From Organfreak, I am reminded of an expression that might apply.

Try not to throw the baby out with the bathwater. BEA have been responsible in the past for rigging the results, and utilizing phony data. For a great deal less than the very existence of AIRBUS, and with it perhaps the economy of FRANCE.

If this turns out to be another "Uncommanded climb", Airbus doesn't have franc one to cover the liability. Let alone the criminal exposure.

Someone ran risk/benefit and figured it was worth the exposure. BEA have shown all manner of unprofessional conduct, flaws in the reporting of their data, and parochial "Memoranda" for mere Market share purpose.

I realize it is difficult to entertain such an accusation, but I believe the truth will out, here, and I believe the Pilots will be exonerated.

Just as you believe your defense of the system is worthy, so do I my challenge of it. I harbor no ill will, and as you will note, I continue to refrain from personal attack. For the simple and exclusionary reason that My respect and admiration for you all runs pretty deep. It does not occur to me to attack, except those I believe are culpable for the tragedy.

RetiredF4

15th Dec 2011, 20:07

DW
There's no "TURB" switch on the Airbus FBW series autopilot as far as I'm aware, but the established procedure seems to be to engage the "Mach/Speed" mode when encountering turbulence, as it monitors airspeed much more strictly - discussed here:

At least for the A330 / 340 series, which we are discussing here, you are dead wrong.

LHTTM TURBULENCE DAMPING FUNCTION (bolding by me)

General
The purpose of the Turbulence Damping Function implemented in the Electrical
Flight Control System is to damp the structural modes induced by atmospheric
turbulence.

Architecture
The Turbulence Damping Function consists of two lanes:

Longitudinal lane
The longitudinal Turbulence Damping command is computed by the FCPC1
(FCPC2 as a redundancy) as a function of the Nz accelerometer information.
It is added to the normal law command and transmitted to the
associated elevator servo-controls.

Rear lateral lane
The rear lateral Turbulence Damping command is computed by the FCPC1
(FCPC3 as a redundancy) as a function of the informationof a specific Ny
accelerometer located at the rear bulkhead level.

It is added to the normal law command and transmitted to the
associated yaw damper.

Specific equipment
The equipment specific to the Turbulence Damping Function are:
- the TURB. DAMP pushbutton switch
- the Ny front accelerometer
- the Ny rear accelerometer.

If not convinced, search for it in this doc Airbus overhead panel description (http://www.google.de/url?sa=t&rct=j&q=turbulence%20dampening%20mode%20airbus%20push%20button&source=web&cd=3&ved=0CD4QFjAC&url=http%3A%2F%2Fwww.andytracy.net%2Ffiles%2FAirbusPBs.doc&ei=ZFzqTq7MEpHbsgbmiKysBw&usg=AFQjCNGf8hBqpdNcC_0hPgGeHNgThqguDA) (you have to download the doc) on page 14

system knowledge........?

franzl

Turbine D

15th Dec 2011, 20:13

Lyman

Your Quote:
Generally, the a/p should be disconnected when entering turbulence as well. Better to not let the a/c try to solve something it cannot fix.

Gee, that ought to fix everything when flying at 35K and Mach 0.82

It is getting more bizarre with every post. Here are two quotes that make much sense to me:

1. From Takata Events Leading To LOC (my words)
Illusion, deceleration, and weather.
- Illusion because altitude recorded is "indicated", then partially false at UAS point.
- Deceleration, because autothrust started to reduce N1 by 16% seven seconds before UAS event.
- Weather because there was an up/down/up.

2. From SmilinEd Recovery (my word)
All they needed to do was to:
1. Take a deep breath and watch what the aircraft did under the pitch and power that was set before the AP dropped out.
2. Make gentle corrections to ensure that altitude and heading were maintained within some reasonable limits given the turbulence encountered.

They didn't do either.

Further, Why did they get to where they got to when all this happened (A/P disconnect, A/T disconnect, etc.)? Why did they think the ITCZ was somewhere off in the distance and may have been surprised to find themselves in the middle of it? What were the cockpit conversations, P/F P/NF, not just 5 or 10 minutes before A/P disconnect, but 30 minutes before? Who was monitoring the weather radar? Was it being monitored? Was it set properly? IMHO, this is where the setup to disaster began, but not much has been said about this.

TD

Lyman

15th Dec 2011, 20:36

TurbineD

With utmost respect, take a breath and consider how well both takata and Smilin Ed fold in with my projection of UPSET prior to UAS. A/T was reducing N1 due a severe Updraft, and combined it with a NOSE DOWN input additive. (takata/BEA) And the a/c lost 380 feet. ACARS shows a WINDSHEAR event early on, along with TCAS warn due exit of altitude approved.

Ed is a bit more complex, since the a/c ostensibly, with Inertial recovered data, showed a PITCH resting on 0, (Three degrees+ LOW), and power that was set correctly for an airmass that was markedly different in two seconds from what was indicated and what he felt. In short, the system was dynamic, the AoA was nine degrees delta PITCH, and power was at ~73? STALLSTALL. Sound familiar? This behaviour was patent on other 330's and at least one 340 prior to 447. One cannot with confidence refuse to review patent behaviour in this accident. BEA would have it, and as you know, I trust BEA to be true to BEA past performance.

The past will repeat, especially when there is no incentive to alter the march of the chariots. The aircraft is a long and heavy tube. Which accelerometer was which, again?

Hamburt Spinkleman

15th Dec 2011, 21:27

The Turbulence Damping Function is part of the Flight Control System and not the Auto Flight System. It is normally on and not dependant on an AP being engaged.

There is no autopilot turbulence mode and the Turbulence Damping Function is somewhat different from the TURB autopilot mode of previous non-FBW Airbus. That would disengage pitch mode which would revert to pitch hold while the lateral mode would be retained and THS trim speed reduced.

Turbine D

15th Dec 2011, 21:32

Lyman,

No, N1 was reduced for turbulence penetration by one of the pilots in anticipation of turbulence ahead. I asked PJ2 the question about how this is actually done, moving the throttle levers or another way. It was a pilot initiated action to slightly slow down.

IMO, the A/P was doing what it does, making corrections for ups and downs. At the point of disconnect, it was correcting for an up and therefore the nose was down. From there on, what took place was pilot input. There was nothing wrong with the aircraft or its systems. The reason the A/P disconnected was UAS due to pitot icing, not turbulence. There is no evidence to support the "severe" turbulence theory, but plenty of evidence to support the pitot icing. In fact, I think that will be the #1 issue Airbus will address going forward. I think you will see some technological advances, perhaps on the A320Neo or even the A-350 if the program slips more.

Lyman

15th Dec 2011, 22:01

PF made a slight retard to .80 mach. AIR, that was it from the pilots.

How did the a/c get sideways enough to award a STALLSTALL to PF upon his first stick? His first input was nowhere near "full aft stick" which has become the Urban Myth collective bleat. ACARS, WINDSHEAR? TCAS? There is leeways aplenty for any analysis of the Turb value that the investigator wants. The noise heard by the pilots was not RAIN, nor was it ICE CRYSTALS, or Hail. I think it was a hellish updraft of perhaps 10000fpm, sufficient to start the entire a/c UP at 500fpm in 1.5 seconds. It's on the graph. The aerodynamic noise of an airmass turnaround/shift of 70-90 degrees is......noisy. I think the a/c was on the verge of a Stall, and dropped to ALTERNATE to sustain the NORMALLAWSTALLIMPOSSIBLE meme.

notquite, but you get my drift?

DozyWannabe

15th Dec 2011, 22:08

I too believe that BEA will make sure that the pilots are blamed. France cannot afford any other outcome. ("Billions and billions.")

Rubbish. The aircraft is already a success and the worst they'd face is a few million in repairs - it's not like the whole concept is unproven as the case was in 1988.

Hamburt Spinkleman

15th Dec 2011, 22:09

...PITCH resting on 0, (Three degrees+ LOW)...
That is not correct, the 3°+ that is.

Interim Report #3 page 86 states :

Standard altitude (ft) 34.992
Computed airspeed (kt) / Mach 275 / 0.80
Pitch attitude (°) 2.8
Total weight (tonnes) / Centre of gravity (%MAC) 218 / 27.5

We can see that at the same altitude and speed but 13 tonnes heavier a pitch of 2.8° was required. At the actual weight of 205 tonnes the pitch would therefor have been less. Somewhere between 2 and 2.5°, probably closer to the 2.5 than 2.

...and power that was set correctly for an airmass that was markedly different in two seconds from what was indicated...

Interim Report #3 page 88 states:

2 h 09 min 58 Speed handling changes from managed to selected. The selected Mach is 0.8.
2 h 10 Pitch attitude decreases from 1.8° to 0° in 3 seconds. In 8 seconds, the N1 commanded and the N1 change from 100 % to 84 %.

A reduction in speed from .82 to .80 was selected and the ATS responded accordingly.

AoA was nine degrees delta PITCH

AOA did not reach 9° until approx. 02:10:55, some 50 seconds after AP disconnect and with the aircraft at 37500 ft. It did not exceed 6° untill 02:10:50, some 45 seconds after AP disconnect. See pages 42 and 106 of Interim Report #3.

I am also still looking for references to where those quotes you attributed to BEA comes from. I don't think a "keep looking" will do.

Lyman

15th Dec 2011, 22:23

Old Carthusian

15th Dec 2011, 22:53

BEA have actually done a fine job and having found the FDR and CVR have identified the causes of the accident. This happens to be the flight crew sad to say. Attempts to involved the machine are just grasping at straws and filleting our shoals of red herrings. I like some of the mechanical explanations of the processes but these are not causal factors. Causal factors are lack of CRM, poor training (especially at altitude - as Lonewolf50 and Machinbird have ably identified), company culture, failure to follow SOPs, poor cockpit discipline, no designated pilot in charge when the captain left the flight deck, need I go on. The Air France safety audit which was linked a couple of threads back should be essential reading for everyone wishing to comment. It provides all one needs to know about the causal factors in this accident. BEA are attributing responsibility to the flight crew because that is where the responsibility is. The causal factors are all human factors NOT machine factors. Even the UAS was curable by waiting and following proper procedures. These were not followed and disaster was the result.

exeng

16th Dec 2011, 00:15

If it walks like a duck, talks like duck etc etc; then it probably is a duck.

Having said all that - I flew the A320 in the LH seat for just 2 years. Whilst a brilliant aircraft in many ways I can see how the inexperienced, and perhaps badly trained pilot, could be suckered into this type of event.

It's still a duck though however you wrap it up.

HazelNuts39

16th Dec 2011, 08:28

Lyman,

From BEA Interim Report #e3, p.89: 2 h 10 min 10: The stall warning is triggered. The angles of attack 1, 2, and 3 values are respectively 2.1°, 4.9° and 5.3°.
02 h 10 min 10,4 : SV : “Stall, stall” (without cricket)From the graph on page 42 at 2 h 10 min 10,4: Pitch attitude = 4.2°, V/S = 495 fpm, Updraft velocity = 1124 fpm. That same graph also shows that in the simulation of the sidestick inputs without turbulence the AoA would have reached 4°.

The stall warning threshold at Mach=0.8 has been documented prior to FDR recovery in BEA Interim Report no.2 and in the Air Caraibes memo to be slightly above 4°.

Why is it so difficult to understand that the stall warning was triggered when the AoA exceeded the warning threshold due to the combination of sidestick input and a minor gust?

infrequentflyer789

16th Dec 2011, 13:01

I will take a break, try to find my reference, and return. The "a/c did not immediately climb.." was in reference to the PF's first aft stick, airecall. So it would be post box dump, first analysis, afaik.

It was as BEA first analysed the beginning of the fatal climb.

A few posts ago you were theorising a BEA cover up of "uncommanded climb" and now it's "did not climb when commanded". Which is it ? Can't have it both ways.

BEA went to great lengths to release (unprecedented, I think) public video of the search and recovery, including shots of serial numbers on the sea floor, recovery and storage with police/judicial oversight and multiple observers etc.

I think it is extremely unlikely the flight recorder data is faked, and certianly can't be subject to the same allegations as Asseline made. The data clearly shows commanded climb, and the simulation with the same commands results in the same crash (without turbulence input).

Aside from the loss of airspeed, that particular plane didn't fail on the night, and the crash was down to the pilot input. Whether or not there are design flaws that contributed to that pilot input is a different and more complex question.

HazelNuts39

17th Dec 2011, 10:43

In the Rumours-News forum GerardC refers to NTSB Report DCA09IA064 (http://www.ntsb.gov/aviationquery/brief2.aspx?ev_id=20090706X72654&ntsbno=DCA09IA064&akey=1) which describes A330 UAS incidents to NWA and TAM. Interesting reading, in particular the TAM incident where the crew reengaged the AP when two airspeeds agreed but were still low.

OK465

17th Dec 2011, 13:44

Remember that, in ALT2, the A/P physically cannot be re-engaged.

(ALT1 it can)

ChristiaanJ

17th Dec 2011, 16:11

HN39,
Thanks for posting the link to the NTSB report, just downloaded it into the 'archive' and read it.

roulishollandais

17th Dec 2011, 18:15

"Les cow-boy d'Airbus" is the title of Bernard Ziegler's book... HIMSELF ! :\
preface from Jean Pierson, Edition : Privat (TOULOUSE-France).

This book has been written before the RIO-PAR crash...

"The aircraft cannot stall", aso. :suspect:

BOAC

18th Dec 2011, 10:42

It is interesting to read this, especially the last block 'Who is to blame'

The moment a computer crash nearly caused my car crash ? The Register (http://www.theregister.co.uk/2011/12/15/safe_engineering/)

Smilin_Ed

18th Dec 2011, 21:10

Another reason to have a "BIG RED BUTTON".

Organfreak

18th Dec 2011, 21:29

Another reason to have a "BIG RED BUTTON".

"Oh no....OOPS! I thought it was the autoland!"

chrisN

18th Dec 2011, 21:38

There is no stopping people being stupid, except by selection and training to the extent possible.

The referenced report is a confession by a car driver that he almost got killed on a level crossing when his car was “acting up” – periodically slowing or stopping when supposed to be driving at a normal speed. So what did he do, when it was doing this and he approached a level crossing? “ . . .I decided to plough on forward and try to make it the last 20 blocks to the dealership”. Car drivers are not specially selected, and their (OK, our – including my) training did not and does not include much on fault analysis, nor on decision making.

In aviation, there is selection, and training. But others, professionals, are pointing out that modern training is not covering enough of the old essentials that used to be acquired.

Years ago, I was giving evidence to a UK House of Commons Select Committee about some aviation issues, and I pointed out that, too often, airlines only adopted safety measures if forced to by legislation, or if somebody else paid for it. I quoted as examples rear facing seats and the fatal accident at Manchester (?) where passengers survived the initial crash only to be killed by smoke inhalation – the airlines would not adopt measures to provide safe exit in the event of fire.

Have they now? You know the answer. Do you care? Have you tried to influence any such decisions?

Now, re AF447, many professionals are complaining about economising on training, late replacement of Thales pitots, and some mention not going for optional extra instruments or systems (AI, BUSS IIRC), etc..

I hope those who see deficiencies are raising these issues in their companies, and rousing BALPA etc., and writing to their governments. I should not have been alone, and from GA rather than professional aviation, in my representations to that select committee.

IMHO.

Old Carthusian

18th Dec 2011, 22:33

Sadly for those who would like to believe so we have no evidence that the accident was caused by anything other than pilot actions. Furthermore, this evidence is not likely to be faked or incomplete. What we do have is serious deficiencies in airline procedures and piloting skills which may or may not extend to other carriers besides Air France. There is some anecdotal evidence that training and piloting skills have been neglected outside Air France as well. However, this is an cultural issue not a complexity issue. It is possible to encourage a culture of excellence and professionalism and to reward this. Certain airlines fail to do this and Air France are just the latest example.

hillberg

18th Dec 2011, 23:27

AirBus should be Russian, Here the plane flys you.

Machinbird

19th Dec 2011, 05:26

Recently I theorized that AF447 suffered a roll PIO condition that completely overload PF's ability to control other axes of the aircraft.
While looking for a definition of PIO to compare against the BEA data, I came across a relatively recent paper showing how thinking is moving on the subject of PIO. You can read the paper here (http://aristotel-project.eu/fileadmin/aristotel/public/deliverables/ARISTOTEL-266073-D1-1-Background_definition_and_Classification_of_ARPC-V3-31-12-2010.pdf). Aircraft and Rotorcraft Pilot Couplings – Tools and Techniques for Alleviation and Detection (ARISTOTEL)
Among the key points in the paper are:
An aircraft- or rotorcraft-pilot coupling (A/RPC) is an unintentional (inadvertent) sustained or uncontrollable vehicle oscillations characterized by a mismatch between the pilot’s mental model of the vehicle dynamics and the actual vehicle dynamics. The result is that the pilot's control input is out-of-phase with the response of the vehicle, possibly causing a diverging motion.and
It can also be said that in normal situation, the pilot drives the vehicle, whereas during an A/RPC event the situation is reversed. In that case, the pilot is driven by the vehicle due to this mental mismatch and actively tries to control it

Based on the many comments from the industry, [ref. 6] suggested the following ten features (definitions) characterizing virtually every APC documented in the open literature:
1.
PIO is a sustained or uncontrollable unintentional oscillation resulting from the efforts of the pilot to control the aircraft. This is the MIL-STD-1797A definition, with the word “unintentional” added.
2.
PIO occurs when a response state of the airplane is approximately 180 degrees out of phase with the pilot. It could be any response state of the airplane, the most common for fixed wing aircraft are pitch attitude, roll attitude, and load factor [ref. 6]
3.
PIO is an event that results from faulty aircraft design, extension of the airplane’s operational usage into an area for which it was not intended, or following a failure, and is not the fault of the pilot.
4.
PIO is commonly found to be related to deficiencies in basic flying qualities characteristics, though it should be treated independently from flying qualities. Most PIOs outside of the research world are related to rate limiting of a control effector or software element upstream of a control effector, but rate limiting can be both the cause of PIO and the result of it.
5.
PIO may be either constant-amplitude, convergent, or divergent with time.
6.
PIO may be any number of cycles of oscillation; there is no minimum number to declare it a PIO.
7.
PIO may occur at very low frequencies – near the phugoid mode in pitch – up to frequencies of around 3 Hz (“roll ratchet”). The most common frequency is in the range for pilot closed-loop control, typically 1/6 Hz to slightly above 1 Hz (1 rad/sec to 8 rad/sec), but frequency alone does not determine whether an oscillation is a PIO.
8.
High-frequency, small-amplitude oscillations in pitch (sometimes referred to as “pitch bobble”), and in roll (“roll ratchet”), may be considered a “mild” form of PIO, and may not even be judged as PIO in all cases. If the amplitudes of the oscillations become intrusive on the piloting task, they are PIOs.
9.
PIO that interferes with, but does not prevent, performance of a primary mission task is a “moderate” PIO; if a Cooper-Harper Handling Qualities Rating 7 is obtained, it is usually in the range of 4-6 (Level 2 by handling qualities specifications). In general, “moderate” PIO is associated with peak-to-peak angular rates of less than ±10 degrees/sec and control forces less than ±5 lb.8 “Moderate” PIO requires corrective action for normal operation of the airplane, but if it occurs in developmental testing the flight test program can continue.
10.
PIO that prevents performance of the task, or that requires the pilot to abandon the task in an attempt to stop the oscillation, is a “severe” PIO; if a Cooper-Harper Handling Qualities Rating is obtained, it is usually 7 or worse (Level 3 or unflyable by handling qualities specifications). Peak-to-peak angular rates are usually greater than ±10 degrees/sec, and control forces greater than ±10 lb, though rate limiting can attenuate the former and result in large increases in the latter.8 “Severe” PIO requires immediate changes to the airplane, and if it occurs in developmental testing the flight test program should be postponed or redirected until the corrections are made.

Machinbird

19th Dec 2011, 05:52

Using BEA roll data for the period 2:10:07.5 through 2:10:45, the following graph describing the amplitude of the roll oscillation was prepared:

http://home.comcast.net/%7Eshademaker/RollAmplitude.jpg
The amplitude is the total roll motion in degrees following a reversal of the roll rate. It is obvious that he was beginning to get a handle on his roll control problem when the aircraft stalled and created a new set of control problems.

HazelNuts39

19th Dec 2011, 07:23

Machinbird,

The result is that the pilot's control input is out-of-phase with the response of the vehicle, possibly causing a diverging motion. Is it?

grity

19th Dec 2011, 10:45

@machinbird

PIO
1 unintenditional YES
2 PF stears exact 180 deg out of phase
3 extension of the airplane’s operational usage into an area for which it was not intended, or following a failure, and is not the fault of the pilot
4 IMO .......software element upstream of a control effector.....???
5 divergent with time, after 2:10:07
6 number of cycles of oscillation ??? more than 5 ???
7 The most common frequency is in the range for pilot closed-loop control.... here it was 1/3Hz
8 1/3 Hz is not high frequency it was not "mild PIO"
9 roll ratchet...... >10 deg
10 Peak-to-peak angular rates are usually greater than ±10 degrees/sec, and control forces greater than ±10 lb, though rate limiting can attenuate the former and result in large increases in the latter.8 “Severe” PIO requires immediate changes to the airplane, and if it occurs in developmental testing the flight test program should be postponed or redirected until the corrections are made. YES we wait

Old Carthusian

19th Dec 2011, 10:48

Machinbird

19th Dec 2011, 14:16

This article seems to define the phenomenon as being anything that authors wish it to be. The evidence is shakey and in some places totally worthless and someone has clearly wasted money commissioning the article. Definitely part of the shoal.
I was expecting this type response. Typical hairy-chested "just fly the aircraft" comment of someone who has never encountered PIO because his aircraft experience involves highly damped flying machines.

My first knowledge of PIO was a news clip explaining how the Navy had lost a Sea Dart aircraft during a high speed flyby.
Later, while assigned to a Test and Evaluation facility, one of the engineers led me to the original full accident report on the Sageburner F-4 PIO accident.

I've personally never encountered PIO inflight, but have experienced roll PIO while flying an early visual simulator with a ~1/3 second visual display computational lag. Disconcerting to say the least. I had to go back to the flight instrument display to regain control. (Note: These were actual instruments-not on the visual display). Small motions did not trigger the PIO, but rapid-high gain lateral motions did. Until you experience the effect, you would have trouble believing it could happen. The onset is sudden. When it does happen, you tend to blame yourself because you are "in control."

The paper I referenced earlier has very little in new concepts. The new part involves the "pilot's mental model of the aircraft" wording. It does an excellent job of bringing together available information on the subject of PIO. The AF447 initial "roll problem" seems to fit the 10 PIO characteristics listed in the paper, but I'll let BEA make the determination, They have better versions of the data.

And for the conspiracy theorists, if BEA does not comment on roll PIO in any manner, either to affirm or deny, then you will have a red flag indicator.

Machinbird

19th Dec 2011, 16:27

The result is that the pilot's control input is out-of-phase with the response of the vehicle, possibly causing a diverging motion.
Is it?
Actually it is very close to 180 out most of the time until he gets it under control but it is converging, not diverging
If you look at the reversal intervals, PF starts out reaching his maximum control input shortly after reaching his roll max angle for a particular oscillation, and he is able to gradually gain on the oscillation so that he is actually leading the oscillation, at which point the amplitude starts to die down, only to have the oscillation flip phases on him. and go through another (smaller) cycle. At least, that is the way I read it.

ChristiaanJ

19th Dec 2011, 16:31

Machinbird,
Thanks for the link!
A bit laborious, as articles go.... but it covered the subject quite well for this ancient flight control engineer (Rtd.), complete with Bode plots and suchlike, which tell the story faster and clearer to those who can read them, rather than long verbal descriptions.

And for those who've never experienced PIO : 'hands up' for those who've never experienced DIO either (driver-induced oscillations, speed or direction) after hitting a couple of pot-holes or speed bumps.....
Been there, done that (luckily on local country roads, without disaster ensuing).

Sure, it's not the same. But it gives you an insight into how a vehicle you are confident of being in control of (near perfectly) at the time, can suddenly acquire a mind of its own....

Old Carthusian

19th Dec 2011, 22:14

Machinbird
I have stated earlier that I see merit in your suggestion but that I see it on a mechanistic level - an explanation of how the phenomenon worked but not a casual factor. This is my main objection to the paper you linked. It was too vague and too inclusive. The phenomenon wasn't adequately defined (it could be anything seemed to be the message) and it seemed to want to attribute an overly deterministic approach to a pilots actions. In other words the pilot was not responsible for his actions and a helpless victim of PIO. One is forced into the question why have pilots then? Are they truly unable to take decisions and judge a situation? I tend to believe that a pilot has responsibility for his/her actions and that a statement like 'is not the fault of the pilot' (Conclusion No. 3) is just as dangerous and misleading as 'is the fault of the pilot'.

We end up returning to the human and cultural factors of training, CRM, SOPs, chain of command. You mentioned you experienced PIO in the simulator and how you solved it by using your instruments. This seems to have been lacking from the PF - as I stated before know your machine and trust your instruments. It's a training and cockpit discipline issue and the paper seems to make no mention of this. You yourself mentioned training and I would add practice - skills atrophy without use. Once again one is forced back to the conclusion that this was a poor crew who took a perfectly flyable aircraft and put it into a non flyable state. Whether they were a one off or indicative of a broader trend is open to debate. Of course the crew were poorly served by their employer - Air France; and the Air France safety audit indicates serious cultural issues developing in their pilot corps. One hopes that Air France are addressing these as a matter of urgency.

If BEA do not reference PIO as a factor it won't be because they have an agenda but because they don't consider it germaine. That too is a legitimate judgment.

Machinbird

20th Dec 2011, 00:16

I have stated earlier that I see merit in your suggestion but that I see it on a mechanistic level - an explanation of how the phenomenon worked but not a casual factor. This is my main objection to the paper you linked. It was too vague and too inclusive. The phenomenon wasn't adequately defined (it could be anything seemed to be the message) and it seemed to want to attribute an overly deterministic approach to a pilots actions. In other words the pilot was not responsible for his actions and a helpless victim of PIO. One is forced into the question why have pilots then? Are they truly unable to take decisions and judge a situation? I tend to believe that a pilot has responsibility for his/her actions and that a statement like 'is not the fault of the pilot' (Conclusion No. 3) is just as dangerous and misleading as 'is the fault of the pilot'. OC, lets try the following concept on for size. Don't worry how the situation occurred, just how the pilot handles it once discovered:

As you lift off the ground, the aircraft rolls the wrong way in response to your roll inputs. If the pilot is not able to override his natural tendency to correct a roll to port by moving the stick to the starboard side of the cockpit, is it then his fault that the aircraft crashes? Shouldn't he be able to rewire his brain on a moments notice to reverse the response?:rolleyes: That is exactly the situation a pilot facing PIO encounters. His learned responses don't quite fit the situation any longer. If you encountered this type of situation, would you also be able to remember your aerobatic training to put the stick forward while inverted to keep from losing altitude? This is similar to the kind of control problem the AF447 PF may have faced (albeit a bit more extreme.)

If BEA do not reference PIO as a factor it won't be because they have an agenda but because they don't consider it germaine. That too is a legitimate judgment.
The roll behavior after the autopilot dropped is extremely anomalous. If BEA does not address why it occurred, then they would be putting their heads in the sand. There would be a lot of people asking hard questions then.

3.
PIO is an event that results from faulty aircraft design, extension of the airplane’s operational usage into an area for which it was not intended, or following a failure, and is not the fault of the pilot.This is the paragraph that you are objecting to. PIO really is a design problem and can be tailored out of the control system if known. If there was not a test point that stimulated the PIO tendency in that corner of the envelope, it may not have been uncovered during the flight test program and subsequent line flying. PIO is very dependent on pilot technique. For example, if a pilot is attempting to damp out a rate of motion, his control strategy is different than if he is attempting to hold an attitude.

Saying that PIO is not the pilot's fault is not the same as saying that PIO is not the pilot's problem. As you well know, when airborne, there is no one available to save you from your predicaments but you. By saying it is not the pilot's fault, the paper indicates that is up to the airframe maker and certifying authority to evaluate the problem and ensure necessary corrective action.

Old Carthusian

20th Dec 2011, 01:32

Machinbird
Sounds rather 'Camelish' (the said biplane used to pull to the right due to the torque of its Bentley engine). Are you saying that the control response is tardy and that the pilot's reactions are too quick? It has all the flavour of panic and forgetting how the machine actually flies. Those who have commented on flying the Airbus family particularly the A330 comment that it is a very stable aircraft in all aspects of its flight envelope. Therefore for your theory to work as a causal factor there would have to be a hidden design flaw which was not spotted in flight testing. I doubt this and fall back on the explanation that the PF (for some reason) lost it and overreacted terribly. The aircraft is going to respond to the pilot inputs and these are what caused the rolling - not the aircraft. A thorough rereading of the CVR transcript might help here. There is a disturbing lack of professionalism manifest throughout the sequence of events and the rolling is just a symptom of this.
What is missing from Conclusion No. 3 is the word 'can' because PIO can also result from a panicking pilot 'mayonnaise stirring' without the aircraft having any blame (as it were). However, I picked that conclusion out because it was an excellent illustration of the sloppy language used in the paper. What the PF needed to do in the AF447 situation was wait and analyse then act. He panicked and flopped around hopelessly and his colleague who could have taken command (as he seems to have understood the situation better) did nothing. No CRM, cockpit discipline, SOPs, chain of command. I keep on repeating this sorry to say but these factors are there for a reason - so that pilots do not get into messes when faced with unfamiliar situations. Simply a training and cultural issue - if you have the time take a look at Pan Am (late '60s early 70's) and Korean Airlines (1970s to early 2000s) for just how nasty these things can get.

Machinbird

20th Dec 2011, 02:11

Those who have commented on flying the Airbus family particularly the A330 comment that it is a very stable aircraft in all aspects of its flight envelope.
OC,
Consider what percentage of the A330 flight time that has been accomplished has been in Normal Law, Now consider what percentage of that has been flown on Autopilot.

Then consider what percentage has been in Alt 1 Law and in Alt 1 Law with Autopilot.

Finally, consider what percentage has been in Alt 2 Law (Autopilot cannot engage)

Assuming manual control, does the aircraft feel the same way in Alt 1 Law as it does in Normal Law? I believe the answer is yes, just the protections operate differently.

Assuming manual control, does it feel the same way in Alt 2 Law as it does in Alt 1 Law? No. Roll response is different.

Other than the test flight program. I would be surprised if the aircraft has accumulated 10 hours of flight time in Alt 2 Law during its entire line flying lifetime.
But those that may know better should feel to correct any misperception on my part.

If I am correct, the bulk of A330 flight experience would not be relevant to AF447's loss of control in Alt 2 Law.:confused:

Old Carthusian

20th Dec 2011, 02:26

Machinbird

20th Dec 2011, 04:12

Machinbird
If you will forgive me the use of my favourite metaphor; that is a particularly juicy red herring. Just because most of the flying may be done in Normal Law doesn't mean that no flying is done in ALT2. It possibly is more than 10 hours but I don't know. However, be that as it may, a properly trained and conversant crew should have no trouble using the aircraft in ALT2 law. Those who have tried to fly it in such a state and who have posted say that it flies well. It was designed by Airbus to fly well - you can be sure of that. It would never have been certified if it was an absolute pig to fly without protections. Once again it's a training issue which should have been addressed in the simulator. If it wasn't then again it's a training issue. Pause, diagnose (using your instruments) then fly. But then I am afraid that this crew would have flown anything into the ground.
OC, I might share your faith in the reliability of the certification process except I have seen examples of the subtle ways things can sneak through, only to be found later, usually under adverse circumstances.
There is a reason that the referenced paper has this quote
“The design process of the airplane has matured, flight control systems have evolved, criteria and analysis techniques are available, yet PIO persists.”PIO can be hard to reliably predict and prevent considering the various different control strategies employed by the pilots flying a particular type of aircraft. (But at least the autopilot should follow its programming in a reliable and predictable manner.)

Training can help pilots avoid unsafe control strategies, and can teach them what to do if they recognize a PIO condition. Has anyone received such training?

PIO recovery:

For example, in B type aircraft, the PNF can assist in breaking a PIO by helping hold the control wheel steady, but in newer A type aircraft, this is not possible.

In either type aircraft, PF can back out of the oscillation by loosening his grip on the controls, reducing the amplitude of his control inputs, and even releasing the controls completely until a PIO dampens out.

On either type of aircraft, exchanging roles between PF and PNF may change control strategy sufficiently to break a PIO. (This would have likely have been the best way to help in the AF447 situation).

Meanwhile I think we can collectively make some good use of your pet herring. I'll bet he's tasty.:}

Old Carthusian

20th Dec 2011, 05:08

“The design process of the airplane has matured, flight control systems have evolved, criteria and analysis techniques are available, yet PIO persists.”

Certainly it does but that is because it is pilot induced. It sounds a bit facetious - I am not trying to be so but point out that this is not nowadays a design issue so much as a human issue. There is nothing I can see in the accident which can be attributed to the aircraft. A different approach to training is probably the answer and proper CRM but the design oriented approach will not work in most cases because of the human factor. There will always be someone who finds a way to crash an aircraft in a totally unexpected way. In the end it still comes down to the man at the front.

jcjeant

20th Dec 2011, 05:38

You can train crew as many as you want
You can teach CRM as many as you want
Even if the crew of the AF447 was super trained to cope with all situations you can think about ... it was useless in their case .. cause they never recognized in which situation they were ...
They never understand what was happening .. so they were unable to apply any procedure .. learned or not ...
They were like children playing with buttons and levers .. and hopping something nice will happen ...

Machinbird

20th Dec 2011, 06:17

Certainly it does but that is because it is pilot induced.

OC, as long as you hold that belief, you will have the PIO cause and PIO effect reversed. But you know that and in the big scheme of things it will probably make no difference- unless you encounter PIO yourself.

The training factors are significant in the failure of AF447's crew to recognize and declare a stall, but if they encountered roll PIO during the transition to ALT2 Law, that could be the reason that they did not/could not fly pitch and power successfully and lost track of their energy.

Remember this paragraph from the Aristotel report?

10.
PIO that prevents performance of the task, or that requires the pilot to abandon the task in an attempt to stop the oscillation, is a “severe” PIO; if a Cooper-Harper Handling Qualities Rating is obtained, it is usually 7 or worse (Level 3 or unflyable by handling qualities specifications). Peak-to-peak angular rates are usually greater than ±10 degrees/sec, and control forces greater than ±10 lb, though rate limiting can attenuate the former and result in large increases in the latter.8 “Severe” PIO requires immediate changes to the airplane, and if it occurs in developmental testing the flight test program should be postponed or redirected until the corrections are made.

According to my decaying math skills, initial peak roll rate was on the order of 10 degrees per second for the first 4 oscillation half cycles but if someone would like to look this aspect over more closely, I would appreciate it. I can see evidence in the roll position record that PF's attention was heavily devoted to this problem. (Changing his strategy & adaptation.)

Old Carthusian

20th Dec 2011, 11:17

Machinbird

'throughout the flight, the movements of the elevators and the THS were consistent with the pilot’s input'
BEA Third Interim Report

It is important to recall that the pilot was the one who was making the inputs. This is where the Aristotel report falls down and badly in that it assumes that these inputs are a result of factors that can be designed out rather than factors that rest in human entities. One can almost say that it is written to the requirements of a pilots union. Rereading the 3rd Interim report we have a clueless PF and a PNF who doesn't feel he has the authority to intervene even though he seems to understand what is happening (as jcjeant succinctly notes). The more important document here is the Air France safety audit. It identified cultural issues that would lead to such a series of events. I'm not going to discount PIO entirely but it doesn't fit the circumstances of the accident and would not rate as a causal factor.

Machinbird

20th Dec 2011, 12:58

'throughout the flight, the movements of the elevators and the THS were consistent with the pilot’s input'
BEA Third Interim Report
In other words, the motions of the control surfaces were consistent with the pilot's control inputs (i.e. no unexpected control system inputs)......but that says nothing of the dynamics of what the control inputs did to the aircraft. From the same report's data, it also appears to have set up a roll oscillation.

OC, What you do not seem to realize is that the Aristotel paper builds on a long history of professional thought on the causes of PIO. This is not a report that just "appeared out of the blue".

That is not an assumption that PIO can be designed out of a particular aircraft's control system-you can take that as a fact, but first it has to be recognized so that it can be addressed. Pilots who blame themselves for all aircraft handling problems are one of the reasons not all PIO problems are addressed.

I will concur that the crew of AF447 seemed to be clueless about a large body of fundamental aviation knowledge that night, but I suspect recognition of a PIO context for their initial manual control performance will explain how they lost control. It may even help explain why they failed to regain control, although the aircraft was then in a stall and no longer subject to PIO. But this area is one for the human factors experts.

grity

20th Dec 2011, 13:09

MB, Actually it is very close to 180 out most of the time until he gets it under control but it is converging, not diverging
If you look at the reversal intervals, PF starts out reaching his maximum control input shortly after reaching his roll max angle for a particular oscillation, and he is able to gradually gain on the oscillation so that he is actually leading the oscillation, at which point the amplitude starts to die down, only to have the oscillation flip phases on him. and go through another (smaller) cycle. At least, that is the way I read it.
180 deg is the way you move on the swing set if you will hold the swing-amplitude, if you will stopp you try to move in 90 deg (or 270 ???)
http://www.elsenbruch.info/ph12_down/Amplitude_Schaukel.gif

if I put together HN´s vertical wind velocity and the roll altitude, then both cange with the same frequency of 1/3 Hz

we do not know much about the turbulent air in this case, but it is truly not one uniform mass which moves up and down, it might be that it was one vortex with the dimension d +/- 800m...... if they flew cross through it, the vertical wind velocity is explicable...

but what will be if they flew alongside of some vortex with this dimension and this frequency? changing different AoAs at both wings with 1/3 Hz..... VIO

the PF did not beginn with this oscillation, with the stick he just helped to hold the roll-amplitude.... (and forgot to control the pitch....)

http://s1.directupload.net/images/111220/temp/yutzngap.jpg (http://s1.directupload.net/file/d/2744/yutzngap_jpg.htm)

DozyWannabe

20th Dec 2011, 20:28

I don't know if "forgot" is the right word. No matter how incorrect the pitch inputs were they were very positive, and way in excess of what should be expected at that altitude.

Even with protections out, the airframe itself is very stable - with 20/20 hindsight, the correct response should have been to understand what the turbulence was doing and very gingerly make small corrections once that was understood and a "feel" for the situation was gained. Instead it looks very much like every control input was reactive to each individual bump - possibly resulting in PIO in the lateral axis, but in my opinion there's not enough evidence to say one way or the other.

The main problem is that the response was very instinctive in nature, but not being trained in high-altitude handling the risk was that the response itself was likely to be inappropriate and excessive because the only manual handling the PF was used to was at low altitudes and commeasurately more extreme in terms of sidestick deflection.

As far as I'm concerned though, this is all by the by. The main problem was organisational in nature - Air France operating a type which was known to have potential issues requiring manual handling at cruise level (until fleet-wide repairs were effected), yet nevertheless rostering crews in such a manner that if such an event happened, the flight deck could potentially be manned by a crew without the required experience to recover correctly. That - based on the information we have so far - is the primary reason that control was lost and the aircraft crashed. The details of how that loss of control developed, while useful to understand, are at best a set of contributory factors.

Old Carthusian

20th Dec 2011, 21:59

Machinbird
I don't think we'll agree on this and to my mind it's because of a fundamental difference in the way we're looking at things. I am looking at the actions of the PF as those of a being capable of making independent decisions unaffected by external factors. Your approach seems to be more deterministic - the PF is subject to factors which force him to act the way he does. To a large extent he has no control over what he does.
Whilst both views have a measure of validity the (shall we say) free choice view is a far better and more realistic model for explaining things. The interesting paper you mention is problematic in that it reduces the human element to a 'cog in the machine' as it were but this is symptomatic of the whole PIO approach. It is logically flawed as a concept in that it assumes no choice of action. As I have mentioned, as a piece of research it is woolly and far too broad in its spread. Choices exist but how we exercise them depends on our training, professionalism or the culture we follow. But and this is the important thing - we always have the choice. This is the case with AF447 - the pilots had choices but ignored them.
Sorry for the philosophical digression but I felt it was relevant in this case.

ChristiaanJ

20th Dec 2011, 22:58

OC,
You sound as if you have never experienced PIO (or DIO, as I mentioned earlier).
You have no 'choice' at that moment.

Machinbird

20th Dec 2011, 23:35

I don't think we'll agree on this and to my mind it's because of a fundamental difference in the way we're looking at things.
Yes, I agree wholeheartedly.

I am looking at the actions of the PF as those of a being capable of making independent decisions unaffected by external factors. Your approach seems to be more deterministic - the PF is subject to factors which force him to act the way he does. To a large extent he has no control over what he does.
We are capable of making choices/decisions as reasoning beings, but in the heat of battle, it can be too late to make relevant choices. Much of what we do is pre-programmed (trained if you will) based upon earlier choices. When that training conflicts with reality, it can be too late to change your mind on your course of action, especially in aviation. That is what Christian was just alluding to, and what I was alluding to with the reversed roll control scenario.

Old Carthusian

21st Dec 2011, 00:30

Machinbird + ChristiaanJ
The choice is to act or to delay your action. There is a belief that by acting quickly you can deal with the problem (and this is indeed the case in some situations) but more often than not it is better to pause and evaluate. This is frequently the case with DIO. One thinks of the supposed Prius issue which turned out to be driver induced. Drivers panicked and blamed the machine for their actions where taking their foot of the accelerator would have solved the problem.
With aircraft a pause with a light touch works wonders. Of course I agree that sometimes it isn't possible but most of the time it is. In the AF447 example there was ample time for the PF to pause and evaluate. He didn't and so ended up in a stall. But what we do have here is a training and possibly experience issue not an aircraft issue. The aircraft did what the PF told it to do. If the pilot had left things, the aircraft would have most likely stayed in a stable condition within its flight envelope. A properly disciplined and non-panicking pilot would have paused, evaluated and then followed the SOP for UAS. He would have worked in concert with his colleague to find a solution. PIO isn't the issue here (except as a mechanical process) but the pilot's conduct is (I am sorry to say). A look at the Korean Airlines Flight 8509 accident shows how a competent crew dealt with a roll issue due to an aircraft fault (I am referencing the first crew not the second). But in AF447 we cannot escape the issue of crew competence or rather the lack of it.

Machinbird

21st Dec 2011, 01:25

OC
I'm not entirely rejecting what you have just said, I prefer the firm&positive well considered method of operating flight controls, but I do have a lot of frightening incidents engraved on my eyeballs that are visible when I close my eyes.
Sometimes you have to act NOW, because there is no time to consider. How does one figure out which is which? I think the answer is experience and exposure.

I do not place AF447 in that category, however.
It seems that PF on that aircraft went to full respond mode when he was roused from his relaxed cruise state. The initial control movements are far too large-for what he was up against. Maybe the cavalry charge music had something to do with it? ;)

Diversification

21st Dec 2011, 20:22

The SAAB company took a patent may years ago on a method to prevent PIO (after the 2 JAS 39 Gripen PIO accidents), but normally this seems to be simply done by rate-limiting in the software. I don't know which method is used in the A330:ies.
I have been wondering if any such PIO-preventing function, which ought to be in operation in normal law, is still operational in alt law 2.
PIO can apparently also occur if the hydraulic system is overloaded by extensive control surface movements, especially shortly after a reduction in N1.

Keep up the interesting and good parts of the discussion.

RR_NDB

21st Dec 2011, 21:33

Machinbird,

New Background Information on PIO (http://www.pprune.org/tech-log/468394-af-447-thread-no-7-a-35.html#post6908708)

Excellent work (http://aristotel-project.eu/fileadmin/aristotel/public/deliverables/ARISTOTEL-266073-D1-1-Background_definition_and_Classification_of_ARPC-V3-31-12-2010.pdf) on a fascinating issue,

Thanks, :ok:

Machinbird

22nd Dec 2011, 01:50

OC, I don't wish to belabor this point unduly, but you really do not understand the problem of what PIO is. If we were to completely accept your viewpoint, we would throw the work of several generations of aircraft handling specialists into the dumpster as an unnecessary complication.

The roll oscillation on AF447 which I suspect may have been PIO was a converging oscillation. There are other oscillations that diverge and are nothing to be trifled with.

Take a look at this video clip of the Sageburner accident and tell me how well your strategy of deciding to do nothing would have worked. This video is a pale imitation of the original phototheodolite film. On that film, the photointerpreters could clearly read out actual stabilator position and thus infer stick motions.
F-4 PIO - YouTube (http://youtu.be/RhLq4jf_tc4)

Machinbird

22nd Dec 2011, 02:42

RR_NDB, I think we owe OC a vote of thanks for his reasoned challenge to my points.:ok:

Being forced to defend a concept requires both parties to explore their thoughts carefully and to develop them to a greater degree than if there were no challenge.

PIO or APC or whatever you wish to call it is a very interesting topic, and produces many surprises. I am pleased that others find it interesting too.

In the case of AF447, the initial roll oscillation stands out as a very strange thing. It will be interesting to see what BEA makes of it.

airtren

22nd Dec 2011, 02:44

....

The roll oscillation on AF447 which I suspect may have been PIO was a converging oscillation. There are other oscillations that diverge and are nothing to be trifled with.

Machinbird,
I should have commented earlier. ...

I've read your recent posts with interest. Excellent work.

Thank you for bringing it forward, and thank you for your patience.

I mentioned this opinion before, that that the full set of technical elements involved in the AF447 (and other accidents), will be a reunion of those enumerated, and made public by BEA and those tacitly recognized and addressed by the manufacturer in improvements/enhancements coming with new versions.

OK465

22nd Dec 2011, 03:05

Old Carthusian

22nd Dec 2011, 04:04

Machinbird
It has indeed been a fascinating discussion but I would still question the involvement of PIO in this case. The sageburner accident is indeed interesting but is it relevant? A high speed jet fighter going for a low altitude speed record? You are almost certainly more conversant with the design philosophy of the F4 than me but I would have thought that it was designed to be very responsive to control inputs - more so than a civilian airliner. Maybe for the pilot to have stopped the control inputs would have helped but once again I suspect you would be more knowledgeable on this point. However, PIO seems to be a phenomenon which affects small manoeuverable aircraft more than civil airliners (referencing the database in the Aristotel article). But even so with a small fast manoeuverable machine it is often better to 'let go and hold back'. I fully acknowledge your point that sometimes you have to act quickly but for most cases this would not be my approach.
OK465, I think, hits the nail on the head. The A330 is not a machine designed to be flung around. It is rather an aircraft designed to fly in a stable manner. Leaving the aircraft alone was the correct approach in this case - it would not have remained in its unstable state. A light touch on the controls if it threatened to roll too far but the roll amplitude was not excessive or too radical. PJ2 who commented on the incident in I believe the third thread of this subject advocated this approach and I would bow to his knowledge. I still find myself coming back to the crew behaviour in this accident. The complete lack of CRM cannot be disregarded and this is a more significant factor than any supposed PIO (and we must be honest we have no evidence of PIO in this accident - we have hypothesis but that is all). Remember in your experience in the simulator you were able to overcome PIO by use of your instruments (and I would assume a pause but do correct me if I am wrong). The PF in this case did not pause (a cavalry charge as you say) and does not seem to have had a scan and crucially to have ignored his copilot. This is the crux of the matter - a seeming panic reaction by both the flight crew.

Machinbird

22nd Dec 2011, 04:16

We're talking about a heavy, inertia laden aircraft at 265 knots, which is decelerating, with an initial max available roll rate in roll direct of less than 20-25 degrees per second (max rate is available at about 320+ KIAS clean, less on down). Rate-wise even at full SS deflection the thing is a slug.
Yes it is a very stately slug. The problem comes from the difference between expectations of the PF versus what the aircraft actually did.

At altitude, roll damping is lower. Did PF understand he was in roll direct? Did he have appropriate training in flying in a roll direct law? Even sluggish aircraft can be overcontrolled or oscillate, they just do it slower, but they still oscillate.

Whether fighter or transport, 900 knots or 300, these things are aircraft and aircraft oscillate if not properly controlled. For an aircraft the size, mass, and control power of AF447, the roll oscillation it encountered was surprisingly quick, but the roll did not reach significant angles until after the stall. This may have deterred PNF from intervening.

The difference between divergent and convergent PIO is the amount of damping available. If the oscillation is building energy, bad things are going to happen as they did in the Sageburner accident. At some oscillation frequencies, pilots cannot effectively intervene.

OC, we are in full agreement that PF came on too strong when he took control. The problem appears to be that his initial mistake was not easily reversed.

The one surprising thing I learned reading the Sageburner file was that the aircraft was headed for an 8 g peak when the pilot released the stick in an attempt to break the oscillation. The aircraft had been trimmed in the alignment turn, and the additional nose up stabilator motion caused the aircraft to breakup somewhere around 15 g.

FWIW, On my roll PIO experience in the visual simulator, the only pause was the minor delay in visually locking on to the attitude indicator.

Organfreak

22nd Dec 2011, 05:25

OC:
...However, PIO seems to be a phenomenon which affects small manoeuverable aircraft more than civil airliners (referencing the database in the Aristotel article).

How about this, then? A bigass Boeing:

PIO jet airplane landing - YouTube (http://youtu.be/zxWs9TWfRLA)

RR_NDB

22nd Dec 2011, 05:52

Feedback Systems are inherently complex. When you introduce human inputs specially of high amplitude the results can be dangerous.

Anyway when you don' t know for sure all the "inputs" the PF "received" it's risky to conclude.

We are talking of a complex scenario with a crew (PF/PNF) lacking the training for the situation.

I love the KISS approach but for this analysis we must consider everything plausible and PF was reacting to stabilize.

Unfortunately due CRM, "tunnel effect", difficulties due "auto THS", use of SS or just panic then the entire crew failed to timely act properly or even "understand".

I understand MB comments on oscillation as a possible complex factor. OTOH in general i agree with many points OC put.

PS

I tend to respect too much all kind of oscillations or "transients" leading to dangerous situations or crashes, mostly the ones affected by human beings inside the feedback loop introducing extra "inputs".

Remember me the "butterfly region" . I feel "butterflies" in stomach when imagining what can happen.

In general, "laissez faire" is safer, i agree. But in some cases you must act decisively.

Which ones? How to manage in "degrading modes" not perfectly timely understood.

Acting decisively avoided me two serious car crashes. And subsequently i had to stabilize the vehicle. And was very difficult and requiring extremely dangerous maneuvers. Full of adrenaline in the end.

May be applying precise and ABSOLUTELY NECESSARY inputs, proportional to the surprise in the beginning.

When confused, better to wait and see.

This remembers me about people*:

Intelligent and active, no problem

Intelligent and passive, no problem.

Dumb and passive, no problem.

Dumb and active, extremely dangerous...
:E

(*) A friend told me about people entering the Army.

Old Carthusian

22nd Dec 2011, 06:28

Organfreak
..However, PIO seems to be a phenomenon which affects small manoeuverable aircraft MORE than civil airliners (referencing the database in the Aristotel article).

Machinbird
I do believe the PF understood he was in ALT2 - after all he calls "I have the controls" (which I interpret as an acknowledgment of the switch) but if he didn't that was also an indication of poor flight deck management and serious training deficiencies.
I think we are all in agreement that sometimes you must act and act quickly. Getting that right depends on your experience and training and here I think the latter let the flight crew down. I am afraid the PF's behaviour fits RR NDBs fourth category.

Diagnostic

22nd Dec 2011, 16:32

I do believe the PF understood he was in ALT2 - after all he calls "I have the controls" (which I interpret as an acknowledgment of the switch) but if he didn't that was also an indication of poor flight deck management and serious training deficiencies.
Personally I do not believe the PF's call of "I have the controls" (in French) was acknowledgement that he was in ALT2 - it was only acknowledgement that the AP had disconnected, and hence the PF has manual control. The CVR transcript shows the PF giving that call at 2:10.06 which is within 1s of the AP disconnect, so I do not believe that after this surprise event, he knew which mode he was in before he said that.

Approx 16s later the PNF announces "Alternate Law protections" but I've never seen any indications of acknowledgement from the PF, nor whether he really understood what that means about the available protections - which seems to fit with your second point above. However other things like cognitive overload were also well-argued in the past.

Machinbird

22nd Dec 2011, 16:34

I am afraid the PF's behaviour fits RR NDBs fourth category.I think we all need to be cautious in evaluating this crew's personal characteristics.

We have the advantage on them of knowing how their efforts turned out.
They were humans like us and did not intend to have their efforts turn out badly. We make mistakes, we have training issues, and poor performance issues. The same weaknesses applied to them. We are only in the early phases of learning what they were up against. Hopefully BEA will be able to put this whole puzzle together.

If we are to be critical, let us be critical of their performance, not their persons.
There is still a lot we do not know.

DozyWannabe

22nd Dec 2011, 17:17

How about this, then? A bigass Boeing:
[video of Korean Air 777]

"We ask you to please remain seated as Captain Kangaroo bounces us to the terminal."

Organfreak

22nd Dec 2011, 17:22

@DW:
LOL!!!

Bonin had a little more room to recover, it has to be said. :eek:

jcjeant

22nd Dec 2011, 22:54

As reminder (concern October 7 2008 incident A330 airbus type) the ATSB report released some days ago is available here:
http://www.atsb.gov.au/media/3532398/ao2008070.pdf
Seem's computers are the culprits
Incorrect data from a sensor measuring airspeed, altitude, air pressure, temperature and the flying angle was fed to the computers controlling the flight, investigators found.

RR_NDB

23rd Dec 2011, 00:21

Hi,

Incorrect data from a sensor measuring airspeed, altitude, air pressure, temperature and the flying angle was fed to the computers controlling the flight, investigators found. (http://www.pprune.org/tech-log/468394-af-447-thread-no-7-a-37.html#post6916662)

Garbage in, Garbage out...

PS

More and more we are dependent on complex Systems. A lot of skill is necessary to act timely and precisely when things go south.

PS2

From page 215 of the ATSB Safety Report:

It is very likely that...Despite extensive testing...the exact origins of the failure mode could not be determined.

Data spikes :}

Old Carthusian

23rd Dec 2011, 01:40

Machinbird
My apologies for the misunderstanding
My comment was not meant to attribute a judgement on the PF or other flight crew's personal characteristics but on the flight deck performance. For this I hold Air France culpable. Their policies and culture and lack of training set up this flight crew ill-equipped for the situation they faced and the poor individuals were out of their depth. I rather regard this as a tragedy for not only the passengers but for the flight crew as well. They too were let down.

Machinbird

23rd Dec 2011, 02:26

OC, No apology needed since you have clarified your intent.

I agree with your assessment of their training readiness for the events of that night.
They were not ready, that is plain.

If you will observe the roll PIO video that Organfreak posted. Once the initial overcontrol input was made, there was no way to promptly stop the oscillation. In fact what finally appears to have stopped the oscillation was likely intervention by the other crew member, probably by freezing the yoke in roll, but it is also possible that PF changed his strategy. It is hard to promptly undo this type of overcontrol mistake. That energy has to be dissipated.

I think something comparable happened on AF447. Those big spoilers popping up alternately are able to generate a lot of roll momentum quickly. But on the FBW 'Bus, PNF cannot freeze the stick, he must take the initiative and take control.

RR_NDB

23rd Dec 2011, 13:47

That energy has to be dissipated. (http://www.pprune.org/tech-log/468394-af-447-thread-no-7-a-37.html#post6916831)

An important reason to refrain from applying high amplitude stimuli.

Reading Learmonth ATSB report it comes to my mind a question:

Possible oscillation (MB), Possible Data Spike (difficult to trace as per ATSB), WRG fault (as per ACARS/Svarin emphasis), RHS not recorded (as per BEA), Persistent NU from PF (at RHS), "combined" may led to an unexplained (AF447) case in the end?

DozyWannabe

23rd Dec 2011, 14:40

In fact what finally appears to have stopped the oscillation was likely intervention by the other crew member, probably by freezing the yoke in roll, but it is also possible that PF changed his strategy.

Alternatively, the final touchdown resulted in a natural switch from lateral movements to pitch - keeping the nose down by pushing forward. I know I'm a critic of the "No pilot would ever..." statement, but the fact is that continung lateral input while pushing forward would be incredibly unnatural.

Organfreak

23rd Dec 2011, 15:33

I am told that what actually saved the landing was Ms. Bertha Pound, a purchaser of two tickets for herself, was standing to reach the overhead bin and suddenly fell down against the window, righting the aircraft.
:\

roulishollandais

23rd Dec 2011, 17:21

:rolleyes: Thank You MachinBird to come on the PIO .

I elaborated in 1992 a method to get out from a DUTCH ROLL, and demonstrated it five times ago, on a MD83 simulator (Finnair, Helsinki, dec 1992...).
Nobody understood how I did that (counting seconds precisly with my free-fall experience, and resolving two differential equations by head computing the "response" I had to fly, and did it with full success.
That is much more that what a pilot learns to fly. But a dutch roll who is not finished near of the ground is extremely dangerous, and I attribute some of the past crashes (I did not find them in the Aistotel data base) to this.
With my method it has been possible to get out the dutch roll, in less then 30 seconds, with loss of height less then thousand feet, it is then possible,falling in the dutch roll at the outer marker, to go around and come back safely. It is quite possible to do that without to have the mind overloaded with the new task. The captain who tried to come out the similar dutch roll, had 6000 hrs on the plane, and going on the back right and left, struggled and lost 11 000 FT to bring the wings level and stable .

The dutch roll is a severe PIO in MachinBird/Aristotel classification.

I agree totally with JCJEANT that without enough formation, the first thing is "HANDS UP". But a minimum training must be given to any professionnal pilot to be able to idendify the problem (is it a stall, a spin, a dutch roll, a deepstall, a lazy eight, a dynamic looping, aso.. Only next is it possible to learn a better method that « hands up » to correct the situation . This method does not concern a unexperienced pilot landing a C152 (Aristotel !).

I agree with MachinBird that it is not enough to "just fly", even for a very good pilot. Flying must be adapted to the dynamic situation. I already posted about the fact that dutch roll is not a problem of ge/speed, but of what doing what at which moment, how long, aso.

How does the dutch roll happen ? (I shall not explain here the total theory of coming out of a dutch roll, only main ideas). It is a frequency resonance (f2=n.f1 ; n=1,2,3,4,5,etc.) between the normal action of the pilot (is he volounteer if nobody learned him that ?!!!) and the natural roll stability of the aircraft.

a- Some aircrafts have this aerodynamic problem, the manufacturer has to correct, it comes sometime on little details.

b - The yaw damper can fail (leak of hydraulic liquid on the electronic box, modifying the electric characteristics, or mechanical failure inside the yaw damper) (failure or sabotage)

c - Modification of the aircraft characteristics due to bad, or insuffisant maintenance.

d - Modification of the aircraft characteristics due to bad flying, without respects of the speed limitation (for example >250 KTS under FL 100 for some aircrafts) repeated day after day...

e - Bad certification, without fully verification that ALL tests have been done, with positive proofs of acceptability for all them

f - To engage the p/a may be enough to start it too (classical or FBW aircraft), and disengage the p/a may be enough in a FBW aircraft. The use of the a/p On or OFF must be done ready to surprise.

g - For ANY AIRCRAFT, so stable he is, hard turbulence can start an oscillation, and the PILOT achives that catastrophic.

h - Last but not least, for ANY AIRCRAFT, ICING SUDDENLY, or ICE GOING AWAY SUDDENLY, may significantly modify the aerodynamic caracteristics and begin the furious mouvement with or without the help of the pilot !

After 1992 I tried to explain that to my pilot colleagues, but NOBODY in my french aeronautical community including administration of civil aviation wanted to listen anithing about that, rejecting strangely mathematics...
.
I wrote to the french BEA, and got no response
From 199 to 1998 nobody asked me how I had done, or to teach my method….and i turned my back , desesperating about flight safety.
In 1998, I got informed that a friend of Michel Baroin died in 1987 as passenger with him in his Learjet crash (not in the Aristotel data base). I had been his flight instructor and what I did read from the crash made me suspect a dutch roll finishing in a deepstall. I decided to start again to speak about coming out from dutch roll. I wrote a book… but found no editor .
Worse, I phoned with the Learjet Instructor in Genève (CH) ... and he explained that they (he ?) had found their own "method" to try to come out from the funest dutch roll : "Faire des cisaillements sur le palonier" (sic) (Quickly shearing pedals) !!!
This extremely wrong and dangerous "method" has been used by the copilot on the flight AA587 in the wake turbulence over the Queens : THE RUDDER BROKE (Nov 12. 2001).
The NTSB started after some time a public enquiry, and found terrifying facts, about flying, and maintenance of airliners and cracks in the fin. Some newspapers wrote about that, from New York and London : I traduced them from english to french, and the second times I showed them, I got death threats... Aerodynamic is really dangerous !

Reading the Aristotel document I am effraid to discover we are still not ready to see the end of the PIO or PAO : Why do they mix helicopter and fixed wing aircraft ? Equations are different ; solutions also. Beautiful categorisation from 1 to 8, but it is just a normalisation. Why do they mix pitch and roll PIO ? Solutions are different. Coming with the phase is a bad entry : without frequency resonance the phases will be different at the next cycle (and no PIO). Aristotel says the first element for an aircraft pilot coupling (APC) is a unfavorable vehicle dynamics : that is not true. A stable aircraft like A330 seems to be, in some specific environment may get in a APC. The « mental mismatch of the pilot » ? generaly the pilot flies same manner as he has learned to fly WELL, but this manner is not adapted to the situation. Finaly the close loop wood be for Aristotel the third key element : When we fly an aircraft we are always in a CLOSE LOOP. Pilots have to learn that and understand that. Aerobatics was much better to learn that, than 200 hours on C177RG or Trinidad ! Aristotel uses four categories of APCs : 1-2 linear and quasilinear ; 3.transitions in the aerodynamic configurations 4. Elastic structural modes or biodynamical couplings : But oscillation is not linear… Air is not elastic … And fly training is not a bioreaction but a Pavlov repetition ; stop with psychologising human factor : the main human factor in dynamic systems, is that a human is essentially a « time constant » !

As the AF447 fin was found by the Brezilian in one piece I already imagined the AF447 fin has broken (see my first pprune's post) like the AA587's one, and I am wainting due arguments from the BEA that it did not happened.

However I often looked BEA#3' DFDR graphs, and oscillations : I cannot find the dutch roll regularity, but that does not mean it was not : We still are unknowing the detailed Airbus software design (management of interruptions, time constants, damping coefficients, system architectur, size of piles, Bode diagrams, aso). (We also do not know the exact description of the flight laws : industrial secret ! We learned here that even AB simulators ,used to qualify the pilots, do not use flight laws but discrete description of the aircraft coming from test flights. But in our endless question about the crew conversation we find no word of wrong heading, despite it changed... It is impossible having 10, 100, 1000 or 10000 hours on the logbook to say not a word of this change . The BEA'silence, once more does us doubtus : Was is a pilot in the aircraft ? If the tail broked, due to a crak or misflying, with or without dutch roll, had they an explosive depressurization ? I was wondering too the oscillations in what seems to be an unstable deeptstall : strange, but possible if the fin has already started to fly away.

I am really very very very happy to read MB today ! Now we are doing aeronautics:D

grity

23rd Dec 2011, 18:01

roulis, It is a frequency resonance (f2=n.f1 ; n=1,2,3,4,5,etc.) between the normal action of the pilot (is he volounteer if nobody learned him that ?!!!) and the natural roll stability of the aircraft.what did you think is the frequency for the natural roll stability for a330 at this high and speed?

RR_NDB

23rd Dec 2011, 18:26

Now we are doing aeronautics (http://www.pprune.org/tech-log/468394-af-447-thread-no-7-a-37.html#post6917916)

A rich and long lived thread, highly motivating many of us.

Question: When (probably) VS separated? There are differences to the AA587 fractured VS as you did see in the released pictures.

When you have an insight* on something most are unprepared for, you pay the price. I "saw this movie" some times.

(*) I elaborated in 1992 a method to get out from a DUTCH ROLL, and demonstrated it five times ago, on a MD83 simulator (Finnair, Helsinki, dec 1992...).
Nobody understood how I did that (counting seconds precisly with my free-fall experience, and resolving two differential equations by head computing the "response" I had to fly, and did it with full success.

DozyWannabe

26th Dec 2011, 21:09

This extremely wrong and dangerous "method" has been used by the copilot on the flight AA587 in the wake turbulence over the Queens : THE RUDDER BROKE (Nov 12. 2001).

Not exactly - the vertical stabiliser separated inflight... *only* after being subjected to stresses beyond the Ultimate Design Load of the structure.

The NTSB started after some time a public enquiry, and found terrifying facts, about flying, and maintenance of airliners and cracks in the fin.

Neither cracks nor the repair to that A300's empennage had anything to do with the separation, which happened considerably beyond the Ultimate Design Load of the vertical stabiliser.

Using the rudder is not in and of itself dangerous, but rapid stop-to stop movement in a sideslip at high speed is, especially in an aircraft with wing-mounted engines and a large rudder to compensate. The problem with the AA case was that the First Officer was attempting a technique designed for the DC-9 series (small rudder, fuselage-mounted engines) on an A300 (large rudder, wing/pod-mounted engines). In the A320 sim using the rudder was better for ironing out the roll, but that was only performed after the speed had decayed past a certain point.

and the second times I showed them, I got death threats...

Forgive me for being a little sceptical, but from whom were these received?

Question: When (probably) VS separated? There are differences to the AA587 fractured VS as you did see in the released pictures.

On impact with the ocean surface. Unlike AA587, the AF447 vertical stabiliser had a large chunk of fuselage attached to it.

jcjeant

26th Dec 2011, 22:19

Neither cracks nor the repair to that A300's empennage had anything to do with the separation, which happened considerably beyond the Ultimate Design Load of the vertical stabiliser.Indeed .. These cracks are not (according to the report) a contributory factor
However the NTSB revealed by examination of other aircraft in the same series .. cracks that existed and had not been detected by maintenance services .. as their means of investigation were not suitable
It is clear that this finding by the NTSB and the development of new means of investigation has certainly allowed to prevent accidents from occurring in the future

This extremely wrong and dangerous "method" has been used by the copilot on the flight AA587 in the wake turbulence over the Queens : THE RUDDER BROKE (Nov 12. 2001).

Methink that the point of "roulishollandais" was about "wrong method" and this can be dangerous .. as it was show by the A300 case (obviously the pilot used the rudder control in a way that it has exceeded the certification of resistance of the materials concerned .. but if he had not used this method .. the accident would not have happen)

Unlike AA587, the AF447 vertical stabiliser had a large chunk of fuselage attached to itIndeed .. again ...
Nevertheless this does not prove that the vertical stabilizer separated from the plane in contact with water or when it was in flight
Other elements of the survey suggest a near certainty that the vertical stabilizer separated from the fuselage on impact

Machinbird

27th Dec 2011, 00:17

Dutch roll is a different oscillation than PIO is. Dutch roll is one of the natural oscillation modes of an aircraft in flight. PIO is an oscillation that results from a pilot's attempts to control an aircraft.

To help understand the difference, take a look at this Wiki post Dutch roll - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Dutch_roll), Then compare with the Aristotel definition. This is the reason Aristotel does not describe Dutch roll as a PIO characteristic, and why the Aristotel database does not have accidents listed that result solely from Dutch roll.

I've seen no evidence in the record that AF447 suffered from Dutch Roll. The A330 aircraft has an independent BYDU unit to provide yaw damping. Normally yaw damping alone is sufficient to prevent Dutch roll, although one jet I flew had "stability augmentation" on all 3 axes (and flew the same way a drunk walks when it was switched off.)

RetiredF4

27th Dec 2011, 09:48

Machinbird

I've seen no evidence in the record that AF447 suffered from Dutch Roll. The A330 aircraft has an independent BYDU unit to provide yaw damping. Normally yaw damping alone is sufficient to prevent Dutch roll, although one jet I flew had "stability augmentation" on all 3 axes (and flew the same way a drunk walks when it was switched off.)

I´m with you on all you wrote concerning PIO and it´s possible influence. I had my share of it once during airrefueling on a KC-135 in pitch dark night just prior contact flying from the backseat during instructor training.

And i can confirm your last sentence ......."and flew the same way a drunk walks when it was switched off" .......as we probably think about the very same aircraft.

Some reference to the Backup Yaw Damper Unit:

BACK UP YAW DAMPER UNIT
The Back up Yaw Damper Unit (BYDU) provides yaw damping in case of yaw
damper servo actuators deactivated, through an independant unit including its own electrical generation on Blue and/or Yellow hydraulic. It computes a yaw damping order similar to lateral alternate law (without turn coordination).

No "turn coordination" and hence no sideslip compensation most probably was contributing to the aparent problems in lateral control in the phase from AP dropout/ALT2 Law to stall entry and later on in the stalled situation. The FDR on Page 106 of BEA IR3 shows the graphs for Sideslip, and on page 112 it´s together with aileron input.

HazelNuts39

27th Dec 2011, 11:23

RetiredF4,
Would he really need turn coördination when he is not turning?

RetiredF4

27th Dec 2011, 12:54

The aircraft stays flyable without it, but that is not the question here.

The PF was used to it, we can assume that he never flew without it in a real aircraft. Any aileron input causes increasing drag on one wing hence sideslip, and any bankangle causes change of lift. It is a fine system that you don´t have to even think about those changes because the aircraft systems conmpensate for it on their own.

Without this compensation the lateral SS inputs causes sideslip and any bankangle change causes change of lift. That´s why you use some rudder and some nose up input on old aircraft without those systems when turning.

Therefore it should feel different to the normal everyday smooth riding especially with those big inputs made by the PF without autopilot and in roll direct (Alt 2).

We humans tend to feel uneasy with an input, if the desired result is not what we exspect. Look at car drivers on slippery roads, if unexpierienced they slam on the brakes if the car picks up a slight drift and agrevate the situation.

gums

27th Dec 2011, 16:37

yeah, Retired, Mach, Wolf, Smilin', et al.

I can't figure out how much aileron-rudder-interconnect (ARI) there is in the various "alternate" laws from looking at my skimpy 'bus manuals. Maybe Retired or A33 can enlighten us?

The Normal law appears to have not only a great ARI function for rolling into a turn, and also has an appropriate pitch input to make a level turn if stick pitch input is neutral.

Same question about the "damper" functions. I thot the 'bus retained the dampers regardless of mode, even "direct". This would resemble what we fighter pukes flew with since the 60's. And it definitely helped mitigate PIO's and other bad things.

Viper dampers NEVER cut out, but ARI cut out when one main gear WOW switch was compressed, hence no "wing low" landing, you landed in a crab. Otherwise, the rudder position that had been manually commanded for the slip went off the wall upon touchdown ( and we tested this for ourselves, heh heh). You don't need air data or inertial system data for the function, just some rate gyros embedded in the flight control computers via hardware/firmware or independent rate/gee sensors feeding the computer(s). In other words, we had no need to have a "basic" computer to filter and use all the external inputs, like the ADRIU the 'bus seems to rely upon.

I am not sure we saw but a glimpse of PIO with respect to the roll commands, so won't join that opinion. Same for inadvertant pitch inputs, as looks like they were intentional because "the aircraft won't let you stall" mentality.

DozyWannabe

27th Dec 2011, 18:01

Nevertheless this does not prove that the vertical stabilizer separated from the plane in contact with water or when it was in flight
Other elements of the survey suggest a near certainty that the vertical stabilizer separated from the fuselage on impact

Absolutely - maybe I should have clarified by prefixing "among other things", chief among which is the fact that the flight path is consistent in every simulation the BEA has run with the vertical stabiliser remaining attached until impact and final breakup.

But sometimes it's more fun to make the "weak tail" conspiracy buffs go and spend a few hours trawling Google Images to understand for themselves... :)

Machinbird

27th Dec 2011, 20:33

Perhaps it is slightly more complicated. The drag due to downward deflection of the aileron on one wing is largely compensated by the drag of the spoilers extending on the other wing, and the yaw damper is still active.
And it is still probably more complicated than that with rapid reversing control inputs. If the response time of ailerons and spoilers are not perfectly matched while transitioning, you might be off the planned schedule and creating additional yaw.

Normally, with a brief interval of mismatch, this is no big deal. However, when the controls are continually transitioning as in the case of a roll PIO, the percentage of time that this potential imbalance applies is greater and may be the source of yaw inputs to the airframe.

Having flown jet aircraft with aileron only roll control, spoiler only roll control, and combination aileron spoiler-aileron roll control, I prefer the combination approach, but spoilers can create cruise inefficiency with a heavy wing. For that reason, spoilers often only move with larger roll inputs, and smaller inputs are handled with the ailerons only. I do not know how the A330 gears the relationship between ailerons and spoilers.

roulishollandais

28th Dec 2011, 16:29

I don't forget you. ... Christmas !!

A33Zab

28th Dec 2011, 20:50

Here some 'food for thought' considering Yaw alternate law and dutch roll dampening, extracted from AMM.

AMM 27-90 - ELECTRICAL FLIGHT CONTROL SYSTEM (EFCS)

(1) Normal configuration
----
----

(2) Reconfigurations
(a) Laws and associated functions
1 If the normal control laws are lost:
When the conditions required for keeping the normal control laws are no longer fulfilled, the control laws are reconfigured.
The various degraded law states that are possible are (in flight or upon flare):
// Roll and yaw:
Yaw alternate law
// Pitch:
Nz law (with limited pitch rate and gains)
Vc PROT law (ALPHA 2)
VMO2 law
Pitch direct law

The "Alternate" laws are engaged when the protections related
to the normal laws (ALPHA 1, VM01) are lost.
The "Direct" laws are engaged when the Nz law is lost.

The associated functions available are :
----
----
sideslip estimation (except in alternate 2 law or direct law)
if yaw alternate law, sideslip estimation is changed in Ny body lateral accelerometer.
----
----
2 Yaw alternate law

This FCPC and FCSC law is engaged if the lateral normal law is lost.
Its characteristics are:
- The roll control is direct, an order on the side stick directly commands a deflection, according to a kinematic calculation.
- The yaw control is achieved by the summation of two terms:
. pedal orders
. Dutch roll damping orders (from yaw rate)
In the event of loss of the inertial data from the ADIRUs, the yaw rate data for Dutch roll damping is provided to the FCPC via the rate gyro unit.
If the three FCPCs are lost, the FCSC1 ensures Dutch roll damping, using yaw rate data from the rate gyro unit.

(6) Turbulence Damping Function

(a) General
The purpose of the Turbulence Damping Function implemented in the Electrical Flight Control System is to damp the structural modes induced by atmospheric turbulence.

(b) Architecture
The Turbulence Damping Function consists of two lanes:
1 Longitudinal lane
The longitudinal Turbulence Damping command is computed by the FCPC1 (FCPC2 as a redundancy) as a function of the Nz accelerometer information.
It is added to the normal law command and transmitted to the associated elevator servo-controls.
2 Rear lateral lane
The rear lateral Turbulence Damping command is computed by the FCPC1 (FCPC2 and FCPC3 as a redundancy) as a function of the information of a specific Ny accelerometer located at the rear bulkhead level.
It is added to the normal law command and transmitted to the associated rudder servocontrols.
(c) Specific equipment
- the TURB. DAMP pushbutton switch
- the Ny rear accelerometer.
----
----
(11) Sideslip estimation and Beta target computation

(a) Sideslip estimation
This function is elaborated in the FCPCs in the flight and flare phases. The estimated sideslip is used as an input parameter for the lateral normal law. It is fed to the FMGECs and sent to the DMCs by the FCDCs for display on the PFD.
~o~

Here's a simplified schematic for the 'mechanical' rudder:

http://i474.photobucket.com/albums/rr101/Zab999/A330_MRudder.jpg

roulishollandais

16th Jan 2012, 20:55

Happy new Year to Everybody !

Thank You A33Zab !
Could we have a look inside S1, S2, P1, P3 ? :mad: ?

roulishollandais

16th Jan 2012, 21:31

Is still anybody here ???

@A33Zab
Please, Do You have the answer to Grity's question (AF447 THREAD 7 post #730)

"what did you think is the frequency for the natural roll stability for a330 at this high and speed? "

In my own experience the frequency of the resonance was around 0.4 hz

@MachinBird
The Dutch roll is of much interest : equations have the lowest degree ! That means too that no additional energy is put in the closed loop (very very important).
For any other oscillations, you need to enlower this degree ! Otherwise you have not only inflexion points but inversion points in the response, and that cannot be managed by the pilot in flight.

A33Zab

17th Jan 2012, 01:15

Could we have a look inside S1, S2, P1, P3

I guess a lot of electronic components gathered closely together....

We know what is going in and what is coming out. (FDR traces in--> Yaw damp order + pedal order
and out --> Rudder position --> Yaw rate = Yaw damp order....

If the lateral accel. trace is coming from ADIRU(below cockpit floor) the trace of Ny accelerometers
is missing (Ny accelerometers located aft of bulkhead).

AMM text:
"if yaw alternate law, sideslip estimation is changed in Ny body lateral accelerometer."

If this is the trace shown on the lateral parameter page it doesn't look very well....(after alternate law is engaged)

AMM text:
The estimated sideslip is used as an input parameter for the lateral normal law

Not mentioned, if the estimated slideslip is also a input during alternate operation or only used for display on PFD?

roulishollandais

4th Feb 2012, 16:41

roulishollandais:
Quote:
inside S1, S2, P1, P3
A33Zab :
Quote:

We know what is going in and what is coming out.

Sure :ugh: but I want to know the algorithms :suspect: and logic circuits :suspect: who are used, and time period of sampling :suspect: , not only input and output ! I want to see INSIDE :ok:

ChristiaanJ

4th Feb 2012, 19:59

You want to look inside? Here you are...

http://img.photobucket.com/albums/v324/ChristiaanJ/11280007w-1.jpg

What you really want is ...
- a full CMM (component maintenance manual),
- a full system block diagram,
- enough system engineering knowledge to interpret the above.....

PS..... OK, that's a Concorde AFCS circuit board.
In those days, the "algoritms" were 'frozen' in op-amps, resistors and capacitors, and the logic was hard-wired using TTL and DTµL logic circuits.

The above photo is an analog control law computing board.

Here's where the logic is being dealt with...

http://img.photobucket.com/albums/v324/ChristiaanJ/12260001w.jpg

roulishollandais

7th Feb 2012, 21:05

Thank you very much ChristiaanJ ; this Concorde AFCS circuit board (analog control law computing board) is very beautiful; like the Concorde is ! How beautiful it was in the sky ! :D

effectively what I still want is ...
- a full CMM (component maintenance manual),
- a full system block diagram,

Despite digital systems overcame on analog system, I am sure that the latter are the best to modelize and control non-linear unstable circuits.
Digitalizing brings many problems at the same time it seemed anything became easy by linearisation, and matrix computing.

Future is ahead ! ;)

A33Zab

8th Feb 2012, 20:50

effectively what I still want is ...
- a full CMM (component maintenance manual),
- a full system block diagram

For sure a CMM will not supply you with the requested information.

http://i474.photobucket.com/albums/rr101/Zab999/FCSCInternals.jpg

For test and fail isolation the computer will be connected to an
ATEC Series 6 (http://www.eads-ts.com/web/brochures/ATEC6.pdf) testbench.

The computer is a modular construction like any modern black box, if a card failed the card is replaced not the failed component on the card itself.

For obvious reasons (e.g. Intellectual property, trade secret, terrorism) a full logical diagram is hidden for the public,
but PJ2 posted a pitch channel logic for A320 a while ago:

http://www.smugmug.com/photos/i-RvKWdbv/0/XL/i-RvKWdbv-XL.jpg

FWIW you will not find beancounters in flight operations only, they are well spread over the world and also in the MRO business.
The suppliers of such sophisticated equipment are negotiating - aircraft life term - maintenance contracts (starting with B787)
for their equipment so all technology remain within the vendors company itself.

ChristiaanJ

9th Feb 2012, 20:32

For sure a CMM will not supply you with the requested information.If so, CMMs have changed from "my days".
A CMM would provide me with block diagrams, circuit diagrams, circuit board layouts, and yes, pictures like the one you showed, to correlate circuit board references and their physical location in the computer.
But it would also provide me with a full test specification.

For test and fail isolation the computer will be connected to an
ATEC Series 6 (http://www.eads-ts.com/web/brochures/ATEC6.pdf) testbench.
I'm afraid you're confusing matters.
The ATEC is an automatic test system that runs an automatic test prgram.
That program does not just appear 'ex nihilo'... it is written on the basis of the original test specification, which can equally well be executed on a manual test bench or a different automatic test system (been there, done that, written ATEC programs....).

The computer is a modular construction like any modern black box, if a card failed the card is replaced not the failed component on the card itself.That of course depends on what level maintenance you're talking about. But for first/second-line maintenance I agree.

For obvious reasons (e.g. Intellectual property, trade secret, terrorism) a full logical diagram is hidden for the public,Depends on what you call "the public". In an avionics workshop, I would expect to have access to this kind of information.
....but PJ2 posted a pitch channel logic for A320 a while ago...Terminology has obviously gone out of the window since "my days". That's not a 'logic' block diagram, but a 'functional' diagram.... and near-useless (except as an intro) to anybody called to maintain the system.