AF447 wreckage found

[bearfoil]

Lonewolf

Many thanks. And also to infrequentflyer789.

So, PF holds back stick over three minutes. He's mad, or he thinks it's "appropriate"? He's not mad, so does he believe that his a/s and v/s (!) is a descent, (It actually is), and his SS back is going eventually to pull them out of the "Dive"? Of course, the panel (LHS) and ISIS have already told their story to BEA.

"We are going to go through 10". Just a wild guess, but is this comment laden with an opinion that they will recover, and it will be quite low when they do? To me, it means just that, it does not mean "And then we will impact the Ocean." I think he expects the ship to level off. That explains the back stick. This means that logically, there would not be a STALL WRN on the way down. Will we find out if there was?

Before autopilot, and for a time after, there was the "wing leveler". I just think that in any condition, a sharp change to manual flight puts the Pilot in a far deeper hole than an a/p w/o ASI. W/O ASI, an auto pilot can hold altitude (accelerometers), and PITCH (Same). The pilot has no such advantage, with bunk data and PNF holding a book.

[BOAC]

As current contributors will probably know, I am one of the 'old' aviators, but I still find it incredible that these two pilots performed the initial climb. I am less interested in investigation of the 'after the climb' events since I judge these to be incorrect handling for whatever reason, be it training, AB 'philosophy' or just lack of recognition of the stall.

Moving on to Bear's 'pitch/power' AP mode - a good idea, but again you need reams of code with all the pitfalls they bring, to cover all the oddballs that can be thrown. Which attitude to use? How will discrepancies be voted out? Was it IAS or attitude - or something else - that triggered the drop to Bear's system? How will the AP cope if the IAS is actually too close to stall/Mcrit while it flies the correct attitude/power? Will it be capable of recovering from an upset?

No, I still back my call (elsewhere) for properly trained and capable pilots who have the innate ability to sift the wheat from the chaff and an FCS that they can understand and use . In my opinion, 'automation' has still way to go.

[mm43]

Bear

Your Pitch 'n' Power mode is what the AP does all the time for its bread and butter. There are of course a few environmental inputs that it needs to effect this operation in a closed loop manner, e.g. barometric alt, OAT, and CAS amongst others.

How about looking again at a proposed method of replacing the CAS short term when UAS becomes an issue as described in AF447 Thread No.4 page 31. The advantage of that proposed method is the AP software operates as per normal and the missing CAS is calculated using all the other parameters that are already known.

This is not meant to be a panacea for all the ills that the PF may be confronted with, e.g. the nose-down right-hand roll. Though in this case if the pseudo CAS was injected seamlessly the AP would have carried on correcting for that perceived external force.

Meanwhile, I'm still contemplating the dynamics of "bubbles" being blown by a grandchild in the bath.

[bearfoil]

The a/p has its command to provide a particular altitude, airspeed. At the core of this command is PITCH and POWER, yep. I'd be surprised if at disconnect, it lost its recent tracking artifacts. The Pilot is not charged with keeping a three second loop of "last recorded" in his head, as the a/p keeps without a sweat. Frustrating, esteemed Pilots suggest at the beginning to be patient, when all we need is a snapshot of the previous chain of acceptable status points, a normed value and a command, "get us 'here'. A million frames of accelerations? Yes, with random points of data geography such that continued flight can be kept in limits for 5-10 minutes? 5-10 hours? Why not?

[wallybird7]

Real deviation

SaturnV

"wallybird7, you are suggesting that they deliberately flew into a defined thunderstorm? Defined by who? and when?"

What I am saying is that they did not deviate far enough away from the line of thunderstorms.

No one knows for sure the dynamics of any particular thunderstorm except that they can contain severe turulence and up and down drafts and most likely had something to do with loss of pitots and possibly control.

A deviation around the line might add 15 minutes of time and fuel, and if so, my opinion is we wouldn't even be discussing AF447.

[wallybird7]

DO'S AND DON'TS OF THUNDERSTORM FLYING

Above all, remember this: never regard any thunderstorm as “light” even when radar observers report the echoes are of light intensity. Avoiding thunderstorms is the best policy. Following are some Do's and Don'ts of thunderstorm avoidance:

1. Don't land or take off in the face of an approaching thunderstorm. A sudden wind shift or low level turbulence could cause loss of control.
2. Don't attempt to fly under a thunderstorm even if you can see through to the other side. Turbulence under the storm could be disastrous.
3. Don't try to circumnavigate thunderstorms covering 6/10 of an area or more either visually or by airborne radar.
4. Don't fly without airborne radar into a cloud mass containing scattered embedded thunderstorms. Scattered thunderstorms not embedded usually can be visually circumnavigated.</I>
5. Do avoid by at least 20 miles any thunderstorm identified as severe or giving an intense radar echo. This is especially true under the anvil of a large cumulonimbus.
6. Do clear the top of a known or suspected severe thunderstorm by at least 1,000 feet altitude for each 10 knots of wind speed at the cloud top. This would exceed the altitude capability of most aircraft.
7. Do remember that vivid and frequent lightning indicates a severe thunderstorm.
8. Do regard as severe any thunderstorm with tops 35,000 feet or higher whether the top is visually sighted or determined by radar.

If you cannot avoid penetrating a thunderstorm, following are some Do's Before entering the storm:

1. Tighten your safety belt, put on your shoulder harness if you have one, and secure all loose objects.
2. Plan your course to take you through the storm in a minimum time and hold it.
3. To avoid the most critical icing, establish a penetration altitude below the freezing level or above the level of —15° C.
4. Turn on pitot heat and carburetor or jet inlet heat. Icing can be rapid at any altitude and cause almost instantaneous power failure or loss of airspeed indication.
5. Establish power settings for reduced turbulence penetration airspeed recommended in your aircraft manual. Reduced airspeed lessens the structural stresses on the aircraft.
6. Turn up cockpit lights to highest intensity to lessen danger of temporary blindness from lightning.
7. If using automatic pilot, disengage altitude hold mode and speed hold mode. The automatic altitude and speed controls will increase maneuvers of the aircraft thus increasing structural stresses.
8. If using airborne radar, tilt your antenna up and down occasionally. Tilting it up may detect a hail shaft that will reach a point on your course by the time you do. Tilting it down may detect a growing thunderstorm cell that may reach your altitude.

Following are some Do's and Don'ts During thunderstorm penetration:

1. Do keep your eyes on your instruments. Looking outside the cockpit can increase danger of temporary blindness from lightning.
2. Don't change power settings; maintain settings for reduced airspeed.
3. Do maintain a constant attitude; let the aircraft “ride the waves.” Maneuvers in trying to maintain constant altitude increase stresses on the aircraft.
4. Don't turn back once you are in the thunderstorm. A straight course through the storm most likely will get you out of the hazards most quickly. In addition, turning maneuvers increase stresses on the aircraft.

Table of Contents
Previous Section: Thunderstorms and Radar
Next Section: Common IFR Producers

SOURCE: FAA AVIATION WEATHER THUNDERSTORM FLYING

Note: The FAA signs off on my certificate. This is also my Company Policy.

It does not mean failure to comply equals certain death. But it does suggest risk is involved. Paying passengers do not want any risk!

[Turbine D]

wallybird7,

Your post on thunderstorm penetration/avoidance was an interesting read. However, in the ITCZ, very nearly all the storms are not thunderstorms. The storms are tropical storms that do not contain lightning and therefore, no thunder. At night visually, with no light from the moon, one would not know they were there. The clue to their presence would be the radar and how it maybe being monitored and used.

It would be my guess and it is strictly a guess, they were late in using their radar to interpret what lay ahead. But with some other clues, they began to, "Can you move a little to the left?" If the static satellite overlay in a couple of previous posts is correct and I think it is as close as we will see, they did recognize the CB buildups (rather late) and were trying to shoot the gap between two. IMHO, what then caused the problem was the pitot situation leading to AP/AT disconnect.

As I recall the LH track before it was taken down, LH did not completely go around either, but shot a gap between two CB buildups a little further to the West. They did however, start their turn Westward earlier.

Just some thoughts.

[bubbers44]

The 12 degree deviation left in their opinion was adequate for the weather they were penetrating. If they had deviated either direction 30 degrees the outcome would have been the same. When their pitot tubes froze up they lost control of the airplane. They didn't have the ability to fly that airplane with UAS with their experience. Soon the final report will come out and we can confirm that but right now speculation of what happened is all we have. The pitching over 15 degrees up with a loss of airspeed indication says a lot.
So far that is all we know they lost. Maybe a few bumps.

[RWA]

"Why the zoom?"

I agree that that's a key question, poit. The BEA's report is pre-occupied with 'noseup inputs' on the part of the PF, but even the report credits the PF with a correct response to the 'zoom':-

"The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb. The PF made nose-down control inputs and alternately left and right roll inputs. The vertical speed, which had reached 7,000 ft/min, dropped to 700 ft/min and the roll varied between 12 degrees right and 10 degrees left."

That was the first phase of the upset. The next phase started with the stall warning sounding. The PF appears to have responded with the correct drill at the time - 'TO/GA power and seek to maintain altitude':-

"At 2 h 10 min 51, the stall warning was triggered again. The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs. The recorded angle of attack, of around 6 degrees at the triggering of the stall warning, continued to increase. The trimmable horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight."

This was the crucial 'second phase.' Whether this was the result of TO/GA power pushing the nose up, the PF's inputs, the THS going to 'full up,' or the thin air at 38,000 feet, or whatever, we don't know; my own feeling is that it was probably the result of a combination of all those factors. In any event, the aeroplane appears to have 'sat on its tail' and entered a deep stall.

We don't know what instruments the pilots had available at that time. However, I suspect that they were at first pre-occupied with the rapid loss of altitude, and formed the view that the aeroplane was in a dive rather than a stall. After all, the stall warning had stopped, that may have given them the impression that they had successfully 'avoided' any stall. It annoys me that the BEA probably KNOWS, from the CVR, what the pilots reckoned 3was goingon (unless they descended over 20,000 feet without saying anything at all to each other?).

There was in fact a third phase. In that connection I next have to mention a 'leak' published early on by 'Der Spiegel'; not the most reliable source, obviously, but it has never been denied:-

"The BEA report, in its current form, only provides the angle of the stabilizer but provides no explanation as to why. The report merely indicates that it was at this moment that Captain Marc Dubois re-entered the cockpit.

"Exactly what orders he issued are not part of last Friday’s report. But sources close to the investigation are saying that he said: “This is a stall. Reduce power and nose down!”

Spiegel: Questions Raised about Airbus Automated Control System | Airlineberg.com

Indeed, a changed (and more correct) approach is indeed referred to in the BEA report, while the aeroplane still had over 10,000 feet in hand:-

"At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have no valid indications". At that moment, the thrust levers were in the IDLE detent and the engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again."

However, as we all know, the aeroplane never recovered from the deep stall. In this connection I have to quote the BEA again; saying that, even though the PF duly (even if belatedly) applied 'nosedown inputs,' "the THS remained in the latter position until the end of the flight." That is, remained at 13 degrees up.....

I'm afraid that that opens up the possibility that the THS didn't just go to 13 degrees up; but that, like the THS on that Alaskan Airlines MD80, it then jammed there?

[iceman50]

RWA

Give up would you. You just keep spouting the same old rubbish which has been pointed out to you many times.

The PF appears to have responded with the correct drill at the time - 'TO/GA power and seek to maintain altitude':-

That is complete rubbish stall recovery is NEVER maintain altitude!!!!! and the low speed recovery was NEVER maintain altitude either!!!!

Read the BEA report and try to understand it the THS went to the nose up position because the PF demanded it! It then stayed there because autotrim was then disabled and all they had to do was use the trim wheel to reset the THS and it would have been annunciated on the PFD.

[Zorin_75]

It then stayed there because autotrim was then disabled

From my understanding they never left alternate law so autotrim was active all the way?

[RWA]

Quoting iceman50:-

That is complete rubbish stall recovery is NEVER maintain altitude!!!!! and the low speed recovery was NEVER maintain altitude either!!!!

So this and other articles about 'revised procedures' since AF447 and other incidents are all just wrong?

"Investigators have been left attempting to explain why the crew of Air France flight AF447 failed to recover the Airbus A330 from a high-altitude stall, a predicament which has been the subject of a recent revision of safety procedures.

"The revision concentrates on placing greater emphasis on reducing excessive angle of attack - the critical characteristic of a stall - rather than the classical approach of training pilots to power their way out of a near-stall with minimum loss of altitude.

----------------

"The revised recovery procedure was agreed between the major airframers, including Airbus and Boeing, some 12 months after the loss of AF447, although a source familiar with the investigation stresses that the change was "not prompted" by the accident.

"At the heart of the revision is an acceptance that classical high-power recovery is not appropriate for every stall condition.

"Simply applying maximum thrust could be ineffective in reducing the angle of attack and averting a stall, particularly at cruise altitudes where the available thrust would be limited and the engines would require time to spool up.

"There is also a risk that the crew might fail to recognise that the aircraft has crossed the threshold from a near-stall into an actual stall, and continue to apply a recovery technique which is no longer effective.

The new procedure is designed to cover all stall conditions. It recognises that recovering the angle of attack might instead require a reduction of thrust, to regain pitch-down authority, as well as a loss of altitude."

http://www.flightglobal.com/articles/2011/05/28/357321/revised-stall-procedures-centre-on-angle-of-attack-not.html

I guess we were all taught 'stall recovery' when we first learned to fly. In daylight, at a reasonable altitude, with plenty of warning, a visible horizon, etc.? And that the very first thing we were told to do was to get the nose down? But I guess that it simply isn't possible to let trainee airline pilots stall an actual transport category aircraft - so it all has to be done on simulators only.

My impression is that such pilots are in fact taught only 'stall avoidance,' not actual 'stall recovery.' And that it is therefore entirely possible that the unfortunate AF447 pilot heard the stall warning and carried out the 'avoidance' procedure prescribed at the time. But that, further - given that the stall warnings stopped (even though that was, in all probability, only because the airspeed had dropped almost to nothing) - the pilot assumed for quite a while that his 'avoidance manouevre' had been successful?

[BOAC]

wallybird - I would ask you to carefully read both the current and old threads on this topic? Your fixation on 'thunderstorms' is out of place based on what we are told by BEA. There is also no firm 'evidence' of any 'thunderstorms' on their route.

There is no evidence that they 'penetrated' or flew near a 'thunderstorm'.

It is shown (in the reports) that their 'choice' to deviate to the west proved to be a better one than other aircraft which went to the east.

We do need more from BEA (hopefully 'at the end of the month') to tell us what radio calls and conversations actually took place on the flight deck. We just do not know enough at the moment.

[bubbers44]

stall recovery in the 60's lower nose and max power
same for 70's 80's until the 90's.
Then you had to use max power and not lose more than 50 ft for some reason. Secondary stalls became a problem then. Guess things haven't changed much since the 90's.

[sebaska]

@RWA:

The next phase started with the stall warning sounding. The PF appears to have responded with the correct drill at the time - 'TO/GA power and seek to maintain altitude

Nope. The drill for UAS was TOGA and 5deg nose up. At that moment (as per BEA) the plane was already 6deg nose up. So making persistent (for over minute as per BEA) nose up inputs to get attitide from (initial) 6 deg up down to 5 deg up is not certainly proper drill. The craft was still climbing (at 700fpm from 37500 to 38000) so maintain altidude does not seem yet to be an issue (or it'd rather dictate nose down).

The reason for nose up inputs (inputs, not surfaces position, but pilot inputs at the stick) remains unxeplained as for now.

This was the crucial 'second phase.' Whether this was the result of TO/GA power pushing the nose up, the PF's inputs, the THS going to 'full up,' or the thin air at 38,000 feet, or whatever, we don't know; my own feeling is that it was probably the result of a combination of all those factors. In any event, the aeroplane appears to have 'sat on its tail' and entered a deep stall.

Coffin corner has been calculated for that plane by one of the experienced posters here. It was determined to be 46000ft. Even if the air was somewhat warmer (as crew discussions as disclosed by BEA indicate) it was rather no worse than 43000ft -- still 5000ft above 38000ft achieved by the plane. And the fact is that the plane was slowed down to Mach 0.68 before stall warning came -- so there was a margin from 0.68 to somewhere around 0.85 -- hardly a corner.

iceman50:

Read the BEA report and try to understand it the THS went to the nose up position because the PF demanded it!

Exactly. It's stated explicitly. All the discussion about the reasons of trim going fully nose up is inventing (non)facts to fit someone's pet theories.

It then stayed there because autotrim was then disabled and all they had to do was use the trim wheel to reset the THS and it would have been annunciated on the PFD.

It seems more probable that there was no mode change to Abnormal attitude. Most probably because IAS below 60kts caused AoA readings to be treated as unreliable and thus disregarded by mode change logic. At the same time to get that (auto)trim down by the use of stick it'd require consistent nose down inputs lasting for time long enough to equalize previous nose up action. "Nose-neutral" inputs won't change (auto)trim, as someone few tens of pages back noticed.

BTW. Wrt AoA relaibility at slow speeds. There was recently thread about rejected takeoff above V1 incidedent and investigation body's take on in. One interesting tidbit pertaining to our discussion is AoA plot from FDR from that plane as presented in the report. As speed of the plane decreased below ~45-50kts measured AoA started to deviate and at ~40kts in went completely wild (like 60 or even 90deg). That plane was on the ground so it's real AoA remained allmost constant.

[iceman50]

RWA

The problem is you keep misinterpreting the information. Maintaining ALTITUDE was NEVER required.

Zorin_75

If you read the report the AOA increased beyond the threshold for Abnormal Attitude Law to come into force, so Autotrim would not be available.

[BOAC]

BEA said abnormal law did not trigger.

See 'Flight Global'

Abnormal law could only have been triggered by an inertial upset, such as a 50° pitch-up or bank angle of more than 125°. "That never occurred," says French accident investigation agency Bureau d'Enquetes et d'Analyses.

[Lonewolf_50]

@funfly:

As an SEP can I please ask you very experienced pilots a question?
If you are flying an (any) aircraft with no outside vis. and suspect instruments and your body and altimeter gave every indication that you were hurtling downwards at a high ft/sec. would it not be a 'normal' reaction to pull back on the stick irrespective of any flight instrumentation. Could this therefore be a case where old fashioned 'seat of pants' reactions were the wrong ones and less 'flying' training and more 'flight' training might, in this case, have yielded a better outcome.

What do you mean by "suspect instruments" in this case?

The primary scan instrument is your attitude indicator/artificial horizon. Unless the BEA find something new in their analysis, we are absent evidence of a failed attitude indication.

If I am flying IFR and my artificial horizon has tumbled or failed, I then have to use a partial panel scan (are my turn and slip working? Is my VSI working? Is my altimeter working?) If no to those questions, I am screwed mightily.

But if they are, I work my butt off via my partial panel scan to cross check to get back to straight and level. Recall: the A330 has three laser ring gyros, also called Inertial Reference Units. These feed the attitude indicators. (there is also a back up gyro on the ISIS display cluster).

All else considered, one thing I have to fight like hell is to overcome any feeling of seat of the pants, since in IMC it can give me the leans and kill me via the classic death spiral. (See JFK Junior for a tragic example of that ...)

To say it again, with feeling: if I am flying without visual reference to the horizon (on instruments), then seat of the pants sensations can fool me.

I have to, I must, use a disciplined instrument scan to ensure safe flying.

I am pretty sure that you will hear the same from every CFII you ever meet. I'd be stunned if you don't.

[Graybeard]

AOA

SEB: . .

Wrt AoA relaibility at slow speeds. There was recently thread about rejected takeoff above V1 incidedent and investigation body's take on in. One interesting tidbit pertaining to our discussion is AoA plot from FDR from that plane as presented in the report. As speed of the plane decreased below ~45-50kts measured AoA started to deviate and at ~40kts in went completely wild (like 60 or even 90deg). That plane was on the ground so it's real AoA remained allmost constant.

447 could not have very low speed for very long. It was either moving forward, or dropping fast enough to keep the AOA vanes pointed into the relative wind.

It still puzzles me why the 330 uses airspeed input to the stall warning. McDouglas airplanes don't.

[RWA]

Quoting sebaska quoting iceman50:

"Read the BEA report and try to understand it the THS went to the nose up position because the PF demanded it!"

Exactly. It's stated explicitly.

Please - either of you - please provide a reference to the part of the BEA report you're referring to? I've read it thoroughly, several times, and if it says anything like that I must have missed it?