PJ2

hi gums;
Yes, the gang's all here, but only momentarily!Yes, I understand that, we've discussed that and I even had posted a schematic showing how AoA can be roughly approximated (while not precisely and not instantly due to lag but perhaps usefully if one is trained / skilled at such interpretation*) from the FPM / FPV and pitch angle, independent of the AoA sensors.

"Derived" in flight data work means usefully accurate and precise as well as timely and the FPM / FPV vs pitch method of "deriving AoA" in rapidly changing circumstances, is none of these.

While the FPM/FPV display is inertially-driven this still requires a working ADR (AF447s were intermittent and, in the time period available, essentially unusable) and a working AoA sensor (Perpignan, frozen sensor, erroneous stall speed display on the PFD).

The point I wished to make in regard to Lyman's statement that AoA can be derived is that it can't be in the sense that it could be used to display AoA when original sources as described, are not available.

*When the A320 first came online, we were trained that the FPV Flight Director should not be used as guidance during a go-around because of the lag in the FPV as the aircraft stops descent and begins the climb. The justification was, following a lagging display could lead to reduced climb performance. I believe that's now changed and the normal FDs are displayed automatically when the thrust levers are pushed to the TO/GA detent.

PJ2

Of possible interest is the UAS table below from the A320, dated April, 1991. The table clearly provides pitch and power settings for all regimes of flight. This checklist is in contrast with what I think was and is a confusing UAS memorized drill & checklist combo. While the origins of the present mess of a drill / checklist are understandable (post Birgenair & Aeroperu), compared to this simple checklist which provides clear information on pitch/power settings for all flight regimes, the present drill remains open to interpretation as to when the safety of the flight is at risk. The present drill also requires a pitch change in cruise altitude when none is required.

While pulling a transport aircraft up to 10deg pitch while in cruise is a serious error, I think the memorized drill, if taught incorrectly or misunderstood (and it still isn't clear) can leave some pilots who may not get into the books very much, (as per DP Davies' thoughts posted earlier on 'working at the career' and learning) or otherwise just thinking about the drill and maybe asking questions, with the impression that "pulling up" somehow solves the 'problem'. Granted a 5deg pitch up at FL350 won't lead to stalling the airplane, but why destabilize the airplane in the first place?

Chris Scott

Hi gums,

Quote from gums #829:
"In wings level flight, AoA can be derived from the pitch and the inertial velocity vector regardless of the air data probes/cones. The Sluf and Viper HUD had a "zero sight line" cross, and usually the flight path marker ( FPM) was below it ( negative gees was something else, heh heh). That was your AoA in wings level flight."

Three years ago (before you joined this discussion?), some of the "gang" chewed over this subject, and we gradually realised that - for various reasons - it wasn't as simple as we had hoped...

http://www.pprune.org/tech-log/39510...ml#post5575204

Mac the Knife

Wouldn't their Attitude Indicator showing a lot of blue sky given them a clue?

Just asking!

Lonewolf_50

Presuming the AI was integrated into a working instrument scan, yes.

Lyman

PJ2

Howdy....From Chris Scott, post #521, "Search to Resume"

This is what I had in mind, and I recall the flightcrew doing some things in the cockpit that put me in mind of wanting the "Bird"...... for AoA? Dunno...

So sorry to get gums in the soup....took some looking.

PJ2

Hi Lyman;

Yes, that's what I'd figured was in mind as I know AoA can't be derived from any other flight or system parameters.

I do think that someone "tuned in" to his/her airplane could make use of this information so in that sense it's another tool, subtle and not widely nor well-understood even in the instructing world, (in fact I know an airline that refused to authorize use of the FPV/FD and would not train or permit its use in operations).

I think had they had the FPV they would have seen this, (quickly...time yourselves... 3, 5, 10 seconds with noise, buffeting, warnings and fright, what's the AoA? What angle are we going down at? Should I pull or push?):

bubbers44

2 degrees nose up attitude and cruise power would have made this accident a non event. Hopefully pilots will now not make the same m
istake they did.

Lyman

Once I jump, I PULL, the ripcord.....20000fpm descent, AoA +45, Pitch 8 ND.

Nope that's wrong, badly..... seven seconds. Adios.

Is this our friends?

gums

TNX Chris and PJ for getting me back to Earth.

I realize that we had the AoA discussion way back before I started to comment, but I had read the threads with only one comment until after we saw the wreckage pattern and got into control laws and a deeply stall jet.

As several had pointed out, a derived AoA might be possible but impractible, and prolly unuseable if the pilot wasn't used to using AoA on a dail basis as Mach did coming aboard the boat.

As far as the FPV, it would likely be updated at a decent rate - maybe 50 or 60 times a second, same as the digital attitude display. The inertial velocities must be sampled at a healthy rate or your nav errors are off the chart. EDITORIAL NOTE: The current use of GPS is super, but I can see less maintenance and care for the "good old inertial" units. But back to the chase - if you are pulling and that FPV ain't moving the same direction as the stick, then you are in a heap of trouble. This is much easier to see in a HUD, as the pitch lines are "real world' and you can only see about 15 degrees total from top to bottom. However, they were extremely helpful maintaining a 3 deg descent angle or any angle you wished. A PAR was so easy it felt like cheating.

PJ2

gums;

Re, "A PAR was so easy it felt like cheating."

Yessir, done them very occasionally in the DC9. Aside from Canarsies onto 31R, that was a leg to get!

I must be out to lunch as I never realized you weren't on earth all the time! The reminder re 'derived' etc was a good one and it got me going too.

bubbers;

Re, "I think I know but Airbus training needs to include how degrading automation needs to let people understand the level of automation they are at."

I trained on the A320 in 1992, the A340 in '99, the A330 a bit later and from the get-go all three laws as well as the protections were heavily emphasized, taught, practiced and checked in recurrent rides. We knew that in Alternate and Direct laws one didn't do anything rash, quickly or rough with the airplane. While it was complicated sometimes, the ECAM was / is very good and must always be done to completion. Forgive me but really, the people who do this work aren't dull or slow.

Re, "2 degrees nose up attitude and cruise power would have made this accident a non event." Well, QED. That's about what the airplane cruises at. Monitor altitude, set power, wait, do the ECAM, get out the QRH. That's why I said very early on, "do nothing, wait..." It's not an emergency.

Regarding pitch, two to 2.5deg NU is the pitch the A330 cruises at and the thrust is already in the CLB detent, so the airplane is immediately both stable and under control which is the first rule, 'aviate'. To change the pitch attitude, (arbitrarily or via the checklist), adds workload and increases the potential for loss of SA as one departs one's cleared altitude and minds the speed, heading, etc and it delays getting on with the ECAM while the PF is ensuring that the airplane remains under control. I surmise that these are the things check airmen argue about in meetings all the time. In my view the UAS drill and checklist is a mess and can, if improperly understood and taught or badly executed, reduce and not increase flight safety.

One thing to note that those who fly these airplanes may not know is, a transport airplane can depart controlled flight very gently almost languidly and smoothly, without broadcasting what it's doing. In the departure from controlled flight into a severe loss of control there was nothing violent about this accident. Even the descent would have been "languid" in terms of pitch, roll, yaw, gee despite the buffeting.

As you must know instinctively from experience, it isn't 10 or 15deg NU that would get the attention of a transport crew, it is a degree or two above nominal. So if the airplane is in stable, level cruise at 2 deg, then a pilot taking it to 3 to 5 degrees (yielding about a 1000 to 1500fpm climb), and keeping it there would require an immediate taking of control to stop a loss of control event and also regain the cleared altitude. Seven or eight degrees pitch at cruise altitude and Mach is positively frightening in my book.

When the ATs disconnect, you'd have to bring the levers back a bit to maintain the previous cruise setting but you'd never overspeed the airplane if you left the TL's alone.

Lyman;

Re, "Is this our friends?"

I don't know. I don't know why this happened. All we know is a bit of how.

HN39;

Re, "Yes, it is possible for AoA to exceed Alpha Prot in Auto."

Absolutely correct. Ask any carrier flying into Mexico City in an A320 about the sharp left turn onto the 5's from the 160R of SMO with the speed right back, landing flap out and an encounter with a bit of turbulence in the turn. It will also occur if one retracts the flaps too early, AP on or off.

3holelover

PJ....
Re: your last image and questions (rhetorical though they might have been): AoA- about 23 degrees, going down at about 35 degrees and you should bleeding well push!... ?

Have I understood the display correctly? ( I don't fly, obviously)

CONF iture

As one image cancel the STALL Warning, temptation to pull can be strong, especially as indicated airspeed is increasing ... Suppose you was already pushing hard at this time.
Note how the big red chevrons do suggest me to pull too ...

bubbers44

Mexico City has the only approach I have ever seen that intercepts the localizier at more than 90 degrees. Also the automation will level you off above the glide slope so you have to TF the altitude to not be high. Trick for those curious. Also they clear you for this long arrival then turn you in short so if you don't know about it you are way too high so have to speed brake the whole arrival.

Clandestino

How in the world did you manage to resurrect this zombie thread again?

Massive it might be, yet it is very succinct with not much duplication or garish. Complex area, such as aviation, can not be explained in simple terms.

False. Once speeds return back to normal, AP is available even as alternate law remains latched for the remainder of the flight. Pages 85 and 86 of the English edition of the final report refer.

Of course, once aeroplane was stalled, turning on the AP was impossible and pretty pointless.

Probably nothing at all. Control inputs and cockpit audio bear no trace of anything that suggest the presence of rationality. They were panic stricken.

No. CM2 kept pulling, First significant input on the left stick was recorded merely 45 seconds before splashdown. CM1 pushed a bit but was counteracted by CM2. After that CM1 started pulling too and reversed to push in a final few seconds.

What the... for Finnegan's sake, have a look at the CM2 stick trace! That's made by a guy who believed he would die if he just lets go of the stick! Such accidents are with us ever since the aeroplanes were first stalled! With all the emphasis in Airbus discussions being on autoflight and FBW, folks tend to forget effing Airbus is still an aeroplane, it stalls if you go over alpha crit!

They moved away from full nose up, which was enough to reduce pitch and promptly provoke another pull to backstop from CM2.

It was answered more than a dozen times in 10 threads. Pity some folks could not understand or did not want to understand as it didn't fit their pet theories.

Pilot did, pilots didn't. Two sticks - two traces.

My gang also prohibited them on 737, ATR, MD-80 and Q400 also stipulated that only one pilot can be at the controls at the time, be it left, right or auto. Wonder why is that.

They took avoiding action. They did not fly through the storm. Where the hell does this hundred times disproved notion they penetrated the active storm cell come from?

It might come as news to some that recorders are fitted to help advance aviation safety and are not intended to be used in connection with civil trials. Even using them in criminal cases is not something aviation authorities look favourably upon.

It's not a key detail but infrared herring. Issue is not handling but having no idea of the aeroplane's energy state. CM2 stalled aeroplane pretty deftly.

Recommend reading "Use of rudder on transport category aircraft". It's applicable to almost anything, "applicable only to Boeings" is just a legal boilerplate.

If I'were to subscribe to the line of thought connecting his postings quality to experience, I would be forced to admit that experience is quite a hindrance in understanding the AF447.

They were quite correct in that respect, too. No aeroplane requires knowledge of manual flight at high altitude.

If the real world conformed to your notions, yes. Fortunately it doesn't care a bit about anyone's ideas how it ought to be. Aeroplane flying high has all the inertia, more speed and a lot less stability & damping compared to the same plane flying lower but it takes a flight of fancy to conclude just from AF447 catastrophe that high manual flight is roughly analog to tight-wire act. Unwholesome experience of TAM crew, as described in 1.16.2 refers.

If I supposed for a second this thread is indicative of the state of the aeronautics, I would have to wholeheartedly agree with you. Luckily, it isn't so.

Are you perchance suggesting it wasn't good enough for them so they went for whole 2000 ft bust?

No way I would volunteer. Would you?

OMG! F-15, F-16, F-18, Rafale, Typhoon, all of the Airbi post 320 are deathtraps, with ueberintelligent pilots required just for everyday operations!

Perish the thought.

Autotrim is just automatic trim. Any aeroplane, anywhere, anytime is properly flown with reference to attitude. Whether the residual stick force after the required performance is achieved is trimmed out manually or automatically is just a minor detail.

Eh... unlike F-16 which has G-trim, Airbus is made to be flightpath stable, so it will achieve 1G in wings level horizontal flight,not by chasing 1G but rather by trying to keep the flightpath constant. If we don't go into details and try to build theories on them, "Stick free it holds 1G" is good enough approximation. Displacing the stick commands the flightpath change with so-and-so gees, proportional to displacement.

Are you accusing BEA of forging the sidestick traces?

Not quite... it will maintain flightpath so left with nose-up, it will increase pitch as airspeed decays and alpha goes up. However, it is not as bad as some try to make it seem. Pilot needs to be quite incapacitated to leave the aeroplane wonder on her own.

Yup, up to the point where flight test data were available. A330 was intentionally stalled during flight testing (and recovered, obviously) but never driven to 40° alpha.

True, but not very applicable to AF447, which was a case of pilots unable to remember and apply basic flying lessons at 4AM, which might be partly affected by not understanding how thin is the Airbus's technological armour shielding from the elements. Precursor of AF447 was described by Wolfgang Langewiesche almost seventy years ago.

That's something you share with about every functional aviation authority in the world.

I'd rather use phrase "cowed by technology" than "having respect for technology" but basically, I agree.

Did and can. I didn't know it was an issue until I read it was supposed to be on this thread.

There were other crews in UAS that had no clue what was happening and had no understanding of the system. They sat puzzled and not doing anything. So survived.

Have a look at the pitch; it's not consistent with CM2 doing low level UAS drill at high level, but rather as if he were trying to run away at all costs from something he believed was coming from below to get him.

They absorbed roll info all right but just couldn't connect the blue on AH and rapidly winding altimeter with idea they will eventually run out of speed and stall.

Lyman

Noted....

However. "Intended" is the backstop for the righteous. Pragmatically, data is data, and is available to whomever can acquire it.

You are a pilot. You by definition deal in reality, not moral judgment.

Therefore....

I direct your attention to the part of the data that is important, to me, that is the beginning, not the end.

This accident happened in twenty seconds, not four minutes. That is my opinion, and always has been.

That is not necessary. At the loss of Autopilot, with cricket and MASTER CAUTION, the aircraft was showing a loss of 370 feet in altitude, and a NOSE DOWN attitude, accompanied by eight degrees of roll, to the right.

PJ2 has posted, initially, "do nothing", which he has amended to mean, don't be precipitous, or ham handed, to which virtually all transport pilots agree.

Pilot flying input NU and RL, as he should. His inputs to me reflected a residual memory of flying in NORMAL LAW, where his inputs would have been modulated.

Big mistake, and perhaps one that caused the crash, at least partially. The next ten seconds show an acclimation to a new and degraded LAW, and an eventual settling of Roll. The PITCH axis remained in a mode that modulated his inputs, and this may have subconsciously affected his muscle memory, in that he was not sufficiently focused on PITCH.

Ninety nine per cent of the posts in this and the other threads focus on the STALL, or the CLIMB, or the CAPTAIN.

It has been established that no one knows what caused the CLIMB, except to hone in on, Pilot Error.

That is fine by me. You?

Lonewolf_50

Howdy, Clanedstino, as usual your comments spice up our discussion.

A few points:
On that we are in violent agreement, but the context of my comment to jcjeant was about the passengers' fear and anxiety being presented in the courtroom as a complaint. Given that they died as a result of the crash, their 'fear and anxiety' seems nearly irrelevant to me ... in that little side bar.
CVR time tags indicate about 2:10 AM to about 2:14 AM as "when" this happened.
His ex wife perhaps? Legend has it that harpies know how to fly. Your post made me chuckle.
At the risk of being pedantic, by "winding" do you mean increasing or decreasing? I presume the former. If you meant the latter, it would indicate "already stalled" to the discerning pilot.

EDIT:
As to "what they were probably thinking" I will mildly disagree with you.
a. Probably thinking "why's it doing that?" or "Why isn't it doing what I expect it to do?" (even though what was expected might not have been aligned with how the aircraft systems work) and then "What's it doing now?" and later on, at least from the right hand seat "WTF is going on here?" There may also have been some background thought on "Why is that stall warning going off?"

b. They indicate a crew behind the aircraft. There were reasons for some of what they did, hence a rational thought process, but those reasons seem to have been based on faulty diagnosis of their problem, faulty recall of procedures, and faulty flying skills, and faulty CRM technique.

c. In the last minute, maybe so, but in the first three, confused more than panic stricken ... unless there's more to my guess about the pursuing harpy than my wisearse comment warrants!

Lyman

But if I wanted to, I would......

A330 has shown some eccentricities in Flight Control, to wit, uncommanded climb.....

Suppose Air France flight 447 had been victim of these "eccentricities"?

The "CLIMB" was instead a desperate attempt by Bonin to FORCE the nose DOWN, not hold it up?

If 447 had been lost to Airbus, not BONIN, what then? Can you imagine?

"AIRBUS kills 228 over the ATLANTIC" Boy Howdy. Until the boxes were found, who could say? Afterwards, and in the possession of an agency that had been accused of criminal conduct to protect the airframer prior, who could say "The pilot performed as expected in the CLIMB emergency, and all the way to the OCEAN"..."He tried the entire while to drop the nose, by pushing the Stick forward".

Without ACCESS? In the possession of those who refuse to release all the DATA?

It would seem a simple task, disclose.

What would I do? Right Wrong or indifferent, I would do the same. Keep the "DATA" secret, and a passive non emotive expression....

Pragmatic.
After ALL, they're all dead.....

PJ2

3holelover;
Yessir, that's what the display says and you've understood it correctly.

It has never been my sense that an AoA indication somewhere on the forward panel or screen real estate would have made a difference to the AF447 outcome. As with the FPV, an AoA indication is part of the kit only when its information is understood within its context of high-altitude, high-speed swept-wing flight.

Lonewolf_50;
In Re the original quote, I took the use of "winding" to mean the climb, (vice the term, "unwinding" to mean a descent).

The altitude and rate of climb would have been visible on both PFDs.

Clandestino;Yes, it's not consistent certainly but merely "mostly in the direction of..." which is inconclusive as to reason and so open only to theory.

The data clearly indicates that in percentage time, the SS was in the NU position most of the time and the left and right elevators were entirely in the NU position throughout the descent:



PJ2

DozyWannabe

Not sure I agree with the first sentence - if HA manual handling was taught as part of basic conversion training, then there would have been a reinforced mnemonic inside the F/Os' heads that pulling up to that extent in the cruise is a very bad idea. As are large control inputs in general.

Agreed - the point I was making is that with this system, the aircraft will do it's best to go exactly where you point it until either it can no longer comply, or until you point it somewhere else. This consequently means that while handling the aircraft is a simpler process, levelling off must be a distinct and conscious act - but that's not really different than for any other type.

Then firstly, do you not think it slightly presumptuous to infer that an accident investigation service who are compelled to abide by strict standards would do the same? And secondly, with due respect, I'm damned glad you're not an accident investigator.

Hopefully this thread will shortly return to rest, 'cos there's nothing new being discussed here.