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Air Asia Indonesia Lost Contact from Surabaya to Singapore

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Air Asia Indonesia Lost Contact from Surabaya to Singapore

Old 28th Jan 2015, 01:17
  #2621 (permalink)  
 
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FullWings completely agree.

Yes, but this may not work immediately in an aircraft with hard envelope protection which is suffering from erroneous inputs. It may be trying to follow a trajectory that is completely wrong for the situation and making it harder to recover by doing things like trimming the stabiliser in the opposite direction needed.

By the time this has been diagnosed by the crew, probably during a time of very high workload in the middle of an upset, it leaves little time for remedial action. “Known power setting and attitude” will not recover the aircraft from a stalled condition. Much more aggressive inputs are required.
These quotes are from (mine and others') posts about 2337. Whilst we're speculating on possibilities, I think we should also look at this in the broader discussion of modern Flt Cntrl laws.

Ice crystal icing, blocked pitots, the aerolane thinks it oversped, then pulled up, overriding the pilots, stalled, got confused and gave up.

How many Airbus incidents have had confusion over what the laws were meant to be doing in the control environment? And, yes I have nearly 5000 hours flying the euro version.
60% of known ice crystal icing events occur in the tropics. If the rate is beyond the ability of the pitot system then I would infer that the blockage would occur at almost identical times and magnitude because of the homogenous nature over the small frontal area of the aircraft. Thus, resulting in an artificial overspeed due to it climbing. It is very difficult for any pilot to do something when the systems designed to protect you are now putting you in harm's way, against your intentions. I've never had it in the aeroplane but have done it in the sim and its the most uncomfortable feeling having FULL forward stick whilst the aeroplane pitches up opposite to your inputs.
Unfortunately, if your climbing, its night time, your looking at the radar, there's associated flashing from lightening, you're thinking about your clearance (or lack thereof), turbulence and the aircraft now "detects" an overspeed... Goodluck! You need to turn off multiple parts of the FCCs or the inputs i.e. ADR an IR (from OEBs) to regain the ability for you to simply level off and set the correct attitudes and power settings. This is from the Airbus manuals - combine voting logic from the section in the FCTM with Overspeed Protection from the Normal Law section in the Ops Manual, throw in a little knowledge about what happens in a climb with blocked pilot tubes and the rest looks like a replay of AF447.

Now, I'm not saying this is what happened but it is feasible and IMHO the most probable scenario. When the pilots most need manual control of the aeroplane, it can be taken away from them. Only, to be handed back when the AoA senses the CA has been exceeded. Helping or hindering?

Something is flawed in the design. Why can't you select the "big,red button" sure, its connected to the ACARS so the company, NTSB and Airbus will all be wanting to know why you did it but you should be able to!
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Old 28th Jan 2015, 02:41
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Exclusive: AirAsia probe vets possible computer glitch, crew response | Reuters

(Reuters) - Investigators probing the crash of an AirAsia jetliner are examining maintenance records of a key part of its automated control systems, and how the pilots may have handled the plane if it failed, two people familiar with the matter said.

An outage of the twin Flight Augmentation Computers (FAC) could not have directly caused the Dec. 28 crash, experts say, but without them the pilots would have had to rely on manual flying skills that are often stretched during a sudden airborne emergency.

"There appears to be some issue with the FAC," a person familiar with the investigation said, adding that more information was being sought from the manufacturer and airline.
The pair of computers comprising the A320's FAC system is mainly responsible for controlling rudder movements and helping to keep the airplane stable, as well detecting windshear, or sudden changes in wind speed or direction.

Indonesian magazine Tempo reported a series of maintenance problems with the computerized rudder system of that particular aircraft in the days and months before the loss of Flight QZ8501.
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Old 28th Jan 2015, 03:08
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Flight Augmentation Computers

FAC - The Flight Augmentation Computers have three main functions:
  • Rudder trim
  • Rudder travel limits
  • Yaw damping inputs
  • Alternate yaw
  • Flight envelope and speed computations
  • Wind shear detection
The most significant function wrt to QZ8501 is probably the Flight envelope and speed computations.
SourceFlight Control Computers | Flight Augmentation Computers
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Old 28th Jan 2015, 03:21
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Several posters have danced around the issue but it's better to be direct. The "Airbus philosophy" of envelope protection needs to be revisited. Either one of two things is going to happen over the long haul.

Scenario One: Flight envelope protection is lost and the pilot guesses. Solution: If all the pilot is going to do is guess the computer can do that just as well and probably better.

AUTOPILOT OFF
AUTO THRUST OFF
FLIGHT DIRECTORS OFF
IF AIRSPEED IS UNKNOWN, SET 90% N1
That isn't difficult logic for software engineers to program...

Scenario Two. Flight envelope protection is lost and the pilot uses his superior flying skills to correct the problem.

This for many is the preferred solution. However, it seems that maybe it isn't working as well as one would hope.
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Old 28th Jan 2015, 03:32
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re " envelope protection"

Seems to me either

1) " HAL" although degraded has the final word or

2) the Pilot has the final control.

All else is 'yea but " arguments.


BA enables 2, Airbus uses 1.

Time for a review or change ??
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Old 28th Jan 2015, 07:13
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All of which, unfortunately, appear to have been disregarded in recent cockpit system integration.
This is because standardisation and saving money by doing things "the way we always did it" is found more important these days, than doing the right thing.
If latest cockpit design would be significantly different from the last generation, pilots would have problems to change between the two, which would either limit the types they are allowed to fly (with all the organisational and financial impact) or it would create new risks. It would also impact all training organisations being forced to teach two different ways of flying. However, somehow we already do have that situation with different aircraft having different levels and type of automation and protections.
Sometimes it is safer if everybody uses a poor design but is well aware how to handle it, than some using an improved design and losing awareness...
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Old 28th Jan 2015, 07:19
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Beginning on 1 June 2009, when 229 souls perished in the Atlantic crossing the ITCZ, in a thunderstorm, punching a cell, crossing extreme shear layers and entering 100+ mph updrafts combined with warm air, followed by 100+ mph downdrafts of cold air and icing conditions -- the anvil portion of the cloud being even more extreme -- weather effects upon AB software have been discussed and re-discussed and recommendations made.

In December of 2014, 168 souls perished in the Java Sea crossing the ITCZ, in a thunderstorm, punching a cell, crossing extreme shear layers and entering 100+ mph updrafts combined with warm air, followed by 100+ mph downdrafts of cold air and icing conditions -- the anvil portion of the cloud being even more extreme....

Both occurring while a FBW system reacts to such insults by trimming the THS to full nose up, and commanding its pilots to follow a flight director that indicates further full nose up, leading to these zoom climbs (The FAC's panicked response to perceived overspeed due to lack of speeds from the pitots and over-reliance on merely the pitots to determine speed.)

I remember being transfixed by the loss of AF447 and following most every thread since then with great interest.

WHENEVER YOU ARE SURPRISED THE MOST IMPORTANT MEMORY ITEM IS:

AUTOPILOT OFF
AUTO THRUST OFF
FLIGHT DIRECTORS OFF
IF AIRSPEED IS UNKNOWN, SET 90% N1
I remember posting back in 2009 on another forum that, at minimum, AB's should have a way of reverting back to manual, 'pilot mode' by providing its pilots with as much information (AoA display being one of them) as possible and providing the pilot with full, cable-and-lever, type control.

After another 168 lives lost, it is time to demand revision to the software. Revisions that gives the pilot back full control of a fully re-trimmed, completely flyable aircraft. I'd suggested back in 2009 that instead of dumping the the aircraft upon the pilots in an out of shape, out of control, "I give up" fashion, that:

The AIRCRAFT in the seconds during transition between AP to manual control, should instead:

1. Re-trim the THS to neutral
2. Re-trim the elevators and ailerons to neutral
3. Rapidly transfer fuel forward to achieve a more forward CG to improve flyability
4. Depending upon the altitude of the craft, and similar to the "exponential rates" and "dual rates" familiar to most radio control flight enthusiasts, give the pilot a dumbed down, not as twitchy/touchy and difficult to fly aircraft when at cruise altitudes, yet still able to provide plane-bending 100% deflections if necessary when control is completely handed to the pilot
and then

5. AUTOPILOT OFF
6. AUTO THRUST OFF
7. FLIGHT DIRECTORS OFF
8. IF AIRSPEED IS UNKNOWN, SET 90% N1
The big red button ought to do all of these things and HAL should press the button himself when unreliable airspeed/AoA sensors or otherwise promote AP auto-disconnect at cruise altitude.

(It would also seem that Airbus now has at least two sets of pretty good data on entry to stall, stall behavior, transition to deep stall, flat spin, 10,000+ per minute altitude loss.... to add to their simulator's knowledge base.)
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Old 28th Jan 2015, 07:29
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Not an Airbus pilot...

Are you saying that the autopilot can never be turned "off" on an Airbus?

You can never "disconnect" the A/P totally and fly it manually at any time?
I have to answer with a "yes, you still can, but ....".

If you "disconnect"the Autopilot, you still guide the Airbus via a Flight Control Computer, which in turn directs actuators and finally the aircraft (same goes with the Boeing FBW system).

The FCC has the famous "protections" built in who restrict the inputs to stay within the programmed envelope. To restrict and direct, the computer needs sensors and those sensors can fail or ice up or etc. etc. The "feeling" of the computer is therefore wrong, just as the resulting restrictions of the inputs will be wrong.

So in short: HAL is still fiddling with flight commands even with the AP OFF.

In an Airbus you would need to force the computer into the famous "Direct Law" to shut out the protections and have almost unrestricted control.
The whole problem is "if", or "how" and "how user friendly" can this be done.

Or in other words: When the hits the fan, does the average pilot have enough possibilities / skill / hard- or software to achieve this in survivable time.
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Old 28th Jan 2015, 08:45
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@ Gretchenfrage...

The FCC has the famous "protections" built in who restrict the inputs to stay within the programmed envelope. To restrict and direct, the computer needs sensors and those sensors can fail or ice up or etc. etc. The "feeling" of the computer is therefore wrong, just as the resulting restrictions of the inputs will be wrong.

So in short: HAL is still fiddling with flight commands even with the AP OFF.
I understand the fact that Airbus designed a "protection" software into their flight computer's program which is fine by me, however are you telling me that if a pitot tube of some other probe (a la AF447) freeze up or just fails to function properly the FCC will still take its inputs and get confused instead of disregarding them and work in a "less than ideal" situation?

If this is a fact then Airbus is pretty stupid in letting a "compromised" sensor render their "protection envelop design" and/or aircraft controllability vulnerable. The compromised sensor should automatically be taken out of the loop and a warning to the crew annunciated immediately.

Furthermore, if the whole FCC is somehow compromised, there should be an easy and quick way to disable it so that the pilot can regain full control of the aircraft (like in a conventional aircraft) albeit without the "protection envelop".

Finally, what I would like to know from an Airbus driver is assuming this crash was related to another stall like the AF447 flight, can a pilot regardless of the FCC's confusion just say "I have control", switch the AP off, the AT to off and FD if need be, fly straight and level and set a given N1 or EPR value to keep the aircraft from falling out of the sky?
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Old 28th Jan 2015, 09:16
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Finally, what I would like to know from an Airbus driver is assuming this crash was related to another stall like the AF447 flight, can a pilot regardless of the FCC's confusion just say "I have control", switch the AP off, the AT to off and FD if need be, fly straight and level and set a given N1 or EPR value to keep the aircraft from falling out of the sky?

Yes you can....fly Pitch-attitude-thrust.. and that is the procedure for "airspeed unreliable"...do all pilots who grew up in these planes have the skills? NO...it's a skill that has over time disappeared...having facilitated many LOFT scenarios in the simulator, it never ceased to amaze me when conflicting information from ADR sensors caused problems, to see how many pilots seemed UNAWARE of their present thrust and attitude before things went haywire..the other fairly recent "surprise" on the 320 family anyway, was water penetrating the seals on the AOA vane shaft and freezing the vane in some undesirable position, forcing the crew to select 2 of the 3 ADR off to place the system in alternate law, removing stall/overspeed protections..

Last edited by ironbutt57; 28th Jan 2015 at 09:27. Reason: helpful spell checker
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Old 28th Jan 2015, 09:43
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@ ironbutt57...

Thank you for the answer.

So in the end in an Airbus you can still fly it like a non FBW conventional aircraft if you required to do so regardless of which "Law" it's in or faults/malfunctions in "Normal Law" or am I and others missing something?

It's all down to basic pilot skills, which it seems a lot of new pilots don't have these days.

This should not be an Airbus versus Boeing debate then.
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Old 28th Jan 2015, 09:44
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Originally Posted by ironbutt57
...the other fairly recent "surprise" on the 320 family anyway, was water penetrating the seals on the AOA vane shaft and freezing the vane in some undesirable position, forcing the crew to select 2 of the 3 ADR off to place the system in alternate law, removing stall/overspeed protections..
I alluded to this earlier, the XL Air /Air New Zealand A320 crash off the coast of Perpignan. It pitched up into a nose high attitude, stalled and fell into the water below. This AirAsia flight seems to have made a carbon copy manoeuvre.

My suggestion that this crash might well be similar to that one was lost in all the Airbus v Boeing control philosophy discussion.
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Old 28th Jan 2015, 09:57
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however are you telling me that if a pitot tube of some other probe (a la AF447) freeze up or just fails to function properly the FCC will still take its inputs and get confused instead of disregarding them and work in a "less than ideal" situation?
As usual : it depends.
Normally a system should detect that the available data is corrupted/invalid/senseless/outside the norm, and hence should not get confused, but take the action it is designed for. Which might be switching off and leave it to the pilot to solve the issue. All input to systems should come from independent and redundant sources (e.g. 3 pitots feeding three air data computers), If one delivers data which is different from the other two, the system should understand that this one is at fault, and use the data from the others. If all three differ, the system should understand that no valid data exists, and act accordingly.
However, being designed by humans there might always be situations nobody ever thought of, and hence did not design the system for. This is valid for any complex product of any manufacturer.
See the Spanair accident in Madrid, where the very old fashioned pre-computer-systems got confused, and did not warn the pilot when having full authority to do something wrong.
Sometimes protections kill you, sometimes the lack of protections does. Sometimes systems safe the day. Some days they fail. Most important is that the pilot fully understands the systems in his aircraft and works with them, not against. A pilot which is not trusting his systems should not fly that aircraft.
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Old 28th Jan 2015, 10:47
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So in the end in an Airbus you can still fly it like a non FBW conventional aircraft if you required to do so regardless of which "Law" it's in or faults/malfunctions in "Normal Law" or am I and others missing something?
Not strictly true

If you turn off AP/ATHR and FDs (in fact FDs academic) then you should be flying "attitude and power". However, if you are in Normal Law, then auto-trim and protections are still present, and you are not commanding control surface movements, but performance changes that the computers action.

In Direct Law the computers are still between the stick and controls, but in a fairly dumb way (stick relates to control surface movement).

Alternate Law somewhere between.

The "problem" some seem very concerned with is when a "protection" incorrectly kicks in, or limits you inappropriately, such it prevents you from flying normal attitudes. The recent OEB I believe, after many years of Airbus FBW Ops, is the first acknowledgement this can happen. Others here claim it has happened on numerous occasions.

I do not see that issue relevant to AF447. Without re-reading the whole thing again, I do not believe a "protection" incorrectly kicked in? Sensor failures led to FBW downgrades and allowed the pilots to fly the aircraft conventionally into an unrecoverable situation.

Perpignan ditto - again faults then downgrades allowed the pilots to crash the aircraft.

China 747 - yes he pulled 5g or whatever, bent the wings, and people say "couldn't do that in an Airbus - they'd all have died". With FBW working, the Airbus would have stopped the situation arising. Even if it got into that, I see no evidence the 747 recovery required 5g? A correctly flown 2g recovery would likely have been fine.

A Qantas A330, then the run up to the OEB, did see the aircraft behave inappropriately due FBW protections (as did a SQ777?). I suspect these are now designed out, or being so.

There are 000s of FBW Airbuses out there, and I doubt more accidents than say 737s? It is not perfect, but then nor is the 737. I very much doubt we will see a significant change (linked sidesticks, moving throttles, Law basics) requiring extensive hardware modification and re-training. I suspect we will see tweaks to the software and training to try and close off the loopholes as they arise.

Won't stop the Airbus bashers on here, who are now so desperate they blame the Airbus for the 777 SFO crash

I fly it, fine piece of kit, would prefer something "fun/real" to fly like the 757, (but get that outside the airline world). It's pretty reliable, albeit has it's French quirks. As is being repeatedly shown however, like all aircraft in the past, it is not crash (or idiot) proof.
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Old 28th Jan 2015, 11:01
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If latest cockpit design would be significantly different from the last generation, pilots would have problems to change between the two, which would either limit the types they are allowed to fly (with all the organisational and financial impact) or it would create new risks.

You're, perhaps, forgetting history. In 1985 I was flying a very, really basic B732. The BY boys will remember. Then we became the lead airline for B767. Wow; this was a quantum leap. Fortunately we had a very strong pilot orientated Flt Ops management right up to MD level. They expected the pilots to be able to fly these new toys with the same competence as B732. We took it to some similar places; i.e. very basic Greek island airports = night circle to land at Corfu, or Kos or Heraklion etc. No problem. The culture was correct. My point is that such a mega change happened without a/c falling out of the sky and without the training department collapsing.

Most important is that the pilot fully understands the systems in his aircraft and works with them, not against. A pilot which is not trusting his systems should not fly that aircraft.

So how did we achieve this safe transition? Firstly the ground school was very thorough. The FCOM's had been simplified & diluted and CBT introduced. But, this was backed up at the end of every day with 'chalk & talk' FAQ's with a FE. During the CBT we used the sim as an FTD to explore and experiment with what we had learned that day. We came out with a healthy knowledge. We then went on the line and plugged in the automatics at 400' and watched what the a/c did; how it wanted to fly. We tried all the different methods via AFDS and learnt in depth how to fly & manage this new beast. The LTC/TRI/TRE's had a real indepth understanding and passed it on. When possible we hand flew it as that was the culture of the company. We'd learnt from the automatics what was necessary and then we applied it manually. Job done.

I then went to an airline who transitioned from B727 to B757. I took my BY philosophy with me, but had a culture clash. They insisted in a complete change and it became a "follow the FD" type operation with full automatics. The older guys flew it manually, but the newbies didn't know how and switching off the VNAV for descent planning was scary. Switching off the FD for departures from small empty airfields or approaches was even more so. Switching off the ILS on a CAVOK day was the final straw for some. All this was 25 hears ago.
I now fly B738 and HAL has sporned and migrated onto that fleet as well. I still fly my way and try to encourage others, but the ice is too thin and they don't want to venture out. OFDM is watching and they are afraid. When some do 'have a go' it might be a mess. They have a confidence blip and complain they don't get enough practice. True. I also teach TQ and they never had the skills in the first place via the syllabus. Hand flying on the line is discouraged and strict SOP's cause a trained monkey mentality. They know only a fraction of the capabilities of both the a/c and the systems.
You can only "trust your systems" if you understand them. Guys fly the a/c using the A/P looking only at the FD. It will always be centred, even when you stall or hurtle into the ground. It tells you nothing and can mask the truth of what is happening, i.e. attitude and V/S. In todays automated dependant operation the basic instrument scan, to confirm the FD is giving healthy guidance, is no more. It wasn't taught, save the raw data ILS, and it not used on line due to fully automatic operations. What chance have they got when the missing skills are needed? The way EASA is going I do not hold out any hope. Keep everything as cheap and as simple as possible just to be inside the safety envelope. Enough. Perhaps the days of single crew 99% automatic flight is not that far away. I'm sure the companies would love it. Any faults and the computer tells you how to fix it. That's not always a success if the computer is at fault. Bit like asking the police to conduct the enquiry into the police. The independent pilot needs to sort out the mess and decide if the computer solutions are correct: if not take over and save the day.
Ah, but that takes us back to the beginning and the circle is complete, or rather the spiral.
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Old 28th Jan 2015, 11:09
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@ NigelOnDraft...

Not strictly true

If you turn off AP/ATHR and FDs (in fact FDs academic) then you should be flying "attitude and power". However, if you are in Normal Law, then auto-trim and protections are still present, and you are not commanding control surface movements, but performance changes that the computers action.

In Direct Law the computers are still between the stick and controls, but in a fairly dumb way (stick relates to control surface movement).

Alternate Law somewhere between.
I basically understand the 3 "Laws" of the Airbus.

Again I am asking, in "Normal Law" with all protections working, if you get caught in a 3000 feet/min updraft (for argument's sake) and you feel the aircraft is not reacting properly for what ever reason it (the aircraft's FCCs) think, can you just turn "OFF" the AP, AT and FDs and fly the darn thing to a pitch/attitude with a manual power setting on the engines to prevent or reduce the rate of climb or will the FCCs say tough luck pilot I'm still deciding what's best?
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Old 28th Jan 2015, 11:18
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RAT 5 - an excellent summary of where we are today People scared to manually fly, either through lack of familiarity, fear of QAR monitoring, get rusty..

Again I am asking, in "Normal Law" with all protections working, if you get caught in a 3000 feet/min updraft (for argument's sake) and you feel the aircraft is not reacting properly for what ever reason it (the aircraft's FCCs) think, can you just turn "OFF" the AP, AT and FDs and fly the darn thing to a pitch/attitude with a manual power setting on the engines to prevent or reduce the rate of climb or will the FCCs say tough luck pilot I'm still deciding what's best?
If the Aircraft is serviceable, and you do not demand an "outrageous" attitude or speed, then yes - and indeed it is "Airbus Golden Rule 1" I think: If you don't like or understand what it's doing, take control.

I likely confused you with the earlier reply because the simple answer would be picked up by the Airbus bashers that in exceptional circumstances, the one word answer would not be correct
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Old 28th Jan 2015, 11:23
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I alluded to this earlier, the XL Air /Air New Zealand A320 crash off the coast of Perpignan. It pitched up into a nose high attitude, stalled and fell into the water below. This AirAsia flight seems to have made a carbon copy manoeuvre.

My suggestion that this crash might well be similar to that one was lost in all the Airbus v Boeing control philosophy discussion.
Is there any evidence of this aircraft also having been heavily pressure washed immediately prior to takeoff such that both AOA sensors were filled with water below the seals causing them to freeze at exactly the same time (at FL370+ ) and AOA and thus confuse the AC into thinking they were both still working?
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Old 28th Jan 2015, 11:55
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No, but replace pressure washers with rains aloft hitting a fuselage doing 300 something MPH and the effect should be similar
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Old 28th Jan 2015, 12:02
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@ NigelOnDraft...

So that I understand this "autotrim" feature that keeps coming back in many conversations...

Do I understand this feature correctly as a pitch trim that is activated automatically whenever an extended pitch input (up or down) is commanded through the sidestick?

In other words if I command a pitch up from the sidestick, it trims in a nose up to relieve back pressure on the elevator not unlike when you fly a conventional aircraft in manual when using the electric trim or basically the same way an aircraft on AP would trim itself?

If I'm correct in my assumption as stated above? If so what is the big deal behind this feature on the Airbus?

Assuming the THS is trimming a nose up attitude because you are pulling on the sidestick, wouldn't the reverse also be true… that with a nose down input the THS would trim nose down?

Assuming you are in cruise at FL370 in an Airbus 320 and all is working properly, you then encounter some mountain wave turbulence or something similar to it, what usually happens at first in an increase in speed with a tendency in an increase in altitude usually compensated by the AP.

In the above scenario in a very conventional aircraft with a basic AP without AT, if left unchecked and if the power is not reduced, the aircraft may overspeed but it should hold altitude. In an aircraft with AT, the FADECs should automatically reduce to a power setting as to avoid overspeed.

However it seems from reading on here that the Airbus might want to pitch up to avoid overspeeding, is this correct? At what point will the Airbus reduce power to keep it within the normal parameters?

Back to AF447 and the THS being full nose up. If the pilot would have just inputed a full nose down on the sidestick, wouldn’t the THS trimmed nose down too?
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