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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 19th Apr 2022, 10:19
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"(Actually, since Airbus hides in fact the entire THS from the pilot, if the pilot is made aware of a THS movement it is necessarily a surprise)"
The THS is not "hidden"; the trim wheels either side of the thrust lever quadrant clearly show any THS movement. Auto trim would not be a surprise to a properly trained Airbus FBW pilot.

Mechanically coupled side-sticks would need to have joints, bearings, levers etc, and would require a mechanism to uncouple the sticks, all of which could jam and cause more problems than it might solve.

Hence, if the side-stick position indication display - see below - that we use to check our controls before take-off were to reappear on both PFDs in the event of a stick being held at or near a limit in flight, then both pilots - and a third pilot - would be able to see on both PFDs what was happening. It would only take a couple of lines of extra program code in the software to add this feature.


From Airbus FCOM:



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Old 19th Apr 2022, 10:57
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I could never understand why this is isn't a standard feature, the cross should be visible anytime the aircraft is being manually flown. Of course this would require Airbus admitting that the flight control system has a few shortcomings which they are never likely to do.
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Old 19th Apr 2022, 12:27
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No thanks, the "Bird" is available. Attitude is important not stick position. It has been removed earlier in the rotation by Airbus as it was being used as a rotation "attitude", which caused an interesting departure from J'Burg for one carrier.
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Old 19th Apr 2022, 15:43
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Originally Posted by vilas View Post
When you pull or push the stick it is to change the attitude which you have to see on the PFD. 447 guy just pulled never looked at the pitch. They didn't see anything nor hear the stall warning. AT FL350 pulling 16° pitch is irrational. The pilots didn't know unreliable speed procedure and stall recovery procedure either. That may have triggered the fear factor causing loss of cognitive awareness. That's why all their actions appear irrational. Connected stick may have some virtue but if pilot doesn't know if pull is correct or push then it's not going to help.
Anyway ultimately the automation has come to rescue again. Now there's fourth source that is called Digital Back Up Speed it's calculated speed from load factor, CG etc. without any anemometric data that compares normal ADR speeds. Whatever is outside threshold is rejected through ECAM actions. If all are wrong then digital speed is displayed which you fly. In A350 it's automatically done. So no more 447.
Where did you see 16° pitch ?
I read 11°, which is still way too much of course.

In this accident, I think contrarily that too much automation is the cause.
Since RVSM, it is not possible anymore to hand fly at high altitudes. And how much sim time is there to train hand flying at altitude ? Maybe less than 10 minutes in the entire type rating and then less than 5 minutes every three years...
If hand flying at altitude was allowed, it would not have disoriented them that much.

Let's simplify the matter. Have you heard of a single GA crash where the pilot lost control, stalled or crashed, with no medical condition, in clear skies, while attempting to fly straight and level ?
Well I don't think so because flying straight and level is basic flying, which GA pilots are trained for and do all the time (most light GA don't even have an AP let alone FDs). Or if it happened, said pilot should never have gotten his license in the first place. But it's perfectly possible to have three full ATPL pilots with less than 3 hours (total) manual flying at altitude and 0 minute real manual flying at altitude in the aircraft.

Light aircraft do crash (even a lot) but for other reasons.
Originally Posted by Bidule View Post
You should read the Accident Report for this Perpignan flight, which by the way was not a commercial flight. You will then see that it is much more complex than what you summarised to try supporting your views.

.
Can you tell me in which ways ?
I read the report, I know it wasn't the designed, nominal functioning of the airbus because the AOA froze, but the THS able to go fully up is nominal.
Here is a google translate from the report :
At 15 h 45 min 19, the stall warning stopped. The captain's longitudinal input is still full forward. The elevators reach their maximum nose-down position at approximately 11.6 degrees.
The bank was 40 degrees to the left and the Captain gradually canceled his lateral order. One second later, the aircraft is in a 7 degree pitch attitude. Its wings were close to horizontal and its speed was 138 kt. The Captain canceled his longitudinal order. At 15 h 45 min 23, the pitch attitude and altitude then began to increase. The altitude reached approximately 2,250 ft. The Captain immediately gave a longitudinal stop forward order.
With 7° pitch attitude, wings level, 138kt, TOGA. With a THS at neutral the aircraft is saved. With a THS fully up, 2-3 seconds without a fully down order on the sidestick killed them, with a 50° increase in pitch in less than 20 seconds.
On any normal aircraft, this pilot would have completed his test with no problem at all.
The pilot should have been made aware that his trim was doing a runaway.

My view is that the responsibility of the pilot does not exonerate the manufacturer from having to provide the pilots with an intuitive, safe aircraft, that won't do anything dangerous unexpectedly and with no information. In short, that is the contrary of MCAS style design. Am I wrong to think so ?
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Old 19th Apr 2022, 18:38
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Originally Posted by Bidule View Post
You should read the Accident Report for this Perpignan flight, which by the way was not a commercial flight. You will then see that it is much more complex than what you summarised to try supporting your views.
Perpignan was due to pressure washing of AoA probes which is not to be done. Water ingress into No.1 and 2 probes which froze at higher threshold after takeoff. No.3 which correct was kicked out by the rogues. Unscheduled last minute check of low speed protection with gear down airspeed reduced very low and when aircraft dropped wing it transitioned to direct law. The THS auto trimmed full up due to wrong SW threshold of 1&3. In normal law THS stops trimming at alpha prot.
Lastly 447 was beaten to death by 24000 posts on PPRuNe. Nobody can discover anything new that wasn't already.

Last edited by vilas; 20th Apr 2022 at 06:08.
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Old 20th Apr 2022, 07:35
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CVividasku
In 2006 or 2008 Airbus considered connected side sticks and didn't find it particularly useful and rejected it. In 2014 about the SFO crash NTSB asked Boeing to have look at their throttle hold function Boeing will keep looking but not going to do anything about it. High level handling is not possible because the planet is RVSM.
What is possible is to explain the pilot the normal attitudes at higher levels and tell him that at those levels in alternate law pulling on the stick without looking at PFD can be fatal. It is possible to teach him stall recovery as is being done. Tell pilots that even on autothrottle you cannot fly an approach without monitoring your speed. When automation reaches those perfect levels nobody will higher someone to sit in the cockpit. Already technology is moving towards that. It's matter of which is easier to eliminate, the human error or the human himself?
Already Airbus and Boeing have created a speed without anemometric input. Airbus calls it digital speed, Boeing calls it synthetic speed? That can be used in 447 situation. A350 has auto TCAS, auto EMER descent. It's not Airbus or Boeing it's the march of technology.

Last edited by vilas; 20th Apr 2022 at 08:02.
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Old 20th Apr 2022, 08:56
  #1667 (permalink)  
 
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Originally Posted by CVividasku View Post
The pilot should have been made aware that his trim was doing a runaway.
Any properly trained Pilots should notice if the trim is doing a runaway. It's barely moving in normal flight ( on A320 at least) and if for any reasons it's going crazy, it's easy to override it manually.
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Old 20th Apr 2022, 10:13
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Originally Posted by pineteam View Post
Any properly trained Pilots should notice if the trim is doing a runaway. It's barely moving in normal flight ( on A320 at least) and if for any reasons it's going crazy, it's easy to override it manually.
Really ?
I did the complete A320 TR and flew for only 4-5 minutes in direct law with man pitch trim.
Then I never had to worry about this wheel ever again.
I never had any trim runaway exercise or anything similar.

Plus, the wheel is not in the primary visual circuit, not even in the secondary visual circuit, and many accidents showed that it's not that easy to notice and override manually (Boeing had the same flaw with MCAS). And if you missed the movement, there is not a single indication that visibly indicates that there is something dangerous back there.
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Old 20th Apr 2022, 13:53
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Originally Posted by CVividasku View Post
........In this accident, I think contrarily that too much automation is the cause............The pilot should have been made aware that his trim was doing a runaway...............My view is that the responsibility of the pilot does not exonerate the manufacturer from having to provide the pilots with an intuitive, safe aircraft, that won't do anything dangerous unexpectedly and with no information. In short, that is the contrary of MCAS style design. Am I wrong to think so ?
Automation is a fact of airline flying in today's busy airspaces. Going back to less or no automation is simply not going to happen. Pilots must only use the appropriate level of automation for the task, therefore pilots need to be properly trained how to understand and use the automation correctly. This is where a lot of problems seem to be arising. My classmates and I spent about 6 weeks in a classroom being taught about the Airbus FBW aircraft; followed by 4 weeks in the Sim; followed by 6+ weeks line training; followed by our final line check. Does this still happen, or is it a few days in front of a CBT computer before a reduced Sim and reduced line training?

The Airbus THS movement is clearly shown by the two black and white painted trim wheels.

After being type-rated on a number of conventional turboprops and jet transports, I found the Airbus FBW to be very intuitive - as long as you understand how the FBW works and how it helps you. I have observed some pilots who think it is fighting them etc., because they don't understand it.

Airbus FBW is a very good design and well engineered product - an order of magnitude better than what existed before its introduction. Nothing can ever be completely fool proof however, which is why the authorities rightly demand ATPL licences and type ratings - to ensure that aircraft are flown by capable professionals, not fools.
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Old 20th Apr 2022, 15:24
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Originally Posted by CVividasku View Post
Really ?
I did the complete A320 TR and flew for only 4-5 minutes in direct law with man pitch trim.
Then I never had to worry about this wheel ever again.
I never had any trim runaway exercise or anything similar.

Plus, the wheel is not in the primary visual circuit, not even in the secondary visual circuit, and many accidents showed that it's not that easy to notice and override manually (Boeing had the same flaw with MCAS). And if you missed the movement, there is not a single indication that visibly indicates that there is something dangerous back there.
Yes really. I mean on Airbus, if you release the side stick and the pitch is going up or down then there is a big chance it is related to the trim. I had a case while hand flying on the real aircraft that every time I was releasing the side stick the nose was going down. During the whole approach I had to keep constant back pressure similar like the flare mode but much less. I did not trim the aircraft manually cause I was still in normal law, aircraft still under control with light back pressure on the sidestick and no ECAM but I would definitely if it was a violent pitch up or down moment.
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Old 20th Apr 2022, 16:28
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In Airbus computers are monitoring. Any uncommanded stab the ELAC will be knocked out and passed on to the next. There's simply no abnormality like runway trim. There's jam stab. Anyone who has done it in conventional aircraft knows how tough it is. Not so in Airbus because elevators are held in the given position.
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Old 20th Apr 2022, 17:11
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Originally Posted by CVividasku View Post
Let's simplify the matter. Have you heard of a single GA crash where the pilot lost control, stalled or crashed, with no medical condition, in clear skies, while attempting to fly straight and level ?

On any normal aircraft, this pilot would have completed his test with no problem at all.
The pilot should have been made aware that his trim was doing a runaway.

My view is that the responsibility of the pilot does not exonerate the manufacturer from having to provide the pilots with an intuitive, safe aircraft, that won't do anything dangerous unexpectedly and with no information. In short, that is the contrary of MCAS style design. Am I wrong to think so ?
Would you call a B737-300 a normal aircraft? Would you think the crew of a B737 would recognise the pitch trim winding slowly backwards with the AP engaged on an ILS APP as the speed reduced? I suggest you read B737 GA at Bournemouth

"During the go-around the aircraft pitched up excessively; flight crew attempts to reduce the aircraft’s pitch were largely ineffective. The aircraft reached a maximum pitch of 44º nose-up and the indicated airspeed reduced to 82 kt. The flight crew, however, were able to recover control of the aircraft and complete a subsequent approach and landing at Bournemouth without further incident. "

Crews need to be constantly alert and not become "passengers" by assuming their aircraft will perform flawlessly every time.
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Old 20th Apr 2022, 17:34
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The pilot should have been made aware that his trim was doing a runaway.
This was not a runway at all. It trimmed as designed. Airbus design the system trims for you. This test profile was only meant for a test pilot not a line pilot. That too the pilot suddenly decided to do it at low altitude without any briefing. When NO.3 ADR triggered a stall warning they should have abandoned the exercise. But they dropped speed below that. Even in alternate law if you don't keep back pressure on stick the nose will drop and it will stop trimming.
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Old 20th Apr 2022, 17:47
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[Pax] Have Airbus modified the stall warning logic, ie the blanket inhibition below 60kts ?
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Old 21st Apr 2022, 00:11
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Originally Posted by CVividasku View Post
Really ?
I did the complete A320 TR and flew for only 4-5 minutes in direct law with man pitch trim.
Then I never had to worry about this wheel ever again.
You should look for and notice the THS trim wheel movement during every flight. That and the speed trend arrow tell you what is going on with your aircraft.

Plus, the wheel is not in the primary visual circuit, not even in the secondary visual circuit, and many accidents showed that it's not that easy to notice and override manually........
Come on, both trim wheels are in plain view next to the thrust levers, they most certainly should be in your scan. To override THS trim you simply put a hand on a trim wheel and it will stop and the autopilot will disengage.
And if you missed the movement, there is not a single indication that visibly indicates that there is something dangerous back there.
There is nothing 'dangerous back there' to a properly trained Airbus pilot. I think you have been very badly taught the Airbus and also your scan needs revising and improving. I think your problem is with your 'trainers' not with Airbus design.
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Old 21st Apr 2022, 13:58
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Originally Posted by Uplinker View Post

The THS is not "hidden"; the trim wheels either side of the thrust lever quadrant clearly show any THS movement. Auto trim would not be a surprise to a properly trained Airbus FBW pilot.

Mechanically coupled side-sticks would need to have joints, bearings, levers etc, and would require a mechanism to uncouple the sticks, all of which could jam and cause more problems than it might solve.

Hence, if the side-stick position indication display - see below - that we use to check our controls before take-off were to reappear on both PFDs in the event of a stick being held at or near a limit in flight, then both pilots - and a third pilot - would be able to see on both PFDs what was happening. It would only take a couple of lines of extra program code in the software to add this feature.

I think there is something inconsistent in what you're saying.
You're saying that the THS is not hidden, and that the trim wheels clearly show any THS movement.
But at the same time you say that the opposite sidestick is not visible enough.
In fact, the opposite sidestick is approximately as visible as the trim wheel, if not a bit more. It is in the peripheral vision, not in the primary or secondary visual circuit.

So I don't see why you would oppose making the THS more visible, while advocating for making the sidestick more visible.

I understand even less when considering that pitch control is achieved with both THS and elevators, trim wheel and sidestick.
Originally Posted by Uplinker View Post
Airbus FBW is a very good design and well engineered product - an order of magnitude better than what existed before its introduction. Nothing can ever be completely fool proof however, which is why the authorities rightly demand ATPL licences and type ratings - to ensure that aircraft are flown by capable professionals, not fools.
Reality is a bit different.
Airbus design directly contradicted the usual rules that existed before. And uncommanded THS movement is directly involved in this.
Aircraft are supposed to have a positive longitudinal static stability. Airbus FBW does not behave like that, "thanks" to THS moving automatically.
It has been deemed acceptable only with protections, and when those fail, you have an aircraft that would not be certified, with no information to the pilot.
Originally Posted by Goldenrivett View Post
Would you call a B737-300 a normal aircraft? Would you think the crew of a B737 would recognise the pitch trim winding slowly backwards with the AP engaged on an ILS APP as the speed reduced? I suggest you read B737 GA at Bournemouth

"During the go-around the aircraft pitched up excessively; flight crew attempts to reduce the aircraft’s pitch were largely ineffective. The aircraft reached a maximum pitch of 44º nose-up and the indicated airspeed reduced to 82 kt. The flight crew, however, were able to recover control of the aircraft and complete a subsequent approach and landing at Bournemouth without further incident. "

Crews need to be constantly alert and not become "passengers" by assuming their aircraft will perform flawlessly every time.
Well, with AP engaged the trim can do what it wants.
I never flew the B737, so I don't know how that one behaves, but I have a clear idea of what I would think ideal.
It would be ideal if the stick longitudinal position represented the total pitch moment. Fully back : everything is pulling fully up (THS and elevators), and vice versa.
So if your aircraft is slow, you feel it because your hand/arms are backwards. That is, if your airplane is an awkward position you will feel awkward too.
And the trim only purpose would be to set the zero force position.

If I recall correctly, light aircraft with an AP work like this, and you've never heard of a pilot who applied the right flying technique stall and crash in this type of aircraft (or if you did, it was because of other factors such as flying recklessly into conditions that they're not trained or equipped for). And they have much less yearly experience than airline pilots.
There is nothing 'dangerous back there' to a properly trained Airbus pilot. I think you have been very badly taught the Airbus and also your scan needs revising and improving. I think your problem is with your 'trainers' not with Airbus design.
I'm sorry but my airline uses the standard airbus TR. The trim wheel was never in the scan. The amount of manual flying in degraded situations is minimal, just read the latest syllabus to count how many minutes there are...
And if this type of unexpected THS behavior crashed at least 4 medium/large hulls (I'd have to look for others) then I don't see how you can deny that it's dangerous.
Did you imagine yourself for one second with the THS going unexpectly full up ?
Even if you noticed, did you imagine yourself pushing down the wheel ? How many turns would that be ? How much time would it take, with both hands ? What else could you be doing at the same time since you would have to look at the small numbers in the pedestal ?
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Old 24th Apr 2022, 13:46
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For the sake of honesty, I just read again about the flydubai crash. It showed that there were also accidents where the pilot was in full awareness of the THS position.. So I guess there is no simple answer. Maybe mixing the advantages of both systems would help.
A system in which the airplane helps the pilot but in complete transparency.
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Old 27th Apr 2022, 00:26
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Given how the crew spent 90-95% of the time with the stick aft of center requesting nose-up response, the argument over how “hidden” the airplane’s lack of nose-down authority was, seems to me kind of moot.

Last edited by Vessbot; 27th Apr 2022 at 02:47.
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