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Old 03-14-2019, 06:13 AM   #91
Thorsten
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The time it takes from the first sign of something going wrong to an unrecoverable upset can be surprisingly short. Add in a few moments of doubt as to whether it's the AP or something else causing an unusual attitude, or whether the observed movement is a momentary transient, and you may already be screwed by the time you hit the disconnect.
That's certainly true for some cases - if you're operating an aircraft near the coffin corner, then you might have a few seconds to stall, if you're in a Shuttle at max heating, then.. well...

I guess generally the pre-requisites to successful intervention are:

a) you need to recognize the off-nominal situation, i.e. be aware what the current situation is, what needs to be done and that the AP is not doing it

That requires that you're actually using the freedom the AP gives you to keep your attention on the situation - are the sensor readings plausible? Does airspeed match and Mach number match AoA? That kind of thing. If you're making a cup of tea while the AP flies, you won't react...

b) you need to be confident of your manual piloting skills - I guess that's something I've primarily seen from virtual Shuttle pilots - the majority of them who got killed by the AP simply do not know how to fly an entry manually, so they would also be lost when disengaging the AP. This seems to be less true for simulated airliner pilots, who generally appear to have a good grasp of manual flying

c) you need to know the disengagement procedure and the ability to manually deal with transients and the off-nominal situation

In many planes, it is quite possible to even end a flat spin if you have some altitude left - but not every virtual pilot knows how this is done.

***

Among many other experiences during testing, I've had my Shuttle AP try to invert me during entry once as well, I've never found the root cause, probably an integrator windup - what tripped me off was already the attempt to roll beyond 80 degree bank angle, this seemed completely not justified given the situation and in fact is beyond the coded limit angle, so at that point I disengaged and flew manually - turned out I was unable to re-engage in any phase, so in the end I made it to a location a few meters off the runway at Easter Island (I had cloud cover and was so busy piloting I failed to intercept TACAN, by the time I discovered my inertial position was massively off, it was a bit too late... a co-pilot would have helped a lot...)

Generally, I'd say that I get rarely killed by a virtual AP, probably 9/10 times I manage to disengage in time and save the day - I suspect largely not because I'm a brilliant well-trained pilot, but because I've programmed too much to trust a piece of code overly much. Most of my virtual crashes are classic human errors in judgement (weather doesn't look that poor, I should be able to do that...) or a learning curve of course (for learning to land helicopters you need either an instructor or patience and frustration tolerance...)
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Old 03-14-2019, 07:17 AM   #92
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And it was decided the black boxes go to the evil empire: Germany.

The BFU (federal agency for aircraft accident investigation) will do the analysis... so, the blackboxes will be next to my former workplace.

Aaaaaaaand... its already old news. The BfU rejected because they lack the equipment to read the FDR, because it is a newer model with newer software. Instead of talking nonsense about aircraft carriers, our politicians should better invest the money into the BfU...



Now the BEA of France will do the analysis.
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Old 03-15-2019, 07:40 AM   #93
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Unconfirmed reports that the stabilizer incidence jackscrew has been located in the wreckage field... and that its all the way to the (aircraft) pitch down stop.
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Old 03-15-2019, 07:53 AM   #94
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 Unconfirmed reports that the stabilizer incidence jackscrew has been located in the wreckage field... and that its all the way to the (aircraft) pitch down stop.

Had the part been recovered at Lion Air 610 as well? The suspected MCAS behavior exactly predicts this state of the part, the MCAS driving the pitch trim to pitch down stop in pulses.



Confirmed reports also state that the pilot of Ethiopian Air 302 reported problems to control the aircraft already a few minutes after take-off and requested to return to the airport for an emergency landing.
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Old 03-15-2019, 03:17 PM   #95
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No clue on Lion Air 610, but I would expect they have found it by now.
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Old 03-15-2019, 03:36 PM   #96
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 No clue on Lion Air 610, but I would expect they have found it by now.
Well, it could be in a too bad state to draw any conclusions about the trim before crash.
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Old 03-15-2019, 05:15 PM   #97
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I've not really been following this in depth, and I don't know the 737 (or others), but it looks like the pitch trim was driven with data from a single sensor.... maybe I'm too much into the space shuttle and its quadruple systems but, on a plane full of people, isn't having systems with a single sensor asking for trouble?
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Old 03-15-2019, 05:36 PM   #98
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 I've not really been following this in depth, and I don't know the 737 (or others), but it looks like the pitch trim was driven with data from a single sensor.... maybe I'm too much into the space shuttle and its quadruple systems but, on a plane full of people, isn't having systems with a single sensor asking for trouble?
It is. That's what is so disturbing to me as a mechanic. We JUST covered flight instruments this quarter, and the fact that MCAS is using a single sensor feed is, while legal, flying in the face of over half a century of conventional wisdom. Most instruments used for IFR flight use separate and parallel sensors/inputs to ensure at least one is working at all times. Your artificial horizon gyros even go so far as to use separate power sources, typically electrical for pilot and vacuum for copilot, so that the failure of one power source won't take out all your gyros.
Furthermore, the fact that this was allowed to fly by the FAA raises some... disturbing questions about the FAA's ability to remain impartial in their oversight of Boeing. Combine that with the extended delay before grounding the MAX family altogether, and I'm increasingly of the opinion that the FAA and Boeing are a little too intertwined right now.

Also, although not directly related to the accident, but still in the "this isn't exactly a coincidence" category... the production line for the KC-46 up at the Everett widebody facility has been having issues with leaving tools, parts, and assorted other FOD inside the fuselages of KC-46s, sometimes not being found until acceptance by the USAF. I'm seeing a pattern beginning to emerge that Boeing is having some serious internal issues that need to be addressed, and quickly.
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Old 03-15-2019, 05:42 PM   #99
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 I've not really been following this in depth, and I don't know the 737 (or others), but it looks like the pitch trim was driven with data from a single sensor.... maybe I'm too much into the space shuttle and its quadruple systems but, on a plane full of people, isn't having systems with a single sensor asking for trouble?
I agree; especially since I've heard (perhaps I'm wrong) that most MCAS systems never rely on just one sensor; (not just for space shuttles) but use at least two primary and a few secondary sensors to correlate. So, if they're using only ONE malfunctioning angle of attack sensor on the MAX to trim elevator down every 5 seconds; then we're reaching the level of absurdity on Boeing's part and makes one wonder where they're finding their "engineers".... or has political correctness with quotas meant too much sacrificing of competence? Or is this just bad over-all cultural corruption problem in Boeing these days--not even identifying the MCAS stall recovery function in the POH? (Unless I've been misled with this news as well).

Last edited by skyeboy; 03-15-2019 at 05:46 PM.
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Old 03-15-2019, 06:50 PM   #100
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Originally Posted by GLS View Post
 I've not really been following this in depth, and I don't know the 737 (or others), but it looks like the pitch trim was driven with data from a single sensor.... maybe I'm too much into the space shuttle and its quadruple systems but, on a plane full of people, isn't having systems with a single sensor asking for trouble?

Exactly - now, that isn't far below civil airflight standards, for example on Airbus, one sensor supplies one computer and one half of the cockpit, but then, two ELAC computers together make up the FBW. (conflicting sensors result in downgrade of FBW)
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Old 03-15-2019, 08:26 PM   #101
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But, it's still tolerant of a single failed sensor, right? That's the rub of the issue with MCAS on the MAX. It's NOT tolerant of a single failed sensor.
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Old 03-15-2019, 08:49 PM   #102
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 But, it's still tolerant of a single failed sensor, right? That's the rub of the issue with MCAS on the MAX. It's NOT tolerant of a single failed sensor.

No. It is not, as you can see with the AF447 crash.



The important difference is: On the 737 MAX, an FBW-like component tries to kill you when one sensor fails. On any Airbus aircraft, the FBW shuts down all advanced functions when a single sensor fails, completely changing the flight characteristics and leaves it to the pilots to fly a completely different aircraft from one second to the other.
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Old 03-15-2019, 08:57 PM   #103
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Aaaah, I thought they'd fixed that.
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Old 03-15-2019, 09:13 PM   #104
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 Aaaah, I thought they'd fixed that.

No, they essentially just made a few optional features of the Airbus family standard - they now have a very explicit warning for dual input situations and a PFD function that assists during air data conflicts to help estimating forward speed by variometer and attitude. Both software features had been available before to airlines.



The BEA had recommended to FAA and EASA to make AOA indicators mandatory, the FAA has only made it mandatory for general aviation, not commercial airlines. Both Airbus and Boeing have no AOA indicators right now.
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Old 03-15-2019, 10:44 PM   #105
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Whether or not AOA sensors are generally required, they should certainly be required when an automatic system is able to modify the pilot's flight control inputs based on AOA (such as FBW or stick pusher systems).
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