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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 20th Mar 2019, 10:09
  #2121 (permalink)  
 
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Lion airs flight the day before , they say the switches where turned off ? I believe the stick shaker was on constantly for entire flight ? Is it possible to turn off trim motors so elevator / stab is not being affected by faulty pressure instruments but stick shaker and other systems are still affected ?
How to switch pressure sensor systems ?
If you switched pressure sensor systems would it fix MCAS and other systems ?
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Old 20th Mar 2019, 10:25
  #2122 (permalink)  
 
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Lion airs flight the day before , they say the switches where turned off ? I believe the stick shaker was on constantly for entire flight ?
This raises an interesting point:
Ordinarily the switch position ought be detailed in the maintenance documents. Presumably the maintenance entry ought have mentioned the STAB TRIM CUT OUT switches with guard open in cutoff?
This is pertinent because engineering or the next crew must have reset the STAB TRIM CUT OUT switches.
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Old 20th Mar 2019, 10:52
  #2123 (permalink)  
 
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Originally Posted by Octane
Perhaps the 3rd set of eyes in the first Lion Air incident spotted the trim wheels whirring away in the nose down direction and realised what was going on whilst in the accident aircraft the 2 crew in the mayhem didn't..
Or to put it another way: A flight engineer is needed to watch the trim wheels and if necessary switch off Stab Trim, as pilots do not switch off the Stab Trim even after repeated uncommanded nose down stab trim starts making it close to impossible to pull the yoke back and keep the aircraft level
is that what you meant?

Or was the third set of eyes the only one not saying: "it can't be runaway trim as that is continuous and this is repeated - so we won't do that checklist and switch off the Stab Trim"
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Old 20th Mar 2019, 11:08
  #2124 (permalink)  
 
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The FAA's directive orders airlines within three days to update flight manuals to include specific steps pilots should take to recover.

"They should disengage the autopilot and start controlling the aircraft's pitch using the control column and the "main electric trim", the FAA say. Pilots should also flip the aircraft's stabiliser trim switches to "cutout". Failing that, pilots should attempt to arrest downward pitch by physically holding the stabilizer trim wheel, the FAA adds"
FAA directive to airlines released in Nov last year about arresting trim runaways on the MAX

I think many pilots will deal with this issue alone fairly well, throw in a few other issues like speed mismatch etc or alt mismatch and all of a sudden the situation right after takeoff becomes very dire indeed and is going to require some serious focus
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Old 20th Mar 2019, 11:21
  #2125 (permalink)  
 
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Originally Posted by Octane
Perhaps the 3rd set of eyes in the first Lion Air incident spotted the trim wheels whirring away in the nose down direction and realised what was going on whilst in the accident aircraft the 2 crew in the mayhem didn't..
Maybe, he did, sitting further back and with less immediate issues... however, its reported he went back into the cabin to get a 737 Manual and went back into cabin... therein maybe lies the truth of the matter.. a 3rd crew member with more time on his hands.
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Old 20th Mar 2019, 11:33
  #2126 (permalink)  
 
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Lion Crew

It would certainly be a positive thing if any of the previous Lion Air flight crew/
supernumary crew could post impressions from that flight.

After lots of criticism on his site they are probably highly unmotivated to do that
and I don't blame them
but horse's mouth stuff is better than a lot of guess work
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Old 20th Mar 2019, 11:33
  #2127 (permalink)  
 
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EU, Canada to review Boeing software fixes themselves after Ethiopia Airlines crash

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Old 20th Mar 2019, 11:45
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Originally Posted by Sailvi767
The crew also would have been required to read the aircraft logbook and should have been fully aware of what happened on the previous flight and that it required a trim disconnect.
Have you taken the time to read the preliminary report?

One of the many serious post-flight delinquencies by the previous flight's Captain was his failure to properly document the problems encountered on his flight together with a full account of the remedial actions taken. There was no mention of the stick-shaker activation, there was no mention of having to run the Runway Stabilizer NNC and no mention of having to set the STAB TRIM switches to CUTOUT. The Captain limited his AFML write-up of defects to 'IAS and ALT Disagree shown after take off' and 'feel diff press light illuminate'. That was it!

His write up in the company's A-SHOR electronic reporting system was simply,

Airspeed unreliable and ALT disagree shown after takeoff, STS also running to the wrong direction, suspected because of speed difference, identified that CAPT instrument was unreliable and handover control to FO. Continue NNC of Airspeed Unreliable and ALT disagree. Decide to continue flying to CGK at FL280, landed safely runway 25L.
So the crew for the accident flight had no idea of the extent of the issues that had been encountered the night before nor how they had been handled. What they did know was that the previous flight had encountered Airspeed Unreliable and ALT DISAGREE problems, that they had encountered unusual trimming, and that they rectified those problems by running just those two relevant NNCs.

It appears that they did what you would have expected them to do. There's circumstantial evidence that the accident flight crew briefed for the possibility of encountering Airspeed Unreliable and ALT DISAGREE problems again, reviewed the Flight With Unreliable Airspeed tables and prepared a plan for dealing with the problems if they encountered them.

So maybe time to get off the accident crews' backs, huh?
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Old 20th Mar 2019, 12:32
  #2129 (permalink)  
 
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Does anyone know if MCAS was/is an MMEL/MEL item? One presumes it wasn't if crews didn't know it existed?
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Old 20th Mar 2019, 13:09
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Important article

Capt. "Sully" Sullenberger wrote an important article on MarketWatch.

To read just Google "Sully - Marketwatch"
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Old 20th Mar 2019, 13:16
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https://www.marketwatch.com/story/ca...aga-2019-03-19
Captain Sullenberger
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Old 20th Mar 2019, 13:17
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Originally Posted by gmx
That is an interesting point.

If the leaked log from the pre-crash LionAir flight is accurate, the captain noted "STS running reverse". It was a prosaic description, appearing to lack the detail and urgency that one would associate with a catastrophic nosedive only arrested due to the fortuitous circumstance of an off-duty 737 pilot sitting in the jump seat knowing the correct procedure.
But the dive was clearly not arrested by the runaway stab trim procedure - the traces clearly show it is recovered and mcas continues to operate until cut-out some time later.

Prelim report says that an entry was made on an electronic reporting system, including: "Airspeed unreliable and ALT disagree shown after takeoff, STS also running to the wrong direction, suspected because of speed difference". This is different to the maint log report, which didn't mention STS at all - it's clear they didn't think STS was the real problem, merely another symptom of what they reported in the log.

STS also trims intermittently, is stopped by pilot trimming, and if speeds are unreliable it's probably very reasonable to assume that STS is affected if the a/c is trimming itself weirdly. Particularly in the absence of any knowledge of MCAS and with no AOA disagree displayed.
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Old 20th Mar 2019, 13:32
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You only need know that you are getting uncommanded trim that is effecting controllability of the aircraft.
For that statement to be true in all cases....it would require exactly one response to remedy the un-commanded trimming it would seem.

Is that the case in the aircraft in question here?

Or are there several ways of dealing with various possible causes of the un-wanted trimming?
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Old 20th Mar 2019, 13:48
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Once you turn the autopilot OFF, the only thing moving the flying controls, including the THS, should be you.
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Old 20th Mar 2019, 14:17
  #2135 (permalink)  
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Originally Posted by Nomad2
Once you turn the autopilot OFF, the only thing moving the flying controls, including the THS, should be you.
Says who..?
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Old 20th Mar 2019, 14:35
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Lot of discussion on MCAS and associated issues, I'm not condoning Boeing's apparent quick fix but airlines and consumers have a degree of involvement too.
737 is by today's standards an old design, the NG was a comprehensive update but its still based on a 60's design.

If you look at the 757 which most of us thought would take over from the 737 it takes a greater payload further, higher and faster for a comparable or better fuel burn; Not seen much outside the States now but still heavily used by some major players for N. American routes.

Why choose an older design over newer, more efficient types? Conservatism and customer familiarity/confidence are my first thoughts, leading us to this moment.
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Old 20th Mar 2019, 14:45
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Originally Posted by Lake1952
I think it is a mistake to say that the tendency to pitch up with added thrust due to nacelle created lift is "inherently unstable." In hindsight, Boeing and its customers would have been better served by skipping MCAS, requiring some training in the pitch up tendency even if, God forbid, the flight characteristics required a new type rating. And it probably would not have actually required a new type rating anyway!
No, you cannot simply waive certification requirements on stability by saying you will provide some more training. And how have you arrived at the conclusion that training would do a better job than a small system that provides the required control forces at high angles of attack? This is a system that helps return the aircraft to its normal flight envelope when it already is at a high angle of attack. Typically this is a situation where something else has already gone wrong, and that almost always implies a high workload, where it is vastly preferable to have the airplane return to fully controlled flight by itself rather than relying on a task-saturated pilot to remember some bit of training highly specific to this type of aircraft.

Obviously, these kinds of assistive devices require a proper hazard assessment to be performed, including adequate assumptions about human behaviour, especially in a high-workload environment, which is exactly where this system is most likely to be active, and an analysis of worst-case consequences of single failures. Arguably that could have been done better in the case of MCAS.

On the whole, I'm sure you will find that fly-by-wire airliners generally have a far better safety record than conventionally controlled ones. That is not to say that it is only due to the computer-controlled flight controls, but also because FBW types are newer and incorporate other advances in safe design and systems reliability. But it is also clear that computer-assisted flight controls do not generally make flying less safe, QF72 notwithstanding. Case in point: The A320neo has had no accidents and perhaps one incident (tailstrike), despite being on the market somewhat longer and having almost twice as many airframes in service as the 737MAX.

Bernd
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Old 20th Mar 2019, 14:52
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Originally Posted by bill fly
It would certainly be a positive thing if any of the previous Lion Air flight crew/
supernumary crew could post impressions from that flight.

After lots of criticism on his site they are probably highly unmotivated to do that
and I don't blame them
but horse's mouth stuff is better than a lot of guess work
I havenít seen criticism of the crew. In fact Iím pushed to think of a crew that ďcaused ďĒ an accident. Most accidents are the result of crew actions resulting from poor training or inadequate training.
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Old 20th Mar 2019, 15:02
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This WSJ Article out today but I can't post the link yet, perhaps someone else can.
Inside U.S. Airlines' Decisions to Keep Flying the 737 MAX

Interesting quote from the article:
No problems had shown up, says Neil Raaz, American’s director of flight safety. “We just didn’t see the indications that told us our airplanes were unsafe, and frankly, we still haven’t,” says Mr. Raaz, who is also a Boeing 737 captain and has U.S. Navy and National Transportation Safety Board training in accident investigations.
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Old 20th Mar 2019, 15:05
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Originally Posted by bsieker
No, you cannot simply waive certification requirements on stability by saying you will provide some more training. And how have you arrived at the conclusion that training would do a better job than a small system that provides the required control forces at high angles of attack? This is a system that helps return the aircraft to its normal flight envelope when it already is at a high angle of attack. Typically this is a situation where something else has already gone wrong, and that almost always implies a high workload, where it is vastly preferable to have the airplane return to fully controlled flight by itself rather than relying on a task-saturated pilot to remember some bit of training highly specific to this type of aircraft.

Obviously, these kinds of assistive devices require a proper hazard assessment to be performed, including adequate assumptions about human behaviour, especially in a high-workload environment, which is exactly where this system is most likely to be active, and an analysis of worst-case consequences of single failures. Arguably that could have been done better in the case of MCAS.

On the whole, I'm sure you will find that fly-by-wire airliners generally have a far better safety record than conventionally controlled ones. That is not to say that it is only due to the computer-controlled flight controls, but also because FBW types are newer and incorporate other advances in safe design and systems reliability. But it is also clear that computer-assisted flight controls do not generally make flying less safe, QF72 notwithstanding. Case in point: The A320neo has had no accidents and perhaps one incident (tailstrike), despite being on the market somewhat longer and having almost twice as many airframes in service as the 737MAX.

Bernd
hi Bernd
this is a whole new arena- FBW versus conventional. In fact the argument is only kept alive by the 737 which is the only large jet NOT FBW. The argument is more Boeing v Airbus where newer Boeings look conventional = control yoke and throttles that actually move- ie ď it does what it says on the tinĒ versus joy sticks which donít move together and static thrust levers.
Airbus and Boeing both similar in incident rates over last few years. Iím also sure this has been covered at length in previous prunes.
I like the Boeing way - you can see what the other pilot is trying to do. And what the automatics are doing since the controls follow through on commands. There will be armies of pro Airbus guys who will disagree.
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