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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 12th Mar 2019, 20:03
  #781 (permalink)  
 
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Originally Posted by silverstrata
Wrong on all counts.
a. The 737 is not a computer controlled aircraft by any stretch of the imagination. It is the original fly-by-wire aircraft (yup - 5mm steel cables).
b. The Indonesian, Ethiopian(?), A320, A340, and many other incidents demonstrate that the pilots were NOT able to be the last line of defence. Quite the reverse.
c. AF447 could easily have been saved by computer software. If Normal-law drops out because of input errors, the aircraft defaults to Alternate-law, which is a basic control system running on attitude and power. It would take Airbus a couple of years to knock up this new Alternate-law, which assumed no pilot assistance.
d. The Sioux DC10 crash was easily flown with a computer (just on engines, with no controls). They knocked up that new software inside a year.

Silver

And how many times did the pilots save the airplane from the automation?
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Old 12th Mar 2019, 20:05
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Originally Posted by ReturningVector
And don't forget that most accidents that have happened would also have happened if there were no pilots.
Really? Last year alone pilot errors in airliners contributed to almost 500 fatalities.

Also the case with Lion Air, that plane would have crashed without pilots as well, only sooner. And the day before, the pilots had even saved that plane from the failing automation.
A fully automated aircraft would probably detect the AOA-mismatch while still on ground, and would have no need for MCAS to begin with. 😉
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Old 12th Mar 2019, 20:10
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Originally Posted by KRUSTY 34
The FAA shouldn’t be anywhere near the investigation.
I fully agree!
While the NTSB is a great Organisation (the worldwide benchmark when it comes to flight safety) and beyond the slightest doubt, the FAA has presented themselves time and again mainly as a lobbyist for the industry. Safety does not appear to be anywhere near the top ten on their agenda. And that is nothing new. Sadly.
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Old 12th Mar 2019, 20:11
  #784 (permalink)  

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Originally Posted by The Bartender
Really? Last year alone pilot errors in airliners contributed to almost 500 fatalities.



A fully automated aircraft would probably detect the AOA-mismatch while still on ground, and would have no need for MCAS to begin with. 😉
You ever flown an airliner Bartender.?
Didn’t think so..
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Old 12th Mar 2019, 20:11
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Sort of...

MCD inspired by the brilliant crew handling of the Sioux City incident, using thrust vectors, then worked out a system they called “fly by fire” where the control inputs were sent tho the engine fcus instead of the flight controls. Visiting pilots were invited to try it in flight and apart from a little lag, were very impressed.
I don’t know whether the system was marketed, however.
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Old 12th Mar 2019, 20:22
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Originally Posted by oldoberon
FCENG

so you are 1000 feet and MCAS dials 2.5degrees nose down WHAT DO YOU DO?
1. First thing is pull the column to put in the between 5 to 8 degrees of airplane nose up elevator needed to offset the MCAS stabilizer increment.
2. Use manual pitch trim to re-establish trim to the point of not needing to hold column.
3. If stabilizer runs airplane nose down again, recognize it as inappropriate and arrest by using manual pitch trim to stop MCAS stabilizer motion and move stabilizer back to trimmed position. (No need to sit idly by and watch 10 seconds of stabilizer motion taking you away from trim go in when you have determined that is not appropriate.)
4. Call for PNF to toggle stabilizer cutout switches and discuss managing pitch trim via manual trim wheel for the balance of this flight.
5. Make sure that this event is squawked in a manner that assures:
- The source of the errant stabilizer motion is identified and corrected prior to the next flight
- The next crew to fly this bird knows full well what was encountered on this flight and what was done to work around it.
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Old 12th Mar 2019, 20:29
  #787 (permalink)  
 
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Originally Posted by FCeng84
While there is not yet sufficient information to draw a clear link between the ET accident that is the subject of this thread and MCAS I am deeply troubled by the amount of misinformation regarding MCAS that is being spread here. Reluctantly I offer the explanation below without any suggestion that this system contributed to the tragedy in Ethiopia this last weekend. The truth will be revealed by the recorder data and the full investigation. I strongly implore those who do not know MCAS details to stop providing incorrect information here or anywhere else. Posing questions is fine, but please do not state as fact that about which you are not sufficiently knowledgeable.

MCAS Operation Clarification

MCAS is triggered when all of the following are true:
A. Sensed AOA exceeds a flight condition based activation threshold
B. Flaps are fully retracted (i.e., up)
C. Autopilot is not engaged

When triggered, MCAS commands nose down stabilizer as a function of how much AOA has exceeded the activation threshold and the current Mach number. For large exceedence of the MCAS activation AOA threshold, MCAS will command 2.5 degrees of stabilizer at low Mach number but less than 1/3rd of that at cruise Mach number (gradual Mach number based schedule between). For a lesser exceedence of the MCAS activation AOA threshold the size of the stabilizer increment will be proportionally less. MCAS stabilizer command will be stopped immediately upon pilot activation of pitch trim. (Pilot trim input also serves as MCAS reset - see next paragraph.)

Once MCAS has commanded one increment of stabilizer motion, it will not command more until it has been reset. MCAS is reset if any of the following occur:
1. Pilot makes a manual trim command. (MCAS will not re-activate until there have been 5 continuous seconds without pilot trim command.)
2. AOA drops below MCAS activation threshold and MCAS has run stabilizer in the airplane nose up direction taking out the increment of airplane nose down command it inserted earlier.
3. Autopilot is engaged and then disengaged.

Without pilot trim input, MCAS will not run the stab more than one increment (up to 2.5 degrees) unless MCAS is reset via either 2 or 3 above.

Talk of MCAS running the stabilizer for 10 seconds, pausing for 5 seconds, and then running it again repeatedly without pilot trim input are patently incorrect.
So, in other words, much the same as has been said here already.
So MCAS activates, due to faulty AoA sensor reading.
Pilot resets the system by applying counter trim.
MCAS rolls again... (repeat, while airplane accelerates and finally MCAS wins...)

Why does MCAS run the stab? Why not offset the elevator?

Will MCAS also reset, if it is switched off and switched on again?

Why does MCAS not also read - for instance - vertical and horizontal speeds and their trends first, instead single-pointedly relying on the AoA reading and deciding the airplane is about to stall and start fu****g with the stab?
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Old 12th Mar 2019, 20:29
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That post suggests that using the electric trim button (presumably the most convenient practice) generates issues. Whereas, after toggling the stab off, the geriatric trim wheel solves all problems?

Oh, and using primary flying controls instead of autopilot settings, I assume?
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Old 12th Mar 2019, 20:34
  #789 (permalink)  
 
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Originally Posted by FCeng84
1. Pilot makes a manual trim command. (MCAS will not re-activate until there have been 5 continuous seconds without pilot trim command.)
Talk of MCAS running the stabilizer for 10 seconds, pausing for 5 seconds, and then running it again repeatedly without pilot trim input are patently incorrect.
Actually, this 'talk' is perfectly correct. When the MCAS system is activated erroneously, the pilot will inevitably make a trim input. And if your trim input is insufficient to counter the MCAS input, as was the case on the Indonesian, you rapidly end up with full nose down trim.

And I have to ask again, because nobody has answered - why would anyone invent a system that gives full nose-down trim? It goes against all aviation history and procedures. Remember the old adage - NEVER FLY WITH THE TRIMMER. And yet here is Boeing effectively using the trimmer as a primary flight control - deliberately placing the aircraft out of trim, instead of keeping it in trim.

That is why all other aircraft have stick-pushers, so you fly the stall with the primary flight controls, not the trimmer. The difference? Assisting the stall with the trimmer leaves you out of trim for the subsequent dive - with 60 kg of pressure on the stick, and 60 turns of the trim before you get back to something that is flyable. Conversely, when a stick pusher relents, you are still in trim, and can recover and fly away with ease. So why did Boeing chose such an absurd system for the 737-Max? Are Boeing really penny-pinching to such a degree? They should have taken a leaf out of the British Midland book - quote: "if you think safety is expensive, try having an accident..."

Silver
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Old 12th Mar 2019, 20:35
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Suppose MCAS isn't the CAUSE

Suppose MCAS isn't the CAUSE, but is also a VICTIM OF the root cause. If you feed MCAS defective inputs one result of that is that it will do what it was intended to do - it'll pitch down. Suppose whatever is mangling the MCAS inputs is also mangling the airspeed data displayed to the crew. In other words, the computing and indicating systems on the aircraft are displaying defective information which the crew and MCAS are acting upon. Troubleshooting MCAS in this situation won't get you much because MCAS isn't the CAUSE - it's an EFFECT of a fault elsewhere. I'd like to see the logic chain between the outdoor sensors and the displays and systems. I'll bet there are multiple computing boxes in that chain where defective air data can be produced *without detection* by the crew - or the MCAS.
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Old 12th Mar 2019, 20:40
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Just the one UK TUI MAX that didnt make it home , G-TUMF on extended leave down in Tenerife.
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Old 12th Mar 2019, 20:41
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Originally Posted by MPN11
That post suggests that using the electric trim button (presumably the most convenient practice) generates issues. Whereas, after toggling the stab off, the geriatric trim wheel solves all problems?

Oh, and using primary flying controls instead of autopilot settings, I assume?
Using the electric trim buttons but not fully trimming the airplane to offload column force can lead to progressive net stabilizer motion in the airplane nose down direction as appears to be the case with the last 30 seconds of the Lion Air event. Using the electric trim buttons to fully retrim to zero column force (Lion Air event prior to last minute) supports continued controlled flight. Given the choice between the former and the latter, I choose the latter. Given the choice between the latter and shutting down all electric stabilizer control I would choose to manage the stabilizer via the manual trim wheel for the rest of this flight.

You are correct about not having autopilot once the stabilizer is cutout. Without electric stabilizer control from the autopilot stabilizer offload logic, autopilot functionality cannot be provided.
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Old 12th Mar 2019, 20:45
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Originally Posted by FCeng84
1. First thing is pull the column to put in the between 5 to 8 degrees of airplane nose up elevator needed to offset the MCAS stabilizer increment.
2. Use manual pitch trim to re-establish trim to the point of not needing to hold column.
3. If stabilizer runs airplane nose down again, recognize it as inappropriate and arrest by using manual pitch trim to stop MCAS stabilizer motion and move stabilizer back to trimmed position. (No need to sit idly by and watch 10 seconds of stabilizer motion taking you away from trim go in when you have determined that is not appropriate.)
4. Call for PNF to toggle stabilizer cutout switches and discuss managing pitch trim via manual trim wheel for the balance of this flight.
5. Make sure that this event is squawked in a manner that assures:
- The source of the errant stabilizer motion is identified and corrected prior to the next flight
- The next crew to fly this bird knows full well what was encountered on this flight and what was done to work around it.
To play devil's advocate.

So on any occasion on climb after TO and this was to occur, this would be your modus operandi? Stick shaker or not? Low or erroneous ASI reading or not? Just pull against MCAS and tell PNF to start flicking switches? I know where you're coming from, but, unfortunately it's just not always as simple as the way you're portraying. At 1000ft you dont have much room to play with in the first place, which in itself adds pressure. Again, confirmation bias, people had commented earlier that "look out the window, you'll know if you're close to stall". Say for example this captain who had 8,000 hours of instruments reading correctly, the one time he gets put in a scary position he's meant to look out the window and say to his 200 hour FO "plane is wrong, at 1,000ft I can tell our speed is good". No, his confirmation bias will be, "we're about to stall, the readings must be right, what the f***??".
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Old 12th Mar 2019, 20:51
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Originally Posted by LiamNCL
Just the one UK TUI MAX that didnt make it home , G-TUMF on extended leave down in Tenerife.
And another TUI MAX was wildly circling Bologna just before the EASA cut off time at 1900z - seems to have difficulty finding someone to make a decision where to park the upcoming static display whilst en route from Egypt to Brussels

189 pax now have an Italian holiday extension FOC
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Old 12th Mar 2019, 20:53
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Originally Posted by FCeng84
For large exceedence of the MCAS activation AOA threshold, MCAS will command 2.5 degrees of stabilizer at low Mach number but less than 1/3rd of that at cruise Mach number (gradual Mach number based schedule between).
So you are saying that if you AoA sensor goes bananas right after takeoff (and you have not bought the “option” to see AoA vane displayed), then as mcas activates, you start fighting it - and as you have no time to reduce thrust you develop speed of 380kts while 2000f AGL, mcas will happily apply 2.5 degrees, because you are, after all, at low mach speed?


Or... your flaps got stuck so you are landing with flaps 0, you are on short final, hit a bird directly into AoA, mcas repeatedly applies 2.5 degrees trim while you are a few hundred feet AGL, because clearly that is safe at low mach numbers?

What could possibly go wrong?
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Old 12th Mar 2019, 20:54
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Originally Posted by FCeng84
While there is not yet sufficient information to draw a clear link between the ET accident that is the subject of this thread and MCAS I am deeply troubled by the amount of misinformation regarding MCAS that is being spread here. Reluctantly I offer the explanation below without any suggestion that this system contributed to the tragedy in Ethiopia this last weekend. The truth will be revealed by the recorder data and the full investigation. I strongly implore those who do not know MCAS details to stop providing incorrect information here or anywhere else. Posing questions is fine, but please do not state as fact that about which you are not sufficiently knowledgeable.

MCAS Operation Clarification

MCAS is triggered when all of the following are true:
A. Sensed AOA exceeds a flight condition based activation threshold
B. Flaps are fully retracted (i.e., up)
C. Autopilot is not engaged

When triggered, MCAS commands nose down stabilizer as a function of how much AOA has exceeded the activation threshold and the current Mach number. For large exceedence of the MCAS activation AOA threshold, MCAS will command 2.5 degrees of stabilizer at low Mach number but less than 1/3rd of that at cruise Mach number (gradual Mach number based schedule between). For a lesser exceedence of the MCAS activation AOA threshold the size of the stabilizer increment will be proportionally less. MCAS stabilizer command will be stopped immediately upon pilot activation of pitch trim. (Pilot trim input also serves as MCAS reset - see next paragraph.)

Once MCAS has commanded one increment of stabilizer motion, it will not command more until it has been reset. MCAS is reset if any of the following occur:
1. Pilot makes a manual trim command. (MCAS will not re-activate until there have been 5 continuous seconds without pilot trim command.)
2. AOA drops below MCAS activation threshold and MCAS has run stabilizer in the airplane nose up direction taking out the increment of airplane nose down command it inserted earlier.
3. Autopilot is engaged and then disengaged.

Without pilot trim input, MCAS will not run the stab more than one increment (up to 2.5 degrees) unless MCAS is reset via either 2 or 3 above.

Talk of MCAS running the stabilizer for 10 seconds, pausing for 5 seconds, and then running it again repeatedly without pilot trim input are patently incorrect.
Am in total agreement with above. However that which concerns me is " activation threshold ". How are these values set and what protections have been programmed into the software for errors and other failures, such as AoA malfunction and failure, A/P disengagement and flap/ slat retraction. What systems, oral and visual, are installed to alert crew of auto MCAS engagement. Perhaps those familiar with the system may enlighten us on this subject.
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Old 12th Mar 2019, 20:55
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Originally Posted by LiamNCL
Just the one UK TUI MAX that didnt make it home , G-TUMF on extended leave down in Tenerife.
It will likely position back to Luton shortly.
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Old 12th Mar 2019, 20:58
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Originally Posted by silverstrata
Actually, this 'talk' is perfectly correct. When the MCAS system is activated erroneously, the pilot will inevitably make a trim input. And if your trim input is insufficient to counter the MCAS input, as was the case on the Indonesian, you rapidly end up with full nose down trim.

And I have to ask again, because nobody has answered - why would anyone invent a system that gives full nose-down trim? It goes against all aviation history and procedures. Remember the old adage - NEVER FLY WITH THE TRIMMER. And yet here is Boeing effectively using the trimmer as a primary flight control - deliberately placing the aircraft out of trim, instead of keeping it in trim.

That is why all other aircraft have stick-pushers, so you fly the stall with the primary flight controls, not the trimmer. The difference? Assisting the stall with the trimmer leaves you out of trim for the subsequent dive - with 60 kg of pressure on the stick, and 60 turns of the trim before you get back to something that is flyable. Conversely, when a stick pusher relents, you are still in trim, and can recover and fly away with ease. So why did Boeing chose such an absurd system for the 737-Max? Are Boeing really penny-pinching to such a degree? They should have taken a leaf out of the British Midland book - quote: "if you think safety is expensive, try having an accident..."

Silver
Silver - Your comments above are all worthy of review and consideration. The 737 is not a fly-by-wire airplane and thus does not have an augmented elevator command when flying manually. Earlier models (pre-MAX) used electric stabilizer control to address speed stability (STS). This approach was expanded to address otherwise uncertifiable 737MAX Cm-alpha characteristics by driving the stabilizer through the MCAS function. MCAS underwent extensive analysis and testing prior to certification. An assumption that was made throughout was that if the crew did apply manual trim, they would not stop their manual trim inputs for 5 seconds or longer without having offloaded column forces to (or near) zero. As mentioned via earlier posts in this thread, modifications to MCAS have been developed and will be out to the fleet this spring to improve MCAS safety. One of the key factors is removing the assumption that the crew, having activated manual trim, will provide complete manual trim to zero column force.
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Old 12th Mar 2019, 20:59
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Originally Posted by SLFinAZ
The FO had an MPL not an ATPL, The program provides for 70 hours of actual flight time and 130 hours of simulator training. From an earlier post of a pilot who actually flew with ET he stated that most MPL holders had roughly 230 total hours before they were released to Line (vs. Training) captains.
Thank you.
Probably a discussion for "elsewhere", but MPL does seem to be a bit of a "short cut" affair.
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Old 12th Mar 2019, 21:03
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Originally Posted by 22/04
The wide range of views on here is something I applaud - rather I am concerned by some people who do not live in the real world - this one here.

MPLs are a fact of life- I fly EasyJet and Ryanair and the FOs often look like they should still be at school. Same on SpiceJet and Go-Air in India. I don't see them going away. The US seems to be out of step if anything by still insisting on more experience- I am surprised commercial pressure hasn't led to the same there.

Aeroplanes must be built such that they can be flown by these crews - safely operated all over the world. As I said yesterday, I am not sure certification bodies are doing their duty here.
No.

It is time for the Regulators and Airlines to realise that flying a jet isn't the simple task that they keep trying to delude themselves into believing, in the name of cost cutting. Hopefully this is the accident that is the turning point in refocusing training and money spent on pilot training.

Last edited by greenfields; 12th Mar 2019 at 23:05.
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