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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 11th Mar 2019, 21:40
  #481 (permalink)  
 
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Originally Posted by positiverate20
More like, "FO, keep an eye on your AoA and ASI and cross-check against mine "
And how does that help with an aircraft thats unstable in pitch and where the stab trim is intermittently trying to fly you in to the ground ?
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Old 11th Mar 2019, 21:41
  #482 (permalink)  
 
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Originally Posted by extreme P
​​​​​​MCAS activates automatically when all of the following conditions are met:
High angle of attack
Autopilot disengaged
Flaps are up
Worth adding that any design criteria is capable of failure, or operating outside design parameters.
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Old 11th Mar 2019, 21:52
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Originally Posted by rmac2
The key phrase is "along the lines of" , as apparently Boeing preferred not to admit to the possibility, let alone produce a procedure for it. In the absence of any guidance, what would be the quickest way to inhibit the MCAS system under pressure ? I suspect it would be to reproduce a configuration where it is inactive ?
How about switching it off?
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Old 11th Mar 2019, 21:54
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Originally Posted by OPENDOOR
Read what excrab said;
Well, I did.

10 degrees/80% with flap extended, 4 degrees/75% clean. At low altitudes you climb and at high levels descend slightly...
And he is wrong, that is why I responded....

At low airspeed you descend and accelerate. At high airspeed you climb and decelerate.
What is your point exactly?
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Old 11th Mar 2019, 21:54
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Originally Posted by GotTheTshirt
Is there some logic in having a couple of switches operating in the opposite sense to the rest ??
That worried me too - especially when someone replied, implying that 'all 737 pilots know about these switches' - as if that made it safe. Oh please - surely this is Engineering Human Factors basics - that is a way to guarantee some poor sap will get it wrong. Unless there is some overriding reason why they MUST be the other way round, normal modern engineering thinking says don't do it = recipe for a mistake.
737 experts - please tell us that Boeing didn't do that - or if they did, can anyone explain or justify it?
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Old 11th Mar 2019, 21:55
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Old 11th Mar 2019, 21:57
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Originally Posted by rmac2
The key phrase is "along the lines of" , as apparently Boeing preferred not to admit to the possibility, let alone produce a procedure for it. In the absence of any guidance, what would be the quickest way to inhibit the MCAS system under pressure ? I suspect it would be to reproduce a configuration where it is inactive ?
You realize that that's what the QRH and memory items are for?
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Old 11th Mar 2019, 22:03
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Isn't the procedure something more like "if the trim automation is trying to kill us we will switch it off, grab the trim wheel if necessary, then continue to trim manually. This we know from memory?" The only difference is in recognizing the insidious hand of MCAS.

One question though. IIRC the failures in the Lionair incident also messed with the elevator feel system. How would that impact your ability to trim?
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Old 11th Mar 2019, 22:03
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Originally Posted by ManaAdaSystem


How about switching it off?
Identifying and operating the switches promptly while trying to fly the aircraft under pressure seems to be a problem. Reducing power and setting flap 1 can be done almost instantly.
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Old 11th Mar 2019, 22:08
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Originally Posted by rmac2
Identifying and operating the switches promptly while trying to fly the aircraft under pressure seems to be a problem. Reducing power and setting flap 1 can be done almost instantly.
You do know there are two pilots in the cockpit?
No, you follow Boeing procedures. You can read them a few posts above this one.
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Old 11th Mar 2019, 22:11
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Switch direction

Trident up on
VC 10 down on
DC9 below windshield up on; above windshield down on.
my first three aircraft.
light switches England down on inside of room.
light switches Ireland down on outside of room.
light switches in Bed and breakfast in Ghent up on outside the room..set a bathrobe alight in the loo after a heavy night out.
only got it wrong once in heavy icing on a dark and dirty night when I switched the engine anti icing off instead of on...and got away with it (switched it back on one at a time with a delay just in case).
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Old 11th Mar 2019, 22:13
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Originally Posted by Intrance
They are though. Excluding some lights that can be turned on or off from multiple locations, light switches throughout all the houses and apartments I have lived so far (also Western and Eastern Europe) have been down for on.

It's a bit of a silly thing to argue about though. The type that I fly has the basic logic that everything pointing forward means normal ops. "Down" is then usually reserved for AUTO instead of ON, but same difference. I thought the larger issue with switches regarding 737 MAX is that they (the cut-off switches) function in the opposite way from the 737 NG. Not really any point dragging in regular light switches if we are talking about a manufacturers cockpit philosophy.
Based on multiple replies about this, I stand corrected. I have to say I'm shocked, but, well, learning has occurred. I would have thought this to be as much as a universal as driving on the right ha.... wait!

The reason I'm going on about light switches in rooms (as it turns out, incorrectly) is exploring the pre-existing human factors universal (or not) scheme that that part of aircraft ergonomics is based on. So the up=on scheme is restricted in scope to aircraft, and excludes overhead panels. But to get back to where this branch of the discussion started, the MAX stab cutout switches aren't reversed from previous 737's. Their names are relabeled from "MAIN ELECT" and "AUTOPILOT" to "PRI" and "B/U" but they're all "NORMAL" up and "CUT OUT" down.

http://www.airlinereporter.com/wp-co...light-Deck.jpg
https://s3.amazonaws.com/dsg.files.a...9/Edwilson.jpg

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Old 11th Mar 2019, 22:13
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Originally Posted by rmac2
Identifying and operating the switches promptly while trying to fly the aircraft under pressure seems to be a problem. Reducing power and setting flap 1 can be done almost instantly.
All I'm saying is, if in the exact conditions in which you speak, if stick shaker triggered, if either your ASI or AoA in front of you is showing something abnormal, then how can you instantly confirm it's an MCAS error in those circumstances? So, given that scenario, how can you automatically set flap one and reduce power?

MCAS is not and cannot be 100% wrong all the time, so why assume that is the problem if you're thrown into that scenario?

Last edited by positiverate20; 11th Mar 2019 at 23:11.
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Old 11th Mar 2019, 22:14
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Originally Posted by ManaAdaSystem


You do know there are two pilots in the cockpit?
No, you follow Boeing procedures. You can read them a few posts above this one.
The procedures that were rushed out after Lionair and didnt appear to help either pilot in the cockpit in this case ?
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Old 11th Mar 2019, 22:19
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Originally Posted by positiverate20
All I'm saying is, if in the exact conditions in which you speak, if stick shaker triggered, if either your ASI or AoA indicator in front of you is showing something abnormal, then how can you instantly confirm it's an MCAS error in those circumstances? So, given that scenario, how can you automatically set flap one and reduce power?

MCAS is not and cannot be 100% wrong all the time, so why assume that is the problem if you're thrown into that scenario?
Its a fair point. And a clear AOA indication will grant further cognition of the condition. However a trim system that repeatedly trys to shove the nose in to the deck despite the crews efforts to trim back to level flight and cumulatively builds up forces that quickly require two sets of hands pulling on the control column might be the clue that MCAS is trying to kill you ?
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Old 11th Mar 2019, 22:23
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Originally Posted by blind pew
Trident up on
VC 10 down on
DC9 below windshield up on; above windshield down on.
my first three aircraft.
light switches England down on inside of room.
light switches Ireland down on outside of room.
light switches in Bed and breakfast in Ghent up on outside the room..set a bathrobe alight in the loo after a heavy night out.
only got it wrong once in heavy icing on a dark and dirty night when I switched the engine anti icing off instead of on...and got away with it (switched it back on one at a time with a delay just in case).
For clarity it was an option on Boeings (might be 737 only) to have it either way.

I've flown ex Lufthansa 737s one day and ex Ansett the next where switches operated in the opposite sense. Didn't take much getting used to.
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Old 11th Mar 2019, 22:24
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Originally Posted by rmac2
The procedures that were rushed out after Lionair and didnt appear to help either pilot in the cockpit in this case ?
Nobody knows what caused this crash, and nobody knows what actions they did.
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Old 11th Mar 2019, 22:25
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In the UK:
While the universal standard for light and power/socket switches is down for on, you can easily get three pole bathroom "run on" fan isolator switches in both configurations. Ie those which have up as off and those which have down as off.
Additionally the standard for items in consumer units (house fuse boards) being circuit breakers/MCBs, Rcbo's, and RCD units is up for on.
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Old 11th Mar 2019, 22:28
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Originally Posted by rmac2
Its a fair point. And a clear AOA indication will grant further cognition of the condition. However a trim system that repeatedly trys to shove the nose in to the deck despite the crews efforts to trim back to level flight and cumulatively builds up forces that quickly require two sets of hands pulling on the control column might be the clue that MCAS is trying to kill you ?
As a non-737 pilot who has followed the discussion here since Lion Air fairly closely, it seems to me that by far, the surer bet in response to the trim going haywire is to shut off the trim via the switches provided in a prominent place, that will prevent ANY of the hodge podge software modules from moving the trim, than to invent your own procedure that attempts to outsmart the system logic and prevent just ONE of those modules from moving the trim, that you have primed yourself to think about due to the last crash. What if it's not the MCAS, but the STS? or the next secret patch that Boeing will reveal next year? Or simple classic runaway trim?

Cast my vote with the "follow the procedure" crowd.
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Old 11th Mar 2019, 22:31
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Originally Posted by Chesty Morgan
For clarity it was an option on Boeings (might be 737 only) to have it either way.

I've flown ex Lufthansa 737s one day and ex Ansett the next where switches operated in the opposite sense. Didn't take much getting used to.
To be clear, which switches are you talking about? The stab cutouts? The overhead?
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