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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 11th Mar 2019, 18:54
  #421 (permalink)  
 
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Originally Posted by cncpc
My understanding is that MCAS is only operative with the AP off and flaps extended? Just putting the question out for clarification.
This page seems to have a good overview of the MCAS:

737 MAX - MCAS

Someone said it becomes active at 1000 feet AGL, not sure if this a player if you're trying to climb above 1000 with MCAS and/or AOA problems.
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Old 11th Mar 2019, 18:55
  #422 (permalink)  
 
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Thumbs up

Originally Posted by EDLB


snip ........... snip
We most likely know now with 20/20 hindsight, that the AD was not a sufficient reaction to prevent further fatalities.


a point to ponder far better than many of the last 24 hrs of posts.
If one assumes it is a known problem (LionAir type) then what part of the AD is not sufficient?

Is it the technical part or the compliance part?

When all is said and done we need to understand this question in order to un-ground fleets

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Old 11th Mar 2019, 19:00
  #423 (permalink)  
 
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Originally Posted by CONSO
Unfortunately- Boeing will most likely keep it proprietary such that perhaps- maybe- it will be an exhibit in one or more of the coming- existing lawsuits- even then it may well be supplied under a protective order and available in context only to the jury IF pressed. Otherwise a summary of standard procedure of xyz group checked by abc group and signed off by ccc senior manager. Ditto for FAA and other agencies. And having been determined to meet section - 75635-cvr-67.1834 of code fubar321.45 as amended was within the rules ..

The noise you hear is A** covers slamming closed...
LOL yes that FUBAR321.45 regulation is so hard to overcome!

Seriously I would welcome a Congressional hearing and make Boeing show itís laundry and have the arse-coverers toss each other under the bus. When your proprietary code starts killing people it needs to be examined.
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Old 11th Mar 2019, 19:00
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Originally Posted by SLFinAZ
According to the Reuters report 4 witnesses were specific to sound which is historically much more accurate and telling than sight. Not with regard to specifics but abnormality. It's common for individuals to do a "double take" specific to visual clues since you tend to need to
process and double check an anomaly but we respond much more decisively to aural clues.
If I've learned anything in life, it's not to jump to conclusions, least of all based on eyewitnesses. The CVR and FDR should answer most of the questions. Mine you I still can think of no good reason why with the technology now available internal and external video recording is not also captured on all new airframes.
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Old 11th Mar 2019, 19:01
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Originally Posted by extreme P
​​​​​
High angle of attack
Autopilot disengaged
Flaps are up
The kicker being, if I recall the LionAir mishap discussion, the AP disengages when the AoA goes pear shaped (or rather, the AoA signal to the system).
That linkage informs my understanding of the fix that Southwest went for.

(As I recall, we beat to death in various AF447 discussions (all now in the Tech Log forum) whether or not having an AoA gage for the pilots to refer to was a good idea or not. SW, it seems, has decided that it's a good idea at this point in time.

Last edited by Lonewolf_50; 11th Mar 2019 at 19:12.
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Old 11th Mar 2019, 19:04
  #426 (permalink)  
 
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Engineer here

1. Since those knobs to shutdown the mcas are same as sts breaker then sts trim will also turned off. While sts is more frequent needed for landing/takeoff. Right?

2.in normal flight/aoa vane is ok, it's hard to differentiate when mcas is working? Only different while flaps already up right, or deliberately automated pilot off while getting High angle pitch. Only just 5s trimming that iterates? It will ran rare right in stall regime right, or also running on the sharp banking?

3. Its not possible to turned off just mcas instead whole sts trim system?

4. Eth302 is the b37m with aoa sensor indicator like US airlines has or cheaper that doesn't have aoa sensor indicator like lion air has.




Last edited by Realbabilu; 11th Mar 2019 at 19:21.
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Old 11th Mar 2019, 19:12
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There are thousands of airlines operating millions of flights annually, many with substantial aircraft. And if what is written here is to be believed, many of these are lacking standards, training and ability. Is it just by the grace of God that we don't have planes dropping out of the sky daily? Or the beauty of technology?
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Old 11th Mar 2019, 19:16
  #428 (permalink)  
 
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Originally Posted by 42...
Not certified to stall? Hogwash, we just did full stall recoveries in the sim. Extreme buffet, wingrocking, 6000 plus vvi sinking stalls. This however was not a MAX sim.
Keep in mind that sims have very little fidelity in reproducing a actual fully stalled condition.
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Old 11th Mar 2019, 19:16
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Is it just by the grace of God that we don't have planes dropping out of the sky daily? Or the beauty of technology?
Yes.
Squinty, let's not undersell the hard lessons learned in the industry, over decades, that are procedural in nature and which include CRM and training, etc.
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Old 11th Mar 2019, 19:21
  #430 (permalink)  
 
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Originally Posted by golfyankeesierra


come on, these are guarded switches, not the usual switches for everyday use.
on a guarded switch the switch movement is the same as the guard movement. It is very natural.
The stabtrim cutout switches are no cause for concern.
Thanks to you and airbubba ,,, that clarifies that aspect.

My house was built for a guy who had lived in GCM: the light switches are all over the place!! Some up, some down, multi-gang defying logic, it’s taken me nearly 15 years to get my head round which does what and how. And inverting a multi-gang dual connection doesn’t resolve things!
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Old 11th Mar 2019, 19:22
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Originally Posted by golfyankeesierra


come on, these are guarded switches, not the usual switches for everyday use.
on a guarded switch the switch movement is the same as the guard movement. It is very natural.
The stabtrim cutout switches are no cause for concern.
Ever tried to switch on the emergency exit lights on a 737?
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Old 11th Mar 2019, 19:29
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Originally Posted by Vessbot
Yes. The scheme is, on any vertical surface (like the instrument panel, or a wall) up = on, same as any switch in the rest of the world. On any horizontal surface (center pedestal, or overhead) forward = on. For the center pedestal, the forward = on scheme elegantly matches what you're used to (toward the top of your eyeball = on). But I've always thought that that's a stupid application on the overhead, which gives the feeling of upside down switches since it reverses the "toward the top/bottom of your eyeball" relationship, and instead it should just be treated like a wall.

And the 737 seems to have very few switches in places that aren't the overhead, so the overhead upside-down scheme prevails. But the stab cut out switches are on a place where the normal (up = on) scheme is in place.
Ahh typical American. North America and aviation are about the only places where UP is on for a switch. Most other places in the world down is on.
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Old 11th Mar 2019, 19:29
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Originally Posted by Realbabilu
Engineer here

1. Since those knobs to shutdown the mcas are same as sts breaker then sts trim will also turned off. While sts is more frequent needed for landing/takeoff. Right?

2.in normal flight/aoa vane is ok, it's hard to differentiate when mcas is working? Only different while flaps already up right, or deliberately automated pilot off while getting High angle pitch. Only just 5s trimming that iterates? It will ran rare right in stall regime right, or also running on the sharp banking?

3. Its not possible to turned off just mcas instead whole sts trim system?

4. Eth302 is the b37m with aoa sensor indicator like US airlines has or cheaper that doesn't have aoa sensor indicator like lion air has.



The STS system trims for speed, and works against the pilot when it operates. It is not a system that helps the pilots to keep the aircraft in trim. You would not notice if it was disabled. Itís an annoying piece of kit and only installed for certification reasons.
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Old 11th Mar 2019, 19:31
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What I find interesting, is whenever MCAS is being discussed (re the Lion Air crash and possibly this one as more data comes to light), there are a lot of posts saying that if they’d just done the trim runaway checklist, everything would have been OK. Yes, probably. But what would have led them to that checklist? If you took off in a 737 MAX on a flight where nothing went wrong and you didn’t crash (rare, I know ) and manually flew the cleanup, would you get a bit of trim from MCAS as the last of the flap went in, making it something “normal” and “expected"?

If you had read all the manuals, then got a stall warning shortly after clean, you’d expect the MCAS to do a bit of trimming, yes? So “normal” behaviour? It’s also intermittent and you can trim back and forth yourself, so hardly a “runaway” in the traditional sense; in fact not in the sense of the QRH either, which describes a runaway stab as “continuous”.

So, unless you are prepared to do the runaway stabiliser drill every time you see the trim wheel moving and it wasn’t initiated by you (which would lead to lots of very short flights), how do you tell in a limited timeframe whether MCAS is trying to save your life or trying to kill you...?
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Old 11th Mar 2019, 19:31
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Question - is/are the AOA sensors in such a position that either or possibly one on the pilots side could suffer from ramp rash ?
Maybe someone with that window seat disco'd the sensor...

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Old 11th Mar 2019, 19:32
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Originally Posted by 42...
Not certified to stall? Hogwash, we just did full stall recoveries in the sim. Extreme buffet, wingrocking, 6000 plus vvi sinking stalls. This however was not a MAX sim.
Was the simulator certified for stalling? Most sims are only certified for approach to stall and do not have the stall data package.
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Old 11th Mar 2019, 19:33
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Originally Posted by ManaAdaSystem


Ever tried to switch on the emergency exit lights on a 737?




No, like you have disarmed them innumerable times. But the emergency function (lights on) is the same direction as the guard.
Still see no issue with the stab trim cutout switches..



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Old 11th Mar 2019, 19:33
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Originally Posted by Sailvi767


Keep in mind that sims have very little fidelity in reproducing a actual fully stalled condition.
Disagree, the 737 sim felt like a as fully stalled F15C at extreme AOA as I've felt, violent shaking would be a good description. Yet, controllable. So yes, the 737 is certified to full stall, with devices in place to avoid that condition. The MCAS is only designed to modify characteristics to make it more like the NG, not stop a stall, which apparently has gone horribly wrong.
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Old 11th Mar 2019, 19:42
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Originally Posted by calypso
You cannot be busy with ANYTHING else. Not with unreliable airspeed. AVIATE, NAVIGATE, COMMUNICATE.
From an outside perspective it would seem that both pilots trying to AVIATE at the same time causes more trouble than it solves.

So now we have to wait six months to see if the Max should be grounded, instead of having one pilot COMMUNICATE the problem in real-time. They presumably had the company frequency on one box, why not just flick the comms open and stream the dialogue back to base?
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Old 11th Mar 2019, 19:42
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Originally Posted by downdata


Even after knowing the DC10 had a design fault wrt to the cargo door, it didnt stop the ground crew of TK981 to not lock the damn cargo door that killed 300 odd people. There must have been tens of thousands of t/os and landings on the DC10 without incidents between AA96 and TK981.
That's rather unfair, the baggage handler in that case did what he had been told to do, close the door and press the lock motor button for a set time. He didn't read English and couldn't read the new notice stating to check the lock mechanism alignment marks through the peephole in the door. The person who had been trained on these new instructions was senior to him but was not present that day. This aircraft also had its door microswitch shimmed in the wrong direction, it showed closed on the FE's panel even with the locking mechanism in an unsafe condition.

No this doesn't relate to a 73 Max crash, but blaming the wrong party is never good.
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