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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 12th Mar 2019, 03:21
  #561 (permalink)  
 
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Switch direction.

I recently transitioned to an Airbus from an old British machine. It wasn’t until some months into flying the bus that I realised the switch directions were opposite to what I was supposedly used to. You see, what I’d been doing is this, if I knew something was off and I wanted to turn it on, I would locate the appropriate switch and move it to its other position. I would then check that what was once off was now on and I would carry on. I do something similar with light switches in a room, if the lights are off, I locate a light switch and move it to its opposite position, I then check that the lights have come on. If they haven’t, I look for another light switch and repeat the procedure .

I find it very hard to believe that someone could be confused by switch direction. If the trims need to be cutout, you lift the guard and move the switch. Right? You don’t lift the guard, observe the switch in a particular position, mistake that position for OFF, and then assume that somehow the switch was already off! Talk about overthinking.
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Old 12th Mar 2019, 03:23
  #562 (permalink)  
 
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Fiji Airways have not grounded their two - I am about to board one
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Old 12th Mar 2019, 03:25
  #563 (permalink)  
 
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Aerolíneas Argentinas has suspended their MAX operations, currently 5 in the fleet.
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Old 12th Mar 2019, 03:32
  #564 (permalink)  
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Originally Posted by oldoberon View Post
lancs said " From the Lion Air thread, I believe MCAS cycles between the 2 AOAs between each flight..""..

If the system uses 1 &2 on alternate flights both are wired in, I would think it is relatively simple to put a 1-2 switch in the cockpit but it is only active when the red light / HUD shows there is a difference, that could possibly immediately allow crew to rectify problem

Oldoberon
There is no information in the current B738M AOM that tells crews that the "MCAS cycles between the left AoA and the right AoA sensor". What is the source for the above statement?
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Old 12th Mar 2019, 03:37
  #565 (permalink)  
 
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In Boeing's Nov 6 2018 (FAA as of that date unapproved) bulletin, p. 25, Skyjob's post#496, no mention is made anywhere by Boeing of MCAS.

In Post #511, the clear graphic from Air Current states that MCAS activates when 'steeply turning'.
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Old 12th Mar 2019, 03:42
  #566 (permalink)  
 
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Originally Posted by oldoberon View Post
lancs said " From the Lion Air thread, I believe MCAS cycles between the 2 AOAs between each flight..""..

If the system uses 1 &2 on alternate flights both are wired in, I would think it is relatively simple to put a 1-2 switch in the cockpit but it is only active when the red light / HUD shows there is a difference, that could possibly immediately allow crew to rectify problem
Boeing's software update for the 737 MAX should address the AOA-1 vs -2 inconsistency (assuming that is its scope), obviating the need for physical switches. That also seems a good stage to include reasonability checks on AOA data before triggering MCAS.
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Old 12th Mar 2019, 03:46
  #567 (permalink)  
 
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Originally Posted by jolihokistix View Post
In Boeing's Nov 6 2018 (FAA as of that date unapproved) bulletin, p. 25, Skyjob's post#496, no mention is made anywhere by Boeing of MCAS.

In Post #511, the clear graphic from Air Current states that MCAS activates when 'steeply turning'.
But there is more for example post 427 also applies and AirCurrent does a lot of interpretation



MCAS activates automatically when all of the following conditions are met:
High angle of attack ( could be high bank angle for example )
Autopilot disengaged
Flaps are up
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Old 12th Mar 2019, 03:52
  #568 (permalink)  
 
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Originally Posted by MemberBerry View Post
Correct, except the AOA disagree warning light is an optional extra on the 737 MAX, so not every 737 has it.

For example the Lion Air 737 MAX didn't have either of those options installed, so it would have been difficult for the crew to determine they had an AOA disagree situation or not.
Thanks, edited my post accordingly
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Old 12th Mar 2019, 03:54
  #569 (permalink)  
 
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Straits Times says SAL will ground.

https://www.straitstimes.com/singapo...airlines-crash
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Old 12th Mar 2019, 04:00
  #570 (permalink)  
 
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Originally Posted by PJ2 View Post
There is no information in the current B738M AOM that tells crews that the "MCAS cycles between the left AoA and the right AoA sensor". What is the source for the above statement?
I'm not the person you replied to but I tried to find some sources for it, I could only find an article titled "737 FCC Pitch Axis Augmentation - Command Integrity Mandate for Dual Channel, Fail-Safe" on satcom guru.

They assume that's the case because that's how the similar speed trim and mach trim functions work, the functions are controlled by the active FCC, and the active FCC changes when the plane lands, and reverts to one the left side after a power cycle.
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Old 12th Mar 2019, 04:01
  #571 (permalink)  
 
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Originally Posted by OldnGrounded View Post
Yes. In the discussions of both crashes, it has been striking that there has been so much confusion and disagreement about the operation of MCAS, much of it on the part of transport-experienced professional aviators. And no matter how much relevant material I've read, or how often I've re-read it, some things still aren't clear. For instance, some descriptions of the "system" (software patch) suggest that it is necessary for the MAX to be in a high bank for it to be activated. That doesn't make sense and it doesn't seem to have been the case in the Lion Air or the ET crashes (if the ET incident was MCAS-related), but it pops up repeatedly in lists and graphics.

Common sense and basic principles of human engineering dictate that a system or application that creates this much uncertainty and confusion, even among experts in a discipline, is begging for redesign.
The Lion Air crash happened presumably because of a faulty AOA indicator. I guess the Boeing statement about needing high bank is related to needing a high AOA (so low speed and high bank) to activate MCAS as opposed to a separate AOB input into MCAS. This further proves you are totally right about the confusion and disagreement.
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Old 12th Mar 2019, 04:01
  #572 (permalink)  
 
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AoA sensor switch for MCAS
_________________________
Salute PJ2 !!

The alternating AoA sensor scheme was fully eplained in the 610 thread and apparently was defeated for the 610 flight leg due to disconnecting things and putting in new things. Don't have time now to give you a specific post, but it is all there or on the tech log companion.

Gums sends...
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Old 12th Mar 2019, 04:15
  #573 (permalink)  
 
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To board the MAX, or not to board - That is the question

We are all keenly interested in what the FDR and CVR will show from this second accident.

Either they will show:
  1. a similar scenario as Lion or
  2. something different.
Barring something out of control by the crew and manufacturer, neither outcome will reflect well on the MAX.

The 37 has enjoyed an extraordinary run of success since its inauguration, but the latest engineering efforts seem to have pushed an initially robust and exemplary design into fragile behavior .
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Old 12th Mar 2019, 04:21
  #574 (permalink)  
 
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Originally Posted by JumpJumpJump View Post

737 max fleet grounded by Gol in Brazil.

They use their Max fleet for direct flights from Brazil to Florida.... Routes suspended, though imagine that they will be frantically working out how to honour current schedule with a fuel stop added in either the north of Brazil or the Caribbean
That's surprising since Brazil's certifying authority differed with others and required training on the MCAS system. What that training was and whether it was a pencil whip might explain their grounding.
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Old 12th Mar 2019, 04:22
  #575 (permalink)  
 
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Gotta agree!

In great VMC conditions - as reported - even the very worst of pilots should surely be able to maintain some semblance of the old Straight and Level.

Seems inconceivable to me that even if this Max had the same airspeed/attitude problems as the last one that crashed, the pilots couldn't have controlled it?

Something else going gone here I suspect!

A bad start to 2019!
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Old 12th Mar 2019, 04:27
  #576 (permalink)  
 
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Clearly the MCAS situation - even if this accident doesn't turn out to be rooted in MCAS - is a strong indicator.
Agreed. Aerodynamic problems have been buffered by computerized controls at least since OXCART, which experienced lopsided flameouts at close to Mach 3 because the pilots were unable to manually adjust the intake cones with adequate precision. It was a fight to get the test pilots to agree to the automation at that time, even though a couple had been lost.

Now, 60 years later, we seem to have turned 180 degrees in our thinking. As little as I understand MCAS, it is clear, at least to me, that it is a computer controlled solution to aerodynamic instability inherent in the design.

While computerized aerodynamic stabilization of inherently unstable new designs may be the trajectory of future, to apply it as a fix as we push 50 year old designs to new limits may prove to be a mistake.
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Old 12th Mar 2019, 04:27
  #577 (permalink)  
 
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Originally Posted by Buster15 View Post
Easily the most sensible and correct post I have read so far.
Speculation is just that. All will be revealed in good time.
And how long will that take and possibly how many more MAX's will crash (or nearly do so)? I would guess 2 or 3 years for the publication of an Ethipian Accident Report, so should we just sit on our hands and wait patiently? Of course not. Humans are curious by their nature and this thread proves that. The quicker the CVR and DFDR are downloaded and we know more, the better.

Without reading 500 odd posts, do we know who was PF? The experienced Captain or the inexperienced Co-PIlot? Steep expereince difference don't you think?
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Old 12th Mar 2019, 04:30
  #578 (permalink)  
 
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Interesting details/analysis by a control guru which **may** help explanation of which sensor does what and how

https://www.satcom.guru/2018/11/737-...n-command.html

Obviously put together after LionAir . .

Peter was Boeing avionics supervisor for 767 and 747-400 data link recording, data link reporting, and satellite communications. He was an FAA designated engineering representative (DER) for ACARS, satellite communications, DFDAU, DFDR, ACMS and printers. Peter was lead engineer for Thrust Management System (757, 767, 747-400), also supervisor for satellite communications for 777, and was manager of terminal-area projects (GLS, MLS, enhanced vision).
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Old 12th Mar 2019, 04:41
  #579 (permalink)  
 
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The crew reported problems with air speed indications. Does that invalidate the reported 383kt speed?
It does seem a high speed for less than 6 minutes after takeoff and at low altitude. Is it even credible?
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Old 12th Mar 2019, 04:43
  #580 (permalink)  
 
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Originally Posted by CONSO View Post
Interesting details/analysis by a control guru which **may** help explanation of which sensor does what and how
Peter made a few posts here a couple of years ago but I think someone didn't like his ADS-B analysis.
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