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-   -   Ethiopian airliner down in Africa (https://www.pprune.org/rumours-news/619272-ethiopian-airliner-down-africa.html)

Cows getting bigger 16th Mar 2019 20:02


Originally Posted by donal r james (Post 10420841)
The ET B787 fire in LHR? thought that was due to a ELT battery shorting out.

Indeed, poorly implemented risk assessments at design level. As for the firproof box and exhaust solution, one needs to ask the FAA whty they basically accepted that an airborne fire scenario was suddenly acceptable. (There’s a REALLY long thread somewhere about that).

PuraVidaTransport 16th Mar 2019 20:10

AvHerald reporting the CVR has been read out and the data given to theEthiopian authorities without being listened to by the French. The work on the FDR is ongoing.

derjodel 16th Mar 2019 20:11


Originally Posted by esoterex (Post 10420800)
What about the 2010 737 crash in Lebanon? Looking at that accident report it does not put ET in a good light.

You can‘t draw conclussions on cherry-picked data. This way you introduce bias to the sample and of course data confirms your bias!

that said, ET409 final report is a fascinating read. I‘m just going over it and what standa out is:
- captains behavior seems to indicate he was somehow incapacitated (eg slow and wrong reactions to bank angle); what‘s more, he complained he could not sleep due to evening meal! It could be he was totally zombied due to insomnia
- twice on cvr recording he‘s asking about „what‘s that“ to which FO doesnt even react... insomnia induced hallucinations? Report offers no explaination
- he hand flew which was against SOP for IMC

now for the interesting part:
- TO trim selection was wrong for unexplained reasons(??)
- period of 3” a trim up which resulted in an increase of pitch trim from 7.9 to 8.8 units and an airspeed of 196 Kts. That manual trim command was the last one commanded by the crew during the flight and resulted in the aircraft computer memorizing that speed as the one the crew wanted to maintain, despite the different speed selected on the MCP19.- AP could not be engaged due to column forces against trim
- toga was selected
- At the same time, as the speed started to increase beyond 195 Kts, the speed trim commanded a nose up trim input increasing the pitch trim from 8.2 to 9.3 units at 00:40:37, resulting in a further increase in the aircraft pitch up tendency. The crew did not take any action to re-trim the aircraft to the desired speed, so, once the nose down pressure was released on the control column, the aircraft pitch started to increase again and became close to 30° up

in essence, possibly very similar to mcas, but in reverse: sts remebered a certain speed and stalled the airplane trying to maintain it. With toga selected sts had to compensate plenty of power with trim.

Wow.

I don‘t know if last manual trim also sets target speed for mcas? In case of ET with full thrust, wouldn’t that set higher target sped with every manual up trim? And as soon as you pull up and reduce speed you’d get hit with more trim to get to the target speed? That certainly would escalate very quickly once speed starts building up and could explain why the crews could not handle the plane. But this could also be nonsense, I don’t know how the systems behave.

Cloud Cutter 16th Mar 2019 20:11


Originally Posted by reamer (Post 10420832)
If it turns out to be mcas for this flight loss and the stab trim switches are found to be in the on position then the pilots are 100% to blame for all those lost lives.

What an ignorant comment. From a systems perspective, if aircraft design results in a situation that is 100% reliant on crew to flick the stab trim switches off, in a time critical, startling, highly dynamic scenario, the fault is almost entirely with the design of the aircraft. I thought we'd moved on a bit from the 'blame the human at the end of the error chain' mentality, but clearly some among us still have some way to go.

cockpitvisit 16th Mar 2019 20:19

Question from an SLF: Is it normal that you can trim an aircraft so far that you could not counteract the trim with the yoke, or is it a special feature of the 737?

What's the point of having a trim range exceeding the elevator authority? Are there any situations where this is needed?

donal r james 16th Mar 2019 20:21

The ELT (Emergency Location Transmitter) is completely independent emergency equipment system. Nothing to do with the two main electrical system batteries that have ended up in a stainless steel fire proof box. The initial fix there was to remove the ELT or the battery.

A. Muse 16th Mar 2019 20:34


stainless steel fire proof box
Nothing is fire proof - it may be fire resisting but everything melts at some point. The point is, does a burning battery have the heat to melt stainless steel?

dozing4dollars 16th Mar 2019 20:39

Thought Experiment
 
Your lined up on the runway. All normal. Advance power. Liftoff. Now your initial climbing out. “STALL STALL” HORN STICK SHAKER

Firewall the throttles
Pitch to respect stick shaker
Look around. What’s going on?

So my question is what do you do?

???

Joejosh999 16th Mar 2019 20:39

I had wondered about a pitot issue given the IAS problems reported, and wondered at the chances of additional hardware failure w AoA vane tripping MCAS....

...but does this show that IAS Disagree can in fact be caused by the AoA failure?
https://hackaday.com/2019/03/14/mcas...-consequences/

So instead of pitot issue AND AoA issue we are back to all being caused by a bad alpha vane?

Cloud Cutter 16th Mar 2019 20:42


Originally Posted by cockpitvisit (Post 10420858)
Question from an SLF: Is it normal that you can trim an aircraft so far that you could not counteract the trim with the yoke, or is it a special feature of the 737?

What's the point of having a trim range exceeding the elevator authority? Are there any situations where this is needed?

That's essentially a function of pitch moment range (i.e. the extremes of nose-up and nose-down pitch moment), elevator effectiveness across the relevant speed range, and elevator force required to achieve full displacement throughout the speed range. As has been discussed ad nauseam, the pitch moment range in the 737 has expanded significantly as the engines have become more powerful and the thrust arm has lengthened (larger engines, thrust arm moved further below CG). Add to that the effect of moving the now quite impressively sized engine nacelles further forward just so they'll fit, which has the effect of reducing dynamic pitch stability in a high AoA situation, and you absolutely have the potential to find yourself in an area of the envelope where elevator control alone is not sufficient, particularly when you take into account the force required to move the elevator at high speeds.

As you've alluded to, the above is not an ideal situation, and one of the many reasons why it's not a good idea to hang on to common type certification by the skin of your teeth as you redesign an aircraft to within an inch of what's 'acceptable'. Now we'll likely see 'what's acceptable' being pulled back into line, leaving the 737 MAX sitting out there on it's own, essentially uncertifiable in it's current state. No doubt a quick fix will be rustled up, but it obviously won't fix the underlying issues.

TRey 16th Mar 2019 20:52


Originally Posted by Cloud Cutter (Post 10420852)
What an ignorant comment. From a systems perspective, if aircraft design results in a situation that is 100% reliant on crew to flick the stab trim switches off, in a time critical, startling, highly dynamic scenario, the fault is almost entirely with the design of the aircraft. I thought we'd moved on a bit from the 'blame the human at the end of the error chain' mentality, but clearly some among us still have some way to go.

Ignorant seems a little rough. Ultimately, the human has to be the one capture the errors, either by system design or induced. There are some inherently dangerous designs that require a crew to be the last defense. But I cant imagine a single MAX crew in the world that doesn't brief before takeoff...Hey, when the flaps come up and if that trim wheel starts a goin"...then shut those STAB switches OFF! And I wouldn't say MCAS is a design failure...works great, until it doesn't...kind of like my brother-in-law.

MPN11 16th Mar 2019 20:53

May I take a weekend moment to thank many contributors here for NOT disparaging those of us who are not 10+k hour Captains for their sympathetic and informative responses to some of our slightly obtuse or ill-informed questions? You are taking the subject forward, instead of just stifling discussion. Thank you to the Moderators as well ... a thankless task, as I know from ‘another place’.

StuntPilot 16th Mar 2019 21:00


Originally Posted by A. Muse (Post 10420871)
Nothing is fire proof - it may be fire resisting but everything melts at some point.

That is simply not true. Although the heat of a fire in theory has no limit (one can keep adding fuel) the combustion temperature is strictly limited by the chemical potential of the reactants. Any material that is physically and chemically stable above this temperature can contain the fire. Ceramics and refractory metals (amongst others) have no problems doing so.

reamer 16th Mar 2019 21:07

Every pilot of the 737 has known since the Lionair crash that the first thing to do in this situation is simply switch off the mcas by cutting off the stab trim switches.

dingy737 16th Mar 2019 21:07

Question: When MCAS is active, does the trim wheel on the flight deck turn? Or is the MCAS trim applied without the knowledge of the pilots, similar to Yaw damper operation without rudder pedal movement?

reamer 16th Mar 2019 21:08

The big trim wheel spins as normal. Can't be missed.

reamer 16th Mar 2019 21:13


Originally Posted by Cloud Cutter (Post 10420852)
What an ignorant comment. From a systems perspective, if aircraft design results in a situation that is 100% reliant on crew to flick the stab trim switches off, in a time critical, startling, highly dynamic scenario, the fault is almost entirely with the design of the aircraft. I thought we'd moved on a bit from the 'blame the human at the end of the error chain' mentality, but clearly some among us still have some way to go.

Well from a pilot perspective, If you know that a 737 was lost 6 months ago due to this faulty system,
and it happens again , and you have been told what to do if it does, and
you fail to do it, then who do you think is at fault? If you answer anything but the pilot, then I hope to never be your passenger.

Cloud Cutter 16th Mar 2019 21:16


Originally Posted by TRey (Post 10420892)
Ignorant seems a little rough. Ultimately, the human has to be the one capture the errors, either by system design or induced. There are some inherently dangerous designs that require a crew to be the last defense. But I cant imagine a single MAX crew in the world that doesn't brief before takeoff...Hey, when the flaps come up and if that trim wheel starts a goin"...then shut those STAB switches OFF! And I wouldn't say MCAS is a design failure...works great, until it doesn't...kind of like my brother-in-law.

Yes, it was a little rough - apologies to reamer. You get my point though - reamer was just saying what a heck of a lot of 737 pilots are also saying and thinking, and it was that mindset that I was commenting on, for which 'ignorant' seems a perfect word (meant objectively, without malice).


Originally Posted by reamer (Post 10420914)
Well from a pilot perspective, If you know that a 737 was lost 6 months ago due to this faulty system,
and it happens again , and you have been told what to do if it does, and
you fail to do it, then who do you think is at fault? If you answer anything but the pilot, then I hope to never be your passenger.

With all due respect, you miss my point. If an aircraft designer relies on flight crew to carryout an action that ends up being essentially impossible (or very, very difficult at certain phases of flight, given certain scenarios), that is a design flaw - no sense blaming flight crew for that! The fact that all Max pilots were clearly primed for this situation after Lion only emphasises my point - don't you think the crew would have be extremely well versed with what they were expected to do in that scenario? A little causal analysis goes a long way, rather than jumping to conclusions.

reamer 16th Mar 2019 21:18


Originally Posted by Cows getting bigger (Post 10420843)


Tosh. The manufacturer has produced a sub-standard product, pushing enhanced responsibility on aircrews. There are many layers of responsibility here, the first being Boeing’s insistence on polishing-off a 50+ year-old aircraft by adding bigger engines bringing questionable stability and mitigating it all with a poorly thought-through ‘safety system’ (MCAS).

See above.

reamer 16th Mar 2019 21:23


Originally Posted by Cloud Cutter (Post 10420916)
Yes, it was a little rough - apologies to reamer. You get my point though - reamer was just saying what a heck of a lot of 737 pilots are also saying and thinking, and it was that mindset that I was commenting on, for which 'ignorant' seems a perfect word (meant objectively, without malice).



With all due respect, you miss my point. If an aircraft designer relies on flight crew to carryout an action that ends up being essentially impossible (or very, very difficult at certain phases of flight, given certain scenarios), that is a design flaw - no sense blaming flight crew for that! The fact that all Max pilots were clearly primed for this situation after Lion only emphasises my point - don't you think the crew would have be extremely well versed with what they were expected to do in that scenario? A little causal analysis goes a long way, rather than jumping to conclusions.

Oh, the mindset of common sense and reason and responsibility for ones actions is it?


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