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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 21st Mar 2019, 23:56
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Originally Posted by TriStar_drvr
No. At rotation flaps would be extended. MCAS does not engage with the flaps extended.
​​​​​​.. .and so.. our game crew retract the flaps, cos they are approaching Vfe in the aircraft config but the light is on? What happens next?
How the heck they ever got this through part 14cfr chapter 25 certification reliant on only 1 sensor?

Seems to me, in the rush to fix one certification issue, someone forgot the rest.

Ttfn
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Old 22nd Mar 2019, 00:11
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I have flown with AoA indicators on various corporate jets.
I found them extremely useful as a conformation for approach and departure speeds.
Why they are not standard on larger jets is puzzling.

If MCAS was a bodge, how many other bodges were found acceptable
Stick pushers, stick shakers, Stall Avoidance System on SA227 aircraft, etc..

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Old 22nd Mar 2019, 00:15
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Originally Posted by PaxBritannica
I can't see that a quick fix for MCAS is going to reassure the travelling public, ie me. If MCAS was a bodge, how many other bodges were found acceptable? If this was the only place in the design where engineers were asked to take a 'small' risk, I suspect whispers would have gotten around long before the plane flew. Therefore, it's likely that it was just one of many other design 'solutions' where the idea of tolerable risk was normalised.

No software patch will fix systemic management hubris.
It is amazing the amount of Boeing bashing on this forum. Boeing has made tens of thousands of safe & efficient airliners for more than half a century & that's why there are more Boeings than anything else. Every airplane design is a compromise that needs to be tweaked in one way or another to meet certification requirements. This process takes many months & involves much actual test flying. The much maligned MCAS was a tweak to meet an obscure certification requirement that was probably never going to be encountered in the life of the airplane. A lot of effort over decades has gone into making the aircraft as safe & foolproof in operation as possible. But, how do you design for an airline that flies an aircraft for three days with unreliable airspeed, maintenance that then compounds the problem with a bad AOA installation, & flight crews that still try to complete the flight with a continuous stick shaker? We don't know yet about Ethiopian, but if it was the same malfunction after all the warnings & publicity worldwide from Lion Air, then that is the height of incompetence.
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Old 22nd Mar 2019, 00:18
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Originally Posted by gums
Salute!
---snip---
I am trying to follow the ROE for our forum, but it's getting hard. I do not mean to diminish the length and breadth of experience that many pilots here have contributed to the discussion. But somethimes I get a little testy.

My fear is that some lurking here will think that we lost two planes and 300 passengers because incompetent crews did not simply turn off two switches within seconds of raising flaps at normal altitude and speed with the stall warning system telling them they were stalling and their airspeed was FUBAR.

The primary contributing factor to loss of control in the Lion crash and likely the Ethiopian one ,is gonna be the MCAS and its implementatio without fairly documenting it for the crews and not considering its activation at a corner of the envelope it was not intended for.

Gums...
Gums,

Mostly everyone here who is *not* a pilot realizes that the rushed certification of the Max is the real issue.

AFAIK nobody except Boeing lawyers and maybe the families is going to lay the blame on those pilots. Anyone, pilot or not, who reads the details of MCAS spooling up time and again in those cockpits thinks "there but for the grace of God go I".

But there is one interesting question though which is why those who survived such MCAS incidents prior to the Lion Air crash did not document them and raise a stink. Was it because they thought they had made an operational mistake?

Edmund
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Old 22nd Mar 2019, 00:41
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QF72 - A330

Running through TiVo tonight I came across the Air Disaster documentary on QF72. It's an A330 but at a high-level there is a lot in common with these recent tragedies.

https://www.smithsonianchannel.com/s...ll/802/3467449
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Old 22nd Mar 2019, 00:42
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I cant see any foreign regulatory authority allowing the Max into its airspace without an extensive modification of the stall avoidance system and an in-depth training program for Pilots and engineers. A separate type rating covering the Max, rather than relying on a current B737 rating is a real possibility. A new type certificate might also be on the cards as well.

After two disasters, no authority is going to sign off on a solution unless its iron clad and well in excess of whats required, a software update isnt going to be enough. No pilot will be flying a Max until hes demonstrated proficiency in dealing with any possible MCAS failures a simulator.

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Old 22nd Mar 2019, 00:45
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Originally Posted by BobM2
It is amazing the amount of Boeing bashing on this forum. Boeing has made tens of thousands of safe & efficient airliners for more than half a century & that's why there are more Boeings than anything else. Every airplane design is a compromise that needs to be tweaked in one way or another to meet certification requirements. This process takes many months & involves much actual test flying. The much maligned MCAS was a tweak to meet an obscure certification requirement that was probably never going to be encountered in the life of the airplane. A lot of effort over decades has gone into making the aircraft as safe & foolproof in operation as possible. But, how do you design for an airline that flies an aircraft for three days with unreliable airspeed, maintenance that then compounds the problem with a bad AOA installation, & flight crews that still try to complete the flight with a continuous stick shaker? We don't know yet about Ethiopian, but if it was the same malfunction after all the warnings & publicity worldwide from Lion Air, then that is the height of incompetence.
Yes, though that Bob is why you as a manufacturer should Tell them what the heck you've done to the stab trim circuit... which it sounds ominously like was poorly or undocumented. Nor we are told, was much if anything made of it as a 'difference' feature in any training (?).

I've a rare option Ford Focus Ghia without ABS brakes, which i hate (ABS that is)...
When I maybe have to buy one with ABS I'd hope the Driver's Handbook actually mentioned the fact !
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Old 22nd Mar 2019, 01:12
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Originally Posted by Alchad

It seems to be accepted that there are such similarities between the Indonesian and the Ethiopian crashes that – I suspect – a lot of people are assuming the cause of the accidents will also be similar. However, one difference between the two crashes which doesn’t appear to have aroused all that much speculation, at least as far as I can determine, is the fact that the Ethiopian 737 only managed to get to perhaps 1000 feet (according to Flightradar24), whereas the Indonesian 737 appeared to achieve 5000 feet and the pilots consciously settled for that altitude.

This is where my non- aircraft background becomes apparent and the reason for my question; which is basically what caused ET 302 to be unable to get above 1000 feet?


Minimum flap retraction altitude for B737 is 400 ft so possible MCAS-activation at low altitude.

Also there seems to be an assumption that the MCAS would bug them continuously after that unless they switched trim off. In the LionAir crash prel report a difference of 20 deg throughout the flight and stick shaker active for most of the rest of the flight. I e there seems to be a systematic error in one of the AoA sensors that would only activate shaker when they flew with an actual AoA above a certain level. Same would then hold true for MCAS-activation.

With just the "right" systematic error in one of the AoA-sensors ET302 could have been perfectly trimmable flying at constant altitude with AoA below the threshold. As soon as they tried to ascend increasing true AoA to proper MCAS-activation angle minus systematic offset they would have been "pushed down" but could have trimmed out again. So they are in a "perfectly good airplane" as long as they zoom along at breakneck speeds at a constant altitude above sea level. If ground level (above sea level) increases they would be destined to meet with terra firma sooner or later...unless they used the elevator...and got hammered by MCAS again.

And for the complaints about their speeding: Thrust reduction? No go. You'd sink unless you increased AoA above the threshold...and got hammered again.



Last edited by RUTUS; 22nd Mar 2019 at 01:41.
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Old 22nd Mar 2019, 01:23
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Originally Posted by edmundronald
Gums,


But there is one interesting question though which is why those who survived such MCAS incidents prior to the Lion Air crash did not document them and raise a stink. Was it because they thought they had made an operational mistake?

Edmund
Nobody has reported a MCAS event prior to Lion Air. Where did you get such a story?
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Old 22nd Mar 2019, 01:37
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Originally Posted by PaxBritannica
I can't see that a quick fix for MCAS is going to reassure the travelling public, ie me. If MCAS was a bodge, how many other bodges were found acceptable? If this was the only place in the design where engineers were asked to take a 'small' risk, I suspect whispers would have gotten around long before the plane flew. Therefore, it's likely that it was just one of many other design 'solutions' where the idea of tolerable risk was normalised.

No software patch will fix systemic management hubris.
Really? Do you think a crew will board then? As has been posted in many topics, most pax have no clue what aircraft type they are flying on. They fly by the dollar. If the crew boards, so will the pax.
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Old 22nd Mar 2019, 01:38
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Originally Posted by HarryMann
Yes, though that Bob is why you as a manufacturer should Tell them what the heck you've done to the stab trim circuit... which it sounds ominously like was poorly or undocumented. Nor we are told, was much if anything made of it as a 'difference' feature in any training (?).
You're right, Harry, Boeing should have told the crews. "If you're out doing flaps up stalls in your MAX, you will get an intervention from MCAS. Also, if you get a continuous stick shaker on take off rotation & are stupid enough to accelerate, clean up the flaps, & try to continue the flight with the stick shaker, you MAY get a repeated intervention from MCAS 'cause it thinks the airplane is stalling".
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Old 22nd Mar 2019, 01:50
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Originally Posted by Kerosene
Suppose MCAS becomes unavailable during flight e.g. due to Stab trim deactivation. The MAXs flight characteristics in approach to stall scenarios proved not certifiable without MCAS as a fix. Id like to ask the ones in the know (FcEng and others) how critical the loss of MCAS in flight would be in real life. For example, encountering a flight upset with approach to stall, how easily can this be recovered without MCAS? How was the risk of such an event assessed? Was it demonstrated in test flights? Why was it determined there would be no need to train flight crews on the simulator for the changed handling outside the certification parameters?

In a previous post I assumed such a scenario to be critcal, but perhaps it isnt? Thanking you in advance for shedding light on this issue.
I have asked this before but in a different way.

Is there any recorded valid activation of MCAS?

Is it even possible that we have a tick box implementation for certification purposes that has achieved nothing other than promote accidents?
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Old 22nd Mar 2019, 02:14
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But, how do you design for an airline that flies an aircraft for three days with unreliable airspeed, maintenance that then compounds the problem with a bad AOA installation, & flight crews that still try to complete the flight with a continuous stick shaker? We don't know yet about Ethiopian, but if it was the same malfunction after all the warnings & publicity worldwide from Lion Air, then that is the height of incompetence.
Hard not to concur.A lot of Boeing bashing going on here.
Life isnt black and white like that.
Its not all Boeings fault.Its not all the pilots fault for not cutting out those 2 switches.
I think it was mentioned by FCENG84 that designers design safe
in the knowledge that airline pilots have a minimum standard
of airmanship and that line engineers know their job and
follow the MEL.Lionair's reputation is not a good one.
And frankly speaking,neither is Ethiopian.So its a difficult.situation
to analyse.Do I think either accident could have
happened in Southwest?No,I do not.

Boeing obviously considered the consequences of a faulty
sensor and its effect on MCAS prior certification.They knew
this would occur at flap retraction at low altitude and would result
in stick shaker,unreliable airspeed and considerable and
unexpected nose down trim all at once.They decided
that this failure scenario was one step shy of "catastrophic".
and that a crew would cope.Maybe they under-rated the
effect of the stick shaker on the pilots ability to react in the
correct manner.Those shakers can scramble your brain
and degrade reaction time and pilot response.They can cause
startle factor which I know is sometimes derided as an
excuse for poor airmanship.But it can happen and it can affect
quite a few crews.
Whats not okay is if they deliberately downgraded it below
"catastrophic" to rush certification and avoid further analysis
and fine-tuning of the design.If they genuinely miscalculated
the effect of unwanted MCAS at low altitude and so designed
it to work off one sensor only,then its just an error.
However,if they downgraded it below "catastrophic" to rush
certification then it was a cynical decision and thats negligence.
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Old 22nd Mar 2019, 02:31
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Originally Posted by Rananim
Boeing obviously considered the consequences of a faulty
sensor and its effect on MCAS prior certification.They knew
this would occur at flap retraction at low altitude and would result
in stick shaker,unreliable airspeed and considerable and
unexpected nose down trim all at once.
It's not obvious to me that Boeing considered those possible consequences and it's not at all clear that any or every failure of an AoA sensor -- or another fault in raw data or processing upon which MCAS activation is dependent -- would result in identical systems behaviors, always in a single phase of flight. In fact, with all due respect, I seriously doubt whether either of those assumptions is defensible.
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Old 22nd Mar 2019, 02:34
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Originally Posted by Rananim

Boeing obviously considered the consequences of a faulty
sensor and its effect on MCAS prior certification.They knew
this would occur at flap retraction at low altitude and would result
in stick shaker,unreliable airspeed and considerable and
unexpected nose down trim all at once.
Rananim, a faulty AOA that would activate MCAS would produce a continuous stick shaker at rotation, not on flap retract. Why would any right-thinking pilot ever attempt to retract flaps & continue the flight with an active stick shaker, even if unaware that MCAS exists?
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Old 22nd Mar 2019, 02:37
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SLF here, but with a background in experimental physics dealing with personnel and equipment safety in large-scale, hazardous experimental situations.

Assuming that both 737 MAX crashes were the result (in large part) of faulty AOA probe data, then we already know, from sad experimental evidence, that relying on one probe is unacceptable. With 2 hull losses in N (? - not a terribly large number) flights of this aircraft, the reliability statistics are hardly at the flight-safety-critical level.

Having an "AOA disagree" warning or AOA readouts for pilots is not necessarily going to help. I suggest that as a minimum, with only two AOA probes (and that should be the minimum number), that MCAS should shut itself down in an AOA disagree situation (with notification to the pilots). The principle here is "primum non nocere". The aircraft is not going to have an upset just because MCAS is not there on these rare occasions.

Furthermore, if AOA data is going to be used in this way (possibly killing people if it is wrong), further sanity checks should be applied to the probe data (e.g., AOA pre-rotation on take-off, consistency with inertial and other air data, whatever).

MCAS as currently implemented seems like a horrid kluge to a non-pilot, but I'm inclined to believe, from what I've read here, that with better engineering (and not too drastic a change) the 737 MAX could be restored to safe service.
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Old 22nd Mar 2019, 02:54
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Rananim, a faulty AOA that would activate MCAS would produce a continuous stick shaker at rotation, not on flap retract. Why would any right-thinking pilot ever attempt to retract flaps & continue the flight with an active stick shaker, even if unaware that MCAS exists?
BobM2
Yes you are of course correct but that doesnt alter the fact that crews who
elect to retract flaps and climb to MSA as per SOP would face
all 3 concurrently with flaps up.You assert that no crew would retract
flaps and climb to MSA to perform checklists and I hope you
are right.I agree with not retracting flaps and just landing from circuit height
but I dont assume thats what all crews would do,especially
if unfamiliar with MCAS.
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Old 22nd Mar 2019, 03:22
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Originally Posted by Rananim
BobM2
Yes you are of course correct but that doesnt alter the fact that crews who
elect to retract flaps and climb to MSA as per SOP would face
all 3 concurrently with flaps up.You assert that no crew would retract
flaps and climb to MSA to perform checklists and I hope you
are right.I agree with not retracting flaps and just landing from circuit height
but I dont assume thats what all crews would do,especially
if unfamiliar with MCAS.
You are right. At least 2 crews, maybe 3 did accelerate, clean up, & got into a worse mess. These occurrences were all in good weather with long runways immediately available. There was no need to climb to an MSA, but you could if you felt a need to troubleshoot or read checklists. The main thing is don't change the take-off configuration as long as the airplane is flying normally. You are not paid or qualified to be a test pilot, especially with passengers on board.
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Old 22nd Mar 2019, 04:02
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Originally Posted by BobM2
You are right. At least 2 crews, maybe 3 did accelerate, clean up, & got into a worse mess. These occurrences were all in good weather with long runways immediately available. There was no need to climb to an MSA, but you could if you felt a need to troubleshoot or read checklists. The main thing is don't change the take-off configuration as long as the airplane is flying normally. You are not paid or qualified to be a test pilot, especially with passengers on board.
What we can only conclude as a design flaw requires recurring RTO above Vr?

Wrong focus.

Last edited by pilot9250; 22nd Mar 2019 at 04:21.
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Old 22nd Mar 2019, 04:14
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Originally Posted by BobM2
You are right. At least 2 crews, maybe 3 did accelerate, clean up, & got into a worse mess. These occurrences were all in good weather with long runways immediately available. There was no need to climb to an MSA, but you could if you felt a need to troubleshoot or read checklists. The main thing is don't change the take-off configuration as long as the airplane is flying normally. You are not paid or qualified to be a test pilot, especially with passengers on board.
In regards to cleaning up and accelerating, if one is dealing with stall indications and unreliable airspeed on climb out, the natural tendency would be to ensure you've got sufficient airspeed. Speed is life, in most cases. It would appear, unfortunately, that this was not one of those cases.
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