B737 Max : CAA bans from UK airspace; Comair aircraft grounded
Mar 11, 2019, 10:48 am
#31
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With so much automation becoming dependent on some fairly basic technology (AoA sensors and pitot tubes) that are hugely vulnerable to external influences (damage, ice accretion etc.) it seems to me it’s becoming time for manufactureres to step back from ‘because we can’ to ‘is this wise?’.
Apologies for the long sentence.
Apologies for the long sentence.
Mar 11, 2019, 11:03 am
#32
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China grounding these planes is as much about Huawei and trade wars than safety imo. Until EASA and/or FAA do the same I will hold opinion.
I do share some of the concerns that the original 737 type certification has nothing to do with a current 7M8. Perhaps time to shine a light on this.
I do share some of the concerns that the original 737 type certification has nothing to do with a current 7M8. Perhaps time to shine a light on this.
BTW, when China grounds the MAX, presumably it includes not just Chinese carriers but also flights operated by foreign carriers to/from mainland China that use the MAX, right?
My biggest problem with the 737-Max discussion has been that the MCAS auto-trim system is a single fault design flaw. Retired Boeing engineers and others have been quoted as saying that the air input to the system that determines the angle of attack for the MCAS auto-trim system is a single point with no back up. Thus if there is a flaw/failure there the whole system malfunctions.
This should have been picked up at the time of FAA certification but was not (software has gotten so complex that I'm not surprised that this happened, I am surprised that Boeing has not jumped on either a fix or a disconnect of the MCAS auto-trim system.)
Remember, FAA is NOT supposed to allow certification of any aircraft where a single fault would allow disabling of the aircraft. I would think that Boeing would be better served to disable the MCAS auto-trim system and train for the flight characteristics of the 737Max rather than having the pilots fighting the computer, especially if there are times when the computer is being given false information from the angle of attack input to the MCAS auto-trim system.
This should have been picked up at the time of FAA certification but was not (software has gotten so complex that I'm not surprised that this happened, I am surprised that Boeing has not jumped on either a fix or a disconnect of the MCAS auto-trim system.)
Remember, FAA is NOT supposed to allow certification of any aircraft where a single fault would allow disabling of the aircraft. I would think that Boeing would be better served to disable the MCAS auto-trim system and train for the flight characteristics of the 737Max rather than having the pilots fighting the computer, especially if there are times when the computer is being given false information from the angle of attack input to the MCAS auto-trim system.
Mar 11, 2019, 11:30 am
#33
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It wasn’t all too long ago BA Mainline shorthaul had their own 737 issues. The 737-236 all had an inherent Rudder PCU design flaw that had sent several 737’s into unrecoverable rudder ‘hard-overs’ with operators around the globe. It was only due the a few very near misses and a lengthy investigation of aircraft that had been lost that the fault was discovered and a mod issued to all global operators. BA continued to fly the fleet throughout this period. The 737 is such a long standing design that has evolved and each evoloution has brought with it latent faults and as yet we have no idea if the two MAX 8 accidents are related. We also do not know that the issue lies with training or pilot competence. Too many unknowns.
Would I get on a MAX? Yes. Would I fly on either airline involved on amy of their other types (ok limited with Lionair I know), No!
Would I get on a MAX? Yes. Would I fly on either airline involved on amy of their other types (ok limited with Lionair I know), No!
Mar 11, 2019, 12:16 pm
#34
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If these multiple eyewitness reports are correct, a lot of people may have jumped the gun.
https://www.reuters.com/article/uk-e...-idUKKBN1QS1LH
https://www.reuters.com/article/uk-e...-idUKKBN1QS1LH
Mar 11, 2019, 12:23 pm
#35
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Each to their own. I have flown on the Max twice, once AA and once FI. Will I get on another one at this point in time? Not under any circumstances, period. If you read the thread on Pprune about this, and yes, I know it is rumours and conjecture, it appears there is a strong possibility that a design fault exists which can put the aircraft into a sharp nose down attitude at very low altitude leaving seconds to overcome the problem. Consensus there is that it is a recoverable situation but only if the crew react impeccably and locate the right switches to disable the right systems at the same time as panic is likely setting in as the ground is suddenly looming. And no, disconnection of the autopilot does not override the erroneous control inputs. And no, pulling back on the column doesn't work well either - it requires circa 60kg of force to override the system. No, I haven't flown a 737. I fly a sophisticated light aircraft so have some limited insight and no more. But I have read enough to see a pattern emerging. And whilst the theories may subsequently prove to be incorrect, they have sufficient credibility at this point to make me choose to stay away. Just checked my two domestic AA sectors next week and they are E90 and 319 respectively. But I say again, if irrops leads to a 737-max being substituted, I will refuse to board.
Mar 11, 2019, 1:24 pm
#36
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777 had issues in pattern, doesn’t that worry you? involved a BA flight
Mar 11, 2019, 1:31 pm
#37
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Oversimplifying, I know, but what about a bloody great button that disconnects all the automatics and resets all trim to neutral, and reverts to manual throttles ... and let the pilot fly the bloody thing manually? Or aren’t aome Captains able to do that any more? 
I wouldn’t dare post that on PPRuNe, of course. I’m not a pilot.
I wouldn’t dare post that on PPRuNe, of course. I’m not a pilot.
Mar 11, 2019, 1:37 pm
#38
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I know it is rumours and conjecture, it appears there is a strong possibility that a design fault exists which can put the aircraft into a sharp nose down attitude at very low altitude leaving seconds to overcome the problem. Consensus there is that it is a recoverable situation but only if the crew react impeccably and locate the right switches to disable the right systems at the same time as panic is likely setting in as the ground is suddenly looming.
For clarity, it looks it's Comair's single example of the MAX that is being grounded: https://www.iol.co.za/business-repor...7-max-19811120
Surely the remainder of the 737-800 fleet isn't in the least bit affected by this?
Surely the remainder of the 737-800 fleet isn't in the least bit affected by this?
Mar 11, 2019, 1:41 pm
#39
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Oversimplifying, I know, but what about a bloody great button that disconnects all the automatics and resets all trim to neutral, and reverts to manual throttles ... and let the pilot fly the bloody thing manually? Or aren’t aome Captains able to do that any more?
I wouldn’t dare post that on PPRuNe, of course. I’m not a pilot.
I wouldn’t dare post that on PPRuNe, of course. I’m not a pilot.
IMO (IANAP = I am not a pilot), this would work for pilots with lots of hours flying for major (legacy) first world carriers, but not when the cockpit crew consists of only two, with at least one being very inexperienced. Having a third person to improve crew resource management wouldn't be cost effective, so that wouldn't fly as a solution, nor could having only very experienced pilots be mandates for some of these carriers.
Mar 11, 2019, 1:46 pm
#40
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IMO (IANAP = I am not a pilot), this would work for pilots with lots of hours flying for major (legacy) first world carriers, but not when the cockpit crew consists of only two, with at least one being very inexperienced. Having a third person to improve crew resource management wouldn't be cost effective, so that wouldn't fly as a solution, nor could having only very experienced pilots be mandates for some of these carriers.
https://www.pprune.org/10414149-post460.html
Mar 11, 2019, 1:57 pm
#41
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With so much automation becoming dependent on some fairly basic technology (AoA sensors and pitot tubes) that are hugely vulnerable to external influences (damage, ice accretion etc.) it seems to me it’s becoming time for manufactureres to step back from ‘because we can’ to ‘is this wise?’.
Apologies for the long sentence.
Apologies for the long sentence.
I was uncomfortable with a long, overwater 787 flight i took in the early days, and i'd be uncomfortable taking a 737 MAX flight now.
Mar 11, 2019, 2:00 pm
#42
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Oversimplifying, I know, but what about a bloody great button that disconnects all the automatics and resets all trim to neutral, and reverts to manual throttles ... and let the pilot fly the bloody thing manually? Or aren’t aome Captains able to do that any more?
I wouldn’t dare post that on PPRuNe, of course. I’m not a pilot.
I wouldn’t dare post that on PPRuNe, of course. I’m not a pilot.
i haven’t see anything which suggests the auto throttle system was malfunctioning for the lion air incident so no reason to touch that.
Mar 11, 2019, 2:09 pm
#43
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I saw somewhere a fairly nice summation of Airbus aircraft being designed from day 1 to be automated, whilst Boeings are designed as a manual aircraft with ever increasing layers of automation to meet certification requirements. The MCAS on the 737 MAX reads like it might be a layer too far.
I was uncomfortable with a long, overwater 787 flight i took in the early days, and i'd be uncomfortable taking a 737 MAX flight now.
I was uncomfortable with a long, overwater 787 flight i took in the early days, and i'd be uncomfortable taking a 737 MAX flight now.
Mar 11, 2019, 2:10 pm
#44
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Mar 11, 2019, 2:25 pm
#45
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My understanding is that Airbus was designed from the ground up as a mostly automated aircraft, while the 737 in particular has been stretched, modified and tweaked so many times it only bears a passing resemblance to the original from the 60's. It seems like it's layers of modification upon modification, and as such the type approval process may not be as rigorous as a new type approval; so there is the potential for flaws to get missed.