Originally Posted by DaveReidUK
(Post 10415091)
Triplexed systems have been around for 50+ years. How many times in that period has a good input been outvoted by two bad ones ?
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Originally Posted by jimtx
(Post 10391326)
The Brazilian Certifying authority did, with Boeing's involvement, require MCAS training. What that training was would be interesting. I would assume somebody from GOL, a Max operator, would know what that was. If we find out we might know whether that type of training would have helped the Lion Air crew.
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Originally Posted by Lonewolf_50
(Post 10415228)
jim, was this before or after the LionAir accident? If before, good job Brazilian Certifying authority
I can also mention that I read somewhere that European EASA also was not happy with the MCAS not beeing disclosed to the pilots, and lack of training in its functionality, but they in the end caved in and followed FAA. |
Originally Posted by Lonewolf_50
(Post 10415228)
jim, was this before or after the LionAir accident? If before, good job Brazilian Certifying authority
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Thank you Jim.
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Salute!
The problem, Wolf and Jimtx, is that the specific indications/symptoms of erroneous MCAS activation are not all that clear. Not like basic runaway trim that most pilots recognize right away, huh? The AoA sensor failure or being FUBAR activates the stick shaker, right? Then an audible warning, right? Then does it also activate the unreliable speed warning ? GASP! There could be some back door paths for the various kludge boxes ( STS, feel system, etc) to disguise the obvious MCAS activation of down trim then 5 seconds before next down trim by presenting the crew with all kindsa warning lights and tones. I have no problem with many crews not realizing that the MCAS is FUBAR because the down trim goes way with just a tap on the trim switch. So 5 seconds later, just as they were going thru another procedure or making a radio call the damned thing does it gain and he beeps the trim and it goes away. You can clearly see this on both of the Lion Air plots. And I also believe that the "flight before" crew suspected STS failure or something other than MCAS. So they just pulled a Luke Skywalker trick and went manual. The problem with the scenario is that you only have 5 seconds to disable electric trim before the bugger starts again. The CRM and decision of a trim system malfunction all come into play. I think thatI could have set up this scenario back last summer and most crews would have crashed. Gums sends... |
Originally Posted by Lonewolf_50
(Post 10415307)
Thank you Jim.
https://cimg3.ibsrv.net/gimg/pprune....a1d2ad931c.jpg |
Originally Posted by icemanalgeria
(Post 10388860)
How many times did a Boeing stall and Crash without this system ? Do we really need this kind of solution in today’s aircraft ? 2018 UT Air in Sotschi (NG) The reason why they had to certify MCAS was that a 737 is potentially not sustained stable in pitch in high power settings. And if you don't trim early and fast enough you cannot avoid the stall anymore. On the MAX it's even more pronounced. |
"Eyewitnesses say they saw a trail of smoke, sparks and debris as the plane nosedived." (https://www.bbc.com/news/world-asia-47536502)
IF TRUE: Does that sound like an MCAS-caused event? Or more in keeping with an engine FOD Ingestion, or perhaps even a pyrotechnic issue of some kind? |
Originally Posted by Dani
(Post 10415750)
2016 Flydubai in Rostow (Classic)
2018 UT Air in Sotschi (NG) The reason why they had to certify MCAS was that a 737 is potentially not sustained stable in pitch in high power settings. And if you don't trim early and fast enough you cannot avoid the stall anymore. On the MAX it's even more pronounced. |
Originally Posted by jimtx
(Post 10416094)
This is not correct. |
Originally Posted by Dani
(Post 10415750)
2016 Flydubai in Rostow (Classic)
2018 UT Air in Sotschi (NG) The reason why they had to certify MCAS was that a 737 is potentially not sustained stable in pitch in high power settings. And if you don't trim early and fast enough you cannot avoid the stall anymore. On the MAX it's even more pronounced. With low cost airlines and carry on luggage what happens to the centre of gravity in relation to the massive thrust how much was in the hold in these flights. All the holes in the cheese lines up. |
Originally Posted by hans brinker
(Post 10386987)
https://cimg9.ibsrv.net/gimg/pprune....b62da90118.jpg
https://cimg0.ibsrv.net/gimg/pprune....6092bf2e88.jpg Because they can't certify the aircraft without MCAS. At high AOA the engines (being MUCH bigger and WAY further forward) provide too much aerodynamic lift ahead of the CG, pushing the nose up even further. MCAS adds AND trim in this scenario. Just compare the B737-100 with the B737-MAX and you see why they needed to add electronic band-aids to keep it legal. One can only presume the engines were engineered in that position due to their increased aerodynamic lift profile. An economically motivated trade-off between; (being competitive, pushing the envelope, increasing system complexity), and, (cost, safety, simplicity, and reliability). I used to work on some 737-200’s - probably the first jet I was able to sit jump seat too. Thanks for reigniting some nostalgic memories with that post. I have no visibility to the design spec, but if there is no vote comparison for sensors that provide critical data, essential to airworthiness, then my eyebrows are raised :/ |
Originally Posted by davionics
(Post 10416246)
One can only presume the engines were engineered in that position due to their increased aerodynamic lift profile. The A320 was designed for larger engines from the start, and hence doesn't have the same problem. |
Originally Posted by infrequentflyer789
(Post 10416425)
I believe they have had to add several inches to the nose gear.
The 737 Max has a semi-levered main gear (a bit like that on the 777-300ER, mostly for tail strike protection on the Max 9) and also a "shrink-link" that in effect shortens the longer Max main leg on retraction so that it can still be accommodated in the bay. |
I haven’t read the whole thread so I may be repeating another post, but could it be something as simple as damage to the AoA sensor by poor ground handling? Maybe the environments in which they were operating had a less stringent reporting system for on ground damage. Maybe something happened after the walk around in both these accidents. |
Should we be worried that there appears to be a gap between the FAA and EASA and other safety agencies? I don't know what to make of a situation where some agencies think that there is a sufficient grounds for concern to warrant stopping over flights of the 737 MAX, and other don't. The aviation industry has been the leader in improving safety through a culture of incremental improvement, detailed investigation and analysis of all the root causes of accidents and incidents, seeking answers, not someone to blame, and free of political and commercial influence. I will be much happier once the FAA & EASA are back on the same page regards the 737 MAX.
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Originally Posted by Packs off
(Post 10416473)
I haven’t read the whole thread so I may be repeating another post, but could it be something as simple as damage to the AoA sensor by poor ground handling? Maybe the environments in which they were operating had a less stringent reporting system for on ground damage. Maybe something happened after the walk around in both these accidents. |
Some Learjet style tail strakes might solve the problem aerodynamically, rather than the MCAS work around.
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Originally Posted by DaveReidUK
(Post 10416468)
And, more importantly, the main gear is also lengthened so that even with the bigger engines, the engine-to-ground clearance is only 2-3 inches less than the NG.
The 737 Max has a semi-levered main gear (a bit like that on the 777-300ER, mostly for tail strike protection on the Max 9) and also a "shrink-link" that in effect shortens the longer Max main leg on retraction so that it can still be accommodated in the bay. |
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