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Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed

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Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed

Old 12th Mar 2019, 15:46
  #121 (permalink)  
 
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Originally Posted by DaveReidUK View Post
Triplexed systems have been around for 50+ years. How many times in that period has a good input been outvoted by two bad ones ?
Once that I know of, during an early test flight of a V-22, but that seems to have been set up by a wiring problem that was identified and corrected.
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Old 12th Mar 2019, 15:48
  #122 (permalink)  
 
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Originally Posted by jimtx View Post
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.
jim, was this before or after the LionAir accident? If before, good job Brazilian Certifying authority
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Old 12th Mar 2019, 16:18
  #123 (permalink)  
 
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Originally Posted by Lonewolf_50 View Post
jim, was this before or after the LionAir accident? If before, good job Brazilian Certifying authority
It was before, in fact before the Max was entered into service i Brazil.

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.
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Old 12th Mar 2019, 16:19
  #124 (permalink)  
 
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Originally Posted by Lonewolf_50 View Post
jim, was this before or after the LionAir accident? If before, good job Brazilian Certifying authority
This was during their certification process. Boeingís chief technical pilot was listed as participating. But the training category required was a level that could be done by CBT or otherwise. What it was at GOL we donít know but since they grounded their Max fleet they probably are rethinking what that training should be.
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Old 12th Mar 2019, 16:33
  #125 (permalink)  
 
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Thank you Jim.
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Old 12th Mar 2019, 16:39
  #126 (permalink)  
 
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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...
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Old 12th Mar 2019, 16:45
  #127 (permalink)  
 
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Originally Posted by Lonewolf_50 View Post
Thank you Jim.
Relevant page from the report. There are some other difference on that page where the Brazilians differ from the FAA under the Flt Char column as to "minor" or "no" for other systems.
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Old 12th Mar 2019, 21:18
  #128 (permalink)  
 
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Originally Posted by icemanalgeria View Post
How many times did a Boeing stall and Crash without this system ?

Do we really need this kind of solution in todayís aircraft ?
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.
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Old 13th Mar 2019, 03:16
  #129 (permalink)  
 
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"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?
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Old 13th Mar 2019, 03:17
  #130 (permalink)  
 
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Originally Posted by Dani View Post
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.
This is not correct.
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Old 13th Mar 2019, 06:50
  #131 (permalink)  
 
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Originally Posted by jimtx View Post


This is not correct.
So what is the truth then?
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Old 13th Mar 2019, 07:11
  #132 (permalink)  
 
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Originally Posted by Dani View Post
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.
I was just looking to see if anyone has tried this with full power in the sim. Its looking like the software is fighting the engine power increasing the angle of attack.

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.
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Old 13th Mar 2019, 07:40
  #133 (permalink)  
 
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Originally Posted by hans brinker View Post



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 737-200ís - 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 :/

Last edited by davionics; 13th Mar 2019 at 09:07.
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Old 13th Mar 2019, 10:19
  #134 (permalink)  
 
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Originally Posted by davionics View Post

One can only presume the engines were engineered in that position due to their increased aerodynamic lift profile.
Not really, they were engineered in that position because they are much bigger than the engines the plane was originally designed for and if mounted "normally" under the wing they would be too close to the ground (if not on it). Longer gear is not an easy option as it has to fold away into the same space or you have to redesign fuselage (probably causing cascade of redesign and re-certify changes), even so, I believe they have had to add several inches to the nose gear.

The A320 was designed for larger engines from the start, and hence doesn't have the same problem.
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Old 13th Mar 2019, 10:55
  #135 (permalink)  
 
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Originally Posted by infrequentflyer789 View Post
I believe they have had to add several inches to the nose gear.
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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Old 13th Mar 2019, 11:02
  #136 (permalink)  
 
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I havenít 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.
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Old 13th Mar 2019, 11:14
  #137 (permalink)  
 
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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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Old 13th Mar 2019, 11:16
  #138 (permalink)  
 
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Originally Posted by Packs off View Post
I havenít 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.
My understanding is that the aircraft that flew as JT610 had had an AoA sensor replaced following events on previous flights, The failure of a second sensor on the same plane seems 'unlikely', and the subsequent failure of the equivalent sensor in another accident even more so, given the general reliability of this kit.
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Old 13th Mar 2019, 11:41
  #139 (permalink)  
 
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Some Learjet style tail strakes might solve the problem aerodynamically, rather than the MCAS work around.
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Old 13th Mar 2019, 11:58
  #140 (permalink)  
 
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Originally Posted by DaveReidUK View Post
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.
No, only the MAX 10 will have a modified Main Landing Gear. However all MAXes have a lengthened Nose Landing Gear (12 inches IIRC) which makes for the strange stance of the airplane on ground.

Last edited by oceancrosser; 13th Mar 2019 at 12:29.
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