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Boeing 737 MAX is stupidly designed

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Boeing 737 MAX is stupidly designed

Old 03-26-2019, 08:29 AM
  #221  
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I saw a video that said "The 737 MCAS system switches AOA sensors every flight". If this is true, and it was in fact not in the mechanics maintenance manuals I can concede that is a major mess up. The video asserted that is why Lion air mechanics couldn't replicate the problem, because the test switched sensors. Then, the test counted as a flight, and the doomed flight was back on the failed sensor. The manual may not have said to run the test twice to check both sensors. I hope this isn't true.
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Old 03-26-2019, 09:02 AM
  #222  
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Originally Posted by TurboJoe View Post
I saw a video that said "The 737 MCAS system switches AOA sensors every flight". If this is true, and it was in fact not in the mechanics maintenance manuals I can concede that is a major mess up. The video asserted that is why Lion air mechanics couldn't replicate the problem, because the test switched sensors. Then, the test counted as a flight, and the doomed flight was back on the failed sensor. The manual may not have said to run the test twice to check both sensors. I hope this isn't true.

wow! why wouldn't it rely on both sensors to confirm a correct reading? especially if the plan is already equipped with two... very strange...
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Old 03-26-2019, 09:41 AM
  #223  
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Originally Posted by ndb8fxe View Post
reliance on the instruments is far more crucial than that of seat of pants stuff. This and seat of pants has proven to work really poorly in IMC.
Yep, I agree with you. What I was saying is that if this 737 is going up and down like a bucking bronco, I won't need much to understand what flight envelope we'd be in.

OVER reliance on whiz-bang gizmos have also killed some people.....

The Asiana Airbus crash in San Fran come to mind.
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Old 03-26-2019, 09:52 AM
  #224  
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Originally Posted by HurricaneBK View Post
This article says that the Lion Air pilots cycled the cut-off switches more than two dozen times before they crashed. It's not really clear in the article what else a pilot has to do after switching the cut-off switches to disable MCAS though, just saying that it buys them more time to control the plane by doing so.

https://www.nytimes.com/2019/03/25/b...ion-error.html
That's not what the article says. It says "pilots used the thumb switch more than two dozen times to try to override the system." These are the manual controls that the pilot has to trim up or trim down. They are NOT the cutoff switches. They could have done this indefinitely or until they actually used the cut off switches.

Question for the pilots: Do the cutoff switches just disable the automatic trim (STS , MCAS, etc) or do they disable the whole electrical trim system (including the pilots trim switches)?

The article also says: "If the system starts pushing the plane’s nose down, pilots can reverse the movement via a switch at their thumb, a typical reaction in that situation. In doing so, they can potentially extend the 40-second window, giving them more time to avoid a crash. To fully neutralize the system, pilots would need to flip two more switches. That would shut off the electricity to a motor that allows the system to push the plane toward the ground."
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Old 03-26-2019, 09:59 AM
  #225  
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Originally Posted by TurboJoe View Post
I saw a video that said "The 737 MCAS system switches AOA sensors every flight". If this is true, and it was in fact not in the mechanics maintenance manuals I can concede that is a major mess up. The video asserted that is why Lion air mechanics couldn't replicate the problem, because the test switched sensors. Then, the test counted as a flight, and the doomed flight was back on the failed sensor. The manual may not have said to run the test twice to check both sensors. I hope this isn't true.
I'm pretty sure I read an article somewhere that said that they did change the AOA sensor. Don't know where they got that info from, or if it was just speculation. I'll dig around and see if I can find it again. It also included some discussion of the actual internal workings of the AOA sensors and possible failure modes that would result in the readings that were seen on the FDR. It appears that the sensor didn't fail outright, but was off a bit, indicating the plane was climbing when indeed it wasn't.

From the FDR it shows you what the sensors are outputting. I would think that info would also be available for diagnostics on the issue and would would confirm which side needed attention.
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Old 03-26-2019, 10:03 AM
  #226  
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Originally Posted by km1125 View Post
That's not what the article says. It says "pilots used the thumb switch more than two dozen times to try to override the system." These are the manual controls that the pilot has to trim up or trim down. They are NOT the cutoff switches. They could have done this indefinitely or until they actually used the cut off switches.

Question for the pilots: Do the cutoff switches just disable the automatic trim (STS , MCAS, etc) or do they disable the whole electrical trim system (including the pilots trim switches)?

The article also says: "If the system starts pushing the plane’s nose down, pilots can reverse the movement via a switch at their thumb, a typical reaction in that situation. In doing so, they can potentially extend the 40-second window, giving them more time to avoid a crash. To fully neutralize the system, pilots would need to flip two more switches. That would shut off the electricity to a motor that allows the system to push the plane toward the ground."
Ok so the switch at their thumb isn't the same switch shown in a picture earlier in the thread that cuts it off, my mistake. Those switches I assume are the important ones that cut electricity to the motor.
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Old 03-26-2019, 10:18 AM
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Originally Posted by HurricaneBK View Post


Ok so the switch at their thumb isn't the same switch shown in a picture earlier in the thread that cuts it off, my mistake. Those switches I assume are the important ones that cut electricity to the motor.
The thumb switches are up on the yolk and allow either pilot to manually trim up or down without taking their hands off the controls. The cut-off switches are on the console between both pilots
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Old 03-26-2019, 10:20 AM
  #228  
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Originally Posted by HurricaneBK View Post


Ok so the switch at their thumb isn't the same switch shown in a picture earlier in the thread that cuts it off, my mistake. Those switches I assume are the important ones that cut electricity to the motor.
Correct, and also from my understanding, the thumb switch counter acts the mcas and lets them trim it back to nose up.. if they only kept doing it.
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Old 03-26-2019, 11:06 AM
  #229  
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Question for the pilots: Do the cutoff switches just disable the automatic trim (STS , MCAS, etc) or do they disable the whole electrical trim system (including the pilots trim switches)?
I believe those switches shut down the entire trim system. You can then re-trim with the manual trim wheel.

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Old 03-26-2019, 11:23 AM
  #230  
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My apologies if this has been posted here already. Looks like an admission of guilt from Boeing.

https://www.foxnews.com/science/boei...ne-report-says

I have read that Ethiopia has stated that both pilots had been trained and qualified on the Max. If that is true, we'll find out in the Investigation. We will also find out the true amount of flight hours of the 737 F/O. I call total BS that he only had 200 total hours. 200 in the 737 more likely.

One other way to stop a Runaway Stabilzer Trim is to push the wheel in the opposite direction to the runaway. If the black and white manual trim wheels start running in a backwards turn, that will make the nose go up, so we were trained (in my antique 737 at least) to push forward on the wheel/yoke. That should 'lock' or stop the trim movement.

And here's what I'd love to know. "Did the MCAS kick in normally due to its pre-set parameters, or did it activate by accident or due to a malfunction?"
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Old 03-26-2019, 12:03 PM
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Originally Posted by Gary M View Post
My apologies if this has been posted here already. Looks like an admission of guilt from Boeing.

https://www.foxnews.com/science/boei...ne-report-says

I have read that Ethiopia has stated that both pilots had been trained and qualified on the Max. If that is true, we'll find out in the Investigation. We will also find out the true amount of flight hours of the 737 F/O. I call total BS that he only had 200 total hours. 200 in the 737 more likely.

One other way to stop a Runaway Stabilzer Trim is to push the wheel in the opposite direction to the runaway. If the black and white manual trim wheels start running in a backwards turn, that will make the nose go up, so we were trained (in my antique 737 at least) to push forward on the wheel/yoke. That should 'lock' or stop the trim movement.

And here's what I'd love to know. "Did the MCAS kick in normally due to its pre-set parameters, or did it activate by accident or due to a malfunction?"
Where do you get "admission of guilt:"??? I don't see that anywhere. They are improving a system but it's still functioning essentially the same. What if these accidents were due to stalling because the pilots were pitching up too high? Would they be modifying the MCAS to be more aggressive???

How many other things can go wrong in a flight, which, if not addressed in 40 seconds, could lead to a catastrophic issue?? I'm betting there are MANY, MANY things. The 40 second timing is if you IGNORE what's going on and don't counteract the system or don't address the issue by using the supplied features (switches) and available procedures (runaway trim) to address an issue.
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Old 03-26-2019, 12:25 PM
  #232  
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Originally Posted by km1125 View Post
I'm pretty sure I read an article somewhere that said that they did change the AOA sensor.
Here is some of that info:Further examination of the aircraft's instruments revealed that one of the aircraft's airspeed indicators had malfunctioned for its last four flights, including the flight to Denpasar.

On 7 November, the NTSC confirmed that there had been problems with Flight 610's angle of attack (AoA) sensors. Thinking that it would fix the problem, the engineers in Bali then replaced one of the aircraft's AoA sensors, but the problem persisted on the penultimate flight, from Denpasar to Jakarta. Just minutes after takeoff, the aircraft abruptly dived. The crew of that flight, however, had managed to control the aircraft and decided to fly at a lower than normal altitude. They then managed to land the aircraft safely and recorded a twenty-degree difference between the readings of the left AoA sensor and the right sensor.[121] NTSC chief Soerjanto Tjahjono told the press that future reporting or actions, enacted to prevent similar problems on similar aircraft, would be decided by Boeing and US aviation authorities.[122]On 28 November, Indonesia investigators said the Lion Air jet was not airworthy on the flight before the crash. Several relatives of the crash victims have already filed lawsuits against Boeing.[123]

Preliminary report

On 28 November, the Indonesian National Transportation Safety Committee (NTSC) released its preliminary accident investigation report.[124] After airspeed and altitude problems, an AoA sensor was replaced and tested two days earlier on the accident aircraft.[125] Erroneous airspeed indications were still present on the subsequent flight on 28 October, which experienced automatic nose down trim.[125] The runaway stabilizer non-normal checklist was run, the electric stabilizer trim was turned off, and the flight continued with manual trim; the issues were reported after landing.[125] Shortly after takeoff on 29 October, issues involving altitude and airspeed continued due to erroneous AoA data and commanded automatic nose-down trim via the Maneuvering Characteristics Augmentation System (MCAS).[125] The flight crew repeatedly commanded nose-up trim over the final ten minutes of the flight.[125] The report does not state whether the runaway stabilizer trim procedure was run or whether the electric stabilizer trim switches were cut out on the accident flight.
WIKI_SOURCE

With the reported problems with airspeed sensors on FOUR of the last flights, and AOA problems on the last THREE flights, I'd be looking more and more at the situations surrounding the treatment of the planes between flights and the maintenance procedures. What's the chances of replacing one bad AOA sensor for another identically-bad AOA sensor???
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Old 03-26-2019, 01:45 PM
  #233  
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did you guys see this story yet?

An empty 737 MAX was on its way to California to be stored during the grounding and it had to abort and land in Orlando. Note: These empty flights are allowed even though the plan is landed so that the planes can be moved to proper maint. facilities.

Just crazy!


Southwest Boeing 737 Max makes emergency landing at Orlando International Airport - Story | WOFL
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Old 03-26-2019, 01:48 PM
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Preliminary reports on twitter report that it was due to an engine problem unrelated to the actual grounding concern but man this plane can't seem to catch a break!
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Old 03-26-2019, 04:26 PM
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Originally Posted by km1125 View Post
With the reported problems with airspeed sensors on FOUR of the last flights, and AOA problems on the last THREE flights, I'd be looking more and more at the situations surrounding the treatment of the planes between flights and the maintenance procedures. What's the chances of replacing one bad AOA sensor for another identically-bad AOA sensor???
Question for the pros - When you are the PIC of a flight that has had a significant in-flight event resulting in a partial loss of control of the aircraft, when you write that up in the aircraft log/squawk-sheet, would you typically include any successful remedial action that you took to recover the aircraft? I can imagine that might be useful to both the mechanics and the next guy to ride the pointy end of the tin can.
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Old 03-27-2019, 12:28 AM
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Originally Posted by SilverGraphite View Post
Question for the pros - When you are the PIC of a flight that has had a significant in-flight event resulting in a partial loss of control of the aircraft, when you write that up in the aircraft log/squawk-sheet, would you typically include any successful remedial action that you took to recover the aircraft? I can imagine that might be useful to both the mechanics and the next guy to ride the pointy end of the tin can.
Our Mx logbooks have a space for the descrepancy item then another space below for clarification or extra details that may be of useful info to the mechanics. It’s also good form to verbally brief the mx team upon arrival on what exactly happened. Kind of a dick move to write something up and walk away without at least chatting with the guys.

example
Discrepancy: Amber Windscreen OVHT caution light illuminated in flight.

Clarification Notes: Condition occurred during cruise flight at FL410. Temp -54. QHR Items complied with. Light remained illuminated during all phases of flight.
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Old 03-27-2019, 02:39 AM
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Here’s another question (directed at those certified and current on 737, preferably on max version)

the data currently available wrt the 2 crashes, seem to implicate automated trim causing the aircraft to nose down....

what has more aerodynamic authority, full nose down trim, or full up on the control yoke?
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Old 03-27-2019, 06:14 AM
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Originally Posted by mickt243 View Post
Here’s another question (directed at those certified and current on 737, preferably on max version)

the data currently available wrt the 2 crashes, seem to implicate automated trim causing the aircraft to nose down....

what has more aerodynamic authority, full nose down trim, or full up on the control yoke?
I don't meet those qualifications to answer, but from my research: Since the trim moves the whole stabilizer and it's much larger than the elevators, a full down trim has more authority than full up elevator. I'm curious to hear the qualified weigh in though!! But the real reason I'm responding is to add on a question to yours for those same folks.... I read that moving the yoke will stop or delay the automatic trim from happening.... is that true??
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Old 03-27-2019, 06:32 AM
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Maybe one of the non trained authoritative aviation design and airline operation experts, on this thread, could elaborate on liability implications as it relates to the following-

It is my understanding, BA offered upgraded safety options and Ethiopian Airlines didn't purchase those upgrades, does that make Ethiopian airlines culpable?
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Old 03-27-2019, 06:53 AM
  #240  
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Originally Posted by km1125 View Post
Where do you get "admission of guilt:"??? I don't see that anywhere. .
The fact that they are quickly changing the software to the MCAS, the fact that they brought 200 pilots, etc to Seattle to talk about MCAS, the fact that they are expanding the Training for MCAS......

See the Common Denominator there? Coming from Boeing.......
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