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Boeing 737 MAX is stupidly designed

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Boeing 737 MAX is stupidly designed

Old 03-16-2019, 04:28 PM
  #101  
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Originally Posted by coastboater View Post
Farnborough Air Show - zero gravity at -1:00 - amazing it doesn't stall at that climb rate

https://m.youtube.com/watch?v=RyeqeqSNSgQ
Not sure they still do it but American Airlines used to do a flyby over the water and all the boats during the Ft Lauderdale Air/Sea show. They would have every plane in their inventory ( an example of each one ) fly by low over the water, and then hit the up button over the crowd. First time I saw a 777 do some amazing stuff, I was more impressed by that than the Blue Angels shortly afterwards.

They started low enough you can see the rivets in the belly of the plane, gear down, lots of flaps, then up up and away.
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Old 03-16-2019, 04:29 PM
  #102  
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Originally Posted by aubv View Post




Many accidents are not because of single thing but a cascade of events..... including human reactions.....

Agree.
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Old 03-16-2019, 04:31 PM
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Originally Posted by GulfC View Post
Dude (and I hate the word dude but it's appropriate here), it ain't rocket science. Nor brain surgery. It's a friggin' airplane. There's ton's of people that can do it. There's no secret formula, just controls like any other. Ease up, you'll get used to it.
I tend to listen to folks that actually are allowed and trained to fly this aircraft.

Don't know for sure which one of these posters are this person. I'm fairly sure 99% are not.

The 1 % with seat time are probably not going to say a thing at this point for good reason.

Does a Pelican have anti stall devices along with anti dumb ass protection built in? Can he turn it off? And who the f trained him to fly to start with? I hear Indonesian pelicans are more likely to go into a dive than US pelicans.

I would leave this alone until we get the word from the Chinese Pelican. He has stolen and re engineered the diving practice software at pennies on the dollar.
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Old 03-16-2019, 04:37 PM
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Originally Posted by Kendall View Post
Incorrect. Boeing did not institute the MCAS based on customer demands.

According to "The Air Current" (a digital publication providing exclusive news and insight on the business and technology of flying), Boeing wanted to retain the Boeing 737 but "relocated engines and their refined nacelle shape then caused an upward pitching moment- in essence, the Max's nose was getting nudged skyward. Boeing QUIETLY ADDED A NEW SYSTEM (the MCAS) to compensate for some unique aircraft handling characteristics during its Part 25 certification AND to help pilots bring the nose down in the event the jet's angle of attack drifted too high when flying manually, putting the air craft at risk of stalling."

Without the addition of the MCAS, the FAA would not have given Part 25 certification to this modified design with the relocated engines.
So tell me, since you are the self declared non-pilot, non aero-engineer expert who has spent more time in commercial airliners than in cars (a claim which I find very hard to believe by the way!) what exactly you think is "stupid" about the design? What do you believe they should do to fix it?

Do you understand that Southwest, a large customer, flys only 737s, so if Boeing goes "clean sheet" and retires the basic 737 design, they will risk losing Southwest as a customer? Do you understand that the engines were moved to accommodate new higher bypass engines for the sake of fuel economy which is presumably a customer request? Do you understand that the aircraft can be generally flown without MCAS? Do you understand that the pilot can cutout MCAS by operating 2 switches? Do you understand that even if these crashes were caused by pilots failing to realize that MCAS was erroneously attempting to correct an aircraft that it thought was at the extreme edges of the operating envelope, that the problem likely isn't even in MCAS itself, but rather in the angle of attack sensor. Do you honestly believe that a clean-sheet airframe is going to have less teething issues than a reconfiguration of an existing well proven airframe?

Does MCAS need tweaking to make it more intuitive? Probably, from what I've heard some professional pilots say (I'm not claiming to be a cattle-class expert like you). Those pilots say that if the flight deck overrides MCAS with manual trim, perhaps MCAS should refrain from trying to retrim the aircraft again after a 10 second delay. Should Boeing have done a better job with the flight manual and checklists for the Max? Sounds like it (again, from what I've heard some professional pilots say). Should there be better training for pilots? Maybe. Or maybe some airlines have the training aspect down, and some don't.

So, does all that mean that the fundamental design of the Max is a stupid design? Well, since probably every single airplane ever built has had AD's (Airworthiness Directives) issued requiring some kind of alteration of one sort or another I guess that means that by your "reality" every single aircraft design is "stupid". Me, I see designs that like everything, can be improved.
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Old 03-16-2019, 04:44 PM
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Originally Posted by 20biminitwist View Post

Does a Pelican have anti stall devices along with anti dumb ass protection built in? Can he turn it off? And who the f trained him to fly to start with? I hear Indonesian pelicans are more likely to go into a dive than US pelicans.

I would leave this alone until we get the word from the Chinese Pelican. He has stolen and re engineered the diving practice software at pennies on the dollar.
Pelicans worldwide obviously have severe control issues.. They are frequently observed to enter extreme nose-down attitudes and crash into the sea at high rates of speed. Only the soft surface of the seawater prevents them from breaking up on impact...
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Old 03-16-2019, 04:51 PM
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I’m curious to see if the jackscrew issue is the same as the jack screw issue on that Alaska Airlines plane that crashed in the ocean years ago.
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Old 03-16-2019, 04:55 PM
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I think a lot of people are hung up on the word stupid. Boeing made a design compromise to save money and make the plane more efficient. They compromised the handling of the airframe to accomplish this and, fixed it with artificial flight stability in a way that is not normally done with airliners. The system was well thought out and FAA Certified. However the system failed in flight and the failure mode was to lawn dart the airplane. For whatever reason (training, no failure notification from the system) the pilots did not figure it out in time to shut off or override the system, and 350 people are dead.

The worldwide grounding of the aircraft with the very limited info we have about this crash lets you know there is a problem. Plane crashed and we found the jack screw indicated significant nose down trim and everyone assumes the MCAS failed again.
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Old 03-16-2019, 04:58 PM
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Originally Posted by Turtle9343 View Post
I’m curious to see if the jackscrew issue is the same as the jack screw issue on that Alaska Airlines plane that crashed in the ocean years ago.
IIRC the jackscrew failure on that airplane was a mechanical issue with the trim mechanism itself. In this case the trim system was functioning properly, it was just found in the crash trimmed way nose down.
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Old 03-16-2019, 05:00 PM
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Originally Posted by Kendall View Post
Agree.
Your smartest post in this entire thread.....
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Old 03-16-2019, 05:23 PM
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Originally Posted by Turtle9343 View Post
I’m curious to see if the jackscrew issue is the same as the jack screw issue on that Alaska Airlines plane that crashed in the ocean years ago.
Seeing as that one was a maintenance/wear issue, I would not suspect that on two newer aircraft.
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Old 03-16-2019, 05:51 PM
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The Jackscrew was a lubrication issue. Nearly no one considers lubrication specific qualities except in aviation. If you want to compare this to marine, take a scan into lubrication callouts and what's actually used. I tried, in vain, to get specific lubricants on my F250TXR and met a plethora of resistance. No one carried the correct stuff, not mechanics, certified techs... no one. I ordered online and got them. Many of the issues marine engines face today is because of using the wrong lubricants. Some are for high temps, some because they old their positions, some due to viscosity. And I posted many times but no one listens.
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Old 03-16-2019, 08:02 PM
  #112  
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Originally Posted by dell30rb View Post


IIRC the jackscrew failure on that airplane was a mechanical issue with the trim mechanism itself. In this case the trim system was functioning properly, it was just found in the crash trimmed way nose down.
It was also a maintenance issue, or lack there of.
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Old 03-16-2019, 08:13 PM
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Originally Posted by GulfC View Post
Dude (and I hate the word dude but it's appropriate here), it ain't rocket science. Nor brain surgery. It's a friggin' airplane. There's ton's of people that can do it. There's no secret formula, just controls like any other. Ease up, you'll get used to it.
Dude where did I ever say it was hard? It's super easy. Just like driving a car. Dude.

Yet many can't do that.

I suppose you get your law advice from the self proclaimed lawyers on here. But disregard the handful of guys that actually step in to give solid advice that are lawyers because there are tons of people that do that too... Bro. Plus you can just read all about it on legalzoom... Dude
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Old 03-16-2019, 08:49 PM
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Originally Posted by dell30rb View Post


Correct me if I am wrong but the trim logic on the NG’s and earlier 737’s is there to make trim changes easier. It isn’t there to mask an undesirable handling characteristic. It won’t adjust the trim unless commanded by the pilot or the autopilot. The autopilot can be easily switched off with a button on the yoke.
Yes one aspect is there to make trim changes easier for example you need to run trim faster at slower speeds because there is less authority.

Yes turning the autopilot off is as easy as pushing a button. In the case of Lion Air it wasn't on. He was manually flying and fighting the trim for 5 minutes in which cases there are two switches to stop the aircraft from trimming. It does not appear these switches were flipped.

Here are more that could easily be considered "masking" undesirable characteristics. Sorry I just copied and pasted because I am in a hurry. But folks this logic is built into every 737 and any of it could have a "glitch" too.

Speed trim is applied to the stabilizer automatically at low speed, low weight, aft C of G and high thrust. Sometimes you may notice that the speed trim is trimming in the opposite direction to you, this is because the speed trim is trying to trim the stabilizer in the direction calculated to provide the pilot with positive speed stability characteristics. The speed trim system adjusts stick force so the pilot must provide significant amount of pull force to reduce airspeed or a significant amount of push force to increase airspeed. Whereas, pilots are typically trying to trim the stick force to zero. Occasionally these may be in opposition.

Speed Trim System (STS)

An electrical stabilizer trim input automatically controls certain aircraft attitude conditions when undergoing large thrust changes in the lower speed region, such as takeoff and go-around. These conditions require high thrust settings and are especially present with a low weight aircraft and a relatively aft center of gravity where the aircraft wants to “nose up”. The STS supports the crew during these conditions when manually controlling the aircraft without the use of an autopilot by an opposite stabilizer trim, commanding a nose down force by use of the autopilot trim.

STS activates:
– Between 100 KIAS and Mach 0.60 (fading to zero after M 0.68)
– 10 secs after takeoff
– 5 secs after releasing trim switch(es)
– N1 >60%
– Autopilot disengaged
– Trim required

A short manual trim selection overrides the speed trim and will inhibit it for around 10 seconds, just in case that the speed trim inadvertently provides an incorrect input.

The SPEED TRIM FAIL light Illuminates amber:
– accompanied by the FLT CONT annunciator and MASTER CAUTION with a failure of the STS
– after RECALL is pushed together with the FLT CONT annunciator and MASTER CAUTION but extinguishes when Master Caution System is reset with a single FCC channel failure.

The stabilizer speed trim itself (not to be confused with STS) depends on flap position as it is most needed with the flaps extended around the takeoff and landing phase.
When the flaps are up, the low speed trim moves the stabilizer at 0.2 ups (units per second) and when the flaps are extended the high speed trim moves the stabilizer at 0.4 ups.

This stabilizer speed trim is available during autopilot operation, than stabilizer trim speed changes when the flaps are up to 0.09 ups and when the flaps extended to high speed of 0.27 ups.



Mach trim is automatically applied above M0.615 (Classics onwards), M0.715 (-1/200) to the elevators. This provides speed stability against Mach Tuck; i.e. as Mach increases, the centre of pressure moves aft and the nose of the aircraft tends to drop.

And then there is this one which is only in the Max which is what is being blamed for the two crashes,

Maneuvering Characteristics Augmentation System (MAX only) will apply nose down stabilizer trim during high AoA flight when the flaps are up and the A/P is not engaged.

Attached is the "supposedly" the FDR data from Lion Air. If true you can see the pilot fought the manual trim system for over 6 minutes until he let it runaway from him. Everytime the aircraft trimmed down, he corrected and trimmed up until the end. Initially it looks like he put the flaps up, got a sticker shaker and some MCAS trim coinciding with the alleged faulty AOA, dropped the flaps back down (which disabled MCAS trim) and then when he put them back up MCAS kicked in and he fought it for 6 minutes.




After that crash the FAA released an AD (attached at the bottom in a pdf). Note that it does not mention the Max specifically but ALL -800's and -900's. It also "reminds" flight crews what to do if this happens.

This is the checklist dealing with the problems said to have been encountered.





And the switches to flip to turn it off.


Attached Images
File Type: pdf
B737-MAX-AD-1107.pdf (194.9 KB, 12 views)
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Old 03-17-2019, 07:26 AM
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Great explanation and it makes sence to a non pilot.

I may be wrong but this is sounding more and more like a pilot error from lack of training and seat time.
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Old 03-17-2019, 07:55 AM
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Originally Posted by dell30rb View Post
I think a lot of people are hung up on the word stupid. Boeing made a design compromise to save money and make the plane more efficient. They compromised the handling of the airframe to accomplish this and, fixed it with artificial flight stability in a way that is not normally done with airliners. The system was well thought out and FAA Certified. However the system failed in flight and the failure mode was to lawn dart the airplane. For whatever reason (training, no failure notification from the system) the pilots did not figure it out in time to shut off or override the system, and 350 people are dead.

The worldwide grounding of the aircraft with the very limited info we have about this crash lets you know there is a problem. Plane crashed and we found the jack screw indicated significant nose down trim and everyone assumes the MCAS failed again.
Ummm...... yeah I think I have to disagree with you there. Go look up the flight control laws and schemes of any airbus, or 777 / 787. Or any plane. Flight augmentation is nothing new, and allows engineers to design better more efficient airplanes. Sometimes the most efficient aerodynamic design is the least stable w/o computer control. It really seems like the total implementation/training is the issue, not MCAS, not the MAx. We also don't have CVR and CDR data yes, so we don't actually know why the second plane went down. We likely know it, but there a lot more pieces to the puzzle.
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Old 03-17-2019, 08:36 AM
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Originally Posted by ProppedUp View Post
Attached is the "supposedly" the FDR data from Lion Air. If true you can see the pilot fought the manual trim system for over 6 minutes until he let it runaway from him. Everytime the aircraft trimmed down, he corrected and trimmed up until the end. Initially it looks like he put the flaps up, got a sticker shaker and some MCAS trim coinciding with the alleged faulty AOA, dropped the flaps back down (which disabled MCAS trim) and then when he put them back up MCAS kicked in and he fought it for 6 minutes.
Thanks for posting that. Will be interesting to find out if that is the real data or not.

Interesting that the AOA left and right were indicating differences even before takeoff (if I'm reading that correctly) and that the stick shaker was active nearly the whole time, aside from that little dive nearer the beginning. Is the "stick shaker left" and "stick shaker right" really the two physical sticks, or is that two different outputs to the same stick shaker system? Can/do the sticks shake independently, and if so, why?

Also interesting that they appeared to combat the initial dive with flaps, and that seemed to work great (even causing a steady climb), but didn't add any flaps later while they appeared to be fighting trim, even at the 29:23 mark where it appeared they were losing the battle.

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Old 03-17-2019, 08:44 AM
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I have over 7000 hours in the B737 including the Max 8. The problem. as I see it, is a combination of an undocumented aircraft control augmentation system that is capable of overriding pilot control inputs, lack of training, and a control augmentation system that has a single point of failure.

Boeing should have included a description of the MCAS system in the manual, some sort of warning that would indicate that the MCAS was activated, and insured that the corrective action (turn the stab trim disconnect switches off) was a memory item. The lack of training has been exacerbated by the fact that none of the major US operators have a Max 8 simulator, they can't realistically train the pilot to recognize an MCAS failure and have been forced to train pilots "via memo".

Eliminating the single source of failure (the AOA input) should virtually eliminate the chance of the MCAS activating at the wrong time. Combining this with adequate pilot training, will return the Max 8 to the safety record enjoyed by the rest of the 737 fleet.

At least in a 737, there is an option to revert to non-computer assisted flying. An Airbus is always computer controlled and had its share of unexplained crashes where the aircraft flew into the ground regardless of what the pilots did with the controls.
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Old 03-17-2019, 08:53 AM
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Originally Posted by 20biminitwist View Post
Great explanation and it makes sence to a non pilot.

I may be wrong but this is sounding more and more like a pilot error from lack of training and seat time.
Yes unfortunately most aviation accidents are attributed to pilot error but will have/list contributing factors.

So in this case if what is being speculated is true the accident report if it were issued by the NTSB would read something like the cause being the pilots inability to control the aircraft and/or losing control by failing to follow established procedures and checklist.

The contributing factors would be a bad AOA probe which caused the MCAS system to activate and give the wrong inputs.

In any event the ultimate reason for the crash was when the pilots had a problem (runaway trim) the failed to follow a half century old checklist that they were supposed to have committed to memory.

Some may think this is strange or foreign to them but we also have checklist for and engine catching on fire. If you fail to follow that checklist it could turn out bad also.

In other words they crashed a controllable aircraft.
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Old 03-17-2019, 08:57 AM
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Originally Posted by cdrhoek View Post

At least in a 737, there is an option to revert to non-computer assisted flying. An Airbus is always computer controlled and had its share of unexplained crashes where the aircraft flew into the ground regardless of what the pilots did with the controls.
Amen to that. For all those that are freaking out saying they won't get on a Max because a computer controls some small aspect they have no idea that on an Airbus it controls everything and the pilot is merely making suggestions...
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