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  1. #181
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    Quote Originally Posted by Gordon B. Clarke View Post
    "Moderating" this sub forum has gone politically 180º.

    The main difference between the 2 moderator types is that Metlmunchr kept much more in the background and didn't feel the need to constantly comment and post.
    will comment a lot less even if you ask me a direct question Gordon.
    I

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    Quote Originally Posted by Miguels244 View Post
    Seems weird to have a plane where the trim elements can over power the primary control surfaces.
    Watch the video, the trim moves the complete horizontal tail surface, moving the back edge of that tail surface probably won't counteract that.

    What seams odd is the range of motion that trim has, yet the green zone on the console is so much narrower, almost gotta ask why the trim has the range it does if normal is only +- a few degrees?

    FYI trimmed nose down they sure as hell were not falling out of the sky, merely trying to do a inverted loop and im not sure what altitude that would take to pull that off in a 737, but im pretty certain at most points of a inverted loop hard enough to not hit the ground, your wee wee is definitely flowing up your shirt not down your trouser leg!

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    Quote Originally Posted by Gordon B. Clarke View Post
    "Moderating" this sub forum has gone politically 180.

    The main difference between the 2 moderator types is that Metlmunchr kept much more in the background and didn't feel the need to constantly comment and post.
    FYI whilst you were banned the place was pretty nice, its kinda gone back down hill since your return. Remember, each reply to a post either raises of lowers the std of that thread, your replies of late are akin to the elevator trim adjustments, some point hopefully you bottom out maybe? Equally as a member hes as entitled to post as any of us, he just maybe should be the bigger man and follow the example he set out with about keeping it professional "ish"

    Like most Moderators he has to find his feet, so give him a chance, hes got his hands full with us lot! Even more so with all the different problems way beyond most sane people we bring here. In fact would probaly go as far as to say its probably easier being a mod on some of the insane mental health forums than it is dealing with us bunch!

  4. #184
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    Quote Originally Posted by John Garner View Post
    The earlier-generation 737s were under a dark shadow of vertical stabilizer (aka rudder) control problems that may have led to several falling-out-of-sky episodes.
    The servo valve had a weird failure.
    Two hull losses, a couple hundred souls.

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    Quote Originally Posted by Rob F. View Post
    This is a great (and short) explanation of what happened, thanks for finding it amid all the BS speculation out there.
    His reporting style is kinda nice is it not? Equally it is honest about the tech details that typically interest us lot.

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    Quote Originally Posted by jerholz View Post
    Ok, against my better judgement, I'm going to try to correct some inaccuracies posted here and maybe offer a little bit of perspective.

    First, the 737 is a very stable aircraft with a large flight envelope. It is easy to hand fly. The only time the envelope is small is if you are near the top of it's altitude envelope (based on weight and outside air temp), and that's true of any aircraft.

    No 737 is entirely fly-by-wire. The primary flight controls are hydraulically actuated. There are cables running from the control column to the main wheel well. From there, it's hydraulic. Each primary control surface (aileron, elevator, and rudder) has two actuator on independent hydraulic systems with a third manual (hydraulic for the rudder) backup if they both fail. Starting with the NG models in late 1997, the throttles became fly-by wire. Previously there were cables all the way to the fuel control unit. Now, it's just a potentiometer under each thrust lever and the computer runs the engine. There was one failure of this system (that I know of) that was early on and blamed on faulty firmware. It was fixed. Starting with the MAX, the spoiler system became fly-by-wire (for weight savings, I believe). Spoilers are used for roll control augmentation, extra drag when needed in flight, and on landing to kill wing lift for better braking.

    In addition to elevator control for pitch, the leading edge of the horizontal stabilizer can be moved up and down to trim off elevator control force. There are two motors running a jack screw. One for the autopilot and one controlled by switches on the pilot's control yokes. You can also grab a big wheel on either side of the throttle stand and do it manually. Whenever either motor trims the stab, the big wheel moves. There are stab trim cutout which remove electrical power from the motors.

    MCAS was added to the MAX aircraft. It uses the captain's angle of attack (AOA) vane to determine that a stall (wing reaching critical angle of attack) is imminent and it then runs the stab trim towards nose down for up to 10 seconds. For the record, that's a lot of nose down trim. MCAS only operates with the flaps up and the autopilot off. If the pilot activates the yoke trim switches (which he would naturally do if he were fighting to pull back on the control column), MCAS stops. Once the pilot stops trimming, MCAS can restart if it still detects high AOA. If you turn off stab trim cutout switches, MCAS can no longer function.

    Theoretically, a malfunctioning AOA vane causing a faulty MCAS event is easily recoverable. Obviously, in practice it may not be so easy. You have a hand full of out-of-trim aircraft with possible multiple other loud and confusing aural warnings and the stall warning (stick shaker) going off. Having knowledge of the Lion Air failure makes it much easier for a crew to correctly diagnose and respond to this failure.


    We don't know the cause of the latest accident yet, so let's hold off on the blame game until we do.
    Quote Originally Posted by adama View Post
    Watch the video, the trim moves the complete horizontal tail surface, moving the back edge of that tail surface probably won't counteract that.

    What seams odd is the range of motion that trim has, yet the green zone on the console is so much narrower, almost gotta ask why the trim has the range it does if normal is only +- a few degrees?

    FYI trimmed nose down they sure as hell were not falling out of the sky, merely trying to do a inverted loop and im not sure what altitude that would take to pull that off in a 737, but im pretty certain at most points of a inverted loop hard enough to not hit the ground, your wee wee is definitely flowing up your shirt not down your trouser leg!
    As I said, it seems weird a trim element could over ride the primary control surfaces.

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    Quote Originally Posted by Spinit View Post
    I will comment a lot less even if you ask me a direct question Gordon.
    Huh? If asked a direct question (by anyone) then I'd regard it as a reason to comment - aka "answer". What I posted was what I'm thinking. No comment was necessary by you IMO.

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    Quote Originally Posted by Miguels244 View Post
    BS...
    Im as far from MAGA as you can get, and not shy about sharing.
    Are you running the forum? Just asking ...


    but hey, there are always alternate facts.


    dee
    ;-D

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    Quote Originally Posted by Gordon B. Clarke View Post
    Huh? If asked a direct question (by anyone) then I'd regard it as a reason to comment - aka "answer". What I posted was what I'm thinking. No comment was necessary by you IMO.
    Gordon. My wife tends to think with her mouth open. I use earplugs when I'm trying to concentrate on something. You have a tendancy to think with your hands at the keyboard. Even the ignore function of the forum is of limited use in filtering out meaningful comment from babble.


    What stuck me from Adama's linked video, that I had not realised before and I then checked on the BBC web site, was that the entire Ethiopian Airways flight was about three minutes long and that it seems to have had problems within 10 seconds of take off. With the best will in the world, that's going to give the aircrew a lot more stress in an already busy situation.

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    Quote Originally Posted by Miguels244 View Post
    As I said, it seems weird a trim element could over ride the primary control surfaces.
    Not realy do to the dynamics of flight, the reason they trim with the entire horizontal bit is it is very very efficient aerodynamically. Equally on a plane full of people, if you end up with the rear seats full of shall we say larger people and the front full of smaller ones + variance in cargo, you can end up needing to make a lot of additional lift with the tail or a lot less lift if the weight shifts the other way.

    Trying to do that with just a flap on the rear of a wing - rear of the horizontal needs a big control movement and at that point your then getting lot of drag.

    Got to remember a plane is not a car, were to trim to straight you only need a small correction, in flight everything is very much balanced on a knife edge front to back, you have to generate every single gram of force to balance that weight, that needs far more force at the ext reams of loading than the unbalancing force you need to get the rates of movement you need in a plane to control it. Hence why trim has to have so much more control authority - control power than the flight controls. Which is why i found it so strange one of the previous posters claiming other wise.

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    Quote Originally Posted by adama View Post
    ...Hence why trim has to have so much more control authority - control power than the flight controls. Which is why i found it so strange one of the previous posters claiming other wise.
    What I said is that the pilot can overcome the stick pusher, but it takes effort. And that the trim position does not affect control column travel. I also noted that the combination of the MCAS trimming down, along with the stick pusher may be too much for the pilots to overcome.

    No aircraft that is badly out of trim is easily controlled- not even a Cessna 182. Trimming for any given speed and altitude is necessary on all aircraft.

    The video said this: At the time of impact, the horizontal stab was at the full nose down trim position. That's all it said, and the maker of the video is not on the investigative team, was not there, and does not have any first hand information. So you might want to cool your jets a little, cowboy.

    The jackscrew controls the trim, meaning the AOA of the horizontal stab. It has an electric motor that is operated by the trim switch on the control yoke, and another one that the autopilot controls. There are also cables that go from the trim wheels in the cockpit to the jackscrew for mechanical trim adjustment.

    The elevators are what the control yoke moves, They are hydraulic powered, and if the horizontal stab is out of position by more than the elevators can correct, they are not going to alter the flight path. That's why there are mechanical wheels and electric trim switches on the control yoke to adjust the horizontal stab- that's how the pilot adjusts that jackscrew so that the control column force is neutral in level flight.

    The question is why the pilots did not follow the procedures for the uncontrolled trim condition, or if they did, why it failed. The automatic trim is easily shut off, and the manual trim wheels control the jackscrew directly.

    Also why were they unable to gain altitude- according to that video they never made it above 1000 feet AGL.

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    Quote Originally Posted by Mark Rand View Post
    ...What stuck me from Adama's linked video, that I had not realised before and I then checked on the BBC web site, was that the entire Ethiopian Airways flight was about three minutes long and that it seems to have had problems within 10 seconds of take off.
    That's what got my attention too. They basically rotated right into a stall at about 300 feet above the ground, and just barely recovered from that.

    Was the plane even correctly configured for takeoff?

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    Asiana ......with an instructor in the cockpit !

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    Quote Originally Posted by jancollc View Post
    That's what got my attention too. They basically rotated right into a stall at about 300 feet above the ground, and just barely recovered from that.

    Was the plane even correctly configured for takeoff?
    Hmmm...
    I bet the manifest is in the mix too.
    Weight distribution?

    The overall machine might just be a little twitchy...like a super car with no traction control.

    Dunno.
    I guess we’ll read the report in a year...see the documentary six months later.

    I wonder how long the grounding will last?
    Sooner or later Boeing is going to run out of places to park the new builds.

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    Quote Originally Posted by Miguels244 View Post
    ...I wonder how long the grounding will last?
    Sooner or later Boeing is going to run out of places to park the new builds.
    They're allowed ferry flights, they'll be parking them at Boeing Field and Everett I imagine.

    BEA's looking at the FDR now, I imagine we'll have some preliminary findings pretty quick. The final report- who knows.

    The Lion air flight was 2 minutes into the flight before they started having problems. The Ethiopian flight wasn't even able to climb out. Addis Ababa is a high-altitude airport- 7600 ft. MSL. Hot day, density altitude was probably over 10000 feet.

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    Quote Originally Posted by jancollc View Post
    The question is why the pilots did not follow the procedures for the uncontrolled trim condition, or if they did, why it failed. The automatic trim is easily shut off, and the manual trim wheels control the jack-screw directly.

    Also why were they unable to gain altitude- according to that video they never made it above 1000 feet AGL.
    Yes because all the data so far shows they had plenty of air speed, all most raises the question if there's another element to this, is the jack screw locking at full travel or some how breaking, is there some kinda electrical fault too? Something else that locks the pilots out from recovering this. Does the auto bit some how end up in some kinda fault - cause something else that eliminates the pilots manual and cut off control options on this? IE some kinda short or something that still provides power to the trim system and bridges the electrical disconnects?

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    All this reminds me of something I saw on telly years ago.....Boeing contractor was supposed to be drilling rivet holes with a CNC mill,but was doing the holes with hand drills..............at assembly ,the holes didnt line up,so the assemblers just drilled more holes ....with hand drills......Some bulkheads had multiple unused holes..........somehow missed in quality inspections and maintenance inspections........NOT........if you picked out the fault and held up production,you were fired.

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    Quote Originally Posted by Miguels244 View Post
    Sooner or later Boeing is going to run out of places to park the new builds.
    Well then, Rozen is in good hands, now that you're there with him to hold his ...

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    Quote Originally Posted by jancollc View Post
    That's what got my attention too. They basically rotated right into a stall at about 300 feet above the ground, and just barely recovered from that.

    Was the plane even correctly configured for takeoff?
    This is pure speculation but it seems to me that the flight path characteristics are similar in nature to the problems an airframe has when the C.G. is moving in flight or a C.G. to far astern.

    A lot of times pilot error always goes to the top of the list, then mechanical failure or mechanical problems but the actions of the ground crew or just human ignorance can create situations that even the most skilled pilot or the best engineered system can not cope with.

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    Quote Originally Posted by Ziggy2 View Post
    This is pure speculation but it seems to me that the flight path characteristics are similar in nature to the problems an airframe has when the C.G. is moving in flight or a C.G. to far astern.
    You think it was loaded with Ukrainian mail order brides and they all ran to the back to wave bye-bye ?

    A long time ago they ran semi-cargo 747's to China - the back third was cargo and there was a door. Usually locked.

    But one flight I saw this guy who kept going through the door, then coming back out. He was checking on the horses Seriously, they had about ten horses on the plane. Could have got ugly if they freaked out and started kicking ...

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