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paulyg123

FBW and 737 Max trim question

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Looking at cockpit videos of the 737 MAX, I noticed they have those noisy motorized wheel trim controls.  That would drive OCD Pauly crazy.  Is the 737 the only currently built Boeing that has them?  And how come the 737 MAX (such a new plane) uses them, wouldn't a FBW system replace them.  


Paul Gugliotta

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The 737, no matter what version, will always be a 737 classic with a bell, two whistles and a new dress. Other than that it's still the same bones ;-)

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Xander Koote

All round aviation geek

1st Officer Boeing 777

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If you change too much, it requires a new type certificate ($23) and maybe a different type rating ($) instead of completing a training course to qualify in one.


Herman Ross

Seattle, USA

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Afaik the 737 max has FBW spoilers.. but that‘s all. They haven‘t recreated the whole plane, they have adjusted its economical status


,

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The 737 has been the only Boeing in production with noisy trim wheels for a very long time. The 747 Classic had an artificial noise maker to indicate trim motion. The 717 has aural trim motion warning but no trim wheel.

The reason is that back up trim is by manually moving the wheel. The mechanism has to be very low geared so as to be moveable by hand. Hence the rapid and noisy spinning when motorised. Airbus has a much quieter way of doing the same thing. 


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Ok, then what mechanism  does the 757 and 767 use for elevator trim?, are they FBW? and what happens if your tie gets caught in the trim wheel while changing frequncies?


Paul Gugliotta

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Because the MAX is still a 60 year old design with new, big LCD screens wedged into it. It has the same TR as the NG and CL variants.

Regarding FBW, the MAX only has FBW spoilers, just like the 747-8.


 

With kind regards, Bogdan Misko.

 

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8 hours ago, paulyg123 said:

Ok, then what mechanism  does the 757 and 767 use for elevator trim?, are they FBW? and what happens if your tie gets caught in the trim wheel while changing frequncies?

The 757 and 767 have a similar system to the 744 with no trim wheel. It’s stabiliser trim, not elevator trim, by the way. Neither 757 nor 767 are FBW.

I was told you can stop a runaway trim wheel by grabbing it, not that I’ve ever dared to try, so if your tie got caught somehow then you should be able to stop the wheel moving. The 737 trim wheel has retractable crank handles for prolonged manual trimming. What you definitely don’t want to do is run the electric trim with if the handle was left extended.

 

 


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10 hours ago, paulyg123 said:

 and what happens if your tie gets caught in the trim wheel while changing frequncies?

That would be the funniest thing to hear "negative Departure, give us a second. The captain got his tie caught in the trim wheel again":laugh:


All the best,

-John

Milviz Team (posts are of my own opinion)

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29 minutes ago, Milton Waddams said:

That would be the funniest thing to hear "negative Departure, give us a second. The captain got his tie caught in the trim wheel again":laugh:

Well, I'm awaiting the day someone gets WASTED by the yoke AP-inputs on the 777X as he's leaning too far forward to use the new touchscreens...

Like, really Boeing? Touchscreens woth a giant yoke in the way on a FBW aircraft???


 

With kind regards, Bogdan Misko.

 

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23 minutes ago, serviceceiling said:

Well, I'm awaiting the day someone gets WASTED by the yoke AP-inputs on the 777X as he's leaning too far forward to use the new touchscreens...

Like, really Boeing? Touchscreens woth a giant yoke in the way on a FBW aircraft???

I'm sure they'll figure it out, especially once one of their test pilots makes that mistake :laugh:

  • Upvote 1

All the best,

-John

Milviz Team (posts are of my own opinion)

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3 hours ago, VHOEI said:

Ewww...  are you suggesting Boeing simply ditch 80+ years of wonderful, yokes and actually innovates with disgusting sidesticks?! :laugh:

In my opinion, (after being in both Boeing and Airbus Sims - particularly a 744 and A388,) the yokes are much nicer to operate when you "fly" than a sidestick (that is of course, excluding times where you need space in the seat or are trying to enter and exit the cokcpit - then it's horrible) it's heavier and requires more force than a sidestick and I felt that I had more control and that it was more comfortable. (I do recognise the advantages that a sidestick provides but it just isn't as pleasing and satisfying to use IMO.)

Sure, done both as well. Sidesticks are just better for a day to day use, thw whole point of a yoke goes away once you add FBW. Especially with the needed situational awareness of modern jetliners with big screens you don't want to have a yoke infront of you that might block the view. And tbh when handflying you don't look at the yoke or sidestick and think about it, you look eiter outside or at the instruments and make andjustements to follow the desired flightpath. And yes, yokes might feel more old-school and more rewarding due to the heavier feel to them but keep in mind that almost all modern airplanes use artificial feel units do accomplish those forced for feedback. 


 

With kind regards, Bogdan Misko.

 

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On 12/30/2017 at 4:24 AM, paulyg123 said:

Ok, then what mechanism  does the 757 and 767 use for elevator trim?, are they FBW? and what happens if your tie gets caught in the trim wheel while changing frequncies?

The 757/767 use hydraulics to power the stab trim and doesn’t use a wheel. Primary trim is of course controlled via the yoke switches, but the backup is controlled using two switches (similar looking to the yoke switches) to the left of the speed break handle, or with two...levers I guess you would call them. The levers have a lot more travel back and forth and are primarily found on the older aircraft before Boeing converted to the switches. When running the trim in the 757/767, there’s no indication, aural or otherwise, that the trim is moving. You could run it up and down all day and not get a notification unless the trim is doing something it isn’t commanded to do. You’ll get an EICAS message if the trim is moving and not commanded to do so, if it IS commanded but isn’t moving, or if the trim is moving opposite of what is commanded.


Sean Wood

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On 1/5/2018 at 0:17 PM, VHOEI said:

with disgusting sidesticks

haahaaa ... that's a true Boeing fan :D ... i liked it :D hahaa . Boeing all the way man ... Boeing ...:laugh::biggrin::senyum:


Saman Mahdi Abadi 
there is absolute logic in pure illogic ! S.M.A
B1.1 Mechanic

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