737-800 Aileron Movement
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Joined: Oct 2004
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From: Near sheep!
737-800 Aileron Movement
Hi,
Recently flew return sectors in the pax cabin of a 738.
Was sat on the wing both ways and noticed something intersting about aileron movement.
Scenario:
Sat on the right wing.
A/C banks LEFT.
To return to wings level, the aileron on the right wing lowered slightly as opposed to raising. I doubted myself at first, but observed it again on the return.
Could somebody clarify this? Obviously the aileron on the low ring would lower to return return to wings level, but why didn't the high wing aileron raise, and in fact lower instead?
I am aware of some of the aileron logics built into some of the newer FBW a/c, this was incidentally a brand spanking new 738.
Cheers all...
Recently flew return sectors in the pax cabin of a 738.
Was sat on the wing both ways and noticed something intersting about aileron movement.
Scenario:
Sat on the right wing.
A/C banks LEFT.
To return to wings level, the aileron on the right wing lowered slightly as opposed to raising. I doubted myself at first, but observed it again on the return.
Could somebody clarify this? Obviously the aileron on the low ring would lower to return return to wings level, but why didn't the high wing aileron raise, and in fact lower instead?
I am aware of some of the aileron logics built into some of the newer FBW a/c, this was incidentally a brand spanking new 738.
Cheers all...
Joined: Jan 2010
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From: The moon
It could be to do with the roll spoilers or else near the end of the turn the control column was turned left to level the wings thus causing the aileron on the right wing to lower for a second or two. Then I could be completely wrong.....
Joined: Feb 2009
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From: Virginia
I'm SLF, so I'm sure this will be a learning experience for me. But I'd have thought that to level off from a bank, the pilot would return the stick to neutral, not feed in opposite aileron. It would seem to follow that a little left aileron at the end of a left bank would just mean that the stick hadn't yet been returned completely to neutral.
Joined: Aug 2009
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From: GPS L INVALID
No, the plane would not maintain bank by itself, but return to level flight only very slowly - therefore a little aileron against the turn is necessary to level the wings.
Thread Starter
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From: Near sheep!
Okay, maybe I am slightly misunderstood.
What I am getting at is that maybe it was the LOW wing that was doing all the levelling, and that the high wing was conforming with some form of low drag aileron logic.
Obviously, if you are banking left and give some right yoke to level the wings, you can assume that the right aileron will raise to provide what is required by the yoke.
What I observed on this brand new 783-800 wasn't the case.
What I am asking is does the newer version of the 738 have a form of FBW built in?
What I am getting at is that maybe it was the LOW wing that was doing all the levelling, and that the high wing was conforming with some form of low drag aileron logic.
Obviously, if you are banking left and give some right yoke to level the wings, you can assume that the right aileron will raise to provide what is required by the yoke.
What I observed on this brand new 783-800 wasn't the case.
What I am asking is does the newer version of the 738 have a form of FBW built in?
Joined: Apr 2008
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From: A tropical island.
Is there a chance you were seeing the trim tab in action? Or possibly the aileron returning to it's regular "dropped" position (I forget if that's on the NGs or not, it was on the 200 as an STC)?
IIRC the aileron system is linked together by cables (left and right ailerons), the "action" of one side has a directly related "response" from the other side.
IIRC the aileron system is linked together by cables (left and right ailerons), the "action" of one side has a directly related "response" from the other side.
Joined: Apr 2008
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From: A tropical island.
Sorry STBY, but there are trim tabs (servo tabs, or whatever technical name you'd like to assign them) on the entire 737 line. Furthermore, the aileron trim recenters the artificial feel, it doesn't center the bus drum mechanism.
What do you think drives the ailerons in manual reversion? Take a good look at a picture and try to say there's no tabs on the aileron.
What do you think drives the ailerons in manual reversion? Take a good look at a picture and try to say there's no tabs on the aileron.
Joined: Nov 2007
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From: Texas
There's a world of difference between servo tabs and trim tabs. Granted, Boeing tends to have the servo tabs revert to a trim tab function to drive the control surfaces with a loss of hydraulics.
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From: Seattle, WA
What do you think drives the ailerons in manual reversion? Take a good look at a picture and try to say there's no tabs on the aileron.
There's a world of difference between servo tabs and trim tabs. Granted, Boeing tends to have the servo tabs revert to a trim tab function to drive the control surfaces with a loss of hydraulics.
Negative... Either Balance Tabs with hydraulics or Control (Servo) Tab sans hydraulics.
Joined: Apr 2011
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From: USA, Vermont
WindSheer,
Since you were "sitting" on the right wing, you were throwing off the balance of the aircraft in the roll axis, so no "up"aileron on the right wing would be needed to roll back to the right
. I have to guess the FBW computer was adding some crazy aileron differential to counteract the SLF on the right wing
In all seriousness, I have no clue
. But inquiring minds would like to know.
My limited knowledge of aeronautics tells me you would have adverse yaw if only the aileron on the low wing were deflected downward to roll back to level, but then I don't know if that applies to swept wing jet transports.
latetonite,
I don't quite see how reversed rigged ailerons would result in WindSheers observations. Only the PF would be painfully aware the ailerons were reversed.
I've been involved in R/C flying for 25 years, so I've seen all too many cases of reversed controls being discovered a moment after rotation. They rarely end well, but alt least only someones pride is dinged.
Pete
Since you were "sitting" on the right wing, you were throwing off the balance of the aircraft in the roll axis, so no "up"aileron on the right wing would be needed to roll back to the right
. I have to guess the FBW computer was adding some crazy aileron differential to counteract the SLF on the right wingIn all seriousness, I have no clue
. But inquiring minds would like to know.My limited knowledge of aeronautics tells me you would have adverse yaw if only the aileron on the low wing were deflected downward to roll back to level, but then I don't know if that applies to swept wing jet transports.
latetonite,
I don't quite see how reversed rigged ailerons would result in WindSheers observations. Only the PF would be painfully aware the ailerons were reversed.
I've been involved in R/C flying for 25 years, so I've seen all too many cases of reversed controls being discovered a moment after rotation. They rarely end well, but alt least only someones pride is dinged.
Pete
