On 05/12/2010 05:17 PM, Donald Duck wrote:
> What faster we fly that more we get lift by wings.
> That is why we have to push more or trim nose down = trim tabs move upp
> when flying faster.
> The stabilators trailing edges move then down.
YES! And the story doesn't end here.
Now, before we go any further, print this out, and take it with you to
the hangar.
Are you there? Fine.
1) Put the trim in the middle, and line up the tailplane and anti servo
tab by rotating the tailplane. If done properly, the tailplane is in
about its "neutral" position when it lines up with the anti servo tab.
2) Now, trim the nose down with your trim button. Anti servo tabs moves
up (assuming you wired everything correctly).
3) Let's play aerodynamics. Your hand is the airstream. The anti servo
trim "sticks out" in the airstream. Push with your hand on the anti
servo tab to imitate the aerodynamic forces.
4) Now LOOK! The anti servo tab goes down. Due to some ingenious
mechanical linking the trailing edge of the tailplane also moves down
(this is why you trimmed the nose down after all).
But most important: The anti servo tab moves faster down than the
tailplane. While pushing the anti servo tab downward, it will at some
moment be in line with the tailplane. Stop when you reach that moment.
This is your newly trimmed out position!
5) Now stare at it for a while, and consider what you just did. Try it
the other way around.
6) Start wondering why the anti servo tab would remain sticking out in
the airstream by itself while nobody is keeping it there. Also try
moving the trailing edge of the tailplane down without the anti servo
tab moving twice as fast downwards as well. It can't be done!
7) Congratulations! You just discovered that an anti servo tab is not a
regular trim tab! A regular trim tab is held in a fixed position and has
no choice. An anti servo tab can move, seek the most convenient
position, and as a consequence take the tailplane with it.
> They have to be un-lined normally, more or less!
>
> If not I am a Donald Duck!
Quack. :-D
> That is why we usually and almost always see them (trimtabs) in
> deflected position only.
> I am sure you will confirm that when you get take more photos.
If the opportunity exists, I will show it to you so you can see it with
your own eyes.
Frans
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