LS3a Airbrake question

[[email protected]]

I have a problem with my LS3a. During flight, from 90 km/h, on both
wings the airbrakes comming out from the wings slightly (some
millimeters), a little bit higher during ircling flight, during pull-
up and at higher g-loads.
Yesterday I have tried the following during flight:
I have pulled the airbrake handle very slowly back from closed and
locked position untill to the point that I felt resistance and looked
the airbrake covercaps on the wings.
It was interesting that fulling back the airbrake handle 5-I0 mm the
airbrake covercaps went back on both wings to their good positionthe.
I think it means that the over-center (self-closing) is not correct.
Does it mean that the ocer-center is incorrect ? Is there any way to
set the over-center ?

[JJ Sinclair]

It sounds like your spoilers aren't set correctly. They should fully
seat and then pull down on the little springs (under the spoiler cap)
about 1mm or about one dime width. You can check this by pulling up on
the spoiler cap and sliding in a dime. Do this at 4 places along the
spoiler. Then close and lock the spoiler. Now look at the closed
cap.............if it is sticking up anywhere, it did NOT pull down
the required 1mm (dime width). Adjust the linkage, probably at the
spoiler box to make the spoiler pull down more. This adjustment is
made on the rod that goes from the over-center mechanism to the
spoiler, NOT on the rod going TO the over-center mechanism.
JJ
Oh, yeah, remove the dimes from your spoiler box :>)

wrote:
> I have a problem with my LS3a. During flight, from 90 km/h, on both
> wings the airbrakes comming out from the wings slightly (some
> millimeters), a little bit higher during ircling flight, during pull-
> up and at higher g-loads.
> Yesterday I have tried the following during flight:
> I have pulled the airbrake handle very slowly back from closed and
> locked position untill to the point that I felt resistance and looked
> the airbrake covercaps on the wings.
> It was interesting that fulling back the airbrake handle 5-I0 mm the
> airbrake covercaps went back on both wings to their good positionthe.
> I think it means that the over-center (self-closing) is not correct.
> Does it mean that the ocer-center is incorrect ? Is there any way to
> set the over-center ?

[Andy[_1_]]

On Apr 28, 5:36*am, JJ Sinclair > wrote:
>if it is sticking up anywhere, it did NOT pull down
> the required 1mm (dime width). Adjust the linkage, probably at the
> spoiler box to make the spoiler pull down more.

If, as the OP suggests, if the over center mechanism is not set
correctly the spoiler caps may pull down the correct amount and then
relax as the linkage goes further over center.

I had a discussion with Waibel about the airbrakes on my ASW-28. Mine
go much further over center than the factory specs say they should.
The solution is to shim the pad where the over center bell crank
contacts the spoiler box. To find out how much over center there is
at the current adjustment you can put temporary shims on the pads.
Slowly increase the thickness of the temporary shims until the
airbrakes just stay locked. Then remove the temporary shims, measure
them, subtract the factory spec over center measurement, and fix
appropriate thickness shims in place. I used aluminum shims
sandwiched with double sided tape for the temporary shim stack.

I am not familiar with the LS linkage so the specifics for changing
the over center adjustment may be different. However, all over center
mechanisms must use an over center stop and the position of the stop
controls the amount the mechanism relaxes after passing the over
center point.

You will need to know how much over center is required. Reduce it too
much and the airbrakes will come unlocked in flight.


Andy

[[email protected]]

Thanks for your answer, unfortunately I do not understand fully you:
"Then close and lock the spoiler. Now look at the closed
cap.............if it is sticking up anywhere, it did NOT pull down
the required 1mm (dime width). "
It would be nice to discuss it with you off-line, I have a drawing
about the airbrake mechanism from LS, I could send it you.

[[email protected]]

Sorry, I forgot to mention my email:
> It would be nice to discuss it with you off-line, I have a drawing
> about the airbrake mechanism from LS, I could send it you.

[JJ Sinclair]

Recommend you take your LS-3 to a mechanic that understands
sailplanes. Probably not a good idea for unskilled hands to be
adjusting the spoiler caps or over-center stops. Copy the responses
you got, it may help with the adjustment process.
Cheers,
JJ

wrote:
> Thanks for your answer, unfortunately I do not understand fully you:
> "Then close and lock the spoiler. Now look at the closed
> cap.............if it is sticking up anywhere, it did NOT pull down
> the required 1mm (dime width). "
> It would be nice to discuss it with you off-line, I have a drawing
> about the airbrake mechanism from LS, I could send it you.