Airbrakes Pop Out at 115 kts

[ContestID67]

Each time that I exceed approximately 115 knots, my airbrakes partially
deploy. They come out about 2 inches (5cm) and I cannot seem to get
them to retract unless I reduce my speed, fully deploy them and then
retract them.

Any ideas?

Thanks, John (67R)

[5Z]

What type sailplane?

Many Schempp-Hirth style spoilers will suck open a little as the
springs on the spoiler caps get old and weak. Once lifted up, they may
catch on the wing skin and stay that way until the handle is cycled.

[[email protected]]

Not just Schemmps. Good advice. Check the springs. Also check that
overcenter for the spoiler lock is within tolerance. Don't trust the
annual to uncover such problems.

[Don Hammer]

John,
You didn't say what type of aircraft, but look for air getting into the
spoiler boxes and pushing the top out into the slipstream. I am assuming
they are not unlocking, only the springs compressing.

This often comes from not having a good seal at the wing roots and air
pressure is finding its way through the wing and into the spoiler boxes.
As soon as they come up a bit, the slipstream will catch them and pull the
top out further.

[ventus2]

Sounds like something that should possibly have been picked up at the last
airworthiness inspection.
Spring tension on the airbrake caps can be measured and corrected if need
be. Otherwise, if its the whole airbrake that is extending, then there is
either way too much free play in the system (unlikely) or the overcenter
locking is not working.
Otherwise, if it is only a recent thing, then something has changed and you
should check it before flying again.

Just my thoughts.
Cheers
Chris
Std Cirrus "C2"


"ContestID67" > wrote in message
oups.com...
> Each time that I exceed approximately 115 knots, my airbrakes partially
> deploy. They come out about 2 inches (5cm) and I cannot seem to get
> them to retract unless I reduce my speed, fully deploy them and then
> retract them.
>
> Any ideas?
>
> Thanks, John (67R)
>

[COLIN LAMB]

Maybe the onboard computer has calculated that Vne is approaching and kicks
out the spoilers.

Colin

[Bob Korves]

"COLIN LAMB" > wrote in message
nk.net...
> Maybe the onboard computer has calculated that Vne is approaching and
kicks
> out the spoilers.
>
> Colin

Is this an Airbus glider? 8^)
-Bob

[ContestID67]

Thanks for all the advice. Setting the comments about Vne and Airbuses
aside for the moment...

Yes, these are Schempp-Hirth spoilers on a 21 year old DG-101. What
makes most sense is the springs becoming weak and/or an air leak.

I will order replacement springs from DG. The overcenter for the
spoiler lock was specifically checked at the last annual.

On the air leak - I always carefully tape the wing roots but the
aileron gap seals are shot. I have new mylar seals in hand and will be
installing them in the next few days.

After that work is done I will report back.

Thanks again, John

[5Z]

Also, make sure there's no air going from the fuselage, which is a high
pressure area, out through the control rods. There should be a bellows
made of a soft non-permeable material around the pushrods at the wing
root.

-Tom

[[email protected]]

John,
Have you done the "dime" test?
+ Lift the spoiler cap and slip in 4 or 5 dimes.
+ Close and lock spoilers. If the cap didn't close flush, then the rod
length after the over-center mechanism needs adjustment.
+ If the spoilers did close flush, then you need stronger springs. The
springs on the ends should be about twice as strong as the others.
JJ

[For Example John Smith]

Is there a 3rd possible outcome or is something always wrong with these
things? ;-)
> wrote in message
ups.com...
> John,
> Have you done the "dime" test?
> + Lift the spoiler cap and slip in 4 or 5 dimes.
> + Close and lock spoilers. If the cap didn't close flush, then the rod
> length after the over-center mechanism needs adjustment.
> + If the spoilers did close flush, then you need stronger springs. The
> springs on the ends should be about twice as strong as the others.
> JJ
>

[John Sinclair]

I was responding to a post that stated the spoilers
were popping open at 115 knots, but the dime test should
be done every now and then even though no problem is
noted. If the spoiler caps go flush (with dimes in)
then go fly and put her into a 2-G turn (60 degree
bank) and while holding it in the turn, peek out at
both spoilers. If the caps are lifting, increase spring
tension.
JJ

At 19:00 09 May 2005, For Example John Smith wrote:
>Is there a 3rd possible outcome or is something always
>wrong with these
>things? ;-)
> wrote in message
ups.com...
>> John,
>> Have you done the 'dime' test?
>> + Lift the spoiler cap and slip in 4 or 5 dimes.
>> + Close and lock spoilers. If the cap didn't close
>>flush, then the rod
>> length after the over-center mechanism needs adjustment.
>> + If the spoilers did close flush, then you need stronger
>>springs. The
>> springs on the ends should be about twice as strong
>>as the others.
>> JJ
>>
>
>
>

[Eric Greenwell]

John Sinclair wrote:
> I was responding to a post that stated the spoilers
> were popping open at 115 knots, but the dime test should
> be done every now and then even though no problem is
> noted. If the spoiler caps go flush (with dimes in)
> then go fly and put her into a 2-G turn (60 degree
> bank) and while holding it in the turn, peek out at
> both spoilers. If the caps are lifting, increase spring
> tension.

I'm assuming you aren't referring to just the DG 101, so...

Do the dimes go between the spoiler cap and the top of the spoiler blade?

Is there any chance the dimes will fall out and work their way to a
place we don't want them?

What's the best way to increase spring tension? On my ASH 26 E, I put a
couple washers on the posts that didn't seem to be pulling hard enough
to increase the pre-tension there, which has worked so far, but maybe
there is a better/easier way.


--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

[John Sinclair]

At 22:30 09 May 2005, Eric Greenwell wrote:
>John Sinclair wrote:
>> I was responding to a post that stated the spoilers
>> were popping open at 115 knots, but the dime test
>>should
>> be done every now and then even though no problem
>>is
>> noted. If the spoiler caps go flush (with dimes in)
>> then go fly and put her into a 2-G turn (60 degree
>> bank) and while holding it in the turn, peek out at
>> both spoilers. If the caps are lifting, increase spring
>> tension.
>
>I'm assuming you aren't referring to just the DG 101,
>so...

Yeah, works on all spoilers.

>Do the dimes go between the spoiler cap and the top
>of the spoiler blade?

Yes

>Is there any chance the dimes will fall out and work
>their way to a
>place we don't want them?

You don't leave them in, Eric. Just slip them in,
do the test (close and lock) and then remove them.
If one does slip out, it will be in the bottom of the
spoiler box, fish it out.

>What's the best way to increase spring tension? On
>my ASH 26 E, I put a
>couple washers on the posts that didn't seem to be
>pulling hard enough
>to increase the pre-tension there, which has worked
>so far, but maybe
>there is a better/easier way.

It has been my observation that adding washers doesn't
increase the spring tension and therefore doesn't solve
the problem. A quick & dirty way to do the job is to
fill all the nooks & crannies of the spring with silicone
calking, let it dry with spoilers unlocked. Worked
on the ASW-20's end springs. Nowadays, the ships come
with stronger end springs. A good hardware store may
have an nice assortment of springs. Take in the old
one to judge by.
JJ
>Change 'netto' to 'net' to email me directly
>
>Eric Greenwell
>Washington State
>USA
>