Pneumatics Question

Hi All,
Whenever I accelerate, my varios bump up and tell me I'm climbing,
then settle back to reality. Any idea of what I need to look for to
fix this?
My setup:
Kestrel 19, two static ports in the tail boom, pitot and TE in the
fin. The TE line is split under the seat using a Y connector and then
travels to two varios (a Winter mechanical and a 1990-era audio/final-
glide called a VariCalc). Pitot and static lines are split behind the
panel using T connectors.
I replaced all the non-permanent tubing last year and they all seemed
to be leak-free.
Thanks!
-John

John,

I don't think you can have more than 1 pneumatic (mechanical) vario
connected to any TE pressure source. Did you have this vario
configuration before you replaced your tubing?

If it's not too much trouble I would try testing each vario
individually, pinching off (or replacing) the Y connector under the
seat so only one vario is connected to the TE at a time.

ted/2NO

On May 24, 6:32*pm, jsbrake wrote:
Hi All,
Whenever I accelerate, my varios bump up and tell me I'm climbing,
then settle back to reality. *Any idea of what I need to look for to
fix this?
My setup:
Kestrel 19, two static ports in the tail boom, pitot and TE in the
fin. *The TE line is split under the seat using a Y connector and then
travels to two varios (a Winter mechanical and a 1990-era audio/final-
glide called a VariCalc). *Pitot and static lines are split behind the
panel using T connectors.
I replaced all the non-permanent tubing last year and they all seemed
to be leak-free.
Thanks!
-John

Did it do this before you changed the non-permanent tubing?

Why was the tubing changed?

Did you do a real leak down test?

I would do the idiot test of confirming you have the vario connected
to the TE line (blow gently onto the the TE probe and confirm you hear
it affecting the electronic vario). But if you've got the static wired
to the TE you would expect the opposite of what you see. That makes me
suspect you have the TE line open to cockpit pressure somewhere. Other
options like a leak across the TE/static circuits with certain types
of TE probe/mount failure would also produce the opposite effect (i.e.
would show sink when you speed up). (And BTW thank you Mr. Greenwell I
was the idiot with the triple probe static port blocked with grease).

The variocalc has no capacity and the winter is connected to a
capacity flask. You rely on line impedance for this not to be a
problem, so good you have the TE line split far away, like under the
seat. The static and pitot lines are (obviously) irrelevant to the
vario.

It could be a TE line open to cockpit pressure. It could be a leak in
one of the varios themselves (less likely, but try taking one vario at
a time out of the pneumatic circuit). If things are leaking/open to
cockpit pressure it is hard to say for sure what they will do as you
speed up, depends on the cockpit venting. Does opening closing vents
do silly things?

I've found a nylon "T" piece once that was cracked wide open and
leaking so check things like that over carefully.

You can exclude the capacity leaking by taking the whole winter vario
out of the circuit, or you can block the capacity port on the winter
(which should then do nothing).

If all that passes, swap TE probes with another glider and test. What
type of TE probe is it?

Darryl

Kestrel 19, two static ports in the tail boom, pitot and TE in the
fin. *The TE line is split under the seat using a Y connector and then
travels to two varios (a Winter mechanical and a 1990-era audio/final-
glide called a VariCalc). *Pitot and static lines are split behind the
panel using T connectors.
I replaced all the non-permanent tubing last year and they all seemed
to be leak-free.

Tailboom static. Prolly used to work OK till you fixed the leaks.
Simple test. Unplug the static tee from the tailboom source and let it
use cockpit air. Fly the ship and try to recreate the creeping
readings while using cockpit static. Lots of older ships had their
tailboom statics relocated due to errors induced at that location. At
least it's an easy test...

-Paul

On May 24, 8:22*pm, sisu1a wrote:
Kestrel 19, two static ports in the tail boom, pitot and TE in the
fin. *The TE line is split under the seat using a Y connector and then
travels to two varios (a Winter mechanical and a 1990-era audio/final-
glide called a VariCalc). *Pitot and static lines are split behind the
panel using T connectors.
I replaced all the non-permanent tubing last year and they all seemed
to be leak-free.

Tailboom static. Prolly used to work OK till you fixed the leaks.
Simple test. Unplug the static tee from the tailboom source and let it
use cockpit air. Fly the ship and try to recreate the creeping
readings while using cockpit static. Lots of older ships had their
tailboom statics relocated due to errors induced at that location. At
least it's an easy test...

-Paul

He has a TE. Neither vario should be connected to a static source. The
old VariCalc I beleive have a single TE connection and is a direct
reading type electronic vario (no capacity flask).

Darryl

Tailboom static.

-Paul

He has a TE. Neither vario should be connected to a static source.

Darryl

POOF! (the sound of me vanishing in a puff of logic...)

What Tuno said......

Mike

On 25 May, 02:32, jsbrake wrote:
Hi All,
Whenever I accelerate, my varios bump up and tell me I'm climbing,
then settle back to reality. *Any idea of what I need to look for to
fix this?
My setup:
Kestrel 19, two static ports in the tail boom, pitot and TE in the
fin. *The TE line is split under the seat using a Y connector and then
travels to two varios (a Winter mechanical and a 1990-era audio/final-
glide called a VariCalc). *Pitot and static lines are split behind the
panel using T connectors.
I replaced all the non-permanent tubing last year and they all seemed
to be leak-free.
Thanks!
-John


A TE system in which the negative dynamic head compensation is exactly
'right' will do just this. It does not not necessarily indicate a
fault in installation. It is generally manifest during vigorous
changes in load factor. A TE vario reflects rate of change in energy
height not actual height so if you pull/push g the change in induced
drag as a result of load change represents a change in energy. e.g.
Pull up and increase load and therefore induced drag and your total
energy reduces which is manifest as sink on your total energy vario.
And vice versa.

Some commercial probes compensate for this by being deliberately not
quite exactly 'right'. Many probes are not spot on because the maker
can't manage it which is almost invariably true of any home made
device or one of poor design such as the Nicks and Braunschweig tubes.
Thus your observation is relatively uncommon.

If your system is truly reflecting your energy changes then try flying
a little more smoothly for you are throwing energy away.

There is no reason why you should not couple two varios to one TE
source but put the Y connector as far away from the panel as possible
to prevent one vario puffing into the other.

To answer some of the questions posed regarding my setup:
- I replaced the non-permanent lines last year because they were quite
old and looking dry. I was also having TE troubles. The replacement
lines tested leak-free (I hooked up a hyperdermic and an ASI, the
speed held when I pushed the plunger). I left the hard plastic
original lines in place, figuring they weren't part of the problem.
- I split the TE line under the seat when I replaced the other
tubing. It was originally split with a "T" at the panel and I read
that this was a no-no (article by Mike Borgelt)
- I tested all the hard plastic lines with the hyperdermic an ASI,
they all held the pressure.
- then traced my original TE troubles to a leak in the 4-way connector
at the panel. Replaced the connector this year.
- I don't recall the varios doing a quick jump when I accelerate.
It's rather reminscent of a "stick thermal" on non-TE varios, lasts
only a couple of seconds
- I'm not doing hard accelerations, at least to my mind. Not feeling
much force on my body
- Winter mechanical has a capacity flask mounted under the instrument
hood. VariCalc has no flask.
- I'm not sure if there were vario changes when I opened or closed the
vents as I wasn't paying attention to that aspect.
- the VariCalc has connections for all three lines; the Winter
mechanical connects to TE and capacity. A problem in static shouldn't
affect both instruments.
- the TE probe is a simple straight out and then bend down, with 2
slots. No idea who made it, but I suspect it came standard from the
Slingsby factory in 1972.

According to Mike Borgelt's article, it's okay (but not best) to
connect two varios to TE, but they should be split as far away from
the instruments as possible. The farthest back I could get was under
the seat, since I'm too big to fit into the boom and all those pesky
control connections were in the way.

I'll try blocking off one vario at a time to see if that changes
things.

The VariCalc has an option for electronic compensation, but I read
somewhere that it's not as good as using a TE line.

. *Replaced the connector this year.

- the VariCalc has connections for all three lines; the Winter
mechanical connects to TE and capacity. *A problem in static shouldn't
affect both instruments.

Faulty multi-connectors can also cause your described symptom as well.
Check the O-rings well, and silicone grease is your friend.

Hmmm, this puts possible tailboom static issues back on the map and
your VariCalc could be cross-talking that or an internal pitot leak
error to your Winter. Run it once with cockpit static before getting
too fancy with time consuming ground testing. It's real easy and you
get to fly... Your vario isolation test will also be useful here, I
suggest unhooking (plug loose lines!) the VariCalc first.

-Paul