Pneumatics Question

Get rid of the 4-way connector. *They are unreliable, sometimes
causing cross-talk between paths. *For peace of mind, use separate
connectors.


He mentioned it's a 5 way (although only 4 ports are currently being
used) in another post, which I mean to take is a Winter unit. I've
personally had good luck with those but I still prefer the positive
locking threaded compression connection of my 4 way PZL version. I've
had no leaks with either though, nor any crosstalk (ahem- well just be
sure you didn't x-thread the PZL unit back together on after you show
it off just before takeoff... heh.) Only problems I've heard of with
the quick connects are leaks when the stock O-rings are old/crusty,
which is an easy inspection/replacement (spend the extra $.12 on
Viton!). While crosstalk is possible on the PZL 4-way with it's
compression loaded seals, on the Winter 5-way there is no *real chance
of it as the o-rings form a male seal at least 1/4" into the female
sockets, effectively isolating the individual lines from each other in
case of seal failure, even with dual seal failure. Rubber is not
ageless... and again, silicone (spray, applied via cotton swab) is
your friend, same for the probe/socket...

It's also unlikely a probe connection problem since it is not a double-
probe and I feel safe to assume the probe gets taped at each assembly
of course. Borrowing a probe from another ship will help isolate any
problems with the probe itself it It winds up being suspect.

I may just have tunnelvision but really I think an old vario (with
aged internal seals...) that has pitot and TE seems more suspect of
crosstalk issues than a new Winter quick connect or probe performance
issues...

Slightly OT, I like to use these to seal pneumatic instrument hoses on
barbs:
http://www.jollygerman.com/products/goats/rings.shtml cheap, last
bout 5yrs and gives a uniform 360deg seal (UNlike zipties...) that is
easily future-accessed with no damage to hose/barb. Got idea from
Borgelt but it took me a while to figure out what these little green
rubber Cheerio things were *really* used for... OUCHY!!!

-Paul

It's also unlikely a probe connection problem since it is not a double-
probe and I feel safe to assume the probe gets taped at each assembly
of course. Borrowing a probe from another ship will help isolate any
problems with the probe itself it It winds up being suspect.

The Brunswick socket won't have any internal seals. Just one tube
inside another. Tape is unreliable. A short length of silicon tube
tightly fitted over the joint is better. If the tube can stay in situ
in the trailer then wire it or castrate it with a couple of Cheerios
and leave it well alone.

I may just have tunnelvision but really I think an old vario (with
aged internal seals...) that has pitot and TE seems more suspect of
crosstalk issues than a new Winter quick connect or probe performance
issues...

Seems the first port of call for an elimination exercise. I await some
more real data with fascination.

Whee ! Looks like I'm in for some fun this coming weekend, trying to
figure out what's leaking. I'll probably fly it in the daytime and
try to test it during the evening, or bring the panel home to test the
varios.

I think I was happier before I asked the question... oh well, test it
out and get it working nicely.

Thanks to all for the information and advice; I'll report back when I
figure it out.

-John

On 5/25/2010 7:13 AM, wrote:
On May 24, 9:32 pm, 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

Next question is do they go down when you pull up. If both events
occur, you are somewhat over compensated.
Depending on the type of probe, this may be able to be tuned.
UH


I agree with UH. If you accelerate AND descend the energy added to the
glider is virtually zero and the vario should read zero IF it is
correctly compensated. What you are describing in your original post is
classic TE overcompensation. If this is so, a pull up should produce a
negative vario reading, momentarily.

I realize this is theory and does not "find the leak" if there is one
but perhaps UH's comments will get you going in the right direction.

Good luck,

Paul
ZZ

I've gone over the tubing looking for leaks and it all seems patent.
I pulled everything apart, lubed and reconnected and it's looking good
(including the much-maligned quick-connector). Unfortunately, I
haven't had a chance to fly it to find out if the tubing was my
problem or if it's the instruments (but BOTH varios behaving badly the
same way seems to indicate that it's not the instruments).

On the plus side, one off my club's members is a licenced instrument
mechanic and he's said he'll take a look at my setup when we can get
together. Hopefully that'll get it fixed.

Now, is there some way that I can use this as an excuse to convince my
wife that the "mistress" needs a panel upgrade?