Wild Vario Needle Swings

First flight today in glider with LX 7007 and Winter varios. Needles on both the LED vario and the Winter
mechanical would swing wildly from 10 kts up to 10 kts down all thru the flight- mostly in cruise,
but also in the early phase of thermalling. Needle and LED display seemed synchronous. Both would settle down to give reasonable readings once established in a thermal.


I believe both are plumbed to the same TE probe (an unusually long probe with tee at the end-- not the
usual bent up variety).

Can't be a computer or electrical problem as the Winter would not be affected.

Any suggestions as to cause and fix?

Bill

Hi Bill,

Make sure you don't have the tubes connected to the wrong ports on the
Winter. If the capacity flask is connected to the TE port and the TE line
connected to the capacity flask tubing - that would be bad. I have no idea
if it would cause that problem though.

Best Regards,

Paul Remde
Cumulus Soaring, Inc.
______________________________________

wrote in message
...

First flight today in glider with LX 7007 and Winter varios. Needles on
both the LED vario and the Winter
mechanical would swing wildly from 10 kts up to 10 kts down all thru the
flight- mostly in cruise,
but also in the early phase of thermalling. Needle and LED display seemed
synchronous. Both would settle down to give reasonable readings once
established in a thermal.


I believe both are plumbed to the same TE probe (an unusually long probe
with tee at the end-- not the
usual bent up variety).

Can't be a computer or electrical problem as the Winter would not be
affected.

Any suggestions as to cause and fix?

Bill

On Sunday, March 3, 2013 10:18:02 PM UTC-6, wrote:
Any suggestions as to cause and fix? Bill

Sounds like you have a leak in the TE line and they were both actually sensing static pressure. If hooked up backwards, they will operate backwards. If you had a leak between the capacity and the vario and a good connection between the vario and the TE probe, the vario would go full up and stay there until you land.

Could be a missed connection in the plane, or maybe your probe didn't seal up in the fitting in the vertical tail

Steve Leonard

Agee with Steve, sounds like a T/E leak, could be anywhere from the back of
one of the instruments (or even inside one) to the probe connection on the
fin. You can check if you can get hold of some instrument tubing, a T
piece, a syringe and an old ASI. Connect pilot connection on ASI to one
branch of the T, syringe to another and 3rd to T/E port in fin. Slowwly
push in plunger on syringe, varios should read down. Stop pushing and
varios will com back to zero if no leak and will read up if there's a leak.
Up reading proprtional to size of leak.

At 05:40 04 March 2013, Steve Leonard wrote:
On Sunday, March 3, 2013 10:18:02 PM UTC-6, wrote:
Any suggestions as to cause and fix? Bill

Sounds like you have a leak in the TE line and they were both actually
sens=
ing static pressure. If hooked up backwards, they will operate
backwards.
=
If you had a leak between the capacity and the vario and a good
connection=
between the vario and the TE probe, the vario would go full up and stay
th=
ere until you land.

Could be a missed connection in the plane, or maybe your probe didn't
seal
=
up in the fitting in the vertical tail

Steve Leonard

Could it be a small quantity of water in the tubing, either from
condensation or from washing?


At 04:18 04 March 2013, wrote:
First flight today in glider with LX 7007 and Winter varios. Needles on
both the LED vario and the Winter
mechanical would swing wildly from 10 kts up to 10 kts down all thru the
flight- mostly in cruise,
but also in the early phase of thermalling. Needle and LED display seemed
synchronous. Both would settle down to give reasonable readings once
established in a thermal.


I believe both are plumbed to the same TE probe (an unusually long probe
with tee at the end-- not the
usual bent up variety).

Can't be a computer or electrical problem as the Winter would not be
affected.

Any suggestions as to cause and fix?

Bill

When I was plumbing in my B50, I found some great info on the TE. line under the 'good practices/pneumatic' paragraph. I thought it may be applicable here.
http://www.borgeltinstruments.com/B50man.pdf

Text of paragraph follows:
The most common mistake in variometer installations is to connect two vario systems to one Total Energy line with a T-piece at the instrument panel. The only time that this is permissible is when both instruments are of the pressure transducer type. That is no flasks hence no flow. Flow sensor type instruments cause significant flows in the line to the T.E. probe and these flows can cause these instruments to interact with each other or with a pressure transducer type variometer causing weird behaviour or a general slowing of the response of both instruments connected to the T.E. probe.

The T-piece in the T.E. line should be as close as possible to the T.E. probe although in practice it has been found that if the T.E. line is split under the pilot's seat, further aft behind the seat or near the trailing edge of the wing no problems will result.
end quoted txt

It may be a cause....
~Travis
N4067U

On Sunday, March 3, 2013 10:18:02 PM UTC-6, wrote:
First flight today in glider with LX 7007 and Winter varios. Needles on both the LED vario and the Winter

mechanical would swing wildly from 10 kts up to 10 kts down all thru the flight- mostly in cruise,

but also in the early phase of thermalling. Needle and LED display seemed synchronous. Both would settle down to give reasonable readings once established in a thermal.





I believe both are plumbed to the same TE probe (an unusually long probe with tee at the end-- not the

usual bent up variety).



Can't be a computer or electrical problem as the Winter would not be affected.



Any suggestions as to cause and fix?



Bill

As others have said, this screams leak in the TE line. I had one develop where the canopy goes up and down, bending the lines each time. Hard to find. Connectors are suspects too.
john Cochrane

Check all the tubes for leaks using mild suction rather than positive pressure (don't want to blow a tube off a blind connection someplace back in the fuse) and without the instruments connected. A hand vacuum pump for bleeding brakes is a nice tool for this. It doesn't take much suction to find a leak which would be indicated on the gauge as a steady loss of vacuum.

While it's less likely to be the issue, check the routing of the tubes under the seat pan. If your weight (via the seat pan) is pressing on the tubes then that is also a possibility. If you're seeing some +/- Gs in cruise then that "might" fit the "wildly swinging" observation.

Good luck...be systematic in your approach and you'll find it.

On Sunday, March 3, 2013 8:18:02 PM UTC-8, wrote:
First flight today in glider with LX 7007 and Winter varios. Needles on both the LED vario and the Winter

mechanical would swing wildly from 10 kts up to 10 kts down all thru the flight- mostly in cruise,

but also in the early phase of thermalling. Needle and LED display seemed synchronous. Both would settle down to give reasonable readings once established in a thermal.





I believe both are plumbed to the same TE probe (an unusually long probe with tee at the end-- not the

usual bent up variety).



Can't be a computer or electrical problem as the Winter would not be affected.



Any suggestions as to cause and fix?



Bill

If the receptacle in the fin is designed for Prandtl Tubes, it has two ports. You need to plug the unused port if all you are using is a standard TE probe. Otherwise there's a very big leak.

Best regards,
Craig

On Monday, March 4, 2013 1:59:39 PM UTC-5, Craig Funston wrote:
On Sunday, March 3, 2013 8:18:02 PM UTC-8, wrote:

First flight today in glider with LX 7007 and Winter varios. Needles on both the LED vario and the Winter



mechanical would swing wildly from 10 kts up to 10 kts down all thru the flight- mostly in cruise,



but also in the early phase of thermalling. Needle and LED display seemed synchronous. Both would settle down to give reasonable readings once established in a thermal.











I believe both are plumbed to the same TE probe (an unusually long probe with tee at the end-- not the



usual bent up variety).







Can't be a computer or electrical problem as the Winter would not be affected.







Any suggestions as to cause and fix?







Bill



If the receptacle in the fin is designed for Prandtl Tubes, it has two ports. You need to plug the unused port if all you are using is a standard TE probe. Otherwise there's a very big leak.



Best regards,

Craig

I've seen this problem with my mechanical vario (Sage). For that I installed
a gust filter. I'd already done the split back in the tailboom, making use of
tubing that had connected to a flask back there. I moved the flask up near
the Sage where it belonged.

Checking for leaks is always a good practice. There's articles on doing that
using an ASI and a syringe if you hunt around.

Matt