Wild Vario Needle Swings

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