The TE head generates a low pressure at the sensor holes on the back of the
tube, so that if there is a leak in the system on the flask side of the
Winter vario, then it appears to me that the TE pressure will draw air out
even whilst the glider is holding a steady height. Hence, Winter vario
reads up. Change tubing downstream of the vario and change the flask for
one you have confidence is leak free - best is a replacement flask of the
same kind. Fly the glider again. If the problem persists this may suggest
the leak is with the Winter vario. Flasks can have leaks and tubing can
fracture or be old and not sealing at the barbs on the vario or flask
connections.

The ground problem is either due to needle out of balance or needle zero
setting error I would suggest. These are actually two seperate problems. I
suggest that the adjustment under the faceplate is provided to adjust the
zero needle position as controlled by zeroing springs and after the needle
is balanced. The problem is usually a needle balance problem. Fix a
balance problem by use of paint on the needle. See my posting at the end of
the thread on this topic which appeared starting 27 March 2006.

For completeness I will repeat he
The factors a
1. The state of balance of the needle about the pivot - as affected by
the balance state of the needle.
2. The influence of zero setting springs - as affected by the serated
ring exposed under the little cover at the vario face centre (as with Winter
varios).

When we find that the vario at rest has the needle away from zero (with
Winter variometers usually 0.5 to 1 kt up due loss of solvents from the
white paint, and with PZL ofen down due ?? to luminescent paint absoring and
holding moisture??), what result do we want from our efforts to correct it?
I would suggest we want the outcome to be that the vario needle at rest sits
at zero both with the vario in both upright and inverted (ie rolled 180
degrees about the needle shaft axis) positions.

At rest hold the vario upright and note the needle position, and then hold
it inverted and note the needle position. From that information you can get
an idea as to whether it is a problem of needle balance (1 above) or zero
setting (2 above), or a mix of the two. For example a needle out of balance
of + 1 knot upright will show -1 knot with vario inverted.

Mostly it is a matter of 1 above. In the case of 1, fixing it by using the
zero setting springs via the serated ring will zero the needle with
variometer upright but not inverted! If it is a needle balance problem then
you need to fix the needle balance, not alter the zeroing springs. If you
fix the needle balance, then the needle will not respond to accelerations
during pullups, gusts, etc which is a better outcome.

I use paint placed close to the needle pivot because so little is needed to
produce balance. I use a broken hacksaw blade ground to length (and using
the plain edge not the serrated edge) to engage the ring
and facilitate its removal and reinstallation. Rather than fit the blade
element to a piece of timber to create a tool, I put the blade element in a
bench vise and hold the vario down onto the blade element. Then you get
precise control of the undoing and particularly the doing up force/torque.

Don't give the job to your local club member-gorrilla!

I welcome any contribution to improving the understanding presented above.
Cheers

Roger Druce




"Alan Meyer" wrote in message
...
Last year my Winter mechanical variometer may have read a bit
high, but not very much. Today however, on my first flight of
the year, the vario appeared to read 400 feet high in the air and
about 75 feet high on the ground. With the vario reading 400
feet per minute up, the altimiter wasn't doing anything and the
Cambridge electric vario was reading zero sink.

I've searched the r.a.s. archives and found the advice about
zeroing the needle using the adjustment under the faceplate and
putting a trace of nail polish on the needle to weigh it down.

Do these seem like appropriate repairs for this problem?

Can anyone speculate on why the vario might read so much higher
in the air than on the ground? Is there a plumbing problem I
should look for to explain this?

Thanks for any ideas.

Alan