Alan Meyer wrote:
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


I cannot explain 325 the 400 F/M error in the air but I think that I
can explain 75 F/M of it.

Previous posts on RAS may have explained this already so if this is
repetitious, my apologies.

The fluorescent material on the needle which
allows it to be visible at night, emits particles and over the years,
loses mass. It therefore eventually reads high. (I have never seen one
read low on the ground but it may be possible). There is an adjusting
screw behind the glass and has enough range for one or two adjustments
before it requires more fluorescent paint to put it back into range.

Paul