Good point about TE probe failure. I've been thinking about adding a Dick
Johnson midship probe. I'll keep my tail mounted probe as a backup.

About battery failure. I've never known of a failure except in very new
(rare) or very old batteries. I had a conversation with a pilot I saw with
three huge batteries under his arm walking toward his glider.
Q. Why so many?
A. They might fail.
Q. How old are they?
A. I dunno, they came with the glider
Q. How long have you owned the glider?
A. 10 years.

Sealed Lead Acid rechargables are really only reliable for three years
whether on the shelf or in use. I start with a fresh one every two years.
I also go through the wiring at least twice a season. So far, no failures.

Bill D


"Chip Bearden" wrote in message
ups.com...
I've always had a backup vario. Some were electric, others mechanical.
Some were completely separate (power, static, TE, pitot), others had a
common point of failure (usually the TE probe and/or electrical bus/
common battery selector switch). I'm not sure there's a perfect answer
although the small, self contained electonic vario with audio/averager
sounds good if you could connect it to a separate TE source.

[On that note, I had a running correspondence with one of the major
vario/flight computer systems last year about offering electronic TE
as a backup option. His contention was that it didn't work as well as
a good TE probe. My point was that if the probe failed (it's happens),
I'd like to have a backup TE vario. We never came to a common
understanding although I think one of the major manufacturers offers
something like this.]

Get something good enough to fly a contest with, not just to limp
home. That way you'll be familiar with it when your primary vario does
fail.

I've had batteries fail with little warning (yes, I have a backup).
The panel-mounted fuse holder came loose at one national contest and
provided intermittant power. One mechanical vario failed suddenly. And
the pressure capsule in my ASI failed at another national contest
which not only gave me no airspeed info but also removed the netto and
speed-to-fly info from my primary vario/flight computer.

If you fly long enough, something will fail. Provide redundancy with
as few common points of failure as possible, then go fly.

Chip Bearden
ASW 24 "JB"
USA