The brass valve is a pneumatic switch, and lets a calibrated leak through
the capillary (the s/s 'wire') into the flask. connected at the other end
to pitot if using a diaphragm TE compensation, or static if using a probe.
Flow proportional to IAS squared, which approximates to a polar curve for
useful speeds. You then have an ordinary vario with the switch closed, and
a netto (airmass movement) vario with valve open.

Uing the JSW circular slide rule was pretty easy, and surprisingly
accurate, but computery does it all for you now. Nostalgia doesn't make me
want to go back to the old methods.

At 03:46 06 November 2012, Eric Greenwell wrote:
On 11/5/2012 3:36 PM, Tony wrote:
This was in the days when nearly every vario (except for the Ball

series) had a 1/2 liter flask. And when the really fancy final
glide

computers were plastic wheels instead of cardboard. And when real
men

navigated with paper maps! And....

no one had time to look outside while trying to figure out where they
were on the map and if they could make it?



It could be very time consuming figuring out where you were on the map,
then measure distances to your waypoint/airport, decide on a wind
component to use, twirl the "prayer wheel" to the right setting, and
finally discover your arrival altitude.

Shoot, just unfolding and folding the map and switching from one
sectional to the other was a big challenge! Electronic flight computers
eliminated almost all this distraction.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)