rod

> Of course, one shouldn't forget that a usable vacuum "supply" was
> available without a pump when an external venturi was installed.
>
I was wondering how long it was going to take for someone to divulge the
REAL reason for vacuum instruments. External venturi tubes were the only
form of energy available to drive gyros on airplanes in the 30'3 and 40's
which had no electrical systems. After WW2 here were so many vacuum
instruments out there nobody had the courage to change.

Rod