I believe most a/c with IRUs use them for V/S instead of static.
Interestingly, a pneumatic IVSI, Instantaneous Vertical Speed Indicator, contains a small pendulum that starts tne needle in the correct direction to counter the delay inherent in the basic VSI.
GB
Last edited by Graybeard; 7th Jun 2011 at 16:24.
Reason: correction for IVSI