I didn’t think I’d need help with measurement issues,
but I’m hitting some stone walls.
I have a pocket altimeter I thought I’d use but wonder
if it will have a stop on negative altitude. Also I went online to
see how to convert altitude differential to PSID. Not much
luck. The one site I found had conversion formulae that don’t seem
correct. It lists a correlation 1” of mercury to 1,000 feet of
altitude and that should be ok. It then goes on to list a .49
conversion factor to get from inches of mercury to psi.
My calculations show that at a service ceiling of FL290
the altitude difference to 10,000 foot cabin alt is 19,000 feet. .49
times this difference is about 9.5 PSID. That’s WAY higher than the
5.0 PSI we’re supposed to be seeing in the LIVP at FL 290. I had
hoped to test to about 6 PSI.
Short of an altimeter that allows negative readings all
the way to something over 19K and a formula that works, the only other
instrument I can think of is a gauge that reads psi. I found some
online that sell for from a couple hundred bucks to $450 or so. They
all appeared to be set up for plumbing into a pipe system and I don’t know
if they would read correctly if placed inside the cockpit.
How have you IVP builders out there gone about getting
measurements when sealing up the pressure vessel?
Thanks,
John Barrett, CEO
Leading Edge Composites
PO Box 428
Port Hadlock, WA 98339
www.carbinge.com