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