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