Scott,
I
hadn’t seen those numbers before but they seem consistent with the
general experience. Even the
Velocity pusher can, with bad luck, suck some exhaust forward if it’s in
the engine compartment, though it’s rare. Generally, there is enough in leakage
around the front nose gear and elevator that air flow is still toward the rear.
Even
though the FAA doesn’t mandate a CO monitor, given their low cost and
dire consequences of an exhaust leak, I wouldn’t leave home without one.
Chuck
I have
yet to hear of an unpressurized high performance composite aircraft with a
positive cabin pressure - even when all the cabin vents are open - even when it
is rear engined.
One of
the tests that should be done in phase 1 is opening the static to the
cabin at cruise and slow flight, with and without vents open to understand the
speed and altitude changes (higher altitude, faster
indicated speed) you will see using such alternate static. It
should be recorded in your POH or placarded.
As I
reported once before, at 180 KIAS, the pressure drop in my cabin is .38"
Hg less or about 380 feet higher at 3000 feet. There is only a .05"
Hg increase when the vent is opened while using cabin static pressure. At
approach speed (110 KIAS), the difference was about .1" Hg. or a 100
foot higher reading. I don't have access to my pressure/air-speed table
and I can't remember the exact speed change numbers.
The
fact that the cabin is alway less pressure than the lower cowling (it is always
more than static) and static means that bad stuff can enter firewall openings
(front or rear engine) or other openings that exhaust fumes pass by.
?