It is my understanding (from
David Atkins) is that the spring on the metering pump forces the control
to ‘Low’ position. Since this is a critcal issue if relying upon the metered
system for seal lubrication I (we) would be forever grateful if someone would
verify which way is which.
On a related
subject, a posting on the ACRE list follows:
Dave Atkins claims the apex
seal oil metering system does not work over
8000 feet. He also claims
the engine will run up to three months in automotive service with no apex
seal oil whatsoever. We have some verification of that as George Graham flew
his airplane from Tennessee to New York state while forgetting to
mix two cycle oil with the fuel.
If it be true,
then that also is a bit of a critical piece of information. But ‘why’? The
driving force for the metering system oil flow (as best I can figure out)
is the pressure differential between the ambient atmospheric and the pressure
in the combustion chamber during the intake cycle. This would suggest that
for a NA engine there would always be some pressure to drive the flow.
And it is
consistent that the metering control lever should be at lowest flow for closed
throttle position (greatest pressure differential), and highest flow position
for open throttle position (lowest pressure differential). I’d guess there
is the presumption that the lubrication requirement is only a function of
RPM, and not power output, and the metering control level is for compensation
of the changes in pressure differential.
Al