Any who have read my rantings for long know of my
affection for failure tolerant systems. I've been
watching a thread on electric primers wondering
if anyone would remember some words I wrote in
Appendix Z to the 'Connection which I repeat
here as follows:
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Note 14. Consider installing an electric solenoid valve
between the pressure side of your fuel system and the
primer ports on your engine. Aircraft Spruce offers
a suitable electrically operated valve for primer
service. Further, consider using a 4 or 6 port primer
system (depending on the number of cylinders on your
engine). Two advantages: (1) no wet fuel lines
in the cabin, (2) many an engine plagued with a
plugged carburetor or broken mixture control has
been kept running to an uneventful landing by a
multi-port primer system. This setup will perform
very nicely in such circumstances. Throttle full
open. Tease the boost pump switch as required to
develop considerable power and pick a landing
spot well beyond your normal glide ratio!
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Some of my builders have gone a step further
and installed a needle valve in the line downstream
of the solenoid valve. With a bit of tinkering,
the right combo of needle valve setting and throttle
position was determined for getting 60-75% power
with mixture at idle-cutoff. The also plumbed the
primer valve into its own pump with a separate feed
---From the last-tank-to-drain in their standard flight
procedures.
What results is a totally independent, fuel supply
system that will keep an engine running. One of
my builders was able to use this feature to his
advantage about 8 years ago when the mixture control
on his Long-Ez became detached. He flew an additional
45 mintues to a much more desirable airport where
repairs were quickly accomplished.
Bob . . .
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