I don't know if the problem is from a
spool valve, this is the second pump I've had in my plane and both have done
the same thing in warmer weather. And, of course, being in southern California
it's usually always on the warm side.
I can see on the gear pressure gauge
that as the heat goes up so does the pressure. It's gets to a point where the
pressure opens both pressure switches, so when I switch to gear down there's
no connection. One small tap on the dump valve and it releases the excess
pressure on the low side and the pump lites up.
I've seen this same problem with other
Lancairs I fly with but never a solution. There should be a
small expansion tank or relief valve going back to the reservoir on the
low side of the pump. Last resort would be a relay to over ride the low
pressure switch, fed through the high pressure circuit for a momentary
pump start. This would have the same effect as tapping the dump valve for a
second. I'm not sure what the answer is.
Randy Stuart
LNC2