Message text written by Tony Renshaw
>I have a desire to use a parallel fuel system too, and have always thought
it
the best way to go since reading an e-mail about it years ago (it might
have
been yours, but I think it was from a guy that would no doubt be flying by
now)<
Yes it probably was me.
> Anyway, I was wondering if the main side can still have a significant
amount of fuel in it when it first swithches over to the reserve, lets say
during a climb, well will it kick in and out when it resenses fuel in the
main
side?<
It is very unlikely you will be in the climb with this fuel state unless
you are on diversion. My system is set up so that the reserve latches on
when it comes on to stop it changing between the two sides. Should main
pump pressure be re-established ( red 'Fuel Pressure' light extinguishes)
the system is reset using a reset button. This is what happens after start
when the main pump comes on line and provides a check of the system. To
continue with your scenario, when you reach top of climb if pressure is
regained from the main pump you could then do a reset.
> If so, how can you be sure the main pump doesn't introduce air into the
upstream side where the good fuel is coming from, or isn't this a problem.<
As soon as the pressure drops the reserve pump comes on line forcing the
NRV closed isolating the main side from the carbs. It helps if the reserve
pump has a slightly higher output pressure than the main so that even if
main pressure is restored you know which pump is in control.
Nigel Charles
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