Check the cutaway picture and info at

http://www.ppavionics.com/FacSolidState.htm

Notice that there is only one model that has a positive shutoff and a
built in check valve to prevent backflow. The others depend on the
valve built into the inlet. Ordinarily I would say that the inlet
valve would prevent backflow but I have seen two cases where it did
not. One resulted in a fuel starvation crash. Apparently the inlet
valve can hang open too easily to bet your life on it. I recommend
that a seperate check valve be used for safety on the models that do
not have one built in.

I also would not consider an application that depends on reverse flow
through the pump.

Bob




In article ,
says...

Are you really sure fuel will flow backwards through the Facet pump? I
may be wrong as it has been a long time since I worked with one of the
se
pumps, but I remember that the design did not allow flow in the opposi
te
direction. I have seen a number of fuel setups that used two pumps in
parallel. With one pump "on" the other pump, the pump that was not
energized, did not allow any back flow. There was no need for a check
valve in the system as the pump acted as its own.

Greg Reid wrote:

I understand that the simple Facet pumps have no check-valve so this
should be possible. But is it harmful to such pumps?


Greg