Re: [FlyRotary] H.P. Fuel
Pumps
Al Gietzen wrote:
Perry
wrote:
If you are flying and
running only one h.p. fuel pump, and that pump fails, the engine will
become silent only milliseconds later!
This is interesting. As my circuit diagram is
currently configured, I have a pressure switch in the fuel system
which automatically turns on the backup pump if the pressure drops
below about 30 psi. (don't remember now the exact setting on the
pressure switch). Do you suppose that this wouldn't react fast
enough to keep the engine running?
There is a manual bypass so I can turn the pump
on if I want. The idea was to turn on both pumps for takeoff,
but at other times the backup would automatically kick in to keep the
engine from stopping if the primary pump stopped; thereby avoiding
rapid heart rates on the part of pilot and passengers.
Al
That's an excellent idea Al. Probably the
best solution. The engine stutters and dies as pressure drops below 20
psi.
I just run both pumps all the time. (I get nervous if I turn one off,
even at altitude). I can tell if one has failed because the pressure
is slightly lower with only one pump on. Those Mazda pumps are
extremely reliable. I use two junkyard pumps that probably had 100k+
miles in cars previously. No failures yet. I've also owned three 2nd
gens with probably 200kmiles accumulated between them and no failures
yet.
--
Perry Mick
http://www.ductedfan.com
I have two pumps and I have
independent double through switches on the pumps and the leading and
trailing ignitions and in low alt critical times on takeoff and
landing I switch one pump and one ignition on the main battery and the
other two on the backup battery so its nearly impossible to have a
sudden fuel or ignition failure that will cause a power
loss.
When at alt I flip both ignitions to
the main and shut one pump down, I use external Bosch fuel pumps, been
running them for years on all my race cars and never had a failure and
never seen a failure in all the years that I had a VW
shop.
Ken Welter
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