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Bill/Ed,
I guess I should have mentioned that the fuel system has a manual overide. It can be set to primary, secondary, or auto. It will take some time for me to determine just how to best operate the system in the various flight modes.
Ed, good point on the location of the pressure sensor. It is located just after the two EFI filters. The only thing between the sensor and the injectors is a couple feet of braided SS hose and the fuel rail. I'm comfortable with that location.
Ed, thanks for the feedback.
Mark
________________________________
From: Rotary motors in aircraft on behalf of Ed Anderson
Sent: Sat 11/25/2006 8:28 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Z-19 questions
Bill, Mark has a good approach. The only part I might take exception to is
the "Automatic" switching of fuel pumps should pressure decay in one.
While, the automatic mode switching would undoubtedly be quicker than a
human response to the failure of a fuel, pump. It requires several
additional components which could fail and what perhaps bothers me more - it
removes the pilot from the decision loop.
I have not seen the design so can't comment on it - except to say that
adequate Fuel pressure does not necessarily equate to adequate fuel flow.
Depending on where the pressure sensor is relative to the pumps, its
theoretically possible to have a partial blockage after the sensor and still
show "good" fuel pressure - but, have inadequate fuel flow. Unlikely, I
know, but I always look for the unexpected failure modes.
Personally, I prefer to have the two EFI fuel pumps each with their own
switch. Switch both ON for take off and landing and you have your bases
covered. This approach does have a weakness compared to the automatic switch
approach that Mark is using - if you forget to turn both on and have the
primary fail -- it will take some finite amount of time for the pilot to
recognize the failure, diagnose the reason and switch on the other pump.
That is why it is a "check-list" item for me for both pumps to be ON prior
to take off/landing.
If both pumps fail then, whether automatic or manual, - its just not
going to be your day.
This is a personal view point, of course.
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://members.cox.net/rogersda/rotary/configs.htm#N494BW
http://www.dmack.net/mazda/index.html
----- Original Message -----
From: "Mark R Steitle" <mark.steitle@austin.utexas.edu>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Saturday, November 25, 2006 8:56 AM
Subject: [FlyRotary] Re: Z-19 questions
Hi Bill,
Have you checked out Aero-Electric's Z-14 architecture? Dual alternators,
dual batteries. The two PC-680 Odyssey batteries are independent of each
other, but can be connected by flipping a crossover switch on the panel in
the event of an alternator failure. The second battery automatically kicks
in during starting. This is what I did on my ES and it seems to be working
pretty well so far (10 hrs of ground running, no flight time, yet).
One modification I made to the Z-14 design (at the suggestion of Ed
Anderson) was to put all the engine critical items on a separate "always
hot" bus, with breakers. Each fuel pump has its own breaker, leading and
trailing coils have their own as do the primary and secondary injectors.
I also used dual EFI fuel pumps, plumbed in parallel. They feed into two
stainless GM efi filters. The pumps are controlled by a pressure switch and
relay. In other words, they are both switches are on, but only one pump is
running during normal operation. In case of a low pressure event (pressure
sag), the relay turns the second fuel pump on before you can say "wazzzzup".
It also lights an LED on the panel to tell you that the boost pump is
running. You must manually reset it back to single pump mode. This is the
Eggenfelner design and you can get part numbers and schematics on their
site, if you're interested.
Mark S.
________________________________
From: Rotary motors in aircraft on behalf of Bill Bradburry
Sent: Fri 11/24/2006 7:45 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Z-19 questions
OK, This is my fall back position. I have posed this question on the
Aerolectric list for a couple of days and no answer. (although the email
did get caught up in an embarrasing event!) 90% of you guys have
already wired your planes and followed Bob N's advice, so how did you do
the redundancy on the fuel pumps, coils, and injectors?
from the AE list:
"I am installing a fuel injected Mazda rotary engine and trying to follow
the Z-19 guidelines for dual battery, single alternator. Looking at the
engine primary and secondary circuit, I need to install a primary and
secondary fuel pump, plus I want to power the coils and the injectors
off of the battery buss.
How should I do this? I suppose I could take the fuel pump diode output
and switch it to either of the two fuel pumps???
What about the coils and injectors? Should I set up similar circuits
for them, or is there a better way to reduce parts???
I would appreciate any guidance you guys could give me.
Thanks and Happy Thanksgiving!
Bill B
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