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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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