Today's Message Index:
----------------------
1. 07:00 AM - Re: starter switch wiring (racerjerry)
2. 08:29 AM - Re Auto Aux Fuel Pump Circuit Idea (James Kinninger)
3. 03:00 PM - Use of non-aviation Ford-style regulators (Paul Millner)
4. 05:18 PM - Re: Use of non-aviation Ford-style regulators (David)
5. 08:04 PM - Re: Auto Aux Fuel Pump Circuit Idea (Fred Stucklen)
6. 09:34 PM - Purpose of Diodes on Relays (Victor Menkal)
7. 10:42 PM - Re: Purpose of Diodes on Relays (David Lloyd)
Message 1
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Subject: | Re: starter switch wiring |
Most likely you are just reading the magneto internal coil resistance. Disconnect
the P leads and re-measure. You will still see continuity between the magnetos
P lead terminal and ground with P leads disconnected.
The magnetos coils primary winding consists of a small number of turns of wire
wrapped around an iron core. One end of the primary winding is internally grounded
and the other end is connected to the P terminal/stud. The resistance of
the primary winding is very low (not much more than the meter lead resistance)
and difficult to measure using a standard ohmmeter. Slick specifies primary
coil resistance to be between 0.5 and 1.2 ohms (points open / disconnected).
With your ohmmeter, verify that each bare P lead (aircraft wiring) has continuity
between each lead and ground when magneto switch is in the OFF position and
OPEN (no continuity) when in the BOTH position.
If that works, reconnect everything, fire up the engine and do a normal magneto
RPM drop check to verify all is well.
--------
Jerry King
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=360955#360955
Message 2
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Subject: | Re Auto Aux Fuel Pump Circuit Idea |
The original topic seems to have gravitated to the area of vapor locks
and pump placement. That is fine with me and actually makes my below
information applicable.
Here is my question to Don Rivera of Airflow Performance (the maker of
my Aux pump & kit) and his answer:
My question was: " I have return lines to each wing tank. These lines go
through an Andair Value that when turned, changes both the out going
line from the tank as well as the return line. So, can I hook up your
boost pump to take advantage of the plumbing I have in place or should I
abandon it and the expensive Andair Valve?"
Don's response, Nov 19, 2011:
"It would not be advisable to run separate return lines to each tank
when using this boost pump package. Simply tee the return line into the
supply line feeding the boost pump. You can put a tee fitting on the
outlet of the selector valve then on the run of the tee, connect that to
the inlet of the boost pump. Connect the return line from the pump to
the tee part of the fitting on the selector valve. You can use your
trick Andair selector valve for the purge return (that=92s the valve on
top of the engine).
Due to vapor issues it is not advisable to install the boost pump on the
engine side of the firewall (a gascolator is also not advisable to be
installed on the firewall). This is far more a flight safety issue than
installing the boost pump with =93high pressure fuel=94 (30 PSI is not
high pressure) in the cockpit. If the plumbing is installed correctly
and aircraft fuel system practices are followed for plumbing (reference
AC4313-2B) there should be no problem."
Don Rivera
Airflow Performance
111 Airflow Drive
Spartanburg, SC 29306
Phone: 864-576-4512
Fax: 864-576-0201
E-Mail: don@airflowperformance.com
website: airflowperformance.com
Jim Kinninger
jimk@hdiss.net
Message 3
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Subject: | Use of non-aviation Ford-style regulators |
Note that it can be dangerous to use non-aviation Ford-type regulators
in our airplanes.When the alternator half of the master switch is turned
off, the regulator will allow the alternator to go into a voltage
runaway mode, and that overvoltage will not be controlled by your
overvoltage relay (since the field current is flowing via a separate
path, directly from the alternator).The overvoltage condition can cook
your avionics and battery.
Even if you don't turn off the alternator half of the master switch, if
your separate overvoltage relay trip for any reason with such a
regulator installed, that, ironically, will trigger the voltage runaway
scenario.
Paul
Message 4
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Subject: | Re: Use of non-aviation Ford-style regulators |
Uh oh. What's the protection for this? I'm using not a Ford, but a
smaller, denser, lighter Japanese alternator with same output.
David Merchant
Paul Millner wrote:
>
> Note that it can be dangerous to use non-aviation Ford-type regulators
> in our airplanes. When the alternator half of the master switch is
> turned off, the regulator will allow the alternator to go into a
> voltage runaway mode, and that overvoltage will not be controlled by
> your overvoltage relay (since the field current is flowing via a
> separate path, directly from the alternator). The overvoltage
> condition can cook your avionics and battery.
>
>
> Even if you don't turn off the alternator half of the master switch,
> if your separate overvoltage relay trip for any reason with such a
> regulator installed, that, ironically, will trigger the voltage
> runaway scenario.
>
>
> Paul
>
--
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Message 5
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Subject: | Re: Auto Aux Fuel Pump Circuit Idea |
I've given some more thought and testing on the Auto Aux Fuel Pump idea that I
originally posted. I've attached a schematic of a circuit I've bread boarded and
tested. Seems to to work.
The idea/implementation is to automatically turn the pump ON for as long as the
fuel pressure is below a set limit, and don't turn it off until the pressure
has been above that limit for at least 10 seconds. If the pressure go low again,
the process is repeated.
I'm planning on making up a hardwired proto board and actually testing in my
RV-7A, but probably not until after the new year.....
Fred Stucklen
RV-7A N924RV 650 Hrs
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=361007#361007
Attachments:
http://forums.matronics.com//files/auto_aux_fuel_pump_704.pdf
Message 6
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Subject: | Purpose of Diodes on Relays |
I noted that the manufacturer of my ignition switch requests a diode across the
between the excitation (low current start switch) input and ground. Also noted
that Bob calls out diodes on fig Z-16 wiring diagram for the Rotax 912.
Can anyone provide a simple explanation of reason for these? As well Bob did
not call out the diode on Z-16 but assume its the same as the other drawings
which calls for a 1N5400 diode.
I really like Bob's crow bar over voltage module and alternator disconnect relay
which is not included in the standard Rotax wiring schematic. Low cost and
easy to install (following Bob's schematic of course) and covers off one problem
area which a number of Rotax owners have identified with the standard wiring
system and rectifier. Best part is that my ALT switch on the panel is now
gainfully employed (not used following standard Rotax diagram). Over voltage
protection option is also highly recommended by the Rotax guru's at Rotec
Research Canada.
Thanx Vic
CH750 Rotax 912ULS-2
Whitehorse Yukon
Message 7
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Subject: | Re: Purpose of Diodes on Relays |
Not sure if this is what your are looking for....
The diode on some ignition switches provides a small current to the
alternator field to insure that the field gets excited upon start up.
Some alternators do not self start and need a little current to begin
the generation process...
Dave
-------------------------------------------------------------------------
-------
----- Original Message -----
From: Victor Menkal
To: aeroelectric-list@matronics.com
Sent: Thursday, December 15, 2011 9:26 PM
Subject: AeroElectric-List: Purpose of Diodes on Relays
I noted that the manufacturer of my ignition switch requests a diode
across the between the excitation (low current start switch) input and
ground. Also noted that Bob calls out diodes on fig Z-16 wiring
diagram for the Rotax 912. Can anyone provide a simple explanation of
reason for these? As well Bob did not call out the diode on Z-16 but
assume its the same as the other drawings which calls for a 1N5400
diode.
I really like Bob's crow bar over voltage module and alternator
disconnect relay which is not included in the standard Rotax wiring
schematic. Low cost and easy to install (following Bob's schematic of
course) and covers off one problem area which a number of Rotax owners
have identified with the standard wiring system and rectifier. Best
part is that my ALT switch on the panel is now gainfully employed (not
used following standard Rotax diagram). Over voltage protection
option is also highly recommended by the Rotax guru's at Rotec Research
Canada.
Thanx Vic
CH750 Rotax 912ULS-2
Whitehorse Yukon
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