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Changing the mag switches out for emag and pmag

 
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nuckollsr(at)cox.net
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PostPosted: Fri Mar 03, 2006 8:02 am    Post subject: Changing the mag switches out for emag and pmag Reply with quote

At 04:22 PM 3/2/2006 -0600, you wrote:

Quote:


>
>
>>
>> I'm ditching my old Slick mags and going to one Emag and one Pmag. My
>> wiring from switches to mags is from the old Z-9 drawing (same mag
>> wiring as in
>> Z-11). Emagair says that you should switch off power to both the
>> emag and the pmag because there is a drain on the battery when they
>> are powered up, so direct wiring from the battery bus without a
>> switch is out. Both
>> ignitions should be ON during start, as opposed to the disabling of
>> the right mag during startup now. Is there a way to retain the
>> switches I have, including the momentary "start" function on the left
>> mag switch rather than replace the switches with 1-3 switches as in
>> Z-12?

Emags are a unique product in that as the factory points out,
have TWO switchable functions: Power and control. Their installation
manuals suggest separate switches but in a quest for the minimalist
panel, I crafted the drawing for P-Mags at:

http://aeroelectric.com/articles/Rev11/AppZ_R11E.pdf Figure Z-33.

. . . now, be aware that the sequence of switching functions
depicted have been commented on by the good folks at E-magair
suggesting that switch movements should bring power on first
followed by activating the magneto.

My wiring diagram shows the opposite sequence, ignition "active"
first followed by supporting power. The reason is quite simple:
There are separate but divergent interests in the ownership
and operation of the p-mag:

(1) When sitting at the end of the runway doing a pre-flight,
the PILOT'S interest is "are the built in alternators for
each P-Mag functioning?" By wiring as I've suggested,
moving the switch from full up to the mid position deprives
a P-Mag of electrical support and (if the run-up RPMS are
high enough), the ignition will not falter when dropped
to the mid position. Of course, the opposite ignition
needs to be completely OFF at this time.

Pre-flight test would be:

RUN-UP RPM . . . . . Set
L-IGN Switch . . . . . . . OFF
R-IGN Switch . . . . . . . ON but no BAT (mid position)
Note engine does not falter
L-IGN Switch . . . . . . . ON but no BAT (mid position)
R-IGN Switch . . . . . . . OFF
Note engine does not falter
Both IGN Switches . . . . BAT

(2) A secondary interest is what might be called the
maintenance mode for ground ops where the mechanic wants
to have the systems powered but inactive for using a
P-mag's built-in timing features -OR- for hand propping
the engine where again, it's useful to be able to hear
the timing buzzer.

In this mode, you MUST have battery power available to
the P-Mags even when in the inactive state. The diagram
shows a third switch (accessible through the oil check/
filler door?) that places temporary power on both
ignitions while leaving absolute control over activity
in the hands of whoever has access to pilot's controls
on the panel.

If one chooses this architecture, then a light on the
panel should be included to alert the pilot should
the switch be left in the maintenance position. Not
a big risk from a fight operations and safety perspective
but it WOULD run the battery down.

In answer to your specific question, it's my recommendation
that you get a 2-10 switch for the P-mag. Since the E-mag
is electrically dependent, a 2-3 switch to handle both sides
of the E-mag's switching needs is called for. Your existing
mag switches are not suited to this task.

Bob . . .

OOPS! I just noted that a narrative for Figure Z-33 didn't
find its way into the published work. Rats! . . . just sent
Rev 11 back to the printers for another 1000 books. I'll get
the Z-notes updated and publish an errata sheet. I'm glad
you brought up this topic. It showed me where my homework
needs some attention.


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frank.hinde(at)hp.com
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PostPosted: Fri Mar 03, 2006 8:25 am    Post subject: Changing the mag switches out for emag and pmag Reply with quote

Not sure I understand the need for the test switch.

If I understand correctly to enter "Test mode" one simply needs to leave
the P lead grounded (off) and apply power, in this case turn on the
master. Of course now the whole ship is powered up but this seems a
fairly small inconvenience considering that timing is a pretty simple
affair.

Am I correct in my understanding here?

Thanks

Frank
--


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