Today's Message Index:
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1. 04:53 AM - Z-17 battery/ alternator switch (Jeff Point)
2. 05:11 AM - Re: Z-17 battery/ alternator switch (Rene Felker)
3. 05:49 AM - Re: Z-17 battery/ alternator switch (user9253)
4. 08:25 AM - Switch Panel Layout (rvtach)
5. 08:31 AM - Re: Switch Panel Layout (rvtach)
6. 08:48 AM - Re: Re: Z-17 battery/ alternator switch (Robert L. Nuckolls, III)
7. 03:03 PM - Re: Re: Z-17 battery/ alternator switch (iiNet)
8. 06:14 PM - Re: Z-17 battery/ alternator switch (user9253)
Message 1
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| Subject: | Z-17 battery/ alternator switch |
All,
I'm building a simple day/ VFR airplane with Z-17 as the basis for my
electric system. I noticed that the battery/ alternator switch is a
two-throw switch wired as "Off-battery-alternator", presumably to be
able to start on battery power and bring the alternator online once the
engine is running. Other drawings (Z-13/8 for example) use a simple
single-throw switch to bring battery and alternator on together. I've
flown with a Z-13-type system in my RV-6 for 13 years so I have faith in it.
Why the different switch design in Z-17? Is there something about the
PM dynamo alternator that requires it to be off during engine start? Is
it because Z-17 doesn't use a master contactor? Would there be any harm
in starting with the PM alternator online?
Thanks
Jeff Point
Milwaukee WI
Message 2
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| Subject: | Z-17 battery/ alternator switch |
I always thought that the reason for split switches, etc, was so you could turn
off the alternator without turning off the battery. I always start with the
alternator on.......just my 2 cents.
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Jeff Point
Sent: Tuesday, March 7, 2017 5:50 AM
Subject: AeroElectric-List: Z-17 battery/ alternator switch
All,
I'm building a simple day/ VFR airplane with Z-17 as the basis for my electric
system. I noticed that the battery/ alternator switch is a two-throw switch wired
as "Off-battery-alternator", presumably to be able to start on battery power
and bring the alternator online once the engine is running. Other drawings
(Z-13/8 for example) use a simple single-throw switch to bring battery and alternator
on together. I've flown with a Z-13-type system in my RV-6 for 13 years
so I have faith in it.
Why the different switch design in Z-17? Is there something about the PM dynamo
alternator that requires it to be off during engine start? Is it because Z-17
doesn't use a master contactor? Would there be any harm in starting with the
PM alternator online?
Thanks
Jeff Point
Milwaukee WI
Message 3
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| Subject: | Re: Z-17 battery/ alternator switch |
> Would there be any harm in starting with the PM alternator online?
No, in fact that is common practice and is recommended.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=466963#466963
Message 4
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| Subject: | Switch Panel Layout |
Hi-
Some time ago Bob published a sample switch panel layout that showed switches and
labels. I generally copied one of the examples and am now ready to label my
panel but I can't find Bob's drawing. I have searched the archives and found
a link that I think used to put to the drawing but now it just takes me to the
Aeroelectric website and I can't find the drawing there either.
I could come up with my own label wording etc but as usual what Bob showed was
very succinct, clear and concise and they looked really nice.
If someone could help point me in the right direction to find this I would be very
grateful.
Thanks!
--------
Jim McChesney
Tucson, AZ
RV-7A Finishing Kit
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=466967#466967
Message 5
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| Subject: | Re: Switch Panel Layout |
Ok, never mind. After posting this I went back one more time and immediately found
what I was looking for. Go figure. I have spent 2+ hours looking for this.
Sorry to take the groups time. Here's the link:
http://www.aeroelectric.com/Reference_Docs/Misc_PDF/Switches.pdf
--------
Jim McChesney
Tucson, AZ
RV-7A Finishing Kit
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=466968#466968
Message 6
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| Subject: | Re: Z-17 battery/ alternator switch |
At 07:46 AM 3/7/2017, you wrote:
>
>
> > Would there be any harm in starting with the PM alternator online?
>No, in fact that is common practice and is recommended.
Actually, it's six-of-on, half-dozen-of-the-other.
A bit of history:
The first electrical systems to be installed on aircraft
used generators . . . just like the ones on cars, tractors
and trucks. These were simply shunt wound, DC MOTORS being
PUSHED with mechanical energy into the shaft such that they
became GENERATORS.
They required rather sophisticated regulators that not
only maintained the target bus voltage but limited
output current (to prevent commutator and armature
over-heat) and provided reverse current disconnect
so that a NON rotating generator did not revert to
it's roots as a motor and run the battery down after
the engine stopped. These electro-mechanical analogs
to modern electronics are exceedingly clever creations
of the era.
Emacs!
Generators were self-exciting (meaning that they would come
on line with a simple input of mechanical energy (engine running)
and flipping the field supply switch to ON. Further, they
would run well without a battery on line.
Modern starter-generators on turbine aircraft retain traits
of their ancestors and they too run well without having a
battery on line.
Hence, aircraft with any form of generator will generally
have BOTH battery master and generator control switches.
Interestingly enough, the Beech Bonanza STILL has independent
BATTERY and ALTERNATOR switches . . . which is another
story.
When we started putting alternators on TC aircraft (mid 60s)
it was discovered that (1) the alternators did not self
excite at ramp idle rpm and (2) voltage regulation dynamics
were not as comfortable as the generators being replaced.
Cessna (and others) were 'upgrading' the panel styles to incorporate
rocker switches.
Cessna approached Carling to supply a split-rocker switch that
would (1) provide battery and alternator control in one device,
(2) allow battery only operations and (3) prevent alternator
only operations.
http://tinyurl.com/zbo3yg6
Nowadays, many if not most alternators will self excite at
less than cruise rpms . . . voltage regulation dynamics
are improved too . . . so it is less problematic to consider
alternator-only ops. Given the inherent reliability of
the artfully maintained battery, there is really no demontrable
value in planning to accommodate alternator only ops . . . but
it is not outside the realm of possibility . . . indeed, the
POH for Bonanzas (and I think Barons) speak to this option.
Now, how about the differences between the single-throw and
three-throw options depicted in the Z-figures?
EITHER approach is perfectly satisfactory. The single throw
switch prevents alternator-only ops while a PULLABLE circuit
breaker offers a means for breaking alternator field supply
for battery-only ops on the ground. The three throw switch
emulates the split-rocker switch functionality and design
goals adopted by the TC aircraft guys . . . a philosophy
that persists to this day.
MYTHBUSTING: In some circles it has been believed and taught
that turning an alternator ON/OFF while the engine is running
is a bad thing . . . puts lots of stresses on shafts, shear
couplings, gear trains, etc. etc. It has also been reputed
to induce radio zapping transients into the electrical system.
In a word . . . HOGWASH.
I've spent hundreds of hours evaluating alternator/battery/
airplane symbiosis in both in the lab and on airplanes. I've
conducted, witnessed and instrumented hundreds of switching
combinations of battery, alternators and system loads under
the full constellation of conditions.
There is no foundation in physics or practice for the admonition
to start the engine with the alternator switch ON. Leaving
it OFF does relive the battery of about 3A of parasitic load
during cranking . . . a trivial concern.
The short answer: Use which ever MASTER DC PWR switch
philosophy floats ur boat. Either will perform as advertised.
Bob . . .
Message 7
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| Subject: | Re: Z-17 battery/ alternator switch |
Why is it recommended Joe?
Kind Regards, Stu
Sent from my iPhone
> On 8 Mar 2017, at 00:46, user9253 <fransew@gmail.com> wrote:
>
>
>
>> Would there be any harm in starting with the PM alternator online?
> No, in fact that is common practice and is recommended.
>
> --------
> Joe Gores
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=466963#466963
>
>
>
>
>
>
>
>
>
Message 8
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| Subject: | Re: Z-17 battery/ alternator switch |
Recommended so that the pilot does not forget to turn it on.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=466988#466988
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