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alexpeterson(at)earthlink Guest
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Posted: Thu Apr 06, 2006 5:12 pm Post subject: Radios OFF during startup |
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Quote: | >
>The rocket is teaching me lots of lessons. Like: Don't start
the engine
>with your radio on. I tried that last Sunday and was rewarded with a
>blank screen on the SL30. According to the helpful Garmin tech, the
>wiring in the radios will catch some, but not all voltage
spikes, fuses
>don't help and the radios should be kept off during startup. I must
>have been distracted by that Cessna . . .
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What evidence do you have that a voltage spike caused the failure? Could
the thing simply have croaked?
Alex Peterson
RV6-A N66AP 750 hours
Maple Grove, MN
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nuckollsr(at)cox.net Guest
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Posted: Thu Apr 06, 2006 7:58 pm Post subject: Radios OFF during startup |
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At 06:19 PM 4/6/2006 -0500, you wrote:
Quote: |
<BigD(at)DaveMorris.com> Learned] Radios OFF during startup
I guess that would mean that the $150 radio in my car is more robust
than the $3,500 radio in your airplane? I sure don't have an
avionics master switch in my car.
Dave Morris
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Good question. The avionics master switch is still alive
and well in many venues but nobody I've come across can
explain the science or describe the repeatable experiment
that shows why it's 'needed'. It's easy to get folks
to worry about lots of things and then gather a following
that elects to err on the side of caution. The interesting
fact that never seems to carry much weight with the cautious
is that for more than 20 years, folks who qualify equipment
items to run on airplanes at least claim and most demonstrate
they can withstand everything the airplane can throw at it . . .
including transients on the bus due to starter operations.
When we're finished with run-of-the-mill DC power tests.
we bombard electrowhizies with as much as 200 volts/meter RF
interference of two or more kinds. And if that weren't enough,
we'll then hit all the i/o pins with ESD simulations followed
by indirect effects of lightning simulations that put 600 volt
pulses current limited by 10 to 25 ohm resistors into power lines
(24 to 60A potential current flow).
I've shepherded dozens of my own designs and designs of
others through these tests which are rigorous but not
difficult to pass. The idea that any modern piece of
equipment is fatally vulnerable to the inductive kick
of unknown (as yet to be quantified) nature from a
starter motor or contactor just doesn't track the science
that drives current requirements for certification.
Further, there are millions of examples of devices
powered by vehicular DC power systems of all kinds where
operators are NOT cautioned to turn of the device
before starting the engine . . . your car radio included.
Unfortunately, there are just enough anecdotes and
myths floating around to keep the faith in avionics
master switches alive and well. I've had storage
'scopes on dozens of airplanes in situations where
I've been able to watch the bus during startup. I've
never captured a 'spike' of significant amplitude
and certainly nothing that even approached test limits to
which we all subscribe.
Bob . . .
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fvalarm(at)rapidnet.net Guest
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Posted: Thu Apr 06, 2006 8:39 pm Post subject: Radios OFF during startup |
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Is it possible that the radio was somehow affected by a short duration "low"
voltage as the engine drew massive current during start?
Bevan
--
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fvalarm(at)rapidnet.net Guest
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Posted: Thu Apr 06, 2006 9:07 pm Post subject: Radios OFF during startup |
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Does the user guide (for any Garmin or other) actually say to have them
turned off during start?
Bevan
--
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dan(at)rvproject.com Guest
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Posted: Thu Apr 06, 2006 10:15 pm Post subject: Radios OFF during startup |
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Quote: | Is it possible that the radio was somehow affected by a short duration
"low"
voltage as the engine drew massive current during start?
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That's what my GX60 suffers from occasionally. I've never seen my SL30 go
"blank" like the original poster mentioned, but my GX60 does from time to
time. When it happens, the COMM portion is fully functional, I just don't
see anything on screen. A quick off/on with the switch and it's back to
normal (yes, it does a full reboot). On other occasions the GX60 will
reboot during engine start.
I always assumed it was the low voltage that caused this. I've heard other
GX60 owners report similar behavior. Nothing else in the panel is affected,
and no, I don't have an avionics master (my system is an older revision of
Z-11).
FWIW, I have a Sky-Tec LS starter.
)_( Dan
RV-7 N714D (851 hours)
http://www.rvproject.com
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brian
Joined: 02 Jan 2006 Posts: 643 Location: Sacramento, California, USA
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Posted: Fri Apr 07, 2006 6:08 am Post subject: Radios OFF during startup |
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Robert L. Nuckolls, III wrote:
Quote: |
At 06:19 PM 4/6/2006 -0500, you wrote:
>
> <BigD(at)DaveMorris.com> Learned] Radios OFF during startup
>
> I guess that would mean that the $150 radio in my car is more robust
> than the $3,500 radio in your airplane? I sure don't have an
> avionics master switch in my car.
>
> Dave Morris
Good question. The avionics master switch is still alive
and well in many venues but nobody I've come across can
explain the science or describe the repeatable experiment
that shows why it's 'needed'.
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Oh, that one is easy Bob. It is convenient. Some aircraft have a LOT of
radios. My aztec has an audio panel, a GPS/comm, a nav-com, an RNAV
receiver, an ADF, a transponder, an EHSI, a horizontal gyro (separate
circuit from the EHSI, and a music radio. It is a pain the butt to turn
all those on/off switches. It is much more convenient to have one switch
to turn all that stuff on and off. Of course, that one switch can also
turn all that stuff off at the same time when I don't want it to.
When I did the e-bus in my Comanche 20 years ago I added a second switch
that would connect my e-bus (I called it the avionics bus then but it
also had the needle-ball on it too) to the backup battery in case the
main avionics bus switch failed. (At the time it was a SPDT center-off
switch -- yeah, I have learned something since then.)
--
Brian Lloyd 361 Catterline Way
brian-yak at lloyd dot com Folsom, CA 95630
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery
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_________________ Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery |
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nuckollsr(at)cox.net Guest
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Posted: Fri Apr 07, 2006 7:43 am Post subject: Radios OFF during startup |
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At 09:36 PM 4/6/2006 -0700, you wrote:
Quote: |
Is it possible that the radio was somehow affected by a short duration "low"
voltage as the engine drew massive current during start?
Bevan
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If that's the real cause, then the device has some serious deficiencies. Here's
a piece I did on DO-160 testing some years ago for a builder and updated this
morning for posting on my website at:
http://www.aeroelectric.com/articles/What's_all_this_DO160_Stuff_Anyhow.pdf
See paragraph (c)
Bob . . .
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
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nuckollsr(at)cox.net Guest
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Posted: Fri Apr 07, 2006 2:02 pm Post subject: Radios OFF during startup |
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Some folks have reported problems with their email clients recognizing
the address for the piece on DO-160 due to punctuation in the file title.
I've revised the file name and reposted at:
http://www.aeroelectric.com/articles/Whats_all_this_DO160_Stuff_Anyhow.pdf
Bob . . .
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >
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