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deej(at)deej.net
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 Posted: Sat Oct 25, 2014 7:32 am Post subject: was RV-14, now brownouts/resets at engine crank |
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On 10/24/2014 11:41 PM, Robert L. Nuckolls, III wrote:
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Brownout resets are not an architecture problem,
they're a radio problem. A radio that DOES NOT
conform to DO-160 guidelines for graceful recovery
after all manner of input power interruptions.
That capability is supposed to be internal to
the appliance, not external . . . and for good
reason. What's the poor C-172 owner supposed to
do when he wants to modernize his avionics but
doesn't want to climb the Everest-of-paperwork
necessary to modify the ship's certificated
electrical system?
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We've had this discussion on the list many times over the past few
years. We can spend days pointing fingers back and forth blaming the
manufacturer or whomever as to why the radio/efis/panel-goodie resets
when cranking the engine, but the simple reality is that we do have
equipment that resets, and going back to the manufacturer and pointing
at DO-160 likely isn't going to get us anywhere in the short term. One
could argue that continually pestering the manufacturer about the issue
might get us somewhere in the long term, but in the meantime we aren't
likely to return our $12,000+ EFIS system because of it, and we need to
move forward.
Comparing to a 172 owner isn't really relevant since we are
primarily talking about experimental avionics going into OBAM aircraft,
and they'll never see the inside of a 172 without highly unlikely and
significant regulatory changes. Again one could argue that regardless
of being experimental or not they should strive to meet some regulatory
specification, but again we are stuck with what we have and if we choose
to keep the equipment we need to factor it in, and move on, much like
when we got an airframe part in the kit that didn't fit just right and
we had to figure out how to make it work and continue building.
Fortunately for us in the OBAM community we aren't limited in that
manner, and are free to incorporate this into the design architecture.
With as many times as this has come up in recent years, it seems pretty
clear that brownout protection is a very desirable feature, and I'd go
so far as to say that it is a required feature for many posters given
the messages we've seen about it.
Yes, we could design a nice whiz-bang external band-aid device that
could be applied to each individual panel-goodie that resets, but as
soon as you have two of them in your panel you've now created
unnecessary complexity and increased component count. Many OBAM
aircraft today have at least two EFIS screens, and often three. Often
the manufacturers solution is to incorporate an internal battery into
each device, which does certainly work, but then leaves us with having
to maintain several batteries throughout the aircraft.
It would seem the more efficient means of addressing this is to
design it into the architecture from the start (pun intended), reducing
battery and parts count, and making the overall system as simple as
possible, and only as complex as it needs to be and no more.
In my humble opinion,
-Dj
--
Dj Merrill - N1JOV - VP EAA Chapter 87
Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/
Glastar Flyer N866RH - http://deej.net/glastar/
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kenryan
Joined: 20 Oct 2009
Posts: 426
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| Posted: Mon Oct 27, 2014 7:31 am Post subject: was RV-14, now brownouts/resets at engine crank |
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If you have two batteries wired so that one is for starting, doesn't that solve the problem?
On Mon, Oct 27, 2014 at 4:43 AM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:
[quote]--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>
For many of us (if not most), experimental airplanes are toys. There are other modes of transportation that are less expensive and safer. And some of these aircraft have expensive avionics (more toys). Pilots want their avionics to work without the annoyance of rebooting during engine start. It is not a matter of what is needed or what is practical. We want to play with our toys without being annoyed with brownouts. I would like to see this discussion deal with a solution that is inexpensive, lightweight and uncomplicated. Topics could include Eric's deslumpifier (capacitors), backup batteries, and DC to DC converters.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=432340#432340
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Tue Oct 28, 2014 5:39 am Post subject: Re: was RV-14, now brownouts/resets at engine crank |
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| Quote: | | If you have two batteries wired so that one is for starting, doesn't that solve the problem? |
Yes it does. So do super capacitors and DC to DC converters. I was just trying to start a discussion about the most elegant way to accomplish brownout protection considering weight, cost, and complexity.
Joe
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