Today's Message Index:
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1. 01:19 AM - Re: Wild flights... 22 hr trip in an LSA over the Atlantic... (Werner Schneider)
2. 08:09 AM - differences in fuses versus circuit breakers (Dj Merrill)
3. 09:33 AM - EV200 (al38kit)
4. 09:47 AM - Re: transorbs (nuckollsr)
5. 04:31 PM - Re: EV200 (Robert L. Nuckolls, III)
6. 04:31 PM - Re: differences in fuses versus circuit breakers (Robert L. Nuckolls, III)
7. 05:55 PM - Re: EV200 (al38kit)
8. 06:10 PM - Re: EV200 (Richard E. Tasker)
9. 06:40 PM - Re: differences in fuses versus circuit breakers (Dj Merrill)
10. 07:11 PM - Re: Autopilots vs. "The Right Stuff" (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Wild flights... 22 hr trip in an LSA over the |
Atlantic...
Jay,
I wish them luck, but when I look at their route they can only depart
when very favourable winds are around as the last leg to this Island in
the Atlantic took a bit more then they expected I guess, as with that GS
they will not make it to Brazil!
Good luck and hopefully a proper flight planning!
Werner
do not archive
Message 2
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| Subject: | differences in fuses versus circuit breakers |
Hi Bob,
For the 12v/24v DC circuits typically used in our aircraft, is there
any difference in the rating one would select if using a fuse versus a
circuit breaker? In other words, a hypothetical example, if one arrived
at a value of 15 amps to protect a wire, would a 15 amp fuse be
interchangeable with a 15 amp circuit breaker for protecting the wire?
I ask for two reasons - in a discussion on another mailing list,
someone has said that fuses and circuit breakers of the same rated value
are not interchangeable, and AC43.13-1B table 11-3 on page 11-15 in
Section 4 shows a 15 amp CB or a 10 amp fuse to protect a 16 gauge
copper wire (picture attached).
If there is a difference, do you know and can you explain in simple
terms why?
Thanks,
-Dj
--
Dj Merrill - N1JOV
Glastar Sportsman 2+2 Builder #7118 N421DJ
http://deej.net/sportsman/
"Many things that are unexplainable happen during the construction of an
airplane." --Dave Prizio, 30 Aug 2005
Message 3
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It appears the EV200 is a good master relay...anyone know why it should not be
used as a starter relay...also...?
Al
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=254326#254326
Message 4
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Yes I still have it and I'd be happy to send it to Bob if he wants to take a look.
It's in heat shrink with lead wires sticking out. I haven't molested it yet
- just checked it with a meter. A transorb is basicaly two zeners back to back
and one in this is shorted. It measures a standard diode drop one way and open
the other.
Yes, I'd like to look at it. Please send to Bob Nuckolls,
P.O. Box 130, Medicine Lodge, KS 67104-0130.
Bob . . .
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=254333#254333
Message 5
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At 11:31 AM 7/22/2009, you wrote:
>
>It appears the EV200 is a good master relay...anyone know why it
>should not be used as a starter relay...also...?
To what advantage? This is a contactor that operates for
a few seconds per flight cycle. The el-cheeso parts
have performed well and demonstrated good value. The
EV200 may function well too . . . but what's the
expected return on investment for the more expensive
purchase?
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
Message 6
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| Subject: | Re: differences in fuses versus circuit breakers |
At 10:06 AM 7/22/2009, you wrote:
>Hi Bob,
> For the 12v/24v DC circuits typically used in our aircraft, is there
>any difference in the rating one would select if using a fuse versus a
>circuit breaker? In other words, a hypothetical example, if one arrived
>at a value of 15 amps to protect a wire, would a 15 amp fuse be
>interchangeable with a 15 amp circuit breaker for protecting the wire?
This is a classic example of how AC43.13 offers advice that
is not explained and makes no sense based on the physics.
For example, AC43.13 says their table applies to fuses per
Mil-F-15160. Here . . .
http://www.dscc.dla.mil/Programs/MilSpec/ListDocs.asp?BasicDoc=MIL-PRF-15160
we see that the general spec covers a couple dozen types
of fast acting fuses (1 hour trip at 135%, seconds to few
minutes at 200%). The spec called out is constellation of
FORM/FIT/FUNCTION specs for a variety of fuses.
Now we go look at Mil-C-5806G . . .
http://www.aeroelectric.com/Reference_Docs/Circuit_Breaker/Mil-C-5806G.pdf
This is a QUALIFICATION TEST spec for circuit breakers
of unspecified performance. The poor sap who takes AC43.13 table
11-13, and the specifications called out (gee the talked about
Mil-W-5088 wire too!) will be pretty much in the dark as to how
a considered selection can be made. MOST readers will simply check
to see that the sales brochure for each part under consideration
simply cites these specs . . . without a clue as to how the
part performs to design goals.
> I ask for two reasons - in a discussion on another mailing list,
>someone has said that fuses and circuit breakers of the same rated value
>are not interchangeable, and AC43.13-1B table 11-3 on page 11-15 in
>Section 4 shows a 15 amp CB or a 10 amp fuse to protect a 16 gauge
>copper wire (picture attached).
For our purposes, breakers and fuses are size-for-size interchangeable.
The table cited from AC43.13 is but one of many examples of
poor and/or senseless advice. Please consider running section 11
through the shredder and come here to the AeroElectric List for
advice based on experience and proven recipes for success. The
article at
http://www.aeroelectric.com/articles/wiresize.pdf
speaks to the practical aspects of wire sizing and selection
of circuit protection. For the airplanes we're building,
it DOESN'T need to be complicated.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
Message 7
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If I could get the parts cheap enough, the benefit for me, with two planes, would
be interchangeability...or just having one spare on the shelf.
Thanks for the initial lead, it looks like a great relay, but like you say, can
be pricey...I think I can get them at a little over $40.
Cheers,
Al
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=254422#254422
Message 8
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Uuuh... Because a much cheaper and perfectly adequate solution is
available - the normal el-cheapo starter relay.
The only reason I can see for ever using the EV200 is that it uses less
current when it is energized which might be justifiable for the master
relay. But for the starter relay - how long would it be on when
starting - 2-5 seconds?
Save the money and spend it on gas...
My $0.02
Dick Tasker
al38kit wrote:
>
> It appears the EV200 is a good master relay...anyone know why it should not be
used as a starter relay...also...?
>
> Al
Message 9
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| Subject: | Re: differences in fuses versus circuit breakers |
On 7/22/2009 7:25 PM, Robert L. Nuckolls, III wrote:
> For our purposes, breakers and fuses are size-for-size interchangeable.
Thanks! :-)
-Dj
Message 10
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| Subject: | Re: Autopilots vs. "The Right Stuff" |
At 11:21 AM 7/21/2009, you wrote:
>Yes, with the wondrous capabilities and reliability of today's
>computer controlled machines, be assured that nothing can go
>wrong...go wrong...go wrong....go........
>
>I seem to recall reading about several accidents caused by the
>erroneous actions of computer controlled servo systems; actions that
>couldn't be detected nor corrected by the pilots. Admittedly, these
>were the result of faulty assumptions being built into the
>computer's database by humans. I guess it comes down to "who (or
>what) do you trust?"
Or designing for failure tolerance. Accidents
that follow servo system failures are generally
situations where the pilot did not have his/her
hand on the stick while too close to the ground.
I've had a/p systems hiccup . . . and it's
never pleasant. I wouldn't shoot a coupled
approach without having a hand on the wheel
and a thumb on the disconnect switch. You
need to unhook the autopilot to land so you
can be ready to punch it off when you break out
and/or punch it off when and if it strays.
I worked a FMEA on a Baron accident where the
pilot was in a climb and punched altitude hold
as he approached his assigned level. The autopilot
immediately grabbed pitch and held the desired
altitude. At the same time, it started driving
trim to take force out of the pitch servo.
Unfortunately, the down-pitch relay stuck and
continued to trim down while the a/p servo worked
to keep pitch level. When the pitch servo ran out
of authority, the aircraft nosed down. The pilot
was then aware of a problem. He correctly deduced
a difficulty in the automatic flight control
system and punched the a/p disconnect button.
The pitch servo relaxed and the airplane was
now trimmed nearly full nose down trim. Forces
on the wheel needed to keep the airplane level
would have been high. He was so busy trying
to fly the airplane that he probably didn't notice
the trim situation. This was a smoking hole event
where all of the wreckage ended up in a single
divot.
In years since we've installed pitch authority
limiters in servos (no reason for the a/p to
be more capable than a robust pilot), trim in
motion annunciation signals, and software based
monitors that watch for diverging forces.
The accident was a simple, analog, single channel
autopilot that had a connection to the standard
factory electric trim. The a/p had no way to spot
the stuck relay but was capable of standing off
the effects of divergent forces until they were
too large for the pilot to physically handle
when he told the autopilot to buzz off.
Microprocessors, highly integrated flight
control systems, and lessons-learned have largely
eliminated such events. The forces and rates
in a stepper motor implemented wing leveler
can never over-stress a pilot or an airframe.
Bob . . .
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