Today's Message Index:
----------------------
1. 01:47 AM - Larger D-Sub pins (Stuart Hutchison)
2. 02:32 AM - Re: Antenna Installation Question (Jared Yates)
3. 06:05 AM - Instrument Earth Bus cable size (MikeDunlop)
4. 06:19 AM - Re: Instrument Earth Bus cable size (user9253)
5. 06:28 AM - Re: Weak and Static on Transmission (user9253)
6. 06:55 AM - Re: Instrument Earth Bus cable size (George, Neal Capt 505 TRS/DOJ)
7. 07:20 AM - Re: Instrument Earth Bus cable size (ROGER & JEAN CURTIS)
8. 07:22 AM - Re: Re: Weak and Static on Transmission (Bill Bradburry)
9. 07:56 AM - Re: Larger D-Sub pins (John Grosse)
10. 08:39 AM - Re: Larger D-Sub pins (Stein Bruch)
11. 08:53 AM - Re: Fuses instead of breakers (Robert L. Nuckolls, III)
12. 09:08 AM - Re: Larger D-Sub pins (John Grosse)
13. 09:08 AM - Fuses instead of breakers (Dennis Johnson)
14. 09:13 AM - Re: Antenna Installation Question (Robert L. Nuckolls, III)
15. 09:27 AM - Re: Fuses instead of breakers (Ed Holyoke)
16. 09:29 AM - Re: Larger D-Sub pins (Robert L. Nuckolls, III)
17. 09:47 AM - Re: Instrument Earth Bus cable size (Robert L. Nuckolls, III)
18. 09:48 AM - Re: Fuses instead of breakers (Robert L. Nuckolls, III)
19. 10:00 AM - Re: Fuses instead of breakers (Robert L. Nuckolls, III)
20. 02:11 PM - Re: Instrument Earth Bus cable size (MikeDunlop)
21. 02:29 PM - Re: Fuses instead of breakers (Jeff Page)
22. 06:40 PM - Re: Fuses instead of breakers (bcondrey)
23. 06:52 PM - Re: Re: Fuses instead of breakers (Robert L. Nuckolls, III)
24. 06:55 PM - Re: Re: Fuses instead of breakers (Robert L. Nuckolls, III)
25. 07:51 PM - Re: Re: Fuses instead of breakers (Jeff B.)
26. 08:31 PM - Re: Re: Fuses instead of breakers (Robert L. Nuckolls, III)
Message 1
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Subject: | Larger D-Sub pins |
G'day all,
Has anyone found a convenient after-market supplier for the D-Sub pins with
an oversize butt that Garmin include in some installation kits? The Garmin
part number is 336-00023-00 and they're physically longer with a larger
crimp cup to fit 18 AWG wire ...
I want to parallel looms into a single connector ... and it seems that
paired 22 (and perhaps 20) AWG wires will fit in these pins. Sadly I only
have three of them :)
Kind regards, Stu
F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY
www.teamrocketaircraft.com
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Wednesday, January 25, 2012 3:08 PM
Subject: Re: AeroElectric-List: Re: Antenna Installation Question
--> <nuckolls.bob@aeroelectric.com>
At 08:36 PM 1/24/2012, you wrote:
><Tom@CostanzaAndAssociates.com>
>
>
> > the teeth of the lock washers should bite through any
> paint/primer into the surface of the skin.
>
>
>Thanks Charlie. I know this makes a good D.C. ground, but I'm not sure
>how well it grounds at 100+ MHz. Maybe Bob could speak to that.
It's nigh on to impossible to get the 'ideal' bond between antenna base and
skin without welding it. Further, adding a cork gasket under the base puts a
'resilient'
material in the stack-up of parts under 'crush'. See:
http://aeroelectric.com/Pictures/Antenna/Comm_Antenna_Installation.gif
Since all electrical connections MUST come though the mounting hardware,
getting the highest practical make up forces goes directly to gas-tightness
of the connections at interfaces marked with (*). All this happens within a
few tenths of an inch of the center of each screw. Taking all the paint off
skin under the antenna adds nothing.
I'd pitch the cork. Drill out the base holes to take at least a #10 screw
(if not already that large). Clean the mate up surfaces marked (*) to
bright. Run a thin bead of RTV around the perimeter of the base before
pressing it into place on the aircraft.
Tighten the screws to spec limits. Using grade 8 hardware will let you get
some real, lasting pressure in the joints.
Bob . . .
Bob . . .
Message 2
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Subject: | Re: Antenna Installation Question |
I fly airplanes in the high flight levels and even there we use the top antenna
primarily. I've thought about it before, and I think a "to scale" diagram would
explain why. Even though 5-6 miles seems high by altitude standards, it's
not very far laterally. If the rco or tower is 20 or even 100 miles away, the
acute angle in the triangle is small. To visualize more easily, think of the distance
in feet instead of miles. The angles are the same regardless of the units
of course. If you stood 5 feet below your antenna's base and 100 feet away,
would the antenna be visible? Likewise at 20 and even 5 feet, it is probably
visible from most angles. If it is blocked by the wing or some other piece of
airplane, then it will likely not be for long in flight.
On Jan 24, 2012, at 21:29, "Noel Loveys" <noelloveys@yahoo.ca> wrote:
>
> The cork gasket goes directly under the antenna, between the antenna and the
> skin to prevent water from penetrating the skin under the base. The antenna
> grounds through the washer and mounting nut inside the skin. This is
> important as this is a ground plane for the antenna. Clean off the alodine,
> or zinc chromate from inside the skin around where the mounting nut and
> washer grip the inside of the skin.
>
>> From here I'm assuming that you have a cloth plane...
> Cloth planes usually have a frame structure under the cloth physically
> strong enough to hold a com. ant. but you may need to install you own foil
> ground plane. If this is your case then make sure your ground plane is well
> grounded through the outside of the antenna connector or preferably the
> mounting nut.
>
> Small planes generally have their com antenna on top of the plane... away
> from landing gear and other parasitic elements like landing gear. Being on
> top is adequate to talk with towers and a good location to communicate with
> other aircraft. If you expect to fly above FL2.0 you may need a com Ant on
> the bottom of your plane to contact ATC.
>
>
> Noel
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
> tomcostanza
> Sent: January 24, 2012 8:57 PM
> To: aeroelectric-list@matronics.com
> Subject: AeroElectric-List: Antenna Installation Question
>
> <Tom@CostanzaAndAssociates.com>
>
> Hi,
>
> Comant instructions for a comm antenna installation says to mount the
> antenna base directly to the skin for proper electrical bonding. Makes
> sense to me. Then they include a cork gasket with the antenna. Any
> suggestions?
>
> I was planning to alodine the skin under the antenna base. Should I put
> dielectric grease or anything else between the base and the skin?
>
> --------
> Clear Skies,
> Tom Costanza
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=364738#364738
>
>
>
>
>
>
>
>
>
>
>
>
>
>
Message 3
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Subject: | Instrument Earth Bus cable size |
Starting a new topic to avoid confusion with previous attempts at a simple explanation.
I'm building a Long-EZ with a Odyssey PC925 battery in the nose section, there
is one 0.5 inch copper tube conduit that runs from the nose section to the firewall
at the rear.
The positive cables (# 2 welding cable) will run from the battery to the master
switch in the nose section (6 to 7 inches), from the master switch through the
earth conduit to the starter solenoid way back on the firewall (about 10 ft),
then from solenoid to starter.
The earth cable (# 2 welding cable) will run from the battery to the copper tab
on the front of the earth conduit, just behind the nose section (20 inches).
The earth is then picked up from the rear copper tab of the earth conduit, on
the engine side of the firewall, by means of a copper braided strap between conduit
and engine. So I presume (dangerous thing to do!) the cranking current runs
through the copper conduit.
My question is:
What is the minimum size cable can I use from the copper tab on the FRONT of the
earth conduit tab (just behind the nose section) to the instrument earth bus
(approx 18-20 inches in length). I'm trying to avoid using the very heavy welding
cable.
Copper Tube Conduit
-----------------------------
Bat Pos ++++++++ # 2 welding cable ++++++++++
-----------------------------
Bat Neg ---------|Tab| |Tab|----- Neg (firewall side)
|
|#?
|
Instrument
Earth Bus
MikeD (U.K.)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=364793#364793
Message 4
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Subject: | Re: Instrument Earth Bus cable size |
> My question is:
> What is the minimum size cable can I use from the copper tab on the FRONT of
the earth conduit tab (just behind the nose section) to the instrument earth bus
(approx 18-20 inches in length).
Use the same size wire for the negative as is used for the positive supply to the
instrument panel.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=364795#364795
Message 5
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Subject: | Re: Weak and Static on Transmission |
> When I first flying my new home built airplane it was fine, crystal clear both
transmission and receiving. However, something changed, now I can hardly understand
transmissions. I haven't yet been able to put my finger on what's changed
and causing it. jerryb
The vast majority of electrical problems are caused by bad connections. I suggest
that each connection be disassembled, mating surfaces cleaned, and fasteners
tightened.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=364796#364796
Message 6
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Subject: | Instrument Earth Bus cable size |
Mike -
It depends. Have you worked a load analysis for the equipment that
would be serviced by the panel ground?
Referring to the wire chart in The AeroElectric Connection, Chapter 8, a
length of #8 copper wire is expected to carry about 22 amps continuous
with less than 10-deg C rise in the wire temp.
neal
-----Original Message-----
From: On Behalf Of MikeDunlop
My question is:
What is the minimum size cable can I use from the copper tab on the
FRONT of the earth conduit tab (just behind the nose section) to the
instrument earth bus (approx 18-20 inches in length). I'm trying to
avoid using the very heavy welding cable.
MikeD (U.K.)
Message 7
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Subject: | Instrument Earth Bus cable size |
My question is:
What is the minimum size cable can I use from the copper tab on the
FRONT of
the earth conduit tab (just behind the nose section) to the instrument
earth
bus (approx 18-20 inches in length). I'm trying to avoid using the very
heavy welding cable.
Mike,
It appears that the current running through this wire is
only that used in the instrument panel. You really need to add up all
the
loads from the avionics, lights, and other electrical devices that
connect
through this ground, then calculate the conductor size. Your + feed
wire
should be of the same gauge.
Once you know the total load you can see Bob's Wire size
calculator here: http://www.aeroelectric.com/articles/wiresize.pdf
Hope this helps.
Roger
Message 8
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Subject: | Re: Weak and Static on Transmission |
Jerryb,
The engine is a Mazda Renesis rotary. It is a 4 stroke engine but has no
valves, so it is somewhat like a two stroke. The voltage regulator is a
Transpo V1200. I am trying to use a ICOM IC-A6 handheld radio with little
or no success.
My problems are evolving as well. I was previously getting "5 by 5"
responses from the tower on radio checks. Now it is "weak but usable". The
first flights were uneventful as far as radio communications go. I could
hear them and they could hear me. Not so much now. As far as what has
changed.well, I have been building on this plane for years!
Bill B
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of jerb
Sent: Wednesday, January 25, 2012 12:30 AM
Subject: RE: AeroElectric-List: Re: Weak and Static on Transmission
What kind of engine, if 2-stroke and using a voltage regular what brand is
it, also what brand/model hand held radio are you using? I have almost the
same identical problem.
When I first flying my new home built airplane it was fine, crystal clear
both transmission and receiving. However, something changed, now I can
hardly understand transmissions. I haven't yet been able to put my finger
on what's changed and causing it.
jerryb
At 09:51 AM 1/22/2012, you wrote:
<nuckolls.bob@aeroelectric.com>
At 07:38 AM 1/20/2012, you wrote:
<bbradburry@bellsouth.net>
Well, to further clarify this problem. I seem to be able to hear ok on the
ground while taxiing around the airport, but after I leave the airport the
reception gets really bad. At first I thought it was a problem with the
approach frequency because that is where it would first start up. It was a
loud hiss in the headphones so loud that I could not hear ATC. In fact, I
have made two NORDO landings as a result on this loud hiss. I sent my radio
back to have it checked out and nothing was found. All this trouble is at
below 5000 ft and fine weather. I am flying off my 40 hours (22 so far) and
am only flying in good weather. These radio problems at a Class C airport
have made me afraid to fly. ATC could take some action against me if it
continues.
This is the first time I've been aware that you were having
problems both with hearing and talking. While the ground
listeners complain of "static" you have described the extraneous
audio as a "hiss". We may be talking of two different problems.
I'm having trouble resolving a single noise source that would
manifest in both what you hear and what is transmitted to the
ground.
Get a hand-held transceiver and use it to 'probe' around
the airplane. Use tune the hand-held to an unused frequency,
open the squelch and open the volume to get a low level of
no-signal hiss common to all receivers. Then probe around
the panel mounted goodies and wire harnesses with the
hand-held's antenna. See if the no-signal hiss changes
in level with the master switch on versus off. If it does
change, turn off accessories and/or pull breakers/fuses to
see if any one accessory produces a noticeable change
in noise from the hand-held.
You can use the hand-held as an airborne signal quality
sniffer too. Use a headset with the hand held to listen
to your own transmitted signals. You may have to take the
antenna off the hand-held to avoid overloading the hand-held
receiver. You don't need to talk on the ship's radio, just
listen to your transmitted signal to characterize the noise.
Is it the same "hiss" you hear in your received signals?
In any case, carry the hand held to avoid the no-radio
return to the airport. In fact, having the 'three musketeers
of dark-panel ops' in your flight bag is good insurance
for any flights:
www.aeroelectric.com/Pictures/Misc/Failure_Tolerance.pdf
It was also suggested that you try a substitute antenna.
I've fabricated test antennas that could be taped to the
top or bottom surface of a wing and coax brought into
the cockpit through the door gasket or some other pathway.
But using the hand-held to characterize your transmitted
and received signals personally takes ATC and others
out of the loop. This is an especially good thing when
they're unable/unwilling to join the discussion and
offer their own observations/insights.
Bob . . .
AeroElectric-List Email Forum -
http://www.matronics.com/Navigator?AeroElectric-List
- MATRONICS WEB FORUMS -
http://forums.matronics.com <http://forums.matronics.com/>
- List Contribution Web Site -
-Matt Dralle, List Admin.
http://www.matronics.com/contribution
Message 9
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Subject: | Re: Larger D-Sub pins |
I searched for them a few years ago and had almost no success. The only
source I found wanted $5 each. You could try getting them from Garmin
through one of their approved avionics shops.
John Grosse
Stuart Hutchison wrote:
> G'day all,
>
> Has anyone found a convenient after-market supplier for the D-Sub pins with
> an oversize butt that Garmin include in some installation kits? The Garmin
> part number is 336-00023-00 and they're physically longer with a larger
> crimp cup to fit 18 AWG wire ...
Message 10
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Subject: | Larger D-Sub pins |
Most every shop has extras laying around because they almost never use all
of them supplied. Gimme a call if you need a few.
BTW, unless the runs are long an AWG20 wire will work fine in place of an
AWG18.
Cheers,
Stein
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of John
Grosse
Sent: Wednesday, January 25, 2012 9:52 AM
Subject: Re: AeroElectric-List: Larger D-Sub pins
--> <grosseair@comcast.net>
I searched for them a few years ago and had almost no success. The only
source I found wanted $5 each. You could try getting them from Garmin
through one of their approved avionics shops.
John Grosse
Stuart Hutchison wrote:
> G'day all,
>
> Has anyone found a convenient after-market supplier for the D-Sub pins
> with an oversize butt that Garmin include in some installation kits?
> The Garmin part number is 336-00023-00 and they're physically longer
> with a larger crimp cup to fit 18 AWG wire ...
Message 11
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Subject: | Re: Fuses instead of breakers |
At 10:33 PM 1/24/2012, you wrote:
You could use a breaker for this particular circuit. I haven't
thought about electronic ignitions specifically but I too like fuses
over breakers. But convinced myself to use 4 breakers anyway, 2 for
the 2 voltage regulators, 1 for the AP, and one for the flaps. Not
sure I would have used all 4 now that I've flown it a bit but it made
sense to me at the time. So I still have 2 dozen fuses...
As long as your wiring is adequately protected then
what you've installed is not "wrong" . . . just different.
If the voltage regulators are fitted with crowbar
ov protection, then panel mounted breakers are
indicated. If you believe that the AP and flaps
have failure modes for which you desire a crew
driven mitigation, then in-reach breakers are also
indicated. Some folks may find justification for
debating the rationale for your design but the
bottom line is this. What you've done does not
increase risk. It MIGHT drive some small risk to
a yet smaller value. But everybody hopes that you'll
fly this airplane throughout it's useful lifetime
never having encountered an urge to touch any of
those breakers in flight.
Bob . . .
Message 12
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Subject: | Re: Larger D-Sub pins |
OBTW depending on the crimper you have, you may need a different
positioner to crimp the special pins. Another option for your
application might be to join your two wires into a "Y" either with a
soldered joint or a pidg fastener then connecting the single end to your
DB-X. It would be bulkier but easier.
John
Stein Bruch wrote:
> --> AeroElectric-List message posted by: "Stein Bruch"<stein@steinair.com>
>
> Most every shop has extras laying around because they almost never use all
> of them supplied. Gimme a call if you need a few.
>
> BTW, unless the runs are long an AWG20 wire will work fine in place of an
> AWG18.
>
> Cheers,
>
> Stein
Message 13
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Subject: | Fuses instead of breakers |
Hi Jeff,
Regarding what size fuse to use, I have a Lightspeed electronic ignition
with a 5 amp fuse. In about 500 hours of flying, I've blown the fuse
once. Don't know why it blew, and the engine kept running on the
magneto. On the ground, I replaced the fuse and it's been fine since.
Next time I have convenient access to the battery bus, I might put a 7.5
amp fuse instead.
Dennis
Message 14
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Subject: | Re: Antenna Installation Question |
At 04:29 AM 1/25/2012, you wrote:
I fly airplanes in the high flight levels and even there we use the
top antenna primarily. I've thought about it before, and I think a
"to scale" diagram would explain why. Even though 5-6 miles seems
high by altitude standards, it's not very far laterally. If the rco
or tower is 20 or even 100 miles away, the acute angle in the
triangle is small. To visualize more easily, think of the distance in
feet instead of miles. The angles are the same regardless of the
units of course. If you stood 5 feet below your antenna's base and
100 feet away, would the antenna be visible? Likewise at 20 and even
5 feet, it is probably visible from most angles. If it is blocked by
the wing or some other piece of airplane, then it will likely not be
for long in flight.
If the antenna's radiation angle were parallel
with the ground plane, your analogy would be
valid. The driving principal for this discussion
is "radiation angle". See:
http://www.hamradio.in/circuits/radiation_pattern.php
The short story is that an ideal 1/4 wave radiator's
angle of greatest sensitivity points up from the
ground plane by some substantial angle. For many
decades, ham radio operators have know that increasing
the mechanical length of an antenna to 5/8 wavelength
produces a much lower radiation angle. This antenna
is NOT resonant at the frequency of operation. That
deficiency is easily offset by a matching network at
the base of the antenna.
Antennas that long on airplanes would raise some
eyebrows if not elicit a few giggles/snickers.
Nevertheless, radiation angle variations in performance
between top and bottom mounted antennas can be
demonstrated. Large aircraft flying at high altitudes
will always get a stronger measured signal from the
bottom mounted antenna for stations having approximately
45 degree depression angle below the plane of flight.
However, given the line-of-sight performance of VHF/UHF
communications, the loss of performance from a top
mounted antenna may not be noticed from the pilot's seat.
The telling test would be to make contact with
a station that is barely readable on a top antenna
and then compare quality of communication with
a bottom mounted antenna.
A friend of mine (who is also an electron herder/
ham radio operator) has flown many of the heavy
iron birds. He has observed this effect many times.
At the same time, he has noted that when parked at
the gate, a top mounted antenna will talk to some
ground facilities that are degraded for the bottom
antenna when surrounded by jetways, baggage carts
and fuel trucks.
Bob . . .
Message 15
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Subject: | Re: Fuses instead of breakers |
Just one more thing to think about if you are doing this with a
Lightspeed ignition. From what I've read, there is some sort of crowbar
inside the ignition module to protect it from an overvoltage event. If a
fuse is fitted and the crowbar kicks it, you'll not be able to reset it
as easily as with a breaker - if you can reach the fuse at all. I've
heard of at least one case where an airplane was brought down because it
was wired differently than the installation instructions in that regard.
Ed Holyoke
On 1/25/2012 8:48 AM, Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 10:33 PM 1/24/2012, you wrote:
> <mauledriver@nc.rr.com>
>
> You could use a breaker for this particular circuit. I haven't
> thought about electronic ignitions specifically but I too like fuses
> over breakers. But convinced myself to use 4 breakers anyway, 2 for
> the 2 voltage regulators, 1 for the AP, and one for the flaps. Not
> sure I would have used all 4 now that I've flown it a bit but it made
> sense to me at the time. So I still have 2 dozen fuses...
>
> As long as your wiring is adequately protected then
> what you've installed is not "wrong" . . . just different.
> If the voltage regulators are fitted with crowbar
> ov protection, then panel mounted breakers are
> indicated. If you believe that the AP and flaps
> have failure modes for which you desire a crew
> driven mitigation, then in-reach breakers are also
> indicated. Some folks may find justification for
> debating the rationale for your design but the
> bottom line is this. What you've done does not
> increase risk. It MIGHT drive some small risk to
> a yet smaller value. But everybody hopes that you'll
> fly this airplane throughout it's useful lifetime
> never having encountered an urge to touch any of
> those breakers in flight.
>
>
> Bob . . .
>
>
Message 16
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Subject: | Larger D-Sub pins |
At 10:31 AM 1/25/2012, you wrote:
>
>Most every shop has extras laying around because they almost never use all
>of them supplied. Gimme a call if you need a few.
>
>BTW, unless the runs are long an AWG20 wire will work fine in place of an
>AWG18.
You beat me to it my friend. I will also suggest that it's
perfectly okay to peel a few strands out of the "too large"
wire to get them all into the 20AWG crimp cup of a standard
pin. You'll have to leave the bare strands exposed over a
greater length because the insulation will not go down
into the wire opening of the connector. Experiment with
an extra pin and a chunk of wire to establish the new strip
dimensions.
When somebody calls for putting overweight wires into
a d-sub connector, the design goal is to REDUCE WIRE
PATHWAY IMPEDANCE. Putting the larger wire into the
pin does not increase the pin's current handling
ability. Hence my suggestion for peeling out extraneous
strands is not a technically 'evil' thing to do in
terms of the physics. It would have an immeasurable
impact on design goals that called for the larger wire.
I think this is preferable to the FAT pin. It adds
no bulk to wiring immediately behind the connector
and leaves less exposed conductor.
However, pulling this trick in an ISO/FAA/PP driven
TC aircraft shop would probably get you fired or
at least a 'ding' in your employment record.
Bob . . .
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Subject: | Re: Instrument Earth Bus cable size |
>My question is:
>What is the minimum size cable can I use from the copper tab on the
>FRONT of the earth conduit tab (just behind the nose section) to the
>instrument earth bus (approx 18-20 inches in length). I'm trying to
>avoid using the very heavy welding cable.
See VIEW -B- in this drawing:
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z15K1.pdf
In your case, the 2AWG ground wire is a piece of copper tube.
Your design does not call for a firewall ground bus so the
engine ground strap goes right to the copper tube. Your design
does not mention the use of a forward high-power ground bus
so the battery (-) wire goes right to a tab on the copper
tube. An instrument panel ground bus could be fabricated per
http://aeroelectric.com/Pictures/Grounding/AVG_RA.jpg
http://aeroelectric.com/Pictures/Grounding/Avionics_Bus_3.jpg
Figure Z15 suggests that a parallel bundle of 5,
20AWG wires be run from the avionics ground to the
tab on the end of your copper tube. Landing
light and position lights could also ground to the
bolt in the copper tube tab.
If you're fabricating your own d-sub panel ground
bus, you could solder a couple of 14AWG wires to
the commoning conductor at the back of the
connector. This is described in
https://matronics.com/aeroelectric/Catalog/AEC/9031/IM9031-700A.pdf
Bob . . .
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Subject: | Re: Fuses instead of breakers |
>Next time I have convenient access to the battery bus, I might put a
>7.5 amp fuse instead.
Good idea.
Bob . . .
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Subject: | Re: Fuses instead of breakers |
At 11:24 AM 1/25/2012, you wrote:
Just one more thing to think about if you are doing this with a
Lightspeed ignition. From what I've read, there is some sort of
crowbar inside the ignition module to protect it from an overvoltage
event. If a fuse is fitted and the crowbar kicks it, you'll not be
able to reset it as easily as with a breaker - if you can reach the
fuse at all. I've heard of at least one case where an airplane was
brought down because it was wired differently than the installation
instructions in that regard.
Can you elaborate on what you've read and give us sources?
I'm unaware of any crowbar ov protection built into the
LSE system. Is this called out in any of their published
literature? I found this on the Lightspeed site:
------------------------
Electrical System Requirements
All Plasma CDI systems can be used with 12 or 24 volt electrical
systems. Input voltages above 35 volts or reversed polarity can
cause system damage.
For this reason it is mandatory that all aircraft using Plasma CD
Ignitions are equipped with over-voltage protection in their
alternator charging system(s). Over-voltage protection is a
requirement for certified aircraft. Power connection must be
directly to the battery terminals to avoid voltage spikes and
electrical noise. Aluminum should never be used as an electrical
conductor for the Plasma CDI. Use only the supplied aircraft quality
stranded wire.
Minimum supply voltage for starting is 6.5 Volts.
Minimum operating voltage is 5.5 Volts.
--------------------------
This statement argues against any built-in ov
protection. At the same time, the very wide operating
voltage for the system guarantees that a properly
designed 14v system will NEVER offer a threat to
the LSE system.
I am presently participating in an analysis of
cause and effect for simultaneous failure of
dual LSE systems. Root cause for that event
was a failure to craft a failure tolerant
architecture . . . a design goal which is foundation
for all efforts here on the AeroElectric-List.
It's a certainty that no builder who participates
here on the List will suffer such an event.
Bob . . .
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Subject: | Re: Instrument Earth Bus cable size |
Many thanks to everyone. Very informative and helpful replies, I will be studying
the resources.
MikeD (U.K.)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=364843#364843
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Subject: | Re: Fuses instead of breakers |
I appreciate everyone's comments regarding sizing fuses.
The reference to the FARs regarding battery bus circuits was useful.
My design doesn't exceed those specifications. Fortunately, with an
amateur-built aircraft, no bureaucrat can claim that a 5A circuit
protective device would be the size of both the fuse and the circuit
breaker.
So a 10A fuse will probably work reliably with a Lightspeed ignition. Thanks.
How about another example ? The popular approach is to use a pullable
breaker for the hydralic pump for the amphibious landing gear. If I
use a switch and a fuse, what size fuse ? I appreciate that I can
always install a bigger fuse if nuisance pops occur, but it seems more
professional to do the initial design with a good idea that the
correct fuse was chosen in the first place ;-)
So, does this logic work ?
The pressure switch deactivates the pump at 500psi, but there will
likely be short term pressure spikes above that. So, pick 1000psi.
The current versus pressure chart for the motor, shows 3A at 500psi
and 5A at 1000psi, as well as 23A at 3000psi, which is probably almost
stalling the motor. So assume a typical current of 3A and spikes of
less than a half second to 10A.
Since a 10A fuse should blow after 1 second with 12.5A, that should be
sufficient to avoid a nuisance pop ?
During that half second, I want full power to the motor, so I will use
10A for the gauge versus wire length calculation. To drop 5% power
through wire resistance, that gives me 18' for 16AWG wire. I should
be able to get to the pump and back in less than 18', so 16AWG should
be sufficient.
A 30 degree rise for 16AWG wire requires 19A, so I could safely upsize
to a 15A or 20A fuse.
With your experience, should I start with a 10A or 15A fuse and expect
it not to nuisance trip ?
Are there any other reasons why a pullable circuit breaker would be
preferred for this situation ?
Jeff Page
Dream Aircraft Tundra #10
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Subject: | Re: Fuses instead of breakers |
I'll second the earlier comment on LSE ignitions having a crowbar setup. I had
initially installed fuses to power a dual Plasma III setup. During a discussion
with Klaus he quickly took exception to this and told me verbally that they
DID have a crowbar setup (but I did not get into a discussion with him about
the triggering criteria). Since it's a pretty long wire run in an RV-10 from
the standard battery location to where the ignition boxes are located, he recommended
having 7.5 amp CBs on the panel and if I felt the need to protect the
feeders (he didn't) from the batteries to use 10 amp CBs back there, guaranteeing
that the 7.5s would be what tripped during whatever event trips the crowbar.
His very clear preference is to simply run the shielded, #18 (I think) wire all
the way back and direct connect to the battery. I couldn't in good conscience
live with a pair of always hot, unprotected wires for a run of that long and
replaced the fuses near the batteries with 10 amp CBs and put 7.5 amp CBs on
the panel as he recommended.
Above conversation took place with him about 3-4 years ago but I remember it very
clearly.
Bob C.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=364852#364852
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Subject: | Re: Fuses instead of breakers |
At 04:27 PM 1/25/2012, you wrote:
I appreciate everyone's comments regarding sizing fuses.
The reference to the FARs regarding battery bus circuits was useful.
My design doesn't exceed those specifications. Fortunately, with an
amateur-built aircraft, no bureaucrat can claim that a 5A circuit
protective device would be the size of both the fuse and the circuit
breaker.
Who said anything about regulations? Just because it's
in a holy-watered book doesn't mean it's not a
valuable ingredient in a recipe for success.
So a 10A fuse will probably work reliably with a Lightspeed ignition. Thanks.
Absolutely.
How about another example ? The popular approach is to use a pullable
breaker for the hydraulic pump for the amphibious landing gear. If I
use a switch and a fuse, what size fuse ?
BIG and beefy . . . in fact for things like hydraulic pump
motors you would consider ANL style current limiters. That's
what we used on the Beech products.
I appreciate that I can
always install a bigger fuse if nuisance pops occur, but it seems more
professional to do the initial design with a good idea that the
correct fuse was chosen in the first place ;-)
Absolutely!!!!! Which is why we have the List. There are
fuses, then there are Fuses and then FUSES. Circuit breakers
come in many flavors of operating speed too. The differences
can be significant in crafting a trip-free system. Recall
years back we discussed the fact that there are tens of
thousands of TC aircraft flying with an alternator b-lead
breaker designed to nuisance trip? 60A circuit breakers
on 60A alternators. An alternator that will put out MORE
than 60A under some conditions.
So, does this logic work ?
The pressure switch deactivates the pump at 500psi, but there will
likely be short term pressure spikes above that. So, pick 1000psi.
The current versus pressure chart for the motor, shows 3A at 500psi
and 5A at 1000psi, as well as 23A at 3000psi, which is probably almost
stalling the motor. So assume a typical current of 3A and spikes of
less than a half second to 10A.
Since a 10A fuse should blow after 1 second with 12.5A, that should be
sufficient to avoid a nuisance pop ?
Don't agonize over it. You're wanting to protect what size wire?
Scratch that. Wire with 10 AWG and use an ANL35 or equal. 10AWG
is plenty heavy and will reduce voltage drop in the system. It's
the 10x inrush current of what is probably a PM motor that drives
the selection of protection . . .
During that half second, I want full power to the motor, so I will use
10A for the gauge versus wire length calculation. To drop 5% power
through wire resistance, that gives me 18' for 16AWG wire. I should
be able to get to the pump and back in less than 18', so 16AWG should
be sufficient.
I'd go with the 10AWG. If 23A and 5000 PSI is a data point, then
its doubtful that the motor is anywhere near stall. I'll bet inrush
is 2 to 3 times that amount.
A 30 degree rise for 16AWG wire requires 19A, so I could safely upsize
to a 15A or 20A fuse.
With your experience, should I start with a 10A or 15A fuse and expect
it not to nuisance trip ?
Are there any other reasons why a pullable circuit breaker would be
preferred for this situation ?
What controls the pump motor . . . a contactor?
Is it tailored for intermittent duty, hi-inrush
service like a starter-contactor? Sticking of this
device might pose an in-flight concern. However,
if you have a dual path e-bus, you can kill the
main bus and shut down a runaway pump motor while
retaining the electro-whizzies needed for comfortable
completion of flight.
Your question goes to exactly the kind of exercise
every electrical system benefits . . . failure mode
effects analysis, "What if . . . and how do I deal
with it as a maintenance event as opposed to an
emergency?" If an FMEA calls for a second disconnect
such as a pullable breaker, then by all means.
Worrying about poorly considered failures tends to
stack redundancy on top of redundancy. It drives up
parts count, cost of ownership and adds to system
complexity. Complexity makes the pilot's job more
difficult and risky. Well considered FMEA tends
to produce the elegant solution: Just enough hardware
with minimum risk and simpler to operate.
Bob . . .
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Subject: | Re: Fuses instead of breakers |
>During a discussion with Klaus he quickly took exception to
>this and told me verbally that they DID have a crowbar setup
>(but I did not get into a discussion with him about the
>triggering criteria).
Hmmmm . . . I'll be seeing Klaus in the not too distant
future. I'll inquire.
Bob . . .
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Subject: | Re: Fuses instead of breakers |
Bob, please do. In the meantime, for those of us just getting to wiring,
would this be reasonable, or overkill?
Battery Bus Input terminal (not fused) ---> Fusible Link ---> Panel Breaker
---> Switch ---> LSE box?
I'm not sure how ground would best get there since Klaus calls out shielded
wire and it might be a little bit of a run to the FW ground or battery
ground.
Thoughts? (Or am I overthinking this?)
-Jeff-
On Wed, Jan 25, 2012 at 7:52 PM, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> nuckolls.bob@aeroelectric.com**>
>
>
> During a discussion with Klaus he quickly took exception to
>> this and told me verbally that they DID have a crowbar setup
>> (but I did not get into a discussion with him about the
>> triggering criteria).
>>
>
> Hmmmm . . . I'll be seeing Klaus in the not too distant
> future. I'll inquire.
>
>
> Bob . . .
>
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Subject: | Re: Fuses instead of breakers |
At 09:47 PM 1/25/2012, you wrote:
Bob, please do. In the meantime, for those of us just getting to
wiring, would this be reasonable, or overkill?
Battery Bus Input terminal (not fused) ---> Fusible Link ---> Panel
Breaker ---> Switch ---> LSE box?
At the moment, I see no reason to treat the LSE
ignition system any differently than any similar
system offered to the TC aircraft world.
If based on what I know now, I'd go 10A fuse at
the battery bus driving a 20AWG non-shielded wire
to an ON/OFF switch on the panel and then to the
ignition system.
I'm not sure how ground would best get there since Klaus calls out
shielded wire and it might be a little bit of a run to the FW ground
or battery ground.
Shielded wire for this application is completely
unwarranted. There is no potential antagonist/
victim scenario which would capacitively couple
into our out of the LSE product. Grounding of the
LSE ignition module should be no more complex
than to take a 20AWG wire to the firewall ground
bus.
Thoughts? (Or am I overthinking this?)
I don't think so. Klaus worries about some things
that are either insignificant or non existent. "Noise"
on the bus is NOT mitigated by connecting to the
battery. I think I explain this in the battery
chapter of the book. Batteries are simply not
filters of any small excursions of bus voltage
at any frequency.
This is precisely why DO-160 and Mil-STD-704
tell the TC aircraft designer to EXPECT certain
kinds of noise on the ship's DC bus. See:
http://www.aeroelectric.com/Pictures/Curves/MSTD704_28V_Noise.jpg
That flat top in the plot between 1 and 5 Khz
is 1 volt RMS or about 3 volts peak to peak
on a 28 volt system. Cut those numbers in half
on a 14 volt system. The amplitude for expected
noise falls off on either side . . . but the
point is, NOTHING . . . especially the battery
will mitigate this noise. Hence the admonition,
"It's there son, learn to live with it."
Indeed we who have run the gauntlet on qualification
for TC aircraft have learned to live with it . . .
in face, it's such a benign stress that "dealing
with it" is not even much of a technically intellectual
exercise.
It makes no sense to build crowbar ov protection
into a product when it's so easy to build passive
shutdown protection. I did this little fast-disconnect
switch to qualify an automotive seat warmer onto
a 28v aircraft.
http://aeroelectric.com/Pictures/Schematics/80v_Surge_Protection.jpg
this circuit simply 'disconnects' the vulnerable
device from the bus during the transient and reconnects
when the event is over.
But more important is the fact that in a 14 volt
airplane, the maximum alternator-runaway event is
limited to 20 volts . . . which is well inside the
LSE's NORMAL operating voltage.
Finally, you could treat a robust feeder from
battery to ignition system just like a fat feeder
to the e-bus. It might look something like this:
http://aeroelectric.com/Pictures/Schematics/Battery_Feed_for_Ignition.pdf
This satisfies the design goals for crash safety
by having a pilot operated disconnect at the battery.
The relay only draws about 100 mA so it's not a big
budget energy consumer for battery only operations.
Modern relays are quite reliable . . . and this one
gets pre-flight tested.
Point is there's a lot of ways to skin cats-of-
legitimate-worry. The task is to separate real worries
from bogus worries.
Bob . . .
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