Today's Message Index:
----------------------
1. 05:53 AM - Re: Summary of concerns on electric gyro reliability (Dennis O'Connor)
2. 05:53 AM - Re: Fuses (KITFOXZ@aol.com)
3. 06:32 AM - Re: Summary of concerns on electric gyro reliability (BobsV35B@aol.com)
4. 06:53 AM - Re: Summary of concerns on electric gyro reliability (BobsV35B@aol.com)
5. 07:57 AM - Wire (ing) Questions (Don Boardman)
6. 07:58 AM - Re: LARGE VOLTAGE DROP (Charlie and Tupper England)
7. 11:27 AM - OV Protection/Internal Regulator (Jon Finley)
8. 01:25 PM - Re: S701-1 contactor for OV (Robert L. Nuckolls, III)
9. 01:35 PM - Re: LARGE VOLTAGE DROP (Robert L. Nuckolls, III)
10. 01:44 PM - Re: Wiring issues at the wing root (Robert L. Nuckolls, III)
11. 02:08 PM - Re: Summary of concerns on electric gyro (Robert L. Nuckolls, III)
12. 03:38 PM - Re: Wire (ing) Questions (DHPHKH@aol.com)
13. 05:32 PM - Re: Wiring issues at the wing root (Lynwood Stagg)
14. 06:13 PM - Z-13 questions (czechsix@juno.com)
15. 06:23 PM - Shielded wire (Larry Bowen)
16. 08:36 PM - Re: Z-13 questions (Robert L. Nuckolls, III)
17. 09:07 PM - Shielded wire (Jim V. Wickert)
18. 09:31 PM - Manassas VA Seminar Date Set (Robert L. Nuckolls, III)
19. 09:38 PM - Re: Shielded wire (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Summary of concerns on electric gyro reliability |
--> AeroElectric-List message posted by: "Dennis O'Connor" <doconnor@chartermi.net>
If electric gyros are so inherently unsafe why does nearly every IFR
airplane have an electric gyro turn indicator as the last resort?
Vastly more fatal crashes have occurred due to failure of a vacuum gyro than
have occurred due to failure of an electric gyro.. So a vacuum system is
not, per se, safer than an electric system...
Not all vacuum gyro failures are due to a vacuum pump failure... Vacuum
gyros fail internally on a regular basis or there would not be numerous gyro
rebuilders making their living rebuilding them.... A gyro bearing failure
will not show a vacuum flag... So a vacuum flag does make the vacuum gyro
safer than the electric gyro in respect to internal failure...
Neither source of power to the gyros, either vacuum or electric, is better
than the other... What is the answer is an airworthy installation, a method
of cross checking the AI against the DG, and a constant practice of partial
panel techniques..
Preventive maintenance is necessary regardless of the source of power to the
gyro...
Denny
----- Original Message -----
From: "Stephen Johnson" <spjohnsn@ix.netcom.com>
Subject: AeroElectric-List: Summary of concerns on electric gyro reliability
> --> AeroElectric-List message posted by: "Stephen Johnson"
<spjohnsn@ix.netcom.com>
>
> The postings the last week on electric gyro reliability have penetrated my
> thick skull and actually caused me to change my mind about the way I will
> initially equip my RV-8. Without rehashing everything, the real show
> stopper for me on the electric gyros is the failure mode where you can
have
> false attitude information with no indication that the gyro has failed. I
> attribute this to the fact that the electric gyros have internal circuity
to
> convert DC to AC for the motor. True, you have the other gyros to
compare,
> but the task of deciding where the error lies in a timely manner in actual
> IFR conditions is something I would rather not try. With a vacuum system,
> you have the option of a low suction warning light as well as the suction
> gauge. Add this to the fact that the value of the RC Allen gyros will
drop
> subtantially when EFIS is a working reality with some service history.
> Right now I think I will go with the vacuum system, change the pump at 500
> hour intervals, equip with a suction warning light, and design the system
to
> be easily converted to a dual alternator/essential bus configuration later
> when the inevitable price reductions and improvements arrive with EFIS. I
> just ordered the servo kit for the S-Tec model 30, so I'll have the
> autopilot on the electrical bus if the vacuum pump gives out just as a
> backup.
>
> Steve Johnson
> building RV-8
>
>
Message 2
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--> AeroElectric-List message posted by: KITFOXZ@aol.com
In a message dated 1/17/2003 9:22:54 PM Eastern Standard Time,
emjones@charter.net writes:
>
> Everything I think know about fuses, but just my opinions:
>
> European fuses seem to have poor ability to withstand vibration. This is an
> important spec for aircraft. The fuses in German-made machinery have
> historically been less reliable than US stuff. For the last 28-years I
> would see German fuses come apart in a million pieces: Two end-caps, an
> element, a glass tube and 999,996 grains of sand.
>
> NASA technicians replaced lots of fuses with brass rods (called no-blows)
> when manned launches started.
>
> It took me two years to find the short-circuit in my Jeep that blew the
> foglight fuses every nine months.
>
> People get PhD's in fusing technology, but there is always stuff that will
> burn up and not blow a fuse.
>
> Don't plug a vacuum cleaner into your computer power strip.
>
> Eric M. Jones
>
>
>
Hello Eric,
Boy Eric, Bob will have a field day with this list of stuff! First, don't
forget that the fuses that we are installing in our aircraft are there to
protect the wires from heating due to an over current condition. The worst
case scenario could be a FIRE! The cause of an over current condition could
be one or more of several. Anything from a chaffed or nicked wire to a
failed electronic part, connector, foreign object, liquid (God forbid fuel),
etc., will blow a fuse and keep the wire cool.
Just think, you saved your Jeep every nine months with a 50 cent fuse. You
finally found the nicked wire and repaired it with a piece of electrical tape
right? You could have replaced that 3 AG fuse on that first day with one of
the infamous "quarter-twenty NO BLOWS" and smoke checked your Jeep's wiring
harness!
(for you younger guys, that's a 1" X 1/4" bolt with the head cut off) This is
one reason why cars are now built with the plastic bayonet fuses of today.
Many of the goodies in your aircraft panel can fail and puff smoke without
blowing the panel circuit fuse. Each panel box is internally protected with
fuses, fusible links or sacrificial electronic components to prevent a
thermal run away and fire. The smoke is a good sign really, that a
sacrificial component has died and shut the current off. If the internal
failure is massive enough, it will blow your properly sized aircraft panel
circuit fuse before the wires get hot.
I can't believe NASA engineers ever allowed fuses to be jumpered out without
further protection up stream.
I agree with your negative comments on many German engineered fuses. I have
had similar observations with German automotive electrical parts in general.
This does not mean that German engineers can't build a fuse. They just
refuse to spend the money to build them for a longer life expectancy in some
product lines.
Shame on you! Not even my wife would ever plug the vacuum cleaner into the
computer power strip! She prefers to use the kitchen receptacle above the
four slice toaster. You know, the circuit that powers the refrigerator,
dishwasher, trash compactor, garbage disposal and microwave oven.
John P. Marzluf
Columbus, Ohio
Outback, (out back in the garage)
Message 3
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| Subject: | Re: Summary of concerns on electric gyro reliability |
--> AeroElectric-List message posted by: BobsV35B@aol.com
In a message dated 1/18/03 7:54:38 AM Central Standard Time,
doconnor@chartermi.net writes:
> Neither source of power to the gyros, either vacuum or electric, is better
> than the other... What is the answer is an airworthy installation, a method
> of cross checking the AI against the DG, and a constant practice of partial
> panel techniques..
>
Good Morning Denny,
You have hit the nail quite squarely!
There are two factors that need to be addressed.
The first thing is to have a means of rapidly and positively identifying a
failed or failing instrument.
The second thing is to have the capability of controlling the aircraft after
the failure has been discovered.
I think it can be said that the simplest things tend to be the most reliable.
The simplest gyroscopic instrument available is the classic Turn & Bank. It
is followed closely by the canted gyro driven Turn Coordinator.
I have never seen a failure of a Turn and Bank where the needle did anything
else except quit responding. I am sure it would be possible for it to fall
to one side or the other, but every one that I have had fail has just been
sitting there in the middle, or very close to the middle, with no motion at
all.
As long as the needle will wiggle when you press a rudder pedal, it will be
giving adequate guidance to allow safe flight. The rate of turn may not be
standard, but the instrument will be usable.
As is true of almost all back up strategies, the back up that is used in
everyday operation tends to be the easiest to use.
Instead of rolling into a twenty degree bank, roll into a twenty degree bank
and simultaneously note the rate of turn that results. If it is more or less
than standard rate, either adjust the bank until the turn rate is standard or
make a mental note that you are using other than a standard rate. It won't
take any more effort than just using the attitude gyro, but it trains your
eye to use the T&B for normal flight.
There is no procedure that I know of that will allow an aviator to discern an
impending Attitude Gyro Failure than to include the rate instrument in
his/her everyday scan.
I, personally, think the T&B is a vastly superior instrument to the Turn
Coordinator, but if either one is regularly included in the normal flight
scan, it should do the job rapidly and efficiently.
One more thing. Be sure you carry a pasty note or some other do-hickey to
cover up a failed attitude instrument. Makes partial panel flight much
easier if you can't see that leaning gyro.
It is conceivable that something like the new Garmin 196 may be even better
than the T&B. Only time will tell.
The big thing is to stop the turn. If you don't turn, you will survive!
Happy Skies,
Old Bob
Message 4
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| Subject: | Re: Summary of concerns on electric gyro reliability |
--> AeroElectric-List message posted by: BobsV35B@aol.com
In a message dated 1/18/03 8:31:56 AM Central Standard Time, Bobs V35B
writes:
> There is no procedure that I know of that will allow an aviator to discern
> an impending Attitude Gyro Failure than to include the rate instrument in
> his/her everyday scan.
>
OOOPS!
Left a word out.
Meant to say:
There is no procedure that I know of that will allow an aviator to discern an
impending Attitude Gyro Failure faster than to include the rate instrument in
his/her everyday scan.
Happy Skies,
Very Old Bob
Message 5
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| Subject: | Wire (ing) Questions |
--> AeroElectric-List message posted by: Don Boardman <dboardm3@twcny.rr.com>
Hi Bob,
Hope all is well.
Panel is cut and the firewall forward is on its way. Avionics are on the
bench. I have a copy of The AeoElectric Connection. All the items I could
think of where ordered from B&C Specialty and are sitting on the shelf.
About the last prep task is to order wire.
Our Murphy Moose will be powered by the M-14PF radial engine. It uses an air
start so there is no electric starter and it's associated contactor.
I am using a Skytronics 50 amp alternator with a Jasco j12M20SP regulator
which incorporates a SVP-3 voltage protector. We will be running dual
alternators using the B&C 8Amp back up and a single battery.
I would appreciate it if you would verify my thinking.
1. Without electric start do I run the wire from the B output terminal on
the alternator to the anl-60 and then directly to the S701-2 battery
contactor?
2. The Skytronics people indicate the use of #8 wire for single routing and
#6 wire when bundled to handle the output of the 50 amp alternator. I see #2
& #4 wire used from Battery to contactor, to starter contactor, to
alternator. in most schematics. The wire chart says #8 carries 40A, #6 54A
with a 35C rise. At a 10C rise 40A would call for #4 wire and at 50A a bit
larger. Your recommendation for wire size from Battery to contactor and then
to the alternator output in this application?
Regards,
Don Boardman
& Partner, Randy Bowers
Super Moose #130 M-14PF 400HP, MT-prop, Aerocet 3500 amphibs, Rome, NY
Message 6
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| Subject: | Re: LARGE VOLTAGE DROP |
--> AeroElectric-List message posted by: Charlie and Tupper England <cengland@netdoor.com>
for clarity, were you probing the wire itself at each end, or the connection points?
Charlie
Meketa wrote:
> --> AeroElectric-List message posted by: "Meketa" <acgm@gvtc.com>
>
> Bob
>
> I would like to hear your theory to the cause of this problem I experienced.
Here are
> pieces of several messages on the subject. Not on an airplane, but airplane related.
> The voltage drop was 5-6 volts across about 6 feet of cable.
>
>
>
>>Another friends 63 Corvette had severe cranking problems when hot.
>>A voltage drop test found all the battery cables had high amounts of
>>voltage loss when crankling. A master battery cable disconnect was installed
>>under the seat and the longer cables were fabricated with fine strand welding
>>cable. He had a hard time believing my diagnosis, but replaced the cables
>>anyway. Problem solved. He used the same style welding cable and the
>>problem reoccured again a year later. He now has standard automotive
>>battery cable with no further problems. This friend builds custom cars for
>>a living and now uses only auto type battery cable. We never figured out
>>the real problem with the cables, it was not the terminal connections, but
>>in the cable itself. Possible internal oxidation of some type.
>
>
>
>>I never came to an actual conclusion as to the cause of the welding cable problem,
>>but do have several theories. The oxidation being the main one (the inner strands
>>were not bright copper colored), and a change in metalurgy due to high amperage
>>loads on the cable being the other. For years I have read or heard that the fine
>>stranded cable is far superior to standard automotive cable and never heard of
any
>>problems. The supplier of the second set of cables rebuilds starters and alternators
>>for a living and swears by them. The tefzel battery cable on my plane is fine
strand,
>>but the conductor is tin coated. I suspect it would not be as vulnerable to
the
>>oxidation. That would make a simple test on the Corvette, but would be a lot
harder
>>to run due to the lack of flexability in the cable. Maybe a good question for
>>Aeroelectric Bob.
>
>
>>You will likely never have a problem with yours. The particular engine with these
>>cables is a 600+ HP/430+CID small block. A high torque starter and large battery
>>are required to crank the engine. On a hot day and the engine warmed up about
>>300 amps continuous and a peak well over 400 amps is required to crank it. I
have
>>no figures for our aircraft engines, but it is far less than that. Maybe less
than 100
>>amps.
>
>
>
> Thanks in advance
>
> George Meketa
> Van's RV8, 239 hours
>
Message 7
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| Subject: | OV Protection/Internal Regulator |
--> AeroElectric-List message posted by: "Jon Finley" <jon@finleyweb.net>
Hi Bob (Nuckolls),
In your book (page 6-6, diagram 6-4 (The Ultimate Protection, the
"Relayless" O.V. Relay)) an OV circuit is shown that does not include an
alternator OV disconnect contactor. In figure Z-24 the contactor is
shown. Could you please elaborate on the differences? I would guess
that the concern is when the alternator field is cut (fuse blows) the
alternator may not immediately stop producing power (but since I know
nothing about electricity my assumptions are dangerous!)?
FYI: my situation is a auto engine (Subaru) with an internally regulated
alternator.
Thanks!
Jon Finley
N90MG Q2 - Subaru EJ-22 DD - 440 Hrs. TT - 0 Hrs Engine
Apple Valley, Minnesota
http://www.FinleyWeb.net/default.asp?id=96
Message 8
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| Subject: | Re: S701-1 contactor for OV |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 05:21 PM 1/17/2003 -0500, you wrote:
>--> AeroElectric-List message posted by: DWENSING@aol.com
>
>Bob,
>Recently you stated "To use the S701-1 as a OV disconnect contactor in the
>B-lead of your alternator, the jumper is removed, the terminal marked TO
>MASTER SWITCH goes to ground, the terminal that used to have the jumper on it
>goes to your alternator control switch, crowbar ovm and alternator control
>lead."
>
>Question: can these connections be reversed?
>Dale Ensing
Nothing inside the contactor is polarity
sensitive . . . only the spike catcher diode
on the two small coil terminals. You can
freely interchange the large terminals. If
you reverse the small terminals, be sure
to turn the diode around also.
Bob . . .
Message 9
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| Subject: | Re: LARGE VOLTAGE DROP |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 12:36 AM 1/18/2003 -0600, you wrote:
>--> AeroElectric-List message posted by: "Meketa" <acgm@gvtc.com>
>
>Bob
>
>I would like to hear your theory to the cause of this problem I
>experienced. Here are
>pieces of several messages on the subject. Not on an airplane, but
>airplane related.
>The voltage drop was 5-6 volts across about 6 feet of cable.
> >Another friends 63 Corvette had severe cranking problems when hot.
> > A voltage drop test found all the battery cables had high amounts of
> > voltage loss when crankling. A master battery cable disconnect was
> installed
> > under the seat and the longer cables were fabricated with fine strand
> welding
> > cable. He had a hard time believing my diagnosis, but replaced the cables
> > anyway. Problem solved. He used the same style welding cable and the
> > problem reoccured again a year later. He now has standard automotive
> > battery cable with no further problems. This friend builds custom cars for
> > a living and now uses only auto type battery cable. We never figured out
> > the real problem with the cables, it was not the terminal connections, but
> > in the cable itself. Possible internal oxidation of some type.
>
>
> >I never came to an actual conclusion as to the cause of the welding
> cable problem,
> >but do have several theories. The oxidation being the main one (the
> inner strands
> >were not bright copper colored), and a change in metalurgy due to high
> amperage
> >loads on the cable being the other. For years I have read or heard that
> the fine
> >stranded cable is far superior to standard automotive cable and never
> heard of any
> >problems. The supplier of the second set of cables rebuilds starters and
> alternators
> >for a living and swears by them. The tefzel battery cable on my plane is
> fine strand,
> >but the conductor is tin coated. I suspect it would not be as
> vulnerable to the
> >oxidation. That would make a simple test on the Corvette, but would be a
> lot harder
> >to run due to the lack of flexability in the cable. Maybe a good
> question for
> >Aeroelectric Bob.
Your theory is as good as any . . . I'd sure like to put my hands
on a "failed" piece of wire for further analysis. IF the wire's
resistance was uniformly raising over its length, I'm wondering
why it took so long to find the problem . . . it would seem that
a much lower voltage drop would be easily noticed in terms cranking
performance . . . a 5-6 volt drop would just about render the starter
motor motionless. Color me skeptical.
Bob . . .
Message 10
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| Subject: | Re: Wiring issues at the wing root |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 10:51 AM 1/17/2003 -0500, you wrote:
>--> AeroElectric-List message posted by: "Lynwood Stagg" <woody6@yahoo.com>
>
>Thanks Randy. I had not run across your site yet. Very helpful.
>
>With the Whelen install kit for strobes, the 3 conductor cable has a shield
>for attach at the power supply end. Did you just run this through the wing
>root connector too? I wasn't sure how this would impact the shielding
>re:noise.
The wing root connectors thing comes around periodically.
Keep in mind that every connector you put in a wire bundle
adds three new joints to every wire. I am flying airplanes
that are 40 years old and never had the wings removed.
Does the convenience of the wing root connector(s) offset
the decreased reliability that every connector adds?
If it were my airplane, I'd leave long pigtails hanging
out of the wing roots for wing wiring that would be left
un-connected until final mating of wings to fuselage.
Wire routing would leave enough slack for about a 6"
diameter "service loop" of wire in each bundle. Should
the wings require removal at some later date, there is
sufficient slack in the wires to allow cutting and splicing
with PIDG butt-splices . . . nearly as reliable as original
wire.
Coaxes, of course, would need to have connectors installed
suited to this special case.
If you MUST have connectors in wire bundles that use
shielded wire, the shields should be treated as separate
conductors and enjoy their own pin for carrying shield
integrity across the connector.
If you DO install wing root connectors, allow for the
service-loop slack I suggest above anyhow. You may
find this extra wire handy in the future should you
find it useful to cut the connector out of the wire
bundle and close the gap with butt-splices.
Bob . . .
Message 11
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| Subject: | Re: Summary of concerns on electric gyro |
reliability
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 02:41 PM 1/17/2003 -0600, you wrote:
>--> AeroElectric-List message posted by: "Stephen Johnson"
><spjohnsn@ix.netcom.com>
>
>The postings the last week on electric gyro reliability have penetrated my
>thick skull and actually caused me to change my mind about the way I will
>initially equip my RV-8. Without rehashing everything, the real show
>stopper for me on the electric gyros is the failure mode where you can have
>false attitude information with no indication that the gyro has failed.
This can happen to a vacuum gyro too . . .
>I attribute this to the fact that the electric gyros have internal circuity to
>convert DC to AC for the motor.
There are several ways the gyro can become unstable, or insufficiently
powered whether driven by vacuum or voltage . . .
>True, you have the other gyros to compare,
>but the task of deciding where the error lies in a timely manner in actual
>IFR conditions is something I would rather not try.
Didn't your instructor work with you on instrument cross checking?
You have mag compasses, turn coordinators, rate of climb, air speed,
altimeters, gyro horizons and compasses, that ALL re-enforce each other
during stable flight conditions. My instructor liked to cover up
combinations of flight instruments while I was under the hood
to demonstrate the need for shifting modes of operation from
one type of display to the other. He told me that he personally
tried to fly need-ball-airspeed all the time and use the
gyros to CROSS CHECK his performance . . . Any one of the cited
devices can become unusable at any time. Your ability to detect
the failure becomes linked to how well you understand and have
trained on the remaining instruments. Trying to play "gee I wish I'd
practiced that more" catch up after you perceive an argument going
on between instruments is a bit late.
> With a vacuum system,
>you have the option of a low suction warning light as well as the suction
>gauge. Add this to the fact that the value of the RC Allen gyros will drop
>subtantially when EFIS is a working reality with some service history.
How come? What's to say that a poorly crafted solder joint on the
rate sensor of your AHRS will cause you less grief than
blown vanes in your vacuum pump? And what comfort it is
to KNOW that suction is falling on your vacuum system when you
know that the same pump runs BOTH instruments?
>Right now I think I will go with the vacuum system, change the pump at 500
>hour intervals, equip with a suction warning light,
The warning light for most airplanes fitted with vacuum systems
works just like the low voltage light (which I hope every one is
installing). Light-on, power-source has crapped. And most vacuum
failures, like alternator failures are total and rapid onset with
no hope of useful but degraded performance. A battery and/or
second alternator backs up the main alternator . . . what backs
up your vacuum pump?
> . . . and design the system to
>be easily converted to a dual alternator/essential bus configuration later
>when the inevitable price reductions and improvements arrive with EFIS. I
>just ordered the servo kit for the S-Tec model 30, so I'll have the
>autopilot on the electrical bus if the vacuum pump gives out just as a
>backup.
I don't understand your reasoning. When you go all electric with
a small alternator on the vacuum pump pad, you have THREE independent
sources of power to run the whole suite of instruments. Further, no
single failure takes down both gyros. How does a vacuum powered
system offer any more comfort than this?
Bob . . .
Message 12
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| Subject: | Re: Wire (ing) Questions |
--> AeroElectric-List message posted by: DHPHKH@aol.com
<<Our Murphy Moose will be powered by the M-14PF radial engine....We will be
running dual alternators using the B&C 8Amp back up and a single battery.>>
Don,
I'm curious about the physical arrangement of two alternators on an M14.
How is that done?
Dan Horton
Message 13
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| Subject: | Re: Wiring issues at the wing root |
--> AeroElectric-List message posted by: "Lynwood Stagg" <woody6@yahoo.com>
----- Original Message -----
From: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
Subject: Re: AeroElectric-List: Wiring issues at the wing root
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
>
> At 10:51 AM 1/17/2003 -0500, you wrote:
> >--> AeroElectric-List message posted by: "Lynwood Stagg"
<woody6@yahoo.com>
> >
> >Thanks Randy. I had not run across your site yet. Very helpful.
> >
> >With the Whelen install kit for strobes, the 3 conductor cable has a
shield
> >for attach at the power supply end. Did you just run this through the
wing
> >root connector too? I wasn't sure how this would impact the shielding
> >re:noise.
>
> The wing root connectors thing comes around periodically.
> Keep in mind that every connector you put in a wire bundle
> adds three new joints to every wire. I am flying airplanes
> that are 40 years old and never had the wings removed.
> Does the convenience of the wing root connector(s) offset
> the decreased reliability that every connector adds?
> If it were my airplane, I'd leave long pigtails hanging
> out of the wing roots for wing wiring that would be left
> un-connected until final mating of wings to fuselage.
>
> Wire routing would leave enough slack for about a 6"
> diameter "service loop" of wire in each bundle. Should
> the wings require removal at some later date, there is
> sufficient slack in the wires to allow cutting and splicing
> with PIDG butt-splices . . . nearly as reliable as original
> wire.
>
After thinking about this over the last few days, and not wanting to install
all those connectors, I ran the wires with lots of slack at the root. Coils
up nicely out of the way, and I will finish routing at final assembly at the
airport. Hopefully I left enough slack, but even if I end up with a
butt-splice or two, I figure I'm ahead of the game, and I don;t have to
worry about the shielding and noise, etc.
Thanks for the info
Woody
> snip
Message 14
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--> AeroElectric-List message posted by: czechsix@juno.com
Hi Bob, I have a few questions on Z-13:
1) I'm wondering if there's any compelling reason not to eliminate the
6-slot fuseblock you show for the always hot battery bus in favor of more
direct connections. Specifically, I am running dual Lightspeed ignitions
so the connection to the battery is absolutely critical to engine
operation. I'm thinking about connecting the wires to the Lightspeeds
directly to the + battery lead (perhaps by crimping/soldering them in
right with the ring terminal) and using fusible links for protection.
This eliminates the connection at the master relay and another one at the
fuseblock as potential single point failures (I know they are robust
connections, but nevertheless, they have to increase the odds of failure
at least slightly...). The only other connections to the battery bus
would be the e-buss alternate path, which I would connect to the master
relay (battery side terminal) and protect with a fusible link, and the
clock power which I could connect also from the relay and use a 1 A
inline fuse. Any disadvantages to going this route?
2) What is the purpose of the fusible link shown between the e-bus
switch and the e-bus? The only thing I can think of is to protect the
wire to the switch during normal operations where power is coming through
the diodes and there's no upstream protection. Is this correct? I have a
friend who took the e-bus normal power via the diodes from a 7 A fuse on
the main bus fuseblock. Would this be an acceptable alternative to the
fusible link technique? I suppose the downside is that if the wire to
the switch shorted to ground, it would then take out everything on the
e-bus instead of just the fuselink....is that the reason for the proposed
architecture?
3) Z-13 shows a 3 A fuse supplying power to the B&C voltage regulator OV
Sense pins and the low voltage lamp. Other Z drawings show a 2 A fuse
for the same thing. I'm thinking about eliminating the low voltage lamp
altogether since I have a Grand Rapids EIS engine monitor that has a
flashing light alarm for low voltage so the v. regulator lamp is
redundant. If I eliminate the lamp, can I just use a 1 A fuse for the OV
sense input to the regulator? Do I need to replace the low voltage lamp
with a resistor of any sort or will it be fine just to leave that pin
disconnected entirely?
Thanks as always for the help,
--Mark Navratil
Cedar Rapids, Iowa
RV-8A N2D engine hung today (yippeeeee!!) so it's on to FWF stuff......
Message 15
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--> AeroElectric-List message posted by: "Larry Bowen" <Larry@BowenAero.com>
What's the standard practice for shielded wire? One source says both
ends of the shield should go to ground. Another source says only one end
should be grounded. Who is right? Does it depend on the situation?
For example, avionics vs. engine-related stuff vs. xxx.
Thx,
-
Larry Bowen
Larry@BowenAero.com
http://BowenAero.com
2003: The year of flight!
Message 16
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| Subject: | Re: Z-13 questions |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 08:08 PM 1/18/2003 -0600, you wrote:
>--> AeroElectric-List message posted by: czechsix@juno.com
>
>Hi Bob, I have a few questions on Z-13:
>
>1) I'm wondering if there's any compelling reason not to eliminate the
>6-slot fuseblock you show for the always hot battery bus in favor of more
>direct connections. Specifically, I am running dual Lightspeed ignitions
>so the connection to the battery is absolutely critical to engine
>operation. I'm thinking about connecting the wires to the Lightspeeds
>directly to the + battery lead (perhaps by crimping/soldering them in
>right with the ring terminal) and using fusible links for protection.
>This eliminates the connection at the master relay and another one at the
>fuseblock as potential single point failures (I know they are robust
>connections, but nevertheless, they have to increase the odds of failure
>at least slightly...). The only other connections to the battery bus
>would be the e-buss alternate path, which I would connect to the master
>relay (battery side terminal) and protect with a fusible link, and the
>clock power which I could connect also from the relay and use a 1 A
>inline fuse. Any disadvantages to going this route?
Why are you agonizing over a failure of these components? Are they
the ONLY components capable of failure in that system? Do you not
plan to have two ignition systems? In your OBAM aircraft you are
free to wire as you wish but I think you're swatting at a swarm
of gnats with a popsicle stick . . .
>2) What is the purpose of the fusible link shown between the e-bus
>switch and the e-bus? The only thing I can think of is to protect the
>wire to the switch during normal operations where power is coming through
>the diodes and there's no upstream protection. Is this correct?
That's what fusible links, fuses and other circuit protective
devices do . . . the lead from battery contactor to e-bus alternate
feed switch is of considerable length and is probably tied in with
other wires. If you don't have a battery bus, then a fusible link
is suggested. If you DO have a battery bus, then the alternate
feed pat can get protection via one of the battery bus fuses.
>I have a
>friend who took the e-bus normal power via the diodes from a 7 A fuse on
>the main bus fuseblock.
that doesn't hurt anything. If the e-bus and main bus are right
next to each other such that the leads to the diode are 6"
or less, it's permissible to forego protection of these wires
in a certified ship.
> Would this be an acceptable alternative to the
>fusible link technique? I suppose the downside is that if the wire to
>the switch shorted to ground, it would then take out everything on the
>e-bus instead of just the fuselink....is that the reason for the proposed
>architecture?
I lost you here. Which "wire to the switch? source side or
e-bus side?
>3) Z-13 shows a 3 A fuse supplying power to the B&C voltage regulator OV
>Sense pins and the low voltage lamp. Other Z drawings show a 2 A fuse
>for the same thing. I'm thinking about eliminating the low voltage lamp
>altogether since I have a Grand Rapids EIS engine monitor that has a
>flashing light alarm for low voltage so the v. regulator lamp is
>redundant.
It's cheap and you've already paid for it. Why not install it?
> If I eliminate the lamp, can I just use a 1 A fuse for the OV
>sense input to the regulator? Do I need to replace the low voltage lamp
>with a resistor of any sort or will it be fine just to leave that pin
>disconnected entirely?
That pin must be connected whether or not you install the light.
A fuse of 1 to 5A would protect the 22AWG wire that feeds this
pin.
Bob . . .
Message 17
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--> AeroElectric-List message posted by: "Jim V. Wickert" <JimW_btg@compuserve.com>
Larry,
From over thirty years of noise supression for analog and other line
problems it is one end of the shield grounded because with two you create a
loop. And they you chase it for ever.
Jim Wickert
Vision #159
Message 18
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| Subject: | Manassas VA Seminar Date Set |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
EAA chapter 186 has offered to host a seminar
on the weekend of June 7/8, 2003. We did a program
in Manassas about 3 years ago. We've had a number
of requests for a repeat performance. Would appreciate
it if folks on this list would spread the word to any
other lists on which you participate, assuming of course
that the list's rules will permit it.
Links to the seminar programs description and Manassas
sign up page are:
http://www.aeroelectric.com/seminars/seminars.html
http://www.aeroelectric.com/seminars/Manassas.html
Thanks!
Bob . . .
|-------------------------------------------------------|
| The man who does not read good books has no advantage |
| over the man who cannot read them. |
| - Mark Twain |
|-------------------------------------------------------|
Message 19
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| Subject: | Re: Shielded wire |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 09:23 PM 1/18/2003 -0500, you wrote:
>--> AeroElectric-List message posted by: "Larry Bowen" <Larry@BowenAero.com>
>
>What's the standard practice for shielded wire? One source says both
>ends of the shield should go to ground. Another source says only one end
>should be grounded. Who is right? Does it depend on the situation?
>For example, avionics vs. engine-related stuff vs. xxx.
Shields can be used for (1) breaking the electro-static
coupling mode between adjacent wires where it is generally
desirable to ground only ONE end of the shield and/or
(2) part of a signal conduction pathway where BOTH ends
of the shield may be connected. In the later case,
electro-static shielding is available . . . the shield
just does double duty.
Installation instructions for the product should be
explicit as to how shields are treated in their
particular situation.
There are no hard and fast rules for shield termination.
It's also true that shields are often mis-used and create
un-anticipated problems. When in doubt, talk to the
designer and/or service rep for the system you're working
with . . . and feel free to dump on them a bit if their
instructions are found lacking.
Bob . . .
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