Today's Message Index:
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1. 07:52 AM - Re: Fw: Shower of Sparks Help (Robert L. Nuckolls, III)
2. 10:03 AM - Re: Borescopes and sparkplug holes (marcausman)
3. 11:09 AM - Re: Wire Protection Question (Robert L. Nuckolls, III)
4. 12:15 PM - Re: Tyco Breakers (dhammer)
5. 05:25 PM - Re: Re: Borescopes and sparkplug holes (Robert Borger)
Message 1
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| Subject: | Re: Shower of Sparks Help |
At 10:38 PM 6/19/2009, you wrote:
>Thanks again Bob for sharing your expertise...
My pleasure sir.
>I'll confirm that the vibrator is working and troubleshoot the
>system as suggested, but before I do, could you please help me with
>a couple more questions I have about the SOS system? With
>reference to the wire between the LR terminal on the switch and the
>retard breaker on the left mag, is this suppose to be a shielded
>wire with the shield running to GND the same as the L & R
>p-lead? If not, what would be the consequences of using a shielded
>wire with the shield running to the switch ground. I know I used
>shielded wire for the retard breaker, but can't recall if I ran the
>shield to ground. I haven't had a chance to pull the switch yet to check.
This lead is 'hot' only while cranking the
engine and doesn't represent a potential noise
source after the engine is running. I've seen
systems where the designer shielded all the wires
but most will leave this one un-shielded.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
Message 2
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| Subject: | Re: Borescopes and sparkplug holes |
This doesn't answer your post directly but you might find it interesting: http://www.vansairforce.com/community/showthread.php?t=42872
--------
Marc Ausman
http://www.verticalpower.com
RV-7 IO-390 Flying
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=249232#249232
Message 3
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| Subject: | Re: Wire Protection Question |
>First, thank you for your response to my original question. If I am
>following your logic: A fat wire, if shorted to airframe
>ground, will burn away the nearby aluminum ground fault very
>quickly, and thereby eliminate the immediate problem.
>
>If that is so, then the next question would seem to be: Why protect
>the relatively short B-Lead that goes to-from the alternator, as it
>can be easily physically protected in a similar manner to the bus feed wire.
Because the fault risk there is not to the
wire itself but for the potential of diodes
shorting in the alternator. This failure
would probably burn wires in the alternator.
That's probably the least "useful" of the fat-wire
feeder fuses. Probability of diodes shorting
in modern alternators is exceedingly low.
That fuse or breaker can probably be eliminated
with little risk. Cars have never used
this fuse. Early cars burned some wires . . .
later ones added fusible links in the system
to limit the amount of wire that needed to
be replaced after a "burn".
>And a second question: Why use an AWG-6 wire to supply a main bus
>that only has a 20 amp max load?
Because to qualify as a fat-feeder with
little use for protection, the wire needs to
be more robust than the fault site conductors that
would put it at risk. We protect the little
guys because flying faults will often burn
them . . . a distribution fat-wire unworthy of
protection needs to be in the robust class.
I've never seen any rules of thumb but my
sense is that wires in the 10 to 6AWG range
are in a grey area and I'd probably fuse them.
A short 6AWG or larger bus feeder is probably
good to go without specific protection other than
extra attention to support and isolation from
potentially hazardous mechanical damage.
>Struggling to understand in a few weeks what you have learned in an
>entire career!!!!............
No hurry my friend. We've got all the time
you need.
Bob . . .
---------------------------------------
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
---------------------------------------
Message 4
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| Subject: | Re: Tyco Breakers |
[quote]
But I am not, which is the source of our differing approach.
My friend, the rich man's chief pilot, has just spent a
large part of the last seven years fighting with the maker
of their new model $47 million private jet over the fact
they wanted to make all the fuses totally inaccessible in
flight. Manufacturer lost the argument. Same principle
applies to single pilot small aircraft with the automobile
style fuse block.
Tom Kuffel[/quote]
Tom,
I spend my life with private Jets. I've never seen fuses in the cockpit, only
circuit breakers. Any fuses or current limiters in transport category aircraft,
and there are hundreds, are always located where the crew can't touch them,
along with many of the breakers they don't want the pilot to have access to.
You just don't want some stupid pilot starting a fire playing with them. The
rule that has always been pounded into my head is to accept the loss and fly
the plane, not try and fix it. That's how L-1011's end up in the swamp while
pilots are trying to change gear indicator bulbs.
The only aircraft I'm aware of that has few, but not no, breakers in the cockpit
is Bombardier's Global Express. It does, however, have remote breakers controlled
by screens in the cockpit. It saves a huge amount of weight running wires
all the way from the hell hole to the cockpit and back. Also the usability
for the crew goes way up. They can see all systems effected when a breaker
is popped and can isolate a bus at will. Also, if one pops you get a message.
That being said, no manufacturer is going to change his Type Certificated product
based on the whims of some ego-centric pilot. Funny, but the buyer of that
$47M aircraft is sitting in the back. That's the ones the manufacturer's listen
to and not the hired hands up front. Trust me on that one.
Cockpits and panel layout of all new aircraft are now part of the certificate and
short of adding a third something cannot be altered without a big STC project.
I'd be interested in knowing what aircraft model you are talking about.
Cheers,
Don
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=249246#249246
Message 5
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| Subject: | Re: Borescopes and sparkplug holes |
Marc,
VERY COOL! Thanks!
Bob Borger
Europa Kit #A221 N914XL, XS Mono, Intercooled 914, Airmaster C/S
http://www.europaowners.org/N914XL
Aircraft Flying!
3705 Lynchburg Dr.
Corinth, TX 76208
Home: 940-497-2123
Cel: 817-992-1117
On Jun 20, 2009, at 11:58, marcausman wrote:
> >
>
> This doesn't answer your post directly but you might find it
> interesting: http://www.vansairforce.com/community/showthread.php?t=42872
>
> --------
> Marc Ausman
> http://www.verticalpower.com
> RV-7 IO-390 Flying
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=249232#249232
>
>
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