Today's Message Index:
----------------------
1. 03:12 AM - Re: Unprotected Feeder in Z Drawings (jan)
2. 04:29 AM - Re: Unprotected Feeder in Z Drawings (Ken)
3. 07:10 AM - Re: Unprotected Feeder in Z Drawings (user9253)
4. 09:31 AM - Re: Unprotected Feeder in Z Drawings (Robert L. Nuckolls, III)
5. 09:39 AM - Re: Unprotected Feeder in Z Drawings (Robert L. Nuckolls, III)
6. 10:38 AM - Re: Unprotected Feeder in Z Drawings (R. curtis)
7. 01:23 PM - Re: Unprotected Feeder in Z Drawings (Jeff Luckey)
8. 02:20 PM - Re: Unprotected Feeder in Z Drawings (jan)
9. 02:20 PM - Re: Unprotected Feeder in Z Drawings (Henador Titzoff)
10. 04:27 PM - Re: Unprotected Feeder in Z Drawings (Jared Yates)
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| Subject: | Unprotected Feeder in Z Drawings |
Hi Jeff,
Interesting story. My take on this is simply a question of 'risk
management'. Lets say that ALL planes that do not have this 'extra fuse' now
suddenly get this 'extra fuse' .. do you think the risk is higher that
something goes wrong with the fuse .. the extra connectors to fit the fuse
.. how the fuse is fitted .. how it is potentially fitted incorrectly etc...
IF .. the only case of 'something bad happened because this wire is not
fused' is the incident that you mention below .. Well ... what do you think
is more likely to happen ....
Something wrong will all the 1000 of planes that now have 'one more part
that can go wrong' i.e. the extra fuse ... or a pen or something else
lodging against the bus and shorting to ground ?
On YOUR plane ... how easy is it for anything to actually lodge in the same
place ? Suggest looking at best way to prevent something to lodge and short
.. than to add something that has never been seen a 'required' before ....
I agree that there are very few things that are absolutely right or
absolutely wrong .. (apart from when at school ;-) ...then everything was
always very black and white ..
The more you can 'remove from the plane' the less you have that can go wrong
... what you are 'left with' ...well .. you just need to analyze the risk
and what happens when it fail .. can you reduce the risk ... without adding
another risk ..
The following is not related to aircrafts .. but I like to use it to make
people thing about risk .. and how to reduce accidents .... I have no idea
if it would work .. but you could argue the case ..
The general thought of car safety is to add more things .. seat belts -
airbags - crumble zones etc etc.. list goes on and on ...
The net results is that we tend to drive faster .. We have more accidents ..
maybe less people would die .. but then compared to what ?
Here is my idea for the ultimate car safety device .. You remove seat belts
and you make it a legal requirement that ALL steering wheels must have a 6"
spike mounted in the centre .. pointing straight at your chest .. (and NO ..
you can not wear a bullet proof west :-) ..)
Now you know ... if you do not drive very carefully, no hard braking etc...
... you are not going to last very long are you ? Looking at that 6" spike
at the steering wheel.
Sure some people will die ..and some people who are driving very carefully
will be hit by someone who does not ... But will the OVERALL number of
accidents go up or go down ??
:-)
Enjoy the weekend ! I
Jan
PS : will not be fitting a fuse on that wire ... But I will look very very
closely at how it is run .....
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Jeff
Luckey
Sent: 07 December 2013 01:38
Subject: Re: AeroElectric-List: Unprotected Feeder in Z Drawings
Bob,
Ok, I don't disagree w/ any of the points made but let's play the Devil's
Advocate/Worst Case Scenario game.
Several years ago in Germany Pilot A was flying an Extra 300 and he looses
his pen. He finishes his flight but forgets to recover the pen. A few days
later Pilot B takes the plane through several aerobatic maneuvers which
dislodge the pen from where it was hiding and wedge it between the buss on
the back of the breakers and the airframe causing a fault to ground. Smoke
in the cockpit, panic, denial, etc but eventually Pilot B does the right
thing and kills the master, lands plane, changes underwear, semi-happy
ending. Good News: engine not electrically-dependent so engine keeps
running:)
Bad News: The plane requires some serious re-wire because the feeder melted
other wires in the loom. Sure, no one died but I certainly don't want to be
Pilot B! If that feeder had been fused there would have been no smoke and
no damage to wiring.
The point is that simply installing the feeder w/ care & craftsmanship may
not be enough. No matter how well that feeder was installed, it would have
made no difference in this scenario. Unforeseen circumstances could make
for a bad day for your electrical system. It may be impossible to foresee
all possible bad scenarios so we want the design of the system to be as
fault tolerant as possible.
Perhaps putting a fuse in the feed line may be a "belt & suspenders"
approach but I still don't see a real down side and, like I mentioned
earlier, I sure don't want to be Pilot B.
BTW Bob (and all) I certainly enjoy being able to explore & discuss these
issues in cordial & intelligent ways - whether or not there's a right or
wrong answer, I always learn something.
-Jeff
_____
From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
Sent: Friday, December 6, 2013 10:29 AM
Subject: Re: AeroElectric-List: Unprotected Feeder in Z Drawings
<nuckolls.bob@aeroelectric.com <mailto:nuckolls.bob@aeroelectric.com> >
>
> That particular wire between battery feeders and distribution busses has
existed in perhaps a quarter million production aircraft over the past 80+
years and to my knowledge, has never been fitted with such protection.
>
> I find that fascinating...
>
> In my relatively simple mind I consider adding a fuse to the feeder
> in question to have little or no down side and potentially huge
> upside - preventing an in-flight fire. (not a fan of in-flight fires)
Consider the consequences of opening that fuse
(or any other event causing that pathway to open)
in a TC aircraft. You loose EVERYTHING on the panel.
I.e. single point of failure for all accessories.
Yeah but . . . if the fuse opens, then there was
something 'wrong'.
Yes, but what? The FEMA process calls for hypothesizing
every kind of event that can open the fuse and either (1)
crafting a plan-b or (2) suppressing the risk.
> So the downside is that there could be some innocuous event
> that I am unaware of which pops the proposed big fuse
> unnecessarily. (sounds a little ridiculous, but carry on...)
> I can't think of anything like that but I'm not a genius so I
> thought I'd throw it out to The List to see if its collective
> wisdom knows about something I may have overlooked.
We have a huge data base from which to conduct that
assessment not the least of which are big bunches of
airplanes smaller bunches of qualification studies
and relatively tiny bunches of incidences that bent
aluminum and maybe even broke bones.
The NTSB narrative on aircraft accidents is accessible
here . . .
http://tinyurl.com/pqcdj4h
Do a random search of FINAL REPORTS with your senses
attuned to causation with roots in human failings
(either in operation, maintenance or design) and those
which have causation in some physical failure
mechanism.
Instances that speak to any electrical will fall into
the second category for causation and will be a
minuscule portion of the whole . . . and
of those, faulting of a wire to ground is even
smaller.
In 40 years of flying, 1000+ hrs as pilot and
probably another 2000 as passenger/observer, I've
observed only two incidences of a popped breaker in
flight. NEITHER of those cases had root cause in a
wire faulted to ground - the fault needed to open
your proposed fuse.
The foundation for moving circuit protection off
the panel and reverting back to fuses is predicated
on similar experiences by thousands of other pilots.
Experiences suggesting that dedicating dollars, panel
space, weight and fabrication time to a breaker-panel
is not a good return on investment.
Bottom line is that you're many, many times more
likely to have a bad day in the cockpit for reasons
far removed from a hard ground fault on your 6AWG
bus feeder . . . and THAT because you didn't conduct
due diligence in its installation.
Same thing applies to torque on your prop bolts,
replacing a tire that's flopping cordage, taking
an extra close look at forecasts during icing season,
and a host of things we do that go to reducing
risk.
In the case of the bus feeder, the risks are not
so much to the wire as to the thing the wire touches.
Case in point: C90 on short final experiences disconnect
of elevator cables. Pilot uses trim commands and power to
execute go-around, assesses the condition and successfully
lands the airplane with rudder, trim and power.
Pulling up floorboards in the cockpit revealed a 40A
protected feeder to the windshield de-ice inverter
had been mis-positioned against the elevator control
cable during a maintenance operation. Over what had to
be many hours of operation, motion of the cable wore
through the insulation bringing the cable into contact
with the hot wire. The arcing and sparking was of
insufficient intensity to come to attention of crew
in spite of the fact that it was going on virtually
under their feet.
The copper wire was barely damaged. The breaker never
popped while the elevator cable eventually eroded through
and parted. Compare thermal properties of copper versus
steel . . . this explains why the best steel safes have
intermediate layers of copper in their construction. It's
EASY to burn through steel . . . next to impossible on copper.
This narrative explains the high order probability that
even if you DID get your 6AWG feeder faulted to
ground, it's most likely to be a soft fault that
burns a hole in your airplane while doing little
damage to the wire . . . and certainly far short of
getting it to smoke and/or open a fuse/breaker.
Adding 'protection' to this pathway doubles the
number of joints in the pathway and adds nothing
demonstrable in terms of fault response . . . which
is why the spam-can builders don't do it either.
Bob . . .
http://www.matronics.com/Navigator?AeroElectric-Lista
href="http://forums.matronics.com/"
target="_blank">http://forums.mat===================
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<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>Hi
Jeff,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>Interesting story. My take
on this
is simply a question of ‘risk management’. Lets say that
ALL planes
that do not have this ‘extra fuse’ now suddenly get this
‘extra
fuse’ .. do you think the risk is higher that something goes
wrong with
the fuse .. the extra connectors to fit the fuse .. how the fuse is
fitted ..
how it is potentially fitted incorrectly
etc…<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>IF .. the only case of
‘something
bad happened because this wire is not fused’ is the incident that
you mention
below .. Well … what do you think is more likely to happen
….<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>Something wrong will all the 1000
of
planes that now have ‘one more part that can go wrong’ i.e.
the
extra fuse … or a pen or something else lodging against the
bus and
shorting to ground ?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>On YOUR plane … how easy is
it for
anything to actually lodge in the same place ? Suggest looking at
best
way to prevent something to lodge and short .. than to add something
that has
never been seen a ‘required’ before
….<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>I agree that there are very few
things
that are absolutely right or absolutely wrong .. (apart from when at
school ;-)
…then everything was always very black and white
..<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>The more you can ‘remove
from the
plane’ the less you have that can go wrong … what you are
‘left
with’ …well .. you just need to analyze the risk and what
happens
when it fail .. can you reduce the risk … without adding another
risk .. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>The following is not related to
aircrafts
.. but I like to use it to make people thing about risk .. and how to
reduce accidents
…. I have no idea if it would work .. but you could argue
the case
..<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>The general thought of car safety
is to
add more things .. seat belts – airbags – crumble zones etc
etc..
list goes on and on …<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>The net results is that we tend to
drive
faster .. We have more accidents .. maybe less people would die .. but
then
compared to what ? <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>Here is my idea for the ultimate
car
safety device .. You remove seat belts and you make it a legal
requirement that
ALL steering wheels must have a 6” spike mounted in the centre ..
pointing straight at your chest .. (and NO .. you can not wear a bullet
proof
west </span></font><font size=2 color=navy face=Wingdings><span
style='font-size:10.0pt;font-family:Wingdings;color:navy'>J</span></fo
nt><font
size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;
color:navy'> ..)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>Now you know … if you do not
drive
very carefully, no hard braking etc… … you are not going to
last
very long are you ? Looking at that 6” spike at the steering
wheel.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>Sure some people will die ..and
some people
who are driving very carefully will be hit by someone who does not
…
But will the OVERALL number of accidents go up or go down
??<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Wingdings><span
style='font-size:10.0pt;font-family:Wingdings;color:navy'>J</span></fo
nt><font
size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;
color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>Enjoy the weekend ! I
<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>Jan<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'>PS : will not be fitting a fuse on
that
wire … But I will look very very closely at how it is run
…..<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<div class=MsoNormal align=center style='text-align:center'><font
size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span
style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] <b><span
style='font-weight:bold'>On Behalf Of </span></b><st1:PersonName
w:st="on">Jeff
Luckey</st1:PersonName><br>
<b><span style='font-weight:bold'>Sent:</span></b> 07 December 2013
01:38<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName
w:st="on">aeroelectric-list@matronics.com</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re:
AeroElectric-List:
Unprotected Feeder in Z Drawings</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal style='background:white'><st1:PersonName
w:st="on"><font
size=3 color=black face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;
color:black'>Bob</span></font></st1:PersonName><font color=black
face=Tahoma><span
style='font-family:Tahoma;color:black'>, <br>
<br>
Ok, I don't disagree w/ any of the points made but let's play the
Devil's
Advocate/Worst Case Scenario game.<br>
<br>
Several years ago in Germany Pilot A was flying an Extra 300 and he
looses his
pen. He finishes his flight but forgets to recover the pen.
A few
days later Pilot B takes the plane through several aerobatic maneuvers
which
dislodge the pen from where it was hiding and wedge it between the buss
on the
back of the breakers and the airframe causing a fault to ground.
Smoke in
the cockpit, panic, denial, etc but eventually Pilot B does the right
thing and
kills the master, lands plane, changes underwear, semi-happy
ending. Good
News: engine not electrically-dependent so engine keeps running:)<br>
<br>
Bad News: The plane requires some serious re-wire because the feeder
melted
other wires in the loom. Sure, no one died but I certainly don't
want to
be Pilot B! If that feeder had been fused there would have been
no smoke
and no damage to wiring.<o:p></o:p></span></font></p>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'><o:p> </o
:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'>The
point is that simply installing the feeder w/ care & craftsmanship
may not
be enough. No matter how well that feeder was installed, it would
have
made no difference in this scenario. Unforeseen circumstances
could make
for a bad day for your electrical system. It may be impossible to
foresee
all possible bad scenarios so we want the design of the system to be as
fault
tolerant as possible.<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'><o:p> </o
:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'>Perhaps
putting a fuse in the feed line may be a "belt &
suspenders"
approach but I still don't see a real down side and, like I mentioned
earlier,
I sure don't want to be Pilot B.<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'><o:p> </o
:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'>BTW
<st1:PersonName
w:st="on">Bob</st1:PersonName> (and all) I certainly enjoy being able
to
explore & discuss these issues in cordial & intelligent ways -
whether
or not there's a right or wrong answer, I always learn
something.<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'><o:p> </o
:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 color=black face=Tahoma><span
style='font-size:
12.0pt;font-family:Tahoma;color:black'>-Jeff<o:p></o:p></span></font></p
>
</div>
<div>
<p class=MsoNormal><font size=3 color=black face=Tahoma><span
style='font-size:
12.0pt;font-family:Tahoma;color:black'><o:p> </o:p></span></font></
p>
</div>
<div>
<div>
<div>
<div class=MsoNormal align=center
style='text-align:center;background:white'><font
size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;
color:black'>
<hr size=1 width="100%" align=center>
</span></font></div>
<p class=MsoNormal style='background:white'><b><font size=2
color=black
face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:black;
font-weight:bold'>From:</span></font></b><font size=2 color=black
face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:black'> "Robert
L.
Nuckolls, III" <nuckolls.bob@aeroelectric.com><br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName
w:st="on">aeroelectric-list@matronics.com</st1:PersonName>
<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, December
6, 2013
10:29 AM<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re:
AeroElectric-List:
Unprotected Feeder in Z Drawings</span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal
style='margin-bottom:12.0pt;background:white'><font size=3
color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'><br>
--> AeroElectric-List message posted by: "Robert L. Nuckolls,
III"
<<a href="mailto:nuckolls.bob@aeroelectric.com"
ymailto="mailto:nuckolls.bob@aeroelectric.com">nuckolls.bob@aeroelectr
ic.com</a>><br>
<br>
<br>
> <br>
> That particular wire between battery feeders and distribution
busses has
existed in perhaps a quarter million production aircraft over the past
80+
years and to my knowledge, has never been fitted with such
protection.<br>
> <br>
> I find that fascinating...<br>
> <br>
> In my relatively simple mind I consider adding a fuse to the
feeder<br>
> in question to have little or no down side and potentially
huge<br>
> upside - preventing an in-flight fire. (not a fan of in-flight
fires)<br>
<br>
Consider the consequences of opening that fuse<br>
(or any other event causing that pathway to open)<br>
in a TC aircraft. You loose EVERYTHING on the panel.<br>
I.e. single point of failure for all accessories.<br>
<br>
Yeah but . . . if the fuse opens, then there was<br>
something 'wrong'.<br>
<br>
Yes, but what? The FEMA process calls for
hypothesizing<br>
every kind of event that can open the fuse and either (1)<br>
crafting a plan-b or (2) suppressing the risk.<br>
<br>
<br>
> So the downside is that there could be some innocuous event<br>
> that I am unaware of which pops the proposed big fuse<br>
> unnecessarily. (sounds a little ridiculous, but carry
on...)<br>
> I can't think of anything like that but I'm not a genius so I<br>
> thought I'd throw it out to The List to see if its collective<br>
> wisdom knows about something I may have overlooked.<br>
<br>
We have a huge data base from which to conduct that<br>
assessment not the least of which are big bunches of<br>
airplanes smaller bunches of qualification studies<br>
and relatively tiny bunches of incidences that bent<br>
aluminum and maybe even broke bones.<br>
<br>
The NTSB narrative on aircraft accidents is accessible<br>
here . . .<br>
<br>
http://tinyurl.com/pqcdj4h<br>
<br>
Do a random search of FINAL REPORTS with your senses<br>
attuned to causation with roots in human failings<br>
(either in operation, maintenance or design) and those<br>
which have causation in some physical failure<br>
mechanism.<br>
<br>
Instances that speak to any electrical will fall into<br>
the second category for causation and will be a<br>
minuscule portion of the whole . . . and<br>
of those, faulting of a wire to ground is even<br>
smaller.<br>
<br>
In 40 years of flying, 1000+ hrs as pilot and<br>
probably another 2000 as passenger/observer, I've<br>
observed only two incidences of a popped breaker in<br>
flight. NEITHER of those cases had root cause in a<br>
wire faulted to ground - the fault needed to open<br>
your proposed fuse.<br>
<br>
The foundation for moving circuit protection off<br>
the panel and reverting back to fuses is predicated<br>
on similar experiences by thousands of other pilots.<br>
Experiences suggesting that dedicating dollars, panel<br>
space, weight and fabrication time to a breaker-panel<br>
is not a good return on investment.<br>
<br>
Bottom line is that you're many, many times more<br>
likely to have a bad day in the cockpit for reasons<br>
far removed from a hard ground fault on your 6AWG<br>
bus feeder . . . and THAT because you didn't conduct<br>
due diligence in its installation.<br>
<br>
Same thing applies to torque on your prop bolts,<br>
replacing a tire that's flopping cordage, taking<br>
an extra close look at forecasts during icing season,<br>
and a host of things we do that go to reducing<br>
risk.<br>
<br>
In the case of the bus feeder, the risks are not<br>
so much to the wire as to the thing the wire touches.<br>
<br>
Case in point: C90 on short final experiences
disconnect<br>
of elevator cables. Pilot uses trim commands and power to<br>
execute go-around, assesses the condition and successfully<br>
lands the airplane with rudder, trim and power.<br>
<br>
Pulling up floorboards in the cockpit revealed a 40A<br>
protected feeder to the windshield de-ice inverter<br>
had been mis-positioned against the elevator control<br>
cable during a maintenance operation. Over what had to<br>
be many hours of operation, motion of the cable wore<br>
through the insulation bringing the cable into contact<br>
with the hot wire. The arcing and sparking was of<br>
insufficient intensity to come to attention of crew<br>
in spite of the fact that it was going on virtually<br>
under their feet.<br>
<br>
The copper wire was barely damaged. The breaker never<br>
popped while the elevator cable eventually eroded through<br>
and parted. Compare thermal properties of copper
versus<br>
steel . . . this explains why the best steel safes have<br>
intermediate layers of copper in their construction. It's<br>
EASY to burn through steel . . . next to impossible on
copper.<br>
<br>
This narrative explains the high order probability that<br>
even if you DID get your 6AWG feeder faulted to<br>
ground, it's most likely to be a soft fault that<br>
burns a hole in your airplane while doing little<br>
damage to the wire . . . and certainly far short of<br>
getting it to smoke and/or open a fuse/breaker.<br>
<br>
Adding 'protection' to this pathway doubles the<br>
number of joints in the pathway and adds nothing<br>
demonstrable in terms of fault response . . . which<br>
is why the spam-can builders don't do it either.<br>
<br>
<br>
<br>
<st1:PersonName w:st="on">Bob</st1:PersonName> . . . <br>
<bsp;
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Message 2
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| Subject: | Re: Unprotected Feeder in Z Drawings |
OTOH with Blue Sea type remote fuse panels installed at the battery, I
have no exposed bus bars. Feeders to the fuse panels are a couple of
inches long but not exposed. My starter feeder is hot when the master is
on but no big deal turning off the master in flight for me if need be.
So no exposed always hot feeders and no CB's cluttering up the
instrument panel.
Ken
On 06/12/2013 8:38 PM, Jeff Luckey wrote:
> Bob,
>
> Ok, I don't disagree w/ any of the points made but let's play the
> Devil's Advocate/Worst Case Scenario game.
>
> Several years ago in Germany Pilot A was flying an Extra 300 and he
> looses his pen. He finishes his flight but forgets to recover the pen.
> A few days later Pilot B takes the plane through several aerobatic
> maneuvers which dislodge the pen from where it was hiding and wedge it
> between the buss on the back of the breakers and the airframe causing a
> fault to ground. Smoke in the cockpit, panic, denial, etc but
> eventually Pilot B does the right thing and kills the master, lands
> plane, changes underwear, semi-happy ending. Good News: engine not
> electrically-dependent so engine keeps running:)
>
> Bad News: The plane requires some serious re-wire because the feeder
> melted other wires in the loom. Sure, no one died but I certainly don't
> want to be Pilot B! If that feeder had been fused there would have been
> no smoke and no damage to wiring.
>
> The point is that simply installing the feeder w/ care & craftsmanship
> may not be enough. No matter how well that feeder was installed, it
> would have made no difference in this scenario. Unforeseen
> circumstances could make for a bad day for your electrical system. It
> may be impossible to foresee all possible bad scenarios so we want the
> design of the system to be as fault tolerant as possible.
>
> Perhaps putting a fuse in the feed line may be a "belt & suspenders"
> approach but I still don't see a real down side and, like I mentioned
> earlier, I sure don't want to be Pilot B.
>
> BTW Bob (and all) I certainly enjoy being able to explore & discuss
> these issues in cordial & intelligent ways - whether or not there's a
> right or wrong answer, I always learn something.
>
> -Jeff
>
Message 3
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| Subject: | Re: Unprotected Feeder in Z Drawings |
If there is a concern about the main feeder shorting to ground, how about making
sure that does not happen instead of adding a fuse? The feeder could be double
insulated where it passes through the firewall. The circuit breaker bus bar
can be insulated. Or better yet, use an insulated fuse block with no exposed
bus.
Even if the main feeder was protected with a fuse, there is no guarantee that
the fuse will blow in the event of a short circuit. Large fuses are difficult
to blow. Many times a short circuit will arc and burn away metal until the
short clears itself, without blowing a fuse.
It is good to question why something has always been done a certain way. On
the other hand, it is hard to argue with success.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=415046#415046
Message 4
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| Subject: | Re: Unprotected Feeder in Z Drawings |
At 07:38 PM 12/6/2013, you wrote:
>Bob,
>
>Ok, I don't disagree w/ any of the points made but let's play the
>Devil's Advocate/Worst Case Scenario game.
>
>Several years ago in Germany Pilot A was flying an Extra 300 and he
>looses his pen. He finishes his flight but forgets to recover the
>pen. A few days later Pilot B takes the plane through several
>aerobatic maneuvers which dislodge the pen from where it was hiding
>and wedge it between the buss on the back of the breakers and the
>airframe causing a fault to ground. Smoke in the cockpit, panic,
>denial, etc but eventually Pilot B does the right thing and kills
>the master, lands plane, changes underwear, semi-happy ending. Good
>News: engine not electrically-dependent so engine keeps running:)
>
>Bad News: The plane requires some serious re-wire because the feeder
>melted other wires in the loom. Sure, no one died but I certainly
>don't want to be Pilot B! If that feeder had been fused there would
>have been no smoke and no damage to wiring.
Okay! A hypothesis. This is step-one in the conduct
of an FMEA for a unique event. Let's apply what we know
about the nature of things and machines to expand our
understanding of this hypothesis and to craft a
reasoned reaction to the result.
I am skeptical of this story based on the limited
data offered . . . which is not unusual. 99.9% of
what I call dark-n-stormy-night stories in the journals
are long on story value and short on data . . . the
narrative of this incident is no different.
Let us consider the processes we have evolved for
the purpose of making secure connections between
fat-wires and some terminus . . . usually a threaded
fastener.
The design goal is to achieve a sub-milliohm connection
between all conductors such that temperature rise at
the connections does not contribute to long term effects
of accelerated corrosion and ultimate failure of the
joint.
I have seen numerous examples of failure-to-implement-
good-practice as manifest by studs burned off, nuts
arc welded to studs, terminals damaged beyond serviceable
condition, etc. Except for the effects of localize heating
at the failed joint, the WIRE crimped into that terminal
was not affected. This is because the dissipation of energy
occurs at the POINT OF HIGHEST RESISTANCE in the loop.
Do the study sometime to figure out why a long piece
of wire suspended between two terminals always burns through
near the center every time.
Okay, consider the rogue debris looking for a place to
do mischief. Aha! exposed bus bar and bare airframe . . .
ideal. Consider the mechanism that brings a metallic
pen into contact with bus and airframe with such conductive
integrity that it places a span of wire at risk . . .
and outlasts the wire during the ensuing contest of
smoke and fire.
The pen would have to (1) possess conductivity capabilities
on a par or better than the at-risk wire and (2) be
held in contact with bus and airframe with sub-milliohm
integrity for a length of time necessary to heat other
components to destructive temperatures.
Another question arising from the narrative is based on
the statement: "The plane requires some serious re-wire
because the feeder melted other wires in the loom."
Again, how did the rogue debris achieve conductive
integrity that had to be a small fraction of that
for the wire(s) being overloaded?
Risks to underwear not withstanding, this pilot's airplane
was obviously wired with attention to the needs of an
electrically dependent engine that was not influenced
by the position of the master switch.
This story yields to a simple study of "where does
the energy go?" Another example: I remember 1969 when
Gordon Wood put a peak-measuring voltmeter on the coil of a
contactor and discovered, "Great galloping gremlins
Batman! Did you see that?"
Yes, discovery of those numbers in a system fitted with
newly minted, solid state radios gave rise for much
concern. But as Gordon deduced (and we've confirmed
in recent years) the energy did not propagate out
onto the bus and is of greatest risk to the controlling
device (master and starter switches). Further, adding
the $1 diode across the coil put that dragon to bed
forever.
Details of simple-ideas aside, the hypothesis you proffered
is a valid component of the FMEA process. It highlighted
something I neglected to included in my earlier
listing of potential risks to pieces of the airplane
with secondary risks to exposed conductors. I neglected
to include loose articles.
The FMEA has to consider not only the details of
how the risks stack together but the environment in
which they occur. Our el-cheepo aerial targets at
Beech were heavily controlled for high reliability (low
risk) missions. Why all the fuss? It's not a man-rated
piece of hardware and expendable. Easy. The $ expended
to set up a mission in which this target would be used
was huge. It orchestrated movements of ships a sea,
flights of training aircraft, called for an accurate
launch of the target from 50,000ft and M1.5 to fly down
a precise track, etc. The expenditures of mission
resources far exceeded the price of our little piece
of throw-away hardware by factors of 1000:1.
Okay, back to your proposed project and concerns for
system reliability. It's not a man-rated weapon so
those sorts of issues don't apply. Do you plan to
conduct negative-g aerobatics wherein loose items
would become a consideration? It would be interesting
if we could search the accident database looking for
incidents where loose articles were major players
in the evolution or outcome of an event. But
for sure, GA aircraft from C-150 to G-5 are seldom
involved in negative-g events . . . and when they
are . . . it's probably not a piece of loose hardware
that drives the outcome.
I advise caution for incorporating 'common knowledge'
into one's deliberations that will burden empty weight, time,
and dollars to reduce risks. You can do a Google search
on my website for these statements:
"I had a Seawind in here yesterday with lots of tiny breakers that
pop all the time. Was a real hassle to work on. Just because a 3 amp
fuse won't blow until it gets to 4 amps isn't the point (which is
known by everyone who deal with these things)"
"Main power bus is fused at 35 Amperes"
"Remember, a fuse or breaker won't hold above 80% of what it says on
the nameplate; so a 50 Amp breaker will pop at 40 amps after 20 or 30 minutes."
. . . which are a small sample of what was widely
distributed as useful information . . . and made yours
truly the target of incoming sand and tomatoes
pitched by acolytes of the author when I questioned the
simple-ideas that supported his statements.
Don't give up on this my friend. If there's a risk yet
un-identified, we all have an interest in knowing what
it is and deducing a mitigating response. At the same
time, be a good scientist. Exploit those recipes for
success with good track records but remain eternally
skeptical of that which is assumed to be valid. The simple-
ideas from which a recipe is crafted are inviolate and
unchanging. It's our skill and understanding of how those
simple-ideas fit together that can get wobbly. They
are always worthy of either re-validation or discounted for
something better.
Bob . . .
Message 5
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| Subject: | Unprotected Feeder in Z Drawings |
>
>Here is my idea for the ultimate car safety
>device .. You remove seat belts and you make it
>a legal requirement that ALL steering wheels
>must have a 6=94 spike mounted in the centre ..
>pointing straight at your chest .. (and NO ..
>you can not wear a bullet proof west J ..)
>
>Now you know =85 if you do not drive very
>carefully, no hard braking etc=85 =85 you are not
>going to last very long are you ? Looking at
>that 6=94 spike at the steering wheel.
>
>Sure some people will die ..and some people who
>are driving very carefully will be hit by
>someone who does not =85 But will the OVERALL
>number of accidents go up or go down ??
Excellent question!
An illuminating peek into the innate perversity of
the human condition. I spent a number of years in
the investigation and modeling of events surrounding
accidents at railroad grade crossings. Cross-bucks
are mandated at every crossing. Some crossings get
lights. Some get lights and gates. The budget for
upgrading safety hardware at the crossing was limited
so only the worst crossings got the full treatment.
It was interesting to note that after gates were
installed at crossings with the highest accident
rates, number of accidents at the crossing only
dropped by half.
Bob . . .
Message 6
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| Subject: | Re: Unprotected Feeder in Z Drawings |
It was interesting to note that after gates were
installed at crossings with the highest accident
rates, number of accidents at the crossing only
dropped by half
You reach a point of no return when you try
to protect people from themselves and their
own stupidity. Granted, some things can
not be avoided, but we now live in a society
where responsibility belongs to someone
else.
Roger
--
Do you have a slow PC=3F Try a Free scan http://www.spamfighter.com/SLOW-PCfi
ghter=3Fcid=sigen
Message 7
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| Subject: | Re: Unprotected Feeder in Z Drawings |
Jan,=0A=0AI'm not sure if you are being serious in this quote (perhaps you
were being facetious?):=0AThe general thought of car safety is to=0Aadd mor
e things .. seat belts =93 airbags =93 crumble zones etc etc..
=0Alist goes on and on =0A=C2-=0AThe net results is that we tend
to drive=0Afaster .. We have more accidents .. maybe less people would die
.. but then=0Acompared to what ? =0A=0AIf you are suggesting that technolo
gy has not made cars safer, that would be an inaccurate assertion.=C2- Th
e advances in motor vehicle safety that you cite have increased safety trem
endously.=C2- See: =0A=0A=0Ahttp://www-fars.nhtsa.dot.gov/Main/index.aspx
=0A=0AAccident rates have plummeted over the past 20 years despite large in
creases in the number of vehicles.=C2- Automotive safety is fantastic exa
mple of making things safer by applying technology.=0A=0A=0A...=0A=0A=0A___
_____________________________=0A From: jan <jan@claver.demon.co.uk>=0ATo: a
eroelectric-list@matronics.com =0ASent: Saturday, December 7, 2013 3:22 AM
=0ASubject: RE: AeroElectric-List: Unprotected Feeder in Z Drawings=0A =0A
=0A=0A =0AHi Jeff,=0A=C2-=0AInteresting story.=C2- My take on this=0Ais
simply a question of =98risk management=99. Lets say that ALL
planes=0Athat do not have this =98extra fuse=99 now suddenly ge
t this =98extra=0Afuse=99 .. do you think the risk is higher th
at something goes wrong with=0Athe fuse .. the extra connectors to fit the
fuse .. how the fuse is fitted ..=0Ahow it is potentially fitted incorrectl
y etc=0A=C2-=0AIF .. the only case of =98something=0Abad h
appened because this wire is not fused=99 is the incident that you me
ntion=0Abelow .. Well what do you think is more likely to happen
.=0A=C2-=0ASomething wrong will all the 1000 of=0Aplanes that no
w have =98one more part that can go wrong=99 i.e. the=0Aextra f
use =C2- or a pen or something else lodging against the bus and
=0Ashorting to ground ?=0A=C2-=0AOn YOUR plane how easy is it f
or=0Aanything to actually lodge in the same place ?=C2- Suggest looking a
t best=0Away to prevent something to lodge and short .. than to add somethi
ng that has=0Anever been seen a =98required=99 before
.=0A=C2-=0AI agree that there are very few things=0Athat are absolutely r
ight or absolutely wrong .. (apart from when at school ;-)=0Athen
everything was always very black and white ..=0A=C2-=0AThe more you can
=98remove from the=0Aplane=99 the less you have that can go wro
ng what you are =98left=0Awith=99 well .. yo
u just need to analyze the risk and what happens=0Awhen it fail .. can you
reduce the risk without adding another risk .. =0A=C2-=0AThe fo
llowing is not related to aircrafts=0A.. but I like to use it to make peopl
e thing about risk .. and how to reduce accidents=0A.=C2- I have
no idea if it would work .. but you could argue the case=0A..=0A=C2-=0AT
he general thought of car safety is to=0Aadd more things .. seat belts
=93 airbags =93 crumble zones etc etc..=0Alist goes on and on
=0A=C2-=0AThe net results is that we tend to drive=0Afaster .. We h
ave more accidents .. maybe less people would die .. but then=0Acompared to
what ? =0A=C2-=0AHere is my idea for the ultimate car=0Asafety device ..
You remove seat belts and you make it a legal requirement that=0AALL steer
ing wheels must have a 6=9D spike mounted in the centre ..=0Apointing
straight at your chest .. (and NO .. you can not wear a bullet proof=0Awes
t J..)=0A=C2-=0ANow you know if you do not drive=0Avery careful
ly, no hard braking etc you are not going to last=0Avery
long are you ? Looking at that 6=9D spike at the steering wheel.=0A
=C2-=0ASure some people will die ..and some people=0Awho are driving very
carefully will be hit by someone who does not =C2-=0ABut will t
he OVERALL number of accidents go up or go down ??=0A=C2-=0AJ=0A=C2-=0A
Enjoy the weekend !=C2- I =0A=C2-=0AJan=0A=C2-=0APS : will not be fit
ting a fuse on that=0Awire =C2- But I will look very very closel
y at how it is run ..=0A=C2-=0A=0A______________________________
__=0A =0AFrom:owner-aeroelectric-list-server@matronics.com=0A[mailto:owner-
aeroelectric-list-server@matronics.com] On Behalf Of Jeff Luckey=0ASent: 0
7 December 2013 01:38=0ATo: aeroelectric-list@matronics.com=0ASubject: Re:
AeroElectric-List:=0AUnprotected Feeder in Z Drawings=0A=C2-=0ABob, =0A
=0AOk, I don't disagree w/ any of the points made but let's play the Devil'
s=0AAdvocate/Worst Case Scenario game.=0A=0ASeveral years ago in Germany Pi
lot A was flying an Extra 300 and he looses his=0Apen.=C2- He finishes hi
s flight but forgets to recover the pen.=C2- A few=0Adays later Pilot B t
akes the plane through several aerobatic maneuvers which=0Adislodge the pen
from where it was hiding and wedge it between the buss on the=0Aback of th
e breakers and the airframe causing a fault to ground.=C2- Smoke in=0Athe
cockpit, panic, denial, etc but eventually Pilot B does the right thing an
d=0Akills the master, lands plane, changes underwear, semi-happy ending.=C2
- Good=0ANews: engine not electrically-dependent so engine keeps running:
)=0A=0ABad News: The plane requires some serious re-wire because the feeder
melted=0Aother wires in the loom.=C2- Sure, no one died but I certainly
don't want to=0Abe Pilot B!=C2- If that feeder had been fused there would
have been no smoke=0Aand no damage to wiring.=0A=C2-=0AThe=0Apoint is th
at simply installing the feeder w/ care & craftsmanship may not=0Abe enough
.=C2- No matter how well that feeder was installed, it would have=0Amade
no difference in this scenario.=C2- Unforeseen circumstances could make
=0Afor a bad day for your electrical system.=C2- It may be impossible to
foresee=0Aall possible bad scenarios so we want the design of the system to
be as fault=0Atolerant as possible.=0A=C2-=0APerhaps=0Aputting a fuse in
the feed line may be a "belt & suspenders"=0Aapproach but I still don't se
e a real down side and, like I mentioned earlier,=0AI sure don't want to be
Pilot B.=0A=C2-=0ABTW Bob (and all) I certainly enjoy being able to=0Aex
plore & discuss these issues in cordial & intelligent ways - whether=0Aor n
ot there's a right or wrong answer, I always learn something.=0A=C2-=0A-J
eff=0A=C2-=0A=0A________________________________=0A =0AFrom:"Robert L.=0A
Nuckolls, III" <nuckolls.bob@aeroelectric.com>=0ATo: aeroelectric-list@matr
onics.com =0ASent: Friday, December 6, 2013=0A10:29 AM=0ASubject: Re: AeroE
lectric-List:=0AUnprotected Feeder in Z Drawings=0A=0A--> AeroElectric-List
message posted by: "Robert L. Nuckolls, III"=0A<nuckolls.bob@aeroelectric.
com>=0A=0A=0A> =0A> That particular wire between battery feeders and distri
bution busses has=0Aexisted in perhaps a quarter million production aircraf
t over the past 80+=0Ayears and to my knowledge, has never been fitted with
such protection.=0A> =0A> I find that fascinating...=0A> =0A> In my relati
vely simple mind I consider adding a fuse to the feeder=0A> in question to
have little or no down side and potentially huge=0A> upside - preventing an
in-flight fire. (not a fan of in-flight fires)=0A=0A=C2- Consider the co
nsequences of opening that fuse=0A=C2- (or any other event causing that p
athway to open)=0A=C2- in a TC aircraft. You loose EVERYTHING on the pane
l.=0A=C2- I.e. single point of failure for all accessories.=0A=0A=C2- Y
eah but . . . if the fuse opens, then there was=0A=C2- something 'wrong'.
=0A=0A=C2- Yes, but what?=C2- The FEMA process calls for hypothesizing
=0A=C2- every kind of event that can open the fuse and either (1)=0A=C2
- crafting a plan-b or (2) suppressing the risk.=0A=0A=0A> So the downsid
e is that there could be some innocuous event=0A> that I am unaware of whic
h pops the proposed big fuse=0A> unnecessarily.=C2- (sounds a little ridi
culous, but carry on...)=0A> I can't think of anything like that but I'm no
t a genius so I=0A> thought I'd throw it out to The List to see if its coll
ective=0A> wisdom knows about something I may have overlooked.=0A=0A=C2-
We have a huge data base from which to conduct that=0A=C2- assessment not
the least of which are big bunches of=0A=C2- airplanes smaller bunches o
f qualification studies=0A=C2- and relatively tiny bunches of incidences
that bent=0A=C2- aluminum and maybe even broke bones.=0A=0A=C2- The NTS
B narrative on aircraft accidents is accessible=0A=C2- here . . .=0A=0Aht
tp://tinyurl.com/pqcdj4h=0A=0A=C2- Do a random search of FINAL REPORTS wi
th your senses=0A=C2- attuned to causation with roots in human failings
=0A=C2- (either in operation, maintenance or design) and those=0A=C2- w
hich have causation in some physical failure=0A=C2- mechanism.=0A=0A=C2
- Instances that speak to any electrical will fall into=0A=C2- the seco
nd category for causation and will be a=0A=C2- minuscule portion of the w
hole . . . and=0A=C2- of those, faulting of a wire to ground is even=0A
=C2- smaller.=0A=0A=C2- In 40 years of flying, 1000+ hrs as pilot and
=0A=C2- probably another 2000 as passenger/observer, I've=0A=C2- observ
ed only two incidences of a popped breaker in=0A=C2- flight. NEITHER of t
hose cases had root cause in a=0A=C2- wire faulted to ground - the fault
needed to open=0A=C2- your proposed fuse.=0A=0A=C2- The foundation for
moving circuit protection off=0A=C2- the panel and reverting back to fuse
s is predicated=0A=C2- on similar experiences by thousands of other pilot
s.=0A=C2- Experiences suggesting that dedicating dollars, panel=0A=C2-
space, weight and fabrication time to a breaker-panel=0A=C2- is not a goo
d return on investment.=0A=0A=C2- Bottom line is that you're many, many t
imes more=0A=C2- likely to have a bad day in the cockpit for reasons=0A
=C2- far removed from a hard ground fault on your 6AWG=0A=C2- bus feede
r . . . and THAT because you didn't conduct=0A=C2- due diligence in its i
nstallation.=0A=0A=C2- Same thing applies to torque on your prop bolts,
=0A=C2- replacing a tire that's flopping cordage, taking=0A=C2- an extr
a close look at forecasts during icing season,=0A=C2- and a host of thing
s we do that go to reducing=0A=C2- risk.=0A=0A=C2- In the case of the b
us feeder, the risks are not=0A=C2- so much to the wire as to the thing t
he wire touches.=0A=0A=C2- Case in point:=C2- C90 on short final experi
ences disconnect=0A=C2- of elevator cables. Pilot uses trim commands and
power to=0A=C2- execute go-around, assesses the condition and successfull
y=0A=C2- lands the airplane with rudder, trim and power.=0A=0A=C2- Pull
ing up floorboards in the cockpit revealed a 40A=0A=C2- protected feeder
to the windshield de-ice inverter=0A=C2- had been mis-positioned against
the elevator control=0A=C2- cable during a maintenance operation. Over wh
at had to=0A=C2- be many hours of operation, motion of the cable wore=0A
=C2- through the insulation bringing the cable into contact=0A=C2- with
the hot wire. The arcing and sparking was of=0A=C2- insufficient intensi
ty to come to attention of crew=0A=C2- in spite of the fact that it was g
oing on virtually=0A=C2- under their feet.=0A=0A=C2- The copper wire wa
s barely damaged. The breaker never=0A=C2- popped while the elevator cabl
e eventually eroded through=0A=C2- and parted. Compare=C2- thermal prop
erties of copper versus=0A=C2- steel . . . this explains why the best ste
el safes have=0A=C2- intermediate layers of copper in their construction.
It's=0A=C2- EASY to burn through steel . . . next to impossible on coppe
r.=0A=0A=C2- This narrative explains the high order probability that=0A
=C2- even if you DID get your 6AWG feeder faulted to=0A=C2- ground, it'
s most likely to be a soft fault that=0A=C2- burns a hole in your airplan
e while doing little=0A=C2- damage to the wire . . . and certainly far sh
ort of=0A=C2- getting it to smoke and/or open a fuse/breaker.=0A=0A=C2-
Adding 'protection' to this pathway doubles the=0A=C2- number of joints
in the pathway and adds nothing=0A=C2- demonstrable in terms of fault res
ponse . . . which=0A=C2- is why the spam-can builders don't do it either.
=0A=0A=0A=0A=C2- Bob . . . =0Ahttp://www.matronics.com/Navigator?AeroElec
tric-Lista=0Ahref="http://forums.matronics.com/"=0Atarget="_blank">http
://forums.mat====================
=0A=0A=0A=0A=0A=0A=C2-=0A=C2-=0Awww.aeroelectric.com=0Awww.buildersbook
s.com=0Awww.homebuilthelp.com=0Awww.mypilotstore.com=0Awww.mrrace.com=0Ahtt
p://www.matronics.com/contribution=0Ahttp://www.matronics.com/Navigator?Aer
=======
Message 8
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| Subject: | Unprotected Feeder in Z Drawings |
Jeff,
:-)
Of course I rather have a crash in a car that has seat belts (as I always
wear them ....)
My point is that we add technical things ... to 'protect us' ... We could
be equally safe if we took responsibility and drove in such a way that we
did not have accidents - or at least had a lot less ..
Jan
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Jeff
Luckey
Sent: 07 December 2013 21:22
Subject: Re: AeroElectric-List: Unprotected Feeder in Z Drawings
Jan,
I'm not sure if you are being serious in this quote (perhaps you were being
facetious?):
The general thought of car safety is to add more things .. seat belts -
airbags - crumble zones etc etc.. list goes on and on ...
The net results is that we tend to drive faster .. We have more accidents ..
maybe less people would die .. but then compared to what ?
If you are suggesting that technology has not made cars safer, that would be
an inaccurate assertion. The advances in motor vehicle safety that you cite
have increased safety tremendously. See:
http://www-fars.nhtsa.dot.gov/Main/index.aspx
Accident rates have plummeted over the past 20 years despite large increases
in the number of vehicles. Automotive safety is fantastic example of making
things safer by applying technology.
...
_____
From: jan <jan@claver.demon.co.uk>
Sent: Saturday, December 7, 2013 3:22 AM
Subject: RE: AeroElectric-List: Unprotected Feeder in Z Drawings
Hi Jeff,
Interesting story. My take on this is simply a question of 'risk
management'. Lets say that ALL planes that do not have this 'extra fuse' now
suddenly get this 'extra fuse' .. do you think the risk is higher that
something goes wrong with the fuse .. the extra connectors to fit the fuse
.. how the fuse is fitted .. how it is potentially fitted incorrectly etc...
IF .. the only case of 'something bad happened because this wire is not
fused' is the incident that you mention below .. Well ... what do you think
is more likely to happen ....
Something wrong will all the 1000 of planes that now have 'one more part
that can go wrong' i.e. the extra fuse ... or a pen or something else
lodging against the bus and shorting to ground ?
On YOUR plane ... how easy is it for anything to actually lodge in the same
place ? Suggest looking at best way to prevent something to lodge and short
.. than to add something that has never been seen a 'required' before ....
I agree that there are very few things that are absolutely right or
absolutely wrong .. (apart from when at school ;-) ...then everything was
always very black and white ..
The more you can 'remove from the plane' the less you have that can go wrong
... what you are 'left with' ...well .. you just need to analyze the risk
and what happens when it fail .. can you reduce the risk ... without adding
another risk ..
The following is not related to aircrafts .. but I like to use it to make
people thing about risk .. and how to reduce accidents .... I have no idea
if it would work .. but you could argue the case ..
The general thought of car safety is to add more things .. seat belts -
airbags - crumble zones etc etc.. list goes on and on ...
The net results is that we tend to drive faster .. We have more accidents ..
maybe less people would die .. but then compared to what ?
Here is my idea for the ultimate car safety device .. You remove seat belts
and you make it a legal requirement that ALL steering wheels must have a 6"
spike mounted in the centre .. pointing straight at your chest .. (and NO ..
you can not wear a bullet proof west :-) ..)
Now you know ... if you do not drive very carefully, no hard braking etc...
... you are not going to last very long are you ? Looking at that 6" spike
at the steering wheel.
Sure some people will die ..and some people who are driving very carefully
will be hit by someone who does not ... But will the OVERALL number of
accidents go up or go down ??
:-)
Enjoy the weekend ! I
Jan
PS : will not be fitting a fuse on that wire ... But I will look very very
closely at how it is run .....
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Jeff
Luckey
Sent: 07 December 2013 01:38
Subject: Re: AeroElectric-List: Unprotected Feeder in Z Drawings
Bob,
Ok, I don't disagree w/ any of the points made but let's play the Devil's
Advocate/Worst Case Scenario game.
Several years ago in Germany Pilot A was flying an Extra 300 and he looses
his pen. He finishes his flight but forgets to recover the pen. A few days
later Pilot B takes the plane through several aerobatic maneuvers which
dislodge the pen from where it was hiding and wedge it between the buss on
the back of the breakers and the airframe causing a fault to ground. Smoke
in the cockpit, panic, denial, etc but eventually Pilot B does the right
thing and kills the master, lands plane, changes underwear, semi-happy
ending. Good News: engine not electrically-dependent so engine keeps
running:)
Bad News: The plane requires some serious re-wire because the feeder melted
other wires in the loom. Sure, no one died but I certainly don't want to be
Pilot B! If that feeder had been fused there would have been no smoke and
no damage to wiring.
The point is that simply installing the feeder w/ care & craftsmanship may
not be enough. No matter how well that feeder was installed, it would have
made no difference in this scenario. Unforeseen circumstances could make
for a bad day for your electrical system. It may be impossible to foresee
all possible bad scenarios so we want the design of the system to be as
fault tolerant as possible.
Perhaps putting a fuse in the feed line may be a "belt & suspenders"
approach but I still don't see a real down side and, like I mentioned
earlier, I sure don't want to be Pilot B.
BTW Bob (and all) I certainly enjoy being able to explore & discuss these
issues in cordial & intelligent ways - whether or not there's a right or
wrong answer, I always learn something.
-Jeff
_____
From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
Sent: Friday, December 6, 2013 10:29 AM
Subject: Re: AeroElectric-List: Unprotected Feeder in Z Drawings
<nuckolls.bob@aeroelectric.com <mailto:nuckolls.bob@aeroelectric.com> >
>
> That particular wire between battery feeders and distribution busses has
existed in perhaps a quarter million production aircraft over the past 80+
years and to my knowledge, has never been fitted with such protection.
>
> I find that fascinating...
>
> In my relatively simple mind I consider adding a fuse to the feeder
> in question to have little or no down side and potentially huge
> upside - preventing an in-flight fire. (not a fan of in-flight fires)
Consider the consequences of opening that fuse
(or any other event causing that pathway to open)
in a TC aircraft. You loose EVERYTHING on the panel.
I.e. single point of failure for all accessories.
Yeah but . . . if the fuse opens, then there was
something 'wrong'.
Yes, but what? The FEMA process calls for hypothesizing
every kind of event that can open the fuse and either (1)
crafting a plan-b or (2) suppressing the risk.
> So the downside is that there could be some innocuous event
> that I am unaware of which pops the proposed big fuse
> unnecessarily. (sounds a little ridiculous, but carry on...)
> I can't think of anything like that but I'm not a genius so I
> thought I'd throw it out to The List to see if its collective
> wisdom knows about something I may have overlooked.
We have a huge data base from which to conduct that
assessment not the least of which are big bunches of
airplanes smaller bunches of qualification studies
and relatively tiny bunches of incidences that bent
aluminum and maybe even broke bones.
The NTSB narrative on aircraft accidents is accessible
here . . .
http://tinyurl.com/pqcdj4h
Do a random search of FINAL REPORTS with your senses
attuned to causation with roots in human failings
(either in operation, maintenance or design) and those
which have causation in some physical failure
mechanism.
Instances that speak to any electrical will fall into
the second category for causation and will be a
minuscule portion of the whole . . . and
of those, faulting of a wire to ground is even
smaller.
In 40 years of flying, 1000+ hrs as pilot and
probably another 2000 as passenger/observer, I've
observed only two incidences of a popped breaker in
flight. NEITHER of those cases had root cause in a
wire faulted to ground - the fault needed to open
your proposed fuse.
The foundation for moving circuit protection off
the panel and reverting back to fuses is predicated
on similar experiences by thousands of other pilots.
Experiences suggesting that dedicating dollars, panel
space, weight and fabrication time to a breaker-panel
is not a good return on investment.
Bottom line is that you're many, many times more
likely to have a bad day in the cockpit for reasons
far removed from a hard ground fault on your 6AWG
bus feeder . . . and THAT because you didn't conduct
due diligence in its installation.
Same thing applies to torque on your prop bolts,
replacing a tire that's flopping cordage, taking
an extra close look at forecasts during icing season,
and a host of things we do that go to reducing
risk.
In the case of the bus feeder, the risks are not
so much to the wire as to the thing the wire touches.
Case in point: C90 on short final experiences disconnect
of elevator cables. Pilot uses trim commands and power to
execute go-around, assesses the condition and successfully
lands the airplane with rudder, trim and power.
Pulling up floorboards in the cockpit revealed a 40A
protected feeder to the windshield de-ice inverter
had been mis-positioned against the elevator control
cable during a maintenance operation. Over what had to
be many hours of operation, motion of the cable wore
through the insulation bringing the cable into contact
with the hot wire. The arcing and sparking was of
insufficient intensity to come to attention of crew
in spite of the fact that it was going on virtually
under their feet.
The copper wire was barely damaged. The breaker never
popped while the elevator cable eventually eroded through
and parted. Compare thermal properties of copper versus
steel . . . this explains why the best steel safes have
intermediate layers of copper in their construction. It's
EASY to burn through steel . . . next to impossible on copper.
This narrative explains the high order probability that
even if you DID get your 6AWG feeder faulted to
ground, it's most likely to be a soft fault that
burns a hole in your airplane while doing little
damage to the wire . . . and certainly far short of
getting it to smoke and/or open a fuse/breaker.
Adding 'protection' to this pathway doubles the
number of joints in the pathway and adds nothing
demonstrable in terms of fault response . . . which
is why the spam-can builders don't do it either.
Bob . . .
http://www.matronics.com/Navigator?AeroElectric-Lista
href="http://forums.matronics.com/"
target="_blank">http://forums.mat===================
www.aeroelectric.com
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iv%3e%20%20%3c/div%3e%0d%0a%3cpre%3e%3cb%3e%3cfont%20size=2%20color=000000>
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-- Please Support Your Lists This Month --
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(And Get Some AWESOME FREE Gifts!)
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November is the Annual List Fund Raiser. Click on
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by:
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c/font%3e%3c/div%3e%3c/div%3e%3cbr%3e%3cbr%3e%3c/div%3e%20%3c/div%3e%20%3c/d
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c/font%3e%3c/div%3e%3c/div%3e%3cbr%3e%3cbr%3e%3c/div%3e%20%3c/div%3e%20%3c/d
iv%3e%20%20%3c/div%3e%0d%0a%3cpre%3e%3cb%3e%3cfont%20size=2%20color=000000>
* AeroElectric www.aeroelectric.com <http://www.aeroelectric.com>
<http://www.buildersbooks.com>
<http://www.matronics.com/contribution>
<http://www.matronics.com/Navigator?AeroElectric-List>
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<div class=Section1>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
lang=EN-GB
style='font-size:12.0pt'>Jeff,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
lang=EN-GB
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face=Wingdings><span lang=EN-GB
style='font-size:12.0pt;font-family:Wingdings'>J</span></font><span
lang=EN-GB><o:p></o:p></span></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
lang=EN-GB
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
lang=EN-GB
style='font-size:12.0pt'>Of course I rather have a crash in a car
that has seat
belts (as I always wear them ....) <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
lang=EN-GB
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
lang=EN-GB
style='font-size:12.0pt'>My point is that we add technical things
... to ‘protect
us’ ... We could be equally safe if we took responsibility and
drove in such a
way that we did not have accidents – or at least had a lot less
.. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
lang=EN-GB
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
lang=EN-GB
style='font-size:12.0pt'>Jan<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span
style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<div class=MsoNormal align=center style='text-align:center'><font
size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span
style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] <b><span
style='font-weight:bold'>On Behalf Of </span></b><st1:PersonName
w:st="on">Jeff
Luckey</st1:PersonName><br>
<b><span style='font-weight:bold'>Sent:</span></b> 07 December 2013
21:22<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName
w:st="on">aeroelectric-list@matronics.com</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re:
AeroElectric-List:
Unprotected Feeder in Z Drawings</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'>Jan,<o:p></o:p
></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 color=black face=Tahoma><span
style='font-size:
12.0pt;font-family:Tahoma;color:black'><o:p> </o:p></span></font></
p>
</div>
<div>
<p class=MsoNormal><font size=3 color=black face=Tahoma><span
style='font-size:
12.0pt;font-family:Tahoma;color:black'>I'm not sure if you are being
serious in
this quote (perhaps you were being
facetious?):<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><span
class=yui372791386432583796150><font size=2 color=navy
face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>The general
thought of
car safety is to add more things .. seat belts – airbags –
crumble zones etc
etc.. list goes on and on …</span></font></span><font
color=black face=Tahoma><span
style='font-family:Tahoma;color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><span
class=yui372791386432583796152><font size=2 color=navy
face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont></span><font
color=black face=Tahoma><span
style='font-family:Tahoma;color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><span class=yui372791386432583796154><font
size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;
color:navy'>The net results is that we tend to drive faster .. We have
more
accidents .. maybe less people would die .. but then compared to what ?
</span></font></span><font
size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;
color:navy'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'><o:p> </o
:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 color=black face=Tahoma><span
style='font-size:
12.0pt;font-family:Tahoma;color:black'>If you are suggesting that
technology
has not made cars safer, that would be an inaccurate assertion.
The
advances in motor vehicle safety that you cite have increased safety
tremendously. See: <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 color=black face=Tahoma><span
style='font-size:
12.0pt;font-family:Tahoma;color:black'><o:p> </o:p></span></font></
p>
</div>
<div>
<p class=MsoNormal><font size=3 color=black face=Tahoma><span
style='font-size:
12.0pt;font-family:Tahoma;color:black'>http://www-fars.nhtsa.dot.gov/Mai
n/index.aspx<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 color=black face=Tahoma><span
style='font-size:
12.0pt;font-family:Tahoma;color:black'><o:p> </o:p></span></font></
p>
</div>
<div>
<p class=MsoNormal><font size=3 color=black face=Tahoma><span
style='font-size:
12.0pt;font-family:Tahoma;color:black'>Accident rates have plummeted
over the
past 20 years despite large increases in the number of vehicles.
Automotive safety is fantastic example of making things safer by
applying
technology.<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'><o:p> </o
:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 color=black face=Tahoma><span
style='font-size:
12.0pt;font-family:Tahoma;color:black'>...<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 color=black face=Tahoma><span
style='font-size:
12.0pt;font-family:Tahoma;color:black'><o:p> </o:p></span></font></
p>
</div>
<div>
<div>
<div>
<div class=MsoNormal align=center
style='text-align:center;background:white'><font
size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;
color:black'>
<hr size=1 width="100%" align=center>
</span></font></div>
<p class=MsoNormal style='background:white'><b><font size=2
color=black
face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:black;
font-weight:bold'>From:</span></font></b><font size=2 color=black
face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:black'> jan
<jan@claver.demon.co.uk><br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName
w:st="on">aeroelectric-list@matronics.com</st1:PersonName>
<br>
<b><span style='font-weight:bold'>Sent:</span></b> Saturday, December
7, 2013
3:22 AM<br>
<b><span style='font-weight:bold'>Subject:</span></b> RE:
AeroElectric-List:
Unprotected Feeder in Z Drawings</span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face="Times New Roman"><span
style='font-size:12.0pt;color:black'><o:p> </o:p></span></font></
p>
<div id=yiv1045139340>
<div>
<div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>Hi
Jeff,</span></font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>Interesting
story.
My take on this is simply a question of ‘risk management’.
Lets say that ALL
planes that do not have this ‘extra fuse’ now suddenly get
this ‘extra fuse’ ..
do you think the risk is higher that something goes wrong with the fuse
.. the
extra connectors to fit the fuse .. how the fuse is fitted .. how it is
potentially fitted incorrectly etc…</span></font><font color=bla
ck><span
style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>IF .. the only
case of
‘something bad happened because this wire is not fused’ is
the incident that
you mention below .. Well … what do you think is more likely to
happen ….</span></font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>Something wrong
will all
the 1000 of planes that now have ‘one more part that can go
wrong’ i.e. the
extra fuse … or a pen or something else lodging against the
bus and
shorting to ground ?</span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>On YOUR plane
… how easy
is it for anything to actually lodge in the same place ? Suggest
looking
at best way to prevent something to lodge and short .. than to add
something
that has never been seen a ‘required’ before
….</span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>I agree that
there are
very few things that are absolutely right or absolutely wrong .. (apart
from
when at school ;-) …then everything was always very black and
white ..</span></font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>The more you
can ‘remove
from the plane’ the less you have that can go wrong … what
you are ‘left with’
…well .. you just need to analyze the risk and what happens when
it fail .. can
you reduce the risk … without adding another risk ..
</span></font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>The following
is not
related to aircrafts .. but I like to use it to make people thing about
risk ..
and how to reduce accidents …. I have no idea if it would
work .. but you
could argue the case ..</span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>The general
thought of
car safety is to add more things .. seat belts – airbags –
crumble zones etc
etc.. list goes on and on …</span></font><font
color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>The net results
is that
we tend to drive faster .. We have more accidents .. maybe less people
would
die .. but then compared to what ? </span></font><font
color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>Here is my idea
for the
ultimate car safety device .. You remove seat belts and you make it a
legal
requirement that ALL steering wheels must have a 6” spike mounted
in the centre
.. pointing straight at your chest .. (and NO .. you can not wear a
bullet
proof west </span></font><font size=2 color=navy
face=Wingdings><span
style='font-size:10.0pt;font-family:Wingdings;color:navy'>J</span></fo
nt><font
size=2 color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;
color:navy'> ..)</span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>Now you know
… if you do
not drive very carefully, no hard braking etc… … you are
not going to last very
long are you ? Looking at that 6” spike at the steering
wheel.</span></font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>Sure some
people will die
..and some people who are driving very carefully will be hit by
someone who
does not … But will the OVERALL number of accidents go up
or go down ??</span></font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy
face=Wingdings><span
style='font-size:10.0pt;font-family:Wingdings;color:navy'>J</span></fo
nt><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>Enjoy the
weekend !
I </span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>Jan</span></font
><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'>PS : will not
be fitting
a fuse on that wire … But I will look very very closely at
how it is run
…..</span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=2
color=navy face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:navy'> </span></f
ont><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
<div>
<div class=MsoNormal align=center
style='text-align:center;background:white'><font
size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;
color:black'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<div>
<p class=MsoNormal style='background:white'><b><font size=2
color=black
face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma;color:black;
font-weight:bold'>From:</span></font></b><font size=2 color=black
face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma;color:black'>
owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] <b><span
style='font-weight:bold'>On Behalf Of </span></b><st1:PersonName
w:st="on">Jeff
Luckey</st1:PersonName><br>
<b><span style='font-weight:bold'>Sent:</span></b> 07 December 2013
01:38<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName
w:st="on">aeroelectric-list@matronics.com</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re:
AeroElectric-List:
Unprotected Feeder in Z Drawings</span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
</div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face="Times New Roman"><span
style='font-size:12.0pt;color:black'> <o:p></o:p></span></font></
p>
</div>
<div>
<div>
<p class=MsoNormal style='background:white'><st1:PersonName
w:st="on"><font
size=3 color=black face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;
color:black'>Bob</span></font></st1:PersonName><font color=black
face=Tahoma><span
style='font-family:Tahoma;color:black'>, <br>
<br>
Ok, I don't disagree w/ any of the points made but let's play the
Devil's
Advocate/Worst Case Scenario game.<br>
<br>
Several years ago in Germany Pilot A was flying an Extra 300 and he
looses his
pen. He finishes his flight but forgets to recover the pen.
A few
days later Pilot B takes the plane through several aerobatic maneuvers
which
dislodge the pen from where it was hiding and wedge it between the buss
on the
back of the breakers and the airframe causing a fault to ground.
Smoke in
the cockpit, panic, denial, etc but eventually Pilot B does the right
thing and
kills the master, lands plane, changes underwear, semi-happy
ending. Good
News: engine not electrically-dependent so engine keeps running:)<br>
<br>
Bad News: The plane requires some serious re-wire because the feeder
melted
other wires in the loom. Sure, no one died but I certainly don't
want to
be Pilot B! If that feeder had been fused there would have been
no smoke
and no damage to wiring.</span></font><font color=black><span
style='color:
black'><o:p></o:p></span></font></p>
</div>
<div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'> </span><
/font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
</div>
<div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'>The
point is that simply installing the feeder w/ care & craftsmanship
may not
be enough. No matter how well that feeder was installed, it would
have
made no difference in this scenario. Unforeseen circumstances
could make
for a bad day for your electrical system. It may be impossible to
foresee
all possible bad scenarios so we want the design of the system to be as
fault
tolerant as possible.</span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
</div>
<div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'> </span><
/font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
</div>
<div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'>Perhaps
putting a fuse in the feed line may be a "belt &
suspenders"
approach but I still don't see a real down side and, like I mentioned
earlier,
I sure don't want to be Pilot B.</span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
</div>
<div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'> </span><
/font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
</div>
<div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'>BTW
<st1:PersonName
w:st="on">Bob</st1:PersonName> (and all) I certainly enjoy being able
to
explore & discuss these issues in cordial & intelligent ways -
whether
or not there's a right or wrong answer, I always learn
something.</span></font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
</div>
<div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'> </span><
/font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
</div>
<div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'>-Jeff</span></
font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
</div>
<div>
<div>
<p class=MsoNormal style='background:white'><font size=3
color=black
face=Tahoma><span
style='font-size:12.0pt;font-family:Tahoma;color:black'> </span><
/font><font
color=black><span style='color:black'><o:p></o:p></span></font></p>
</div>
</div>
<div>
<div>
<div>
<div class=MsoNormal align=center
style='text-align:center;background:white'><font
size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;
color:black'>
<hr size=1 width="100%" align=center>
</span></font></div>
<div>
<p class=MsoNormal style='background:white'><b><font size=2
color=black
face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:black;
font-weight:bold'>From:</span></font></b><font size=2 color=black
face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:black'> "Robert
L.
Nuckolls, III" <nuckolls.bob@aeroelectric.com><br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName
w:st="on">aeroelectric-list@matronics.com</st1:PersonName>
<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, December
6, 2013
10:29 AM<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re:
AeroElectric-List:
Unprotected Feeder in Z Drawings</span></font><font color=black><span
style='color:black'><o:p></o:p></span></font></p>
</div>
</div>
<div>
<div style='margin-bottom:12.0pt'>
<p class=MsoNormal
style='margin-bottom:12.0pt;background:white'><font size=3
color=black face="Times New Roman"><span
style='font-size:12.0pt;color:black'><br>
--> AeroElectric-List message posted by: "Robert L. Nuckolls,
III"
<<a href="mailto:nuckolls.bob@aeroelectric.com" target="_blank"
ymailto="mailto:nuckolls.bob@aeroelectric.com">nuckolls.bob@aeroelectr
ic.com</a>><br>
<br>
<br>
> <br>
> That particular wire between battery feeders and distribution
busses has
existed in perhaps a quarter million production aircraft over the past
80+
years and to my knowledge, has never been fitted with such
protection.<br>
> <br>
> I find that fascinating...<br>
> <br>
> In my relatively simple mind I consider adding a fuse to the
feeder<br>
> in question to have little or no down side and potentially
huge<br>
> upside - preventing an in-flight fire. (not a fan of in-flight
fires)<br>
<br>
Consider the consequences of opening that fuse<br>
(or any other event causing that pathway to open)<br>
in a TC aircraft. You loose EVERYTHING on the panel.<br>
I.e. single point of failure for all accessories.<br>
<br>
Yeah but . . . if the fuse opens, then there was<br>
something 'wrong'.<br>
<br>
Yes, but what? The FEMA process calls for
hypothesizing<br>
every kind of event that can open the fuse and either (1)<br>
crafting a plan-b or (2) suppressing the risk.<br>
<br>
<br>
> So the downside is that there could be some innocuous event<br>
> that I am unaware of which pops the proposed big fuse<br>
> unnecessarily. (sounds a little ridiculous, but carry
on...)<br>
> I can't think of anything like that but I'm not a genius so I<br>
> thought I'd throw it out to The List to see if its collective<br>
> wisdom knows about something I may have overlooked.<br>
<br>
We have a huge data base from which to conduct that<br>
assessment not the least of which are big bunches of<br>
airplanes smaller bunches of qualification studies<br>
and relatively tiny bunches of incidences that bent<br>
aluminum and maybe even broke bones.<br>
<br>
The NTSB narrative on aircraft accidents is accessible<br>
here . . .<br>
<br>
http://tinyurl.com/pqcdj4h<br>
<br>
Do a random search of FINAL REPORTS with your senses<br>
attuned to causation with roots in human failings<br>
(either in operation, maintenance or design) and those<br>
which have causation in some physical failure<br>
mechanism.<br>
<br>
Instances that speak to any electrical will fall into<br>
the second category for causation and will be a<br>
minuscule portion of the whole . . . and<br>
of those, faulting of a wire to ground is even<br>
smaller.<br>
<br>
In 40 years of flying, 1000+ hrs as pilot and<br>
probably another 2000 as passenger/observer, I've<br>
observed only two incidences of a popped breaker in<br>
flight. NEITHER of those cases had root cause in a<br>
wire faulted to ground - the fault needed to open<br>
your proposed fuse.<br>
<br>
The foundation for moving circuit protection off<br>
the panel and reverting back to fuses is predicated<br>
on similar experiences by thousands of other pilots.<br>
Experiences suggesting that dedicating dollars, panel<br>
space, weight and fabrication time to a breaker-panel<br>
is not a good return on investment.<br>
<br>
Bottom line is that you're many, many times more<br>
likely to have a bad day in the cockpit for reasons<br>
far removed from a hard ground fault on your 6AWG<br>
bus feeder . . . and THAT because you didn't conduct<br>
due diligence in its installation.<br>
<br>
Same thing applies to torque on your prop bolts,<br>
replacing a tire that's flopping cordage, taking<br>
an extra close look at forecasts during icing season,<br>
and a host of things we do that go to reducing<br>
risk.<br>
<br>
In the case of the bus feeder, the risks are not<br>
so much to the wire as to the thing the wire touches.<br>
<br>
Case in point: C90 on short final experiences
disconnect<br>
of elevator cables. Pilot uses trim commands and power to<br>
execute go-around, assesses the condition and successfully<br>
lands the airplane with rudder, trim and power.<br>
<br>
Pulling up floorboards in the cockpit revealed a 40A<br>
protected feeder to the windshield de-ice inverter<br>
had been mis-positioned against the elevator control<br>
cable during a maintenance operation. Over what had to<br>
be many hours of operation, motion of the cable wore<br>
through the insulation bringing the cable into contact<br>
with the hot wire. The arcing and sparking was of<br>
insufficient intensity to come to attention of crew<br>
in spite of the fact that it was going on virtually<br>
under their feet.<br>
<br>
The copper wire was barely damaged. The breaker never<br>
popped while the elevator cable eventually eroded through<br>
and parted. Compare thermal properties of copper
versus<br>
steel . . . this explains why the best steel safes have<br>
intermediate layers of copper in their construction. It's<br>
EASY to burn through steel . . . next to impossible on
copper.<br>
<br>
This narrative explains the high order probability that<br>
even if you DID get your 6AWG feeder faulted to<br>
ground, it's most likely to be a soft fault that<br>
burns a hole in your airplane while doing little<br>
damage to the wire . . . and certainly far short of<br>
getting it to smoke and/or open a fuse/breaker.<br>
<br>
Adding 'protection' to this pathway doubles the<br>
number of joints in the pathway and adds nothing<br>
demonstrable in terms of fault response . . . which<br>
is why the spam-can builders don't do it either.<br>
<br>
<br>
<br>
<st1:PersonName w:st="on">Bob</st1:PersonName> . . . <br>
http://www.matronics.com/Navigator?AeroElectric-Lista
href="http://forums.matronics.com/"
target="_blank">http://forums.mat========
============<br>
<br>
<br>
<br>
<o:p></o:p></span></font></p>
</div>
</div>
</div>
</div>
</div>
<pre style='background:white'><b><font size=2 color=black
face="Courier New"><span
style='font-size:10.0pt;color:black;font-weight:bold'> </sp
an></font></b><font
color=black><span
style='color:black'><o:p></o:p></span></font></pre><pre
style='background:white'><b><font size=2 color=black
face="Courier New"><span
style='font-size:10.0pt;color:black;font-weight:bold'>
</span></font></b><font
color=black><span
style='color:black'><o:p></o:p></span></font></pre><pre
style='background:white'><b><font size=2 color=black
face="Courier New"><span
style='font-size:10.0pt;color:black;font-weight:bold'>www.aeroelectric
.com</span></font></b><font
color=black><span
style='color:black'><o:p></o:p></span></font></pre><pre
style='background:white'><b><font size=2 color=black
face="Courier New"><span
style='font-size:10.0pt;color:black;font-weight:bold'>www.buildersbook
s.com</span></font></b><font
color=black><span
style='color:black'><o:p></o:p></span></font></pre><pre
style='background:white'><b><font size=2 color=black
face="Courier New"><span
style='font-size:10.0pt;color:black;font-weight:bold'>www.homebuilthel
p.com</span></font></b><font
color=black><span
style='color:black'><o:p></o:p></span></font></pre><pre
style='background:white'><b><font size=2 color=black
face="Courier New"><span
style='font-size:10.0pt;color:black;font-weight:bold'>www.mypilotstore
.com</span></font></b><font
color=black><span
style='color:black'><o:p></o:p></span></font></pre><pre
style='background:white'><b><font size=2 color=black
face="Courier New"><span
style='font-size:10.0pt;color:black;font-weight:bold'>www.mrrace.com</
span></font></b><font
color=black><span
style='color:black'><o:p></o:p></span></font></pre><pre
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| Subject: | Re: Unprotected Feeder in Z Drawings |
Jeff,
As I see it, the website shows fatal accidents, not accidents, i.e. the row Motor
Vehicle Traffic Crashes is left vacant, whereas row Fatal Crashes is filled
in with the numbers you say decrease (18%) since 1994. If we assume that the
number of vehicles have increased since 1994, it is safe to also assume the number
of accidents have increased, but the website statistics show the number
of fatal accidents decreased. This means if the assumptions are correct, safety
features like what are stated below have indeed saved lives and possibly decreased
the severity of non-fatal injuries. I know I feel safer with modern seat
belts, air bags (the car kind, not the passenger kind), crumble zones, 4-wheel
disc brakes with ABS, etc. Perhaps better designed and maintained roads is
also a factor. I wonder how texting and looking at smartphones have affected
injuries and fatalities?
Henador Titzoff
--------------------------------------------
On Sat, 12/7/13, Jeff Luckey <jluckey@pacbell.net> wrote:
Subject: Re: AeroElectric-List: Unprotected Feeder in Z Drawings
To: "aeroelectric-list@matronics.com" <aeroelectric-list@matronics.com>
Date: Saturday, December 7, 2013, 1:22 PM
Jan,
I'm
not sure if you are being serious in this quote (perhaps you
were being facetious?):The
general thought of car safety is to
add more things .. seat belts airbags crumble zones
etc etc..
list goes on and on
The
net results is that we tend to drive
faster .. We have more accidents .. maybe less people would
die .. but then
compared to what ?
If
you are suggesting that technology has not made cars safer,
that would be an inaccurate assertion. The advances in
motor vehicle safety that you cite have increased safety
tremendously. See:
http://www-fars.nhtsa.dot.gov/Main/index.aspx
Accident
rates have plummeted over the past 20 years despite large
increases in the number of vehicles. Automotive safety
is fantastic example of making things safer by applying
technology.
...
From: jan
<jan@claver.demon.co.uk>
To:
aeroelectric-list@matronics.com
Sent:
Saturday, December 7, 2013 3:22 AM
Subject: RE:
AeroElectric-List: Unprotected Feeder in Z Drawings
Hi
Jeff,
Interesting
story. My take on this
is simply a question of risk management. Lets say that
ALL planes
that do not have this extra fuse now suddenly get this
extra
fuse .. do you think the risk is higher that something
goes wrong with
the fuse .. the extra connectors to fit the fuse .. how the
fuse is fitted ..
how it is potentially fitted incorrectly
etc
IF ..
the only case of something
bad happened because this wire is not fused is the
incident that you mention
below .. Well what do you think is more likely to happen
.
Something
wrong will all the 1000 of
planes that now have one more part that can go wrong
i.e. the
extra fuse or a pen or something else lodging
against the bus and
shorting to ground ?
On
YOUR plane how easy is it for
anything to actually lodge in the same place ? Suggest
looking at best
way to prevent something to lodge and short .. than to add
something that has
never been seen a required before
.
I
agree that there are very few things
that are absolutely right or absolutely wrong .. (apart from
when at school ;-)
then everything was always very black and white
..
The
more you can remove from the
plane the less you have that can go wrong what you
are left
with well .. you just need to analyze the risk and
what happens
when it fail .. can you reduce the risk without adding
another risk ..
The
following is not related to aircrafts
.. but I like to use it to make people thing about risk ..
and how to reduce accidents
. I have no idea if it would work .. but you could
argue the case
..
The
general thought of car safety is to
add more things .. seat belts airbags crumble zones
etc etc..
list goes on and on
The
net results is that we tend to drive
faster .. We have more accidents .. maybe less people would
die .. but then
compared to what ?
Here
is my idea for the ultimate car
safety device .. You remove seat belts and you make it a
legal requirement that
ALL steering wheels must have a 6 spike mounted in the
centre ..
pointing straight at your chest .. (and NO .. you can not
wear a bullet proof
west J
..)
Now
you know if you do not drive
very carefully, no hard braking etc you are not going
to last
very long are you ? Looking at that 6 spike at the
steering wheel.
Sure
some people will die ..and some people
who are driving very carefully will be hit by someone who
does not
But will the OVERALL number of accidents go up or go down
??
J
Enjoy
the weekend ! I
Jan
PS :
will not be fitting a fuse on that
wire But I will look very very closely at how it
is run ..
From:
owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com]
On Behalf Of
Jeff
Luckey
Sent: 07
December 2013 01:38
To:
aeroelectric-list@matronics.com
Subject: Re:
AeroElectric-List:
Unprotected Feeder in Z Drawings
Bob,
Ok, I don't disagree w/ any of the points made but
let's play the Devil's
Advocate/Worst Case Scenario game.
Several years ago in Germany Pilot A was flying an Extra 300
and he looses his
pen. He finishes his flight but forgets to recover the
pen. A few
days later Pilot B takes the plane through several aerobatic
maneuvers which
dislodge the pen from where it was hiding and wedge it
between the buss on the
back of the breakers and the airframe causing a fault to
ground. Smoke in
the cockpit, panic, denial, etc but eventually Pilot B does
the right thing and
kills the master, lands plane, changes underwear, semi-happy
ending. Good
News: engine not electrically-dependent so engine keeps
running:)
Bad News: The plane requires some serious re-wire because
the feeder melted
other wires in the loom. Sure, no one died but I
certainly don't want to
be Pilot B! If that feeder had been fused there would
have been no smoke
and no damage to wiring.
The
point is that simply installing the feeder w/ care &
craftsmanship may not
be enough. No matter how well that feeder was
installed, it would have
made no difference in this scenario. Unforeseen
circumstances could make
for a bad day for your electrical system. It may be
impossible to foresee
all possible bad scenarios so we want the design of the
system to be as fault
tolerant as possible.
Perhaps
putting a fuse in the feed line may be a "belt &
suspenders"
approach but I still don't see a real down side and,
like I mentioned earlier,
I sure don't want to be Pilot B.
BTW
Bob (and all) I certainly enjoy being able to
explore & discuss these issues in cordial &
intelligent ways - whether
or not there's a right or wrong answer, I always learn
something.
-Jeff
From:
"Robert L.
Nuckolls, III" <nuckolls.bob@aeroelectric.com>
To:
aeroelectric-list@matronics.com
Sent: Friday,
December 6, 2013
10:29 AM
Subject: Re:
AeroElectric-List:
Unprotected Feeder in Z Drawings
Nuckolls, III"
<nuckolls.bob@aeroelectric.com>
>
> That particular wire between battery feeders and
distribution busses has
existed in perhaps a quarter million production aircraft
over the past 80+
years and to my knowledge, has never been fitted with such
protection.
>
> I find that fascinating...
>
> In my relatively simple mind I consider adding a fuse
to the feeder
> in question to have little or no down side and
potentially huge
> upside - preventing an in-flight fire. (not a fan of
in-flight fires)
Consider the consequences of opening that fuse
(or any other event causing that pathway to open)
in a TC aircraft. You loose EVERYTHING on the panel.
I.e. single point of failure for all accessories.
Yeah but . . . if the fuse opens, then there was
something 'wrong'.
Yes, but what? The FEMA process calls for
hypothesizing
every kind of event that can open the fuse and either
(1)
crafting a plan-b or (2) suppressing the risk.
> So the downside is that there could be some innocuous
event
> that I am unaware of which pops the proposed big fuse
> unnecessarily. (sounds a little ridiculous, but
carry on...)
> I can't think of anything like that but I'm not
a genius so I
> thought I'd throw it out to The List to see if its
collective
> wisdom knows about something I may have overlooked.
We have a huge data base from which to conduct that
assessment not the least of which are big bunches of
airplanes smaller bunches of qualification studies
and relatively tiny bunches of incidences that bent
aluminum and maybe even broke bones.
The NTSB narrative on aircraft accidents is
accessible
here . . .
http://tinyurl.com/pqcdj4h
Do a random search of FINAL REPORTS with your senses
attuned to causation with roots in human failings
(either in operation, maintenance or design) and
those
which have causation in some physical failure
mechanism.
Instances that speak to any electrical will fall
into
the second category for causation and will be a
minuscule portion of the whole . . . and
of those, faulting of a wire to ground is even
smaller.
In 40 years of flying, 1000+ hrs as pilot and
probably another 2000 as passenger/observer,
I've
observed only two incidences of a popped breaker in
flight. NEITHER of those cases had root cause in a
wire faulted to ground - the fault needed to open
your proposed fuse.
The foundation for moving circuit protection off
the panel and reverting back to fuses is predicated
on similar experiences by thousands of other pilots.
Experiences suggesting that dedicating dollars,
panel
space, weight and fabrication time to a
breaker-panel
is not a good return on investment.
Bottom line is that you're many, many times more
likely to have a bad day in the cockpit for reasons
far removed from a hard ground fault on your 6AWG
bus feeder . . . and THAT because you didn't
conduct
due diligence in its installation.
Same thing applies to torque on your prop bolts,
replacing a tire that's flopping cordage, taking
an extra close look at forecasts during icing
season,
and a host of things we do that go to reducing
risk.
In the case of the bus feeder, the risks are not
so much to the wire as to the thing the wire
touches.
Case in point: C90 on short final experiences
disconnect
of elevator cables. Pilot uses trim commands and
power to
execute go-around, assesses the condition and
successfully
lands the airplane with rudder, trim and power.
Pulling up floorboards in the cockpit revealed a 40A
protected feeder to the windshield de-ice inverter
had been mis-positioned against the elevator control
cable during a maintenance operation. Over what had
to
be many hours of operation, motion of the cable wore
through the insulation bringing the cable into
contact
with the hot wire. The arcing and sparking was of
insufficient intensity to come to attention of crew
in spite of the fact that it was going on virtually
under their feet.
The copper wire was barely damaged. The breaker
never
popped while the elevator cable eventually eroded
through
and parted. Compare thermal properties of
copper versus
steel . . . this explains why the best steel safes
have
intermediate layers of copper in their construction.
It's
EASY to burn through steel . . . next to impossible
on copper.
This narrative explains the high order probability
that
even if you DID get your 6AWG feeder faulted to
ground, it's most likely to be a soft fault that
burns a hole in your airplane while doing little
damage to the wire . . . and certainly far short of
getting it to smoke and/or open a fuse/breaker.
Adding 'protection' to this pathway doubles
the
number of joints in the pathway and adds nothing
demonstrable in terms of fault response . . . which
is why the spam-can builders don't do it either.
Bob . . .
http://www.matronics.com/Navigator?AeroElectric-Lista
href="http://forums.matronics.com/"
target="_blank">http://forums.mat===================
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| Subject: | Re: Unprotected Feeder in Z Drawings |
There is an interesting psychological factor that I've heard called "risk co
mpensation" that applies here. For example, when football players have sligh
tly better helmets, they feel less vulnerable, and thus hit harder. The net r
esult is an increase in head trauma. It's sort of like having an airplane wi
th an emergency parachute. Would you ever find yourself more likely to take a
weather or mechanical risk if you knew, that if all else failed, you could p
ull a lever and float relatively safely to the ground? Experience shows tha
t the human brain is wired in such a way that we can easily fall into that t
rap, so it's something that all aviators should be aware of. The FAA sort of
addressed it in a very old training video about a new Bonanza owner who kee
ps saying that his plane "has enough power to take him anywhere." At the ri
sk of spoiling the ending for those who haven't seen the video, it turns out
that he was wrong.
On Dec 7, 2013, at 17:30, jan <jan@claver.demon.co.uk> wrote:
> Jeff,
>
> J
>
> Of course I rather have a crash in a car that has seat belts (as I always w
ear them ....)
>
> My point is that we add technical things ... to =98protect us
=99 ... We could be equally safe if we took responsibility and drove in such
a way that we did not have accidents =93 or at least had a lot less .
.
>
> Jan
>
>
> From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelect
ric-list-server@matronics.com] On Behalf Of Jeff Luckey
> Sent: 07 December 2013 21:22
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Unprotected Feeder in Z Drawings
>
> Jan,
>
> I'm not sure if you are being serious in this quote (perhaps you were bein
g facetious?):
> The general thought of car safety is to add more things .. seat belts
=93 airbags =93 crumble zones etc etc.. list goes on and on
>
> The net results is that we tend to drive faster .. We have more accidents .
. maybe less people would die .. but then compared to what ?
>
> If you are suggesting that technology has not made cars safer, that would b
e an inaccurate assertion. The advances in motor vehicle safety that you ci
te have increased safety tremendously. See:
>
> http://www-fars.nhtsa.dot.gov/Main/index.aspx
>
> Accident rates have plummeted over the past 20 years despite large increas
es in the number of vehicles. Automotive safety is fantastic example of mak
ing things safer by applying technology.
>
> ...
>
> From: jan <jan@claver.demon.co.uk>
> To: aeroelectric-list@matronics.com
> Sent: Saturday, December 7, 2013 3:22 AM
> Subject: RE: AeroElectric-List: Unprotected Feeder in Z Drawings
>
> Hi Jeff,
>
> Interesting story. My take on this is simply a question of =98risk m
anagement=99. Lets say that ALL planes that do not have this =98
extra fuse=99 now suddenly get this =98extra fuse=99 .. do
you think the risk is higher that something goes wrong with the fuse .. the
extra connectors to fit the fuse .. how the fuse is fitted .. how it is pot
entially fitted incorrectly etc
>
> IF .. the only case of =98something bad happened because this wire i
s not fused=99 is the incident that you mention below .. Well
what do you think is more likely to happen .
>
> Something wrong will all the 1000 of planes that now have =98one mor
e part that can go wrong=99 i.e. the extra fuse or a pen or
something else lodging against the bus and shorting to ground ?
>
> On YOUR plane how easy is it for anything to actually lodge in t
he same place ? Suggest looking at best way to prevent something to lodge a
nd short .. than to add something that has never been seen a =98requir
ed=99 before .
>
> I agree that there are very few things that are absolutely right or absolu
tely wrong .. (apart from when at school ;-) then everything was al
ways very black and white ..
>
> The more you can =98remove from the plane=99 the less you have
that can go wrong what you are =98left with=99
well .. you just need to analyze the risk and what happens when it fail .
. can you reduce the risk without adding another risk ..
>
> The following is not related to aircrafts .. but I like to use it to make p
eople thing about risk .. and how to reduce accidents . I have no i
dea if it would work .. but you could argue the case ..
>
> The general thought of car safety is to add more things .. seat belts
=93 airbags =93 crumble zones etc etc.. list goes on and on
>
> The net results is that we tend to drive faster .. We have more accidents .
. maybe less people would die .. but then compared to what ?
>
> Here is my idea for the ultimate car safety device .. You remove seat belt
s and you make it a legal requirement that ALL steering wheels must have a 6
=9D spike mounted in the centre .. pointing straight at your chest .. (
and NO .. you can not wear a bullet proof west J ..)
>
> Now you know if you do not drive very carefully, no hard braking
etc you are not going to last very long are you ? Lookin
g at that 6=9D spike at the steering wheel.
>
> Sure some people will die ..and some people who are driving very carefully
will be hit by someone who does not But will the OVERALL number o
f accidents go up or go down ??
>
> J
>
> Enjoy the weekend ! I
>
> Jan
>
> PS : will not be fitting a fuse on that wire But I will look ve
ry very closely at how it is run ..
>
> From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelect
ric-list-server@matronics.com] On Behalf Of Jeff Luckey
> Sent: 07 December 2013 01:38
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Unprotected Feeder in Z Drawings
>
> Bob,
>
> Ok, I don't disagree w/ any of the points made but let's play the Devil's A
dvocate/Worst Case Scenario game.
>
> Several years ago in Germany Pilot A was flying an Extra 300 and he looses
his pen. He finishes his flight but forgets to recover the pen. A few day
s later Pilot B takes the plane through several aerobatic maneuvers which di
slodge the pen from where it was hiding and wedge it between the buss on the
back of the breakers and the airframe causing a fault to ground. Smoke in t
he cockpit, panic, denial, etc but eventually Pilot B does the right thing a
nd kills the master, lands plane, changes underwear, semi-happy ending. Goo
d News: engine not electrically-dependent so engine keeps running:)
>
> Bad News: The plane requires some serious re-wire because the feeder melte
d other wires in the loom. Sure, no one died but I certainly don't want to b
e Pilot B! If that feeder had been fused there would have been no smoke and
no damage to wiring.
>
> The point is that simply installing the feeder w/ care & craftsmanship may
not be enough. No matter how well that feeder was installed, it would have
made no difference in this scenario. Unforeseen circumstances could make f
or a bad day for your electrical system. It may be impossible to foresee al
l possible bad scenarios so we want the design of the system to be as fault t
olerant as possible.
>
> Perhaps putting a fuse in the feed line may be a "belt & suspenders" appro
ach but I still don't see a real down side and, like I mentioned earlier, I s
ure don't want to be Pilot B.
>
> BTW Bob (and all) I certainly enjoy being able to explore & discuss these i
ssues in cordial & intelligent ways - whether or not there's a right or wron
g answer, I always learn something.
>
> -Jeff
>
> From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
> To: aeroelectric-list@matronics.com
> Sent: Friday, December 6, 2013 10:29 AM
> Subject: Re: AeroElectric-List: Unprotected Feeder in Z Drawings
>
ls.bob@aeroelectric.com>
>
>
> >
> > That particular wire between battery feeders and distribution busses has
existed in perhaps a quarter million production aircraft over the past 80+ y
ears and to my knowledge, has never been fitted with such protection.
> >
> > I find that fascinating...
> >
> > In my relatively simple mind I consider adding a fuse to the feeder
> > in question to have little or no down side and potentially huge
> > upside - preventing an in-flight fire. (not a fan of in-flight fires)
>
> Consider the consequences of opening that fuse
> (or any other event causing that pathway to open)
> in a TC aircraft. You loose EVERYTHING on the panel.
> I.e. single point of failure for all accessories.
>
> Yeah but . . . if the fuse opens, then there was
> something 'wrong'.
>
> Yes, but what? The FEMA process calls for hypothesizing
> every kind of event that can open the fuse and either (1)
> crafting a plan-b or (2) suppressing the risk.
>
>
> > So the downside is that there could be some innocuous event
> > that I am unaware of which pops the proposed big fuse
> > unnecessarily. (sounds a little ridiculous, but carry on...)
> > I can't think of anything like that but I'm not a genius so I
> > thought I'd throw it out to The List to see if its collective
> > wisdom knows about something I may have overlooked.
>
> We have a huge data base from which to conduct that
> assessment not the least of which are big bunches of
> airplanes smaller bunches of qualification studies
> and relatively tiny bunches of incidences that bent
> aluminum and maybe even broke bones.
>
> The NTSB narrative on aircraft accidents is accessible
> here . . .
>
> http://tinyurl.com/pqcdj4h
>
> Do a random search of FINAL REPORTS with your senses
> attuned to causation with roots in human failings
> (either in operation, maintenance or design) and those
> which have causation in some physical failure
> mechanism.
>
> Instances that speak to any electrical will fall into
> the second category for causation and will be a
> minuscule portion of the whole . . . and
> of those, faulting of a wire to ground is even
> smaller.
>
> In 40 years of flying, 1000+ hrs as pilot and
> probably another 2000 as passenger/observer, I've
> observed only two incidences of a popped breaker in
> flight. NEITHER of those cases had root cause in a
> wire faulted to ground - the fault needed to open
> your proposed fuse.
>
> The foundation for moving circuit protection off
> the panel and reverting back to fuses is predicated
> on similar experiences by thousands of other pilots.
> Experiences suggesting that dedicating dollars, panel
> space, weight and fabrication time to a breaker-panel
> is not a good return on investment.
>
> Bottom line is that you're many, many times more
> likely to have a bad day in the cockpit for reasons
> far removed from a hard ground fault on your 6AWG
> bus feeder . . . and THAT because you didn't conduct
> due diligence in its installation.
>
> Same thing applies to torque on your prop bolts,
> replacing a tire that's flopping cordage, taking
> an extra close look at forecasts during icing season,
> and a host of things we do that go to reducing
> risk.
>
> In the case of the bus feeder, the risks are not
> so much to the wire as to the thing the wire touches.
>
> Case in point: C90 on short final experiences disconnect
> of elevator cables. Pilot uses trim commands and power to
> execute go-around, assesses the condition and successfully
> lands the airplane with rudder, trim and power.
>
> Pulling up floorboards in the cockpit revealed a 40A
> protected feeder to the windshield de-ice inverter
> had been mis-positioned against the elevator control
> cable during a maintenance operation. Over what had to
> be many hours of operation, motion of the cable wore
> through the insulation bringing the cable into contact
> with the hot wire. The arcing and sparking was of
> insufficient intensity to come to attention of crew
> in spite of the fact that it was going on virtually
> under their feet.
>
> The copper wire was barely damaged. The breaker never
> popped while the elevator cable eventually eroded through
> and parted. Compare thermal properties of copper versus
> steel . . . this explains why the best steel safes have
> intermediate layers of copper in their construction. It's
> EASY to burn through steel . . . next to impossible on copper.
>
> This narrative explains the high order probability that
> even if you DID get your 6AWG feeder faulted to
> ground, it's most likely to be a soft fault that
> burns a hole in your airplane while doing little
> damage to the wire . . . and certainly far short of
> getting it to smoke and/or open a fuse/breaker.
>
> Adding 'protection' to this pathway doubles the
> number of joints in the pathway and adds nothing
> demonstrable in terms of fault response . . . which
> is why the spam-can builders don't do it either.
>
>
>
> Bob . . .
> http://www.matronics.com/Navigator?AeroElectric-Lista href="http://forum
s.matronics.com/" target="_blank">http://forums.mat========
===========
>
>
>
>
>
>
> www.aeroelectric.com
> www.buildersbooks.com
> www.homebuilthelp.com
> www.mypilotstore.com
> www.mrrace.com
> http://www.matronics.com/contribution
> http://www.matronics.com/Navigator?AeroElectric-List
> http://forums.matronics.com
> www.homebui= * Race Consulting http://www.matronics.com/cont-===
=====================ank" href="
http://www.matronics.com/Navigator?AeroElectric-List">http://wt;
>
> www.aeroelectric.com
> www.buildersbooks.com
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