Today's Message Index:
----------------------
1. 05:19 AM - Re: Unprotected Feeder in Z Drawings (Robert L. Nuckolls, III)
2. 07:01 AM - Studies in the fine art of worrying (Robert L. Nuckolls, III)
3. 08:20 AM - Re: Unprotected Feeder in Z Drawings (Jeff Luckey)
4. 10:30 AM - Re: Unprotected Feeder in Z Drawings (Robert L. Nuckolls, III)
5. 05:39 PM - Re: Unprotected Feeder in Z Drawings (Jeff Luckey)
Message 1
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Subject: | Re: Unprotected Feeder in Z Drawings |
At 12:16 PM 12/5/2013, you wrote:
>Ken,
>
>I think you put your finger on it - I'm interested in analyzing the
>potential for events which are non-catastrophic & transient in
>nature that might cause the fuse to pop un-necessarily (nuisance trip).
>
>I think that's a pretty small universe and at the moment I can't
>think of an example of such an event - perhaps that's because there
>are none. I'm hoping the brain trust on this list can think of such
>an event that I may be overlooking.
Help me understand your concerns.
You have embarked on an analytical search for
transient events that might nuisance trip the
fuse. Is there not an equally useful activity
to identify events that might put the proposed
feeder at risk for burning in the first place?
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.
Are you aware of facts that argue with the notion
that hard-faults capable of raising that 6AWG wire
to hazardous temperatures do not exist outside
the realm of poor installation practice?
Bob . . .
Message 2
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Subject: | Studies in the fine art of worrying |
Just received a heads-up on this new product . . .
Someone has apparently studied the state of current
arts for joining of wires (and protecting the joint)
and found the practice lacking.
http://tinyurl.com/kz5c48h
They've even produced a video . . .
http://tinyurl.com/kmdfygt
"When there is no margin for error" says the narrator,
this product is the right choice. What is not said
is that the use of the right crimp tool produces a
gas tight joint that does not improve with the addition
of solder.
Had they offered the crimp+solder process as a hedge
against poor selection of tools or technique, this would
begin to make sense.
In this case, the crimp tool is nothing more useful
to the process than fixturing the wire and terminal
while solder is applied to finish a task that the crimp
tool missed.
The promotional materials do not cite reliability and/or
service problems that begged for this solution. Nor
does it suggest that with more understanding and
exploitation of legacy materials and processes, the
"need" for this product becomes less convincing.
Throughout the OBAM aviation forums there are examples
of advice to 'crimp and then solder' for improved
joint integrity. This company has taken that advice to
an new level . . . and perhaps fueled the fires of
new constellation worries amongst our brothers.
Without a doubt, this product offers an opportunity
for improved integrity of joints which are the outcome
of under-educated or careless craftsmanship. Perhaps the
accident chronicled here http://tinyurl.com/mwbk9qs
would not have happened had terminals/wires cited in last
paragraphs of page 3 had be crimped+soldered with this
not so revolutionary new product.
The point of this missive is to re-enforce the idea that
system reliability will be greatest when the designer/
builder possesses a degree of understanding about the
simple-ideas that make all the pieces fit and perform
with confidence. This understanding cannot be secured
from a simple review of promotional literature and data
sheets for products . . . the greatest reliability
doesn't come off the display racks in a blister-pak.
I would not discourage anyone from exploiting such
a product if their budget is not strained . . . without
a doubt, the product performs as advertised. But just
as we've discussed $high$ contactors and fuses in
bus feeders, the question to be asked and answered,
do understanding and rudimentary skills make this
unnecessary or a poor return on investment?
As a side note, in the Utopian lead-free world, what
is the melting temp for the solder? I note that they
did not use a heat-gun but a butane flame, easier
to 'point' the energy but also MUCH hotter. Most
insulations outside the aviation community are
gong to be pretty stressed at temperatures required
to flow lead-free solders which melt at about 100F
hotter than 63/37 tin-lead.
It takes a whole new skill set to apply these
terminals with results that match the demonstration
video . . .
Bob . . .
Message 3
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Subject: | Re: Unprotected Feeder in Z Drawings |
Bob,=0A=0ANot sure I would call them "concerns".- It's more like playing
what-if =0Abased upon my experience in other environments.=0A=0AIn other el
ectrical realms: marine, residential, commercial, and I =0Aworked on a few
high-end motor homes, having an un-protected =0Afeeder would be frowned upo
n (or in varying degrees of =0Adisapproval: considered negligent, unwise, "
against code", etc.)- =0AThat experience permeates my system design proce
ss. =0A=0A=0AIs there not an equally useful activity to identify events tha
t might put theproposedfeeder at risk for burning in the first place?=0A=0A
Certainly, but that doesn't mean that one should not engage =0A=0Ain explor
ing all options and possibilities.=0A=0A=0AAre you aware of facts that argu
e with the notion that hard-faults capable of raising that 6AWG wire to ha
zardous temperatures do not exist outside the realm of poor installation p
ractice?=0A=0AI am not.- But my ignorance of such information does not me
an =0A=0Athat it does not exist.=0A=0AThat particular wire between battery
feeders and distribution busses has existed in perhaps a quarter million p
roduction aircraft over the past 80+ years and to my knowledge, has never
been fitted with such protection.=0A=0AI find that fascinating...=0A=0A=0AI
n my relatively simple mind I consider adding a fuse to the feeder =0A=0Ain
question to have little or no down side and potentially huge =0A=0Aupside
- preventing an in-flight fire. (not a fan of in-flight fires)=0A=0A=0ASo t
he downside is that there could be some innocuous event =0A=0Athat I am una
ware of which pops the proposed big fuse =0A=0Aunnecessarily.- (sounds a
little ridiculous, but carry on...)=0AI can't think of anything like that b
ut I'm not a genius so I =0A=0Athought I'd throw it out to The List to see
if its collective =0A=0Awisdom knows about something I may have overlooked.
=0A=0A=0A-Jeff=0A=0A=0A________________________________=0A From: "Robert L.
Nuckolls, III" <nuckolls.bob@aeroelectric.com>=0ATo: aeroelectric-list@mat
ronics.com =0ASent: Friday, December 6, 2013 5:18 AM=0ASubject: Re: AeroEle
ctric-List: Unprotected Feeder in Z Drawings=0A =0A=0A--> AeroElectric-List
message posted by: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.co
m>=0A=0AAt 12:16 PM 12/5/2013, you wrote:=0A> Ken,=0A> =0A> I think you put
your finger on it - I'm interested in analyzing the potential for events w
hich are non-catastrophic & transient in nature that might cause the fuse t
o pop un-necessarily (nuisance trip).=0A> =0A> I think that's a pretty smal
l universe and at the moment I can't think of an example of such an event -
perhaps that's because there are none.- I'm hoping the brain trust on th
is list can think of such an event that I may be overlooking.=0A=0A- Hel
p me understand your concerns.=0A=0A- You have embarked on an analytical
search for=0A- transient events that might nuisance trip the=0A- fus
e. Is there not an equally useful activity=0A- to identify events that m
ight put the proposed=0A- feeder at risk for burning in the first place?
=0A=0A- That particular wire between battery feeders and=0A- distribu
tion busses has existed in perhaps a=0A- quarter million production airc
raft over the past=0A- 80+ years and to my knowledge, has never been fit
ted=0A- with such protection.=0A=0A- Are you aware of facts that argu
e with the notion=0A- that hard-faults capable of raising that 6AWG wire
=0A- to hazardous temperatures do not exist outside=0A- the realm of
====
Message 4
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Subject: | Re: Unprotected Feeder in Z Drawings |
>
>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 . . .
Message 5
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Subject: | Re: Unprotected Feeder in Z Drawings |
Bob, =0A=0AOk, I don't disagree w/ any of the points made but let's play th
e Devil's Advocate/Worst Case Scenario game.=0A=0ASeveral years ago in Germ
any Pilot A was flying an Extra 300 and he looses his pen.- He finishes h
is 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 breake
rs and the airframe causing a fault to ground.- Smoke in the cockpit, pan
ic, denial, etc but eventually Pilot B does the right thing and kills the m
aster, lands plane, changes underwear, semi-happy ending.- Good News: eng
ine not electrically-dependent so engine keeps running:)=0A=0ABad 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 dam
age to wiring.=0A=0A=0AThe point is that simply installing the feeder w/ ca
re & craftsmanship may not be enough.- No matter how well that feeder was
installed, it would have made no difference in this scenario.- Unforesee
n 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 desi
gn of the system to be as fault tolerant as possible.=0A=0A=0APerhaps putti
ng a fuse in the feed line may be a "belt & suspenders" approach but I stil
l don't see a real down side and, like I mentioned earlier, I sure don't wa
nt to be Pilot B.=0A=0ABTW Bob (and all) I certainly enjoy being able to ex
plore & discuss these issues in cordial & intelligent ways - whether or not
there's a right or wrong answer, I always learn something.=0A=0A-Jeff=0A
=0A=0A=0A________________________________=0A From: "Robert L. Nuckolls, III
" <nuckolls.bob@aeroelectric.com>=0ATo: aeroelectric-list@matronics.com =0A
Sent: Friday, December 6, 2013 10:29 AM=0ASubject: Re: AeroElectric-List: U
nprotected Feeder in Z Drawings=0A =0A=0A--> AeroElectric-List message post
ed by: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>=0A=0A=0A>
=0A> That particular wire between battery feeders and distribution busses h
as existed in perhaps a quarter million production aircraft over the past 8
0+ years and to my knowledge, has never been fitted with such protection.
=0A> =0A> I find that fascinating...=0A> =0A> In my relatively 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- Consider the consequences of openi
ng that fuse=0A- (or any other event causing that pathway to open)=0A-
in a TC aircraft. You loose EVERYTHING on the panel.=0A- I.e. single p
oint of failure for all accessories.=0A=0A- Yeah but . . . if the fuse o
pens, then there was=0A- something 'wrong'.=0A=0A- Yes, but what?-
The FEMA process calls for hypothesizing=0A- every kind of event that ca
n open the fuse and either (1)=0A- crafting a plan-b or (2) suppressing
the risk.=0A=0A=0A> So the downside is that there could be some innocuous e
vent=0A> that I am unaware of which pops the proposed big fuse=0A> unnecess
arily.- (sounds a little ridiculous, but carry on...)=0A> I can't think o
f anything like that but I'm not a genius so I=0A> thought I'd throw it out
to The List to see if its collective=0A> wisdom knows about something I ma
y have overlooked.=0A=0A- We have a huge data base from which to conduct
that=0A- assessment not the least of which are big bunches of=0A- ai
rplanes smaller bunches of qualification studies=0A- and relatively tiny
bunches of incidences that bent=0A- aluminum and maybe even broke bones
.=0A=0A- The NTSB narrative on aircraft accidents is accessible=0A- h
ere . . .=0A=0Ahttp://tinyurl.com/pqcdj4h=0A=0A- Do a random search of F
INAL REPORTS with your senses=0A- attuned to causation with roots in hum
an failings=0A- (either in operation, maintenance or design) and those
=0A- which have causation in some physical failure=0A- mechanism.=0A
=0A- Instances that speak to any electrical will fall into=0A- the se
cond category for causation and will be a=0A- minuscule portion of the w
hole . . . and=0A- of those, faulting of a wire to ground is even=0A-
smaller.=0A=0A- In 40 years of flying, 1000+ hrs as pilot and=0A- pr
obably another 2000 as passenger/observer, I've=0A- observed only two in
cidences of a popped breaker in=0A- flight. NEITHER of those cases had r
oot cause in a=0A- wire faulted to ground - the fault needed to open=0A
- your proposed fuse.=0A=0A- The foundation for moving circuit protec
tion off=0A- the panel and reverting back to fuses is predicated=0A-
on similar experiences by thousands of other pilots.=0A- Experiences sug
gesting that dedicating dollars, panel=0A- space, weight and fabrication
time to a breaker-panel=0A- is not a good return on investment.=0A=0A
- Bottom line is that you're many, many times more=0A- likely to have
a bad day in the cockpit for reasons=0A- far removed from a hard ground
fault on your 6AWG=0A- bus feeder . . . and THAT because you didn't con
duct=0A- due diligence in its installation.=0A=0A- Same thing applies
to torque on your prop bolts,=0A- replacing a tire that's flopping cord
age, taking=0A- an extra close look at forecasts during icing season,=0A
- and a host of things we do that go to reducing=0A- risk.=0A=0A-
In the case of the bus feeder, the risks are not=0A- so much to the wire
as to the thing the wire touches.=0A=0A- Case in point:- C90 on short
final experiences disconnect=0A- of elevator cables. Pilot uses trim co
mmands and power to=0A- execute go-around, assesses the condition and su
ccessfully=0A- lands the airplane with rudder, trim and power.=0A=0A-
Pulling up floorboards in the cockpit revealed a 40A=0A- protected feed
er to the windshield de-ice inverter=0A- had been mis-positioned against
the elevator control=0A- cable during a maintenance operation. Over wha
t had to=0A- be many hours of operation, motion of the cable wore=0A-
through the insulation bringing the cable into contact=0A- with the hot
wire. The arcing and sparking was of=0A- insufficient intensity to come
to attention of crew=0A- in spite of the fact that it was going on virt
ually=0A- under their feet.=0A=0A- The copper wire was barely damaged
. The breaker never=0A- popped while the elevator cable eventually erode
d through=0A- and parted. Compare- thermal properties of copper versus
=0A- steel . . . this explains why the best steel safes have=0A- inte
rmediate layers of copper in their construction. It's=0A- EASY to burn t
hrough steel . . . next to impossible on copper.=0A=0A- This narrative e
xplains the high order probability that=0A- even if you DID get your 6AW
G feeder faulted to=0A- ground, it's most likely to be a soft fault that
=0A- burns a hole in your airplane while doing little=0A- damage to t
he wire . . . and certainly far short of=0A- getting it to smoke and/or
open a fuse/breaker.=0A=0A- Adding 'protection' to this pathway doubles
the=0A- number of joints in the pathway and adds nothing=0A- demonstr
able in terms of fault response . . . which=0A- is why the spam-can buil
====
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