---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 12/06/13: 5 ---------------------------------------------------------- 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 _____________________________________ Time: 05:19:18 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 _____________________________________ Time: 07:01:38 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: 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 _____________________________________ Time: 08:20:48 AM PST US From: Jeff Luckey Subject: Re: AeroElectric-List: 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" =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" =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 _____________________________________ Time: 10:30:25 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 _____________________________________ Time: 05:39:43 PM PST US From: Jeff Luckey Subject: Re: AeroElectric-List: 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 " =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" =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 ==== ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.