AeroElectric-List Digest Archive

Wed 02/27/08


Total Messages Posted: 10



Today's Message Index:
----------------------
 
     1. 08:18 AM - Re: voltage drop calulations (academic exercise) (Ron Quillin)
     2. 08:46 AM - Re: voltage drop calulations (academic exercise) (Robert L. Nuckolls, III)
     3. 10:14 AM - Re: [OT] boat wiring specificity (frazitl)
     4. 10:47 AM - Re: Noisy Turn Coordinator (John McMahon)
     5. 10:50 AM -  (Bill Lamb)
     6. 10:52 AM - TVS Failures ()
     7. 04:52 PM - Re: TVS Failures (Henador Titzoff)
     8. 05:14 PM - Re: voltage drop calulations (academic exercise) (raymondj)
     9. 06:24 PM - Question about panel light dimmers (Neil Clayton)
    10. 07:09 PM - Re: TVS Failures (Robert L. Nuckolls, III)
 
 
 


Message 1


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    Time: 08:18:22 AM PST US
    Subject: Re: voltage drop calulations (academic exercise)
    From: Ron Quillin <rjquillin@gmail.com>
    Exactly. At 23:41 2/26/2008, you wrote: >Ron, > > So, the circuit is functionally 3 resistors in series and the > middle resistor (load) can only see the voltage drop across it as > part of the total voltage drop in the entire circuit. If that's > correct than I understand.


    Message 2


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    Time: 08:46:13 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    Subject: Re: voltage drop calulations (academic exercise)
    At 01:41 AM 2/27/2008 -0600, you wrote: > >Ron, > > So, the circuit is functionally 3 resistors in series and the middle > resistor (load) can only see the voltage drop across it as part of the > total voltage drop in the entire circuit. If that's correct than I understand. > >Thanks for the explanation. >Raymond Julian >Kettle River, MN Getting closer. There are LOTS of resistors. EVERY conductor (including the aiframe), every compoent (terminals, studs, contacts) and every joint between those conductors cannot have zero resistance. We'll, we could wish for a super- conducting system but it won't happen in our lifetimes. See: http://www.aeroelectric.com/Pictures/Schematics/Voltage_Drop_Study_1.pdf http://www.aeroelectric.com/Pictures/Schematics/Voltage_Drop_Study_2.pdf These are two studies of total resistance voltage drop in exemplar situations. In both cases, the lower conductor in the figure could be a wire (composite airframe) or it could be the airframe itself. No matter how the loop is closed to keep all the electrons moving there will be some losses. Fortunately, most metalic airframes are pretty good conductors. I think a Beechjet offers something like 0.001 ohms from nose to tail. Being a "good" conductor might allow us to ignore the effects as tiny compared to the other conductors but "good" is never zero. Bob . . .


    Message 3


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    Time: 10:14:10 AM PST US
    Subject: Re: [OT] boat wiring specificity
    From: "frazitl" <fraziernv@earthlink.net>
    On 2-26 you wrote: "I've been considering switching to RG batteries in my sailboat. Batteries are used for all power and the engine isn't run very often. There is a power charger used in harbor. The lead acid batteries go 3-4 days without recharge. Would RG do better? The conventional batteries are just auto batteries - supposedly deep cycle. Would I need the same size RG batteries?" I have no experience with sail boats. but lots of motor home experience. The hot set-up for motorhomes is AGM battery technology. About twice as expensive, but no fumes, no mess, better deep cycle performance, and about twice the life. I'm about to buy new batteries for my motorhome and am going with AGMs -------- Terry Frazier RV7A Finishing Read this topic online here: http://forums.matronics.com/viewtopic.php?p=166598#166598


    Message 4


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    Time: 10:47:20 AM PST US
    From: "John McMahon" <blackoaks@gmail.com>
    Subject: Re: Noisy Turn Coordinator
    Hi 'Old Bob", I chuckle every time you get this in! I to, am a firm proponent of the turn needle! To me it is a direct reading instrument whereas every time I fly with a turn coordinator I have to convert everything its trying to tell me! Could be a function of our age.... Aviation Cadet 60B...... Old John <snip> In fact, I highly recommend that the Turn Coordinator be scrapped in > lieu of a Turn Needle, but that is another subject! > > Happy Skies, > > Old Bob <snip> > > -- John McMahon Lancair Super ES, S/N 170, N9637M (Reserved)


    Message 5


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    Time: 10:50:47 AM PST US
    From: "Bill Lamb" <n254bl@cfl.rr.com>
    Subject:
    Talk about a bored chef! Pretty amazing. ------------------------------------------------------------------------- -----


    Message 6


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    Time: 10:52:31 AM PST US
    From: <bakerocb@cox.net>
    Subject: TVS Failures
    2/27/2008 Hello Fellow Builders, The certificated airplane community has been hit with a series of TVS failures. Several different manufacturer's airplanes have been affected. Copied below is just one of the SAIB's that the FAA has issued on this subject. If your project includes TVS' you may want to further investigate -- the same TVS manufacturer seems to be involved in all failures. 'OC' Says: "The best investment we can make is the effort to gather and understand knowledge." ----------------------------------------------------- FAA Aircraft Certification Service SPECIAL AIRWORTHINESS INFORMATION BULLETIN SUBJ: Electrical Power SAIB: CE-08-12 This is information only. Recommendations aren't mandatory. Introduction This Special Airworthiness Information Bulletin (SAIB) advises you of an airworthiness concern on Cirrus Design Corporation (CDC) Models SR20 and SR22 airplanes where possible failure of a transient voltage suppressor (TVS) may result in an increase in workload for the pilot. This airworthiness action has been taken after consideration of the responses from CDC as well as airplane owners/ operators through relevant associations and type clubs, using the procedures found in the Small Airplane Directorate Airworthiness Directives Manual Supplement (Airworthiness Concern Process Guide). At this time, this airworthiness concern is not considered an unsafe condition that would warrant an airworthiness directive (AD) action under Title 14 of the Code of Federal Regulations (14 CFR part 39). Background CDC notified the Federal Aviation Administration of the failure of a TVS on a CDC Model SR22 airplane, which resulted in loss of NAV/COM1 functionality and some smoke and fumes within the cockpit. Since that time, 14 other TVS's have failed on CDC airplanes in the field. Other airplanes equipped with TVSs from the same manufacturer have recently experienced failures. Our findings thus far, show that the electronic component itself is the primary suspect for a cause of the failures. To date, no specific reason has been positively identified for the failures although several companies are working on the problem. As previously mentioned, no other functionality other than the NAV/COMM 1 has been lost on a CDC airplane. All CDC airplanes have redundancy with a NAV/COMM 2 available. Also, in all known occurrences of TVS failures, the smoke and fumes have been noted to be of short duration and not sufficient to impede the pilots visibility, or toxic such that the pilot's ability to operate the airplane is impaired. Recommendations We recommend that all CDC airplane owner/operators thoroughly read Cirrus service advisory SA 07-17, dated September 11, 2007. The service advisory provides good information on what to expect should a TVS failure occur and what actions should be taken by the pilot. For Further Information Contact Wesley Rouse, Aerospace Engineer, FAA Chicago Aircraft Certification, 2300 E. Devon, Des Plaines, IL 60018; phone: (847) 294-8113; email: wess.rouse@faa.gov


    Message 7


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    Time: 04:52:56 PM PST US
    From: Henador Titzoff <henador_titzoff@yahoo.com>
    Subject: Re: TVS Failures
    Bob, Without calling the FAA, you wouldn't happen to know how to get the failed TVS vendor's name, would you? The CDC website of course has no bad news in it. I'm sure the vendor isn't advertising it, either. Thanks, Henador Titzof ----- Original Message ---- From: "bakerocb@cox.net" <bakerocb@cox.net> Sent: Wednesday, February 27, 2008 1:49:42 PM Subject: AeroElectric-List: TVS Failures 2/27/2008 Hello Fellow Builders, The certificated airplane community has been hit with a series of TVS failures. Several different manufacturer's airplanes have been affected. Copied below is just one of the SAIB's that the FAA has issued on this subject. If your project includes TVS' you may want to further investigate -- the same TVS manufacturer seems to be involved in all failures. 'OC' Says: "The best investment we can make is the effort to gather and understand knowledge." Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs


    Message 8


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    Time: 05:14:50 PM PST US
    From: "raymondj" <raymondj@frontiernet.net>
    Subject: Re: voltage drop calulations (academic exercise)
    I got this piece of the puzzle now. Thanks! Raymond Julian Kettle River, MN "Hope for the best, but prepare for the worst." do not archive ----- Original Message ----- From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net> Sent: Wednesday, February 27, 2008 10:42 AM Subject: Re: AeroElectric-List: voltage drop calulations (academic exercise) > <nuckolls.bob@cox.net> > > At 01:41 AM 2/27/2008 -0600, you wrote: > >><raymondj@frontiernet.net> >> >>Ron, >> >> So, the circuit is functionally 3 resistors in series and the middle >> resistor (load) can only see the voltage drop across it as part of the >> total voltage drop in the entire circuit. If that's correct than I >> understand. >> >>Thanks for the explanation. >>Raymond Julian >>Kettle River, MN > > Getting closer. There are LOTS of resistors. EVERY conductor > (including the aiframe), every compoent (terminals, studs, > contacts) and every joint between those conductors cannot > have zero resistance. We'll, we could wish for a super- > conducting system but it won't happen in our lifetimes. > > See: > > http://www.aeroelectric.com/Pictures/Schematics/Voltage_Drop_Study_1.pdf > > http://www.aeroelectric.com/Pictures/Schematics/Voltage_Drop_Study_2.pdf > > These are two studies of total resistance voltage drop > in exemplar situations. In both cases, the lower > conductor in the figure could be a wire (composite > airframe) or it could be the airframe itself. No matter > how the loop is closed to keep all the electrons moving > there will be some losses. Fortunately, most metalic > airframes are pretty good conductors. I think a Beechjet > offers something like 0.001 ohms from nose to tail. > Being a "good" conductor might allow us to ignore > the effects as tiny compared to the other conductors > but "good" is never zero. > > Bob . . . > > > -- > 269.21.1/1301 - Release Date: 2/27/2008 8:35 AM > >


    Message 9


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    Time: 06:24:00 PM PST US
    From: Neil Clayton <harvey4@earthlink.net>
    Subject: Question about panel light dimmers
    The panel dimmer I selected can handle 1.5 amps. I have 9 gauges needing 0.2 amps each. So at max dimming, the dimmer is being asked to dissipate (0.2 x 9 =) 1.8 amps - a bit more than it's rated capacity. I figured that was close enough - until I realized I forgot to include the radio back light, which takes me WAY over the 1.5 amp capacity. Theory; this humble M.Eng assumed the dimmer uses a silicon-controlled rectifier that gets hotter the more it's being asked to dim (so that for zero dimming = full brightness, there's no heat being dissipated by the SCR's heat sink). But then I recalled that SCR's work by clipping the tops of the current wave - except we use 12v DC. No current curve to clip. So much for that theory! So....how does a DC dimmer work? Can I safely go over the rated capacity of my dimmer with no expectation of disaster? If a disaster were to occur, what form would it take? Many thanks to any EE who'll take a moment to set this tyro straight. Neil


    Message 10


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    Time: 07:09:02 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@cox.net>
    Subject: Re: TVS Failures
    At 04:49 PM 2/27/2008 -0800, you wrote: ><henador_titzoff@yahoo.com> > >Bob, > >Without calling the FAA, you wouldn't happen to know how to get the failed >TVS vendor's name, would you? The CDC website of course has no bad news >in it. I'm sure the vendor isn't advertising it, either. > >Thanks, >Henador Titzof It's just a guess at this stage of the game but I'll bet that the "problem" has more to do with how the devices were incorporated into the system along with sizes selected than it has to do with quality issues for the manufacturer of the devices. These are legacy products now . . . i.e. 20+ years old. The manufacturer has made millions of these things for industrial and consumer applications and is now probably lamenting the fact that some "kind soul" included a part of their manufacture on the BOM of a T/C aircraft. I won't endeavor to sell to T/C aviation and it has nothing to do with my willingness or ability to deliver product that meets the data sheets. It's cases like this where a hand full of jelly-bean parts are named participants in a "official investigation". NOBODY wins in these things, even if the TVS manufacturer is found blameless. I'll see if I can find out more details. I'm involved in some development programs for the OEM and have some friendly contacts. In the mean time, don't get excited about purging your airframe of "bad parts" until we know the physics of the matter. Oh yeah, I'll mention in passing that my drawings seldom if ever show a TVS as part of ship's wiring. These things belong inside an appliance designed and tested to meed DO-160 cert levels. Once the appliances are pronounced golden, there's little if any need for the wire-slingers to add them to the system. Bob . . .




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