---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sun 12/04/05: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:02 AM - Re: Alternator with External Regulator? () 2. 06:06 AM - Re: OVPM Active Notification (Rodney Dunham) 3. 06:14 AM - Re: Alternator with External Regulator? (ND alternators with external regulation) () 4. 07:08 AM - Avionics Common Grounding Question (CardinalNSB@aol.com) 5. 08:07 AM - Re: Battery Bus Architecture (flyv35b) 6. 10:17 AM - Lowrance Airmap 2000c connector plug (Kellie Hand) 7. 04:51 PM - Re: Lorance Air map 2000c connector plug (James H Nelson) 8. 05:49 PM - Re: Battery Bus Architecture (Robert L. Nuckolls, III) 9. 05:51 PM - Re: Do I Need an Ammeter? (Speedy11@aol.com) 10. 05:59 PM - Re: Alternator terminals (Robert L. Nuckolls, III) 11. 06:03 PM - Re: Re: Do I Need an Ammeter? (Dave Morris \) 12. 07:21 PM - Re: Re: Do I Need an Ammeter? (BobsV35B@aol.com) ________________________________ Message 1 _____________________________________ Time: 06:02:03 AM PST US From: Subject: AeroElectric-List: Re: Alternator with External Regulator? --> AeroElectric-List message posted by: "hoping one of the early GM alternators that are externally regulated might have been found to fit in an RV" You might find a GM alternator with external regulation that will fit, but since all new alternators have internal regulators, you would be looking at late 60's, 70's (old). This was not Detroit's golden days for alternators. These old designs have poor cooling and are not designed for high speed. They also have a poor weight to output ratio. Modern alternator are much more efficient. May I suggest you get a ND alternator and modify that. Over the last 20 years alternators have made technological leaps from the early 80's, such as better coil windings (more power per pound weight/smaller size), better cooling (dual internal cooling fans) and designed for higher rotation RPM's. I would not use an alternator design older than say late 80's. There are other brands other than the NipponDenso, ND but from my research American made alternators continue to have service problems on cars with more recalls, service bulletins and service letters. Even B&C uses the ND as the basis of there line of alternators. They take the regulator out for you and it is only $410 to $685 bucks, plus a regulator ($228). Removing the regulator in a ND alternator is not trivial, but it's not hard. The internal regulation is on the low side (type-A VR) so you will need to modify the brush holder by tapping into one brush lead and grounding the other lead. Good luck. George From: "Tammy Goff" Subject: Re: Alternator with External Regulator? Bob, Thanks, I sort of came to that conclusion and will probably attempt to modify one of the regulators mentioned on the list. I go the "how too" remove the IR but was hoping one of the early GM alternators that are externally regulated might have been found to fit in an RV. Thanks for the info. I am pretty sure I can figure out how to remove the IR. George --------------------------------- Single? There's someone we'd like you to meet. ________________________________ Message 2 _____________________________________ Time: 06:06:28 AM PST US From: "Rodney Dunham" Subject: AeroElectric-List: RE: OVPM Active Notification --> AeroElectric-List message posted by: "Rodney Dunham" The OV protection module, as designed by Bob and purchased from B&C, does indeed provide active notification. It's not an "idiot light" but it's the next best thing. The 5 amp pullable circuit breaker is black with the numeral 5 imprinted in the center of the round pull tab. When the system is in normal mode the black on black (my panel) sits quietly in my peripheral vision. When the breaker trips, the white "collar" is easily visible and catches my eye. If we are exercising even minimal flight discipline and doing our routine check lists periodically during flight, the non illuminated but easily visible white breaker collar informs us that the thing has tripped. I usually look next at the volt meter which is reading lower than when the ALT is on line. So far, the only time mine trips is during engine start. For this reason I start my engine with the master in the middle, BAT only, position and add the ALT after the engine lights off but before adding strobes, radios, etc... I watch the Volt meter needle swing up to the usual indication and am consoled. Not only is my OBAM aircraft's electrical system functioning properly BUT I actually understand what it's doing and why!!! Thank you Bob Nuckolls. My wife still wants to bake you a cake :o) Rodney, Knoxville TN Rotax 912UL with built-in 20 Amp PM alternator and Ducatti igniton and VR ________________________________ Message 3 _____________________________________ Time: 06:14:32 AM PST US From: Subject: AeroElectric-List: Re: Alternator with External Regulator? (ND alternators with external regulation) --> AeroElectric-List message posted by: "B&C is the only company I'm aware of that offers the ND alternator modified for external regulator usage." This company has both internal and external voltage regulated ND alternators. The internal ones are modified with an on-board OV crow bar module. The other models are similar but the internal regulator is removed for external regulation; these come as approved certified replacements for certified factory planes. George http://plane-power.com/ --------------------------------- Single? There's someone we'd like you to meet. ________________________________ Message 4 _____________________________________ Time: 07:08:52 AM PST US From: CardinalNSB@aol.com Subject: AeroElectric-List: Avionics Common Grounding Question --> AeroElectric-List message posted by: CardinalNSB@aol.com I am working on a Cessna aluminum can. I am ready to begin installation of the avionics. Per the manufacturer's instructions (PSE), I have used shielded wire for the intercom. The shield floats at the jack end, and the jacks are insulated. At the intercom end, the shields are to be tied together. Also, all the "lo" wires are tied together. Finally, the shields and the lo's are tied together and inserted into the connector pin 1. There is .3 ohm resistance between the incoming pin 1 (containing the combined shields and lo's) and the outside of the case. There is a separate connector Z for the airframe ground, there is .3 ohm resistance between that pin and the outside of the case. There is .2 ohm between pin 1 and Z. Also, my nav com case is also grounded. Basically, since my cases are grounded, how is the best way to physically handle the grounding? I suppose it is possible to isolate the the case. Is that normally done? Any tips? Is it best to separate the airframe grounds from the other audio grounds anyway? I am considering adding a ground lug on the back of the audio panel for all the shields and lo's and tying that to pin 1. And to take all the airframe grounds to a common ground lug. Or am I misunderstanding, and should just make one big common ground for everything avionics. Or, any other advice, please. Thank you, Skip Simpson ________________________________ Message 5 _____________________________________ Time: 08:07:19 AM PST US From: "flyv35b" Subject: Re: AeroElectric-List: Battery Bus Architecture --> AeroElectric-List message posted by: "flyv35b" > If you extend the bus away from the battery, it's not a battery bus > any more . . . you'll want to add some form of min-battery contactor > and the bus becomes #2, aux, #3, etc. > > A "battery bus" is right at the battery, is always hot and feeds light > loads protected by no larger than 5A breaker or 7A fuses. If a feeder > larger than 7A is needed, then you'd be well advised to add some form > of remotely controlled disconnect for that feeder . . . right at the > bus. Bob, I just noticed your email from over a month ago and have wondered for quite awhile why a feeder from the battery bus to a pull type breaker, for instance, that feeds an E-BUS should be limited to 5A, as specified in FAR 23, or 7A as you mentioned above. What's wrong with using a 15A fuse at the battery, supplying current to a 10A Klixxon breaker and then directly to an E-BUS, as long as the wire is sized properly? It seems to me that this is simpler and there is less chance of failure than adding a contactor as you show in your schematic below. I have never heard why the 5A limitation in the FAR is based on some logical reason or was just an arbitrary value sufficient to supply most always hot circuits. Cliff A&P/IA > One example of a high-current battery bus feeder is illustrated in > http://www.aeroelectric.com/Pictures/Schematics/E-BusFatFeed.gif > where we see how one can feed an overweight e-bus with a 15A feeder > and a relay operated by the E-BUS ALTERNATE FEED switch. ________________________________ Message 6 _____________________________________ Time: 10:17:00 AM PST US From: "Kellie Hand" Subject: AeroElectric-List: Lowrance Airmap 2000c connector plug --> AeroElectric-List message posted by: "Kellie Hand" I need to make (or buy) a cable that will let me use the data line for input to my Trio EZ-Pilot wing leveler, but having trouble finding a part number or source for the 6-pin plug on the back of the 2000c gps. Anybody know the type or a source and part number for the 2000c's power/data plug connector? I'll ask Trio for help as well and post the answer when I find it, but if you have an answer, please let me know! Thanks, Chris Hand RV-6A, finishing kit stages ________________________________ Message 7 _____________________________________ Time: 04:51:23 PM PST US Subject: Re: AeroElectric-List: Lorance Air map 2000c connector plug From: James H Nelson --> AeroElectric-List message posted by: James H Nelson Chris, I had the same problem with Lorance. The end of the discussion was to use their computer hook up from the GPS (with the 12 volt auto power plug). I am using the Air map 500 and I have to pull out the #2 (signal) pin and the #5 (gnd). That way I can use it to drive my Digi Trak... They are beginning to realize they need to put on their web site how to use their GPS to drive something like an auto pilot. Jim Nelson ________________________________ Message 8 _____________________________________ Time: 05:49:31 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Battery Bus Architecture --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 08:08 AM 12/4/2005 -0800, you wrote: >--> AeroElectric-List message posted by: "flyv35b" > > > > If you extend the bus away from the battery, it's not a battery bus > > any more . . . you'll want to add some form of min-battery contactor > > and the bus becomes #2, aux, #3, etc. > > > > A "battery bus" is right at the battery, is always hot and feeds light > > loads protected by no larger than 5A breaker or 7A fuses. If a feeder > > larger than 7A is needed, then you'd be well advised to add some form > > of remotely controlled disconnect for that feeder . . . right at the > > bus. > >Bob, I just noticed your email from over a month ago and have wondered for >quite awhile why a feeder from the battery bus to a pull type breaker, for >instance, that feeds an E-BUS should be limited to 5A, as specified in FAR >23, or 7A as you mentioned above. What's wrong with using a 15A fuse at the >battery, supplying current to a 10A Klixxon breaker and then directly to an >E-BUS, as long as the wire is sized properly? It seems to me that this is >simpler and there is less chance of failure than adding a contactor as you >show in your schematic below. The goal for turning switches on the panel to OFF is to minimize the numbers and sizes for wires connected to the battery (the biggest single power source in the airplane). Toward this goal, battery contactors have always been positioned as close as practical to the battery itself. >I have never heard why the 5A limitation in the FAR is based on some logical >reason or was just an arbitrary value sufficient to supply most always hot >circuits. The 1960's certified singles with electric clocks and Hobbs meters powered from an always-hot battery had a 'battery bus' of sorts. Both of these circuits tied directly to the hot side of the battery contactor through fuses of 5A or less. When I worked at Cessna in '68, the "5A rule" was around and being fondly observed. I don't believe I've seen the "5A rule" in the FARS. In fact, I don't think I've seen it in print anywhere but I can ask around out at RAC . . . The notion behind the "5A rule" is to limit the energy that might delivered from a faulted wire that's always tied to a battery. Just between you and me a 5A breaker will drive a soft-fault with MORE than enough energy needed to light off either gasoline or kerosene. Now, a 5A fuse has an i(squared)-T constant a fraction of that for a breaker. So, I've extrapolated that perhaps one could go to a 7A fuse on an always hot feeder and still meet the spirit and intent of the 5A rule. Like most rules from bureaucratic organizations, the final version is that which upsets the least number of people on the committee. My personal airplane would have an e-bus relay like that shown in . . . http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdf/Z32K.pdf Now the size of the fuse with respect to crash safety is a moot point. When all the switches are OFF, everything is cold. I might have some always hot feeders for things like cabin light . . . on a 1A fuse. Those are my design goals . . . you can adjust yours as you see fit. Bob . . . ________________________________ Message 9 _____________________________________ Time: 05:51:34 PM PST US From: Speedy11@aol.com Subject: AeroElectric-List: Re: Do I Need an Ammeter? --> AeroElectric-List message posted by: Speedy11@aol.com Bob, As usual, your answers are extremely frustrating! You talk all around the subject but never address the subject headon. " Correct. Hall effect devices sense the effects of current flowing in the wire without actually taking energy out and wasting it. However, the term 'acceptable' is not terribly relevant in the context of this discussion. ALL methods are acceptable to someone's design goals." Let's assume that my design goal is to sense current in the wire without out taking energy out of the wire. Therefore, let's accept that sensing that current using a HE device is "acceptable" to me. " You have correctly perceived and illuminated the astute system designers task where goal is to mitigate the technician's tasks when it comes to troubleshooting in the future. Our brothers in the automotive world have done an excellent job with cars having implemented techniques and technologies rooted in ideas over 30 years old. The aviation side has not been so fortunate. Even if the system designer had ideas and skills to put them into production, the present environment for implementing new ideas stonewalls all but the most 'necessary' of new products. We had some discussion about this on the List sometime back where I wrote: -------------------------------------------- Once you're on the ground, likelihood that ammeters and voltmeters as-installed will reveal everything you need to zero in on root cause of failure is remote . . . there are not enough readings available from the rudimentary installations of such displays. (As an example: see alternator system troubleshooting guide in notes of Appendix Z) I've suggested that what ever electrical instrumentation is installed on the panel, the number and kind of measurements displayed will be far short of what's necessary to do a full-up diagnostics evaluation of the electrical system. I've further suggested that INDICATORS displaying present value of any parameter are poor warning devices. In the automotive world, one can plug diagnostic tools into a handy connector and the vehicle spills its guts. Let's consider how something similar might be implemented on an OBAM aircraft. Readers will recall many times that folks have posted calls for assistance diagnosing an electrical system problem here on the list. More often than not, remote assistance for deducing the problem requires DATA . . . voltage and/or current measurements at various points in the system give clues for a divide-and-conquer approach to isolating the problem. The task ALWAYS involves putting your multi-meter probes on various points, usually with the engine running. There are few machines more difficult to troubleshoot than an airplane. What's a mother to do? Take a peek at: http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdf/Electrical_System_Diagn ostics.pdf Here's an approach to adding a diagnostics connector to the airplane during construction. In this case, I've illustrated a couple dozen permanently installed test leads brought out to a 37-pin D-sub connector. A jack panel similar to the one shown on the last page can be plugged into the test connector. One can sit in the right (in flight if needs be) and make voltage measurements in strategic spots to aid in isolating root cause of the problem. With this type of system installed, I can deduce root cause of about any misbehavior down to a few connections, wires, and line-replaceable accessories. The example shown only speaks to electrical system. One might wish to extend test points in other systems out to the same connector. This illustrates my assertion that display of any small number of electrical system parameters on the panel will almost never be adequate for detailed diagnosis of a problem. Further, if real time indicators are also poor warning devices, then I'll suggest that carefully crafted, active notification of failures will guide you to implementation of alternative operating procedures. A few chunks of 22AWG wire and a D-sub connector will permit detailed access to the system under conditions better suited to diagnosis and repair. -------------------------------------------- Somewhere between what's installed on current production aircraft and the full-up approach I suggested above lies the answer to your question. The answers have little to do with whether you use shunted ammeters or hall effect devices, 10-digit research instruments or a $20 RadioShack multimeter. The real considerations are where to I need to peek at a voltage in order to better understand what is NOT working?" Correct! Now let's assume that I want to peek at, say, a dozen locations in the electrical system. "Design goals for your decisions should consider (1) what measurements am I most likely to have an interest in in the future and (2) how much $time$ am I willing to expend now to save perhaps more $time$ in the future? I can't recall how many times I've stood two feet behind a running prop to get an voltage reading under the cowl. Not difficult but time consuming and less than pleasant. What are you willing to do now so that you can make these kinds of measurements from the relative comfort of the copilot's seat . . . and perhaps even while airborne?" Now we're getting somewhere. Design goal is to have access to multiple readings of the electrical system - whether airborne or on the ground. And I'm willing to expend lots of $time$ now to provide said readings to save $time$ in the future. "One of the new products under development here is a 12-bit, 8-channel data acquisition system along with a graphical user interface that will be compatible with tapping data on just such a diagnostic connector. This product would allow you to plug in, start recording, go fly, duplicate symptom, land, and review the data in the comfort of your shop. The same equipment might be running in behind the seat on a long trip to capture some intermittent but irritating failure event. These are just the kinds of things I do at RAC right now. I get paid big-bux to design, fabricate, install and use operate measurement systems to fix problem airplanes . . . remote sensing systems required to mitigate design deficiencies long since removed from cars. My design goal is to offer tools for under $100 that will let you do things on your airplane that an auto mechanic can now do on your car." But, your product is not yet available and I want to wire my airplane now. Having said all that, I'll have to beg your indulgence for not having offered some simplistic response like, "Install this ammeter here, that voltmeter there and keep a wet finger ready to hold up to the wind." The real answers to your questions are not so simple and they require some thought and learning on your part. I have given it a lot of thought and I'm learning more every day. Now, if you really WANT a simple answer . . . "Do whatever you've seen done on any other airplane in the present or past and you'll be no worse off than they are . . . but no better either. I'll add that nothing I've seen done to date comes close to being a real service in the task of troubleshooting the airplane." Any and all techniques currently illustrated in the Z-figures fill the bill. Take your pick. Here's what I want. I want to know where the best locations are in an aircraft circuit to peek at the electrons so as to be able to narrow down and trouble shoot problems. There must be SOMEONE out there who can make suggestions where to sample (peek at) volts and amps so as to be able to trouble shoot the circuits. Disregard the constraints of money and time. If I want to install twelve sensors throughout my electrical system so as to be able to check readings and trouble shoot problems, where would you locate those sensors and what type sensor(s) would you use? I'm anxious to see what the run-around answer will be this time. Actually, I've probably PO'd Bob enough that he won't answer. Perhaps someone can help. Again, my design goal: ---twelve sensors in electrical system (or make it 24 if that would be better) (uh oh, better is a relative term like acceptable ... let's see ... just make it 24 sensors) ---where to locate the sensors to permit troubleshooting ---type of sensors to get the readings Anyone? Stan Sutterfield ________________________________ Message 10 ____________________________________ Time: 05:59:18 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Alternator terminals --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 01:53 PM 12/1/2005 -0700, you wrote: >--> AeroElectric-List message posted by: "Mark R. Supinski" > > > > > > > > >Thanks for the input, Bob. > > > > > >I note the comment: "If I were going to use this alternator in any > > >application..." Which gets my antenna wiggling. > > > > > >General concerns about internally regulated alternators not withstanding, > > >would you not recommend this alternator for a Z-19 based system? > > > > I have no basis to recommend it or discourage it. By "any application" > > I > > meant that if I needed to discover a way to make it work anywhere, > > I'd proceed as follows . . . > > > > Bob . . . > > > > >On further study, I wonder whether this alternator can be used in a Z-19 >style of system. As I understand it, the "F" input is used to turn the >alternator on & off -- thus if the Crowbar detects a failed regulator, the >end result is that F shuts down & the alternator is taken offline. > >Based on your analysis of the internals of my existing alternator, it seems >that there is no shutting it down short of making it stop spinning. Thus, >there is no way to prevent it eating everything on the main and engine >buses. > >The only solution I can see is to introduce (another!) contactor, and >somehow use the output of the crowbar & regulator to turn the contactor >on/off. > >Am I misreading the Z-19 diagram / alternator analysis? Nope. You're exactly right. Until Revision 11 of the Connection I had published a way to add positive control and ov protection to the internally regulated alternator. This was the oft mentioned Figure Z-24 (temporarily removed from Appendix Z) where a b-lead contactor combined with ov protection could be used satisfy those design goals. See: http://www.aeroelectric.com/temp/Z24_temp%20Model%20(1).pdf As it turns out, there are risks to the alternator wired this way IF the alternator is switched off under load. Some builders have reported killing an alternator by operating the switch from ON to OFF while the engine is running. http://www.aeroelectric.com/articles/Alternator_Failures.pdf There is risk to the S701-1 contactor if it's called upon to disconnect a runaway alternator during a real ov event. The rate of rise in alternator output may cause an arc to form across the opening contacts and severely damage the contactor. Initially, I considered these risks minimal since there was no need to operate the alternator control switch while the alternator was loaded and if I sacrificed a contactor to accomplish disconnection of the failed alternator from the system, it was no big deal. However. After at least two builders reporting killing alternators and Vans and others began to recommend against the technique, the drawing was withdrawn until modifications could be made to at least mitigate if not eliminate the risks. There is a school of thought that offers certain brands and part numbers of modern alternators as demonstrating reliability sufficient to use as-is in airplanes. Reliability (freedom from catastrophic failure) notwithstanding, the modern alternator does not fit my personal design goals for crafting a system with the same degree of hazard-free, risk-free control enjoyed by pilots of production aircraft since day-one. Further, as a writer for a broad spectrum of owner/builder/operators, I'm reluctant to promote the idea that one brand and part number of alternator should be favored over the exclusion of all others. Especially when virtually ANY automotive alternator's quirks can be accommodated with minimal $time$, weight and volume. Preliminary tests have confirmed some ideas that will offer ways to refine Z-24 such that the original goals are met (1) absolute control at any time under any conditions without risk to alternator or other system components which then gives rise to (2) ability to incorporate ov protection with any technology of choice. These ideas will not be incorporated into Z-24 for publication until they are tested and explained in the work started a few weeks ago at http://www.aeroelectric.com/articles/alternators/UA/Alternators_1.html I've about got the next four pages of this article completed. In the mean time, if you wired your alternator with the Z-24 temp version cited above and refrained from switching the alternator ON/OFF while under load with the engine running, you sidestep the risks cited and will be ready to install the "final solution" as soon as it's developed and published. I've already discovered a way to make the el-cheeso S701-1 contactor work. Bob . . . ________________________________ Message 11 ____________________________________ Time: 06:03:47 PM PST US From: "Dave Morris \"BigD\"" Subject: Re: AeroElectric-List: Re: Do I Need an Ammeter? --> AeroElectric-List message posted by: "Dave Morris \"BigD\"" He gave you a link for a schematic diagram that clearly showed a bunch of sample test points that a person would probably want to use. I found it within minutes of reading Bob's email. Dave Morris At 07:51 PM 12/4/2005, you wrote: >--> AeroElectric-List message posted by: Speedy11@aol.com > >Bob, >As usual, your answers are extremely frustrating! You talk all around the >subject but never address the subject headon. > " Correct. Hall effect devices sense the effects of current flowing > in the wire without actually taking energy out and wasting it. However, > the term 'acceptable' is not terribly relevant in the context of this > discussion. ALL methods are acceptable to someone's design goals." >Let's assume that my design goal is to sense current in the wire without out >taking energy out of the wire. Therefore, let's accept that sensing that >current using a HE device is "acceptable" to me. > > " You have correctly perceived and illuminated the astute system > designers task where goal is to mitigate the technician's tasks > when it comes to troubleshooting in the future. Our brothers in the > automotive world have done an excellent job with cars having implemented > techniques and technologies rooted in ideas over 30 years old. The > aviation side has not been so fortunate. Even if the system designer > had ideas and skills to put them into production, the present > environment for implementing new ideas stonewalls all but the most > 'necessary' of new products. > > We had some discussion about this on the List sometime back > where I wrote: > >-------------------------------------------- > > Once you're on the ground, likelihood that ammeters and > voltmeters as-installed will reveal everything you need > to zero in on root cause of failure is remote . . . there > are not enough readings available from the rudimentary installations > of such displays. > > (As an example: see alternator system troubleshooting guide > in notes of Appendix Z) > > I've suggested that what ever electrical instrumentation > is installed on the panel, the number and kind of measurements > displayed will be far short of what's necessary to do a full-up > diagnostics evaluation of the electrical system. > > I've further suggested that INDICATORS displaying present value > of any parameter are poor warning devices. > > In the automotive world, one can plug diagnostic tools into > a handy connector and the vehicle spills its guts. Let's > consider how something similar might be implemented on an > OBAM aircraft. > > Readers will recall many times that folks have posted calls > for assistance diagnosing an electrical system problem here > on the list. More often than not, remote assistance for > deducing the problem requires DATA . . . voltage and/or > current measurements at various points in the system give > clues for a divide-and-conquer approach to isolating the > problem. > > The task ALWAYS involves putting your multi-meter probes > on various points, usually with the engine running. There > are few machines more difficult to troubleshoot than an > airplane. > > What's a mother to do? Take a peek at: > >http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdf/Electrical_System_Diagn >ostics.pdf > > Here's an approach to adding a diagnostics connector to > the airplane during construction. In this case, I've > illustrated a couple dozen permanently installed test > leads brought out to a 37-pin D-sub connector. A jack > panel similar to the one shown on the last page can be > plugged into the test connector. One can sit in the right > (in flight if needs be) and make voltage measurements > in strategic spots to aid in isolating root cause of > the problem. With this type of system installed, I can > deduce root cause of about any misbehavior down to a > few connections, wires, and line-replaceable accessories. > > The example shown only speaks to electrical system. One > might wish to extend test points in other systems out > to the same connector. > > This illustrates my assertion that display of any small > number of electrical system parameters on the panel will > almost never be adequate for detailed diagnosis of a > problem. Further, if real time indicators are also poor > warning devices, then I'll suggest that carefully crafted, > active notification of failures will guide you to implementation > of alternative operating procedures. A few chunks of 22AWG > wire and a D-sub connector will permit detailed access to > the system under conditions better suited to diagnosis and > repair. >-------------------------------------------- > > Somewhere between what's installed on current production > aircraft and the full-up approach I suggested above lies > the answer to your question. The answers have little to > do with whether you use shunted ammeters or hall effect > devices, 10-digit research instruments or a $20 RadioShack > multimeter. The real considerations are where to I need > to peek at a voltage in order to better understand what > is NOT working?" > >Correct! Now let's assume that I want to peek at, say, a dozen locations in >the electrical system. > > "Design goals for your decisions should consider (1) what > measurements am I most likely to have an interest in > in the future and (2) how much $time$ am I willing to > expend now to save perhaps more $time$ in the future? > > I can't recall how many times I've stood two feet behind > a running prop to get an voltage reading under the cowl. > Not difficult but time consuming and less than pleasant. > What are you willing to do now so that you can make > these kinds of measurements from the relative comfort > of the copilot's seat . . . and perhaps even while > airborne?" > >Now we're getting somewhere. Design goal is to have access to multiple >readings of the electrical system - whether airborne or on the >ground. And I'm >willing to expend lots of $time$ now to provide said readings to save >$time$ in >the future. > > "One of the new products under development here is a > 12-bit, 8-channel data acquisition system along with > a graphical user interface that will be compatible with > tapping data on just such a diagnostic connector. This > product would allow you to plug in, start recording, > go fly, duplicate symptom, land, and review the data > in the comfort of your shop. The same equipment might > be running in behind the seat on a long trip to capture > some intermittent but irritating failure event. These > are just the kinds of things I do at RAC right now. > I get paid big-bux to design, fabricate, install and > use operate measurement systems to fix problem > airplanes . . . remote sensing systems required to > mitigate design deficiencies long since removed from > cars. > > My design goal is to offer tools for under $100 that > will let you do things on your airplane that an > auto mechanic can now do on your car." >But, your product is not yet available and I want to wire my airplane now. > > > Having said all that, I'll have to beg your indulgence > for not having offered some simplistic response like, > "Install this ammeter here, that voltmeter there and > keep a wet finger ready to hold up to the wind." The > real answers to your questions are not so simple and > they require some thought and learning on your part. >I have given it a lot of thought and I'm learning more every day. > > Now, if you really WANT a simple answer . . . > > "Do whatever you've seen done on any other airplane > in the present or past and you'll be no worse off than > they are . . . but no better either. I'll add that > nothing I've seen done to date comes close to being > a real service in the task of troubleshooting the > airplane." > > Any and all techniques currently illustrated in the > Z-figures fill the bill. Take your pick. >Here's what I want. I want to know where the best locations are in an >aircraft circuit to peek at the electrons so as to be able to narrow down and >trouble shoot problems. There must be SOMEONE out there who can make >suggestions >where to sample (peek at) volts and amps so as to be able to trouble shoot >the >circuits. Disregard the constraints of money and time. If I want to install >twelve sensors throughout my electrical system so as to be able to check >readings and trouble shoot problems, where would you locate those sensors >and what >type sensor(s) would you use? >I'm anxious to see what the run-around answer will be this time. >Actually, I've probably PO'd Bob enough that he won't answer. >Perhaps someone can help. >Again, my design goal: >---twelve sensors in electrical system (or make it 24 if that would be >better) (uh oh, better is a relative term like acceptable ... let's see >... just >make it 24 sensors) >---where to locate the sensors to permit troubleshooting >---type of sensors to get the readings >Anyone? >Stan Sutterfield > > ________________________________ Message 12 ____________________________________ Time: 07:21:32 PM PST US From: BobsV35B@aol.com Subject: Re: AeroElectric-List: Re: Do I Need an Ammeter? --> AeroElectric-List message posted by: BobsV35B@aol.com In a message dated 12/4/2005 7:53:54 P.M. Central Standard Time, Speedy11@aol.com writes: Again, my design goal: ---twelve sensors in electrical system (or make it 24 if that would be better) (uh oh, better is a relative term like acceptable ... let's see ... just make it 24 sensors) ---where to locate the sensors to permit troubleshooting ---type of sensors to get the readings Anyone? Stan Sutterfield Good Evening Stan, Please don't assume that my commenting on your question means that I know anything at all about the subject, but I was having some problems a year or so ago with an alternator control circuit on a certificated airplane. I wanted to be able to check the voltages in a manner similar to what you want to do, so this is what I did. I got the Zeftronics trouble shooting guide and looked to see what places Zeftronics suggested using for measuring voltages while checking the system. I then attached a number twenty-two wire at each of those points and led those wires to a DB nine plug which was positioned where it could be easily reached from the right seat. That way, I could use a Fluke Meter to make the checks Zeftronics wanted while the airplane was airborne. Worked just fine for me! Happy Skies, Old Bob AKA Bob Siegfried Ancient Aviator Stearman N3977A Brookeridge Air Park LL22 Downers Grove, IL 60516 630 985-8503