---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 02/28/04: 9 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 11:01 AM - Re: Battery Dumps (Robert L. Nuckolls, III) 2. 12:17 PM - Re: Battery dumps (Robert L. Nuckolls, III) 3. 12:22 PM - Re: Figure Z-14 and Battery-Dump (Robert L. Nuckolls, III) 4. 03:52 PM - loadmeters (Tom Barter) 5. 06:51 PM - Help with Diagnosis (Matt Jurotich) 6. 07:12 PM - Weird LED fuse behavior (John Slade) 7. 09:04 PM - Fw: Transponder arial location (Rick Fogerson) 8. 10:04 PM - Re: Re: Battery dumps (Paul Messinger) 9. 11:13 PM - ?B lead to contactor or to battery? (Troy Scott) ________________________________ Message 1 _____________________________________ Time: 11:01:16 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: RE: Battery Dumps --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 04:39 PM 2/27/2004 -0500, you wrote: >--> AeroElectric-List message posted by: "Rogers, Bob J." > >I plan to have an internally regulated 80-amp alternator (from a Mazda RX-7) >as my primary electrical energy source, with a second 35-amp permanent >magnet internally regulated alternator as a back up source of electricity. >I will have only one battery. > >I need to be able to test the back-up alternator before I fly, which >involves turning at least one alternator off while the engine is running (or >switching from one alternator to the other). What is the correct procedure >to insure that I do not accidentally destroy an alternator or any other >electrical component of my system? The PM alternator is not subject to the phenomenon of battery-dump spiking. If you have alternator loadmeter shunts in the output of both alternators, they'll allow you to monitor individual alternator behavior during preflight. A low voltage warning light is your primary first notification of a tired or broken alternator and will suffice for preflight checks of dual alternators. Start the engine and turn the PM alternator on first. Observe that you have output current. If loadmeters are not installed, observe that your low voltage warning light goes out when the alternator comes on. Turn the PM alternator off and the main alternator on. Loadmeter should show output and the low voltage light should stay off. There's no operational need for turning the main alternator off again until time to park the airplane. At that time system loads should be minimal, the battery charged and the engine is at idle rpm. Battery dumps of damaging proportions don't happen under these conditions. By the way, I've been making some effort to re-label the phenomenon under discussion "battery dump" as opposed to "load dump". In aviation, "load dump" speaks clearly to the phenomenon excited by relieving the SYSTEM of a heavy load like hydraulic pump, windshield heater, etc. We EXPECT to see system voltage perturbations but in the general sense, "load dump" is from a system perspective wherein a battery is a component of stabilizing influences. Not trying to be obtuse . . . if I use the phrase "load dump" during conversation with my associates in spam-can-land, the image that pops into their thoughts does not describe what we're talking about here. The more precise and less familiar term "battery dump" allows me to answer their questioning response with a description brings understanding about a condition that is seldom (if ever) considered. Bob . . . ________________________________ Message 2 _____________________________________ Time: 12:17:54 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: Battery dumps --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" At 01:21 PM 2/27/2004 -0800, you wrote: >--> AeroElectric-List message posted by: "Paul Messinger" > >---- Original Message ----- >From: "Robert L. Nuckolls, III" >To: >Subject: Re: AeroElectric-List: Re: Load Dumps > > > > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > > > > The big question is how the alternator's built in regulator behaves. > > If the regulator can open the field circuit before voltages get > > so high that the regulator itself is damaged, then everything > > comes to rest in an orderly manner. Depending on response time > > of the REGULATOR, the TVS has to grunt 50A or so of current for > > DURATION OF RESPONSE TIME . . . this is how George's TVS got > > launched into orbit. > > > > Response time can be a huge variable from one make of regulator > > to the next. I'm hoping that we can deduce enough information > > from the testing to modify recommendations for implementing > > Z-24 with some degree of comfort. If not (and the pilot > > really feels a need to flip alternator switches on and off > > while the engine is running), then I may have to retreat > > to the original philosophy of recommending that airplanes > > fly only with externally regulated alternators. > >I do not see how there is any basic difference (with regard to LOAD DUMP)in >internally regulated VS externally regulated Alternators; The "problem" we're addressing is the fact that some alternators with built in regulators will shoot themselves between the eyes if the pilot switches them on/off in Figure Z-24 with the engine running and with the alternator carrying some significant load. This generates something akin to the automotive "load dump" except that effects are limited to the alternator itself. Both styles of alternator can be goaded into producing a battery-dump surge of output voltage, but for everything except Z-24 wiring this has been a rare event and very low on the list of concerns. Many more radios have been smoked for lack of ov protection than for any other reason. Experience indicates (and DO-160 infers) that once this dragon is adequately chained down, probability of letting lots of smoke out of your radios is very low. >Either way the TVS current is limited to a few ms and can be tolerated by >the proper TVS. however the TVS may allow a few ms of relatively HV to >appear on the main buss that can exceed the equipment ratings. Only if the equipment is not designed to live in the real world of airplanes (or any other vehicle with a DC power generation system). >Mostly agree on Z-24, however, protection from pilot is only part of the >concern. I really do not like the use of procedures to prevent equipment >damage. Throwing the incorrect switch should never cause damage! It's not a procedure . . . it's a rational/natural mode of operating the airplane. One should not apply rapid full travel of flight controls above certain published airspeeds . . . okay as far as procedures go but I've never had occasion or desire to exercise it. By the same token, I cannot recall a single time I felt a need to cycle alternator and/or battery switches for anything other than troubleshooting on the ground or in the normal course of turning things on during preflight and turning things off before I park the airplane. Even then the alternator always goes off first and does NOT have an internal regulator. You can take ANY certified single with the infamous split rocker master switch and punch the alternator and battery off simultaneously by hitting both sides of the switch. This simultaneously disconnects the battery AND the alternator field . . . the mechanically linked nature of the split-rocker COMBINED with the fact that all spam-cans have externally regulated alternators makes this action a non- event with respect to battery dump. >I am addressing a different case. First, not everyone has your progressive >switches; Can't help it if the reasoning behind the use of progressive master switches is misunderstood or ignored. The split rocker was crafted to address these issues 45 years ago . . . and aside from the fact that it mounts in a square cornered hole and looks nothing like the other switches in the panel, there's nothing "wrong" with the split rocker. It's made by Carling and has the same guts behind the panel as the 2-10 toggle switch. The spirit and intent of this switch has stood the test of time quite well even if the switch itself has been root cause of many unnecessary replacements for alternators and regulators in spam-cans. The Z-figures have shown either simultaneous or progressive disconnection of alternator/battery since day-one. If someone chooses to wire their airplane like a Bonanza, well . . . > and you do not seem to address contactor failure. (however >unlikely its not zero). Contactor failure, particularly contactor failure while the battery presents a substantial portion of the total alternator load is very rare. > The importance of your progressive switch as the key >to your above statement should be included. >Failure of one device should never cause additional failures. I suggest that >a battery contactor failure should not result in a load dump where the >alternator is still connected to the main bus. Regardless of the potential >damage of the alternator regulator the main bus gets the impact of the load >dump and prtection needs to be added in my opinion. The combination of DO-160 qualification and designing electrical systems constrained to Mil-STD-704 has a pretty good track record for covering all the bases . . . including battery-dump. If one chooses to install accessories which are less robust, then there are certainly new issues to be considered. >My testing to date has shown to me that the remaining issue is the peak >voltage and duration during the TVS protected load dump VS the ability of >the equipment to tolerate that transient. Can you share a repeatable experiments for the tests and the data derived therefrom? We've been hashing this topic for several weeks now but I've yet to see hard data by which one can make rational recommendations for either part selection or places where it's a good thing to include as part of the system design. Everyone is free to stack as many "firewalls" against the extraordinary and unexpected as they wish. I try to avoid recommendations for firewalls in favor of designing the risks out (which is, in part, what DO-160 is about). I'll be pleased to have some real hammer-n-tongs data for color and size of the beast. It will be nice if there's a practical, one-part solution with sufficient stature to provide a 99% plus probability for standing off a battery dump event. It is my intention to document testing along with a rational for part selection which we'll recommend as an important inclusion to Figure Z-24. We'll add information specific to this topic at the next revision to the OV protection chapter in the 'Connection. Of course, folks are welcome to apply the technique to any other configuration as they see fit. As for as my recommendations . . . may I suggest it's hard to beat Figure Z-11 with a B&C L-40/LR-3 combination that drives accessories capable of standing off DO-160 defined stresses WITH or WITHOUT battery dump protection. This combination of B&C products has amassed something on order of a million flight hours of experience over the last 15 years. This represents a whole lot of pilots who have had very few reasons to worry their electrical systems. I'm confident that we'll be able to bring a similar level of confidence to the use of internally regulated alternators but not until the NUMBERS are known and describe in a way that anyone else can go verify/confirm as they see fit. Bob . . . ________________________________ Message 3 _____________________________________ Time: 12:22:37 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Re: Figure Z-14 and Battery-Dump --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" >Comments/Questions: I have installed a dual alt / dual bus system in my RV >per your design. Is there a failure mode which would make use of the >X-Feed switch unwise? If so, how do I identify that failure mode prior to >using the x-feed? If you have internally regulated alternators and you've wired with progressive (2-10) or simultaneous (2-3) switching of alternator/battery in the Master DC power control switches, there are no combinations of switch operation that generate a hazards to your system. Bob . . . ----------------------------------------- ( Experience and common sense cannot be ) ( replaced with policy and procedures. ) ( R. L. Nuckolls III ) ----------------------------------------- ________________________________ Message 4 _____________________________________ Time: 03:52:54 PM PST US From: "Tom Barter" Subject: AeroElectric-List: loadmeters --> AeroElectric-List message posted by: "Tom Barter" Bob, What is your current recommendation for a loadmeter? Searching the archives indicates that the loadmeter kits are no longer available. Is there another instrument available that can be modified to indicate system load rather than the minus -0 -plus ammeter? Thanks, Tom Barter Kesley, IA Avid Magnum ________________________________ Message 5 _____________________________________ Time: 06:51:48 PM PST US From: Matt Jurotich Subject: AeroElectric-List: Help with Diagnosis --> AeroElectric-List message posted by: Matt Jurotich My already flying when I bought it RV 6 A has a B&C alternator and a LR3C-14 voltage regulator. The builder used a 10 amp fuse in the Field line. Some months ago when I had a low battery, an attempt to jump the battery got a lot of sparks in the vicinity of the LR3C-14. About 3 flying hours later the fuse blew and we got home on the battery. Today the fuse blew again. We landed and replaced the fuse. Everything seemed OK during taxi and run-up, but the fuse blew again shortly after take-off. Got home on battery again. Since my home airport is in the DC ADIZ this needs to be fixed properly. Where do I start to look? A short in the field wire is the first place, what next? Thanks in advance for the help. Matthew M. Jurotich NASA/Goddard Space Flight Center JWST ISIM Systems Engineer m/c : 443 e-mail mailto: mjurotich@hst.nasa.gov phone : 301-286-5919 fax : 301-286-7021 JWST URL: ________________________________ Message 6 _____________________________________ Time: 07:12:56 PM PST US From: "John Slade" Subject: AeroElectric-List: Weird LED fuse behavior --> AeroElectric-List message posted by: "John Slade" Here's a strange one for someone.... I have those fuses with an LED that lights up when they blow. When running my engine for the first time I notice that the LED for the fuel injection computer (on the essential buss) is glowing, and that the glow changes in intensity with rpm - i.e. I can light it up more by pushing the throttle. On shut down I find that the fuse is not blown. I'm not seeing any charge on the buss from the alternator, and I'm wondering if this may have something to do with it. Perhaps the alternator solenoid is open, but I can't see how that would affect voltage or cause some sort of reverse flow effect. Any ideas anyone? John Slade Cozy IV turbo rotary - making noise ________________________________ Message 7 _____________________________________ Time: 09:04:56 PM PST US From: "Rick Fogerson" Subject: AeroElectric-List: Fw: Transponder arial location --> AeroElectric-List message posted by: "Rick Fogerson" ----- Original Message ----- From: Rick Fogerson Subject: Transponder arial location Hi Bob, I've got a xpdr arial question for you. I have installed that little 3 inch long arial with a ball (B&C) belly just aft of the firewall between the exhaust pipes. The arial would be shielded some in the forward direction by the portion of the lower cowl where cooling air exits and the exhaust pipes emerge from the engine compartment. That wasn't a problem when I was going to install the standard frp cowl but now I thinking of trying to build an aluminum cowl. How much of a problem do you think this would be? Thanks, Rick Fogerson RV3 Boise, ID ________________________________ Message 8 _____________________________________ Time: 10:04:13 PM PST US From: "Paul Messinger" Subject: Re: AeroElectric-List: Re: Battery dumps --> AeroElectric-List message posted by: "Paul Messinger" Thanks for your comments. Embedded comments Subject: AeroElectric-List: Re: Battery dumps > --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" > >I do not see how there is any basic difference (with regard to LOAD >>DUMP)in > >internally regulated VS externally regulated Alternators; > > The "problem" we're addressing is the fact that some > alternators with built in regulators will shoot themselves > between the eyes if the pilot switches them on/off in Figure > Z-24 with the engine running and with the alternator carrying > some significant load. This generates something akin to > the automotive "load dump" except that effects are > limited to the alternator itself. > > Both styles of alternator can be goaded into producing > a battery-dump surge of output voltage, but for everything > except Z-24 wiring this has been a rare event and very > low on the list of concerns. Rare is not zero however. I still maintain ANY internal or external regulator controlled alternator will produce a spike if the load is reduced suddenly removed or reduced. I do not see how the response time of the regulator is a major factor as the energy is already there and fast response regulators will only limit the duration, not the peak of the "dump". I do not agree that procedure alone is sufficent IF there is a solution that prevents or clips the spike. Also, I am not addressing alternator regulator damage but potential damage to the acft electrical systems. After spending tens of thousands on an acft and then skimping a small amount on adding an external regulator is to me mind boggling (dittos for low output strobes). > Many more radios have been smoked > for lack of ov protection than for any other reason. Experience > indicates (and DO-160 infers) that once this dragon is adequately > chained down, probability of letting lots of smoke out of your > radios is very low. I agree but many of us have older equipment that may not have the type of OV protection (per DO -160) to withstand a large "dump" where the voltage 'seems' to get well over 40 V with a simple 5kw 18v device and a 40 amp dump. I have not fully instrumented it as yet. Limiting the selection of equipment to certified to DO-160 is not affordable in many cases. I only have the materials and time to test my own alternator etc and do not have a ND internal W/WO external alternator. Thus you may get very different results. Sorry but every alternator is likely to be somewhat different. However, if you have a load bank that can handle 14V at 40 amps and use a contactor to drop the load you can see what the "dump" is. I have had no damage with the 5kw 18v device I am using in my setup but another poster has had failures perhaps only due to the test setup. I am not placing the TVS at the alternator but several feet away on the power bus distribution and as such have some series resistance external to the alternator. Nor do I have the time (or interest) to try to see if all my equipment will withstand the resulting OV on the bus. My intent is to clamp the OV at its source and or prevent the dump from happening in the first place. I think we agree that if the battery is never taken off line while being charged, there will be no dump. Other than contactor failure your designs prevent that IF fully followed. The problem is where a builder fails to see the reason for your design detail and changes it. >>s and can be tolerated by > >the proper TVS. however the TVS may allow a few ms of relatively HV to > >appear on the main buss that can exceed the equipment ratings. > > Only if the equipment is not designed to live in the real > world of airplanes (or any other vehicle with a DC power > generation system). Agree but in the real world there is a lot of low cost equipment available that some of us can afford that may not meet the real world enviroment and needs some external help. > >Mostly agree on Z-24, however, protection from pilot is only part of the > >concern. I really do not like the use of procedures to prevent equipment > >damage. Throwing the incorrect switch should never cause damage! > > It's not a procedure . . . it's a rational/natural mode of > operating the airplane. One should not apply rapid full > travel of flight controls above certain published airspeeds . . . > okay as far as procedures go but I've never had occasion or > desire to exercise it. By the same token, I cannot recall a > single time I felt a need to cycle alternator and/or battery > switches for anything other than troubleshooting on the ground > or in the normal course of turning things on during preflight > and turning things off before I park the airplane. Many pilots are not as well disciplined and its easy to hit the incorrect switch in a panic or simply by accident. So I disagree, regardless of the word used improper or accidental switch actuation should never result in damage. Guards and or locking levers prevent accidental actuation but does not prevent bad thinking by the pilot who believes that turning off the alternator with the engine running is OK. > > Even then the alternator always goes off first and does NOT have > an internal regulator. You can take ANY certified single with > the infamous split rocker master switch and punch the alternator > and battery off simultaneously by hitting both sides of the > switch. This simultaneously disconnects the battery AND the > alternator field . . . the mechanically linked nature > of the split-rocker COMBINED with the fact that all spam-cans > have externally regulated alternators makes this action a non- > event with respect to battery dump. Again disagree with ALL. I fly a friends spam can and he lost the external regulator when electrical smoke appeared in the cockpit and he hit the dual off rocker. True no avionics were damaged but the alternator regulator was fried and this was a factory supplied regulator. In the above case I believe the battery contactor slow opening time of several MS allowed the alternator to shut\down with no "dump". > >I am addressing a different case. First, not everyone has your progressive > >switches; All of us do not like toggle switches etc and while its fine to suggest you use what you have designed in its also worth considering others need to be able to provide the same safety with "normal" rockers or other styles that are simple not available in sequential design. > Can't help it if the reasoning behind the use of > progressive master switches is misunderstood or ignored. I suspect there are many who do not fully understand. Perhaps I missed it but I see no note in appendix Z (just downloaded) describing the requirement for the sequential switch. > The split rocker was crafted to address these issues > 45 years ago . . . and aside from the fact that it > mounts in a square cornered hole and looks nothing > like the other switches in the panel, there's nothing > "wrong" with the split rocker. It's made by Carling > and has the same guts behind the panel as the 2-10 > toggle switch. The spirit and intent of this switch > has stood the test of time quite well even if the > switch itself has been root cause of many unnecessary > replacements for alternators and regulators in spam-cans. > The Z-figures have shown either simultaneous or progressive > disconnection of alternator/battery since day-one. If > someone chooses to wire their airplane like a Bonanza, > well . . . > > > and you do not seem to address contactor failure. (however > >unlikely its not zero). > > Contactor failure, particularly contactor failure while the > battery presents a substantial portion of the total alternator > load is very rare. > > > >Failure of one device should never cause additional failures. I suggest that > >a battery contactor failure should not result in a load dump where the > >alternator is still connected to the main bus. Regardless of the potential > >damage of the alternator regulator the main bus gets the impact of the load > >dump and prtection needs to be added in my opinion. > > The combination of DO-160 qualification and designing electrical > systems constrained to Mil-STD-704 has a pretty good track record > for covering all the bases . . . including battery-dump. If one > chooses to install accessories which are less robust, then there > are certainly new issues to be considered. > > > >My testing to date has shown to me that the remaining issue is the peak > >voltage and duration during the TVS protected load dump VS the ability of > >the equipment to tolerate that transient. > > Can you share a repeatable experiments for the tests and the > data derived therefrom? We've been hashing this topic for > several weeks now but I've yet to see hard data by which > one can make rational recommendations for either part > selection or places where it's a good thing to include > as part of the system design. Addressed earlier. I will post what I can when I have accurate info VS a simple test setup where repeatability and accurate measurements are not made. I am just looking for rough info at present and what may work as a clamp. > Everyone is free to stack as many "firewalls" against the > extraordinary and unexpected as they wish. I try to avoid > recommendations for firewalls in favor of designing the risks > out (which is, in part, what DO-160 is about). I'll be pleased > to have some real hammer-n-tongs data for color and size of the > beast. It will be nice if there's a practical, one-part > solution with sufficient stature to provide a 99% plus > probability for standing off a battery dump event. > > I think we have such a part today. There is a 500 amp TVS designed specifically for this subject load dump (mentioned much earlier in ths thread as I recall). Not stocked, so I went to the 160 amp 5kw part that was in stock. It seems to work for me and should keep the dump event under DO-160 testing. However I do have some equipment that appears to be unable to pass DO-160 and so I am continuing to investigate. Perhaps my background in space craft is biasing my thinking. There we did what ever was possible to prevent single point failures regardless of probability based on real experience that even a 0.0001% probable event can and did happen. Perhaps you would like to know that I recommend your "book" etc to other builders and admonish them to follow the the info 100%. Or ask specific questions about any deviations (including the use of progressive switches :-) ) Paul EAA TC, FA ________________________________ Message 9 _____________________________________ Time: 11:13:00 PM PST US From: "Troy Scott" Subject: AeroElectric-List: ?B lead to contactor or to battery? --> AeroElectric-List message posted by: "Troy Scott" Gentlemen, I note that all the Z drawings show the alternator B lead connected to a contactor rather than directly to a battery or hot bus. Is this necessarily always the case? Is this done to facilitate OV protection? Is this more appropriate to internally regulated alternators that to externally regulated alternators? Regards, Troy Scott tscott1217@bellsouth.net