---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 03/03/08: 13 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:59 AM - Re: Ignition control in a dual alternator dual bus system (Mike) 2. 10:23 AM - Re: Ignition control in a dual alternator dual bus system (Ken) 3. 11:06 AM - Re: Ignition control in a dual alternator dual bus system (Hinde, Frank George (Corvallis)) 4. 04:06 PM - Re: Ignition control in a dual alternator dual bus system (William Slaughter) 5. 05:03 PM - Re: Ignition control in a dual alternator dual bus system (Deems Davis) 6. 05:19 PM - Re: Ignition control in a dual alternator dual bus system (Mike) 7. 05:42 PM - Re: Ignition control in a dual alternator dual bus system (Mike) 8. 06:18 PM - Re: Ignition control in a dual alternator dual bus system (Ken) 9. 06:57 PM - Re: Ignition control in a dual alternator dual bus system (Robert L. Nuckolls, III) 10. 08:18 PM - New EMAG and PMAG Wiring question (Don Vs) 11. 08:18 PM - Re: Low voltage indicator for LR3 (Jeff Page) 12. 08:44 PM - Re: New EMAG and PMAG Wiring question (Robert L. Nuckolls, III) 13. 09:03 PM - Re: New EMAG and PMAG Wiring question (Don Vs) ________________________________ Message 1 _____________________________________ Time: 06:59:03 AM PST US From: "Mike" Subject: RE: AeroElectric-List: Ignition control in a dual alternator dual bus system Leo, I just wanted to respond to the ignition issues you raised. First if you use an impulse coupling then you should inhibit the non-impulse mag during the start. If you go with an electronic system with variable timing then you should start with both systems on. When using an ignition system with variable timing you should run two, not one mag and one electronic system. The only exception to the mag vs. electronic is if the maximum advance on the electronic is the same at the mag. This will enable you to gain the highest horse power at the highest power setting. The idea behind having an electronic ignition system is to have variable timing and a hotter spark. The problem with one mag vs. one electronic is you give up horsepower and fuel efficiency when the timing is different. The unit that has the most advance will fire first thus starting the combustion cycle early as it compares to the other. In most cases the mag will be the first to fire at lower power setting thus eliminating a retarded timing giving you better idle and starting. At takeoff power the electronic system will in most cases advance beyond the mag causing you the loss of power gained from the mag system during that period. Something to think about, Mike -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Dr. Leo Davies Sent: Sunday, March 02, 2008 7:30 PM Subject: AeroElectric-List: Ignition control in a dual alternator dual bus system Dear List, I am currently designing the electrical system for my "all-electric" RV 10. I have been very happy with Bob's architecture for my RV6A which worked beautifully the day my alternator died in the clouds. I am looking at the Z-14 schematic which involves two batteries, two alternators and a cross feed for starting and for electron sharing in failure mode. I note that there are no switching diagrams for mags or other ignition systems on this diagram. I wondered what the implications for mag switching were in this setup. Should they just have simple switches but only turn on the impulse coupled mag for a start? If so, how serious are the implications if the non-coupled mag is accidentally enabled at startup? If I ran an electronic system on the left would you only turn this on after start and again stick with impulse coupling on the standard mag for the start. I would be pleased to hear from anyone who has used this schematic as the basis for their electrical system as to how they had handled the ignition switching. Thanks for your help. Leo Davies -- A/Prof Leo Davies, Sub-Dean, Head of Assessment, Faculty of Medicine, Edward Ford Building, University of Sydney 2006 10/2/2007 11:10 AM 10/2/2007 11:10 AM ________________________________ Message 2 _____________________________________ Time: 10:23:00 AM PST US From: Ken Subject: Re: AeroElectric-List: Ignition control in a dual alternator dual bus system I think you've misinterpreted something. I can't believe there are any electronic ignitions that advance so far as to reduce power and efficiency at any power setting when one or two of them is installed. If that were true then having two electronic ignitions would be worse than one. By all accounts one EI and one mag gives most of the benefit available from EI and is a winning combination. Ken >snip > The problem with one mag vs. > one electronic is you give up horsepower and fuel efficiency when the > timing is different. The unit that has the most advance will fire first > thus starting the combustion cycle early as it compares to the other. > In most cases the mag will be the first to fire at lower power setting > thus eliminating a retarded timing giving you better idle and starting. > At takeoff power the electronic system will in most cases advance beyond > the mag causing you the loss of power gained from the mag system during > that period. > > Something to think about, > > Mike > ________________________________ Message 3 _____________________________________ Time: 11:06:00 AM PST US From: "Hinde, Frank George (Corvallis)" Subject: RE: AeroElectric-List: Ignition control in a dual alternator dual bus system Eh?....I think you might be missing each others point... First off, there is no loss of power/efficiency with a single EI and mag...there is a reduction of fuel burned and probably a small power increase if you go from a dual mag to a single EI/mag. At low manifold pressure (high altitude) the advance will go beyond what a normal mag will do (which is fixed at 25 deg)...up to 40 deg or so of advance. This enables the thinned out mixture to make more power for a specific fuel consumption because it is lighting the fire earlier...as the thinned out mixture takes longer to burn this maximises the efficiency because max cylinder pressure is produced (hopefully) at the optimum point i.e 11 deg or so AFTER TDC It is possible to run into problems (destructive detonation is one of the worst things) if the fuel octane is too low and the advance too great... Anyway, yes if the advance is operating at 40 deg and the mag is fixed at 25 then it takes longer for the flame to spread across the cylinder which effectively retards the timing a little compared to if you have dual EI's...So for sure in terms of fuel economy adding a single EI gives the most benefit...adding a second gives a little more, but not as much as the first. Best thing to do for starting/idling is to start on the EI for smoothest running/easiest starting. Frank -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ken Sent: Monday, March 03, 2008 10:21 AM Subject: Re: AeroElectric-List: Ignition control in a dual alternator dual bus system I think you've misinterpreted something. I can't believe there are any electronic ignitions that advance so far as to reduce power and efficiency at any power setting when one or two of them is installed. If that were true then having two electronic ignitions would be worse than one. By all accounts one EI and one mag gives most of the benefit available from EI and is a winning combination. Ken >snip > The problem with one mag vs. > one electronic is you give up horsepower and fuel efficiency when the > timing is different. The unit that has the most advance will fire > first thus starting the combustion cycle early as it compares to the other. > In most cases the mag will be the first to fire at lower power setting > thus eliminating a retarded timing giving you better idle and starting. > At takeoff power the electronic system will in most cases advance > beyond the mag causing you the loss of power gained from the mag > system during that period. > > Something to think about, > > Mike > ________________________________ Message 4 _____________________________________ Time: 04:06:55 PM PST US From: "William Slaughter" Subject: RE: AeroElectric-List: Ignition control in a dual alternator dual bus system Electronic ignition systems will not cause a loss of power at takeoff power settings, as they advance the timing at lower manifold pressure cruise conditions, just like the vacuum advance mechanism did in automobile distributors of days gone by. Fixed magneto timing is set for the worst case situation - WOT. The engine will run much more efficiently with the timing advancing incrementally as the manifold pressure (and thus BMEP) declines. William -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ken Sent: Monday, March 03, 2008 12:21 PM Subject: Re: AeroElectric-List: Ignition control in a dual alternator dual bus system I think you've misinterpreted something. I can't believe there are any electronic ignitions that advance so far as to reduce power and efficiency at any power setting when one or two of them is installed. If that were true then having two electronic ignitions would be worse than one. By all accounts one EI and one mag gives most of the benefit available from EI and is a winning combination. Ken >snip > The problem with one mag vs. > one electronic is you give up horsepower and fuel efficiency when the > timing is different. The unit that has the most advance will fire first > thus starting the combustion cycle early as it compares to the other. > In most cases the mag will be the first to fire at lower power setting > thus eliminating a retarded timing giving you better idle and starting. > At takeoff power the electronic system will in most cases advance beyond > the mag causing you the loss of power gained from the mag system during > that period. > > Something to think about, > > Mike > ________________________________ Message 5 _____________________________________ Time: 05:03:39 PM PST US From: Deems Davis Subject: Re: AeroElectric-List: Ignition control in a dual alternator dual bus system Noticed there's a lot of dialog about electronic ignitions. My engine builder runs all of their engines on a fully instrumented dyno for 1 1/2 hours and records all of the data at 1 minute intervals as RPMs increase to max. Their experience is that EI's show a decrease in HP as compared to mags, in fact they will no longer build an engine with EI. Obviously they can't simulate changes in altitude with their dyno set up. And the actual results @ altitude may be different, Thie was certainly counterintuitive, but it is a data point that is worthy of consideration, and is backed up with instrumented dyno runs. I was all set to go with EI until I learned this and I've backed off to mags until the emag/pmag 6 cyl version is out and has a LOT of experience behind it. I'm not trying to start an EI/MAG war here, and I'm certainly no engine/electron expert, so don't shoot the messenger, I'm just trying to share some additional information that seems the have a basis in fact and experience. Deems Davis # 406 'Its all done....Its just not put together' http://deemsrv10.com/ William Slaughter wrote: > > Electronic ignition systems will not cause a loss of power at takeoff power > settings, as they advance the timing at lower manifold pressure cruise > conditions, just like the vacuum advance mechanism did in automobile > distributors of days gone by. Fixed magneto timing is set for the worst case > situation - WOT. The engine will run much more efficiently with the timing > advancing incrementally as the manifold pressure (and thus BMEP) declines. > > William > > -----Original Message----- > From: owner-aeroelectric-list-server@matronics.com > [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ken > Sent: Monday, March 03, 2008 12:21 PM > To: aeroelectric-list@matronics.com > Subject: Re: AeroElectric-List: Ignition control in a dual alternator dual > bus system > > > I think you've misinterpreted something. I can't believe there are any > electronic ignitions that advance so far as to reduce power and > efficiency at any power setting when one or two of them is installed. If > that were true then having two electronic ignitions would be worse than > one. By all accounts one EI and one mag gives most of the benefit > available from EI and is a winning combination. > Ken > > >snip > > The problem with one mag vs. > >> one electronic is you give up horsepower and fuel efficiency when the >> timing is different. The unit that has the most advance will fire first >> thus starting the combustion cycle early as it compares to the other. >> In most cases the mag will be the first to fire at lower power setting >> thus eliminating a retarded timing giving you better idle and starting. >> At takeoff power the electronic system will in most cases advance beyond >> the mag causing you the loss of power gained from the mag system during >> that period. >> >> Something to think about, >> >> Mike >> >> > > > ________________________________ Message 6 _____________________________________ Time: 05:19:43 PM PST US From: "Mike" Subject: RE: AeroElectric-List: Ignition control in a dual alternator dual bus system Frank, For the most part I agree. The points that I was trying to make were small. The main reason for using EI (order not important) is to improve the starting, overall HP, fuel specifics, and general smoother running throughout the range of operation. I didn't want to confuse rated operation to improved operation. The general point is, if your going to run a mix of EI and MAG why bother, your not going to see much gain unless you run both systems at the same timing point. MIke -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Hinde, Frank George (Corvallis) Sent: Monday, March 03, 2008 12:01 PM Subject: RE: AeroElectric-List: Ignition control in a dual alternator dual bus system (Corvallis)" Eh?....I think you might be missing each others point... First off, there is no loss of power/efficiency with a single EI and mag...there is a reduction of fuel burned and probably a small power increase if you go from a dual mag to a single EI/mag. At low manifold pressure (high altitude) the advance will go beyond what a normal mag will do (which is fixed at 25 deg)...up to 40 deg or so of advance. This enables the thinned out mixture to make more power for a specific fuel consumption because it is lighting the fire earlier...as the thinned out mixture takes longer to burn this maximises the efficiency because max cylinder pressure is produced (hopefully) at the optimum point i.e 11 deg or so AFTER TDC It is possible to run into problems (destructive detonation is one of the worst things) if the fuel octane is too low and the advance too great... Anyway, yes if the advance is operating at 40 deg and the mag is fixed at 25 then it takes longer for the flame to spread across the cylinder which effectively retards the timing a little compared to if you have dual EI's...So for sure in terms of fuel economy adding a single EI gives the most benefit...adding a second gives a little more, but not as much as the first. Best thing to do for starting/idling is to start on the EI for smoothest running/easiest starting. Frank -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ken Sent: Monday, March 03, 2008 10:21 AM Subject: Re: AeroElectric-List: Ignition control in a dual alternator dual bus system I think you've misinterpreted something. I can't believe there are any electronic ignitions that advance so far as to reduce power and efficiency at any power setting when one or two of them is installed. If that were true then having two electronic ignitions would be worse than one. By all accounts one EI and one mag gives most of the benefit available from EI and is a winning combination. Ken >snip > The problem with one mag vs. > one electronic is you give up horsepower and fuel efficiency when the > timing is different. The unit that has the most advance will fire > first thus starting the combustion cycle early as it compares to the other. > In most cases the mag will be the first to fire at lower power setting > thus eliminating a retarded timing giving you better idle and starting. > At takeoff power the electronic system will in most cases advance > beyond the mag causing you the loss of power gained from the mag > system during that period. > > Something to think about, > > Mike > 10/2/2007 11:10 AM 10/2/2007 11:10 AM ________________________________ Message 7 _____________________________________ Time: 05:42:44 PM PST US From: "Mike" Subject: RE: AeroElectric-List: Ignition control in a dual alternator dual bus system I can't speak for the Emag Pmag system, but we have Dyno data that shows the opposite with the Light Speed systems on 6cyl engines. Depending on power settings, data shows as much as 10% hp gain with high compression pistons. Mike -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Deems Davis Sent: Monday, March 03, 2008 5:58 PM Subject: Re: AeroElectric-List: Ignition control in a dual alternator dual bus system Noticed there's a lot of dialog about electronic ignitions. My engine builder runs all of their engines on a fully instrumented dyno for 1 1/2 hours and records all of the data at 1 minute intervals as RPMs increase to max. Their experience is that EI's show a decrease in HP as compared to mags, in fact they will no longer build an engine with EI. Obviously they can't simulate changes in altitude with their dyno set up. And the actual results @ altitude may be different, Thie was certainly counterintuitive, but it is a data point that is worthy of consideration, and is backed up with instrumented dyno runs. I was all set to go with EI until I learned this and I've backed off to mags until the emag/pmag 6 cyl version is out and has a LOT of experience behind it. I'm not trying to start an EI/MAG war here, and I'm certainly no engine/electron expert, so don't shoot the messenger, I'm just trying to share some additional information that seems the have a basis in fact and experience. Deems Davis # 406 'Its all done....Its just not put together' http://deemsrv10.com/ William Slaughter wrote: > > Electronic ignition systems will not cause a loss of power at takeoff power > settings, as they advance the timing at lower manifold pressure cruise > conditions, just like the vacuum advance mechanism did in automobile > distributors of days gone by. Fixed magneto timing is set for the worst case > situation - WOT. The engine will run much more efficiently with the timing > advancing incrementally as the manifold pressure (and thus BMEP) declines. > > William > > -----Original Message----- > From: owner-aeroelectric-list-server@matronics.com > [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ken > Sent: Monday, March 03, 2008 12:21 PM > To: aeroelectric-list@matronics.com > Subject: Re: AeroElectric-List: Ignition control in a dual alternator dual > bus system > > > I think you've misinterpreted something. I can't believe there are any > electronic ignitions that advance so far as to reduce power and > efficiency at any power setting when one or two of them is installed. If > that were true then having two electronic ignitions would be worse than > one. By all accounts one EI and one mag gives most of the benefit > available from EI and is a winning combination. > Ken > > >snip > > The problem with one mag vs. > >> one electronic is you give up horsepower and fuel efficiency when the >> timing is different. The unit that has the most advance will fire first >> thus starting the combustion cycle early as it compares to the other. >> In most cases the mag will be the first to fire at lower power setting >> thus eliminating a retarded timing giving you better idle and starting. >> At takeoff power the electronic system will in most cases advance beyond >> the mag causing you the loss of power gained from the mag system during >> that period. >> >> Something to think about, >> >> Mike >> >> > > > 10/2/2007 11:10 AM 10/2/2007 11:10 AM ________________________________ Message 8 _____________________________________ Time: 06:18:53 PM PST US From: Ken Subject: Re: AeroElectric-List: Ignition control in a dual alternator dual bus system The only explanation that I can think of is miss tuning of the advance curve either by the supplier, or by the installer. With a dyno they should be able to get it optimum. After all isn't the main advantage of EI to have the advance optimized 100% of the time. Performance automotive tuning typically involves a two dimensional map (lookup table) of manifold pressure and rpm. One map for ignition and another for fuel. That lets you set the ignition and mixture pretty much anywhere. Ken Deems Davis wrote: > > Noticed there's a lot of dialog about electronic ignitions. My engine > builder runs all of their engines on a fully instrumented dyno for 1 1/2 > hours and records all of the data at 1 minute intervals as RPMs increase > to max. Their experience is that EI's show a decrease in HP as compared > to mags, in fact they will no longer build an engine with EI. Obviously > they can't simulate changes in altitude with their dyno set up. And the > actual results @ altitude may be different, Thie was certainly > counterintuitive, but it is a data point that is worthy of > consideration, and is backed up with instrumented dyno runs. I was all > set to go with EI until I learned this and I've backed off to mags > until the emag/pmag 6 cyl version is out and has a LOT of experience > behind it. > I'm not trying to start an EI/MAG war here, and I'm certainly no > engine/electron expert, so don't shoot the messenger, I'm just trying to > share some additional information that seems the have a basis in fact > and experience. > > Deems Davis # 406 > 'Its all done....Its just not put together' > http://deemsrv10.com/ > ________________________________ Message 9 _____________________________________ Time: 06:57:30 PM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Ignition control in a dual alternator dual bus system At 06:16 PM 3/3/2008 -0700, you wrote: > >Frank, > >For the most part I agree. The points that I was trying to make were >small. The main reason for using EI (order not important) is to improve >the starting, overall HP, fuel specifics, and general smoother running >throughout the range of operation. I didn't want to confuse rated >operation to improved operation. The general point is, if your going to >run a mix of EI and MAG why bother, your not going to see much gain >unless you run both systems at the same timing point. > >MIke Most folks running a mix of technologies are hedging their bets. After all, EI is the "new kid" on the block although work by Lightspeed and ElectoAir now goes back over 20 years. The other factor is that I'm aware of no engine suppliers that will offer you a discount equal to the cost of the magneto ignition system for leaving it off the delivered engine. The last point is that the vast majority of your gains for running EI come with addition of the first system. So, consider the cost of ownership: Take off one mag and leave the other on to back up a EI system that's going to do all the work. When and if the first mag craps, put the removed one back on and get your investment back out of it. When and if the second one craps, one would hope that the first EI system is still going strong . . . so putting the second brand-new EI system on gives you one old one, one new one. You've maintained redundancy throughout the exercise and not wasted any money on hardware while enjoying the vast majority of what an EI system can deliver. Most folks I've talked to running EI had yet to see an ROI on fuel savings . . . although when it gets to $5/gallon, that may change quickly. Most were very pleased with starting performance and the ability to use automotive plugs. Bob . . . ________________________________ Message 10 ____________________________________ Time: 08:18:17 PM PST US From: "Don Vs" Subject: AeroElectric-List: New EMAG and PMAG Wiring question Bob, I just looked at the new?? fig 13-8 and I have a few questions. The Pmag wiring shown would require you to turn off the main bus to test the PMAG self power. Is this your intention? Would another method such as using the Emag method shown with the addition of a switch between the bat bus and the S700 2 10 switch also work. If so do you see any problems with this set up? Thanks. Don ________________________________ Message 11 ____________________________________ Time: 08:18:18 PM PST US From: Jeff Page Subject: AeroElectric-List: Re: Low voltage indicator for LR3 > Failure of the main alternator is not an emergency. It's > an emergency only if you have no alternatives i.e, you > have no back up engine driven power source and you haven't > the foggiest notion of how long your battery will run goodies > in the endurance mode. I can turn it into an emergency by thinking the aux alternator is maintaining the battery when I have not remembered to turn it on. > How about a voltmeter. Does one of your relatively low > power digital panel-wiggets have a voltmeter function? I will likely have a Dynon product, so yeah, it will have a low voltage alarm, but idiot lights are still useful sometimes. >> This also means there are 3 switches I could accidentally leave on >> after a flight or maintenance that would ensure a depleted battery >> before the next flight. > > Are there no electro-whizzies on the panel that stay > lit up when the endurance bus is hot? . . . and three > switches? What's going to stay on un-annunciated besides > the e-bus alternate feed switch? Oh, yeah, the aux alternator > switch being left on would leave a hundred+ millamps of draw > on the battery. Yeah, the Dynon being lit up might be a good clue :-) > I think you're making this more complicated than > it needs to be. If the scenario that creates the situation > you're guarding against happens every fifth flight, there's > a significant human factors consideration for adding the > extra indication/warning features. But your adding "stuff" > to a system to remind you that you've just experienced > a main alternator failure. Therefore, in addition a need for > getting out the toolbox after you land, you need additional > reminding to shut off the aux alternator and e-bus alternate > feed switches? Far more likely that I bump a switch accidentally and don't notice it is on. With the Dynon lit up, then I suppose the only switch that requires an indicator is the aux alternator. > I considered low voltage warning lights for the e-bus architecture > some years ago but decided against it. Flying on the e-bus only > whether supported by the SD-8 or not is an extra-ordinary happening. > An event that should cause give the pilot a heightened awareness > of protocols for a sweat-free termination of the flight. Unfortunately, the low voltage indicator in my Cessna is the radios going out after the battery is mostly discharged. The slight difference between a little charge and a little discharge on a small gauge in front of the passenger is insufficient. I do not anticipate a engine failure, but I have had an alternator failure already in my short flying career and one in pretty much every car I have owned. So I would like something better in my Tundra. Jeff Page Dream Aircraft Tundra #10 ________________________________ Message 12 ____________________________________ Time: 08:44:42 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: New EMAG and PMAG Wiring question At 08:13 PM 3/3/2008 -0800, you wrote: > > >Bob, I just looked at the new?? fig 13-8 and I have a few questions. The >Pmag wiring shown would require you to turn off the main bus to test the >PMAG self power. Yup. You don't need to test it every flight. > Is this your intention? Yes. This is Emagair's recommendation. > Would another method such as >using the Emag method shown with the addition of a switch between the bat >bus and the S700 2 10 switch also work. If so do you see any problems with >this set up? Thanks. Don No . . . except it complicates the system by adding a function that is seldom needed and easily accommodated by killing the main bus . . . like you COULD test the alternate feed switch at every pre-flight during an ignition test. Depends on how often you believe it's useful. The design goal was to accommodate needed functionality with a minimum of parts count and pilot workload. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ________________________________ Message 13 ____________________________________ Time: 09:03:57 PM PST US From: "Don Vs" Subject: RE: AeroElectric-List: New EMAG and PMAG Wiring question Thanks Bob. I forgot to mention that I have 2 PMAGS and like the idea of running them from the always hot battery bus. -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of Robert L. Nuckolls, III Sent: Monday, March 03, 2008 8:40 PM Subject: Re: AeroElectric-List: New EMAG and PMAG Wiring question At 08:13 PM 3/3/2008 -0800, you wrote: > > >Bob, I just looked at the new?? fig 13-8 and I have a few questions. The >Pmag wiring shown would require you to turn off the main bus to test the >PMAG self power. Yup. You don't need to test it every flight. > Is this your intention? Yes. This is Emagair's recommendation. > Would another method such as >using the Emag method shown with the addition of a switch between the bat >bus and the S700 2 10 switch also work. If so do you see any problems with >this set up? Thanks. Don No . . . except it complicates the system by adding a function that is seldom needed and easily accommodated by killing the main bus . . . like you COULD test the alternate feed switch at every pre-flight during an ignition test. Depends on how often you believe it's useful. The design goal was to accommodate needed functionality with a minimum of parts count and pilot workload. Bob . . . ----------------------------------------) ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------- ------------------------------------------------------------------------------------- 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.