---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 12/03/16: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:08 AM - Magnetos connection to ground (Carlos Trigo) 2. 05:45 AM - Re: Magnetos connection to ground (Charlie England) 3. 07:58 AM - Avionics Master (Robert L. Nuckolls, III) 4. 10:04 AM - Re: Magnetos connection to ground (Charlie England) 5. 10:33 AM - Re: Magnetos connection to ground (Robert L. Nuckolls, III) 6. 11:25 AM - Re: Magnetos connection to ground (David Lloyd) 7. 02:53 PM - Re: Magnetos connection to ground (Stuart Hutchison) ________________________________ Message 1 _____________________________________ Time: 05:08:04 AM PST US From: Carlos Trigo Subject: AeroElectric-List: Magnetos connection to ground Guys Which is the best practice to connect the Magnetos Ground terminals to the Firewall Ground "forest"? Is it recommended to wire Left and Right magnetos with separate wires, or can they be connected to each other and then to the Ground forest? And how about the wires to be used, should they be shielded or unshielded? Which gauge? One more question: for the connections from the ignition switch to both magnetos, I am using shielded wires, so should the shields be connected on both sides (like it is recommended in Tony Bingelis' books), or only on one side? In this last case, the shield should be connected in the magneto side, so is it good to connect the shield to the Ground terminal of the magneto? Thanks in advance Carlos ________________________________ Message 2 _____________________________________ Time: 05:45:37 AM PST US From: Charlie England Subject: Re: AeroElectric-List: Magnetos connection to ground On Sat, Dec 3, 2016 at 7:04 AM, Carlos Trigo wrote: > trigo@mail.telepac.pt> > > Guys > > Which is the best practice to connect the Magnetos Ground terminals to the > Firewall Ground "forest"? > Is it recommended to wire Left and Right magnetos with separate wires, or > can they be connected to each other and then to the Ground forest? > > And how about the wires to be used, should they be shielded or unshielded? > Which gauge? > > One more question: for the connections from the ignition switch to both > magnetos, I am using shielded wires, so should the shields be connected on > both sides (like it is recommended in Tony Bingelis' books), or only on one > side? > In this last case, the shield should be connected in the magneto side, so > is it good to connect the shield to the Ground terminal of the magneto? > > Thanks in advance > Carlos Hi Carlos, You don't need to carry the mag ground to the firewall. The wire from the mag to the switch should be a shielded wire, with the center conductor tied to the 'P' lead terminal and the shield tied to the mag's case, using any convenient screw on the case. The mag's case is electrically bonded to the engine, and the engine has a ground to the firewall/battery negative. The other end of the wire should have the center (P-lead) tied to one of the terminals on your switch, and the shield tied to the other terminal (or the ground terminal, if you're using a key type switch). No need to ground it locally near the switch, and I don't do it, since there's the potential of injecting mag noise into your other electronics. Grounding it locally gives the noise you're trying to shield an additional path to follow, which may be around/through other electronics. Grounding it locally can also mask a failed shield connection, because the P lead would still be shorted to ground even with the shield broken. The hazard of this is when you (or worse, someone else) is doing maintenance. If you have a broken shield & don't know it, everything will appear to be normal until someone is doing maintenance & removes a ground wire for electrical safety. If this ungrounds the engine from the rest of the airframe, the mag is now 'hot', even with the mag switch 'off'. The shielded P-lead has a dual purpose. While the engine is operating, the shield is grounded only at the mag and functions purely as a shield, to limit the radiated noise from the mag. When you turn off the mag, you're actually closing the switch contacts, and the shield serves as the ground return to short out mag's primary coil. Charlie ________________________________ Message 3 _____________________________________ Time: 07:58:56 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Avionics Master >Comments/Questions: Bob ... I took our seminar many years ago and >you suggested not to use an Avionics Master .. that you can just >turn on each component etc. So that's what i did .. and it's worked >just fine. However, I'm now redesigning my panel with remote mount >avionics .. COMM, TRANSPONDER, AUDIO PANEL etc. Now I'm curious how >I should protect these during start up? Should I now plan for a >MASTER or do I have to use individual switches for each component? > >Thank you for your expertise! > >Regards, > >Dave The avionics master switch was borne of an idea not grounded in physics. I was at Cessna in the 60's when, for reasons we didn't understand, radios were being killed in brand new airplanes by the dozens. Adding the AV Master did indeed 'help' but for reasons we did not know. Check out the writings on my website concerning the AV Master. http://tinyurl.com/mr2jk8g If you ever get to OSH, it would be interesting to stop by the booths of the manufacturer of ANY solid state device be it radio, instrument, system controller, etc. and inquire as to their recommendations for 'protecting their product from the effects of engine cranking'. If any one of them says that an AV Master is recommended, I'd like to hear about it. Since the universal adoption of DO-160 protocols about 50 years ago, risks to electronics from startup transients (or other any well understood transients) has gone to zero. Turns out that the 'radio killer' in the 1960's Cessnas was soggy batteries combined with poor design rules for the radio's newly minted solid state power supplies. That combination of shortfalls was easily and has been eliminated. Bob . . . ________________________________ Message 4 _____________________________________ Time: 10:04:42 AM PST US From: Charlie England Subject: Re: AeroElectric-List: Magnetos connection to ground On Sat, Dec 3, 2016 at 7:44 AM, Charlie England wrote: > > > On Sat, Dec 3, 2016 at 7:04 AM, Carlos Trigo > wrote: > >> trigo@mail.telepac.pt> >> >> Guys >> >> Which is the best practice to connect the Magnetos Ground terminals to >> the Firewall Ground "forest"? >> Is it recommended to wire Left and Right magnetos with separate wires, or >> can they be connected to each other and then to the Ground forest? >> >> And how about the wires to be used, should they be shielded or >> unshielded? Which gauge? >> >> One more question: for the connections from the ignition switch to both >> magnetos, I am using shielded wires, so should the shields be connected on >> both sides (like it is recommended in Tony Bingelis' books), or only on one >> side? >> In this last case, the shield should be connected in the magneto side, so >> is it good to connect the shield to the Ground terminal of the magneto? >> >> Thanks in advance >> Carlos > > Hi Carlos, > > You don't need to carry the mag ground to the firewall. The wire from the > mag to the switch should be a shielded wire, with the center conductor tied > to the 'P' lead terminal and the shield tied to the mag's case, using any > convenient screw on the case. The mag's case is electrically bonded to the > engine, and the engine has a ground to the firewall/battery negative. The > other end of the wire should have the center (P-lead) tied to one of the > terminals on your switch, and the shield tied to the other terminal (or the > ground terminal, if you're using a key type switch). No need to ground it > locally near the switch, and I don't do it, since there's the potential of > injecting mag noise into your other electronics. Grounding it locally gives > the noise you're trying to shield an additional path to follow, which may > be around/through other electronics. Grounding it locally can also mask a > failed shield connection, because the P lead would still be shorted to > ground even with the shield broken. The hazard of this is when you (or > worse, someone else) is doing maintenance. If you have a broken shield & > don't know it, everything will appear to be normal until someone is doing > maintenance & removes a ground wire for electrical safety. If this > ungrounds the engine from the rest of the airframe, the mag is now 'hot', > even with the mag switch 'off'. > > The shielded P-lead has a dual purpose. While the engine is operating, the > shield is grounded only at the mag and functions purely as a shield, to > limit the radiated noise from the mag. When you turn off the mag, you're > actually closing the switch contacts, and the shield serves as the ground > return to short out mag's primary coil. > > Charlie > > Forgot to add, each mag should be a separate entity, with its own shielded P-lead. The only thing that should be common is (potentially) the grounding (shutdown) terminal(s) in the switch, if you're using a key-switch type control for the mags. If you're using toggles, then nothing would be common between the mags' wiring. ________________________________ Message 5 _____________________________________ Time: 10:33:24 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Magnetos connection to ground At 07:04 AM 12/3/2016, you wrote: > >Guys > >Which is the best practice to connect the Magnetos Ground terminals >to the Firewall Ground "forest"? >Is it recommended to wire Left and Right magnetos with separate >wires, or can they be connected to each other and then to the Ground forest? > >And how about the wires to be used, should they be shielded or >unshielded? Which gauge? They can be any size . . . but 20AWG or larger is sort of standard practice for mechanical robustness. Some OEM TC airplane guys don't use anything smaller than 20AWG under the cowl. >One more question: for the connections from the ignition switch to >both magnetos, I am using shielded wires, so should the shields be >connected on both sides (like it is recommended in Tony Bingelis' >books), or only on one side? >In this last case, the shield should be connected in the magneto >side, so is it good to connect the shield to the Ground terminal of >the magneto? Here is the recommended configuration for managing p-leads. Emacs! This connection philosophy offers greatest noise control and eliminates any potential for burning the p-leads with starter current in the event that the crankcase bonding jumper is disconnected (don't laugh . . . I've seen it happen twice). Bob . . . ________________________________ Message 6 _____________________________________ Time: 11:25:23 AM PST US From: "David Lloyd" Subject: Re: AeroElectric-List: Magnetos connection to ground A comment about the P-lead mounting. That wire connection at the mag is subject to a lot of vibration and turbul ence. Secure the P-lead as if a room full of kindergarten kids are going to use i t as a tug of rope game. We all know the danger of a disconnected P-lead leaving the mag hot and rea dy to fire a plug if the prop is moved. --------------------------------------------------------------------------- ----- ----- Original Message ----- From: Charlie England To: aeroelectric-list@matronics.com Sent: Saturday, December 03, 2016 10:03 AM Subject: Re: AeroElectric-List: Magnetos connection to ground On Sat, Dec 3, 2016 at 7:44 AM, Charlie England wr ote: On Sat, Dec 3, 2016 at 7:04 AM, Carlos Trigo wr ote: epac.pt> Guys Which is the best practice to connect the Magnetos Ground terminals t o the Firewall Ground "forest"? Is it recommended to wire Left and Right magnetos with separate wires , or can they be connected to each other and then to the Ground forest? And how about the wires to be used, should they be shielded or unshie lded? Which gauge? One more question: for the connections from the ignition switch to bo th magnetos, I am using shielded wires, so should the shields be connected on both sides (like it is recommended in Tony Bingelis' books), or only on one side? In this last case, the shield should be connected in the magneto side , so is it good to connect the shield to the Ground terminal of the magneto ? Thanks in advance Carlos Hi Carlos, You don't need to carry the mag ground to the firewall. The wire from t he mag to the switch should be a shielded wire, with the center conductor t ied to the 'P' lead terminal and the shield tied to the mag's case, using a ny convenient screw on the case. The mag's case is electrically bonded to t he engine, and the engine has a ground to the firewall/battery negative. Th e other end of the wire should have the center (P-lead) tied to one of the terminals on your switch, and the shield tied to the other terminal (or the ground terminal, if you're using a key type switch). No need to ground it locally near the switch, and I don't do it, since there's the potential of injecting mag noise into your other electronics. Grounding it locally gives the noise you're trying to shield an additional path to follow, which may be around/through other electronics. Grounding it locally can also mask a f ailed shield connection, because the P lead would still be shorted to groun d even with the shield broken. The hazard of this is when you (or worse, so meone else) is doing maintenance. If you have a broken shield & don't know it, everything will appear to be normal until someone is doing maintenance & removes a ground wire for electrical safety. If this ungrounds the engine from the rest of the airframe, the mag is now 'hot', even with the mag swi tch 'off'. The shielded P-lead has a dual purpose. While the engine is operating, the shield is grounded only at the mag and functions purely as a shield, to limit the radiated noise from the mag. When you turn off the mag, you're a ctually closing the switch contacts, and the shield serves as the ground re turn to short out mag's primary coil. Charlie Forgot to add, each mag should be a separate entity, with its own shielde d P-lead. The only thing that should be common is (potentially) the groundi ng (shutdown) terminal(s) in the switch, if you're using a key-switch type control for the mags. If you're using toggles, then nothing would be common between the mags' wiring. --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ________________________________ Message 7 _____________________________________ Time: 02:53:25 PM PST US From: Stuart Hutchison Subject: Re: AeroElectric-List: Magnetos connection to ground Yes, dangers such as this recent example . that caught the pilot by surprise because the switches were left on . https://youtu.be/XFqDZagVeJU > On 4 Dec. 2016, at 06:23, David Lloyd wrote: > > A comment about the P-lead mounting. > > That wire connection at the mag is subject to a lot of vibration and turbulence. > Secure the P-lead as if a room full of kindergarten kids are going to use it as a tug of rope game. > We all know the danger of a disconnected P-lead leaving the mag hot and ready to fire a plug if the prop is moved. > >> ----- Original Message ----- >> From: Charlie England >> To: aeroelectric-list@matronics.com >> Sent: Saturday, December 03, 2016 10:03 AM >> Subject: Re: AeroElectric-List: Magnetos connection to ground >> >> >> >> On Sat, Dec 3, 2016 at 7:44 AM, Charlie England > wrote: >>> >>> >>> On Sat, Dec 3, 2016 at 7:04 AM, Carlos Trigo > wrote: > >>>> >>>> Guys >>>> >>>> Which is the best practice to connect the Magnetos Ground terminals to the Firewall Ground "forest"? >>>> Is it recommended to wire Left and Right magnetos with separate wires, or can they be connected to each other and then to the Ground forest? >>>> >>>> And how about the wires to be used, should they be shielded or unshielded? Which gauge? >>>> >>>> One more question: for the connections from the ignition switch to both magnetos, I am using shielded wires, so should the shields be connected on both sides (like it is recommended in Tony Bingelis' books), or only on one side? >>>> In this last case, the shield should be connected in the magneto side, so is it good to connect the shield to the Ground terminal of the magneto? >>>> >>>> Thanks in advance >>>> Carlos >>> Hi Carlos, >>> >>> You don't need to carry the mag ground to the firewall. The wire from the mag to the switch should be a shielded wire, with the center conductor tied to the 'P' lead terminal and the shield tied to the mag's case, using any convenient screw on the case. The mag's case is electrically bonded to the engine, and the engine has a ground to the firewall/battery negative. The other end of the wire should have the center (P-lead) tied to one of the terminals on your switch, and the shield tied to the other terminal (or the ground terminal, if you're using a key type switch). No need to ground it locally near the switch, and I don't do it, since there's the potential of injecting mag noise into your other electronics. Grounding it locally gives the noise you're trying to shield an additional path to follow, which may be around/through other electronics. Grounding it locally can also mask a failed shield connection, because the P lead would still be shorted to ground even with the shield broken. The hazard of this is when you (or worse, someone else) is doing maintenance. If you have a broken shield & don't know it, everything will appear to be normal until someone is doing maintenance & removes a ground wire for electrical safety. If this ungrounds the engine from the rest of the airframe, the mag is now 'hot', even with the mag switch 'off'. >>> >>> The shielded P-lead has a dual purpose. While the engine is operating, the shield is grounded only at the mag and functions purely as a shield, to limit the radiated noise from the mag. When you turn off the mag, you're actually closing the switch contacts, and the shield serves as the ground return to short out mag's primary coil. >>> >>> Charlie >>> >> Forgot to add, each mag should be a separate entity, with its own shielded P-lead. The only thing that should be common is (potentially) the grounding (shutdown) terminal(s) in the switch, if you're using a key-switch type control for the mags. If you're using toggles, then nothing would be common between the mags' wiring. > > > > This email has been checked for viruses by Avast antivirus software. > www.avast.com > ------------------------------------------------------------------------------------- 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.