---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Fri 09/19/08: 10 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:59 AM - Re: Rotax 914 (Duncan & Ami McFadyean) 2. 01:21 AM - Re: Rotax 914 (Craig Payne) 3. 08:22 AM - Re: Rotax 914 (Noel Loveys) 4. 09:07 AM - Re: Rotax 914 (Noel Loveys) 5. 01:09 PM - Re: carb ice revisited (avid2008) 6. 02:14 PM - Re: Rotax 914 (Duncan & Ami McFadyean) 7. 02:43 PM - Re: Rotax 914 (Craig Payne) 8. 03:26 PM - Re: Rotax 914 (Noel Loveys) 9. 03:41 PM - Re: Rotax 914 (Noel Loveys) 10. 05:48 PM - Re: carb ice revisited (Roger Lee) ________________________________ Message 1 _____________________________________ Time: 12:59:22 AM PST US From: "Duncan & Ami McFadyean" Subject: Re: RotaxEngines-List: Rotax 914 RE: RotaxEngines-List: Rotax 914Yet the Rotax manual (later versions) show grounding of the shield at both ends, with a statement to the effect that their EMI compliance is not maintained otherwise. Duncan Mcf. ----- Original Message ----- From: Noel Loveys To: rotaxengines-list@matronics.com Sent: Friday, September 19, 2008 4:20 AM Subject: RE: RotaxEngines-List: Rotax 914 The ground on the shield is to prevent the P-leads from interfering with your radios.. When you ground these leads they turn off (short out) the magnetos so the engine will stop. Generally, coax should only be grounded at one end, the engine end. Grounding at both ends makes the coax an inductive emitter if the signal is high enough on the centre lead. When you wire your plane be sure to have a good hefty braid (ground) going from the engine block across the lord mounts to a sturdy place on the frame. Doing that will lower the possibility of radio interference and it will ensure you get lots of cranking amps to your starter too. Noel _____________________________________________ From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus Kyle Sent: Thursday, September 18, 2008 11:18 AM To: ROTAXnet Subject: RotaxEngines-List: Rotax 914 Hello, I am assembling the wiring for the above model engine. In the process, I wired the dynamo module wires to coaxial cable which runs to the ignition switches, ensuring that the coax braid is exclusively connected to nearby engine ground at one end and one pole of each switch at the other. The switches are enclosed in small alum boxes attached to the panel for interference protection. I see, by Installation manual, page 75 [electric circuit, d/1996 05 10] that there seems to be an electrical ground connection to the switch frame and thus to the metal panel on which it is fixed. If that is so, then the engine frame ground extends into the cockpit via the coax. Is this the intent? What is its purpose, please? Ferg Europa A064 ________________________________ Message 2 _____________________________________ Time: 01:21:42 AM PST US From: "Craig Payne" Subject: RE: RotaxEngines-List: Rotax 914 Does it actually show the shield grounded at the switch or is the shield just connected to a terminal on the switch? The common off-left-right-both-start switch from Aircraft Spruce has terminals on it labeled "GRD" which the shields connect to. But they don't actually connect to the metal frame of the switch case. They are just the terminals that the switch connects the P leads to when killing that half of the ignition. I've attached a snippet from diagram Z-27 in the AeroElectric update on page 30 at the link below. The table shows what actually happens inside the switch. https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf -- Craig From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan & Ami McFadyean Sent: Friday, September 19, 2008 1:56 AM Subject: Re: RotaxEngines-List: Rotax 914 Yet the Rotax manual (later versions) show grounding of the shield at both ends, with a statement to the effect that their EMI compliance is not maintained otherwise. Duncan Mcf. ----- Original Message ----- From: Noel Loveys Sent: Friday, September 19, 2008 4:20 AM Subject: RE: RotaxEngines-List: Rotax 914 The ground on the shield is to prevent the P-leads from interfering with your radios.. When you ground these leads they turn off (short out) the magnetos so the engine will stop. Generally, coax should only be grounded at one end, the engine end. Grounding at both ends makes the coax an inductive emitter if the signal is high enough on the centre lead. When you wire your plane be sure to have a good hefty braid (ground) going from the engine block across the lord mounts to a sturdy place on the frame. Doing that will lower the possibility of radio interference and it will ensure you get lots of cranking amps to your starter too. Noel _____________________________________________ From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus Kyle Sent: Thursday, September 18, 2008 11:18 AM Subject: RotaxEngines-List: Rotax 914 Hello, I am assembling the wiring for the above model engine. In the process, I wired the dynamo module wires to coaxial cable which runs to the ignition switches, ensuring that the coax braid is exclusively connected to nearby engine ground at one end and one pole of each switch at the other. The switches are enclosed in small alum boxes attached to the panel for interference protection. I see, by Installation manual, page 75 [electric circuit, d/1996 05 10] that there seems to be an electrical ground connection to the switch frame and thus to the metal panel on which it is fixed. If that is so, then the engine frame ground extends into the cockpit via the coax. Is this the intent? What is its purpose, please? Ferg Europa A064 href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro nics.com/Navigator?RotaxEngines-List href="http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c ________________________________ Message 3 _____________________________________ Time: 08:22:17 AM PST US From: "Noel Loveys" Subject: RE: RotaxEngines-List: Rotax 914 That is probably true but coax is an unbalanced feed cable grounding at both ends will enable the whole wire to become a capacitive radiator. Capacitors as you know pass AC and block DC the problem is the current feeding the P-Leads is AC. Grounding at the engine end only allows any induced AC into the shield to be grounded rather than swing back and forth in the shield. The only exception to the rule is for antennae. The feed end (radio) of the coax is grounded to the case of the radio and the far end of the coax should have an good ground to form a ground plane for the antenna radiator. In that case the ground part of the antenna end should be very clean. A lot of problems with com radios rise from corroded ground terminals at the antenna end. That is one of the first things I will check when there is a radio problem in an airplane. A bad ground in that location can cause other physical problems within the radio itself. The same thing is true for other avionics. Good clean grounds and shielded cables grounded at the source end only. Rotax may have specified double grounding because of bad grounds across the engine mounts. That could have caused the P-Lead not to work properly. It is my personal experience as a Canadian AME intern (Aircraft Maintenance Engineer) with specialty training in avionics and an Amateur Radio operator with an advanced licence for over twenty years, that 90 % of electrical and avionics problems are due to bad grounding. The general rule of thumb is to ground closest to the source. This grounding at one end only should continue throughout the full avionics suite. Perhaps if there is someone from the Rotax design team on line they could let us know why they spec double grounding of coaxial cable. Noel From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan & Ami McFadyean Sent: Friday, September 19, 2008 5:26 AM Subject: Re: RotaxEngines-List: Rotax 914 Yet the Rotax manual (later versions) show grounding of the shield at both ends, with a statement to the effect that their EMI compliance is not maintained otherwise. Duncan Mcf. ----- Original Message ----- From: Noel Loveys Sent: Friday, September 19, 2008 4:20 AM Subject: RE: RotaxEngines-List: Rotax 914 The ground on the shield is to prevent the P-leads from interfering with your radios.. When you ground these leads they turn off (short out) the magnetos so the engine will stop. Generally, coax should only be grounded at one end, the engine end. Grounding at both ends makes the coax an inductive emitter if the signal is high enough on the centre lead. When you wire your plane be sure to have a good hefty braid (ground) going from the engine block across the lord mounts to a sturdy place on the frame. Doing that will lower the possibility of radio interference and it will ensure you get lots of cranking amps to your starter too. Noel _____________________________________________ From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus Kyle Sent: Thursday, September 18, 2008 11:18 AM Subject: RotaxEngines-List: Rotax 914 Hello, I am assembling the wiring for the above model engine. In the process, I wired the dynamo module wires to coaxial cable which runs to the ignition switches, ensuring that the coax braid is exclusively connected to nearby engine ground at one end and one pole of each switch at the other. The switches are enclosed in small alum boxes attached to the panel for interference protection. I see, by Installation manual, page 75 [electric circuit, d/1996 05 10] that there seems to be an electrical ground connection to the switch frame and thus to the metal panel on which it is fixed. If that is so, then the engine frame ground extends into the cockpit via the coax. Is this the intent? What is its purpose, please? Ferg Europa A064 href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro nics.com/Navigator?RotaxEngines-List href="http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c ________________________________ Message 4 _____________________________________ Time: 09:07:27 AM PST US From: "Noel Loveys" Subject: RE: RotaxEngines-List: Rotax 914 You're spot on. The shield is only grounded at the switch end when the mag is turned off. Fig Z-11 Noel From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig Payne Sent: Friday, September 19, 2008 5:51 AM Subject: RE: RotaxEngines-List: Rotax 914 Does it actually show the shield grounded at the switch or is the shield just connected to a terminal on the switch? The common off-left-right-both-start switch from Aircraft Spruce has terminals on it labeled "GRD" which the shields connect to. But they don't actually connect to the metal frame of the switch case. They are just the terminals that the switch connects the P leads to when killing that half of the ignition. I've attached a snippet from diagram Z-27 in the AeroElectric update on page 30 at the link below. The table shows what actually happens inside the switch. https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf -- Craig From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan & Ami McFadyean Sent: Friday, September 19, 2008 1:56 AM Subject: Re: RotaxEngines-List: Rotax 914 Yet the Rotax manual (later versions) show grounding of the shield at both ends, with a statement to the effect that their EMI compliance is not maintained otherwise. Duncan Mcf. ----- Original Message ----- From: Noel Loveys Sent: Friday, September 19, 2008 4:20 AM Subject: RE: RotaxEngines-List: Rotax 914 The ground on the shield is to prevent the P-leads from interfering with your radios.. When you ground these leads they turn off (short out) the magnetos so the engine will stop. Generally, coax should only be grounded at one end, the engine end. Grounding at both ends makes the coax an inductive emitter if the signal is high enough on the centre lead. When you wire your plane be sure to have a good hefty braid (ground) going from the engine block across the lord mounts to a sturdy place on the frame. Doing that will lower the possibility of radio interference and it will ensure you get lots of cranking amps to your starter too. Noel _____________________________________________ From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus Kyle Sent: Thursday, September 18, 2008 11:18 AM Subject: RotaxEngines-List: Rotax 914 Hello, I am assembling the wiring for the above model engine. In the process, I wired the dynamo module wires to coaxial cable which runs to the ignition switches, ensuring that the coax braid is exclusively connected to nearby engine ground at one end and one pole of each switch at the other. The switches are enclosed in small alum boxes attached to the panel for interference protection. I see, by Installation manual, page 75 [electric circuit, d/1996 05 10] that there seems to be an electrical ground connection to the switch frame and thus to the metal panel on which it is fixed. If that is so, then the engine frame ground extends into the cockpit via the coax. Is this the intent? What is its purpose, please? Ferg Europa A064 href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro nics.com/Navigator?RotaxEngines-List href="http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c http://www.matronics.com/Navigator?RotaxEngines-List http://forums.matronics.com http://www.matronics.com/contribution ________________________________ Message 5 _____________________________________ Time: 01:09:43 PM PST US Subject: RotaxEngines-List: Re: carb ice revisited From: "avid2008" Roger, I have always been told that R912 is pretty much ice-proof. Last winter I discovered the contrary although it must be said in all fairness that conditions were prone to icing. I purchaised a Rotax 912 powered Avid Flyer and was ferrying it accross Europe in the company of the previous owner. It was around 0C and very humid; the guy was running it at 4500rpm. After about 20min of flight I noticed that revs were around 4200 and quite uneven; I pushed in some more throttle with no effect, then after some 30-60secs suddenly revs came up to 5000. We kept it at 4800-5000 for the rest of the day( 6hrs/2 landings) without any further problem. The next day the valley where we stopped for the night was filled with stratus and occasionally there were some drops of rain. Hardly a VFR type of weather but we decided to try to take off. While warming up the engine I noticed that it was running VERY rough - I couldn't check above 3500rpm as the brakes were not strong enough to hold the plane, but anything below 3500rpm was very uneven. Not being certain if there is everything OK with the engine and having marginal weather we decided to postpone the takeoff. Next day I called a local FBO mechanic (I had to go back home by train) and asked him to check the engine. The weather was fine and he didn't have any problem. I feel very strongly we must have experienced carb icing. I did 70hrs with this plane since that day and I must say that on a couple of occasions I had a suspicion of icing (not as apparent as described above, but a slight irregularity below 4000rpm) in humid conditions. Adding power has always improved the situation. I must say that the Avid Flyer has huge air intakes on both sides of the prop, so presumably there is no wam air stagnating under the cowl (as it is frequently the case of modern planes with sleek cowlings). Warmer air in the carb area can probably help, although it is not a 100% solution (FAA wants to see, if memory serves me well, at least 70F air temp increase to be considered as an efficient carb heat). Martin Read this topic online here: http://forums.matronics.com/viewtopic.php?p 5127#205127 ________________________________ Message 6 _____________________________________ Time: 02:14:38 PM PST US From: "Duncan & Ami McFadyean" Subject: Re: RotaxEngines-List: Rotax 914 RE: RotaxEngines-List: Rotax 914Except that the Rotax manual shows a different set-up, with each end of the screen grounded, the switch body grounded and the centre-conductor of the shielded wire switched to a separate ground when the kill-switch is closed. The descriptions in the text of the manual confirm the indications of the diagram. Hey, don't shoot the messenger; Ask Rotax how they got it "wrong"! Duncan McF. ----- Original Message ----- From: Noel Loveys To: rotaxengines-list@matronics.com Sent: Friday, September 19, 2008 4:29 PM Subject: RE: RotaxEngines-List: Rotax 914 You're spot on. The shield is only grounded at the switch end when the mag is turned off. Fig Z-11 Noel From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig Payne Sent: Friday, September 19, 2008 5:51 AM To: rotaxengines-list@matronics.com Subject: RE: RotaxEngines-List: Rotax 914 Does it actually show the shield grounded at the switch or is the shield just connected to a terminal on the switch? The common off-left-right-both-start switch from Aircraft Spruce has terminals on it labeled "GRD" which the shields connect to. But they don't actually connect to the metal frame of the switch case. They are just the terminals that the switch connects the P leads to when killing that half of the ignition. I've attached a snippet from diagram Z-27 in the AeroElectric update on page 30 at the link below. The table shows what actually happens inside the switch. https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf -- Craig From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan & Ami McFadyean Sent: Friday, September 19, 2008 1:56 AM To: rotaxengines-list@matronics.com Subject: Re: RotaxEngines-List: Rotax 914 Yet the Rotax manual (later versions) show grounding of the shield at both ends, with a statement to the effect that their EMI compliance is not maintained otherwise. Duncan Mcf. ----- Original Message ----- From: Noel Loveys To: rotaxengines-list@matronics.com Sent: Friday, September 19, 2008 4:20 AM Subject: RE: RotaxEngines-List: Rotax 914 The ground on the shield is to prevent the P-leads from interfering with your radios.. When you ground these leads they turn off (short out) the magnetos so the engine will stop. Generally, coax should only be grounded at one end, the engine end. Grounding at both ends makes the coax an inductive emitter if the signal is high enough on the centre lead. When you wire your plane be sure to have a good hefty braid (ground) going from the engine block across the lord mounts to a sturdy place on the frame. Doing that will lower the possibility of radio interference and it will ensure you get lots of cranking amps to your starter too. Noel _____________________________________________ From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus Kyle Sent: Thursday, September 18, 2008 11:18 AM To: ROTAXnet Subject: RotaxEngines-List: Rotax 914 Hello, I am assembling the wiring for the above model engine. In the process, I wired the dynamo module wires to coaxial cable which runs to the ignition switches, ensuring that the coax braid is exclusively connected to nearby engine ground at one end and one pole of each switch at the other. The switches are enclosed in small alum boxes attached to the panel for interference protection. I see, by Installation manual, page 75 [electric circuit, d/1996 05 10] that there seems to be an electrical ground connection to the switch frame and thus to the metal panel on which it is fixed. If that is so, then the engine frame ground extends into the cockpit via the coax. Is this the intent? What is its purpose, please? Ferg Europa A064 href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www. matronics.com/Navigator?RotaxEngines-Listhref="http://forums.matronics. com">http://forums.matronics.comhref="http://www.matronics.com/contribu tion">http://www.matronics.com/c http://www.matronics.com/Navigator?RotaxEngines-List http://forums.matronics.com http://www.matronics.com/contribution ________________________________ Message 7 _____________________________________ Time: 02:43:44 PM PST US From: "Craig Payne" Subject: RE: RotaxEngines-List: Rotax 914 Do you mean figures 67 and 73 from the installation manual (or the equivalent)? I've attached a copy of each. They certainly do appear to be grounding both ends of the shield in figure 73. -- Craig From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan & Ami McFadyean Sent: Friday, September 19, 2008 3:11 PM Subject: Re: RotaxEngines-List: Rotax 914 Except that the Rotax manual shows a different set-up, with each end of the screen grounded, the switch body grounded and the centre-conductor of the shielded wire switched to a separate ground when the kill-switch is closed. The descriptions in the text of the manual confirm the indications of the diagram. Hey, don't shoot the messenger; Ask Rotax how they got it "wrong"! Duncan McF. ----- Original Message ----- From: Noel Loveys Sent: Friday, September 19, 2008 4:29 PM Subject: RE: RotaxEngines-List: Rotax 914 You're spot on. The shield is only grounded at the switch end when the mag is turned off. Fig Z-11 Noel From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig Payne Sent: Friday, September 19, 2008 5:51 AM Subject: RE: RotaxEngines-List: Rotax 914 Does it actually show the shield grounded at the switch or is the shield just connected to a terminal on the switch? The common off-left-right-both-start switch from Aircraft Spruce has terminals on it labeled "GRD" which the shields connect to. But they don't actually connect to the metal frame of the switch case. They are just the terminals that the switch connects the P leads to when killing that half of the ignition. I've attached a snippet from diagram Z-27 in the AeroElectric update on page 30 at the link below. The table shows what actually happens inside the switch. https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf -- Craig From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan & Ami McFadyean Sent: Friday, September 19, 2008 1:56 AM Subject: Re: RotaxEngines-List: Rotax 914 Yet the Rotax manual (later versions) show grounding of the shield at both ends, with a statement to the effect that their EMI compliance is not maintained otherwise. Duncan Mcf. ----- Original Message ----- From: Noel Loveys Sent: Friday, September 19, 2008 4:20 AM Subject: RE: RotaxEngines-List: Rotax 914 The ground on the shield is to prevent the P-leads from interfering with your radios.. When you ground these leads they turn off (short out) the magnetos so the engine will stop. Generally, coax should only be grounded at one end, the engine end. Grounding at both ends makes the coax an inductive emitter if the signal is high enough on the centre lead. When you wire your plane be sure to have a good hefty braid (ground) going from the engine block across the lord mounts to a sturdy place on the frame. Doing that will lower the possibility of radio interference and it will ensure you get lots of cranking amps to your starter too. Noel _____________________________________________ From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus Kyle Sent: Thursday, September 18, 2008 11:18 AM Subject: RotaxEngines-List: Rotax 914 Hello, I am assembling the wiring for the above model engine. In the process, I wired the dynamo module wires to coaxial cable which runs to the ignition switches, ensuring that the coax braid is exclusively connected to nearby engine ground at one end and one pole of each switch at the other. The switches are enclosed in small alum boxes attached to the panel for interference protection. I see, by Installation manual, page 75 [electric circuit, d/1996 05 10] that there seems to be an electrical ground connection to the switch frame and thus to the metal panel on which it is fixed. If that is so, then the engine frame ground extends into the cockpit via the coax. Is this the intent? What is its purpose, please? Ferg Europa A064 href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro nics.com/Navigator?RotaxEngines-List href="http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c http://www.matronics.com/Navigator?RotaxEngines-List http://forums.matronics.com http://www.matronics.com/contribution href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro nics.com/Navigator?RotaxEngines-List href="http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c ________________________________ Message 8 _____________________________________ Time: 03:26:03 PM PST US From: "Noel Loveys" Subject: RE: RotaxEngines-List: Rotax 914 We don't shoot messengers around here except with shots of Scotch, Rum, Corn or Brandy! Double barrels are encouraged by most victims! I would be interested in why Rotax specifies both ends of the shield to be grounded though. Anyone have any ideas? Noel From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan & Ami McFadyean Sent: Friday, September 19, 2008 6:41 PM Subject: Re: RotaxEngines-List: Rotax 914 Except that the Rotax manual shows a different set-up, with each end of the screen grounded, the switch body grounded and the centre-conductor of the shielded wire switched to a separate ground when the kill-switch is closed. The descriptions in the text of the manual confirm the indications of the diagram. Hey, don't shoot the messenger; Ask Rotax how they got it "wrong"! Duncan McF. ----- Original Message ----- From: Noel Loveys Sent: Friday, September 19, 2008 4:29 PM Subject: RE: RotaxEngines-List: Rotax 914 You're spot on. The shield is only grounded at the switch end when the mag is turned off. Fig Z-11 Noel From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig Payne Sent: Friday, September 19, 2008 5:51 AM Subject: RE: RotaxEngines-List: Rotax 914 Does it actually show the shield grounded at the switch or is the shield just connected to a terminal on the switch? The common off-left-right-both-start switch from Aircraft Spruce has terminals on it labeled "GRD" which the shields connect to. But they don't actually connect to the metal frame of the switch case. They are just the terminals that the switch connects the P leads to when killing that half of the ignition. I've attached a snippet from diagram Z-27 in the AeroElectric update on page 30 at the link below. The table shows what actually happens inside the switch. https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf -- Craig From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan & Ami McFadyean Sent: Friday, September 19, 2008 1:56 AM Subject: Re: RotaxEngines-List: Rotax 914 Yet the Rotax manual (later versions) show grounding of the shield at both ends, with a statement to the effect that their EMI compliance is not maintained otherwise. Duncan Mcf. ----- Original Message ----- From: Noel Loveys Sent: Friday, September 19, 2008 4:20 AM Subject: RE: RotaxEngines-List: Rotax 914 The ground on the shield is to prevent the P-leads from interfering with your radios.. When you ground these leads they turn off (short out) the magnetos so the engine will stop. Generally, coax should only be grounded at one end, the engine end. Grounding at both ends makes the coax an inductive emitter if the signal is high enough on the centre lead. When you wire your plane be sure to have a good hefty braid (ground) going from the engine block across the lord mounts to a sturdy place on the frame. Doing that will lower the possibility of radio interference and it will ensure you get lots of cranking amps to your starter too. Noel _____________________________________________ From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus Kyle Sent: Thursday, September 18, 2008 11:18 AM Subject: RotaxEngines-List: Rotax 914 Hello, I am assembling the wiring for the above model engine. In the process, I wired the dynamo module wires to coaxial cable which runs to the ignition switches, ensuring that the coax braid is exclusively connected to nearby engine ground at one end and one pole of each switch at the other. The switches are enclosed in small alum boxes attached to the panel for interference protection. I see, by Installation manual, page 75 [electric circuit, d/1996 05 10] that there seems to be an electrical ground connection to the switch frame and thus to the metal panel on which it is fixed. If that is so, then the engine frame ground extends into the cockpit via the coax. Is this the intent? What is its purpose, please? Ferg Europa A064 href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro nics.com/Navigator?RotaxEngines-List href="http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c http://www.matronics.com/Navigator?RotaxEngines-List http://forums.matronics.com http://www.matronics.com/contribution href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro nics.com/Navigator?RotaxEngines-List href="http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c ________________________________ Message 9 _____________________________________ Time: 03:41:31 PM PST US From: "Noel Loveys" Subject: RE: RotaxEngines-List: Rotax 914 It may be that with the conductor only grounded at one end the mag(s) may be cut off because of EMI within the cable... that's the way I read it. However grounding at both ends will no doubt cause a great increase in RFI. In such a case I'd recommend a double shielded wire with the outside shield grounded at the engine end only. Sounds like a catch 22. Either the engine may shut itself down or you won't be able to receive any thing on your radios...Com or nav. One thing is for sure I'm going to get the chance to find out for sure in the very near future as I'm installing a 912 in my plane. Noel From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig Payne Sent: Friday, September 19, 2008 7:13 PM Subject: RE: RotaxEngines-List: Rotax 914 Do you mean figures 67 and 73 from the installation manual (or the equivalent)? I've attached a copy of each. They certainly do appear to be grounding both ends of the shield in figure 73. -- Craig From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan & Ami McFadyean Sent: Friday, September 19, 2008 3:11 PM Subject: Re: RotaxEngines-List: Rotax 914 Except that the Rotax manual shows a different set-up, with each end of the screen grounded, the switch body grounded and the centre-conductor of the shielded wire switched to a separate ground when the kill-switch is closed. The descriptions in the text of the manual confirm the indications of the diagram. Hey, don't shoot the messenger; Ask Rotax how they got it "wrong"! Duncan McF. ----- Original Message ----- From: Noel Loveys Sent: Friday, September 19, 2008 4:29 PM Subject: RE: RotaxEngines-List: Rotax 914 You're spot on. The shield is only grounded at the switch end when the mag is turned off. Fig Z-11 Noel From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Craig Payne Sent: Friday, September 19, 2008 5:51 AM Subject: RE: RotaxEngines-List: Rotax 914 Does it actually show the shield grounded at the switch or is the shield just connected to a terminal on the switch? The common off-left-right-both-start switch from Aircraft Spruce has terminals on it labeled "GRD" which the shields connect to. But they don't actually connect to the metal frame of the switch case. They are just the terminals that the switch connects the P leads to when killing that half of the ignition. I've attached a snippet from diagram Z-27 in the AeroElectric update on page 30 at the link below. The table shows what actually happens inside the switch. https://matronics.com/aeroelectric/articles/Rev11/AppZ_R11M.pdf -- Craig From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Duncan & Ami McFadyean Sent: Friday, September 19, 2008 1:56 AM Subject: Re: RotaxEngines-List: Rotax 914 Yet the Rotax manual (later versions) show grounding of the shield at both ends, with a statement to the effect that their EMI compliance is not maintained otherwise. Duncan Mcf. ----- Original Message ----- From: Noel Loveys Sent: Friday, September 19, 2008 4:20 AM Subject: RE: RotaxEngines-List: Rotax 914 The ground on the shield is to prevent the P-leads from interfering with your radios.. When you ground these leads they turn off (short out) the magnetos so the engine will stop. Generally, coax should only be grounded at one end, the engine end. Grounding at both ends makes the coax an inductive emitter if the signal is high enough on the centre lead. When you wire your plane be sure to have a good hefty braid (ground) going from the engine block across the lord mounts to a sturdy place on the frame. Doing that will lower the possibility of radio interference and it will ensure you get lots of cranking amps to your starter too. Noel _____________________________________________ From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Fergus Kyle Sent: Thursday, September 18, 2008 11:18 AM Subject: RotaxEngines-List: Rotax 914 Hello, I am assembling the wiring for the above model engine. In the process, I wired the dynamo module wires to coaxial cable which runs to the ignition switches, ensuring that the coax braid is exclusively connected to nearby engine ground at one end and one pole of each switch at the other. The switches are enclosed in small alum boxes attached to the panel for interference protection. I see, by Installation manual, page 75 [electric circuit, d/1996 05 10] that there seems to be an electrical ground connection to the switch frame and thus to the metal panel on which it is fixed. If that is so, then the engine frame ground extends into the cockpit via the coax. Is this the intent? What is its purpose, please? Ferg Europa A064 href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro nics.com/Navigator?RotaxEngines-List href="http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c http://www.matronics.com/Navigator?RotaxEngines-List http://forums.matronics.com http://www.matronics.com/contribution href="http://www.matronics.com/Navigator?RotaxEngines-List">http://www.matro nics.com/Navigator?RotaxEngines-List href="http://forums.matronics.com">http://forums.matronics.com href="http://www.matronics.com/contribution">http://www.matronics.com/c http://www.matronics.com/Navigator?RotaxEngines-List http://forums.matronics.com http://www.matronics.com/contribution ________________________________ Message 10 ____________________________________ Time: 05:48:01 PM PST US Subject: RotaxEngines-List: Re: carb ice revisited From: "Roger Lee" Hi Guys, Please don't take my next comment as being a smart ass, but how do you guys know if it was really icing without any confirmation and have you ruled out all other possibilities? Without confirmation it still is speculation. These are not standard carbs like the ones we were raised with during our life, but quite different. These are variable venturi carbs. That in itself makes them less prone to standard icing effects. -------- Roger Lee Tucson, Az. Light Sport Repairman - Maintenance Rated Rotax Service Center 520-574-1080 Read this topic online here: http://forums.matronics.com/viewtopic.php?p 5184#205184 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rotaxengines-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RotaxEngines-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/rotaxengines-list Browse Digests http://www.matronics.com/digest/rotaxengines-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.