---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 01/25/12: 26 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:47 AM - Larger D-Sub pins (Stuart Hutchison) 2. 02:32 AM - Re: Antenna Installation Question (Jared Yates) 3. 06:05 AM - Instrument Earth Bus cable size (MikeDunlop) 4. 06:19 AM - Re: Instrument Earth Bus cable size (user9253) 5. 06:28 AM - Re: Weak and Static on Transmission (user9253) 6. 06:55 AM - Re: Instrument Earth Bus cable size (George, Neal Capt 505 TRS/DOJ) 7. 07:20 AM - Re: Instrument Earth Bus cable size (ROGER & JEAN CURTIS) 8. 07:22 AM - Re: Re: Weak and Static on Transmission (Bill Bradburry) 9. 07:56 AM - Re: Larger D-Sub pins (John Grosse) 10. 08:39 AM - Re: Larger D-Sub pins (Stein Bruch) 11. 08:53 AM - Re: Fuses instead of breakers (Robert L. Nuckolls, III) 12. 09:08 AM - Re: Larger D-Sub pins (John Grosse) 13. 09:08 AM - Fuses instead of breakers (Dennis Johnson) 14. 09:13 AM - Re: Antenna Installation Question (Robert L. Nuckolls, III) 15. 09:27 AM - Re: Fuses instead of breakers (Ed Holyoke) 16. 09:29 AM - Re: Larger D-Sub pins (Robert L. Nuckolls, III) 17. 09:47 AM - Re: Instrument Earth Bus cable size (Robert L. Nuckolls, III) 18. 09:48 AM - Re: Fuses instead of breakers (Robert L. Nuckolls, III) 19. 10:00 AM - Re: Fuses instead of breakers (Robert L. Nuckolls, III) 20. 02:11 PM - Re: Instrument Earth Bus cable size (MikeDunlop) 21. 02:29 PM - Re: Fuses instead of breakers (Jeff Page) 22. 06:40 PM - Re: Fuses instead of breakers (bcondrey) 23. 06:52 PM - Re: Re: Fuses instead of breakers (Robert L. Nuckolls, III) 24. 06:55 PM - Re: Re: Fuses instead of breakers (Robert L. Nuckolls, III) 25. 07:51 PM - Re: Re: Fuses instead of breakers (Jeff B.) 26. 08:31 PM - Re: Re: Fuses instead of breakers (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 01:47:14 AM PST US From: "Stuart Hutchison" Subject: AeroElectric-List: Larger D-Sub pins G'day all, Has anyone found a convenient after-market supplier for the D-Sub pins with an oversize butt that Garmin include in some installation kits? The Garmin part number is 336-00023-00 and they're physically longer with a larger crimp cup to fit 18 AWG wire ... I want to parallel looms into a single connector ... and it seems that paired 22 (and perhaps 20) AWG wires will fit in these pins. Sadly I only have three of them :) Kind regards, Stu F1 Rocket VH-FLY http://www.mykitlog.com/RockFLY www.teamrocketaircraft.com -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: Wednesday, January 25, 2012 3:08 PM Subject: Re: AeroElectric-List: Re: Antenna Installation Question --> At 08:36 PM 1/24/2012, you wrote: > > > > > the teeth of the lock washers should bite through any > paint/primer into the surface of the skin. > > >Thanks Charlie. I know this makes a good D.C. ground, but I'm not sure >how well it grounds at 100+ MHz. Maybe Bob could speak to that. It's nigh on to impossible to get the 'ideal' bond between antenna base and skin without welding it. Further, adding a cork gasket under the base puts a 'resilient' material in the stack-up of parts under 'crush'. See: http://aeroelectric.com/Pictures/Antenna/Comm_Antenna_Installation.gif Since all electrical connections MUST come though the mounting hardware, getting the highest practical make up forces goes directly to gas-tightness of the connections at interfaces marked with (*). All this happens within a few tenths of an inch of the center of each screw. Taking all the paint off skin under the antenna adds nothing. I'd pitch the cork. Drill out the base holes to take at least a #10 screw (if not already that large). Clean the mate up surfaces marked (*) to bright. Run a thin bead of RTV around the perimeter of the base before pressing it into place on the aircraft. Tighten the screws to spec limits. Using grade 8 hardware will let you get some real, lasting pressure in the joints. Bob . . . Bob . . . ________________________________ Message 2 _____________________________________ Time: 02:32:53 AM PST US Subject: Re: AeroElectric-List: Antenna Installation Question From: Jared Yates I fly airplanes in the high flight levels and even there we use the top antenna primarily. I've thought about it before, and I think a "to scale" diagram would explain why. Even though 5-6 miles seems high by altitude standards, it's not very far laterally. If the rco or tower is 20 or even 100 miles away, the acute angle in the triangle is small. To visualize more easily, think of the distance in feet instead of miles. The angles are the same regardless of the units of course. If you stood 5 feet below your antenna's base and 100 feet away, would the antenna be visible? Likewise at 20 and even 5 feet, it is probably visible from most angles. If it is blocked by the wing or some other piece of airplane, then it will likely not be for long in flight. On Jan 24, 2012, at 21:29, "Noel Loveys" wrote: > > The cork gasket goes directly under the antenna, between the antenna and the > skin to prevent water from penetrating the skin under the base. The antenna > grounds through the washer and mounting nut inside the skin. This is > important as this is a ground plane for the antenna. Clean off the alodine, > or zinc chromate from inside the skin around where the mounting nut and > washer grip the inside of the skin. > >> From here I'm assuming that you have a cloth plane... > Cloth planes usually have a frame structure under the cloth physically > strong enough to hold a com. ant. but you may need to install you own foil > ground plane. If this is your case then make sure your ground plane is well > grounded through the outside of the antenna connector or preferably the > mounting nut. > > Small planes generally have their com antenna on top of the plane... away > from landing gear and other parasitic elements like landing gear. Being on > top is adequate to talk with towers and a good location to communicate with > other aircraft. If you expect to fly above FL2.0 you may need a com Ant on > the bottom of your plane to contact ATC. > > > Noel > > -----Original Message----- > From: owner-aeroelectric-list-server@matronics.com > [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of > tomcostanza > Sent: January 24, 2012 8:57 PM > To: aeroelectric-list@matronics.com > Subject: AeroElectric-List: Antenna Installation Question > > > > Hi, > > Comant instructions for a comm antenna installation says to mount the > antenna base directly to the skin for proper electrical bonding. Makes > sense to me. Then they include a cork gasket with the antenna. Any > suggestions? > > I was planning to alodine the skin under the antenna base. Should I put > dielectric grease or anything else between the base and the skin? > > -------- > Clear Skies, > Tom Costanza > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=364738#364738 > > > > > > > > > > > > > > ________________________________ Message 3 _____________________________________ Time: 06:05:29 AM PST US Subject: AeroElectric-List: Instrument Earth Bus cable size From: "MikeDunlop" Starting a new topic to avoid confusion with previous attempts at a simple explanation. I'm building a Long-EZ with a Odyssey PC925 battery in the nose section, there is one 0.5 inch copper tube conduit that runs from the nose section to the firewall at the rear. The positive cables (# 2 welding cable) will run from the battery to the master switch in the nose section (6 to 7 inches), from the master switch through the earth conduit to the starter solenoid way back on the firewall (about 10 ft), then from solenoid to starter. The earth cable (# 2 welding cable) will run from the battery to the copper tab on the front of the earth conduit, just behind the nose section (20 inches). The earth is then picked up from the rear copper tab of the earth conduit, on the engine side of the firewall, by means of a copper braided strap between conduit and engine. So I presume (dangerous thing to do!) the cranking current runs through the copper conduit. My question is: What is the minimum size cable can I use from the copper tab on the FRONT of the earth conduit tab (just behind the nose section) to the instrument earth bus (approx 18-20 inches in length). I'm trying to avoid using the very heavy welding cable. Copper Tube Conduit ----------------------------- Bat Pos ++++++++ # 2 welding cable ++++++++++ ----------------------------- Bat Neg ---------|Tab| |Tab|----- Neg (firewall side) | |#? | Instrument Earth Bus MikeD (U.K.) Read this topic online here: http://forums.matronics.com/viewtopic.php?p=364793#364793 ________________________________ Message 4 _____________________________________ Time: 06:19:12 AM PST US Subject: AeroElectric-List: Re: Instrument Earth Bus cable size From: "user9253" > My question is: > What is the minimum size cable can I use from the copper tab on the FRONT of the earth conduit tab (just behind the nose section) to the instrument earth bus (approx 18-20 inches in length). Use the same size wire for the negative as is used for the positive supply to the instrument panel. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=364795#364795 ________________________________ Message 5 _____________________________________ Time: 06:28:22 AM PST US Subject: AeroElectric-List: Re: Weak and Static on Transmission From: "user9253" > When I first flying my new home built airplane it was fine, crystal clear both transmission and receiving. However, something changed, now I can hardly understand transmissions. I haven't yet been able to put my finger on what's changed and causing it. jerryb The vast majority of electrical problems are caused by bad connections. I suggest that each connection be disassembled, mating surfaces cleaned, and fasteners tightened. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=364796#364796 ________________________________ Message 6 _____________________________________ Time: 06:55:21 AM PST US Subject: RE: AeroElectric-List: Instrument Earth Bus cable size From: "George, Neal Capt 505 TRS/DOJ" Mike - It depends. Have you worked a load analysis for the equipment that would be serviced by the panel ground? Referring to the wire chart in The AeroElectric Connection, Chapter 8, a length of #8 copper wire is expected to carry about 22 amps continuous with less than 10-deg C rise in the wire temp. neal -----Original Message----- From: On Behalf Of MikeDunlop My question is: What is the minimum size cable can I use from the copper tab on the FRONT of the earth conduit tab (just behind the nose section) to the instrument earth bus (approx 18-20 inches in length). I'm trying to avoid using the very heavy welding cable. MikeD (U.K.) ________________________________ Message 7 _____________________________________ Time: 07:20:59 AM PST US From: "ROGER & JEAN CURTIS" Subject: RE: AeroElectric-List: Instrument Earth Bus cable size My question is: What is the minimum size cable can I use from the copper tab on the FRONT of the earth conduit tab (just behind the nose section) to the instrument earth bus (approx 18-20 inches in length). I'm trying to avoid using the very heavy welding cable. Mike, It appears that the current running through this wire is only that used in the instrument panel. You really need to add up all the loads from the avionics, lights, and other electrical devices that connect through this ground, then calculate the conductor size. Your + feed wire should be of the same gauge. Once you know the total load you can see Bob's Wire size calculator here: http://www.aeroelectric.com/articles/wiresize.pdf Hope this helps. Roger ________________________________ Message 8 _____________________________________ Time: 07:22:18 AM PST US From: "Bill Bradburry" Subject: RE: AeroElectric-List: Re: Weak and Static on Transmission Jerryb, The engine is a Mazda Renesis rotary. It is a 4 stroke engine but has no valves, so it is somewhat like a two stroke. The voltage regulator is a Transpo V1200. I am trying to use a ICOM IC-A6 handheld radio with little or no success. My problems are evolving as well. I was previously getting "5 by 5" responses from the tower on radio checks. Now it is "weak but usable". The first flights were uneventful as far as radio communications go. I could hear them and they could hear me. Not so much now. As far as what has changed.well, I have been building on this plane for years! Bill B _____ From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of jerb Sent: Wednesday, January 25, 2012 12:30 AM Subject: RE: AeroElectric-List: Re: Weak and Static on Transmission What kind of engine, if 2-stroke and using a voltage regular what brand is it, also what brand/model hand held radio are you using? I have almost the same identical problem. When I first flying my new home built airplane it was fine, crystal clear both transmission and receiving. However, something changed, now I can hardly understand transmissions. I haven't yet been able to put my finger on what's changed and causing it. jerryb At 09:51 AM 1/22/2012, you wrote: At 07:38 AM 1/20/2012, you wrote: Well, to further clarify this problem. I seem to be able to hear ok on the ground while taxiing around the airport, but after I leave the airport the reception gets really bad. At first I thought it was a problem with the approach frequency because that is where it would first start up. It was a loud hiss in the headphones so loud that I could not hear ATC. In fact, I have made two NORDO landings as a result on this loud hiss. I sent my radio back to have it checked out and nothing was found. All this trouble is at below 5000 ft and fine weather. I am flying off my 40 hours (22 so far) and am only flying in good weather. These radio problems at a Class C airport have made me afraid to fly. ATC could take some action against me if it continues. This is the first time I've been aware that you were having problems both with hearing and talking. While the ground listeners complain of "static" you have described the extraneous audio as a "hiss". We may be talking of two different problems. I'm having trouble resolving a single noise source that would manifest in both what you hear and what is transmitted to the ground. Get a hand-held transceiver and use it to 'probe' around the airplane. Use tune the hand-held to an unused frequency, open the squelch and open the volume to get a low level of no-signal hiss common to all receivers. Then probe around the panel mounted goodies and wire harnesses with the hand-held's antenna. See if the no-signal hiss changes in level with the master switch on versus off. If it does change, turn off accessories and/or pull breakers/fuses to see if any one accessory produces a noticeable change in noise from the hand-held. You can use the hand-held as an airborne signal quality sniffer too. Use a headset with the hand held to listen to your own transmitted signals. You may have to take the antenna off the hand-held to avoid overloading the hand-held receiver. You don't need to talk on the ship's radio, just listen to your transmitted signal to characterize the noise. Is it the same "hiss" you hear in your received signals? In any case, carry the hand held to avoid the no-radio return to the airport. In fact, having the 'three musketeers of dark-panel ops' in your flight bag is good insurance for any flights: www.aeroelectric.com/Pictures/Misc/Failure_Tolerance.pdf It was also suggested that you try a substitute antenna. I've fabricated test antennas that could be taped to the top or bottom surface of a wing and coax brought into the cockpit through the door gasket or some other pathway. But using the hand-held to characterize your transmitted and received signals personally takes ATC and others out of the loop. This is an especially good thing when they're unable/unwilling to join the discussion and offer their own observations/insights. Bob . . . AeroElectric-List Email Forum - http://www.matronics.com/Navigator?AeroElectric-List - MATRONICS WEB FORUMS - http://forums.matronics.com - List Contribution Web Site - -Matt Dralle, List Admin. http://www.matronics.com/contribution ________________________________ Message 9 _____________________________________ Time: 07:56:11 AM PST US From: John Grosse Subject: Re: AeroElectric-List: Larger D-Sub pins I searched for them a few years ago and had almost no success. The only source I found wanted $5 each. You could try getting them from Garmin through one of their approved avionics shops. John Grosse Stuart Hutchison wrote: > G'day all, > > Has anyone found a convenient after-market supplier for the D-Sub pins with > an oversize butt that Garmin include in some installation kits? The Garmin > part number is 336-00023-00 and they're physically longer with a larger > crimp cup to fit 18 AWG wire ... ________________________________ Message 10 ____________________________________ Time: 08:39:38 AM PST US From: "Stein Bruch" Subject: RE: AeroElectric-List: Larger D-Sub pins Most every shop has extras laying around because they almost never use all of them supplied. Gimme a call if you need a few. BTW, unless the runs are long an AWG20 wire will work fine in place of an AWG18. Cheers, Stein -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of John Grosse Sent: Wednesday, January 25, 2012 9:52 AM Subject: Re: AeroElectric-List: Larger D-Sub pins --> I searched for them a few years ago and had almost no success. The only source I found wanted $5 each. You could try getting them from Garmin through one of their approved avionics shops. John Grosse Stuart Hutchison wrote: > G'day all, > > Has anyone found a convenient after-market supplier for the D-Sub pins > with an oversize butt that Garmin include in some installation kits? > The Garmin part number is 336-00023-00 and they're physically longer > with a larger crimp cup to fit 18 AWG wire ... ________________________________ Message 11 ____________________________________ Time: 08:53:15 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Fuses instead of breakers At 10:33 PM 1/24/2012, you wrote: You could use a breaker for this particular circuit. I haven't thought about electronic ignitions specifically but I too like fuses over breakers. But convinced myself to use 4 breakers anyway, 2 for the 2 voltage regulators, 1 for the AP, and one for the flaps. Not sure I would have used all 4 now that I've flown it a bit but it made sense to me at the time. So I still have 2 dozen fuses... As long as your wiring is adequately protected then what you've installed is not "wrong" . . . just different. If the voltage regulators are fitted with crowbar ov protection, then panel mounted breakers are indicated. If you believe that the AP and flaps have failure modes for which you desire a crew driven mitigation, then in-reach breakers are also indicated. Some folks may find justification for debating the rationale for your design but the bottom line is this. What you've done does not increase risk. It MIGHT drive some small risk to a yet smaller value. But everybody hopes that you'll fly this airplane throughout it's useful lifetime never having encountered an urge to touch any of those breakers in flight. Bob . . . ________________________________ Message 12 ____________________________________ Time: 09:08:19 AM PST US From: John Grosse Subject: Re: AeroElectric-List: Larger D-Sub pins OBTW depending on the crimper you have, you may need a different positioner to crimp the special pins. Another option for your application might be to join your two wires into a "Y" either with a soldered joint or a pidg fastener then connecting the single end to your DB-X. It would be bulkier but easier. John Stein Bruch wrote: > --> AeroElectric-List message posted by: "Stein Bruch" > > Most every shop has extras laying around because they almost never use all > of them supplied. Gimme a call if you need a few. > > BTW, unless the runs are long an AWG20 wire will work fine in place of an > AWG18. > > Cheers, > > Stein ________________________________ Message 13 ____________________________________ Time: 09:08:24 AM PST US From: "Dennis Johnson" Subject: AeroElectric-List: Fuses instead of breakers Hi Jeff, Regarding what size fuse to use, I have a Lightspeed electronic ignition with a 5 amp fuse. In about 500 hours of flying, I've blown the fuse once. Don't know why it blew, and the engine kept running on the magneto. On the ground, I replaced the fuse and it's been fine since. Next time I have convenient access to the battery bus, I might put a 7.5 amp fuse instead. Dennis ________________________________ Message 14 ____________________________________ Time: 09:13:40 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Antenna Installation Question At 04:29 AM 1/25/2012, you wrote: I fly airplanes in the high flight levels and even there we use the top antenna primarily. I've thought about it before, and I think a "to scale" diagram would explain why. Even though 5-6 miles seems high by altitude standards, it's not very far laterally. If the rco or tower is 20 or even 100 miles away, the acute angle in the triangle is small. To visualize more easily, think of the distance in feet instead of miles. The angles are the same regardless of the units of course. If you stood 5 feet below your antenna's base and 100 feet away, would the antenna be visible? Likewise at 20 and even 5 feet, it is probably visible from most angles. If it is blocked by the wing or some other piece of airplane, then it will likely not be for long in flight. If the antenna's radiation angle were parallel with the ground plane, your analogy would be valid. The driving principal for this discussion is "radiation angle". See: http://www.hamradio.in/circuits/radiation_pattern.php The short story is that an ideal 1/4 wave radiator's angle of greatest sensitivity points up from the ground plane by some substantial angle. For many decades, ham radio operators have know that increasing the mechanical length of an antenna to 5/8 wavelength produces a much lower radiation angle. This antenna is NOT resonant at the frequency of operation. That deficiency is easily offset by a matching network at the base of the antenna. Antennas that long on airplanes would raise some eyebrows if not elicit a few giggles/snickers. Nevertheless, radiation angle variations in performance between top and bottom mounted antennas can be demonstrated. Large aircraft flying at high altitudes will always get a stronger measured signal from the bottom mounted antenna for stations having approximately 45 degree depression angle below the plane of flight. However, given the line-of-sight performance of VHF/UHF communications, the loss of performance from a top mounted antenna may not be noticed from the pilot's seat. The telling test would be to make contact with a station that is barely readable on a top antenna and then compare quality of communication with a bottom mounted antenna. A friend of mine (who is also an electron herder/ ham radio operator) has flown many of the heavy iron birds. He has observed this effect many times. At the same time, he has noted that when parked at the gate, a top mounted antenna will talk to some ground facilities that are degraded for the bottom antenna when surrounded by jetways, baggage carts and fuel trucks. Bob . . . ________________________________ Message 15 ____________________________________ Time: 09:27:36 AM PST US From: Ed Holyoke Subject: Re: AeroElectric-List: Fuses instead of breakers Just one more thing to think about if you are doing this with a Lightspeed ignition. From what I've read, there is some sort of crowbar inside the ignition module to protect it from an overvoltage event. If a fuse is fitted and the crowbar kicks it, you'll not be able to reset it as easily as with a breaker - if you can reach the fuse at all. I've heard of at least one case where an airplane was brought down because it was wired differently than the installation instructions in that regard. Ed Holyoke On 1/25/2012 8:48 AM, Robert L. Nuckolls, III wrote: > > > At 10:33 PM 1/24/2012, you wrote: > > > You could use a breaker for this particular circuit. I haven't > thought about electronic ignitions specifically but I too like fuses > over breakers. But convinced myself to use 4 breakers anyway, 2 for > the 2 voltage regulators, 1 for the AP, and one for the flaps. Not > sure I would have used all 4 now that I've flown it a bit but it made > sense to me at the time. So I still have 2 dozen fuses... > > As long as your wiring is adequately protected then > what you've installed is not "wrong" . . . just different. > If the voltage regulators are fitted with crowbar > ov protection, then panel mounted breakers are > indicated. If you believe that the AP and flaps > have failure modes for which you desire a crew > driven mitigation, then in-reach breakers are also > indicated. Some folks may find justification for > debating the rationale for your design but the > bottom line is this. What you've done does not > increase risk. It MIGHT drive some small risk to > a yet smaller value. But everybody hopes that you'll > fly this airplane throughout it's useful lifetime > never having encountered an urge to touch any of > those breakers in flight. > > > Bob . . . > > ________________________________ Message 16 ____________________________________ Time: 09:29:00 AM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Larger D-Sub pins At 10:31 AM 1/25/2012, you wrote: > >Most every shop has extras laying around because they almost never use all >of them supplied. Gimme a call if you need a few. > >BTW, unless the runs are long an AWG20 wire will work fine in place of an >AWG18. You beat me to it my friend. I will also suggest that it's perfectly okay to peel a few strands out of the "too large" wire to get them all into the 20AWG crimp cup of a standard pin. You'll have to leave the bare strands exposed over a greater length because the insulation will not go down into the wire opening of the connector. Experiment with an extra pin and a chunk of wire to establish the new strip dimensions. When somebody calls for putting overweight wires into a d-sub connector, the design goal is to REDUCE WIRE PATHWAY IMPEDANCE. Putting the larger wire into the pin does not increase the pin's current handling ability. Hence my suggestion for peeling out extraneous strands is not a technically 'evil' thing to do in terms of the physics. It would have an immeasurable impact on design goals that called for the larger wire. I think this is preferable to the FAT pin. It adds no bulk to wiring immediately behind the connector and leaves less exposed conductor. However, pulling this trick in an ISO/FAA/PP driven TC aircraft shop would probably get you fired or at least a 'ding' in your employment record. Bob . . . ________________________________ Message 17 ____________________________________ Time: 09:47:44 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Instrument Earth Bus cable size >My question is: >What is the minimum size cable can I use from the copper tab on the >FRONT of the earth conduit tab (just behind the nose section) to the >instrument earth bus (approx 18-20 inches in length). I'm trying to >avoid using the very heavy welding cable. See VIEW -B- in this drawing: http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z15K1.pdf In your case, the 2AWG ground wire is a piece of copper tube. Your design does not call for a firewall ground bus so the engine ground strap goes right to the copper tube. Your design does not mention the use of a forward high-power ground bus so the battery (-) wire goes right to a tab on the copper tube. An instrument panel ground bus could be fabricated per http://aeroelectric.com/Pictures/Grounding/AVG_RA.jpg http://aeroelectric.com/Pictures/Grounding/Avionics_Bus_3.jpg Figure Z15 suggests that a parallel bundle of 5, 20AWG wires be run from the avionics ground to the tab on the end of your copper tube. Landing light and position lights could also ground to the bolt in the copper tube tab. If you're fabricating your own d-sub panel ground bus, you could solder a couple of 14AWG wires to the commoning conductor at the back of the connector. This is described in https://matronics.com/aeroelectric/Catalog/AEC/9031/IM9031-700A.pdf Bob . . . ________________________________ Message 18 ____________________________________ Time: 09:48:55 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Fuses instead of breakers >Next time I have convenient access to the battery bus, I might put a >7.5 amp fuse instead. Good idea. Bob . . . ________________________________ Message 19 ____________________________________ Time: 10:00:00 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Fuses instead of breakers At 11:24 AM 1/25/2012, you wrote: Just one more thing to think about if you are doing this with a Lightspeed ignition. From what I've read, there is some sort of crowbar inside the ignition module to protect it from an overvoltage event. If a fuse is fitted and the crowbar kicks it, you'll not be able to reset it as easily as with a breaker - if you can reach the fuse at all. I've heard of at least one case where an airplane was brought down because it was wired differently than the installation instructions in that regard. Can you elaborate on what you've read and give us sources? I'm unaware of any crowbar ov protection built into the LSE system. Is this called out in any of their published literature? I found this on the Lightspeed site: ------------------------ Electrical System Requirements All Plasma CDI systems can be used with 12 or 24 volt electrical systems. Input voltages above 35 volts or reversed polarity can cause system damage. For this reason it is mandatory that all aircraft using Plasma CD Ignitions are equipped with over-voltage protection in their alternator charging system(s). Over-voltage protection is a requirement for certified aircraft. Power connection must be directly to the battery terminals to avoid voltage spikes and electrical noise. Aluminum should never be used as an electrical conductor for the Plasma CDI. Use only the supplied aircraft quality stranded wire. Minimum supply voltage for starting is 6.5 Volts. Minimum operating voltage is 5.5 Volts. -------------------------- This statement argues against any built-in ov protection. At the same time, the very wide operating voltage for the system guarantees that a properly designed 14v system will NEVER offer a threat to the LSE system. I am presently participating in an analysis of cause and effect for simultaneous failure of dual LSE systems. Root cause for that event was a failure to craft a failure tolerant architecture . . . a design goal which is foundation for all efforts here on the AeroElectric-List. It's a certainty that no builder who participates here on the List will suffer such an event. Bob . . . ________________________________ Message 20 ____________________________________ Time: 02:11:14 PM PST US Subject: AeroElectric-List: Re: Instrument Earth Bus cable size From: "MikeDunlop" Many thanks to everyone. Very informative and helpful replies, I will be studying the resources. MikeD (U.K.) Read this topic online here: http://forums.matronics.com/viewtopic.php?p=364843#364843 ________________________________ Message 21 ____________________________________ Time: 02:29:53 PM PST US From: Jeff Page Subject: AeroElectric-List: Re: Fuses instead of breakers I appreciate everyone's comments regarding sizing fuses. The reference to the FARs regarding battery bus circuits was useful. My design doesn't exceed those specifications. Fortunately, with an amateur-built aircraft, no bureaucrat can claim that a 5A circuit protective device would be the size of both the fuse and the circuit breaker. So a 10A fuse will probably work reliably with a Lightspeed ignition. Thanks. How about another example ? The popular approach is to use a pullable breaker for the hydralic pump for the amphibious landing gear. If I use a switch and a fuse, what size fuse ? I appreciate that I can always install a bigger fuse if nuisance pops occur, but it seems more professional to do the initial design with a good idea that the correct fuse was chosen in the first place ;-) So, does this logic work ? The pressure switch deactivates the pump at 500psi, but there will likely be short term pressure spikes above that. So, pick 1000psi. The current versus pressure chart for the motor, shows 3A at 500psi and 5A at 1000psi, as well as 23A at 3000psi, which is probably almost stalling the motor. So assume a typical current of 3A and spikes of less than a half second to 10A. Since a 10A fuse should blow after 1 second with 12.5A, that should be sufficient to avoid a nuisance pop ? During that half second, I want full power to the motor, so I will use 10A for the gauge versus wire length calculation. To drop 5% power through wire resistance, that gives me 18' for 16AWG wire. I should be able to get to the pump and back in less than 18', so 16AWG should be sufficient. A 30 degree rise for 16AWG wire requires 19A, so I could safely upsize to a 15A or 20A fuse. With your experience, should I start with a 10A or 15A fuse and expect it not to nuisance trip ? Are there any other reasons why a pullable circuit breaker would be preferred for this situation ? Jeff Page Dream Aircraft Tundra #10 ________________________________ Message 22 ____________________________________ Time: 06:40:04 PM PST US Subject: AeroElectric-List: Re: Fuses instead of breakers From: "bcondrey" I'll second the earlier comment on LSE ignitions having a crowbar setup. I had initially installed fuses to power a dual Plasma III setup. During a discussion with Klaus he quickly took exception to this and told me verbally that they DID have a crowbar setup (but I did not get into a discussion with him about the triggering criteria). Since it's a pretty long wire run in an RV-10 from the standard battery location to where the ignition boxes are located, he recommended having 7.5 amp CBs on the panel and if I felt the need to protect the feeders (he didn't) from the batteries to use 10 amp CBs back there, guaranteeing that the 7.5s would be what tripped during whatever event trips the crowbar. His very clear preference is to simply run the shielded, #18 (I think) wire all the way back and direct connect to the battery. I couldn't in good conscience live with a pair of always hot, unprotected wires for a run of that long and replaced the fuses near the batteries with 10 amp CBs and put 7.5 amp CBs on the panel as he recommended. Above conversation took place with him about 3-4 years ago but I remember it very clearly. Bob C. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=364852#364852 ________________________________ Message 23 ____________________________________ Time: 06:52:31 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Fuses instead of breakers At 04:27 PM 1/25/2012, you wrote: I appreciate everyone's comments regarding sizing fuses. The reference to the FARs regarding battery bus circuits was useful. My design doesn't exceed those specifications. Fortunately, with an amateur-built aircraft, no bureaucrat can claim that a 5A circuit protective device would be the size of both the fuse and the circuit breaker. Who said anything about regulations? Just because it's in a holy-watered book doesn't mean it's not a valuable ingredient in a recipe for success. So a 10A fuse will probably work reliably with a Lightspeed ignition. Thanks. Absolutely. How about another example ? The popular approach is to use a pullable breaker for the hydraulic pump for the amphibious landing gear. If I use a switch and a fuse, what size fuse ? BIG and beefy . . . in fact for things like hydraulic pump motors you would consider ANL style current limiters. That's what we used on the Beech products. I appreciate that I can always install a bigger fuse if nuisance pops occur, but it seems more professional to do the initial design with a good idea that the correct fuse was chosen in the first place ;-) Absolutely!!!!! Which is why we have the List. There are fuses, then there are Fuses and then FUSES. Circuit breakers come in many flavors of operating speed too. The differences can be significant in crafting a trip-free system. Recall years back we discussed the fact that there are tens of thousands of TC aircraft flying with an alternator b-lead breaker designed to nuisance trip? 60A circuit breakers on 60A alternators. An alternator that will put out MORE than 60A under some conditions. So, does this logic work ? The pressure switch deactivates the pump at 500psi, but there will likely be short term pressure spikes above that. So, pick 1000psi. The current versus pressure chart for the motor, shows 3A at 500psi and 5A at 1000psi, as well as 23A at 3000psi, which is probably almost stalling the motor. So assume a typical current of 3A and spikes of less than a half second to 10A. Since a 10A fuse should blow after 1 second with 12.5A, that should be sufficient to avoid a nuisance pop ? Don't agonize over it. You're wanting to protect what size wire? Scratch that. Wire with 10 AWG and use an ANL35 or equal. 10AWG is plenty heavy and will reduce voltage drop in the system. It's the 10x inrush current of what is probably a PM motor that drives the selection of protection . . . During that half second, I want full power to the motor, so I will use 10A for the gauge versus wire length calculation. To drop 5% power through wire resistance, that gives me 18' for 16AWG wire. I should be able to get to the pump and back in less than 18', so 16AWG should be sufficient. I'd go with the 10AWG. If 23A and 5000 PSI is a data point, then its doubtful that the motor is anywhere near stall. I'll bet inrush is 2 to 3 times that amount. A 30 degree rise for 16AWG wire requires 19A, so I could safely upsize to a 15A or 20A fuse. With your experience, should I start with a 10A or 15A fuse and expect it not to nuisance trip ? Are there any other reasons why a pullable circuit breaker would be preferred for this situation ? What controls the pump motor . . . a contactor? Is it tailored for intermittent duty, hi-inrush service like a starter-contactor? Sticking of this device might pose an in-flight concern. However, if you have a dual path e-bus, you can kill the main bus and shut down a runaway pump motor while retaining the electro-whizzies needed for comfortable completion of flight. Your question goes to exactly the kind of exercise every electrical system benefits . . . failure mode effects analysis, "What if . . . and how do I deal with it as a maintenance event as opposed to an emergency?" If an FMEA calls for a second disconnect such as a pullable breaker, then by all means. Worrying about poorly considered failures tends to stack redundancy on top of redundancy. It drives up parts count, cost of ownership and adds to system complexity. Complexity makes the pilot's job more difficult and risky. Well considered FMEA tends to produce the elegant solution: Just enough hardware with minimum risk and simpler to operate. Bob . . . ________________________________ Message 24 ____________________________________ Time: 06:55:30 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Fuses instead of breakers >During a discussion with Klaus he quickly took exception to >this and told me verbally that they DID have a crowbar setup >(but I did not get into a discussion with him about the >triggering criteria). Hmmmm . . . I'll be seeing Klaus in the not too distant future. I'll inquire. Bob . . . ________________________________ Message 25 ____________________________________ Time: 07:51:22 PM PST US Subject: Re: AeroElectric-List: Re: Fuses instead of breakers From: "Jeff B." Bob, please do. In the meantime, for those of us just getting to wiring, would this be reasonable, or overkill? Battery Bus Input terminal (not fused) ---> Fusible Link ---> Panel Breaker ---> Switch ---> LSE box? I'm not sure how ground would best get there since Klaus calls out shielded wire and it might be a little bit of a run to the FW ground or battery ground. Thoughts? (Or am I overthinking this?) -Jeff- On Wed, Jan 25, 2012 at 7:52 PM, Robert L. Nuckolls, III < nuckolls.bob@aeroelectric.com> wrote: > nuckolls.bob@aeroelectric.com**> > > > During a discussion with Klaus he quickly took exception to >> this and told me verbally that they DID have a crowbar setup >> (but I did not get into a discussion with him about the >> triggering criteria). >> > > Hmmmm . . . I'll be seeing Klaus in the not too distant > future. I'll inquire. > > > Bob . . . > ________________________________ Message 26 ____________________________________ Time: 08:31:51 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Fuses instead of breakers At 09:47 PM 1/25/2012, you wrote: Bob, please do. In the meantime, for those of us just getting to wiring, would this be reasonable, or overkill? Battery Bus Input terminal (not fused) ---> Fusible Link ---> Panel Breaker ---> Switch ---> LSE box? At the moment, I see no reason to treat the LSE ignition system any differently than any similar system offered to the TC aircraft world. If based on what I know now, I'd go 10A fuse at the battery bus driving a 20AWG non-shielded wire to an ON/OFF switch on the panel and then to the ignition system. I'm not sure how ground would best get there since Klaus calls out shielded wire and it might be a little bit of a run to the FW ground or battery ground. Shielded wire for this application is completely unwarranted. There is no potential antagonist/ victim scenario which would capacitively couple into our out of the LSE product. Grounding of the LSE ignition module should be no more complex than to take a 20AWG wire to the firewall ground bus. Thoughts? (Or am I overthinking this?) I don't think so. Klaus worries about some things that are either insignificant or non existent. "Noise" on the bus is NOT mitigated by connecting to the battery. I think I explain this in the battery chapter of the book. Batteries are simply not filters of any small excursions of bus voltage at any frequency. This is precisely why DO-160 and Mil-STD-704 tell the TC aircraft designer to EXPECT certain kinds of noise on the ship's DC bus. See: http://www.aeroelectric.com/Pictures/Curves/MSTD704_28V_Noise.jpg That flat top in the plot between 1 and 5 Khz is 1 volt RMS or about 3 volts peak to peak on a 28 volt system. Cut those numbers in half on a 14 volt system. The amplitude for expected noise falls off on either side . . . but the point is, NOTHING . . . especially the battery will mitigate this noise. Hence the admonition, "It's there son, learn to live with it." Indeed we who have run the gauntlet on qualification for TC aircraft have learned to live with it . . . in face, it's such a benign stress that "dealing with it" is not even much of a technically intellectual exercise. It makes no sense to build crowbar ov protection into a product when it's so easy to build passive shutdown protection. I did this little fast-disconnect switch to qualify an automotive seat warmer onto a 28v aircraft. http://aeroelectric.com/Pictures/Schematics/80v_Surge_Protection.jpg this circuit simply 'disconnects' the vulnerable device from the bus during the transient and reconnects when the event is over. But more important is the fact that in a 14 volt airplane, the maximum alternator-runaway event is limited to 20 volts . . . which is well inside the LSE's NORMAL operating voltage. Finally, you could treat a robust feeder from battery to ignition system just like a fat feeder to the e-bus. It might look something like this: http://aeroelectric.com/Pictures/Schematics/Battery_Feed_for_Ignition.pdf This satisfies the design goals for crash safety by having a pilot operated disconnect at the battery. The relay only draws about 100 mA so it's not a big budget energy consumer for battery only operations. Modern relays are quite reliable . . . and this one gets pre-flight tested. Point is there's a lot of ways to skin cats-of- legitimate-worry. The task is to separate real worries from bogus worries. Bob . . . ------------------------------------------------------------------------------------- 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.