AeroElectric-List Digest Archive

Mon 01/26/15


Total Messages Posted: 7



Today's Message Index:
----------------------
 
     1. 03:24 AM - Re: Dual Alternator, Dual Battery, Single Bus (Dan Brown)
     2. 07:40 AM - Rotax 912iS data (Robert L. Nuckolls, III)
     3. 10:20 AM - Re: Dual Alternator, Dual Battery, Single Bus (user9253)
     4. 10:47 AM - Re: Dual Alternator, Dual Battery, Single Bus (user9253)
     5. 01:21 PM - Re: Re: Dual Alternator, Dual Battery, Single Bus (Dan Brown)
     6. 08:09 PM - Re: Re: Dual Alternator, Dual Battery, Single Bus (Robert L. Nuckolls, III)
     7. 08:37 PM - Re: Re: Dual Alternator, Dual Battery, Single Bus (ARGOLDMAN@aol.com)
 
 
 


Message 1


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    Time: 03:24:08 AM PST US
    From: "Dan Brown" <dbrown2@nycap.rr.com>
    Subject: Re: Dual Alternator, Dual Battery, Single Bus
    Thanks Bob, > As long as you don't have 250w incanescant landing lights > or an electro-hydraulic pump system, transient loads > capable of stalling a self-excited alternator don't > exist. Further, since you're running dual batteries, > you'd have to crap two contactors to set that scenario > up. I do have an electro-hydraulic pump for the landing gear but I get your point about the two battery contactors. I will make sure I do a contactor check during run-up to ensure that I am not flying around with one of them failed. > What does your power distribution look like. What electro-whizzies > from which which busses? I am still working on that but basically its electronic ignition, fuel pump, clock and system memories, cabin lighting and 12v outlets split between the two battery buses and everything else on the main bus. The last time I tried to estimate the total load I came up with about 40 amps with everything I plan to equip my plane with on at the same time. If my estimate is correct I could probably run my full suite of goodies with the 30 amp aux alternator. If I find that my system want much more than 30 amps during normal cruise will install a contactor that cuts the power to non-essential equipment and reduces the load to <30 amps. This brings up another question. I already have a contactor, that I have named avionics contactor, conveniently locate by the power bus. Traditionally I believe its intent was to turn off all the sensitive and expensive avionics during engine startup and such to protect them from power spikes or surges. At least that's what I was told. I was also more recently told that modern avionics, with their internal protection, do not need such isolation. If that is the case I would like to use my avionics contactor as the non-essential equipment switch cited above. Is it true that the avionics switch is a thing of the past? Thanks again, Dan


    Message 2


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    Time: 07:40:15 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Rotax 912iS data
    At 20:41 2015-01-25, you wrote: > >The Rotax fuel injected engine is new, only having been for sale for >the last year or two. It is an electrically dependent engine, not >only for the ignition, but also for the high pressure fuel >pumps. Thus, the electrical system needs to be fail safe. Below is >an excerpt from the installation manual. >http://www.flyrotax.com/customer-serviceImpressum/technical-publications.aspx >Joe Thanks for the heads-up on this page! I was aware of the new engine and spent some time looking for MM/IM data . . . every offer I found last night wanted to sell me the book. I've downloaded the manual and will spend some time with it today. Bob . . .


    Message 3


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    Time: 10:20:48 AM PST US
    Subject: Re: Dual Alternator, Dual Battery, Single Bus
    From: "user9253" <fransew@gmail.com>
    > Is it true that the avionics switch is a thing of the past? Here is a quote from SkyView Pilots User Guide - Revision Q > SkyViews robust power protection allows it to be powered on during engine start. And here is a quote from the Dynon D-180 user guide: > It is acceptable to have the FlightDEK-D180 turned on during engine start. My RV-12 does have an avionics switch, but only because I had to build the plane exactly per the plans in order to register it as E-LSA. But I never shut it off, even during engine start. The Garmin SL-40 and GTX-327 and GPS496 and Dynon D-180 all still work fine. I probably should exercise the avionics switch occasionally to remove corrosion on the contacts. An avionics switch is a single point of failure. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=437665#437665


    Message 4


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    Time: 10:47:41 AM PST US
    Subject: Re: Dual Alternator, Dual Battery, Single Bus
    From: "user9253" <fransew@gmail.com>
    Here is link to Bob Nuckolls article about the avionics master switch. http://www.aeroelectric.com/articles/avmaster.pdf -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=437666#437666


    Message 5


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    Time: 01:21:21 PM PST US
    From: "Dan Brown" <dbrown2@nycap.rr.com>
    Subject: Re: Dual Alternator, Dual Battery, Single Bus
    Thanks Joe, That article rings of a familiar tone. Maybe that where "I was also more recently told that modern avionics, with their internal protection, do not need such isolation." Dan -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of user9253 Sent: Monday, January 26, 2015 1:47 PM Subject: AeroElectric-List: Re: Dual Alternator, Dual Battery, Single Bus Here is link to Bob Nuckolls article about the avionics master switch. http://www.aeroelectric.com/articles/avmaster.pdf -------- Joe Gores


    Message 6


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    Time: 08:09:58 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Dual Alternator, Dual Battery, Single Bus
    At 15:20 2015-01-26, you wrote: > >Thanks Joe, >That article rings of a familiar tone. Maybe that where "I was also more >recently told that modern avionics, with their internal protection, do not >need such isolation." >Dan Actually, the av master was borne on a compelling but flawed premise . . . About 1966, when transistors were starting to show up in aircraft radios (pnp germanium with 30v ratings) Cessna (and I suspect others . . . don't know for sure but I was at Cessna) were experiencing a rash of radio failures in new, ready-to-deliver airplanes . . . . . .and yes . . . it seems that radios left ON during engine start were the most affected. It was surmised that a 'spike' from the starter got 'em. It stood to good reason. That starter thingy draws hundreds of amps, was very inductive . . . it HAD to be a potential source of inductive 'kick back' deleterious to those relatively fragile. The Avionics Master was borne . . . and yes . . . the failures went away. In retrospect, it was not an inductive 'spike' that got the radios but brownout. The 'Airplane Patch' east of the plant would park hundreds of airplanes waiting for delivery . . . none of which had guaranteed battery integrity . . . a 6v sag to the 14v radio during a starter 'grunt' was the most likely cause. Further, while DO-160 (and its predecessors DO-138 and DO-108) was definitely around, it was not as rigorous with respect to bus voltage aberrations. In years since, solid state devices have become very robust in that they are designed to EXPECT the very abuse that rolled a NavCom 300 T.U. in 1967. By the time yours truly was designing transistors into airplanes in the 1975 time frame, the idea that I would want to 'take it off the bus' during an engine start was rather humorous . . . the industry had learned how to live in the vehicular DC power environment. It was no big deal . . . yet the seeds of concern for 'spiking' a radio persisted as did the avionics master switch. Bob . . . Bob . . .


    Message 7


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    Time: 08:37:59 PM PST US
    From: ARGOLDMAN@aol.com
    Subject: Re: Dual Alternator, Dual Battery, Single Bus
    The below not withstanding, Dynon recommends starting and stopping the engine with the /Skyview not connected to the ships buss. They recommend starting the engine on the skyview backup battery so that you can see the engine instruments and connecting to the ships power after start. What do they know that we don't? Rich In a message dated 1/26/2015 10:11:07 P.M. Central Standard Time, nuckolls.bob@aeroelectric.com writes: --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com> At 15:20 2015-01-26, you wrote: <dbrown2@nycap.rr.com> > >Thanks Joe, >That article rings of a familiar tone. Maybe that where "I was also more >recently told that modern avionics, with their internal protection, do not >need such isolation." >Dan Actually, the av master was borne on a compelling but flawed premise . . . About 1966, when transistors were starting to show up in aircraft radios (pnp germanium with 30v ratings) Cessna (and I suspect others . . . don't know for sure but I was at Cessna) were experiencing a rash of radio failures in new, ready-to-deliver airplanes . . . . . .and yes . . . it seems that radios left ON during engine start were the most affected. It was surmised that a 'spike' from the starter got 'em. It stood to good reason. That starter thingy draws hundreds of amps, was very inductive . . . it HAD to be a potential source of inductive 'kick back' deleterious to those relatively fragile. The Avionics Master was borne . . . and yes . . . the failures went away. In retrospect, it was not an inductive 'spike' that got the radios but brownout. The 'Airplane Patch' east of the plant would park hundreds of airplanes waiting for delivery . . . none of which had guaranteed battery integrity . . . a 6v sag to the 14v radio during a starter 'grunt' was the most likely cause. Further, while DO-160 (and its predecessors DO-138 and DO-108) was definitely around, it was not as rigorous with respect to bus voltage aberrations. In years since, solid state devices have become very robust in that they are designed to EXPECT the very abuse that rolled a NavCom 300 T.U. in 1967. By the time yours truly was designing transistors into airplanes in the 1975 time frame, the idea that I would want to 'take it off the bus' during an engine start was rather humorous . . . the industry had learned how to live in the vehicular DC power environment. It was no big deal . . . yet the seeds of concern for 'spiking' a radio persisted as did the avionics master switch. Bob . . . Bob . . .




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