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txpilot
Joined: 26 Feb 2007
Posts: 87
Location: Houston, TX
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 Posted: Fri Nov 09, 2007 8:34 pm Post subject: Avionics Master Switch: To install, or not to install |
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I'm currently working on my electrical system using Bob Nuckoll's 'Aeroelectric Design' book as a guide. This book is an excellent resource, but I'm not sure about his suggestion not to install an avionics master switch. He claims it causes more problems than it solves because the switch itself can be a single point of failure for all avionics.
He also says modern avionics are robust enough to take voltage fluctuations and therefore don't need an AMS. I'm planning on installing relatively old technology radios: KX-155, KT-76A and a standard sigtronics intercom.
Any thoughts? What's everyone else doing? BTW - I'm not intending on installing a secondary AMS. This is a day VFR only airplane and I'm trying to keep it simple.
Thanks,
Dan Ginty
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Gig Giacona
Joined: 10 Jan 2006
Posts: 1416
Location: El Dorado Arkansas USA
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| Posted: Fri Nov 09, 2007 11:21 pm Post subject: Re: Avionics Master Switch: To install, or not to install |
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All I can say is I've never flown and aircraft that had an electrical system that didn't have one. That doesn't make it right but...
| txpilot wrote: | I'm currently working on my electrical system using Bob Nuckoll's 'Aeroelectric Design' book as a guide. This book is an excellent resource, but I'm not sure about his suggestion not to install an avionics master switch. He claims it causes more problems than it solves because the switch itself can be a single point of failure for all avionics.
He also says modern avionics are robust enough to take voltage fluctuations and therefore don't need an AMS. I'm planning on installing relatively old technology radios: KX-155, KT-76A and a standard sigtronics intercom.
Any thoughts? What's everyone else doing? BTW - I'm not intending on installing a secondary AMS. This is a day VFR only airplane and I'm trying to keep it simple.
Thanks,
Dan Ginty |
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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W.R. "Gig" Giacona
601XL Under Construction
See my progress at www.peoamerica.net/N601WR |
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jetboy
Joined: 22 Jul 2006
Posts: 233
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| Posted: Sat Nov 10, 2007 12:11 am Post subject: Re: Avionics Master Switch: To install, or not to install |
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I went with simple, no avionics master, and I never bother turning the stuff I normally run (KY97a) on or off either. That just wears out the controls. I have run this same radio in 2 planes over the last 15 years, no problems. It was in a C150A with the pull starter and generator, no avionics master, not even the 'dump the radios while the keyswitch is cranking' facility.
Those 'older' radios are compliant to DOD 160, something that some of the newer round hole mount types seem to be lacking. You can tell the cheap ones by the messages on their websites about "must install after avionics master and xx,000 uF capacitor" The problem with these is they actually have no physical switch of their own, and the electronic switch is 'susceptible', so this class of device does benefit from a separate switch.
I'm with Bob's philosophy here, and if things go bad on a murky day you really just want to fly the airplane without getting mixed up in complicated systems that lead to more troubles than you started with. Sorry it doesnt make for a very impressive cockpit, bit like when I got into a Piper Cub after training in C172's and literally wondered if I could safely fly this machine because it lacked almost every item that I thought was needed for the journey. And it didnt have an avionics master.
Ralph
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Ralph - CH701 / 2200a |
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ashontz
Joined: 27 Dec 2006
Posts: 723
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| Posted: Mon Nov 12, 2007 7:37 am Post subject: Re: Avionics Master Switch: To install, or not to install |
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I belive it's a good idea to turn off the avionocs before turning on or off the engine due to possible electrical spikes from what I remember. They should be protected, but even so. Plus, let's say you forgot to shut off one of the instruments, or say the fuel tank level gauge or another such instrument like a temperature gauge, that's still drawing power albeit a little bit, like leaving a your dome light on in the car, well, not as serious of a draw of current, but still. Come back 3 weeks later to fly and you're battery could be seriously drained.
do not archive
| txpilot wrote: | I'm currently working on my electrical system using Bob Nuckoll's 'Aeroelectric Design' book as a guide. This book is an excellent resource, but I'm not sure about his suggestion not to install an avionics master switch. He claims it causes more problems than it solves because the switch itself can be a single point of failure for all avionics.
He also says modern avionics are robust enough to take voltage fluctuations and therefore don't need an AMS. I'm planning on installing relatively old technology radios: KX-155, KT-76A and a standard sigtronics intercom.
Any thoughts? What's everyone else doing? BTW - I'm not intending on installing a secondary AMS. This is a day VFR only airplane and I'm trying to keep it simple.
Thanks,
Dan Ginty |
| | - The Matronics Zenith-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith-List |
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ashontz
Joined: 27 Dec 2006
Posts: 723
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| Posted: Mon Nov 12, 2007 7:44 am Post subject: Re: Avionics Master Switch: To install, or not to install |
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Actually, if anything it may may the installation cleaner, you have everything going back to a common terminal strip anyway, I would hope anyway, not a big deal to just add a switch to that whole terminal strip. Or how about if you're doing maintenance later in and around one of those instruments, instead of disconnecting the whole battery you can just flip the switch off and be able to work around the instruments without worrying about shorting something out. Plus you can add a breaker to the whole terminal block that services the instruments. Seems like a "best practices" thing to me to add a master switch.
When I get to the point of doing my instrument panel I'd like the whole thing to be able to just slide out and have the terminal block and everything on a tray along with the instruments, that way I can install all the instruments on my work bench and then just slide the tray in and connected one or two wiring harnesses. Nothing beats clean installations. Make it easier to work on for sure.
do not archive.
| jetboy wrote: | I went with simple, no avionics master, and I never bother turning the stuff I normally run (KY97a) on or off either. That just wears out the controls. I have run this same radio in 2 planes over the last 15 years, no problems. It was in a C150A with the pull starter and generator, no avionics master, not even the 'dump the radios while the keyswitch is cranking' facility.
Those 'older' radios are compliant to DOD 160, something that some of the newer round hole mount types seem to be lacking. You can tell the cheap ones by the messages on their websites about "must install after avionics master and xx,000 uF capacitor" The problem with these is they actually have no physical switch of their own, and the electronic switch is 'susceptible', so this class of device does benefit from a separate switch.
I'm with Bob's philosophy here, and if things go bad on a murky day you really just want to fly the airplane without getting mixed up in complicated systems that lead to more troubles than you started with. Sorry it doesnt make for a very impressive cockpit, bit like when I got into a Piper Cub after training in C172's and literally wondered if I could safely fly this machine because it lacked almost every item that I thought was needed for the journey. And it didnt have an avionics master.
Ralph |
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http://www.matronics.com/Navigator?Zenith-List |
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