Avionics Master Switch Brand

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luftkul

Filing Flight Plan
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luftkul
Is there a preferred quality Avionics master switch for a certified plane - in this case Grumman Traveler - that never had one from the factory? Getting some avionics upgrades done and doing some research.

Is rocker/paddle or toggle style better? Should you have a cover or bump protection on the avionics master?
 
Some planes have a switch and a relay. Others have a switching breaker (25-35A depending on the load) that feeds the avionics bus. The later is the easiest way, and you shouldn't need to shield that switching breaker. The P&B W31 is the most common switching breaker I see.
 
luftkul said:
Is there a preferred quality Avionics master switch for a certified plane - in this case Grumman Traveler - that never had one from the factory? Getting some avionics upgrades done and doing some research.

Is rocker/paddle or toggle style better? Should you have a cover or bump protection on the avionics master?
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Are you replacing the fuses with breakers? If so, how about using breakers that look like toggle switches and avoid the avionics master switch entirely? When it's time to turn on/off your radios, just fan your hand over all of them at once.
acb-7270-b.jpg

https://www.aircraftspruce.com/catalog/elpages/7270_5_20.php
 
Thanks Jesse!

It's all adding up, but we're on the slippery slope to empty bank accounts. I think we are going to replace the old fuses with Klixon 7277 series breakers.
 
luftkul said:
Is there a preferred quality Avionics master switch for a certified plane - in this case Grumman Traveler - that never had one from the factory?
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An alternate route is to look at various other aircraft avionics set-ups and copy/buy the same switches, etc. for your aircraft. For a better bang-for-your buck you can also look into the salvage yards and see if they'll let you buy/remove a whole power panel. If you go this route keep an eye out for certain helicopters as their power panels (CBs/switches) are convenient to remove with just a several dzus and a couple harnesses to cut.
luftkul said:
Is rocker/paddle or toggle style better?
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FYI: It usually depends on space whether you can use a rocker switch.
luftkul said:
Should you have a cover or bump protection on the avionics master?
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Usually not in my experience.
 
asicer said:
Flipping them in sequence looks impressive to passengers.:)
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With that in mind, one can just use the individual switches on each unit. I decided on that approach for my RV10 and use fuses for wire protection. Individually turning each unit on at startup and doing the reverse during shut down is part of my flow. There are arguments for doing or not doing an avionics master independent of space and cost but I’ve forgotten them.

My EFISs are unstitched; if the plane is on, they are on. Still not sure if that was the right approach but it’s been that way for 10 years and I like it.


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Bill Watson said:
here are arguments for doing or not doing an avionics master independent of space and cost but I’ve forgotten them.
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FYI: the main benefit of a separate avionics master is to isolate/protect the equipment during the engine start voltage drops. Older equipment was more sensitive to these drops and could be damaged over time. The current stuff has a greater tolerance of voltage swings but it is still recommended to keep avionics isolated during engine starting. Some aircraft will even de-energize the avionics buss when the start circuit is energized.
 
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Here's my Warrior II's CB panel. Note the Avionics Master switch upper right. Looks like a simple toggle. Interestingly, the POH makes no mention of an Avionics Master switch, though there are many mentions of the Master Switch. In normal procedures, there are line items such as,
Radios ................................. OFF
All electrical equipment ........... OFF
Circuit.Breaker.Panel.1024.jpg
 
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Bell206 said:
FYI: the main benefit of a separate avionics master is to isolate/protect the equipment during the engine start voltage drops. Older equipment was more sensitive to these drops and could be damaged over time. The current stuff has a greater tolerance of voltage swings but it is still recommended to keep avionics isolated during engine starting. Some aircraft will even de-energize the avionics buss when the start circuit is energized.
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Thanks. I’m very aware of that reasoning but using each unit’s power switch accomplishes the same. Yes, the current stuff has, by TSO, greater tolerance. One argument against an avionics master is the creation of a single point of failure.

With that said, the one set of units that have no discreet on/off switch on my panel are experimental GRT EFISs. Initially I found they could be corrupted if power was interrupted/dropped during their boot process. I reported the problem and it was fixed about 7 years ago. I like having the EFISs on at all times with redundant power sources since they are in effect my Artificial Horizon. I’ve done everything possible to avoid having anything power them down short of turning the plane master off.


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Bill Watson said:
I’ve done everything possible to avoid having anything power them down short of turning the plane master off.
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Except you still have the same argument of a single point of failure. One method to reduce that is to create an essential buss that feeds direct off the battery. A number of aircraft use this method, especially IFR types. So your only failure point then becomes a broken wire or your battery is dead. However, I'd still recommend a separate switch for all avionics. But if switch failure is still an issue for you then you can install dual switches that will each provide power if the other fails.
 
Bell206 said:
Except you still have the same argument of a single point of failure. One method to reduce that is to create an essential buss that feeds direct off the battery. A number of aircraft use this method, especially IFR types. So your only failure point then becomes a broken wire or your battery is dead. However, I'd still recommend a separate switch for all avionics. But if switch failure is still an issue for you then you can install dual switches that will each provide power if the other fails.
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Rather than an essential bus, I have a dual bus, dual alt, dual battery setup. I cross-feed them for TO & Landing but run them separately in flight so any failures become evident.

I’m running 3 GRT EFISs, all capable of all functions. They are all powered through multiple connections to a single bus that can be cross fed. I’ve eliminated all other backup batteries in order to remove additional battery maintenance requirements (a bad backup battery can be worse than not having one). It’s a bit much for a single engine plane but easy to do on an experimental. Turns out to be simple to operate in normal or in response to a failure.

Easy to maintain as well. Major electrical system components are serviced or replaced on condition-only since no single component, even a battery, is essential to flight completion. A high confidence situation when flying somewhere like the Bahamas.


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