GTX327

[az_gila]

Originally Posted by RV7Guy

I am a huge proponent of safety and minimizing risk by taking reasonable steps to eliminate "points of failure."

There seems to be a general hysteria on many lists and forums about the concern over various component failures especially in the area of switches. However on the same forums you rarely, if ever, hear of these actually occuring. Redundancy this and that, also adds to the complexity and to the opportunity for something else to fail.

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If I were to be concerned about switch failures I be just as concerned about the Master switch failing along with the Radio Master since they are acuated virtually the same number of times. Neither seem to be an issue.

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Great discussion.

Darwin, I agree about your comment on complexity, and adding more stuff to allow for failures. My personal observation is the IFR pilot/builders are the most guilty of this, adding extra equipment to allow for other equipment to fail....

However, following AeroElectric Bob's bus architecture adds little complexity. Using his generic light aircraft example here...

http://www.aeroelectric.com/PPS/Adob..._Pdfs/Z11K.pdf

The only extra "stuff" added is a diode and an alternate feed switch, and splitting a single power bus into 3 smaller busses. Very little extra complexity, with a definite payoff.

You will notice that the Alternate Bus feed comes directly off the battery, so if there is a Master Switch failure, or a Battery Contactor failure (more likely), you will have enough electronics able to be powered to make a safe landing at a nearby airport, as opposed to a complete electrical failure, and loss of all electronics.

As a member of the Grumman Gang mailing list, I see regular postings on switch and contactor failures, and some pilots even carry extra switches in their travel tool kit. They are cheap switches though....

The AeroElectric sample diagrams are worth their weight in gold, and if implemented really do not add to the system complexity, but give good redundancy to make a safe landing, even if not at the intended destination. Sounds like a good safety system to me.

I don't know what redundancy and/or safety measures are built into the EXP Buss.... do you know of any?

gil in Tucson - I think we have less electrical problems here in AZ due to a lack of corrosion effects.... This doesn't remove mechanical type problems, such as vibration though...

[RV7Guy]

Hi Gil,

I guess I have it then with the EXP Buss. Not only is it wired with the battery, but a back up battery as well. The only problem would be if the entire panel took a shiite. Not likely since it is protected with the poly fuses.

I'd probably use Bob's system or something quite similar if doing it again.

[az_gila]

Originally Posted by RV7Guy

Hi Gil,

I guess I have it then with the EXP Buss. Not only is it wired with the battery, but a back up battery as well. The only problem would be if the entire panel took a shiite. Not likely since it is protected with the poly fuses.

I'd probably use Bob's system or something quite similar if doing it again.

Darwin... sounds like the back-up battery is the built-in redundancy.... should be OK.

I'm retiring soon (17 more work days, but who's counting... ...) and sounds like there could be a market for a pre-built panel that implements the AeroElectric system.....hmmmm...

gil in Tucson - the RV-6A is #1 on the honey-do list...

[Jekyll]

The endurance bus (ala Nuckolls) not only provides a 2nd path to glory for your electrons but, it also creates the endurance mode by performing 2 critical functions when faced with "alternation interuptus" it allows rapid reconfiguration (flip 1 switch) to power only those systems you consider to be critical to safe continuance of flight and it takes the battery conntactor, and its 1 amp of draw, out of the load.

It takes all of 10-15 seconds to turn on the individual radios however, the single avionics master can take down your whole system and you know Murphy.....

Jekyll

[Bob Brown]

FWIW, in the last 12 years I have had one failed battery master and one failed avionics master. I now subscribe to the Nuckolls "endurance" bus philosophy and wired my RV7A accordingly. YMMV

[az_gila]

Originally Posted by Bob Brown

FWIW, in the last 12 years I have had one failed battery master and one failed avionics master. I now subscribe to the Nuckolls "endurance" bus philosophy and wired my RV7A accordingly. YMMV

Bob... was that the "master switch" or the "master solenoid"??

gil in Tucson

[Bob Brown]

Gil, I had the battery master switch fail in my '79 182 last year, the avionics master switch failed in flight the year before that. Now that plane is sold and gone to the warm moist coastal air of Florida to live out the rest of its life...and I'm FREEEE of Spam.