[freddie]

In my readings on this forum regarding electrical systems, I gather that one benefit of the Essential/Endurance bus is that it would provide an alternate source of power were the master contactor to fail.

Question: How could a master contactor fail mechanically?

 

[Harold Lanfear]

I don't know, but

I've had it happen. It was on the ground and I had no power to start. Apparently, a wire burned off somewhere, but I don't know that for a fact as we didn't analyze it we didn't analyze it, just changed the contactor and flew home. Of course, I beat the mechanic - he had a 65 mile drive

 

[f1rocket]

Good question and I don't think they fail that often, but they are an electro-mechanical device and all mechanical devices fail eventually. I suspect that acrobatics may assist in getting the plunger to stick, spring to break, contacts to arc, or coil wires to fail.

If getting around a failed contactor was your ONLY reason for considering an E-bus, then I wouldn't bother with it.

 

[chaskuss]

You are mis-understanding the purpose of the Essential Bus

In my readings on this forum regarding electrical systems, I gather that one benefit of the Essential/Endurance bus is that it would provide an alternate source of power were the master contactor to fail.

Question: How could a master contactor fail mechanically?

Freddie,
The REAL purpose of an essential bus is to provide an alternate power path after an ALTERNATOR failure. Such a failure would require the pilot to shed all but essential electrical loads to ensure safe continuation of the flight for the maximum possible time. IFR flight, or flight over water or rough terrain are situations when this would be desirable.
The idea of the essential bus is to allow the pilot to simply shut down the master contactor to shed unwanted loads. On a "properly" designed electrical system, this will shed all non essential electrical loads (for cruise flight) with the flip of a single switch. The idea is to ease pilot workload during a stressful situation (loss of alternator).

Charlie Kuss

 

[freddie]

I really appreciate these responses. It seems like I won't need an essential bus setup since I will only fly day/VFR and will be running one mag. I am also using a B&C alternator, which hopefully, has greater reliability. And I will have pullable fuses to shut things off individually.