I subscribe to the Bob N school of thought that an alternator
failure shouldn't ruin your day or prevent you from going to your
intended destination.

Shannon,

 

I never read that Mr. Nuckolls supported "finishing" the flight after losing critical electrical gear.  I have always found it interesting that some folks focus on completing the trip rather than more easily accepting a premature stop to repair a problem.  It is especially interesting to see that, when a well designed system with a backup both fail, some are willing to rely on the "last reserve item" to finish the trip.

 

I, too, have an essential bus system, but configured quite differently than yours because the objective is to land as soon as possible after some major problem and because it is for a much simpler LNC2.  For example, when under IFR, what are the things I need to get on the ground?  The essential electrical list only contains gear locked lights, cold cathode panel lights, AOA, turn coordinator, air data computer, engine instruments, comm1, nav1, gps and xpdr.  I can further shed loads in reverse order up the list.  Notice that flaps, gear, fuel pumps, secondary radios, A/P, trim, etc., are not on the list. 

 

If only the alternator failed and sufficient battery power remains, I can always turn the master switch back on to utilize some of the main bus items.  Also note that my fuel system always keeps my header tank at greater than 8 gallons -- certainly enough to get to the ground within 30 minutes. 

 

If the failure was major problem on the main bus, I don't necessarily "need" anything on that bus to get to the ground.  Hmmmm, perhaps Pitot Heat should be moved to the Essential Bus although that could definitely hasten my need for speed to the ground.

 

Because of my philosophy, my backups are only one level deep.  For example, the autopilot with its electric gyro is the backup for the vacuum system during IFR operations.  Let me illustrate this with a real life experience -- flying IFR stormy weather from Ogden, Utah to Chicago, I lost the use of the A/P (although not the electric turn coordinator) and thus decided to land at nearby Casper, Wyoming and get it fixed rather than solely rely on the vacuum system or, after it's loss, my partial panel skills to finish the trip.  BTW, the failure was an A/P internal fuse and it was repaired overnight allowing me to confidently re-enter the lingering bad weather.

 

 

PS, I never figure myself as a useful backup for anything.