Scott and Jeff,

 

I think you misunderstand my intentions.  This exericise is purely a design one.  I said that I thought the system should be designed in such a way that you COULD continue flight if you wanted….notice I never said you SHOULD or that I would.  I guess I should have added that disclaimer.  I thought my comment about both alternators failing and how rare that would be would suffice to show that, but I guess not.  Sorry for the confusion.

 

I have heard Bob say more than once that any piece of electrical failing shouldn’t ruin your day and that you should be able to continue on to your destination if you chose.

 

Let me assure you that if both alternators failed at the same time, I’m landing ASAP.  However, I feel the system should be designed (or overdesigned if you will) so that it will allow flight to continue.

 

Jeff, for all the spam cans out there you are correct, as they aren’t designed like Bob’s Z14 (or my slightly modified Z14).  However, what part of what I have said makes for an “unairworthy electrical system”?  If it is properly designed, I hold that there is nothing about it that is unairworthly.  If a short exists in the line from the alternator to the crossfeed contactor and distribution buss on the firewall, the ANL current limiter will blow.  If there is a short in the field wire, the circuit breaker will pop.  This is true for both alternators.  That’s all there is….what else could go wrong with an alternator and how is it not protected?  An alternator failing hardly makes my electrical system unairworthly.  I hold that even both alternators failing (with a properly designed system with a crossfeed and a way to shed loads or an essential buss) would not make my electrical system unairworthly.  It is designed to be airworthy for the next 3 hours, so I haven’t nor wouldn’t break any rules.

 

I’m in NO way suggesting that if 2 alternators fail to keep flying, that’s crazy.  All I’m saying is that a system should be designed and all the different scenarios should be included in the analysis and design, including the worst case scenario of both alternators failing.  My comment is about exercising your brain during the design phase to really understand your system and its limitations and what it is capable of and to design it (over design probably) to meet and exceed all possible scenarios and all your expectations…..and, to develop your own personal limitations about what you are comfortable with.

 

My own comfort level is that if one alternator fails, I’m flying on to my intended destination and maybe even back home so I can fix it where I have my own tools and parts and trust the people that will be working on it (me).  This is the exact scenario that Ron Brice demonstrated on our way to the San Jose fly-in….one of his alternators failed coming out of Vegas, yet because he had a properly designed system that he knew and understood and was comfortable with, he flew on to our fuel stop, and then on again into San Jose.  He then fixed it there where there were tools and people in the know that he trusted.  Now, if both alternators fail, I’m landing ASAP….BUT, I have the confidence in my system to know that I have 3 hours of endurance on my essential buss if I have to stretch it past 30 minutes to get to VFR or to a decent approach I’m comfortable with.  I know I have this reserve….I guess my question to you guys would be do you know?  My whole point to my post was that I feel its something you should know.