Hamid writes --

 

<<What you are saying is that in a system with multiple alternator/batteries and isolated/redundant busses, a TSO's system and a non-TSO's system can equally survive an adverse event like a lightning induced power surge or an alternator caused voltage surge. I would strongly disagree with your conclusion.>>

Actually I agree completely with Hamid.  Environmental effects such as the indirect effects of lightning are precisely where the TSO'd units have an advantage.  With my electrical power example I was trying to say that there are other failure modes (loss of electrical power for a variety of reasons) where the TSO'd unit goes dark just like the non-TSOd unit.

 

I did envision electrical power surges due to failures in the electrical system causing the non-TSOd unit to fail which the TSOd unit might survive.  In this case, Hamid is right -- the TSOd unit has an advantage here as well.  The lesson is that problems with the fairly mundane portion of our avionics systems (electrical power generation and distribution) can also cause failures of our whiz-bang EFISs and glass panel displays.  It doesn't take a lightning strike.

 

- Rob Wolf

Steam gauges in my airplane!