Hi
Daves point which I think is being slightly lost here is that we should always consider reinforcing the potential weak links in our aeroplanes. Batteries are a well known weak link especially the airborne pack because of the environemnt it lives in and the continuing varying current it has to deliver. Batteries prefer a steady current drain not spikes. Which is why Tx batteries generally last longer than Rx batteries.

Going down the route of multiple redundant systems is a choice the individual has to make based on the plane,the investmentand the risk. We have a saying in the Nuclear Industry ALARP. As Low As Reasonably Practical and that I beleive is what Dave is suggesting. We should always consider ALARP when cosnidering the weak links in the system. No system can be made 100% bullet proof but we can at least minimise the risk which I believe is the point is the Dave was trying to put over.

Redundacy always comes at a cost, increased complexity, increased weight or something else and this also has to be considered.

Even a dual battery system still depends on a potential single point of failure ( eg the change over mechanism) . Normally the potetial single point failure has a far higher ( several orders of magnitude) reliablity than the devices it is changing over.

In my profession I live by risk and redundancy otherwise things get very nasty very quickly. I use the same principal in my Jets. My Exocet has a single RX but dual batteries. Mainly because we couldn't shoe horn a Weatronix in the fuselage. My next jet will have both dual rx and dual battieries. God forbid it still suffers a failure than at least I will know I have done all I can and I have suffered the one in a million. ( then throw myself on the mercy of the wife).

I await the flak.

Mike