<<Modern electronic EFIS systems properly installed with backup batteries and internal automatic isolation circuitry are about as fail-proof as a single piece of electronic equipment can get.>>

 

This is not Brent's statement.  Rather, this relates to a suggestion that non-TSOd units should be considered equally reliable as TSOd units, which is something that Brent disagrees with.

 

I think Brent is saying that a device that has successfully passes environmental qualification testing (a TSOd unit) is way less likely to fail than a unit which has not.  His first-hand experience taking an experimental system through this process (Sieera Flight Systems, now Chelton) bears this out.  Such units are most likely more resilient to power fluctuation, temperature extremes, shock and vibration, and even exposure to water.  In this sense, the TSOd unit is more reliable.

 

Having said that, no electronic unit will work without power.  Now you look at internal backup batteries, redundant power sources, multiple generators/alternators, duplicate paths for power, no single point failures, and perhaps other things which are totally separate from the unit itself.  In this sense, the non-TSOd unit and the TSOd unit are equally reliable.

 

Just my two cents...

 

- Rob Wolf

 

p.s. I'm using a vacuum pump and steam gauges.  I don't need no stinkin' electricity.... (But then, if the weather is really bad -- like it's raining -- I stay on the ground.  YMMV)