Marshall asks:

<<When this occurred, did you get any error warning displayed on your screen?  With your understanding of the Chelton system, are there failure modes which are not annunciated?>>

When this happened I was testing a "discount" AHRS to see if it could be used in place of the X-Bow  system for the low end systems. A design flaw in the electronics caused the 5 volt supply in the AHRS to brown out at low temperatures. The roll event was preceded by an "Attitude Failure" display and aural warning and when the AHRS rebooted it started rolling.  Chelton does not use this AHRS. A confidentiality agreement precludes me from saying who was the manufacturer but I have heard that they fixed the problem.

There are cases where a sensor can transmit seemingly valid but incorrect data, pitot ice for example, that may not be immediately enunciated. This is true for ANY system and is why standby gauges are a good idea. Chelton is about to receive Level A certification (the highest level) for their certified software. The Chelton software has extensive cross checking and data range checking as well as numerous hardware watchdogs to keep bugs out.  They even have protection from Gamma Ray induced RAM memory errors. Is it perfect? Hell no, it is designed and built by humans after all,  but it is the best system available.

As PIC just remember the first rule of Naval Aviation "Everyone is trying to kill me." and you will do just fine.

Regards
Brent Regan