Originally Posted by [URL="http://www.pprune.org/members/302559-clippedcub"
ClippedCub[/URL]]Three pitots is double redundant, at best.
1. lose one, down to two - 1st level of redundancy, and singly redundant if you exclude human interaction.
2. IF one of the remainder disagree, the pilot chooses which one he likes - 2nd redundancy level, but only due to human interaction.
3. Lose the last one, no backup. System is doubly redundant.
That is not strictly true. The level of redundancy is a count of the available resources, not the number you can afford to lose. Where you have three sensors, i.e. three pitot sensors, all of them are redundant, i.e. none of them are essential on their own for the system to work, therefore you have triple redundancy. It would take three failures for a triple redundant system to become inoperative.