I've tried to explain this before but it's been pretty negatively received. The assumption that safety critical systems on jet aircraft have triple redundancy is a misconception. At least in so far as any kind of automated, transparent to the pilot, monitoring and switching.
For example, the front of the 737 does have 3 pitot tubes. However, these drive the air data computers for the pilot and the copilot positions. The 3rd one drives a small set of backup instruments. A fourth at the rear of the plane is an input to the hydraulic pitch and feel computer. The Airbus is closer to what some might imagine but the switch between the 3 data sources is still manual (AF447 might have reached Paris if this wasn't the case).
There is another argument that adding more AoA sensors would have had a negligible impact on safety given they are exposed to the same environmental conditions. The main outcome was limiting the authority of the system, it would have prevented both accidents.
For example, the front of the 737 does have 3 pitot tubes. However, these drive the air data computers for the pilot and the copilot positions. The 3rd one drives a small set of backup instruments. A fourth at the rear of the plane is an input to the hydraulic pitch and feel computer. The Airbus is closer to what some might imagine but the switch between the 3 data sources is still manual (AF447 might have reached Paris if this wasn't the case).
There is another argument that adding more AoA sensors would have had a negligible impact on safety given they are exposed to the same environmental conditions. The main outcome was limiting the authority of the system, it would have prevented both accidents.