woodpecker
WRT the SAARU on the 777, this was a mandated device the FAA made them installl as they did not trust honywells 1 in 3 billion chance of an undetected ADIRU failure.
Its input is AVERAGED with the ADIRU .. if the SAARU had been on MEL the Malasian 777 would have attempted to fly backwards,
SAARU was a cheap device using teh same FOG type RLG's as the ISFD (Boeing for ISIS) consequently they failed a lot.
New SAARUS have the SAME RLG's as the ADRIUS now. & we are back to a 1 in 3 billion chance.. Guess Malaysian got lucky
so on that aircraft You had the SAARU the Adiru & the ISFD.
If it lost the probe data you would be in a similar scenario. Does the ICE Detector work well on the A330?