SoarngTheSkies;
The 767, however, has three independent pitot systems, right? (two for the CPT/FO PFDs and one feeding the Backup). So while a sinlge pitot/static, if it fails without any backup, will create a major issue, having three of them will always render the failed one a minority.
Yes, correct but not easily discerned in all cases - sometimes one must switch pitot-static sources manually. In our case, the PF's airspeed was increasing while mine (the PNF) was decreasing as he "tried to keep the speed below VMO", 340kts I think, anyway it was close to red-lining. I called out my airspeed which was by then around 220kts (climbing through 240 or so). We compared both CAS's with the Standby and decided mine was correct so I took control. Interestinlgy, the altimeters were not affected. The system recovered on approach at the other end, in warmer air. We had a number of EICAS messages regarding the rudder limiter and something about aileron control but no overspeed warning when the PF's CAS exceeded VMO.
The same would apply in the 320/340 series I think but again, pitot-static sources may have to be selected - I'd have to examine the books.
In that case it's at least rather trivial to determine that they are in disagreement and thus not trustworthy. If you then also look at altitude trends from the barometric altimeter, you'd again be able to rule out the faulty one.
Precisely. And today, given the installation and a few moments to bring up the appropriate FMC page, one can use the GPS altitude and groundspeed to keep things perhaps not to the foot or knot, at least within the nominal.
This is a very, very sad accident among sad accidents.