Originally Posted by
groundbum
if the instruments were displaying faulty data because of blocked pitot tubes/dodgy connections/et al, wouldn't it follow that the FDR data will also be suspect?
It's certainly possible that those FDR parameters whcih are derived from pitot/static measurement might be suspect. However, the FDR records at least 88 parameters, whcih include geographic position and acceleration in all 3 axes, whcih are completely independent of any pitot/static errors whcih might have been occurring. If you have independent position and acceleration data, it becomes a pretty simple task to determine if the recorded altitude and airspeed information is in error.