Originally Posted by
island_airphoto
FYI - if ice plugs the pitot tube quick enough to trap the air in there, the speed may not go down. If the airplane gains altitude the "speed" goes UP because the difference between the trapped pitot and static air gets bigger.
Could this phenomena triggers the high speed protection (in an ALT mode without alpha prot.) creating a diverging / self amplifying control loop (small NU input => hiher alt. => higher spd => high spd prot. => higher nose up => even higher alt. => even higher spd, whereas it is the opposite in reality) with a skyrocketing altitude out of the flight enveloppe ? (a moderate NU input would translate as an ever increasing altitude)
If the high vertical speeds put forward are derived from radar data measured at range limit (just before the track is lost), meaning derived from noisy altitude measurements at low SNR, are they reliable ?