SODPUD RVDT
- ASI errors = Static blocked, ASI overread in a descent - Pitot Blocked, ASI underread in a descent
I actually had a pitot blockage once and what happened was that the airspeed drops to zero. Theres drain holes in the pitot tube sides for moisture so the pitot line effectively goes to ambient meaning the airspeed drops to zero. A bit sporting when pitch based speed hold was engaged on the AP and we nosed over!