[USNBandit]

I remember that the news reported right after the accident that the FAA had active TDs out on that type of aircraft for the instruments, but I couldn't remember if it was the indicator itself or the pumps.

[expatpat]

I'd guess the pump. It would be interesting to know if the two AI's each had separate vacuum pumps or if both ran off the same pump, with the other as backup for the first pump. Maybe CN18F knows.