Backup Speed Scale
My outfit has retrofitted all 330/340 machines with Backup Speed Scale function. In a nutshell, if unsure which ADR(s) is/are faulty, switch them all off and- voila! Keep the "speed" out of red by using power and attitude (note: two red bands, one above, one below the speed reference line on speed tape). Altitude displayed is derived from GPS.
I'm just curious whether this particular MSN had the same retrofit done or not.