As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT, AIRSPEED SUDDENLY INDICATED 30 KTS HIGHER THAN WHAT WAS REAL. UPPER MODES OF THE AUTO PILOT WOULD NOT FUNCTION AND A "DECOUPLE" LIGHT CAME ON ON THE CAD. ALSO, UNTIL ADC NR 2 WAS TURNED OFF, THE HIGH NR MODE WOULD NOT WORK. THE NORMAL PROCEDURE IS TO SWITCH THE ADC TO NR 1 AND HAVE PROPER AIRSPEED INDICATION. AFTER DOING SO, ACFT WAS LANDED AT HELIPAD WITHOUT ANY PROBLEM AND HIGH NR RESTORED THEN MX WAS CONTACTED.