As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ENROUTE, THE PILOTS ALTIMETER FLAGGED AND OVERSPEED HORN TRIGGERED. THE ADC BEGAN TO WORK AGAIN AT THE END OF THE FLIGHT. THE ADC WAS FOUND TO BE DEFECTIVE AND REPLACED. THE SYSTEM WAS TESTED AND INSPECTED AND FOUND TO COMPLY WITH FAR 91-411, PART 43 AND TO REMAIN RVSM COMPLIANT. THERE HAS BEEN 2 PRIOR REPORTED FAILURES OF ADC`S IN THIS AIRCRAFT DATED MAY 6, 2005 AND NOV 21, 2005. (K)