Narrative:

In level flight air data computer began to make mach/IAS, ivsi and altimeter erratic +/-800 ft, +/-.2 mach, +/-1000 FPM. Aircraft never left altitude per copilot side instrument which were working normal. Removed and replaced air data computer and aircraft is functioning normally. I flew the aircraft manually to eliminate altitude excursions that the aircraft would have done had autoplt been connected. ATC asked our altitude which was reported at FL330, where we were according to accurate copilot instrument.

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Original NASA ASRS Text

Title: A LIGHT 2 TURBOJET TRANSPORT ON START OF DSCNT AT FL330 EXPERIENCED THE L AIR DATA COMPUTER FAILURE WITH ASSOCIATED INSTS.

Narrative: IN LEVEL FLT AIR DATA COMPUTER BEGAN TO MAKE MACH/IAS, IVSI AND ALTIMETER ERRATIC +/-800 FT, +/-.2 MACH, +/-1000 FPM. ACFT NEVER LEFT ALT PER COPLT SIDE INST WHICH WERE WORKING NORMAL. REMOVED AND REPLACED AIR DATA COMPUTER AND ACFT IS FUNCTIONING NORMALLY. I FLEW THE ACFT MANUALLY TO ELIMINATE ALT EXCURSIONS THAT THE ACFT WOULD HAVE DONE HAD AUTOPLT BEEN CONNECTED. ATC ASKED OUR ALT WHICH WAS RPTED AT FL330, WHERE WE WERE ACCORDING TO ACCURATE COPLT INST.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.