Narrative:

Operating flight cvg-atu, cruising at FL310. Captain's leg. His airspeed started fluctuating wildly. The high speed warning ticker went off constantly. He reduced power to stop the warning. At one point, his read 400 KTS, mine read 260 KTS. The altitude tape also fluctuated. I notified ATC quickly to let them know our altitude and airspeed were inaccurate. Told them it was an air data attitude/heading refer system problem. A few mins later we got a TA to climb. The RA said climb and we did. Saw aircraft about 4-5 mi away and 1000 ft vertical. We never made abrupt changes to avoid the other aircraft. We probably fluctuated 300-400 ft off our altitude of FL310, our best guess. By this time the captain's airspeed and altitude tape disappeared. The standby altitude at FL310 normally reads 300- 400 ft high. We went through the QRH and figured out the problem was the air data computer. Switched to air data #2. We began our descent to atw, and landed uneventfully. Called maintenance and ATC by the phone number they gave us en route. ATC was concerned about the other aircraft. It was not a close call. That seemed to be her main concern. He said the same thing may happen on the next leg or 3 months from now, or maybe never. Maintenance came out to the aircraft. A write-up was entered in the book.

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Original NASA ASRS Text

Title: A CL65 FLC LOSES THE #1 AIR DATA COMPUTER. WHILE SORTING OUT THE PROB THE TCASII RA CREATES THE NEED OF AN ALTDEV FOR THE CREW.

Narrative: OPERATING FLT CVG-ATU, CRUISING AT FL310. CAPT'S LEG. HIS AIRSPD STARTED FLUCTUATING WILDLY. THE HIGH SPD WARNING TICKER WENT OFF CONSTANTLY. HE REDUCED PWR TO STOP THE WARNING. AT ONE POINT, HIS READ 400 KTS, MINE READ 260 KTS. THE ALT TAPE ALSO FLUCTUATED. I NOTIFIED ATC QUICKLY TO LET THEM KNOW OUR ALT AND AIRSPD WERE INACCURATE. TOLD THEM IT WAS AN AIR DATA ATTITUDE/HDG REFER SYS PROB. A FEW MINS LATER WE GOT A TA TO CLB. THE RA SAID CLB AND WE DID. SAW ACFT ABOUT 4-5 MI AWAY AND 1000 FT VERT. WE NEVER MADE ABRUPT CHANGES TO AVOID THE OTHER ACFT. WE PROBABLY FLUCTUATED 300-400 FT OFF OUR ALT OF FL310, OUR BEST GUESS. BY THIS TIME THE CAPT'S AIRSPD AND ALT TAPE DISAPPEARED. THE STANDBY ALT AT FL310 NORMALLY READS 300- 400 FT HIGH. WE WENT THROUGH THE QRH AND FIGURED OUT THE PROB WAS THE AIR DATA COMPUTER. SWITCHED TO AIR DATA #2. WE BEGAN OUR DSCNT TO ATW, AND LANDED UNEVENTFULLY. CALLED MAINT AND ATC BY THE PHONE NUMBER THEY GAVE US ENRTE. ATC WAS CONCERNED ABOUT THE OTHER ACFT. IT WAS NOT A CLOSE CALL. THAT SEEMED TO BE HER MAIN CONCERN. HE SAID THE SAME THING MAY HAPPEN ON THE NEXT LEG OR 3 MONTHS FROM NOW, OR MAYBE NEVER. MAINT CAME OUT TO THE ACFT. A WRITE-UP WAS ENTERED IN THE BOOK.

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.