Narrative:

Flight from rdu to dca. After clearance to cross ric at FL220, aircraft was level at FL220 with autoplt #1 selected on. Received clearance to cross ojaay (irons 3 arrival, dca) at 10000 ft, 250 KTS. This was entered in the FMC and in the autoplt MCP. 'Profile' was selected on the MCP. The aircraft entered an uncommanded climb, the autoplt was disengaged and a hand-flown descent was initiated. Altitude deviation was +500 ft (FL225). After the descent was under control, the #1 FMS showed approximately 1200 ft below the profile and the #2 FMS showed 800 ft above profile. #2 FMS was determined to be correct and the #2 autoplt was engaged. Remainder of flight was uneventful. The FMS was written up upon arrival at dca. An air safety report was filed with our company, and an altitude awareness program incident data form was also filed.

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Original NASA ASRS Text

Title: F100 ACFT WITH DSCNT CLRNC, FLC ENTERED DATA INTO FMS AND WHEN PROFILE WAS SELECTED IN THE MCP, THE ACFT IMMEDIATELY WENT INTO A CLB. FLC DISCONNECTED THE AUTOPLT AND RETURNED TO PROFILE USING THE #2 FMS.

Narrative: FLT FROM RDU TO DCA. AFTER CLRNC TO CROSS RIC AT FL220, ACFT WAS LEVEL AT FL220 WITH AUTOPLT #1 SELECTED ON. RECEIVED CLRNC TO CROSS OJAAY (IRONS 3 ARR, DCA) AT 10000 FT, 250 KTS. THIS WAS ENTERED IN THE FMC AND IN THE AUTOPLT MCP. 'PROFILE' WAS SELECTED ON THE MCP. THE ACFT ENTERED AN UNCOMMANDED CLB, THE AUTOPLT WAS DISENGAGED AND A HAND-FLOWN DSCNT WAS INITIATED. ALTDEV WAS +500 FT (FL225). AFTER THE DSCNT WAS UNDER CTL, THE #1 FMS SHOWED APPROX 1200 FT BELOW THE PROFILE AND THE #2 FMS SHOWED 800 FT ABOVE PROFILE. #2 FMS WAS DETERMINED TO BE CORRECT AND THE #2 AUTOPLT WAS ENGAGED. REMAINDER OF FLT WAS UNEVENTFUL. THE FMS WAS WRITTEN UP UPON ARR AT DCA. AN AIR SAFETY RPT WAS FILED WITH OUR COMPANY, AND AN ALT AWARENESS PROGRAM INCIDENT DATA FORM WAS ALSO FILED.

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.