Narrative:

We encountered a challenge with our flight management computer on our departure climbout. When cleared out of 14;000 ft; our altitude selector display on the mode control panel got stuck and displayed '50;000' while we were trying to set it to the new ATC assigned altitude. However; we determined that we could continue to our destination since we were able to manually maintain any chosen altitude. We advised departure of our situation and expressed concerns about rvsm. The controller checked and informed us that we were cleared to continue to our destination in rvsm airspace since we were able to maintain altitude. We also advised company dispatch and maintenance. We endured the aural altitude alert which chimed every 10 seconds. We asked if we could pull the circuit breaker to silence it; but maintenance would not allow it. Although vertical navigation mode worked in cruise; as expected; when we initiated our descent we lost numerous vertical navigation mode capabilities. These included normal descent planning tools such as the following: 1. V-nav path; 2. The top of descent symbol (T/D) on the navigation display unit; 3. The altitude range arc on the navigation display unit; and 4. The waypoint/altitude vertical bearing display guidance on the CDU unit v-nav descent page. We descended using vertical/speed; our lowest mode of automation. We leveled off at flight level 340 as requested by center. About 60 miles out they asked us to cross a fix on the arrival at 12;000 ft and 250 KTS. We calculated incorrectly and started down at 35 miles away from our crossing fix. This caused us to cross around 10;000 ft too high. Although we informed approach control he did not respond but cleared us down to 6;000 ft. Near the end of our descent; at around 14;000 ft; the challenge disappeared and we were able to accomplish a stable uneventful approach and landing. To prevent such an error in the future I would: 1. Silence the altitude alerter; 2. Review calculation of 3 degree manual descent profiles.

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Original NASA ASRS Text

Title: When the altitude alert display stuck at 50;000 FT on initial climbout the flight crew of a B737-700 decided to continue the flight using FMS cruise altitude programming to maintain altitude in cruise and utilizing Vertical Speed Mode for the descent. When given a crossing altitude restriction on their descent they miscalculated the required Top of Descent point and crossed the restricted fix 10;000 FT high.

Narrative: We encountered a challenge with our Flight Management Computer on our departure climbout. When cleared out of 14;000 FT; our ALTITUDE SELECTOR DISPLAY on the MODE CONTROL PANEL got stuck and displayed '50;000' while we were trying to set it to the new ATC assigned altitude. However; we determined that we could continue to our destination since we were able to manually maintain any chosen altitude. We advised Departure of our situation and expressed concerns about RVSM. The Controller checked and informed us that we were cleared to continue to our destination in RVSM airspace since we were able to maintain altitude. We also advised Company Dispatch and Maintenance. We endured the aural ALTITUDE ALERT which chimed every 10 seconds. We asked if we could pull the CIRCUIT BREAKER to silence it; but Maintenance would not allow it. Although VERTICAL NAVIGATION MODE worked in cruise; as expected; when we initiated our descent we lost numerous VERTICAL NAVIGATION MODE capabilities. These included normal descent planning tools such as the following: 1. V-NAV path; 2. The Top of Descent symbol (T/D) on the NAV display unit; 3. The Altitude Range Arc on the NAV display unit; and 4. The WAYPOINT/ALTITUDE VERTICAL BEARING display guidance on the CDU unit V-NAV descent page. We descended using VERTICAL/SPEED; our lowest mode of automation. We leveled off at Flight Level 340 as requested by Center. About 60 miles out they asked us to cross a fix on the arrival at 12;000 FT and 250 KTS. We calculated incorrectly and started down at 35 miles away from our crossing fix. This caused us to cross around 10;000 FT too high. Although we informed Approach Control he did not respond but cleared us down to 6;000 FT. Near the end of our descent; at around 14;000 FT; the challenge disappeared and we were able to accomplish a stable uneventful approach and landing. To prevent such an error in the future I would: 1. Silence the Altitude Alerter; 2. Review calculation of 3 degree manual descent profiles.

Data retrieved from NASA's ASRS site as of July 2013 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.