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Flight crew of a B737-300 climbed above assigned altitude due to the autoplt altitude hold mode disconnecting due to higher than cruise power setting.
| Attributes | |
| ACN | 408150 |
| Time | |
| Date | 199807 |
| Day | Sun |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : das |
| State Reference | TX |
| Altitude | msl bound lower : 28000 msl bound upper : 29000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zhu tower : atl |
| Operator | common carrier : air carrier |
| Make Model Name | B737-300 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other |
| Route In Use | enroute airway : zhu |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : flight engineer pilot : commercial pilot : cfi pilot : atp pilot : instrument |
| Experience | flight time last 90 days : 172 flight time total : 9667 flight time type : 2589 |
| ASRS Report | 408150 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : clearance |
| Independent Detector | other controllera |
| Resolutory Action | flight crew : returned to intended course or assigned course other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
We were at FL280 with discretion to FL240 and at an assigned speed of 280 KTS. ZHU changed our speed to 300 KTS. I increased our airspeed to 300 KTS by means of the mode control panel. During all of the speed changes, the captain and myself were having a discussion on converting centigrade temperature to fahrenheit temperature. After a while the controller asked about our altitude. The aircraft had begun a slow climb from FL280 to FL290. The captain and myself had a long discussion on this incident. We think that when I increased the airspeed the engines accelerated the aircraft to the point that the autoplt could not keep up with the acceleration. The pitch mode of the autoplt disconnected and it began a slow climb. Since we were in a cruise portion of flight we missed the aircraft was in a climb. In addition to climb and descent leveloffs, I will watch speed changes to make sure we don't go through on altitude.
Original NASA ASRS Text
Title: FLC OF A B737-300 CLBED ABOVE ASSIGNED ALT DUE TO THE AUTOPLT ALT HOLD MODE DISCONNECTING DUE TO HIGHER THAN CRUISE PWR SETTING.
Narrative: WE WERE AT FL280 WITH DISCRETION TO FL240 AND AT AN ASSIGNED SPD OF 280 KTS. ZHU CHANGED OUR SPD TO 300 KTS. I INCREASED OUR AIRSPD TO 300 KTS BY MEANS OF THE MODE CTL PANEL. DURING ALL OF THE SPD CHANGES, THE CAPT AND MYSELF WERE HAVING A DISCUSSION ON CONVERTING CENTIGRADE TEMP TO FAHRENHEIT TEMP. AFTER A WHILE THE CTLR ASKED ABOUT OUR ALT. THE ACFT HAD BEGUN A SLOW CLB FROM FL280 TO FL290. THE CAPT AND MYSELF HAD A LONG DISCUSSION ON THIS INCIDENT. WE THINK THAT WHEN I INCREASED THE AIRSPD THE ENGS ACCELERATED THE ACFT TO THE POINT THAT THE AUTOPLT COULD NOT KEEP UP WITH THE ACCELERATION. THE PITCH MODE OF THE AUTOPLT DISCONNECTED AND IT BEGAN A SLOW CLB. SINCE WE WERE IN A CRUISE PORTION OF FLT WE MISSED THE ACFT WAS IN A CLB. IN ADDITION TO CLB AND DSCNT LEVELOFFS, I WILL WATCH SPD CHANGES TO MAKE SURE WE DON'T GO THROUGH ON ALT.
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.