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CE550 maintaining FL250 checking charts for direct routing, aircraft began a climb resulting in deviation from altitude of 450 ft. Center queried and returned aircraft to FL250.
| Attributes | |
| ACN | 349080 |
| Time | |
| Date | 199610 |
| Day | Sat |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : ewc |
| State Reference | PA |
| Altitude | msl bound lower : 25000 msl bound upper : 25450 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zob |
| Operator | general aviation : corporate |
| Make Model Name | Citation II S2/Bravo |
| Operating Under FAR Part | Part 91 |
| Navigation In Use | Other |
| Flight Phase | cruise other |
| Route In Use | enroute : direct |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | Other |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 100 flight time total : 12000 flight time type : 2000 |
| ASRS Report | 349080 |
| Person 2 | |
| Affiliation | Other |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 100 flight time total : 6000 flight time type : 3000 |
| ASRS Report | 349137 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : far non adherence : clearance |
| Independent Detector | other controllera other flight crewa |
| Resolutory Action | flight crew : returned to intended course or assigned course |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
After leveling off at FL250, autoplt was engaged. All indications were normal. The pilot flying the aircraft asked me to see if center would clear us direct to VOR near our destination (spa VOR). I stated I don't believe the route would be that much shorter and proceeded to get the en route chart out to check. We were both looking at the chart. After a short time (about a min), noticed altitude was high. I looked down and noticed autoplt altitude hold had become disengaged. The pilot then took over manually and returned aircraft to proper altitude. Neither of us could figure out what caused the autoplt to disengage. The contributing factor was that, for a short period of time, neither of us were monitoring our flight instruments. As a result, we got approximately 450 ft off our altitude before we realized there was a problem. We have had autoplt problems before so should have been more alert that this could possibly happen. Supplemental information from acn 349137: at FL250 and 360 KTS, autoplt was knocked off accidentally. Pilots were looking at maps and did not catch it until ATC questioned altitude at FL254. Autoplt pitch trim wheel is extremely sensitive. Maintenance has been working on it.
Original NASA ASRS Text
Title: CE550 MAINTAINING FL250 CHKING CHARTS FOR DIRECT ROUTING, ACFT BEGAN A CLB RESULTING IN DEV FROM ALT OF 450 FT. CTR QUERIED AND RETURNED ACFT TO FL250.
Narrative: AFTER LEVELING OFF AT FL250, AUTOPLT WAS ENGAGED. ALL INDICATIONS WERE NORMAL. THE PLT FLYING THE ACFT ASKED ME TO SEE IF CTR WOULD CLR US DIRECT TO VOR NEAR OUR DEST (SPA VOR). I STATED I DON'T BELIEVE THE RTE WOULD BE THAT MUCH SHORTER AND PROCEEDED TO GET THE ENRTE CHART OUT TO CHK. WE WERE BOTH LOOKING AT THE CHART. AFTER A SHORT TIME (ABOUT A MIN), NOTICED ALT WAS HIGH. I LOOKED DOWN AND NOTICED AUTOPLT ALT HOLD HAD BECOME DISENGAGED. THE PLT THEN TOOK OVER MANUALLY AND RETURNED ACFT TO PROPER ALT. NEITHER OF US COULD FIGURE OUT WHAT CAUSED THE AUTOPLT TO DISENGAGE. THE CONTRIBUTING FACTOR WAS THAT, FOR A SHORT PERIOD OF TIME, NEITHER OF US WERE MONITORING OUR FLT INSTS. AS A RESULT, WE GOT APPROX 450 FT OFF OUR ALT BEFORE WE REALIZED THERE WAS A PROB. WE HAVE HAD AUTOPLT PROBS BEFORE SO SHOULD HAVE BEEN MORE ALERT THAT THIS COULD POSSIBLY HAPPEN. SUPPLEMENTAL INFO FROM ACN 349137: AT FL250 AND 360 KTS, AUTOPLT WAS KNOCKED OFF ACCIDENTALLY. PLTS WERE LOOKING AT MAPS AND DID NOT CATCH IT UNTIL ATC QUESTIONED ALT AT FL254. AUTOPLT PITCH TRIM WHEEL IS EXTREMELY SENSITIVE. MAINT HAS BEEN WORKING ON IT.
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.