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BE60 pilot reports autopilot pitch up on engagement and difficulties flying aircraft after disengagement. Emergency declared and successful return to departure airport.
| Attributes | |
| ACN | 758558 |
| Time | |
| Date | 200710 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : zzz.airport |
| State Reference | US |
| Altitude | msl single value : 4000 |
| Environment | |
| Flight Conditions | IMC |
| Weather Elements | Rain Fog Turbulence |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zzz.artcc |
| Operator | general aviation : personal |
| Make Model Name | Duke 60 |
| Operating Under FAR Part | Part 91 |
| Flight Phase | climbout : intermediate altitude |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | other |
| Function | flight crew : single pilot |
| Qualification | pilot : multi engine pilot : private |
| Experience | flight time last 90 days : 40 flight time total : 900 flight time type : 100 |
| ASRS Report | 758558 |
| Events | |
| Anomaly | aircraft equipment problem : critical altitude deviation : excursion from assigned altitude inflight encounter : turbulence inflight encounter : weather other anomaly |
| Independent Detector | other flight crewa |
| Resolutory Action | controller : issued new clearance flight crew : declared emergency flight crew : regained aircraft control |
| Consequence | other |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
Narrative:
At assigned cruise altitude; I pressed the altitude hold button on autoplt. The autoplt commanded a very sharp pitch up; I disengaged the autoplt and stopped the climb. The autoplt disengaged but I believe the clutches on the servos did not release; due to very heavy control forces during incident. Due to the control forces and IMC conditions; control of aircraft was momentarily in question. I asked for and received clearance from center to return to ZZZ due to deteriorating WX at destination. Upon completion of turn and stabilization of airplane I tried to relieve the control pressures by activating the pitch coordinator and the aircraft went into an uncommanded climb again. I disengaged and momentarily control was in question again; and this time I busted IFR altitude assignment; I declared an emergency with approach. I was granted; and I completed an ugly but successful GPS approach into ZZZ and returned aircraft for autoplt repair. Callback conversation with reporter revealed the following information: maintenance found that the barometric altitude sensor had failed causing the initial pitch up and a loose wire prevented the autopilot from being disengaged. The reporter was able to overpower the autopilot but the experience was very disconcerting in IMC.
Original NASA ASRS Text
Title: BE60 PILOT REPORTS AUTOPILOT PITCH UP ON ENGAGEMENT AND DIFFICULTIES FLYING ACFT AFTER DISENGAGEMENT. EMERGENCY DECLARED AND SUCCESSFUL RETURN TO DEPARTURE ARPT.
Narrative: AT ASSIGNED CRUISE ALT; I PRESSED THE ALT HOLD BUTTON ON AUTOPLT. THE AUTOPLT COMMANDED A VERY SHARP PITCH UP; I DISENGAGED THE AUTOPLT AND STOPPED THE CLB. THE AUTOPLT DISENGAGED BUT I BELIEVE THE CLUTCHES ON THE SERVOS DID NOT RELEASE; DUE TO VERY HVY CTL FORCES DURING INCIDENT. DUE TO THE CTL FORCES AND IMC CONDITIONS; CTL OF ACFT WAS MOMENTARILY IN QUESTION. I ASKED FOR AND RECEIVED CLRNC FROM CTR TO RETURN TO ZZZ DUE TO DETERIORATING WX AT DEST. UPON COMPLETION OF TURN AND STABILIZATION OF AIRPLANE I TRIED TO RELIEVE THE CTL PRESSURES BY ACTIVATING THE PITCH COORDINATOR AND THE ACFT WENT INTO AN UNCOMMANDED CLB AGAIN. I DISENGAGED AND MOMENTARILY CTL WAS IN QUESTION AGAIN; AND THIS TIME I BUSTED IFR ALT ASSIGNMENT; I DECLARED AN EMER WITH APCH. I WAS GRANTED; AND I COMPLETED AN UGLY BUT SUCCESSFUL GPS APCH INTO ZZZ AND RETURNED ACFT FOR AUTOPLT REPAIR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: MAINTENANCE FOUND THAT THE BAROMETRIC ALTITUDE SENSOR HAD FAILED CAUSING THE INITIAL PITCH UP AND A LOOSE WIRE PREVENTED THE AUTOPILOT FROM BEING DISENGAGED. THE REPORTER WAS ABLE TO OVERPOWER THE AUTOPILOT BUT THE EXPERIENCE WAS VERY DISCONCERTING IN IMC.
Data retrieved from NASA's ASRS site as of January 2009 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.