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Hawker 800 captain had an autopilot pitch up while attempting to descend due to a 'max speed' flag with the speed 15 knots below maximum. An altitude deviation above the original cruise altitude occured. Queries to honeywell; the avionics package manufacturer; indicate that this is normal operation.
| Attributes | |
| ACN | 976492 |
| Time | |
| Date | 201110 |
| Local Time Of Day | 0601-1200 |
| Place | |
| Locale Reference | ZZZZ.ARTCC |
| State Reference | FO |
| Environment | |
| Flight Conditions | VMC |
| Aircraft 1 | |
| Make Model Name | BAe 125 Series 800 |
| Operating Under FAR Part | Part 91 |
| Flight Phase | Descent |
| Flight Plan | IFR |
| Person 1 | |
| Function | Captain Pilot Flying |
| Qualification | Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine |
| Experience | Flight Crew Last 90 Days 45 Flight Crew Total 5525 Flight Crew Type 525 |
| Events | |
| Anomaly | Aircraft Equipment Problem Less Severe Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance |
Narrative:
With the autopilot engaged at FL240; we were beginning our decent to 12;000. We were indicating about 15 KTS below red line (320 KTS). I selected vertical speed and rolled in about 2;000 FPM down; the nose began to lower and then we showed a 'max speed' flag; and the aircraft immediately began to pitch up to a 1;500 FPM climb. By the time I recovered; we had climbed up to 24;400 ft. The speed was never within 10 KTS of max speed; and the climb took me by surprise. I have personally experienced this phenomenon in a decent before today; but never at our maximum clearance altitude; which directly related to our altitude deviation. ATC did inquire to say our altitude and we were already in the decent at that point passing back through 24;000. We have the honeywell primus epic avionics package installed and we have had discussions with them regarding this bug where the aircraft autopilot pitches up steeply on a 'max speed' flag; when we are still at least 10-15 KTS slower than red line. They say it is normal operation.
Original NASA ASRS Text
Title: Hawker 800 Captain had an autopilot pitch up while attempting to descend due to a 'max speed' flag with the speed 15 knots below maximum. An altitude deviation above the original cruise altitude occured. Queries to Honeywell; the avionics package manufacturer; indicate that this is normal operation.
Narrative: With the autopilot engaged at FL240; we were beginning our decent to 12;000. We were indicating about 15 KTS BELOW Red Line (320 KTS). I selected vertical speed and rolled in about 2;000 FPM DOWN; the nose began to lower and then we showed a 'Max Speed' flag; and the aircraft immediately began to pitch up to a 1;500 FPM CLIMB. By the time I recovered; we had climbed up to 24;400 FT. The speed was never within 10 KTS of max speed; and the climb took me by surprise. I have personally experienced this phenomenon in a decent before today; but never at our maximum clearance altitude; which directly related to our altitude deviation. ATC did inquire to say our altitude and we were already in the decent at that point passing back through 24;000. We have the Honeywell Primus Epic avionics package installed and we have had discussions with them regarding this bug where the aircraft autopilot pitches up steeply on a 'Max Speed' flag; when we are still at least 10-15 KTS SLOWER than Red Line. They say it is normal operation.
Data retrieved from NASA's ASRS site as of April 2012 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.