CE560 flight crew experienced runaway trim at 14;000 ft with the autopilot engaged. When auto pilot ...

Attributes
ACN	898937
Time
Date	201007
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Citation Excel (C560XL)
Operating Under FAR Part	Part 91
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Horizontal Stabilizer Trim
Person 1
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Altitude Excursion From Assigned Altitude Inflight Event / Encounter Loss Of Aircraft Control

Narrative:

About 5 minutes after take off and at approximately 14;000 ft and about 250 KTS I saw the master caution flicker and didn't observe any associated lights. A few seconds later the master caution came back on with the stab miscompare for just a moment then went back off. I checked the flap handle to insure it was at 0 and it was. Shortly after that the captain disengaged the autopilot and the aircraft immediately pitched approximately 20 degrees nose down. At that time I called ATC and declared an emergency and told them I would contact them with more info after we got the aircraft under control. At approximately 8;000 ft the captain had the airplane under control and everything appeared to be normal. During this time there were no abnormal indications in the cockpit except for the uncommanded pitch. We canceled the emergency with ATC and proceeded back to the FBO. While at the FBO we checked the operation of the flaps and stab and they appeared to be working normally.

Original NASA ASRS Text

Title: CE560 Flight Crew experienced runaway trim at 14;000 FT with the autopilot engaged. When auto pilot disengaged after stab miscompare warning; aircraft pitched hard over and lost 6;000 FT before control can be regained. An emergency was declared and flight returns to departure airport.

Narrative: About 5 minutes after take off and at approximately 14;000 FT and about 250 KTS I saw the master caution flicker and didn't observe any associated lights. A few seconds later the master caution came back on with the stab miscompare for just a moment then went back off. I checked the flap handle to insure it was at 0 and it was. Shortly after that the Captain disengaged the autopilot and the aircraft immediately pitched approximately 20 degrees nose down. At that time I called ATC and declared an emergency and told them I would contact them with more info after we got the aircraft under control. At approximately 8;000 FT the Captain had the airplane under control and everything appeared to be normal. During this time there were no abnormal indications in the cockpit except for the uncommanded pitch. We canceled the emergency with ATC and proceeded back to the FBO. While at the FBO we checked the operation of the flaps and stab and they appeared to be working normally.

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.

CE560 flight crew experienced runaway trim at 14;000 ft with the autopilot engaged. When auto pilot disengaged after stab miscompare warning; aircraft pitched hard over and lost 6;000 ft before control can be regained. An emergency was declared and flight returns to departure airport.