A BE90 pitched nose up at FL190 causing the autopilot to trip off. The pilot recovered at FL203 and ...

Attributes
ACN	879480
Time
Date	201003
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Beechcraft King Air Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Vectors
Flight Plan	IFR
Component
Aircraft Component	Elevator ControlSystem
Person 1
Function	Single Pilot Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 150 Flight Crew Total 17700 Flight Crew Type 4100
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Altitude Excursion From Assigned Altitude Inflight Event / Encounter Loss Of Aircraft Control Inflight Event / Encounter Weather / Turbulence

Narrative:

When trying to level off at 20;000 ft; the autopilot failed commanding down on the autopilot pitch trim at full down deflection beginning at 19;000 ft. The autopilot 'kicked' off at about 20;100 ft. It left the airplane in a trim-up position. I got the plane leveled and starting down at about 20;300 ft; and then leveled at 20;000 ft with a lot of down force. Trying to re-trim the plane I found the trim wheel frozen. I hand flew for a few minutes in this condition and then finally forced the trim wheel loose. I re-engaged the autopilot with no further problems. Analysis: the plane flew through rain up to the freezing level (about 10;000 ft). I believe the trim tab assembly accumulated ice and froze; forcing the trim wheel broke it loose. I checked with the inspector who did the last plane inspection and he said the weep holes were clear.

Original NASA ASRS Text

Title: A BE90 pitched nose up at FL190 causing the autopilot to trip off. The Pilot recovered at FL203 and with down elevator force regained aircraft control. The aircraft had flown through rain up to the freezing point and ice on the elevator trim tab was the apparent cause.

Narrative: When trying to level off at 20;000 FT; the autopilot failed commanding down on the autopilot pitch trim at full down deflection beginning at 19;000 FT. The autopilot 'kicked' off at about 20;100 FT. It left the airplane in a trim-up position. I got the plane leveled and starting down at about 20;300 FT; and then leveled at 20;000 FT with a lot of down force. Trying to re-trim the plane I found the trim wheel frozen. I hand flew for a few minutes in this condition and then finally forced the trim wheel loose. I re-engaged the autopilot with no further problems. Analysis: The plane flew through rain up to the freezing level (about 10;000 FT). I believe the trim tab assembly accumulated ice and froze; forcing the trim wheel broke it loose. I checked with the Inspector who did the last plane inspection and he said the weep holes were clear.

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.

A BE90 pitched nose up at FL190 causing the autopilot to trip off. The pilot recovered at FL203 and with down elevator force regained aircraft control. The aircraft had flown through rain up to the freezing point and ice on the elevator trim tab was the apparent cause.