<< >> NASA ASRS Report 629782, August 2004

A B767 flight crew experience a malfunction in the rudder trim and deviate from assigned altitude by 300 ft.

Attributes
ACN	629782
Time
Date	200408
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : bos.airport
State Reference	MA
Altitude	msl single value : 35000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zbw.artcc
Operator	common carrier : air carrier
Make Model Name	B767 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 160 flight time total : 6400 flight time type : 2820
ASRS Report	629782
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	aircraft : equipment problem dissipated flight crew : returned to assigned altitude
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

While in cruise at FL350, noticed aircraft out of trim. Attempted to level yoke with rudder trim. Rudder trim required was approximately 5 units left rudder, deselected autoplt to see affect, the nose fell through and aircraft descended approximately 300 ft before descent could be arrested. During climb back to FL350, ZBW was advised of altitude loss. At FL348 autoplt was reengaged and aircraft began a climb at approximately 1500 FPM through FL350. The autoplt was again disengaged and aircraft stabilized at FL355 and returned manually to FL350 where it was manually trimmed. The autoplt was reengaged and aircraft remained at FL350. ZBW was kept apprise of our altitude deviation due to autoplt problems. No conflicts occurred with other aircraft. A logbook entry was made.

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Original NASA ASRS Text

Title: A B767 FLT CREW EXPERIENCE A MALFUNCTION IN THE RUDDER TRIM AND DEVIATE FROM ASSIGNED ALT BY 300 FT.

Narrative: WHILE IN CRUISE AT FL350, NOTICED ACFT OUT OF TRIM. ATTEMPTED TO LEVEL YOKE WITH RUDDER TRIM. RUDDER TRIM REQUIRED WAS APPROX 5 UNITS L RUDDER, DESELECTED AUTOPLT TO SEE AFFECT, THE NOSE FELL THROUGH AND ACFT DSNDED APPROX 300 FT BEFORE DSCNT COULD BE ARRESTED. DURING CLB BACK TO FL350, ZBW WAS ADVISED OF ALT LOSS. AT FL348 AUTOPLT WAS REENGAGED AND ACFT BEGAN A CLB AT APPROX 1500 FPM THROUGH FL350. THE AUTOPLT WAS AGAIN DISENGAGED AND ACFT STABILIZED AT FL355 AND RETURNED MANUALLY TO FL350 WHERE IT WAS MANUALLY TRIMMED. THE AUTOPLT WAS REENGAGED AND ACFT REMAINED AT FL350. ZBW WAS KEPT APPRISE OF OUR ALTDEV DUE TO AUTOPLT PROBS. NO CONFLICTS OCCURRED WITH OTHER ACFT. A LOGBOOK ENTRY WAS MADE.

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.