A300 crew found the rudder trim inoperative at 20 degree flaps. Other flap position operated normall...

Attributes
ACN	531907
Time
Date	200112
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mia.airport
State Reference	FL
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mia.tracon
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 9r
Flight Phase	descent : approach
Route In Use	approach : instrument precision
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	531907
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	none taken : anomaly accepted
Consequence	other other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Rudder anomaly. Flight XXX had a normal en route flight with a normal descent to ILS runway 9R at mia. Rudder trim cruise settings for the rudder was selected to .9L units to maintain a centered trapezoid. While executing the ILS runway 9R at mia and after configuring the aircraft to flaps 20 degrees, I attempted to reset the rudder trim to recenter the trapezoid. The rudder trim would not work. The rudder trim would not move left or right. I selected 40 degree flaps, continuing the approach and then I again attempted to recenter the trapezoid using the rudder trim. The rudder trim worked as it should have. Upon landing, I left the rudder trim in the last position selected for the benefit of maintenance. A logbook entry was made describing the anomaly. I debriefed the mechanic who showed up at the aircraft and was told that he would be checking the system and that a byte check would be performed. The aircraft did not have any uncommanded rudder inputs at any time during the flight.

Original NASA ASRS Text

Title: A300 CREW FOUND THE RUDDER TRIM INOP AT 20 DEG FLAPS. OTHER FLAP POS OPERATED NORMALLY.

Narrative: RUDDER ANOMALY. FLT XXX HAD A NORMAL ENRTE FLT WITH A NORMAL DSCNT TO ILS RWY 9R AT MIA. RUDDER TRIM CRUISE SETTINGS FOR THE RUDDER WAS SELECTED TO .9L UNITS TO MAINTAIN A CTRED TRAPEZOID. WHILE EXECUTING THE ILS RWY 9R AT MIA AND AFTER CONFIGURING THE ACFT TO FLAPS 20 DEGS, I ATTEMPTED TO RESET THE RUDDER TRIM TO RECENTER THE TRAPEZOID. THE RUDDER TRIM WOULD NOT WORK. THE RUDDER TRIM WOULD NOT MOVE L OR R. I SELECTED 40 DEG FLAPS, CONTINUING THE APCH AND THEN I AGAIN ATTEMPTED TO RECENTER THE TRAPEZOID USING THE RUDDER TRIM. THE RUDDER TRIM WORKED AS IT SHOULD HAVE. UPON LNDG, I LEFT THE RUDDER TRIM IN THE LAST POS SELECTED FOR THE BENEFIT OF MAINT. A LOGBOOK ENTRY WAS MADE DESCRIBING THE ANOMALY. I DEBRIEFED THE MECH WHO SHOWED UP AT THE ACFT AND WAS TOLD THAT HE WOULD BE CHKING THE SYS AND THAT A BYTE CHK WOULD BE PERFORMED. THE ACFT DID NOT HAVE ANY UNCOMMANDED RUDDER INPUTS AT ANY TIME DURING THE FLT.

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.

A300 crew found the rudder trim inoperative at 20 degree flaps. Other flap position operated normally.