Tahiti AT72 at Papeete on Jun 25th 2011, rudder trim not connected

Last Update: July 23, 2013 / 14:15:42 GMT/Zulu time

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Incident Facts

Date of incident
Jun 25, 2011

Classification
Report

Airline
Air Tahiti

Flight number
VT-422

Aircraft Registration
F-OIQU

Aircraft Type
ATR ATR-72-200

ICAO Type Designator
AT72

An Air Tahiti Avion de Transport Regional ATR-72-500, registration F-OIQU performing flight VT-422 from Papeete to Bora Bora (Tahiti), was in the initial climb out of Papeete accelerating through about 170 KIAS when the captain noticed the ball of the turn indicator was fully to the right. Applying the rudder he managed to get the ball about halfway between center and full right, but grew concerned they would not have sufficient rudder authority to compensate for a left hand engine failure. The first officer's instrument also showed the ball right off the center, so that the captain decided to return to Papeete for a safe landing.

On Oct 2nd 2012 the French BEA released their final report in French followed by the release of the English translation on Jul 23rd 2013 concluding the probable cause of the serious incident was:

incomplete implementation and verification of maintenance work, which resulted in the undetected omission of re-connecting the rudder trim components.

Contributing factors were:
- limitations of the computer system in use by maintenance, that only permitted to enter the start and end of maintenance without detailing the individual steps
- lack of signature cards by engineers and supervisor for each maintenance task

The aircraft had undergone maintenance between May 30th 2011 and June 24th 2011.

On Jun 10th a detailed inspection of the torque tube revealed corrosion, the supervisor thus decided to add the task of treating the torque tube against corrosion and thus handed mechanics A work cards which included to disconnect the control rod of the rudder trim in the tail of the aircraft as part of the overall task. The mechanics entered the completion of the task into the computer system, however without the possibility to mention the rudder trim control rod has been disconnected.

The torque tube was subsequently treated against corrosion and re-assembled on Jun 21st by mechanics B, who continued to reinstall the torque tube, which should have included the re-connection of the rudder trim control rod. That step however was omitted, the mechanics closed the access doors without noticing the control rod was disconnected.

At the end of the work the then supervisor did not inspect the rudder because according to the original maintenance plan no work was to be carried out in the rudder area. Control surface movements also did not show any anomalies, however, the inspection had not actually watched the movement of the trim tabs but the indicator at the trim actuator. This indicator however only showed the movement of the cylinder, but not the actual position of the trim tab.

The last work card of the control surface movement tests was omitted because no work was supposed to be done on the rudder. That work card would have required to measure the actual angles of the trim tabs and verify they are consistent with the trim actuator movements and indications in the cockpit.

The aircraft was subsequently returned to service on Jun 24th.

The operator took a number of safety actions immediately to address the issues with maintenance documentation and task management.
Incident Facts

Date of incident
Jun 25, 2011

Classification
Report

Airline
Air Tahiti

Flight number
VT-422

Aircraft Registration
F-OIQU

Aircraft Type
ATR ATR-72-200

ICAO Type Designator
AT72

This article is published under license from Avherald.com. © of text by Avherald.com.
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