TSB Recommendation A06-05

In its 14 June 2006 letter, Transport Canada (TC) provided the following comments:

• TC concurs with the TSB suggestion that the current A310-300 inspection program may not be adequate to provide timely detection of defects to the rudder assembly. This may be caused by either inappropriate inspection intervals or inadequate inspection techniques.
• At the time of this occurrence, composite materials in general were, from a maintenance perspective, believed to have a no damage growth design philosophy. It was also believed that, from a fatigue point of view, more frequent inspections of composite materials would not prove to be more effective. In addition, these concepts were an industry-accepted philosophy during the development of maintenance programs using the Maintenance Review Board (MRB) process.
• As a result of this occurrence, and the additional findings based on the Airbus AOT, TC now believes that there is potential for damage growth. Following this determination, the Department inspected additional Canadian-registered Airbus A310-300 series aircraft in order to evaluate the effectiveness of the current Airbus maintenance program.

The following corrective actions are currently being taken by TC:

• TC will send a letter to Airbus Industries and the Direction Générale de l'Aviation Civile (DGAC) of France detailing the results of the additional inspection on a Canadian-registered Airbus A310-300 series aircraft.
• TC will recommend that a detailed inspection of the drainage path of the rudder for blockage be added to the current inspection program to ensure that there is adequate drainage.
• TC will request that Airbus Industries review the current inspection program for the vertical stabilizer and rudder assembly for the Airbus A300/A310 aircraft series.
• Because a tap test, a scheduled inspection of the rudder required at the time of the occurrence, is potentially not effective in determining smaller areas of delamination or disbond of composite materials, TC is currently working with the National Research Council of Canada to identify suitable inspection techniques that will detect failures in composite materials.
• To better identify failures in composite material, TC will coordinate with the International MRB Policy Board to review the logic used in developing maintenance programs.

In its 14 June 2006 response, TC states that it is currently working with the National Research Council of Canada to identify suitable inspection techniques that will detect failures in composite materials. TC will recommend that a detailed inspection of the drainage path of the rudder for blockage be added to the current inspection program to ensure that there is adequate drainage. TC will also request that Airbus Industries review the current inspection program for the vertical stabilizer and rudder assembly for the Airbus A300/A310 aircraft series, and will work with the International MRB Policy Board to review the logic used in developing maintenance programs.

TC concurs that the current Airbus A310-300 inspection program may not be adequate to provide timely detection of defects to the rudder assembly; however, the response will not significantly reduce or eliminate the risk as stated in the recommendation in the short term, until the intended actions result in the development of an early and consistent detection program of any damage to the affected rudders. Consequently, the response is assessed as Satisfactory Intent.

In its letter dated 07 February 2007, TC provided the following comments:

• TC has made Airbus and the DGAC aware of the findings made on a number of Canadian-registered A310-300 aircraft, as part of the continuing AOT initiative.
• TC will, at the next scheduled A310/A300-600 Industry Steering Committee meeting, recommend to Airbus that a detailed inspection for blockage of the rudder drainage path be added to the current inspection program.
• TC will request that Airbus Industries continue to review the current inspection program for the rudder assembly for the A300/A310 aircraft series.
• TC will monitor the Airbus initiative to develop an ultrasound inspection technique to detect rudder skin disbond for repetitive application as part of the rudder inspection schedule.
• TC will be presenting an issue paper at the next International MRB Policy Board meeting. The paper will discuss the impact that composite material failures will have on the logic processes used in developing maintenance programs.

While TC's latest response includes actions previously reported to the TSB, it also contains new information, which demonstrates a continued support for the suggested course of action identified in Recommendation A06-05. Because the action plan, when fully implemented, will substantially reduce the safety deficiency identified in Recommendation A06-05, the assessment remains as Satisfactory Intent.

In its response of 06 March 2008, TC provided the following comments:

• TC has made Airbus and the DGAC of France aware of the findings made on a number of Canadian-registered Airbus A310-300 aircraft, as part of the continuing AOT initiative, thus making it unnecessary to duplicate reporting by letter.
• TC has recommended and discussed with Airbus a detailed inspection for blockage of the rudder drainage path to be added to the current inspection program, to ensure that there is adequate drainage.
• TC has requested that Airbus Industries continues to review the current inspection program for the rudder assembly for the Airbus A300/A310 aircraft series. This is ongoing.
• TC will monitor the Airbus initiative to develop an ultrasound inspection technique to detect rudder skin disbond for repetitive application as part of the rudder inspection schedule. A repetitive inspection will be reviewed at the next Industry Steering Committe (ISC) meeting in 2008.
• Airbus Central Entity for Maintainability and Maintenance Engineering has confirmed that rudder ultrasonic inspection results are being reviewed to determine what actions affecting the aircraft inspection schedule need to be taken. TC will discuss progress made at the next ISC meeting in the second quarter of 2008.

In addition to TC's action taken, the European Aviation Safety Agency (EASA), on 08 October 2007, issued Airworthiness Directive (AD) 2007-0266 (Stabilizers - Vertical Stabilizer & Rudder Structure - Inspection/Repair for A310, A300-600 Aircraft), and on 14 January 2008, issued AD 2008-0012 (Stabilizers - Carbon Fiber Reinforced Plastic (CFRP) Rudder - Inspection/Repair for A330, A340-200/-300 Aircraft). These ADs demand more sophisticated inspection techniques than the original tap test; specifically, the inspections now require ultrasonic, thermography, and x-ray processes.

In addition, these ADs demand a mixture of new, one-time and repetitive inspections of areas where damages were found during the TSB investigation, and the periodicity of these inspections is not just based on somebody's best guess, but has been substantiated using knowledge of damage growth rates demonstrated by testing conducted during the TSB investigation.

TC's response not only addresses the specific course of action identified in Recommendation A06-05, but TC is taking significant supplementary action to address the longer-term risks of composite structure failures. TC's action taken has significantly mitigated the risks associated with the deficiency underlying Recommendation A06-05.

Therefore, this response to Recommendation A06-05 is assessed as being Fully Satisfactory.