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Air transportation safety recommendation A06-05

Reassessment of the Responses from Transport Canada to Aviation Safety Recommendation A06-05

Inspection Program of Rudder Assembly

 Recommendation 06-05 in PDF [257 KB]


On 06 March 2005, an Airbus A310-300, serial number 597, registration C-GPAT, operated by Air Transat as Flight 961, departed Juan G. Gomez International Airport in Varadero, Cuba, for Québec/Jean Lesage International Airport, Quebec, with 2 pilots, 7 flight attendants, and 262 passengers on board. While the aircraft was in the early en route phase of the flight, a loud noise was heard, followed by vibrations. The aircraft then started a dutch roll motion. The crew was able to stabilize the aircraft once it had descended to a lower altitude. Following a discussion with the company, the captain decided to return to Varadero. On arrival at Varadero, it was discovered that the aircraft rudder was missing.

The rudder is made of composite sandwich construction, consisting of a nomex honeycomb core with carbon fibre face sheets. The rudder had separated from the aircraft except for its bottom closing rib and the length of spar between the rib and the hydraulic actuators. Only small residual amounts of rudder side panel remained attached.

Following the occurrence, other aircraft were inspected to evaluate the structural integrity of rudders in the fleet. In March 2005, Airbus issued an All Operators Telex (AOT) for the inspection of all aircraft equipped with part number A55471500 series rudders. This one-time visual and tap-test inspection involved 222 Airbus A310s, 146 Airbus A300-600s, 6 Airbus A330s, and 34 Airbus A340s, for a total of 408 aircraft. In addition, a more detailed inspection of rudder side panels on over 20 aircraft was conducted using the elasticity laminate checker (ELCH) test method. Finally, the attention drawn to rudders by the occurrence resulted in operators examining their rudders more closely during maintenance. These various inspections found examples of disbonds, damage around hoisting points and trailing edge fasteners of the rudder, corrosion and abrasion at hinges, seized hinges, hinges with excessive free play, water ingress, and hydraulic fluid ingress.

The findings of the fleet inspection suggest that the current inspection program may not be providing an adequate oversight for timely detection of defects and damages.

On 27 March 2006, the Board released interim safety recommendations as part of its investigation (A05F0047) into this occurrence.

Board Recommendation A06-05 (27 March 2006)

The separation of the rudder from Air Transat Flight 961 and the damage found during the post-occurrence fleet inspections suggest that the current inspection program for Airbus composite rudders may not be adequate to provide for the timely detection of defects. In addition, the recent discovery that disbonds could grow undetected and the increasing age of the composite rudders suggest that increased attention is warranted to mitigate the risk of additional rudder structural failures. The consequences of a rudder separation include reduced directional control and possible separation of the vertical tail plane.

Therefore, the Board recommended that:

The Department of Transport, in coordination with other involved regulatory authorities and industry, urgently develop and implement an inspection program that will allow early and consistent detection of damage to the rudder assembly of aircraft equipped with part number A55471500 series rudders.
Transportation Safety Recommendation A06-05

Response to A06-05 (14 June 2006)

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

The following corrective actions are currently being taken by TC:

Board Assessment of the Response to A06-05 (04 October 2006)

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.

Response to A06-05 (07 February 2007)

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

Board Reassessment of the Response to A06-05 (24 July 2007)

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.

Response to A06-05 (06 March 2008)

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

Board Reassessment of the Response to A06-05 (13 August 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.

Next TSB action

No further action is required.

This deficiency file is assigned a Closed status.