Investigation Summary
The incident involving C-GPAT exposed a critical vulnerability in the composite rudders used on Airbus A300 and A310 series aircraft. The rudder, a sandwich structure consisting of a honeycomb core between composite skins, failed due to a phenomenon where internal damage could propagate without being visible on the exterior. While the broader investigation into the A300/A310 fleet identified hydraulic fluid contamination as a major risk for initiating progressive disbonding, the TSB attributed the specific failure of C-GPAT to either a discrete event or a weak bond at the z-section of the left side panel. Because the A310 rudder design lacked features to mechanically arrest the growth of such fractures, the damage eventually reached a critical size, leading to the total separation of the rudder surface from the vertical stabilizer. The crew faced significant challenges as the aircraft entered a Dutch roll, a rhythmic oscillation of yaw and roll. They initially considered diverting to Fort Lauderdale but returned to Varadero at the company's suggestion. The lack of cockpit warnings for the rudder failure complicated the diagnosis, as the ECAM system showed no malfunctions despite the physical loss of the control surface.
Final Conclusions
The Transportation Safety Board of Canada (TSB) concluded in report A05F0047 that the rudder detached due to the growth of a pre-existing disbond or in-plane core fracture. The investigation determined that the manufacturer's recommended inspection program, which relied heavily on external 'tap tests,' was inadequate for detecting internal damage or hydraulic fluid ingress. Furthermore, the rudder design did not include features to stop the progression of such damage once initiated. The TSB also noted that the 30-minute Cockpit Voice Recorder (CVR) was insufficient, as the data from the actual failure was overwritten by the time the aircraft landed.
Video Analysis
Inadequate Maintenance Procedures | Air Transat Flight 961 — A detailed look at the structural failure of Air Transat Flight 961, where an Airbus A310 lost its rudder in flight due to undetected composite delamination.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Systems & Failure Modes
Composite Rudder
A control surface made of a honeycomb core sandwiched between composite skins. The investigation found these were susceptible to undetected internal disbonds.
ECAM (Electronic Centralized Aircraft Monitor)
The system designed to alert pilots to malfunctions; it failed to provide any warning because it did not have sensors to detect the physical loss of the rudder structure.
Yaw Damper
A system used to reduce Dutch roll tendencies. The crew initially suspected a dual yaw damper failure, though the switches remained engaged.
Interesting Facts
- 01The aircraft was an Airbus A310-308ET, registration C-GPAT, manufactured in 1992.
- 02The rudder (P/N A55471500) was in the 'pre-modification 8827' configuration, where rivets penetrate the honeycomb core to join skin panels to the front spar.
- 03The rudder separated completely, leaving only the bottom closing rib and the spar between the rib and actuators.
- 04The vertical stabilizer's two rearmost attachment lugs were damaged by high stresses during the rudder separation, similar to stresses seen in the AA587 accident.
- 05There were no ECAM messages or cockpit warnings indicating the loss of the rudder during the flight.
- 06The CVR only recorded the final 30 minutes of the flight, meaning the audio of the actual failure was lost.
Safety Actions & Advisories
Rudder Inspection Program Overhaul
The TSB and NTSB recommended the urgent development of new inspection programs to detect internal damage in A55471500 series rudders, moving beyond simple external tap tests.
CVR Duration Increase
The TSB issued a safety advisory regarding the need for cockpit voice recorders to capture longer periods of data to prevent critical event information from being overwritten.
Airbus All Operators Telex (AOT)
Airbus issued mandatory AOTs requiring visual and manual tap test inspections of the inner side of rudder panels for all A300 and A310 series aircraft.