What happened
On 8 October 1998, a Concorde Type 1 Variant 102, registration G-BOAC, was operating a scheduled passenger service from London Heathrow to New York JFK. While cruising at Mach 2.0 over the North Atlantic, the crew experienced a sudden thump and continuous vibration throughout the cabin.
Upon inspecting the visible flight controls, the crew found the elevons to be intact and functioning normally. To mitigate increased vibration during the transition to subsonic speeds, the crew reduced thrust to idle power. Following a normal landing at JFK, air traffic control informed the crew that a section of the aircraft's rudder appeared to be missing. The aircraft had sustained damage to the lower rudder control surface, with a significant portion of the lower wedge having separated.
The investigation
The AAIB examined the aircraft and the failed rudder component. Investigation of the wreckage in New York revealed that approximately 60% to 70% of the lower wedge was missing, and the remaining core had completely disbonded from the left skin. The investigation also noted damage to the stub fairing, which had been struck by the remaining rudder structure. A bolt was found to be missing from the fairing's attachment to the tailcone.
Detailed metallurgical and adhesive analysis was conducted at DERA Farnborough. While the rudder was a relatively new component, investigators discovered a disbond in the upper wedge of the rudder. This defect was located near a rivet in the closing rib. The investigation also explored whether the manufacturing process of the rivets—specifically the hydraulic squeezing method—had caused localized damage to the adhesive bond.
Findings
- The primary cause of the failure was a disbond that likely originated during the manufacturing process.
- The defect was located in a metal-to-metal bond area, which was not detectable by the standard in-service Mechanical Impedance Analyser (MIA) or ultrasonic scans used by the operator.
- There was evidence that the hydraulic pressure used to form rivets in the trailing edge may have caused a local disbond that eventually spread into the skin/core bond.
- The aircraft's design successfully prevented a total loss of control, as the failure was limited to a single rudder wedge.
- The inspection of the rudder stub fairing attachments was identified as an area requiring improved oversight.