What happened
On 27 July 1998, a 28-5ACF Super Catalina, registration VP-BPS, was conducting a series of waterborne touch-and-go landings in Southampton Water as part of a promotional event. The aircraft, operated for a private flight, was performing a second approach when the crew encountered a boat wake. Shortly after the aircraft settled on the water and the pilot applied power to continue the run, a sudden jet of water erupted from the cockpit rear bulkhead.
This was immediately followed by a violent yaw to the left. The crew attempted to maintain control, but water began flooding the cockpit, causing the aircraft to decelerleate rapidly. During the evacuation, the aircraft pitched nose-down, and the bulkhead door between the compartments slammed shut, trapping passengers in the forward section. Despite the efforts of the crew to organize an escape, the aircraft sank. While most occupants escaped, 2 fatal injuries were recorded among the passengers.
The investigation
Investigators examined the wreckage after it was recovered from the seabed. The examination revealed that the nose landing gear doors had been torn off and the nose gear bay had been breached, allowing water to enter the hull. The investigation focused on the structural integrity of the door operating mechanisms and the potential for external factors, such as flotsam or the encountered boat wake, to have caused the failure.
Technical analysis of the left torque tube, which operates the nose gear doors, revealed severe internal corrosion. This corrosion had reduced the cross-sectional area of the tube by 42%, significantly weakening its structural strength. The investigation also looked into the aircraft's control settings, noting that the right rudder pedal adjustment was positioned in a way that may have limited the pilot's ability to counter the yaw.
Findings
- The primary cause of the accident was the failure of the left nose gear door torque tube due to severe internal corrosion.
- This failure allowed the nose gear doors to separate from the aircraft, exposing the nose gear bay to high hydrodynamic pressures.
- The loss of the doors led to a breach in the aft bulkhead and bay roof, creating a large aperture for water ingress.
- The resulting sudden yaw caused the left tip float to strike the water, leading to further structural damage and an increased rate of yaw.
- The internal corrosion was undetectable during standard maintenance because the torque tubes were sealed with plugs, preventing visual inspection of the interior.