What happened
During the approach to Whyalla Airport, the flight crew had initiated sterile cockpit procedures when the cover for the aircraft's ditching dam partially opened. This movement allowed aerodynamic forces to fully open the cover, causing the dam bag to unfurl into the airstream. The resulting impact of the bag, cover, and inflation hose against the fuselage created loud noises within the cabin. The cabin crew interrupted the sterile cockpit environment to alert the flight crew to the abnormal noise. The crew managed the situation using non-normal checklists and effective resource management.
The investigation
The investigation focused on why the ditching dam cover became unseated. While the aircraft had previously encountered severe turbulence and icing during the flight, conditions were benign at the time the cover opened. However, investigators considered that earlier exposure to severe weather might have compromised the cover's security.
Post-occurrence examination of a replacement ditching dam revealed that it did not meet the necessary engagement tolerance within the airframe retaining channel. This suggested that the cover may have appeared visually secure during pre-flight inspections despite not being properly engaged. The investigation determined that the deployment of the device did not pose a risk to the continued safe flight or damage to other aircraft systems.
Findings
- The ditching dam cover opened in-flight, potentially due to improper engagement of the cover with the airframe or previous exposure to severe icing and turbulence.
- The cover may have appeared secure during pre-flight inspections while failing to meet required engagement tolerances.
- The cabin crew acted appropriately by breaking the sterile cockpit environment to report the abnormal situation.
- The deployment of the ditching dam was unlikely to have caused further damage to the aircraft given its specific location.