What happened
A Seair Seaplanes Ltd. deHavilland DHC-2 MK 1, registration C-GTMC, was departing Lyall Harbour, Saturna Island, for Vancouver International Airport with a full load of passengers. After an initial unsuccessful takeoff attempt downwind, the pilot attempted a takeoff into the wind. During the climb, the aircraft encountered atmospheric turbulence and mountain waves, causing the pilot to bank the aircraft to the left to avoid rising terrain. This maneuver, combined with the environmental conditions, led to an aerable aerodynamic stall. The aircraft's nose pitched down and it descended rapidly into the water. While the pilot and one passenger survived with serious injuries, the remaining six passengers perished.
The investigation
Investigators examined the aircraft's mechanical state and the pilot's flight parameters. The investigation revealed that the aircraft's stall warning system was unserviceable due to a blown 5-amp fuse caused by electrical loads from other cabin lights. Additionally, the stall warning horn had been modified with silicone sealant to reduce its volume, making it difficult to hear over engine noise. The aircraft was also found to be loaded with a center of gravity that exceeded the aft limit for floatplane operations. The investigation also looked into the aircraft's structural configuration, noting the absence of jettisonable windows or alternative emergency exits.
Findings
- The primary cause of the accident was an aerodynamic stall triggered by the combined effects of increased load factor from a bank angle and significant atmospheric turbulence.
- The pilot received no warning of the impending stall because the stall warning system was non-functional and the audio horn was muffled.
- The aircraft's aft center of gravity hindered a full recovery from the stall.
- Impact forces jammed two of the four cabin doors, significantly restricting the ability of passengers to escape the sinking aircraft.
- The pilot's seat failed upon impact, leaving the pilot unrestrained and causing injuries that limited his ability to assist passengers.