What happened
While attempting to depart from a gravel bar situated on the margin of the Duke of York River, the DHC-3 Otter successfully lifted off but failed to climb. During this initial ascent, the aircraft struck a steep bank composed of gravel. Following the impact, the plane performed a slight right-hand turn before settling into the river. The aircraft eventually nosed over and came to a stop in an inverted position submerged in approximately three to four feet of water.
Inside the cabin, two crew members and five passengers were trapped upside down in their seats as water entered the fuselage. Despite being suspended inverted, all occupants were able to unbuckle themselves from their restraints and successfully reach the shore.
Findings
Investigations into the accident identified several contributing elements. The pilot chose to operate from an unverified and austere airstrip where the precise length of usable runway was unknown. This departure was attempted under difficult wind conditions while the aircraft was operating at or near its maximum allowable gross weight.
Furthermore, a lack of cockpit coordination was noted, as the captain did not provide a briefing to the co-pilot or delegate the responsibility of monitoring flight instruments during the takeoff. Operational challenges were also cited, specifically regarding the difficulty of maintaining effective control over flying operations due to the hierarchical relationship between the air detachment commander and the pilot in command.