Accident Details
On the afternoon of the accident, a single-pilot aircraft was conducting firefighting operations near Lake Wicksteed, approximately 10 nautical miles north of Hornepayne, Ontario. The lake, about 7300 feet in length, features gentle rising terrain along its shoreline. The pilot was performing his third water scoop of the day, approaching the lake from an easterly direction in light wind conditions.
Sequence of Events
The pilot completed inbound checks, lowered the water probes, and touched down on the lake to begin filling the float water tanks. Shortly after, water spraying from the overflow vents on top of the floats indicated that the tanks were full. The pilot pressed a button on the yoke to retract the probes. Immediately, the aircraft nosed over into the lake in a wings-level attitude and began to sink. The accident occurred at approximately 1800 eastern daylight time.
The pilot extricated himself from the aircraft and held onto the side of the partially submerged float. A witness who observed the event immediately launched a powered aluminum boat to assist the pilot, while another witness traveled to Hornepayne to alert authorities and emergency services. After reaching shore, the pilot was taken to a nearby cottage where he remained until emergency services arrived. The aircraft came to rest inverted on the bottom of the shallow lake, with its floats above the water surface.
Probable Cause
Findings as to Causes and Contributing Factors: 1. Ministry of Natural Resources DHC-6 SOPs were not followed, and the Vital Action checklist was not fully completed during the approach. As a result, the bomb door armed switch on the centre panel was not selected Off after the previous water bombing run and prior to the scooping operation. 2. After completing the water scooping operation, the pilot unintentionally selected the bomb door push button switch instead of the adjacent probe switch. Because the bomb door armed switch on the centre panel was left On, the bomb doors extended into the water. Drag from the doors and the water rushing into the door openings resulted in the aircraft nosing over in the water. 3. The hinged cover plate for the bomb door push button switch was not re-installed following maintenance to replace the push button switch. The push button was exposed, making an inadvertent selection more likely.