Incident Overview
On an unspecified date, a De Havilland DHC-2 'Beaver' seaplane departed Lake Union seaplane base with four passengers from the British Broadcasting Company. The flight was tasked with aerial videography of an east-west geological fault line crossing from south Seattle through Blakely Harbor near the south end of Bainbridge Island.
Flight Sequence
An onboard video recorder captured a voice instructing: "Keep as low as you can and slow as you can while we're doing this please..." The pilot-in-command (PIC) completed a first pass over the south end of Bainbridge Island without incident and maneuvered for a second pass. During the second pass, the PIC reported that as he approached upsloping, tree-covered terrain, he applied climb flaps and power but shortly realized the climb rate was less than expected. He attempted a shallow left turn toward downsloping terrain and then leveled the wings as the aircraft descended into the treetops. Two onboard video recordings corroborated this sequence.
Pilot Report and Conditions
The PIC reported no powerplant or control system malfunction during the accident flight. He also reported encountering a downdraft condition over the tree-covered terrain. According to reporting stations near the accident site, winds remained below 12 knots throughout the day. The video recordings showed no wind streaking and only sporadic whitecaps on the surface of Puget Sound during the transit from Seattle to the south end of Bainbridge Island.
Investigation Findings
The official investigation determined that the probable cause was the pilot-in-command's failure to maintain adequate clearance from trees/terrain. Contributing factors were identified as rising terrain and trees.