What happened
On a local flight from Cordingley Lake, Ontario, a Cessna 180H floatplane, registration N720CS, failed to climb sufficiently during takeoff, leading to a collision with trees. The aircraft, carrying the pilot and two passengers, began its takeoff run without backtracking. After reaching tree-top height, the aircraft ceased to accelerate or climb, with airspeed dropping to approximately 60 mph.
As the aircraft approached the shoreline, the pilot attempted to maneuver toward lower terrain and deployed full flaps while maintaining full power, hoping to cushion the impact. The aircraft struck the treetops and subsequently pitched nose-down into the ground. The three occupants sustained minor injuries, and a small fuel-fed fire occurred following the impact.
The investigation
The investigation focused on the aircraft's performance capabilities and the pilot's takeoff technique. Investigators examined the interaction between the installed Canadian Aircraft Products (CAP) series 3000D floats and the 78-inch, three-blade Hartzell propeller.
It was established that while the three-blade propeller was approved under a supplemental type certificate (STC), the performance analysis used for that approval compared the 78-inch propeller to 82-inch propellers used on landplanes, rather than the 88-inch propeller typically used for floatplane configurations. Consequently, the aircraft could not meet the performance specifications listed in the Cessna owner's manual supplement. Furthermore, the pilot was unaware of a specific takeoff procedure—involving early flap retraction—that the aircraft owner had developed to compensate for this performance loss.