ERA22FA387 · SEA & SKY Inc KRUCKER CYGNET

The pilot and one passenger were departing from a lake for a local flight in the weight-shift-control aircraft. The pilot’s wife reported that the aircraft did not become airborne at the usual location. Video captured by an onboard camera revealed that, after becoming airborne with the engine operating about 300 rpm below the takeoff rpm setting, the aircraft began a slow climb while flying toward the south edge of the lake. Near the south end of the lake, with the engine operating at the same rpm, the climb stopped and the pilot abruptly manipulated the controls, likely to avoid trees ahead and prevent an aerodynamic stall. Around this time, the pilot’s wife heard a “pop” sound. The aircraft then entered a left descending spiral, impacting the tree canopy then the ground. Examination of the flight controls revealed no evidence of preimpact failure or malfunction. Damage signatures observed on one propeller blade indicated that the pop sound heard by the witness was likely the sound of the propeller blade impacting a control cable during the impact sequence. Examination and postaccident operational testing of the engine and propeller revealed that the propeller blade angle was set higher than optimal for the propeller/engine combination, preventing the engine from attaining the published takeoff power setting of 5,800 rpm. Additionally, calculations of the engine rpm during both the accident flight and one previous takeoff recorded by the onboard camera revealed the rpm to be consistent with the engine operating at or near its published maximum continuous power setting (5,500 rpm), rather than the takeoff power setting (5,800 rpm). Given the weights of the occupants and the fuel found onboard after the accident, the aircraft was a minimum of 29 lbs over design gross weight at the time of the accident, but could have been as much as 62 lbs, or about 5.8%, over the design gross weight at the start of the flight. The density altitude at the time of the accident was about 2,950 ft mean sea level. It is likely that the combined effects of the pilot’s operation of the aircraft in an overweight condition, the engine operating at less than the specified takeoff rpm throughout the flight, and the increased density altitude reduced the aircraft’s climb performance, resulting in impact with trees and terrain.

Verbatim NTSB analysis and probable cause from the NTSB dataset