What happened
At approximately 1800 MDT, an instructor and a student departed St. Albert Airport, Alberta, in a Magal Cuby II ultralight aircraft to perform commercial training exercises. During the flight, witnesses near Legal observed the aircraft flying at roughly 500 feet above ground level in a northeast direction. A loud noise was heard, and observers noted that the outer portion of the left wing had detached from the aircraft. Following this structural failure, the aircraft entered a steep descent and was destroyed upon impact with the ground. The crash resulted in two fatalities.
The investigation
The investigation focused on the structural integrity of the left wing spars. Investigators determined that the aircraft's wing was not built according to the manufacturer's original specifications, which resulted in a questionable margin of safety regarding bending strength. Evidence suggested the left wing tip had suffered previous damage that was not properly inspected or repaired. Because ultralight aircraft are exempt from certain engineering logbook requirements, the full extent of previous repairs could not be verified. Furthermore, the lack of inspection ports made it nearly impossible to examine the internal wooden spars for deterioration or damage.
Findings
- The left wing spar failure was the primary cause of the loss of control.
- The aircraft's construction did not adhere to the designer's specifications, reducing its structural strength.
- Previous damage to the wing tip had likely caused internal damage to the spar that went undetected due to inadequate inspection capabilities.
- The flight profile, which included intended maneuvers such as unusual attitudes and spins, placed aerodynamic loads on the wing that exceeded its weakened strength.
- The aircraft was not approved for spin maneuvers.
- The instructor's blood contained a cannabis-containing substance, though its impact on flight performance could not be determined.