Aircraft Mfg & Dev. Co. (Amd) CH601XLi N451BB accident near Farmersville, Texas

Probable cause

The inadvertent tail stall and subsequent loss of airplane control as a result of the open canopy. Contributing to the accident was the inadequate emergency procedures provided by the airplane manufacturer and the inadequate design of the canopy latching mechanism.

NTSB analysis

According to the private pilot receiving instruction, during the flight he became aware of increased airflow on his side of the airplane and noted that the canopy on the flight instructor's side had become unlatched. He mentioned this to the flight instructor and the flight instructor attempted to relatch the canopy. The canopy came completely unlatched and opened to a position of 50 degrees. The nose of the airplane pitched down violently to 60 degrees. The open canopy disrupted the airflow over the empennage resulting in a stalled condition. Neither the private pilot nor flight instructor was able to close the canopy or recover the airplane from the nose low attitude. An examination of the airframe, power plant, and flight control surfaces revealed no anomalies. The latching bolts and latches related to the canopy exhibited scratching consistent with the flexing and movement of the canopy assembly. There is no mechanism to relatch just one side of the canopy without opening the other side of the canopy. According to the pilot operating handbook emergency procedures, in the event that the canopy becomes completely unlatched, the pilot is to ignore the open canopy and wind noise and land the airplane normally. The emergency procedures imply that the airplane is controllable when the canopy is open. The emergency procedures do not address a partially open canopy. Further review of the pilot operating handbook revealed conflicting airspeed information between several chapters in the book and with the markings on the airspeed indicator in the airplane.

Text from the NTSB. Open the NTSB docket for DEN08FA140 for the full record.