WPR22FA048 · Zenith Zodiac CH601XL

About seven minutes after departure, following what appeared to be an uneventful takeoff and initial climb, the airplane began a 180° turn toward the departure airport. A few minutes later, witnesses heard a loud bang, and the airplane pitched down aggressively, rolled inverted, and impacted the ground in a steep, nose-down attitude. During the descent, the pilot’s flight bag and other cabin contents fell out of the airplane, and the sound of buffeting wind noise and the pilot struggling were heard on the airport’s common traffic advisory frequency.

Examination did not reveal any anomalies with the flight controls or engine that would have precluded normal operation, and all components from the airplane were found in the immediate vicinity of the impact site. There was no evidence of bird strike.

The owner/builder of the airplane stated that he had once experienced the canopy opening on takeoff but was able to land safely. As a result of this event, he disabled the standard lock and installed a set of two small over-center latches, each mounted to the rear sides of the canopy frame with two soft aluminum rivets.

Examination of the canopy system revealed damage signatures that appeared to indicate that the rivets of one latch had separated in shear, and the other latch had twisted away from the airframe. It is likely that the accident was initiated by the failure of the mounting rivets in one latch, which caused the canopy to partially open on one side, then twist the latch away from the other side, resulting in an open and possibly deformed canopy. The reason for the initial failure could not be determined; however, the owner of the airplane was shorter than the pilot and had raised the seat and moved it forward during construction. The modification would have resulted in the accident pilot having to lean inboard, or sit with his head tilted, to avoid touching the canopy. It is possible that the airplane encountered turbulence that caused the pilot to hit the canopy, resulting in the failure of one of the latches.

Multiple instances of canopies opening in flight were reported for this airplane model. Because an open canopy disturbs airflow over the horizontal stabilizer, flight control difficulties can result in a loss of control nose-down pitching motion, often accompanied by a loud banging sound and cabin contents being sucked out, all which were observed in this accident. Although the Pilot Operating Handbook (POH) provides instructions for continued flight with an open canopy, evidence from both this and previous accidents suggests that both the nose-down motion and associated negative G-forces can be hard for pilots to maintain airplane control.

The airplane’s POH suggested the installation of a secondary backup latch system, and 2 weeks following the accident, the manufacturer issued a safety alert recommending such. The accident airplane was not equipped with a secondary latch.

Verbatim NTSB analysis and probable cause from the NTSB dataset