The pilot departed on a flight around Independence, Oregon. During the initial climb, the canopy on the Thorp T-18 partially disconnected and the airplane vibrated violently.
He made a precautionary landing in a field, and the right wing hit a fence post.
Post-accident examination revealed that the mechanism that allowed the canopy to move fore and aft and retained the aft portion of the canopy during flight separated at a weld, which resulted in airflow into the cockpit.
The components were not made available for metallurgical examination and the failure mode could not be determined. However, it is possible that the separation was due to repeated loading on the canopy over time.
According to the pilot and a representative of the airplane type club, the canopy design was unique to the accident airplane, and was likely the only one of its kind.
Probable cause: A separation of the canopy mechanism during flight, which resulted in the pilot’s precautionary landing and the airplane’s subsequent collision with a fence post.
NTSB Identification: WPR16LA023
This November 2015 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.