Accident Thorp T 18 N1488, Friday 6 November 2015

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Date:	Friday 6 November 2015
Time:	16:30 LT
Type:	Thorp T 18
Owner/operator:
Registration:	N1488
MSN:	303
Year of manufacture:	1968
Total airframe hrs:	1358 hours
Engine model:	Lycoming O-320-B2A
Fatalities:	Fatalities: 0 / Occupants: 1
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Independence, Oregon - United States of America
Phase:	Initial climb
Nature:	Private
Departure airport:	Independence, OR
Destination airport:	Independence, OR
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
The pilot departed on a local flight; during initial climb, the canopy partially disconnected from the airplane and the airplane vibrated violently. The pilot made a precautionary landing in a field, and the right wing impacted a fence post. Postaccident 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.

Accident investigation: