Amateur-built LANCAIR EVOLUTION N7569A accident near Saratoga, Wyoming

Probable cause

A windshield failure during cruise flight due to stress concentrations in the bond area as a result of improper assembly of the windshield.

NTSB analysis

While in cruise flight at 27,000 ft mean sea level, the experimental, amateur-built airplane’s windshield shattered, followed immediately by a rapid decompression of the cabin. The pilot performed an emergency descent and landed uneventfully. The windshield was substantially damaged.

Examination revealed that the fracture originated from a small crack located at the exterior surface of the windshield within the bonded edge. The presence of parallel linear scratches near the fracture origin and on the windshield edge suggests that the bonded area was not sanded in accordance with the build instructions. The evidence also suggests that the in-service stresses in the as-manufactured windshield were high enough to cause fractures from scratches that deviated from the build instructions; therefore, it is likely that the windshield failure was the result of stress concentrations in the bond area due to scratches made with methods inconsistent with the build instructions.

Text from the NTSB. Open the NTSB docket for WPR21LA108 for the full record.