Amateur-built S-19 N8DV accident near East Falmouth, Massachusetts

Probable cause

The experimental airplane builder's failure to properly secure the stabilator trim tab push-pull tube’s connection, which resulted in the tube’s separation and a subsequent hard landing. Contributing to the accident was the pilot/owner's failure to detect the improperly secured connection during a recent condition inspection.

NTSB analysis

The pilot reported that, during the landing flare, the experimental, amateur-built airplane "ballooned." He then relaxed back pressure on the control stick to correct; however, the airplane then struck the runway hard and departed the left side.

Examination of the wreckage revealed that the stabilator trim tab (antiservo tab) push-pull tube's threaded end had separated from its connection, that the associated nut remained loose on the threads, and that the three end threads were stripped. Further examination revealed that only three of the threads in the push-pull tube's threaded end were engaged in the trim tab connection and that about 1 inch of the threaded portion of the push-pull tube was exposed and visible on the opposite side of the securing plain nut. The kit manufacturer's assembly manual cautioned that a minimum of ten threads must be engaged to secure the stabilator trim tab push-pull connection. The manual also stated that about 0.5 inch of the threaded end of the push-pull tube should be exposed and visible on the opposite side of the securing plain nut.

The builder assembled the airplane from a kit, and it was issued a special airworthiness certificate about 20 months before the accident. The pilot purchased the airplane from the builder about 5 months before the accident. At the time of the accident, the airplane had accumulated 94.5 total flight hours. The pilot performed the last condition inspection about 4 months before the accident, which was 32.8 total flight hours before the accident. The excessive thread exposure on the opposite side of the securing plain nut would have been detectable during the most recent condition inspection; however, the pilot/owner failed to detect the excessive thread exposure during the inspection.

Text from the NTSB. Open the NTSB docket for ERA15LA360 for the full record.