Amateur-built ACRO-SPORT I N5897 accident near Midland, Louisiana

Probable cause

The failure of the left elevator torque tube due to poor quality welds by the manufacturer, which resulted in the loss of pitch control.

NTSB analysis

The pilot reported that, while practicing aerobatics, he pulled the control stick aft and that something in the elevator control system then "broke," and the airplane's nose subsequently started to drop. The pilot established that he still had aileron and rudder control; however, he was not able to control the airplane's pitch. The pilot chose to parachute from the airplane and subsequently landed in a field. The airplane crashed into a field south of the pilot's location and was substantially damaged during the impact.

An examination of the flight control system revealed several points of separation along the elevator control tube and elevator torque tube assembly. The weld area between the left side elevator torque tube and the left elevator horn was fractured, and the fracture surfaces showed large areas of preexisting weld anomalies, including lack of fusion and incomplete penetration. Similar weld anomalies were present between the right elevator components. The examinations determined that incorrect weld filler metal was used. The loads that caused the separation of the left elevator torque tube were likely high but within the design specifications, and the separation likely resulted from the loads being applied to the poor quality welds, which appeared to have occurred during original manufacture.

Text from the NTSB. Open the NTSB docket for CEN13LA225 for the full record.