Piper PA-34-200T N8297P accident near Saginaw, Texas

Probable cause

The pilot's inability to maintain control of the airplane due to a pinched trim system wire that resulted in a runaway nose-down pitch trim.

NTSB analysis

The pilot said that he took off and did not engage the autopilot, but did use the electric trim switch on the control yoke to establish a climb attitude after takeoff. When he activated the trim switch, the airplane "pitched down rapidly." Despite his application of full up elevator to arrest the descent, the airplane continued to descend. The pilot was forced to make a landing in an open field. During the ensuing forced landing, the airplane sustained substantial damage to both wings and fuselage. The pitch trim drum inner shaft was found to be in the full-nose-down position. Examination of the cockpit revealed all circuit breakers were closed and the master switch had been secured. The flight computer, trim servo, directional gyro, flight command indicator, pictorial navigation indicator, and control yoke were functionally tested and no defects were noted. The original control yoke trim switch had been replaced. The switch wiring was not the original wiring and did not correspond to the original color codes on the wires. The wire colors were written on pieces of masking tape which were wrapped around each corresponding wire. One of the wires was pinched and pressing on the switch wafer stack; according to a representative of the manufacturer the pinched wire pressing on the switch wafer stack could have resulted in a runaway trim condition.

Text from the NTSB. Open the NTSB docket for CEN10LA052 for the full record.