Saginaw, TX, USA
N8297P
PIPER PA-34-200T
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.
On November 17, 2009, approximately 0745 central standard time, a Piper PA-34-200T Seneca, N8297P, registered to and operated by the pilot, was substantially damaged during a forced landing near Saginaw, Texas. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 without a flight plan. The pilot, the sole occupant on board, was not injured. The flight had just originated from Hicks Field (T67), Fort Worth, Texas, and was en route to Arlington Airport (GKY), Arlington, Texas. The pilot told FAA inspectors that he took off but did not engage the autopilot. He 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 back 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. Examination of the cockpit revealed all circuit breakers were closed and the master switch had been secured. The airplane was recovered to Air Salvage of Dallas where, on December 3, 2009, it was examined by FAA and Piper officials. The pilot said the two autopilot units had been recently overhauled but "had not been aligned." According to Piper Aircraft, neither the autopilot nor the trim switch wiring were factory-installed. The pitch trim drum inner shaft was found to be in the full nose down position. The flight computer, trim servo, directional gyro, flight command indicator, pictorial navigation indicator, and control yoke were removed and sent to Honeywell in Olathe, Kansas, where, on January 13, 2010, they were examined and functionally tested. According to Honeywell's report, "No defects were observed during this inspection which [would] explain why the aircraft's pitch trim was found in the full nose down position." According to Piper, the airplane was equipped with a KFC-200 autopilot system and a KI-256 flight director. The original control yoke trim switch had been removed and a replacement switch had been installed. The switch wiring was not the original wiring and did not correspond to the original color codes on the wires. Whoever installed the switch had written the wire colors on pieces of masking tape and wrapped them around the wires. According to Honeywell, one of the wires was pinched and pressing on the switch wafer stack. Tests were inconclusive as to whether this may have caused an internal short in the switch. In an e-mail to this investigator, the Piper representative wrote: "When I spoke to [Honeywell, they] indicated that the chafing probably wasn’t an issue but the wire being pinched and pressing on the switch wafer stack might have caused an internal short in the switch."
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.
Source: NTSB Aviation Accident Database
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