CEN16LA227

The commercial pilot reported that he had just completed a cross-country flight and had been cleared for the approach when, during the descent, the engine did not respond when he pulled back on the throttle. When the pilot enriched the fuel/air mixture, the manifold pressure decreased, and the engine lost power. The pilot conducted a forced landing to a field, during which the airplane's wing sustained substantial damaged. The examination of the engine revealed that the throttle control arm, which was original hardware to the airplane, was separated from the joint assembly. Additionally, the female end of the throttle arm exhibited elongation at the linkage attachment point and was consistent with wear developing over time. An examination of the airplane, engine, and remaining systems revealed no other anomalies that would have precluded normal operation. The airplane manufacturer had issued a nonmandatory service letter (SL) recommending that the throttle arm and joint assembly be replaced with a new refinement kit if any indication of wear existed; a review of the engine logbooks found no record of compliance with the SL. Although the pilot reported that the airplane's last inspection was an annual inspection, he did not provide the date of the inspection, and it was not noted in the logbook. Given the condition of the throttle linkage attachment, it is likely that the inspection of the throttle linkage attachment was either not performed or was inadequate. Investigators were unable to determine what the exact state of the throttle arm was at the last inspection.

On June 19, 2016, about 2045 central daylight time, a Piper PA 28R-200 airplane, N9336N, was substantially damaged during a forced landing to a field near Bowie, Texas. The commercial pilot and two passengers were not injured. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 on an instrument flight rules flight plan. Night visual meteorological conditions prevailed for the personal flight. The flight departed Epply Airfield (OMA), Omaha, Nebraska, about 1615 and was en route to Bowie Municipal Airport (0F2), Bowie, Texas. According to the written statement submitted to the National Transportation Safety Board (NTSB) by the pilot, he had been cleared for the RNAV 17 approach to 0F2 with a descent to 4,000 feet mean sea level (msl). The pilot reported that he "pulled back the throttle with no response from the engine." He reported the situation to air traffic control but stated that it was manageable and did not declare an emergency. About four miles from the airport the pilot enrichened the engine's fuel/air mixture at which time the manifold pressure decreased and the engine lost power. A line of trees and a small lake were in front of the flight path so the pilot elected to perform a forced landing towards a road and open field. According to the Federal Aviation Administration (FAA) inspector who responded to the accident, the airplane's right wing sustained substantial damage during the forced landing. And examination of the engine found that the throttle control arm was separated from the joint assembly. Further examination revealed that the throttle control arm was original hardware to the airplane (part number 31747-00). The female end of the throttle arm exhibited elongation at the attachment point. An examination of the airframe, engine, and remaining systems revealed no other anomalies that would have precluded normal operation. Piper Aircraft Corporation service Letter No. 747, titled 'Inspection of Throttle and Mixture Control Attachments', dated May 28, 1975, recommends that the throttle arm and joint assembly be replaced with a new refinement kit if any indication of wear existed. The Service Letter noted "careful inspection of throttle and mixture control attachments is normal maintenance and is a requirement of both standard Piper Period Inspections and the Piper Program Inspection Procedures." According to the FAA inspector, he examined the logbooks and found no record of compliance with this service letter. According to the accident report form submitted by the pilot, the last inspection performed was an annual type; however, no date for that inspection was provided. Investigators were unable to determine why the service letter was not complied with or what the exact state of the throttle arm was at the last inspection.