Accident Overview
On April 8, 2017, about 0750 central daylight time, a Grumman G-164A agricultural airplane, registration N971QC, performed a forced landing near Nome, Texas. The aircraft was operated by Twin County Air-AG, Inc. under 14 CFR Part 137. Visual meteorological conditions prevailed, and no flight plan was filed. The pilot sustained no injuries; the aircraft was destroyed by post-impact fire.
Flight Events
The pilot reported that while conducting spray runs, he noticed a burnt wire smell followed by a low oil pressure indication. He partially opened the cabin door and observed flames. As smoke and fire intensified, the pilot had difficulty seeing but located and closed the engine fuel shut-off valve. The smoke cleared sufficiently for him to select a hay field for the forced landing.
Post-Accident Examination
A Federal Aviation Administration (FAA) inspector noted that after landing, the fire consumed most of the airplane. A review of FAA records revealed that the aircraft's original radial engine had been replaced with a Walter M601E-11 turboprop engine, and later with a Pratt & Whitney PT6A-27 turboprop engine on February 1, 2010.
The FAA inspector reported that the shop holding the supplemental type certificate (STC) for the Pratt & Whitney installation did not perform or authorize the engine installation. The STC required special routing of engine connections and a 5-year replacement interval for fuel lines. Investigators did not receive records indicating that the fuel lines were replaced per the STC. The aircraft's battery had recently been replaced. Extensive fire damage prevented a detailed inspection of the engine installation.