Accident Overview
At 1515 central daylight time on August 6, 2018, a Cessna A188B, registered as N4996R, encountered a total loss of engine power and impacted terrain during an aerial application flight approximately 10 miles north of Sedalia, Missouri. The airplane was destroyed by impact forces and subsequent post-crash fire. The commercial pilot, the sole occupant, sustained minor injuries. The flight was operated by Lloyd Darter Aviation under 14 Code of Federal Regulations Part 137 and was not operating on a flight plan. Visual meteorological conditions prevailed at the time. The local flight had departed from Marshall Memorial Municipal Airport (MHL) in Marshall, Missouri, at about 1430.
Pilot Narrative
The pilot provided a written statement to the Federal Aviation Administration inspector. He reported that during the second pass over an agricultural field, he pulled up and felt a loss of power. He advanced the throttle and mixture controls to full forward but observed no response. He dumped the payload and identified a landing area. While flying at the airplane's best glide speed, he struck a tree short of the intended landing area, causing the airplane to spin to the right. He pulled the control stick back and applied right rudder to maintain an upright attitude before the ground impact. The pilot did not submit the required NTSB Pilot/Operator Aircraft Accident/Incident Report (form 6120).
Examination of the Airframe and Engine
Post-accident examination revealed that the airframe was largely consumed by fire, extending from the empennage to the engine firewall and to the mid-wingspan of both wings. Ground scarring was limited to the airplane's planform, with nose-down crushing. The flaps were found in the retracted position. Neither of the two propeller blades displayed S-shaped bending; they were relatively straight, indicating a lack of torsional forces. The bottom half of the engine case was melted to the accessory section, exposing the crankshaft and accessory gears. The internal engine drive and valve train components were connected, secure, and showed no fractures. Engine accessories were destroyed by fire. Notably, the number four-cylinder fuel line, with its attached adapter leading from the fuel manifold, was loose and could be pulled out by hand. The remaining fuel lines were attached and secure in the fuel manifold. The fuel line, its adapter fitting, and the manifold were removed for metallurgical examination.
Metallurgical Findings
Metallurgical examination at the NTSB Material Laboratory showed that the fuel line and its adapter fitting had separated from the fuel manifold. The adapter featured tapered pipe thread where it would screw into the manifold. No evidence of thread deformation was found on the fitting itself. However, the first few threads of the adapter appeared to contain aluminum material from the fuel manifold. Examination of the threaded port on the fuel manifold for the number-four fuel line revealed deformation and indications of incipient melting of the aluminum housing.