N4996RCessna A188B · 1975

On August 6, 2018, at 1515 central daylight time, a Cessna A188B, N4996R, experienced a total loss of engine power and impacted terrain during an aerial application flight about 10 miles north of Sedalia, Missouri. The airplane was destroyed by impact forces and post-crash fire. The commercial pilot sustained minor injuries. The airplane was registered to an individual and operated by Lloyd Darter Aviation under Title 14 Code of Federal Regulations Part 137 as an aerial application flight that was not operating on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The local flight originated from Marshall Memorial Municipal Airport (MHL), Marshall, Missouri about 1430.

The pilot did not submit a National Transportation Safety Board Pilot/Operator Aircraft Accident/Incident Report (form 6120), as required under Part 830.

The pilot provided a written statement to the Federal Aviation Administration Inspector assigned to the accident investigation. The pilot stated that during the second pass over an agricultural field, he pulled up and "felt a loss of power." He stated that he pushed the throttle and mixture controls full forward but there were "no results." He dumped the payload and located a landing area. He said he flew the airplane's best glide speed and struck a tree short of the landing area, spinning the airplane to the right. He pulled the control stick back and applied right rudder to maintain the airplane in an upright attitude prior to impacting the ground.

Post-accident examination of the airplane revealed the airframe was consumed by post-crash fire 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 in the retracted position. Neither of the two propeller blades displayed S-shaped bending and were relatively straight, consistent with a lack of torsion. 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 did not display any fractures. The engine accessories were destroyed by the fire. The number four-cylinder fuel line with an attached adapter leading from the fuel manifold was loose and was pulled out by hand. The remaining fuel lines were attached and secure in the fuel manifold. The fuel line, the fuel line adapter fitting, and the manifold were removed for metallurgical examination at the National Transportation Safety Board Material Laboratory.

The metallurgical examination revealed the fuel line with its adapter fitting were separated from the fuel manifold. The adapter had tapered pipe thread where it would screw into the fuel manifold. Examination of the adapter fitting did not reveal evidence of thread deformation on the fitting. The first few threads of the adapter appeared to contain aluminum material from the fuel manifold.

The threaded port on the fuel manifold for the number-four fuel line exhibited deformation and the appearance of incipient melting of the aluminum housing.