On July 9, 2017, at 1309 mountain daylight time, a Cub Crafters CC11-160 airplane, N111JW, was substantially damaged during a forced landing following a loss of engine power during cruise flight near Milesville, South Dakota. The pilot sustained minor injuries. The airplane was registered to and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Day visual meteorological conditions prevailed. The flight was not operated on a flight plan. The flight originated from the Aberdeen Regional Airport (ABR), Aberdeen, South Dakota, at 1109, with an intended destination of the Rapid City Regional Airport (RAP), Rapid City, South Dakota.On the day of the accident, the pilot departed the Harry Stern Airport (BWP), Wahpeton, North Dakota at 0904 and arrived at ABR at 1036. The pilot reported that airplane was "topped off" at ABR before he departed for RAP. Due to stronger than anticipated head winds, he decided to divert to the Philip Airport (PHP), Philip, South Dakota, to maintain an adequate fuel reserve. Shortly afterward, while the airplane was in cruise flight, the engine "abruptly stopped, [with] no coughing or sputtering." He verified that the fuel selector was set to both. Each fuel tank appeared to have one-quarter tank remaining. His attempts to restart the engine were not successful and he executed a forced landing to an open field. He noted that the airspeed might have decayed on final approach resulting in an inadvertent aerodynamic stall and hard landing. The airplane sustained substantial damage to the fuselage and both wings. The main landing gear collapsed.

A postaccident examination engine test run was conducted by FAA inspectors, with the assistance of technical representatives from the airframe and engine manufacturers. The engine remained attached to the airframe. The carburetor was displaced aft but appeared otherwise intact. A small oil leak was observed at the sump near the carburetor. The fuel tanks contained fuel, and positive fuel flow to the carburetor was confirmed. Both fuel caps appeared to be secure. No evidence of in-flight fuel leakage or a fuel system obstruction was observed. The one electrical lead from the ignition module was disconnected; however, it could not be determined if that occurred in-flight or as a result of the accident sequence.

The engine was run on the airframe using an external fuel supply plumbed directly to the carburetor fuel inlet. The disconnected ignition lead was reattached before the run. The engine started on the first attempt and ran at 1,120 rpm. The test run was limited to 7 seconds due to the oil leak. A second test run with a duration of 29 seconds was completed; the engine ran at ,1510 rpm. The cylinder head and exhaust gas temperatures increased normally. No anomalies were observed.

Engine data was recovered from the airplane avionics system; the data was recorded at 1-second intervals. (All time references are with respect to the local time at the accident site – mountain daylight time.) The initial data point related to the accident flight was recorded at 1105:56. A loss of engine speed occurred about 1307:40, and routine 1-second data continued until 1309:10. Data resumed at 1309:50 and included a notation "powerup." This is consistent with an interruption of electrical power during the restart attempt. The final data point was recorded at 1309:59. The accident flight duration, from initial power-up of the avionics before takeoff until the loss of engine power and the restart attempt was 2 hours, 3 minutes, and 14 seconds (2.054 hours).

A review of the data revealed that the engine indications were normal until about 1254. Over the next 4 minutes, the engine fuel flow varied from about 3.7 gph to 7.3 gph. The remaining engine parameters remained within normal operating limits during this time. The fuel flow returned to approximately 5.9 gph for the following 4 minutes; the remaining engine parameters appeared stable. About 1304, the fuel flow became erratic, ranging from 2.3 gph to 7.6 gph, and ultimately decreasing to zero. The corresponding parameters including engine speed, oil pressure, exhaust gas temperature, and cylinder head temperature also decreased at that time.

Based on the average fuel flow of 5.89 gph for the accident flight, the calculated fuel consumption since refueling was 12.10 gallons. The pilot reported a total useable fuel capacity of 24 gallons. As previously noted in this report, he stated that the fuel tanks were "topped off" before the accident takeoff.