On April 10, 2020, about 1225 central daylight time (CDT), a Beechcraft N35, N1258Z, was substantially damaged when it was involved in an accident near Sidney, Iowa. The airline transport pilot and passenger were uninjured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 personal flight.

According to the pilot, the accident flight was the third following an annual inspection. The airplane had flown about 1.5 hours since the completion of the annual inspection and was topped off with fuel prior to the flight. About 80 minutes into the cross-country flight, while in level cruise flight about 4,500 ft above mean sea level (msl), the engine ceased to produce power. The pilot stated that there was no warning, and the engine instruments appeared normal. He attempted to restore power, but when he turned the key to "START," he heard a sound consistent with an attempt to start an already running engine. When he moved the throttle from the cruise setting to idle and then back to the previous setting, the RPM gauge fluctuated. When the airplane descended to 1,500 ft msl, about 1,000 ft above ground level, he began to look for an emergency landing area. He said that it was at this time that he and his passenger began detecting a "slight burning smell."

Unable to reach an airport, he conducted an emergency landing to a grass field. Upon touchdown, the airplane encountered uneven terrain, the nose gear collapsed and the left main gear was compressed up and into the left wing, resulting in substantial damage to the wing.

During a postaccident examination, thumb compression was obtained on all cylinders through rotation of the propeller. The impulse coupler could be heard, consistent with internal continuity from the front to the back of the engine. The spark plugs were removed and appeared intact and undamaged, although the manufacturer of the spark plugs (Champion and BG) and spark plug electrode gaps were inconsistent. The magnetos and wiring harnesses were removed and tested on a bench using a hand drill; spark was observed on all ignition harness leads.

The propeller governor was examined by the NTSB investigator-in-charge. A small amount of unidentified metallic material and debris was found on the oil screen but not within the accessory. The governor was disassembled and found to be unremarkable.

A postaccident examination of the fuel system was accomplished with no anomalies or malfunctions discovered in any components that would have precluded normal operation. Fuel obtained from the gascolator was examined for proper color and the presence of debris or water, with no contamination noted.