Accident Overview
On January 15, 2019, about 1050 mountain standard time, a Piper PA-28-140 airplane, registration N1697J, was substantially damaged when it was involved in an accident near Salt Lake City, Utah. The commercial pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
Accident Sequence
The pilot reported that he was practicing touch-and-go landings. While on landing approach, he reduced the throttle control to decrease engine rpm; however, the engine remained at 2,200 rpm. He then pushed the throttle back in and the power increased to 2,500 rpm. He attempted to reduce throttle again, but the engine remained at 2,500 rpm. The pilot initiated a go-around, and, shortly thereafter, engine power decreased from 2,500 to 1,500 rpm. With no usable runway remaining, the pilot performed a forced landing to a road, during which the propeller struck the road and the landing gear sheared off the airplane.
Examination Findings
The service manual for the Marvel-Schebler Model MA4 series carburetor lists a castellated nut and cotter pin to secure the serrated throttle arm to the throttle shaft of the carburetor. Examination of the engine revealed that the carburetor serrated throttle lever locking nut was finger-tight and the cotter pin was absent. When the throttle lever was retracted and extended, the loosely attached throttle shaft did not move. Postaccident examination of the carburetor at Precision Air Power, Woods Cross, Utah revealed no anomalies that would have precluded normal operation.
Maintenance History
A review of the engine maintenance records revealed that, on December 14, 2018, as part of the annual inspection, the mechanic wrote, "Verified control movement and lubricated." In an interview with a Federal Aviation Administration representative, the mechanic confirmed that he took the throttle cable off to do this work.