NTSB Factual Report

On August 11, 2012, at 1600 central daylight time, a GN-1 Aircamper, N31TM, impacted terrain during a forced landing to a field near Burlington, Wisconsin, after the propeller with its bolts separated from the airplane during cruise flight. The certificated private pilot and a passenger received minor injuries. The airplane sustained substantial damage to the fuselage. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and a flight plan had not been filed for the local flight that departed from Burlington Municipal Airport, Burlington, Wisconsin, about 1500.

According to the Federal Aviation Administration (FAA) inspector who examined the airplane, stated that the pilot shut down the engine two times when the he experienced an in-flight vibration during a local flight. The pilot then landed the airplane on a field. The propeller was found 500 yards from the airplane. The inspector stated that the pilot installed the propeller bolts backwards and they were not properly torqued. The tachometer time at the time of the accident was 607.9 hours.

The FAA inspector gave the pilot two National Transportation Safety Board (NTSB) Accident/Incident Report forms when he met the pilot. The pilot was also sent an NTSB Accident/Incident Report form by the NTSB Investigator-In-Charge. An NTSB Accident/Incident Report was not received from the pilot.

NTSB Probable Cause

The pilot's improper installation of the propeller bolts, which resulted in the in-flight separation of the propeller.