SPORTCOPTER VORTEX N634SC accident near Viroqua, Wisconsin

Probable cause

The noncertificated pilot's loss of control of the gyrocopter after a total loss of engine power due to seizure of the crankshaft bearings. Contributing to the accident were the insufficient maintenance of the engine and the pilot's lack of gyrocopter flight experience.

NTSB analysis

The noncertificated pilot was conducting taxi operations in a gyrocopter at the airport. A witness near the airport stated that the aircraft became airborne and then turned and descended rapidly. A second witness near the airport stated that he heard the engine running and then quit suddenly, with no sputtering. A third witness heard the impact and saw smoke rising from the field.

The main rotor blade had separated at the shaft near the main rotor hub and was one of the first pieces of wreckage located within the ground scar. The flywheel contained dirt and debris embedded on one side, consistent with a near vertical ground impact with no rotation of the main rotor. A postaccident engine examination revealed that all of the crankshaft bearings were seized in place and that a foreign substance in all bearings was congealed, consistent with exposure to high heat. When the engine case was separated, circumferential scarring was present on both sides of the case corresponding to the No. 1 (most forward) bearing, consistent with a spun bearing and lack of oil around the bearing journal It is likely that, based upon these findings, the engine seized in flight.

No maintenance records were located during the investigation. Additionally, the previous owner had not started the engine or performed any maintenance on it. A photograph that the previous owner provided showed the tachometer displaying 122 hours about 5 months before the accident.

According to the engine maintenance manual, a 100-hour inspection should include, among other tasks, an inspection of the cylinder head and piston crown and an inspection of the piston rings for movement. A general overhaul of the engine was to be completed every 5 years or 300 hours, whichever came first. Based upon the serial number, the engine was produced in 2002.

Given the findings from the engine examination and the statements from the previous owner, it is unlikely that the engine had ever been overhauled or inspected in accordance with the engine maintenance manual. Had the required maintenance been performed, it is likely that the signs of a lubrication issue would have been revealed.

Further, the pilot's lack of flight experience in the aircraft likely contributed to the loss of control after the engine failure. The pilot’s logbooks indicated that he had logged less than 20 hours of total gyrocopter flight experience, of which only 3.5 hours occurred in 2019. It is likely, based upon this lack of experience, the pilot was not prepared for an engine failure to occur, and likely did not possess the aeronautical knowledge or skills required to appropriately respond to such an event, leading to a loss of control in flight.

Text from the NTSB. Open the NTSB docket for CEN19FA276 for the full record.