Amateur-built Cavalon N477AG accident near Roseburg, Oregon

Probable cause

A substantially unweighted rotor system for reasons that could not be determined, which resulted in contact between the main rotor blade and the gyrocopter’s keel tube and a loss of control and impact with terrain.

NTSB analysis

The pilot departed an airport on a cross country flight and had flown about 7 miles before witnesses observed the aircraft flying between 1,000 ft to 2,000 ft above ground level (agl), at which time they also heard the engine make an unusual noise as if something had come off the aircraft. They subsequently observed the gyrocopter enter an uncontrolled descent and impact terrain. One of the witnesses observed parts coming off the gyrocopter, which he believed was either the engine or the transmission coming apart. He also observed the “tail boom” break off, swing forward, and crash into the passenger side of the cockpit, which sent it into an uncontrollable spin and subsequent impact with terrain at about a 45° nose-down attitude.

A postaccident examination of the gyrocopter revealed that the keel tube had signature strike marks consistent with a main rotor blade impact. This physical evidence was indicative of a substantially unweighted rotor system. This would have occurred while the aircraft was nosed over for a long period of time, at which time the rotor likely lost its directional orientation and spun out of axis and struck the keel tube. However, the duration of any nose over made by the gyrocopter during the accident flight could not be determined due to a lack of available evidence. The parts that departed the gyrocopter inflight were not identified during the investigation.

Text from the NTSB. Open the NTSB docket for WPR20LA155 for the full record.