Amateur-built T BIRD II N618ER accident near St Mary'S, Kansas

Probable cause

The loss of engine power due to a propeller failure when the passenger’s hat exited the cockpit and impacted the three-bladed pusher propeller, separating one of the propeller blades.

NTSB analysis

The private pilot and passenger planned on a short flight around the traffic pattern in an open-cockpit, light sport airplane. Shortly after takeoff, as the pilot turned downwind, he heard a "crack," and the engine started to vibrate and lose power. The pilot applied power, but the engine did not respond. He turned sharply left and then tried to stop the turn and descend, but the airplane continued to turn and descend until it impacted terrain. A witness saw two objects fall from the airplane shortly after the engine sound "stopped." Both objects were retrieved. The first object was the passenger's knitted hat, the top of which was "chewed up" and had a line burnt/melted into it. The other object was one of the propeller blades. The accident is consistent with the passenger's hat exiting the cockpit and impacting the three-bladed pusher propeller, which led to the separation of one of the propeller blades and the subsequent loss of engine power.

Text from the NTSB. Open the NTSB docket for CEN18LA027 for the full record.