Cessna 172H N1658F accident near El Monte, California

Probable cause

The inflight separation of a section of a propeller blade due to a fatigue crack which resulted in a forced landing.

NTSB analysis

The pilot reported that during the flight, the airplane suddenly vibrated severely followed by a sudden loss of engine power and the appearance of oil on the windscreen. The pilot noticed that the propeller was not rotating along with visible damage to the engine cowling. The pilot initiated a forced landing to a nearby airport and landed uneventfully. Postaccident examination of the airplane revealed that the engine mount was bent, and a portion of one propeller blade had separated in flight.

Examination of the propeller revealed that it exhibited a fracture chordwise across the propeller approximately 12 inches outboard of the center of the propeller hub. The leading-edge area of the fracture exhibited an area of darker coloration and smoother surface texture along with fracture features consistent with progressive crack growth on the fracture surface in the area. The signatures were consistent with a fatigue fracture originating at the leading edge of the propeller

Text from the NTSB. Open the NTSB docket for WPR20LA062 for the full record.