Accident Sequence
On September 2, 2021, at approximately 1130 Pacific daylight time, a Cessna 172E airplane, registration N3965S, sustained substantial damage in an accident near Enterprise, Oregon. The pilot and passenger on board were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
The pilot reported that after a light touchdown on the center of runway 30, the airplane rolled smoothly on its main wheels for a couple of seconds. As the airplane slowed and the nose wheel contacted the ground, the airplane veered to the left and the nose gear fully collapsed. The pilot applied right rudder and full brakes on the right wheel. The airplane subsequently exited the runway, nosed over, and came to rest inverted.
Aircraft Examination
A Federal Aviation Administration inspector examined the airplane and found substantial damage to the fuselage, vertical stabilizer, and rudder. The nose gear upper torque link had separated from the shock strut, with a section of the upper torque link remaining attached to the shock strut. The two sections of the upper torque link were removed and sent to the National Transportation Safety Board Materials Laboratory for further examination.
Metallurgical Analysis
Examination of the fracture surface of the upper torque link revealed flat areas at the forward ribs. These flat areas originated from the forward edge of the ribs and extended almost to the transition from the ribs to the web of the upper torque link. Using a scanning electron microscope, the flat areas exhibited transgranular features consistent with fatigue cracking. Outside the flat areas, the fracture surface features were characteristic of dimpled rupture from overstress.
Review of the airframe logbook showed no specific entries pertaining to the nose gear torque links.