Incident Overview
On December 13, 2020, at about 1250 Pacific standard time, a Cessna 172, registration N5098E, was substantially damaged when it overran the departure end of runway 28R and struck an airport perimeter fence near San Diego, California. The flight instructor and student pilot were not injured. The aircraft was being operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.
Flight Sequence
According to the flight instructor, the purpose of the flight was for the student to practice touch-and-go landings. During the second takeoff on runway 28R, as the airplane reached an altitude of about 100 to 150 feet above ground level, the instructor detected a loss of engine power and assumed control of the aircraft. He landed the airplane on the remaining runway, but it overran the departure end and collided with the perimeter fence.
Postaccident Examination
A Federal Aviation Administration inspector examined the airplane and found that both wings and the fuselage had sustained substantial damage. Subsequent examination of the engine revealed that the No. 3 cylinder's intake shroud tube was bent. When the No. 3 cylinder's rocker box cover was removed, the exhaust valve rocker arm stud was found to have separated. The exhaust valve rocker arm seat, rocker arm, washer, and a section of the stud with a self-locking nut were loose within the rocker box cover. Fretting was observed at the mating surfaces for the rocker arm seat, the rocker arm seat, the shroud tube, and the push rod assembly.
Metallurgical Analysis
The separated rocker arm stud was sent to the National Transportation Safety Board Materials Laboratory in Washington, DC, for examination. The fracture surface displayed characteristics consistent with a fatigue fracture. A review of maintenance records did not reveal whether the stud had ever been replaced or inspected during the last major overhaul.