Accident Details
On June 18, 2021, about 1832 eastern daylight time, a Cessna 172N, registration N2797E, was involved in an accident near Jupiter, Florida. The airplane was being operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. According to the Federal Aviation Administration (FAA), approximately 10 minutes after takeoff, while at 2,700 ft mean sea level, the engine experienced a total loss of power. The flight instructor was unable to restart the engine and attempted to land on a grass field. The airplane overflew the field and collided with a fence and trees before coming to rest nose-down in a creek.
Damage and Injuries
The airplane was substantially damaged. The flight instructor sustained serious injuries, and the student pilot sustained minor injuries. Due to his injuries, the instructor could not provide a statement. Attempts to contact the student pilot were unsuccessful.
Engine Examination
An examination of the wreckage by an FAA inspector and a representative from the airframe manufacturer revealed oil streaks along the fuselage. Further examination showed that the single-drive, dual output magneto had separated from the rear accessory section of the engine. The nuts, clamps, and lock washers that secured the magneto to the studs were not recovered, and the studs did not exhibit any stripping or damage to the threads. Cuts in the magneto housing were consistent with vibration over time, possibly due to tightening at an angle between the two studs.
Maintenance History
A review of maintenance records indicated that the magneto was serviced on March 4, 2021, and the airplane’s most recent annual inspection was completed on May 17, 2021. The airplane had accumulated about 215 hours since the magneto service and 74 hours since the annual inspection. A 100-hour inspection was also performed on April 9, 2021.
The mechanic who serviced the magneto on March 4 stated that he did so as part of a pre-buy inspection. He advised the seller that an applicable Airworthiness Directive (AD) had been superseded, but was requested to perform the original AD anyway to satisfy the buyer. The original AD required a 500-hour inspection of the magneto impulse couplings. The mechanic removed and reinstalled the magneto, using used clamps and nuts but new lock washers. He noted no defects at the time.
The mechanic who performed the annual inspection on May 17 stated that, when the magneto was previously removed and replaced, the earlier mechanic would tighten its two steel nuts with star lock washers using a torque wrench. During the annual inspection, he followed the Part 43 checklist, which does not specifically include magnetos, but he manually checked that the magneto was secure by attempting to wiggle the accessories. The Cessna checklist includes magnetos, but its use is at the operator's discretion due to increased labor and cost.