Accident Overview
On December 21, 2023, at approximately 1210 Pacific standard time, a Mooney M20J airplane, registration N2073K, was substantially damaged during a forced landing near Carlin, Nevada. The pilot and the passenger sustained minor injuries. The flight was operated as a personal flight under 14 Code of Federal Regulations Part 91.
Pilot Report
The pilot reported that before departing from Redding Municipal Airport (RDD), Redding, California, he topped off the fuel tanks. The intended destination was Glendale Municipal Airport (GEU), Glendale, Arizona. About two hours into the flight, the airplane climbed from 11,500 ft to 13,500 ft mean sea level, and the pilot configured the trim, fuel mixture, and power for cruise flight with the fuel selector positioned to the left tank.
Approximately 20 minutes later, the pilot heard a loud clunk from the engine, followed by strong vibrations and the smell of engine oil. He activated the fuel boost pump, moved the fuel selector to the right tank, turned left toward the northwest, and declared an emergency with the Salt Lake City Center ARTCC controller. Shortly after, the engine lost all power. Attempts to restart the engine were unsuccessful. The pilot selected a suitable landing site and performed an off-airport, gear-up forced landing in mountainous terrain, about 9 miles south of Carlin. The airplane sustained substantial damage to the outboard section of the right wing. The pilot did not recall the manifold pressure or engine rpm before the power loss.
Magneto Examination
The single-drive dual magneto was found securely clamped at its mounting pad. The magneto impulse coupling clicked near top dead center during crankshaft rotation. However, magneto-to-engine timing could not be confirmed using a timing synchronizer box, which did not produce the expected audible tone indicating that either magneto contact assembly was open. The magneto produced no spark at any ignition lead and was removed for further examination.
Upon removal of the distributor housing, neither contact assembly was functioning. The contacts did not appear burnt, the plastic cam follower foot was intact and showed no heat distress, and there was no evidence of mechanical malfunction of the internal gears. The wiring inside the magneto appeared normal, and the cap internal surfaces and wires had no oil residue or signs of arcing.
When the magneto drive was rotated by hand with power supplied, neither the left nor right contact assembly cam follower engaged the main breaker point frame bracket. After manually separating the main breaker point from the retard breaker point, the right magneto produced an audible tone and the green light illuminated, but the left magneto did not.
Bench Testing
The magneto was shipped to the manufacturer for bench testing. The initial bench test showed that the right magneto produced a spark at each of the four ignition leads, while the left magneto produced no spark. Further examination of the distributor housing revealed that the right magneto cam follower was engaging the cam, allowing the contact assembly breaker points to open when the cam lobe lifted the cam follower and frame bracket. The left magneto cam follower was not engaging the cam.
The engine manufacturer's High Tension Magneto Service Support Manual provided instructions for adjusting the assembly frame bracket for breaker point clearance. The left main contact clearance should be 0.016 inch (±0.002), and the retard contacts should have 0.016 inch (±0.004) clearance. The contact assembly frame bracket was adjusted to increase breaker point opening clearance, and the magneto drive and distributor housings were reassembled. A second bench test showed that both the left and right magnetos produced electrical impulses to each designated ignition lead in firing order (1, 3, 4, 2). The left main contact opening clearance was not measured before or after the bench test.
Maintenance Records
A review of the airplane's maintenance logs indicated that the magneto-to-engine timing was checked during the last annual inspection. However, a definitive magneto service history could not be determined.