Accident Overview
On December 12, 2022, at approximately 2005 central standard time, a Mooney M20K, registration N231GZ, was substantially damaged when it struck a power pole during a forced landing near Addison, Texas. The pilot and passenger sustained serious injuries. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Flight History
The flight originated at Abilene Regional Airport (ABI) in Abilene, Texas, and was destined for Addison Airport (ADS) in Addison, Texas. The pilot reported that while being vectored for an instrument landing system approach to runway 16 at ADS, the engine lost all power and the propeller automatically feathered. After an unsuccessful attempt to restart the engine, the pilot aligned the airplane with a road for a forced landing. During the approach, the airplane struck a power pole, resulting in substantial damage to the wings and fuselage. A post-impact fire occurred.
Postaccident Examination
During the postaccident examination of the engine, 12 of the camshaft gear teeth were found either broken or missing, with six teeth recovered from the oil sump. The aircraft owner reported that the maintenance logbooks were in the airplane at the time of the accident and were destroyed by fire, preventing a review of engine maintenance history.
Service Bulletin History
In 2005, Continental Motors issued critical service bulletin (SB) CSB05-8C, which was superseded in 2018 by CSB05-8D. The service bulletin pertained to certain camshaft gear part numbers on specific engines, including the TSIO-520-NB17N and the camshaft gear part number 655516 installed on the accident airplane. The SB required replacement of the camshaft gear with a newer model (part number 656818) during the next 100-hour or annual inspection, citing an increased face circumference of 0.060 inches to prevent possible gear tooth failure. At the time of the accident, the accident airplane still had the old camshaft gear installed. Compliance with this service bulletin is not mandatory for Part 91 operations. Laboratory analysis confirmed that the gear teeth fractured due to fatigue cracks, consistent with the failure mode described in the service bulletin.