Incident Summary
A night instrument instruction flight was in progress at an altitude of 9,000 feet, operating under visual flight rules on top of a cloud layer. During the flight, the left half of the top engine cowling detached from the aircraft and became lodged on the horizontal stabilizer. The aircraft subsequently exhibited handling difficulties and was unable to maintain level flight. The flight instructor and student pilot elected to divert to a nearby airport, where they executed an uneventful landing.
Examination Findings
An inspector from the Federal Aviation Administration (FAA) examined the aircraft following the incident. The inspector noted that the left cowl pin was missing, but determined that the pin did not fail; instead, it had been torn away along with the surrounding cowling material. No other damage or failures were reported.
Maintenance Observations
The manager of the repair facility where the aircraft had been maintained provided additional insight. He stated that during prior maintenance, he had observed worn side latches and pin grommets on the upper cowling. These worn components allowed the upper cowl pin to slide out of the lower pin hole, which in turn could permit airflow to separate the upper cowling from the aircraft. The source did not indicate whether any corrective action was taken before the incident.
Industry Records
According to the source, there were no prior FAA malfunction or defect reports of a similar cowling failure. Additionally, the aircraft manufacturer did not have records of any previous failures of this nature.