Incident Overview
During a routine maintenance inspection, an aircraft mechanic discovered substantial structural damage to the airplane's firewall. The operator reported that the damage was not externally visible and could not have been detected during a preflight inspection.
Investigation Findings
The circumstances surrounding the damage remain uncertain. The operator stated she does not know when, where, or who caused the damage. According to the operator, three individuals flew the airplane after its most recent 100-hour inspection. All pilots and their previous passengers reported uneventful flights and landings, and no witnesses have provided contradictory accounts.
The date, time, and location used for the official record are taken from the airplane's last flight for computer entry purposes only. A determination was not made regarding the identity of the pilot(s) that caused the damage. The aircraft's occupants at the time of the damage are unknown, and it is presumed that there were no injuries.