What happened
On December 21, 2022, at approximately 16:20 local time, a commercial pilot was conducting an aerial advertising flight (perifoneo) over Puerto Montt, Chile. Shortly after departing from Aeródromo Marcel Marchant (SCPF), the pilot heard an unidentified cracking noise. Although engine parameters remained within normal operating ranges, the pilot decided to return to the airfield as a precaution.
During the approach to runway 01, the pilot noticed natural light entering the cockpit from the upper section of the cabin. This indicated that the fabric covering on the upper fuselage had separated. The pilot performed a normal landing without declaring an emergency. Upon parking the aircraft, the extent of the damage was confirmed: a large section of the upper fuselage fabric had torn away.
The investigation
The investigation conducted by DGAC Chile examined the aircraft's maintenance history, the pilot's experience, and the physical condition of the airframe. The Piper PA-22-108 had undergone its annual inspection only 37.5 hours prior to the incident, at which time no anomalies regarding the fabric covering were detected. The pilot had also performed a pre-flight inspection on the day of the event without noting any discrepancies.
Investigators analyzed the tear pattern, which originated at the junction between the windshield and the fuselage fabric. The investigation found several longitudinal cuts in the fabric. Once these initial cuts occurred, the aerodynamic forces from the relative wind during flight caused the fabric to peel backward and away from the structure.
Findings
- The primary cause of the incident was the detachment of the upper fuselage fabric due to the degradation of the material's properties.
- The fabric degradation was attributed to natural wear and environmental exposure, specifically including ultraviolet (UV) radiation and fluctuations in temperature.
- The aerodynamic impact of the wind during flight acted as a contributing factor, driving the tearing process once the structural integrity of the fabric was compromised.
- The aircraft's maintenance records and recent inspections were found to be in compliance with approved programs, and no prior mechanical failures were identified.