What happened
During flight, the VHF COM 1 antenna became detached from the aircraft. The separation was preceded by a whistling sound, followed by the sound of an impact. While investigators considered the possibility of a birdstrike or a collision with a remotely piloted aircraft (RPA), there was no visual evidence of such an event, and the altitude of the occurrence made a birdstrike or RPA encounter unlikely.
The investigation
Investigators examined the remains of the antenna base and discovered traces of aluminium oxide and chlorine. Because the antenna base is intended to be a fully sealed unit, the presence of these substances indicates that moisture had penetrated the component. The investigation noted that much of the antenna was not recovered, making it difficult to pinpoint the exact pathway for this moisture ingress.
Evidence showed that the seal surrounding the base had separated from the top half of the antenna. While moisture was found beneath certain sections of the seal, it remains unclear if this moisture entered through a compromised seal or was already present within the unit. The investigation also noted that the antenna had cracked around its six fastener holes. It is possible that corrosion weakened the bond between the antenna's skin and its polyurethane core, or that moisture absorption within the glass fibre composite skin reduced the unit's structural strength, leading to cracks during flight-induced flexing.
Findings
- The VHF COM 1 antenna failed and separated from the aircraft due to pre-existing damage caused by moisture ingress.
- Corrosion was present on the antenna base, evidenced by the discovery of aluminium oxide and chlorine.
- The antenna exhibited cracking around the six fastener holes.
- It could not be determined if the damage would have been detectable during the inspection conducted eight months prior to the event, as the damage may have been too small or hidden by paint.