What happened
On November 8, 2016, a PZL-SW4 helicopter, registration PP-MHJ, was conducting a local flight from the Dolores helipad in Rio Negrinho, Santa Catarina, to demonstrate the aircraft to a prospective buyer. The flight included the pilot and two passengers.
While the aircraft was leveled at 500 feet and traveling at approximately 80 knots, a passenger alerted the pilot that the right upward vision window had detached from the airframe. The pilot immediately initiated a return to the departure helipad. The aircraft landed without further incident, resulting in minor damage to the airframe. No injuries were reported among the crew or passengers.
The investigation
CENIPA investigators examined the maintenance history of the aircraft, specifically focusing on a recent inspection performed on October 10, 2016. This inspection included the replacement of the upward vision window.
Laboratory analysis of the residue left in the window frame revealed that the maintenance shop had used Essex U-438RF sealant instead of the Betaseal 1407 sealant specified in the manufacturer's maintenance manual. While the shop claimed the substitution was due to local market unavailability and believed the products were equivalent, chemical analysis showed differences in composition between the two substances. Furthermore, investigators found that the maintenance team had not verified the successful cure of the adhesive and that there were no records confirming that the specific application distances, fixations, and timing intervals required by the manual had been strictly followed.