What happened
On June 18, 2022, at approximately 1710 central daylight time, a Eurocopter EC-135 P2+ helicopter, registration N226SA, was performing an air medical inter-facility transfer near Waukesha, Wisconsin. The flight was intended to transport a patient from Waukesha County Airport (UES) to Children's Hospital of Wisconsin in Milwaukee.
Shortly after departing from UES, while flying approximately 150 feet above ground level, the pilot heard a loud thump and experienced a sudden pitch-up of the aircraft. The pilot immediately performed an emergency landing. All 4 occupants (the pilot and three passengers) were not injured.
The investigation
Investigators examined the accident site, which was located near a concrete ramp and taxiway. The investigation revealed that the fairing cover was missing from the fenestron assembly, with debris scattered approximately 600 feet in all directions. Fragments of the fairing cover, composite pieces from the fenestron body, and various attachment bolts and brackets were recovered. Some debris was found on the roof of a one-story hangar.
Analysis of the recovered fairing fragments showed damage consistent with being ingested into the rotating fenestron blades. There was no evidence of a bird strike, and investigators could not identify any foreign object debris (FOD) that might have caused the cover to separate.
Mechanical examination of the N226SA showed that the fenestron blades and the interior of the housing had impact damage consistent with the ingestion of the cover fragments. The blades, gearbox, and drive showed no evidence of pre-accident malfunction. Furthermore, all attachment hardware for the fairing cover was accounted for and showed no signs of material failure or improper maintenance. The helicopter had flown 5.8 hours since the most recent maintenance on the fenestron, and no uncorrected maintenance anomalies were noted in the logs.