N226SA

On June 18, 2022, about 1710 central daylight time, a Eurocopter Deutschland Gmbh EC-135 P2+ helicopter, N226SA, sustained substantial damage when it was involved in an accident near Waukesha, Wisconsin. The pilot and 3 passengers were not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 135 air medical flight.

According to the operator, the pilot received a flight request for an inter-facility transfer flight. The intended route of flight was from the aircraft's primary base at Waukesha County Airport (UES) to pick up a patient at Aurora Lakeland Medical Center, Elkhorn, Wisconsin, and transport them to Children's Hospital of Wisconsin, Milwaukee, Wisconsin. After departing from UES when the helicopter about 150 ft agl, the pilot heard a thump, and the helicopter pitched up. The pilot immediately executed an emergency landing, and all occupants exited the helicopter uninjured. The pilot had full control of the helicopter during the emergency landing. The helicopter sustained substantial damage to the fenestron blades.

The accident site was situated over a large area adjacent to a concrete ramp and taxiway. The fairing cover was missing from fenestron assembly. Debris was found about 600 ft in all directions. The debris consisted of fenestron fairing (hub cover) fragments, composite fragments from the fenestron body, attachment bolts, and brackets. Some debris was found on top of a one-story hangar rooftop. Small fragments of the fairing cover were found scattered on the ramp and the top of the one-story hangar. Larger fragments of the fairing cover were found wedged between the fenestron housing and the fenestron blades. The fairing fragments that were found showed damage consistent with ingestion into the rotating blades of the fenestron. There was no evidence of a bird strike present. After an extensive search of the accident area, investigators were unable to identify any foreign debris that might have come into contact with the cover before its separation. Other than the fenestron fairing cover and fenestron housing, the entire helicopter (airframe and engine) had no other damage or missing hardware/components.

The fenestron blades within the fenestron housing were found attached with no evidence of malfunction. The fenestron blades and the inside of fenestron housing were impact damaged, consistent with ingestion of the fragments from the fenestron fairing cover. No evidence of preaccident malfunctions of the fenestron housing, blades, gearbox, or drive were found. No improper maintenance anomalies were found with the fenestron assembly.

Along with multiple fragments of the fenestron fairing cover, five of the fenestron fairing cover attachment bolts were found attached to their respective brackets, and all were torqued. A sixth bolt was not found; however, a portion of the sixth bolt’s bracket was found embedded in a faring cover fragment, consistent with the bolt being attached before the accident. All faring cover attachment hardware was accounted for and showed no evidence of preaccident material failure.

On an exemplar fenestron assembly, a security test of the fenestron fairing cover was conducted with various combinations of retaining bolts and clips. The fairing cover was attached to the exemplar fenestron assembly with six attachment bolts, brackets, and anchors. The hub cover was secure. Two of the bolts were removed, and the fairing cover remained secure. Two more bolts were removed, and with only two bolts remaining, and the fairing cover remained secure.

The helicopter flew about 5.8 hours without incident after the most recent maintenance of the fenestron. Since the fenestron maintenance, numerous daily maintenance checks and pilot prefights were conducted, with no unresolved items or anomalies. No uncorrected maintenance anomalies were found in the maintenance logbooks.

There were six historical events involving the fenestron faring cover separating from the same model helicopter. All six events were related to FOD ingestions that caused the fenestron fairing cover to separate.