20241210018949A

ON DECEMBER 10, 2024, AT APPROXIMATELY 1210 PST, A 2008 EUROCOPTER/AIRBUS AS350B2, ^PRIVACY DATA OMITTED^ AIR SUPPORT DIVISION, WAS INVOLVED IN AN INCIDENT DURING A TRAINING MANEUVER AT LOS ALAMITOS ARMY AIRFIELD (KSLI) IN LOS ALAMITOS, CA. THE AIRCRAFT WAS CONDUCTING A SIMULATED HYDRAULIC CONTROL FAILURE EXERCISE WHEN IT ROLLED ONTO ITS SIDE WHILE ATTEMPTING TO LAND. BOTH THE INSTRUCTOR AND TRAINEE PILOTS SUSTAINED ONLY MINOR INJURIES AND WERE ABLE TO EXIT THE AIRCRAFT UNAIDED.

THE INVESTIGATION INTO THE INCIDENT COMMENCED THE FOLLOWING DAY, DECEMBER 11, 2024. AT 0856 PST, THE LOS ALAMITOS AAF AIRPORT OPERATIONS DEPARTMENT WAS CONTACTED AND SUBSEQUENTLY REFERRED THE MATTER TO THE BASE SAFETY OFFICER, WHO WOULD LEAD THE INVESTIGATION. A VOICEMAIL WAS LEFT FOR THE SAFETY OFFICER AT 0858 PST REQUESTING FURTHER DETAILS. EFFORTS TO CONTACT THE ^PRIVACY DATA OMITTED^AIR SUPPORT DIVISION’S MAINTENANCE HANGAR AT 0906 PST WERE UNSUCCESSFUL AT THAT TIME, BUT THE ^PRIVACY DATA OMITTED^ AIR SUPPORT DIVISION’S SAFETY OFFICER WAS LATER REACHED, WHO PROVIDED A NARRATIVE OF THE EVENTS AND CONTACT DETAILS FOR NTSB INVESTIGATORS.

THE INCIDENT OCCURRED DURING A PRIMARY TRAINING FLIGHT, DURING WHICH THE TRAINEE PILOT, SEATED ON THE RIGHT, CLIMBED THE HELICOPTER TO PATTERN ALTITUDE. AT THIS POINT, THE INSTRUCTOR PILOT, SEATED ON THE LEFT, ENGAGED THE HYDRAULIC TEST MODE TO SIMULATE A HYDRAULIC FAILURE. AFTER RECOGNIZING THE CORRESPONDING INDICATIONS, THE TRAINEE PILOT ESTABLISHED A SAFE HYDRAULIC FAILURE SPEED. THE INSTRUCTOR THEN RESTORED NORMAL HYDRAULIC CONDITIONS, AFTER WHICH THE TRAINEE FULLY ISOLATED THE HYDRAULIC SYSTEM USING THE HYDRAULIC CUTOFF SWITCH ON THE COLLECTIVE PITCH LEVER, AS OUTLINED IN THE ROTORCRAFT FLIGHT MANUAL (RFM).

THE HELICOPTER THEN PROCEEDED TO LAND ON RUNWAY 4R. UPON GROUND CONTACT, THE HELICOPTER BEGAN DRIFTING LEFT AND BRIEFLY BECAME AIRBORNE AGAIN. THE INSTRUCTOR PILOT IMMEDIATELY TOOK CONTROL, APPLIED POWER TO ATTEMPT A TAKEOFF, BUT THE HELICOPTER IMPACTED THE GROUND AND ROLLED ONTO ITS SIDE. BOTH PILOTS EXITED THE AIRCRAFT AND SUFFERED ONLY MINOR INJURIES. THE INSTRUCTOR PILOT ACCEPTED RESPONSIBILITY FOR THE INCIDENT.

METEOROLOGICAL CONDITIONS AT THE TIME WERE DOCUMENTED THROUGH METAR AND TAF DATA FROM KSLI. THE RELEVANT METAR AND TAF DATA FOR ONE HOUR BEFORE, DURING, AND ONE HOUR AFTER THE EVENT ARE AS FOLLOWS:

METAR KSLI 102155Z 20006KT 10SM FEW250 24/M14 A3019 RMK AO2A SLP226 T02371142=

METAR KSLI 102055Z 22009KT 10SM FEW050 FEW250 23/M13 A3021 RMK AO2A SLP233 T02301131 57025=

METAR KSLI 101955Z 07012KT 10SM FEW050 25/M28 A3023 RMK AO2A SLP240 T02451280=

TAF DATA INCLUDED:

TAF AMD KSLI 102135Z 1021/1203 VRB06KT 9999 SKC QNH3003INS TX19/1100Z TN08/1116Z=

TAF KSLI 102100Z 1021/1203 VRB06KT 9999 FEW050 FEW250 QNH3003INS TX19/1100Z TN08/1116Z=

DURING A SIMULATED HYDRAULIC FAILURE MANEUVER, THE AIRCRAFT WILL EXHIBIT A TENDENCY TO DRIFT LEFT DUE TO THE AERODYNAMIC FORCES EXERTED BY THE TAILROTOR. THE IP STATED THAT AS THE AIRCRAFT DRIFTED TOWARD THE EDGE OF THE RUNWAY, THEY TOOK IMMEDIATE CONTROL TO PREVENT IT FROM VEERING OFF THE RUNWAY. THIS WAS DONE WITHOUT HYDRAULIC ASSISTANCE TO THE CONTROLS. THE ABSENCE OF HYDRAULIC POWER, COMBINED WITH THE POSSIBLY PRESET PITCH IN THE COLLECTIVE, CONTRIBUTED TO THE AIRCRAFT BECOMING AIRBORNE. THE RAPID INCREASE IN POWER AND THE LIMITED TAILROTOR CONTROL CAUSED A LEFT YAW, RESULTING IN THE AIRCRAFT STRIKING THE RIGHT LANDING GEAR SKID AND SUBSEQUENTLY ROLLING OVER.

THE IP ALSO NOTED THAT THE ^PRIVACY DATA OMITTED^ DEVIATES FROM THE HYDRAULIC FAILURE SIMULATION PROCEDURE AS OUTLINED IN SUPPLEMENT 7 OF THE AIRBUS AS350 ROTORCRAFT FLIGHT MANUAL (RFM) AND AIRBUS HELICOPTERS SAFETY INFORMATION NOTICE NO. 3246-S-29.