What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
02/22/2022:
At approximately 10:20 HST an S61N, registration # N615CK, privacy data omitted was destroyed on ground impact at barking sands airport. The helicopter was performing a part 133 operation in support of the pacific missile range facility retrieving practice torpedoes from the waters west of the island of kauai. Witness statements shared a similar trend that the aircraft was over the taxiway and everything looked normal and then suddenly the helicopter pitched nose down and crashed.
02/23/2022:
FAA on scene and conducted routine investigative interviews and verified information previously gathered by military personnel, reviewed maintenance records, picture documented the accident site. Crash dispersal indicated a low angle high velocity impact with power to the rotor system due to consistent ground scarring by the main rotor blades. NTSB arrived at end of day and took possession of the accident investigation.
02/24/2022:
Cockpit voice recorder sent to NTSB labs.
Conducted flight control continuity check, conducted powertrain continuity check. Item of interest noted during flight control continuity check, below is an excerpt from my sas activity record:
From the main rotor flight control bellcranks to the primary servos there was heavy soot deposits and displacement from impact however both right and left lateral servo sloppy links still exhibited nominal freedom of movement.
The fore/aft servo bellcrank had over-extended beyond the normal range of travel, the major item of interest was the hardware that connects the servo to the link assembly was backed out and cocked at a 45 degree angle. This bolt was jammed and had displaced the rod end bearing inner race which exposed the roller bearings. There was a bushing on the bolt head side and a large area washer against the bushing and two thin washers to prevent shank out, the threaded end of the bolt was jammed inside the inner race of the bearing. Search of the the area around the mrgb found what may be the nut-side bushing however the washers, nut, and cotter key were not found.
The entire servo was removed, documented, and then the bolt was removed whole with no evidence of shearing or significant deformation. Threads were visible and the cotter key hole was empty.
Inspection of the other primary servo attaching hardware showed no discrepancies, the left lateral lower clevis bolt was removed for reference of length to the fore/aft servo bolt with no significant difference noted.
The bolt removed from the fore/aft and the left lateral links both had part number NAS6205-32D. The right lateral link bolt was an NAS6205-31D. Ipc calls for NAS464P5 hardware, verified that the NAS6205 supersedes the series called out in the ipc.
Due to the missing hardware on the fore/aft primary servo attachment special emphasis was placed on reviewing the logbooks to determine what heavy maintenance was done that may coincide with the servo attaching hardware being disturbed. Below is the following maintenance that was documented:
12/17/2021 @ Actt 36,741.2 - m/r blades, hub, mrgb removed for maintenance convenience.
12/28/2021 @ Actt 36,741.2 - heavy maintenance was performed by privacy data omitted on wo# 12204. Discrepancy #11 of that work order states: "removed and installed fwd & aft servo s/n #R308 ref sa 4045-80 chap 65-46-0" signed by A&P privacy data omitted and inspected by inspectorprivacy data omitted. The aircraft was reassembled and a ground run and ground track and balance was performed.
12/30/2021 @ Actt 36,741.2 - privacy data omitted signed off the return to service and the hover and fwd flight t&b at the same actt.
02/16/2022 @ Actt 36,747.7 - post maintenance 5-17 hour torque check of installed components.
02/22/2022 The aircraft total time at the start of the day prior to the accident flight was 36,748.7.
The aircraft flew approx. 7.5 hours and the flight on the day of the accident since servo installation.
See sas ar# WP13202201667.
As the FAA filed it
02/22/2022:
AT APPROXIMATELY 10:20 HST AN S61N, REGISTRATION # N615CK, ^PRIVACY DATA OMITTED^ WAS DESTROYED ON GROUND IMPACT AT BARKING SANDS AIRPORT. THE HELICOPTER WAS PERFORMING A PART 133 OPERATION IN SUPPORT OF THE PACIFIC MISSILE RANGE FACILITY RETRIEVING PRACTICE TORPEDOES FROM THE WATERS WEST OF THE ISLAND OF KAUAI. WITNESS STATEMENTS SHARED A SIMILAR TREND THAT THE AIRCRAFT WAS OVER THE TAXIWAY AND EVERYTHING LOOKED NORMAL AND THEN SUDDENLY THE HELICOPTER PITCHED NOSE DOWN AND CRASHED.
02/23/2022:
FAA ON SCENE AND CONDUCTED ROUTINE INVESTIGATIVE INTERVIEWS AND VERIFIED INFORMATION PREVIOUSLY GATHERED BY MILITARY PERSONNEL, REVIEWED MAINTENANCE RECORDS, PICTURE DOCUMENTED THE ACCIDENT SITE. CRASH DISPERSAL INDICATED A LOW ANGLE HIGH VELOCITY IMPACT WITH POWER TO THE ROTOR SYSTEM DUE TO CONSISTENT GROUND SCARRING BY THE MAIN ROTOR BLADES. NTSB ARRIVED AT END OF DAY AND TOOK POSSESSION OF THE ACCIDENT INVESTIGATION.
02/24/2022:
COCKPIT VOICE RECORDER SENT TO NTSB LABS.
CONDUCTED FLIGHT CONTROL CONTINUITY CHECK, CONDUCTED POWERTRAIN CONTINUITY CHECK. ITEM OF INTEREST NOTED DURING FLIGHT CONTROL CONTINUITY CHECK, BELOW IS AN EXCERPT FROM MY SAS ACTIVITY RECORD:
FROM THE MAIN ROTOR FLIGHT CONTROL BELLCRANKS TO THE PRIMARY SERVOS THERE WAS HEAVY SOOT DEPOSITS AND DISPLACEMENT FROM IMPACT HOWEVER BOTH RIGHT AND LEFT LATERAL SERVO SLOPPY LINKS STILL EXHIBITED NOMINAL FREEDOM OF MOVEMENT.
THE FORE/AFT SERVO BELLCRANK HAD OVER-EXTENDED BEYOND THE NORMAL RANGE OF TRAVEL, THE MAJOR ITEM OF INTEREST WAS THE HARDWARE THAT CONNECTS THE SERVO TO THE LINK ASSEMBLY WAS BACKED OUT AND COCKED AT A 45 DEGREE ANGLE. THIS BOLT WAS JAMMED AND HAD DISPLACED THE ROD END BEARING INNER RACE WHICH EXPOSED THE ROLLER BEARINGS. THERE WAS A BUSHING ON THE BOLT HEAD SIDE AND A LARGE AREA WASHER AGAINST THE BUSHING AND TWO THIN WASHERS TO PREVENT SHANK OUT, THE THREADED END OF THE BOLT WAS JAMMED INSIDE THE INNER RACE OF THE BEARING. SEARCH OF THE THE AREA AROUND THE MRGB FOUND WHAT MAY BE THE NUT-SIDE BUSHING HOWEVER THE WASHERS, NUT, AND COTTER KEY WERE NOT FOUND.
THE ENTIRE SERVO WAS REMOVED, DOCUMENTED, AND THEN THE BOLT WAS REMOVED WHOLE WITH NO EVIDENCE OF SHEARING OR SIGNIFICANT DEFORMATION. THREADS WERE VISIBLE AND THE COTTER KEY HOLE WAS EMPTY.
INSPECTION OF THE OTHER PRIMARY SERVO ATTACHING HARDWARE SHOWED NO DISCREPANCIES, THE LEFT LATERAL LOWER CLEVIS BOLT WAS REMOVED FOR REFERENCE OF LENGTH TO THE FORE/AFT SERVO BOLT WITH NO SIGNIFICANT DIFFERENCE NOTED.
THE BOLT REMOVED FROM THE FORE/AFT AND THE LEFT LATERAL LINKS BOTH HAD PART NUMBER NAS6205-32D. THE RIGHT LATERAL LINK BOLT WAS AN NAS6205-31D. IPC CALLS FOR NAS464P5 HARDWARE, VERIFIED THAT THE NAS6205 SUPERSEDES THE SERIES CALLED OUT IN THE IPC.
DUE TO THE MISSING HARDWARE ON THE FORE/AFT PRIMARY SERVO ATTACHMENT SPECIAL EMPHASIS WAS PLACED ON REVIEWING THE LOGBOOKS TO DETERMINE WHAT HEAVY MAINTENANCE WAS DONE THAT MAY COINCIDE WITH THE SERVO ATTACHING HARDWARE BEING DISTURBED. BELOW IS THE FOLLOWING MAINTENANCE THAT WAS DOCUMENTED:
12/17/2021 @ ACTT 36,741.2 - M/R BLADES, HUB, MRGB REMOVED FOR MAINTENANCE CONVENIENCE.
12/28/2021 @ ACTT 36,741.2 - HEAVY MAINTENANCE WAS PERFORMED BY ^PRIVACY DATA OMITTED^ ON WO# 12204. DISCREPANCY #11 OF THAT WORK ORDER STATES: "REMOVED AND INSTALLED FWD & AFT SERVO S/N #R308 REF SA 4045-80 CHAP 65-46-0" SIGNED BY A&P ^PRIVACY DATA OMITTED^ AND INSPECTED BY INSPECTOR^PRIVACY DATA OMITTED^. THE AIRCRAFT WAS REASSEMBLED AND A GROUND RUN AND GROUND TRACK AND BALANCE WAS PERFORMED.
12/30/2021 @ ACTT 36,741.2 - ^PRIVACY DATA OMITTED^ SIGNED OFF THE RETURN TO SERVICE AND THE HOVER AND FWD FLIGHT T&B AT THE SAME ACTT.
02/16/2022 @ ACTT 36,747.7 - POST MAINTENANCE 5-17 HOUR TORQUE CHECK OF INSTALLED COMPONENTS.
02/22/2022 THE AIRCRAFT TOTAL TIME AT THE START OF THE DAY PRIOR TO THE ACCIDENT FLIGHT WAS 36,748.7.
THE AIRCRAFT FLEW APPROX. 7.5 HOURS AND THE FLIGHT ON THE DAY OF THE ACCIDENT SINCE SERVO INSTALLATION.
SEE SAS AR# WP13202201667.
NTSB investigation
The NTSB’s investigation of this event, with its probable cause and findings. Matched to this report by N-number and date.