# NTSB LAX97FA107: Hughes 369D, N505RM, Milolii, HI, February 21, 1997 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Field investigation · Final report - Date: February 21, 1997, 09:09 local (19:09 UTC) - Place: Milolii, HI - Coordinates: 19.420429, -155.909317 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=19.4204&lon=-155.9093&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 3 serious, 1 minor - Status: Completed, report December 31, 1998 - Report: Approved by Office Director - NTSB case key (mKey): 29607 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX97FA107 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/29607/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=29607 - Page: https://openairdocs.org/ntsb/LAX97FA107 ## Probable cause failure of the tail rotor for undetermined reason(s), resulting in tail rotor imbalance, separation of the tail rotor, and an autorotative landing on rough terrain with high vegetation. The lack of suitable terrain for a forced landing was a related factor. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, cruise - rotor system,tail rotor - undetermined (cause) - rotor system,tail rotor - dynamic imbalance (cause) - rotor system,tail rotor - separation - Loss of control - in flight, cruise - tail rotor/anti-torque control - not possible - Forced landing, emergency descent/landing - autorotation - performed, pilot in command - In flight collision with terrain/water, emergency landing - terrain condition - none suitable (contributing factor) - terrain condition - rough/uneven (contributing factor) - terrain condition - high vegetation (contributing factor) ## Analysis The purpose of the flight was to transport state employees to a nearby work site. The pilot took off, climbed to about 400 feet msl, and accelerated to 90 knots. The first minute of flight was routine, and the pilot did not indicate he was experiencing any malfunctions. Suddenly, a loud bang was heard which was followed by a slight shudder in the tail rotor pedals. A passenger reported observing pieces of the tail rotor blades flying past the left side of the helicopter. The pilot applied pressure to the tail rotor pedals, but no response was evident. The pilot autorotated to a landing on rough terrain covered with vegetation. The helicopter was recovered and examined. No evidence of mechanical problems was found. The tail rotor blade assembly was not located. Prior to the flight, the helicopter's doors had been removed. Also, 2 days earlier, company maintenance personnel had replaced one of the two tail rotor pitch change links due to excessive wear in its rod end bearing. ## Factual narrative HISTORY OF FLIGHT On February 21, 1997, about 0909 hours Hawaiian standard time, a Hughes HU-369-D, N505RM, operated by Manuiwa Airways, Inc., d.b.a. Volcano Hili-Tours, experienced the loss of its tail rotor assembly during cruise flight. The flight was operating under 14 CFR Part 135. The helicopter was substantially damaged during the pilot's forced landing on rough terrain about 5 miles southeast of Milolii, Hawaii. The commercial pilot and two passengers were seriously injured. The fourth passenger received minor injuries. Visual meteorological conditions prevailed, and a company VFR flight plan was filed. The local flight originated from a remote area approximately 1.4 miles north of the crash site about 0850. The purpose of the flight was to transport personnel from the State of Hawaii's Department of Land and Natural Resources, Division of Forestry and Wildlife, to a work site within the Manuka Forest Reserve, in the South Kona District of the island of Hawaii. The personnel had been directed to spray fountain grass. The passengers and their equipment boarded the helicopter, and the flight commenced. The pilot did not report that anything unusual occurred until after he leveled off at 90 knots airspeed and 400 feet mean sea level. The pilot indicated that about 1 minute after taking off he heard a loud bang, and immediately thereafter he felt a slight shudder in the tail rotor pedals. When he applied pressure to the tail rotor pedals there was no response. Seconds later the helicopter entered a steep left nose tuck attitude. The pilot reported that he regained control, flew for several minutes, and then began an autorotation. The helicopter touched down hard in an area covered with vegetation and rolled over. The engine continued operating and the main rotor blades continued rotating after the ground impact. The left rear seated passenger reported that about 1 minute into the flight he heard a loud bang. Thereafter, he observed pieces of tail rotor blades flying past the left side of the helicopter. PERSONNEL INFORMATION The pilot passed an Federal Aviation Administration (FAA) proficiency flight check on November 25, 1996. The flight was performed in the accident helicopter, and was conducted by personnel from the FAA's Honolulu Flight Standards District Office. No training or airman proficiency deficiencies were reported. AIRCRAFT INFORMATION On February 19, 1997, the operator's director of maintenance examined the helicopter and observed that one of the two tail rotor assembly pitch change links exhibited excessive wear in the rod end bearing. The maintenance director removed the link. He replaced it with a serviceable link from his inventory. The replacement link had previously accrued about 100 hours of in-service use. The maintenance director further reported that he test flew the helicopter and determined it operated normally. The helicopter was placed back in service the following day. Prior to the accident flight all of the helicopter's doors had been removed. WRECKAGE AND IMPACT INFORMATION The crash site is located in the Kapua-Manuka Forest Reserve, southwest of the Mamalahoa Highway at the following GPS coordinates: 19 degrees 6.80 minutes north latitude, by 155 degrees 51.11 minutes west longitude. The flight originated at 19 degrees 7.80 minutes north latitude, by 155 degrees 50.31 minutes west longitude. Component part separation occurred within an estimated 7,300 feet northeast of the crash site. Multiple searches for the missing two tail rotor blades, pitch change links, and the gearbox output quill shaft were unproductive. The main wreckage was examined following its recovery from the accident site. The integrity of the power train, main rotor blades, and the flight control system was established. No pertinent maintenance anomalies were noted, except that a tail rotor assembly pitch change link had a recent replacement history. There was no evidence of fire. TESTS AND RESEARCH The tail rotor pitch link, which the operator had removed from the helicopter 2 days before the accident and had retained in its inventory, was examined under the supervision of the National Transportation Safety Board. The operator reported to the Safety Board that the link had been removed because its bearings appeared virtually worn out. The examination was performed on March 19, 1997, by C & H Hydraulics and Engineering, Acme-Divac Industries Division, in Newport Beach, California. The link was found to have worn out. No manufacturing defects were observed. An inventory was performed of the items reported to have been carried on board the helicopter during the accident flight. All reported items were accounted for. None of the occupants reported being aware of any item exiting the helicopter during the flight. The helicopter's tail rotor drive shaft and the tail rotor gear box housing were shipped to McDonnell Douglas Helicopter Systems (MDHS) in Mesa, Arizona, where they were examined under the supervision of the Safety Board. No evidence of preimpact defects was noted. MDHS laboratory personnel reported that the fracture surfaces exhibited evidence of tensile (instantaneous) overload. No evidence of fatigue was observed. MDHS opined that the most likely initiator for the housing fracture was a vibratory or out of balance load (of undetermined origin) created by the tail rotor assembly rotation and unbalanced centrifugal force. According to MDHS, events which potentially could produce the requisite force to fail the housing could result from: (a) tail rotor blade or related component failure, or (b) an event external to the helicopter such as foreign object impact damage to the rotating blade assembly. ADDITIONAL INFORMATION All recovered helicopter wreckage was released to the owner's assigned insurance adjuster on March 1, 1997. ## Aircraft - Registration: [N505RM](https://openairdocs.org/deregistered/N505RM-2004-11-05), registration cancelled 2004-11-05, S/N 1080358D (OpenAirDocs) - Reported make and model: Hughes 369D (HU-369-D) - Registry model: [Hughes Helicopters HUGHES 369D](https://openairdocs.org/model/hughes-helicopters-hughes-369d) (registry code 4470706) (OpenAirDocs) - Category: Helicopter - Serial number: 1080358D - Airframe hours: 7974 - Engines: Allison 250-C20B 375 horsepower turbo shaft - Damage: Substantial damage - Flight: Part 135 - Operator: Manuiwa Airways, doing business as Volcano Hili-Tours - Registered owner: Hili Logistics, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, January 20, 1997, 80 hours before - Departed: HI ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 51; commercial; instrument ratings: helicopter; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 8,575 total, 775 in this make and model, 8,395 as pilot in command, 70 in the last 90 days, 25 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 200° at 5 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 66 °F - Altimeter: 30.00 inHg ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19970221045249A](https://openairdocs.org/incident/19970221045249A), Feb 21, 1997: Scwzer 269D, Milolii, HI, Substantial damage. (.19) On February 21, 1997, about 0909 hours hawaiian standard time, a Hughes HU-369-D, N505RM, operated by manuiwa airways, inc., d.b.a. volcano hili-tours,… ## Docket (21 files) The files NTSB released with the investigation on July 16, 1998, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=29607. 5.9 MB in all. - Supplement A - Wreckage Documentation, Single (item 1, .PDF, 267 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087141&FileExtension=.PDF&FileName=Supplement%20A%20-%20Wreckage%20Documentation,%20Single-Master.PDF - Supplement C - Wreckage Documentation, Multi (item 2, .PDF, 393 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087161&FileExtension=.PDF&FileName=Supplement%20C%20-%20Wreckage%20Documentation,%20Multi-Master.PDF - Supplement S - Aircraft Occupant and Injured Ground Personnel (item 3, .PDF, 60 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087142&FileExtension=.PDF&FileName=Supplement%20S%20-%20Aircraft%20Occupant%20and%20Injured%20Ground%20Personnel-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 4, .PDF, 609 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40474821&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Witness Statements (item 5, .PDF, 98 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40474822&FileExtension=.PDF&FileName=Witness%20Statements-Master.PDF - Map of Accident Area (item 6, .PDF, 248 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087145&FileExtension=.PDF&FileName=Map%20of%20Accident%20Area-Master.PDF - Drawings of Tail Rotor Assembly (item 7, .PDF, 237 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087146&FileExtension=.PDF&FileName=Drawings%20of%20Tail%20Rotor%20Assembly-Master.PDF - Report from FAA Inspector Smith (item 8, .PDF, 53 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40474823&FileExtension=.PDF&FileName=Report%20from%20FAA%20Inspector%20Smith-Master.PDF - Report from FAA Inspector Reed and Operator Okita (item 9, .PDF, 545 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40474830&FileExtension=.PDF&FileName=Report%20from%20FAA%20Inspector%20Reed%20and%20Operator%20Okita-Master.PDF - Report from FAA Inspector Kanae (item 10, .PDF, 70 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40474825&FileExtension=.PDF&FileName=Report%20from%20FAA%20Inspector%20Kanae-Master.PDF - Reports from McDonnell Douglas Helicopter (item 11, .PDF, 2.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40474826&FileExtension=.PDF&FileName=Reports%20from%20McDonnell%20Douglas%20Helicopter-Master.PDF - FAA Form 8410-3, Airman Competency/Proficiency Check (item 12, .PDF, 123 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40474827&FileExtension=.PDF&FileName=FAA%20Form%208410-3,%20Airman%20Competency%2FProficiency%20Check-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 13, .PDF, 574 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40474828&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Master.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 14, .PDF, 77 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40474829&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Master.PDF - Photo 1. Aerial view of helicopter. (Photo provided by FAA) (item 15, .PDF, 78 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087154&FileExtension=.PDF&FileName=Photo%201.%20%20Aerial%20view%20of%20helicopter.%20%20(Photo%20provided%20by%20FAA)-Master.PDF - Photo 2. Right side of helicopter and skid assembly. (item 16, .PDF, 56 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087155&FileExtension=.PDF&FileName=Photo%202.%20%20Right%20side%20of%20helicopter%20and%20skid%20assembly.-Master.PDF - Photo 3. Left side of helicopter. (item 17, .PDF, 51 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087156&FileExtension=.PDF&FileName=Photo%203.%20%20Left%20side%20of%20helicopter.-Master.PDF - Photo 4. Skids (item 18, .PDF, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087157&FileExtension=.PDF&FileName=Photo%204.%20%20Skids-Master.PDF - Photo 5. Main rotor blades and tail rotor drive shaft. (item 19, .PDF, 56 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087158&FileExtension=.PDF&FileName=Photo%205.%20%20Main%20rotor%20blades%20and%20tail%20rotor%20drive%20shaft.-Master.PDF - Photo 6. Tail rotor drive shaft. (item 20, .PDF, 39 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087159&FileExtension=.PDF&FileName=Photo%206.%20%20Tail%20rotor%20drive%20shaft.-Master.PDF - Photo 7. Closeup view of the fractured gearbox. (item 21, .PDF, 48 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40087160&FileExtension=.PDF&FileName=Photo%207.%20%20Closeup%20view%20of%20the%20fractured%20gearbox.-Master.PDF From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.