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ASN Wikibase Occurrence # 184620
Last updated: 22 March 2019
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Date:18-FEB-2016
Time:10:20
Type:Silhouette image of generic B06 model; specific model in this crash may look slightly different
Bell 206B3 JetRanger
Owner/operator:Genesis Helicopters
Registration: N80918
C/n / msn: 2687
Fatalities:Fatalities: 1 / Occupants: 5
Other fatalities:0
Aircraft damage: Substantial
Category:Accident
Location:near Ford Island, Pearl Harbor, Honolulu, HI -   United States of America
Phase: En route
Nature:Survey
Departure airport:Honolulu, HI (HLN)
Destination airport:Honolulu, HI (HLN)
Investigating agency: NTSB
Narrative:
The commercial pilot of the helicopter was performing a local air tour around the island with four passengers onboard. During the flight, he noticed a vibration throughout the cabin. The pilot diverted toward the destination airport; however, when the vibration stopped shortly thereafter, he decided to initiate a turn so the passengers could see a nearby landmark. The vibration returned shortly thereafter, and the pilot began to maneuver toward the destination airport a second time. The pilot stated that the vibration developed into a grinding sensation, which was followed by illumination of the main rotor low rpm warning light and an increase in engine rpm to the point where the engine and rotor RPM needles were no longer matched on the power turbine gauge. The pilot initiated an approach to a grassy area near the shoreline; however, due to the presence of people nearby, he turned the helicopter slightly left to land in the water as close to shore as possible. The pilot said that, about 20 ft above the water, it felt like the main rotor stalled, the helicopter lost lift, and it "fell out of the sky." The helicopter descended rapidly into the water and sank about 20 ft from the shoreline.

Three of the passengers were able to egress the helicopter following impact; however, the middle aft seat passenger was trapped inside. A first responder stated that he and another person repeatedly dove underwater to cut the passenger's seatbelt straps and extract him. The first responder reported that the passenger's life preserver appeared to be entangled with the seatbelts. Postaccident examination of the life preserver revealed signatures of inflation and cut waist straps, with no other damage noted. It could not be determined when or how the life preserver was inflated; the first responder could not recall whether it was inflated and the nurse providing CPR said it was not inflated. Review of treatment records for the passenger revealed evidence consistent with drowning, and no traumatic injuries to the head or neck. It could not be determined whether the passenger was unable to extricate himself from the restraint, or if he had a period of unconsciousness resulting from the impact that contributed to his drowning. The helicopter's doors were not installed at the time of the accident and all five seat restraints were found to be in working order and undamaged.

Postaccident examination of the helicopter revealed that the engine-to-transmission drive shaft was separated at the transmission side. Metallurgical examination of the engine-to-transmission drive shaft components revealed that the forward coupling did not appear to be lubricated and that there were multiple indications of exposure to elevated temperature, such as heat tinting and loss of the temperature plates on the forward outer coupling, high-temperature cadmium-induced brittle fracture of two forward attachment bolt heads, and a loss of hardness of the bolt head material due to high-temperature tempering. The external spline teeth on the forward spherical coupling were worn down to the bottom landings, while comparatively minor wear marks were observed on the mating internal spline teeth of the forward outer coupling. The asymmetry in the wear pattern between the spherical coupling and the outer coupling combined with the observations consistent with elevated temperatures indicate that the assembly likely failed by overheating due to lack of lubrication. This resulted in softening and subsequent failure of the spring that limits and centers the spherical coupling. When the spring failed, the coupling shifted forward, damaging the forward end of the outer coupling, fracturing the forward cover plate, and wearing the external spline teeth down to the bottom landings. Following the failure of the drive shaft, the engine would have continued to operate, but would not have been able to drive the main rotor.



Interviews with the pilot, the owner of the company, and a non-mechanic rated maintenance assistant indicated that maintenance had recently been conducte

Probable Cause: The in-flight failure of the engine-to-transmission drive shaft due to improper maintenance, which resulted in low main rotor rpm and a subsequent hard landing to water.

Sources:

NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20160218X71040&key=1
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?nNumberTxt=80918

Accident investigation:
cover
  
Investigating agency: NTSB
Status: Investigation completed
Duration: 2 years
Download report: Final report


Revision history:

Date/timeContributorUpdates
18-Feb-2016 22:27 Aerossurance Added
18-Feb-2016 22:27 Aerossurance Updated [Operator, Source]
18-Feb-2016 22:35 Aerossurance Updated [Embed code]
18-Feb-2016 22:45 Aerossurance Updated [Aircraft type, Embed code, Narrative]
19-Feb-2016 00:22 Geno Updated [Aircraft type, Registration, Cn, Location, Phase, Departure airport, Source, Damage, Narrative]
19-Feb-2016 08:10 harro Updated [Narrative]
19-Feb-2016 08:15 Aerossurance Updated [Time, Phase, Embed code, Narrative]
19-Feb-2016 08:16 Aerossurance Updated [Narrative]
19-Feb-2016 16:29 Geno Updated [Source, Narrative]
20-Feb-2016 11:38 Aerossurance Updated [Narrative]
23-Feb-2016 10:07 gerard57 Updated [Total fatalities, Source, Narrative]
23-Feb-2016 17:26 Aerossurance Updated [Source, Narrative]
24-Feb-2016 15:26 Aerossurance Updated [Source]
24-Feb-2016 15:27 Aerossurance Updated [Narrative]
21-Dec-2016 19:30 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
23-Feb-2018 09:51 Aerossurance Updated [Time, Aircraft type, Location, Nature, Destination airport, Source, Narrative]
01-Mar-2018 17:56 ASN Update Bot Updated [Time, Operator, Nature, Departure airport, Destination airport, Source, Embed code, Narrative]

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