Loss of control Accident Hughes 369D N369TH,
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ASN Wikibase Occurrence # 205207
 
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Date:Saturday 27 January 2018
Time:15:34
Type:Silhouette image of generic H500 model; specific model in this crash may look slightly different    
Hughes 369D
Owner/operator:Hells Canyon Helicopters
Registration: N369TH
MSN: 1000830D
Year of manufacture:1980
Total airframe hrs:11793 hours
Engine model:Rolls-Royce 250-C20B
Fatalities:Fatalities: 1 / Occupants: 3
Aircraft damage: Substantial
Category:Accident
Location:Garfield County, 30 mi W of Clarkston, WA -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Agricultural
Departure airport:Gould City, WA
Destination airport:Gould City, WA
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The purpose of the wildlife capture flight was to catch and collar mule deer for tracking. The flight was operated with three crewmembers: a pilot, a gunner, and a mugger. The pilot sits in the front left seat, the gunner sits in the rear left seat and shoots nets from a net gun in order to capture deer, and the mugger sits in the front right seat and exits the helicopter to handle the tagging and release of the deer.

During a refueling stop after about 2 hours of flight, the pilot mentioned to the biologist that it was quite windy. The helicopter then departed; data from an onboard GPS unit showed the helicopter flying northeast through the ravine before reversing course and proceeding southwest through the ravine when the flight track ended in the vicinity of the accident site.

Examination of the site revealed two nets slightly northeast of the main wreckage. One net was mostly closed at the bottom of the ravine, with one weight extended farther than the others. This weight exhibited damage inconsistent with the other weights and was missing its rubber ring. Metallurgical examination of the weight revealed aluminum transfer marks. Another net that was partially open was located about 6 ft north of the first net and slightly up the western ravine wall. A piece of tail rotor skin was found about 5 ft farther north.

At the time of the accident, nearby airports were reporting wind gusts between 23 and 35 knots. A High Resolution Rapid Refresh model over the accident site identified strong low-level winds, with a maximum wind 1,000 ft above the surface from 230° at 48 knots. AIRMET Tango for low-level wind shear and turbulence due to strong winds was current for the area of the accident site at the time of the accident.

Postaccident examination did not reveal any anomalies with the engine that would have precluded normal operation. The tail rotor hub and stop exhibited contact marks and dents consistent with excessive tail rotor blade flapping. The tail rotor blades remained attached at the hub. One blade appeared undamaged, and the outboard 2 inches of the second blade had a dent with gouge marks with evidence of metal transfer consistent with stainless steel, similar to that of the net weight; the remaining section of the blade was bent and curled. One side of the tail rotor skin was fracture-separated.

Based on the marks on the tail rotor blade and on the net weight, it is likely that the net weight struck the leading edge of the tail rotor, which resulted in a fracture of the tail rotor tip and subsequent imbalance of the tail rotor blades. This imbalance resulted in excessive tail rotor blade flapping and subsequent loss of control. Despite two net guns being present in the helicopter, the angle the net weight impacted the tail rotor is consistent with the net originating from the left side of the helicopter. In addition, since there are several accounts of windy conditions it is potential that the wind affected the nets ability to open and possibly the net trajectory.

Probable Cause: A loss of control following the gunner's failure to ensure that the net maintained clearance from the tail rotor.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: WPR18FA074
Status: Investigation completed
Duration: 1 year and 5 months
Download report: Final report

Sources:

NTSB
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=369TH
http://aerossurance.com/helicopters/wildlife-netting-accidents/

Location

Images:


Revision history:

Date/timeContributorUpdates
28-Jan-2018 11:01 gerard57 Added
28-Jan-2018 12:21 Aerossurance Updated [Time, Operator, Location, Nature, Narrative]
28-Jan-2018 19:30 Iceman 29 Updated [Source, Narrative]
29-Jan-2018 00:03 Geno Updated [Registration, Cn, Operator, Location, Phase, Nature, Source, Narrative]
29-Jan-2018 09:15 Iceman 29 Updated [Source, Embed code]
29-Jan-2018 09:22 Iceman 29 Updated [Photo, ]
29-Jan-2018 09:28 Iceman 29 Updated [Operator]
29-Jan-2018 09:30 Iceman 29 Updated [Operator]
11-Jul-2019 14:04 Aerossurance Updated [Operator, Nature, Departure airport, Destination airport, Source, Narrative]
11-Jul-2019 14:35 Aerossurance Updated [Embed code]
15-Jul-2019 18:07 ASN Update Bot Updated [Time, Operator, Nature, Source, Embed code, Damage, Narrative, Accident report, ]
27-Jan-2021 07:58 Aerossurance Updated [Source, Embed code, Narrative, Accident report]
07-Aug-2023 14:03 harro Updated [[Source, Embed code, Narrative, Accident report]]

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