Accident Robinson R44 Clipper N808NV,
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ASN Wikibase Occurrence # 224495
 
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Date:Monday 29 April 2019
Time:09:10 LT
Type:Silhouette image of generic R44 model; specific model in this crash may look slightly different    
Robinson R44 Clipper
Owner/operator:Novictor Aviation LLC
Registration: N808NV
MSN: 0926
Year of manufacture:2000
Total airframe hrs:6242 hours
Engine model:Lycoming O-540
Fatalities:Fatalities: 3 / Occupants: 3
Aircraft damage: Destroyed
Category:Accident
Location:Kawainui, Kailua, Oahu, HI -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Passenger - Non-Scheduled/charter/Air Taxi
Departure airport:Honolulu-Daniel K. Inouye International Airport, HI (HNL/PHNL)
Destination airport:Honolulu-Daniel K. Inouye International Airport, HI (HNL/PHNL)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The pilot and two passengers departed on a helicopter tour flight around the island. Air traffic control radar and communications information indicated that the flight encountered deteriorating visibility conditions enroute. About this time, the helicopter slowed from about 108 knots (kts) to about 92 kts and initiated a turn. Shortly thereafter, radar data then indicated a rapid descent from an altitude about 1,700 ft above ground level. Witnesses near the accident site reported hearing the helicopter in the clouds and reported that it sounded as if it was very low. They then described the sound of metal hitting metal and saw pieces of the helicopter falling from the sky.
Postaccident examination of the airframe revealed that the forward left roof and floor/chin exhibited damage consistent with contact from a main rotor blade. One main rotor blade exhibited a spanwise dent which displayed equally spaced score marks consistent with the row of screws in the windshield bow. The outboard portion of one of the main rotor blades, along with left fuselage and left side cabin components, were found early in the debris path. The main rotor drive shaft was bent about 20° above the swashplate. Arc-shaped scoring was observed on both sides of the main rotor hub adjacent to the pitch horns. Both teeter stops were crushed, and the driveshaft was dented. The droop stop bolt at the nut was sheard but remained in place. Examination of the engine revealed no anomalies and the evidence indicated that the engine was operating at the time of the accident.
The accident helicopter was equipped with a two-bladed, semirigid rotor system. This design is susceptible to excessive rotor blade flapping, during periods of low-G's or the pilot's improper application of control inputs. Excessive rotor blade flapping can result in main rotor contact with the fuselage. A manufacturer safety notice stated, in part, that, when flying in turbulence, the helicopter should be slowed below a normal cruise speed to around 60 to 70 kts.
Review of weather information for the area of the accident site around the time of the accident revealed a warm, moist environment that supported heavy rain showers that could produce unexpected strong downdrafts, reduced visibilities, wet microburst, and outflow wind conditions. At the time of the accident, weather surveillance radar reflectivity values indicated a descending core of 20 to 30 dBZ values descending towards the surface from above the accident site. The accident flight likely encountered this downdraft or outflow boundary, reduced visibilities, and rapidly changing and unexpected wind conditions. Which likely caused a low-G condition, excessive main rotor flapping, and an in-flight breakup when the main rotor contacted the cabin area.

Probable Cause: The helicopter's encounter with a strong downdraft or outflow boundary while operating at a higher than recommended airspeed in turbulence which resulted in a low-G condition, excessive main rotor flapping, and an in-flight breakup when the main rotor contacted the cabin area.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: WPR19FA123
Status: Investigation completed
Duration: 2 years
Download report: Final report

Sources:

NTSB WPR19FA123

https://flightaware.com/live/flight/N808NV/history/20190429/1855Z

https://flightaware.com/resources/registration/N808NV

FAA register: https://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=805NV

Location

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Revision history:

Date/timeContributorUpdates
29-Apr-2019 20:37 Captain Adam Added
29-Apr-2019 20:51 Iceman 29 Updated [Registration, Cn, Source, Embed code, Narrative]
29-Apr-2019 21:07 Geno Updated [Source, Embed code]
29-Apr-2019 21:33 Aerossurance Updated [Time, Location, Narrative]
29-Apr-2019 21:34 Aerossurance Updated [Embed code]
29-Apr-2019 21:36 Aerossurance Updated [Nature, Source, Embed code, Narrative]
29-Apr-2019 22:00 RobertMB Updated [Aircraft type, Registration, Narrative]
29-Apr-2019 22:07 Aerossurance Updated [Source, Embed code, Narrative]
30-Apr-2019 06:06 harro Updated [Time, Source, Photo]
30-Apr-2019 09:20 Iceman 29 Updated [Operator, Source, Embed code, Narrative]
30-Apr-2019 16:28 Aerossurance Updated [Operator, Embed code, Narrative]
30-Apr-2019 18:27 Geno Updated [Location, Departure airport, Destination airport, Source]
30-Apr-2019 21:50 Aerossurance Updated [Source]
08-Jul-2022 17:59 ASN Update Bot Updated [Operator, Other fatalities, Nature, Source, Embed code, Narrative, Category, Accident report]

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