ROBINSON HELICOPTER R44 near Kekaha, HI — 2024-07-11

Probable cause

An encounter with turbulence due to downdraft winds that resulted in mast bumping and an in-flight breakup.

NTSB narrative

The helicopter was on a local air tour when the accident occurred. Witnesses reported strong, gusting wind and that a “huge” and sudden gust of wind blew over them, which was followed by a very loud “bang” noise. As their attention was drawn to the source of the loud noise, they saw the helicopter wreckage freefalling into the ocean in two sections: a main fuselage section and the tail boom section. Examination of the wreckage revealed no evidence of any preexisting anomalies that would have precluded normal operation of the helicopter. There was evidence that a mast bumping event had occurred and that the main rotor blades had contacted the airframe, which resulted in an in-flight breakup. There was no recorded information available that could be used to determine the helicopter's airspeed, altitude, or the pilot's control inputs. A weather study indicated that conditions were conducive to the development of strong downdraft winds. It is likely that the helicopter encountered turbulence due to downdrafts, which resulted in mast bumping and a subsequent in-flight breakup. Robinson Safety Notice SN-32 discusses flight in high winds and turbulence and explains how improper application of control inputs in response to turbulence can increase the likelihood of a mast bumping accident. It recommends that pilots reduce airspeed below normal cruise speed to 60 to 70 knots for flight in significant turbulence. It suggests techniques to avoid overcontrol of the helicopter and says to avoid flying on the downwind side of hills and ridges.

Analysis

Primary failure mode

Loss of control

First missed decision gate

Pilot could have chosen to avoid flying in high winds and turbulence.

NTSB coding

• Mast bumping · Enroute

Evidence available

• ADS-B / radar
• Photos
• 18 docket documents

Docket documents18

• CERTIFICATION OF PARTY REPRESENTATIVESform
• PILOT/OPERATOR AIRCRAFT ACCIDENT REPORT, NTSB FORM 6120.1form
• RELEASE OF AIRCRAFT WRECKAGE, NTSB FORM 6120.15form
• WITNESS STATEMENTSinterview
• METEOROLOGY ATTACHMENT 2 - PRINCEVIILE W WEATHER CAMERAother
• NO AUTOPSY - NO TOXICOLOGYother
• PILOT'S SAFETY COURSEother
• ROBINSON SAFETY NOTICE SN-32other
• INVESTIGATIVE PHOTOGRAPHSphotos
• METEOROLOGY ATTACHMENT 1 -FAA MAKAHA RIDGE N WEATHER CAMERA IMAGERYphotos
• METEOROLOGY ATTACHMENT 3 - GOES-18 INFRARED SATELLITE IMAGERYphotos
• METEOROLOGY ATTACHMENT 4 - GOES-18 GEOCOLOR SATELLITE IMAGERYphotos
• METEOROLOGY ATTACHMENT 5 - GOES-18 WATER VAPOR IMAGERYphotos
• ADS-Bradar
• METEOROLOGY ATTACHMENT 6 - NWS PHKI WSR-88D RADAR ANIMATIONradar
• METEOROLOGY FACTUAL REPORTreport
• PERSONAL ELECTRONIC DEVICE - SPECIALIST'S FACTUAL REPORTreport
• WRECKAGE EXAMINATIONwreckage

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