A preliminary report into a Hawaii tour helicopter crash revealed the chopper experienced a "violent upset," before spinning uncontrollably downward and crashing into a remote lava field.
The June 8 crash near Kalea, Hawaii, on the island of Hawaii, happened during a federally regulated "on-demand air tour flight" and left the pilot and two passengers seriously injured, while three other passengers sustained minor injuries, according to the National Transportation Safety Board.
NTSB’s aviation accident preliminary report details how a representative of the operator, Paradise Helicopters, told investigators that the chopper – a Bell 407 helicopter, N402SH – departed at approximately 5:01 p.m. local time from the company base at Ellison Onizuka Kona International Airport at Keahole (PHKO), Kona, Hawaii, and headed to the south for an air tour flight around the island.
The helicopter traveled southeast at about 500-600 ft above ground level and between airspeeds of 122 and 127 knots, according to automatic dependent surveillance-broadcast and company flight track data.
The pilot reported that the first part of the flight was normal.
About 30 minutes into the flight, the helicopter "experienced a violent upset, followed by an uncontrolled spin (yaw) to the right," according to the NTSB.
A passenger, seated in the aft left forward-facing seat reported that as the helicopter continued to spin, she observed something fall off the helicopter; however, she was not able to identify a specific part.
The flight track data showed a rapid descent and decrease in airspeed at the end of the flight track, consistent with the occupants’ statements, according to the NTSB.
The helicopter continued to spin uncontrollably while it descended, and it subsequently struck an area of rough, uneven, lava-covered terrain and came to rest on its left side.
After the impact, a passenger managed to make the emergency call to report the crash.
The helicopter broke into large pieces separated by hundreds of feet upon hitting the ground.
"An NTSB on site examination of the accident site revealed the tail boom came to rest about 762 ft northeast from the main wreckage, which consisted of the fuselage, engine, and main rotor system," the report says. "The tail boom separated from the fuselage at the tail boom attach point."
"The upper left attachment fitting fastener was not present, and the lower left attachment fitting was fractured and displayed fatigue signatures," the report continues. "The fasteners for the lower left, lower right, and upper right attachment fittings were present."
The helicopter’s maintenance records revealed that the most recent tail boom attachment fasteners torque check was completed on May 4, 2022, at a total airframe time of 22,891.4 flight hours.
At the time of the accident, the helicopter had accumulated 23,005.6 flight hours -- 114.2 flight hours since the torque check -- and no additional maintenance had been conducted to that attachment location.
The tail boom was installed on August 23, 2009, at a total airframe time of 5,780.0 hours and had not been removed prior to the accident, the NTSB says.
Portions of the tail boom structure, aft fuselage structure, attachment fittings and fasteners were retained for further examination by the NTSB’s Materials Laboratory.
An investigator from the National Transportation Safety Board's (NTSB) Alaska Regional Office, along with an NTSB airworthiness investigator, an NTSB survival factors investigator, and an NTSB maintenance investigator from Washington, D.C., responded to the island of Hawaii.