NTSB: Helicopter crash that injured 6 caused by tail boom breaking off aircraft

A tour helicopter crash in Ka‘u that injured six people was caused by the tail boom of the aircraft separating from the fuselage at the point of attachment, according to a preliminary report released Wednesday by the National Transportation Safety Board.

The June 8 crash of the Bell 407 helicopter operated by Paradise Helicopters injured the pilot and two passengers seriously, while three other passengers sustained minor injuries.

The crash occurred at about 5:26 p.m., about 25 minutes after the chopper departed Ellison Onizuka Kona International Airport at Keahole for an around-the-island tour.

The aircraft, which was manufactured in 1997, came down hard in a lava field between Hawaiian Ranchos subdivision and South Point Road.

An NTSB on-site examination of the accident site revealed the tail boom came to rest about 762 feet northeast of the main wreckage, which consisted of the fuselage, engine, and main rotor system. The tail boom separated from the fuselage at the tail boom attach point.

One of the boom fasteners wasn’t found, while another was fractured and displayed signs of fatigue, the report concludes. Three other fasteners were in their proper places.

Automatic dependent surveillance-broadcast and company flight track data showed the helicopter traveled southeast about 500 feet to 600 feet above ground level at air speeds between 122 and 127 nautical miles per hour.

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 to the right.

A passenger, seated in the aft left forward-facing seat, reported that as the helicopter continued to spin, she saw 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 air speed at the end of the flight track, consistent with the occupants’ statements. The helicopter continued to spin uncontrollably as 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, an emergency call was placed by a passenger to report that the helicopter had crashed.

According to the Hawaii Fire Department, the location of the crash made it impossible for medics to reach the site on foot. They were flown in using both Hawaii County helicopters.

A review of the accident helicopter’s maintenance records revealed that the most recent tail boom attachment fasteners torque check was completed on May 4 at a total air-frame 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 Aug. 23, 2009, at a total air-frame time of 5,780 hours, and had not been removed prior to the accident.

Portions of the tail boom structure, aft fuselage structure, attachment fittings and fasteners were retained for further examination by the NTSB’s Materials Laboratory.

Calvin Dorn, chairman of Paradise Helicopters and CEO of its parent company, K&S Helicopters Inc., issued the following statement: “K&S Helicopters is working closely with the pilot, NTSB, FAA, and Bell, to support a thorough investigation of the June 8 accident on the Island of Hawaii. All Bell 407 aircraft operated by K&S Helicopters have been voluntarily grounded out of an abundance of caution until further safety determinations can be made.

“The company is in the process of reviewing the preliminary NTSB findings, and we will continue to work with investigators as they complete a final report.”