Bell 407 Tail Boom Separation Prompts FAASTeam Caution

 - November 19, 2022, 10:07 AM
Bell 407 operators are advised to torque check tail boom attachment hardware following a June 8 in-flight separation accident. (Photo: National Transportation Safety Board)

A June in-flight tail boom separation on a Bell 407 has prompted the FAA's FAASTeam to issue a special notice reminding all operators of the standing FAA Airworthiness Directive (AD) 2012-18-09 to torque-check the boom’s attachment hardware every 300 hours. The NTSB’s investigation into the Hawaii air tour accident that seriously injured three of the six aboard is ongoing.

On June 8, the helicopter—registration N402SH and operated by K&S Helicopters doing business as Paradise Helicopters—crashed into a lava rock field near Kalea. The tail boom was recovered about 762 feet to the northeast of the main wreckage site. 

The 407’s tail boom is attached to the intermediate fuselage with bolts, washers, and nuts that connect the four aft fuselage longerons to four corresponding longerons located at the tail boom’s forward end. Post-accident the operator elected to replace the tail boom attachment hardware on its remaining five Bell 407s. Before hardware removal, the operator torque-checked the attachment hardware and found no evidence of loose hardware, but eddy-current nondestructive inspection on the aft fuselage longerons uncovered cracks on two of these five 407s.

Several bulletins and ADs have been issued since 2007 related to Bell 407 tail booms with regard to the aft fuselage top skin and bulkhead, replacement attachment hardware and torque checks, installation of external strap doublers on the upper-left longeron, and repair instructions for cracked longerons.