AD NUMBER: 2018-10-06

PRODUCT: Bell Model 407 helicopters.

ACTION: Final Rule.

SUMMARY: This AD requires repetitive inspections of the tail rotor (TR) driveshaft segment assemblies and a torque check of the TR adapter retention nuts.

This AD was prompted by a report of an in-flight failure of the TR drive system.

The actions of this AD are intended to detect and correct an unsafe condition on these products.

DATES: This AD is effective June 25, 2018.

COST: The FAA estimates this AD affects 667 helicopters of U.S. Registry.  The costs of compliance are estimated to be:
Inspecting the TR driveshaft segments and adapters for play requires about 1 work-hour, for a cost per helicopter of $85
Determining the torque of the four adapter retention nuts requires about 3 work-hours for a cost per helicopter of $255
If required, repairing a worn driveshaft adapter would require about 3 work-hours, and required parts cost about $1,259, for a cost per helicopter of $1,514
Replacing an adapter retention nut requires about 1 work-hour, and required parts cost are negligible, for a cost of $85 per helicopter

FMI: AD