AD NUMBER: 2020-04-21

PRODUCT: Certain Bell Helicopter Textron Canada Limited (Bell Canada) Model 429 helicopters.

ACTION: Final rule; request for comments.

SUMMARY:  This AD requires inspecting a certain part-numbered curvic coupling for proper engagement and depending on the inspection results, inspecting for play, inspecting the curvic coupling teeth, inspecting the flapping bearing teeth, replacing parts, performing a rigging check, and reporting information.

This AD was prompted by a report of disengaged teeth of a curvic coupling due to improper installation.

DATES: This AD becomes effective March 31, 2020. The FAA must receive comments on this AD by May 15, 2020.

COST: The FAA estimates that this AD affects 88 helicopters of U.S. registry. Operators may incur the following costs in order to comply with this AD:

Labor costs are estimated at $85 per work-hour.

• Inspecting the curvic coupling teeth and the flapping bearing teeth for proper engagement requires about 0.5 work-hours for an estimated cost of $43 per helicopter.
• If required, removing and installing the T/R hub and blade assembly to inspect the curvic coupling teeth and the inboard and outboard flapping bearing teeth for a crack, wear, mechanical damage, and corrosion requires about 0.5 work-hours for an estimated cost of $43 per helicopter.
• Replacing a curvic coupling requires about 0.5 work-hours and parts cost about $4,141 for an estimated cost of $4,184 per curvic coupling.
• Replacing a flapping bearing requires about 0.5 work-hours and parts cost about $19,948 for an estimated cost of $19,991 per flapping bearing.
• If required, reporting information takes about 1 work-hour for an estimated cost of $85 per helicopter.

FMI: AD