AD Issued for Bell 407 Expandable Blade Bolts on Main Rotor

The FAA has issued a new airworthiness directive for Bell Textron Canada Limited (BTCL) Model 407 and 427 helicopters. This AD was prompted by a report that certain expandable blade bolts installed on the main rotor blade may not have received the correct heat treatment, which could result in stress corrosion cracking of the expandable blade bolts. 

This AD requires replacement of affected bolts with bolts eligible for installation within 30 hours’ time-in-service or 30 days, whichever occurs first. 

Affected expandable blade bolts have part number (P/N) 406-310-103 and a serial number (S/N) SLFS9386 through SLFS9405 inclusive. Bolts eligible for installation are those with the same P/N but with a S/N not in the range of affected bolts. 

BTCL Alert Service Bulletin (ASB) 407-24-137, issued July 17, 2024 
Transport Canada AD CF-2025-21, effective May 6, 2025 
FAA AD 2025-13-01, effective July 8, 2025 (this AD)