Airworthiness Directive · Amendment 39-17633 · Main rotor drive system
Bell Helicopter Textron Canada (Bell) Helicopters
This AD applies to Model 206L-4 and 407 helicopters, with a freewheel aft bearing cap (cap), part number (P/N) 406-040-509-101, with a serial number with a prefix of “A-” and Nos. 1833 through 1912, installed, certificated in any category.
We are adopting a new airworthiness directive (AD) for Bell Model 206L-4 and 407 helicopters. This AD requires replacing or reworking certain aft bearing caps. This AD was prompted by the manufacture of certain freewheel aft bearing caps without a lubrication channel to allow oil flow into the aft bearing support assembly. The actions of this AD are intended to prevent failure of the freewheel unit and subsequent loss of control of the helicopter.
You are responsible for performing each action required by this AD within the specified compliance time unless it has already been accomplished prior to that time.
Within 50 hours time-in-service (TIS):
(1) Remove and disassemble each freewheel assembly.
(2) Replace the sprag and retainer (item 7), the output shaft (item 10), and the aft seal (item 3), as depicted in Figure 2 of Bell Alert Service Bulletin (ASB) No. 206L-04-129 for the Model 206L-4 and ASB No. 407-04-66 for the Model 407, both Revision A, and both dated December 1, 2004.
(3) Visually inspect the remaining freewheel part details for a missing channel.
(4) If the channel is missing, replace or rework the cap assembly by following the instructions depicted in Figure 3 of ASB 206L-04-129 or ASB 407 04-66, as applicable for your model helicopter. Using a vibrating stylus, mark the letter “R” at the end of the serial number on the cap assembly.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
