Airworthiness Directive · Amendment 39-21836 · Tail rotor drive shaft
Bell Textron Canada Limited Helicopters
This AD applies to the Bell Textron Canada Limited helicopters identified in paragraphs (c)(1) and (2) of this AD:
(1) Model 206L-1 and Model 206L-3 helicopters, certificated in any category, with Bell Model 206L1/L3 Service Instruction for Increased Gross Weight Upgrade Kit BHT-206-SI-2052, Revision 1, dated October 14, 2010, installed and that are equipped with one of the following Air Comm Corporation Supplemental Type Certificate (STC) SH2750NM air conditioning systems part number (P/N) 206EC-204-1, 206EC-204-2, 206EC-208-1, 206EC-208-2, 206EC-210-1, 206EC-210-2, 206EC-210-3, 206EC-212-3, or 206EC-212-4; and
Note 1 to paragraph (c)(1) of this AD: Helicopters with a 206L-1+ designation are Model 206L-1 helicopters and helicopters with a 206L-3+ designation are Model 206L-3 helicopters.
(2) Model 206 L-4 helicopters, certificated in any category, and that are equipped with one of the following Air Comm Corporation STC SH2750NM air conditioning systems P/N 206EC-204-1, 206EC-204-2, 206EC-208-1, 206EC-208-2, 206EC-210-1, 206EC-210-2, 206EC-210-3, 206EC-212-3, or 206EC-212-4.
The FAA is adopting a new airworthiness directive (AD) for Bell Textron Canada Limited Model 206L-1, 206L-3, and 206L-4 helicopters with certain Air Comm Corporation air conditioning systems installed. This AD was prompted by reports of damage to the drive ring spline teeth and the mating spline teeth. This AD requires visually inspecting the drive ring spline teeth and the mating area spline teeth on the oil cooler blower shaft for signs of deformation and fretting and depending on the results of the inspection, removing certain parts from service. This AD also requires reinstalling certain parts, applying torque, and aligning certain bolt holes. The FAA is issuing this AD to address the unsafe condition on these products.
Within 300 hours time-in-service (TIS) after the effective date of this AD, and thereafter at intervals not to exceed 300 hours TIS:
(1) Gain access to the drive ring spline teeth and the mating area spline teeth on the oil cooler blower shaft by removing the tail rotor drive system's forward short shaft and spline adaptor, and the air conditioner system's drive ring. Refer to Figure 1 of ACC Air Comm Corporation Service Bulletin SB 206EC-091119, Rev B, dated May 26, 2021 for a depiction of each component's location.
(2) Visually inspect the drive ring spline teeth and the mating area spline teeth on the oil cooler blower shaft for deformation and fretting.
(i) If there is deformation or fretting on the drive ring spline teeth, before further flight, remove the drive ring from service and replace it with an airworthy part.
(ii) If there is deformation or fretting on the mating area spline teeth of the oil cooler blower shaft, before further flight, remove the oil cooler blower assembly from service and replace with an airworthy part.
(3) Reinstall the drive ring, spline adapter, and the forward short shaft. If the compressor drive pulley was removed, torque the drive pulley to 200-300 in-lbs, increasing torque in this range to align the four threaded holes with the through holes in the drive ring. Do not back-off torque to align the bolt holes.
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.
