Airworthiness directives › 2021-24-15
AD 2021-24-15 Airworthiness Directives; Bell Textron Canada Limited Helicopters
Models named: 206L-1, Model 206L-3, 206L-3, 206 L-4. Read the applicability below — it usually turns on serial or part numbers too.
Applicability*9
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.
Compliance
Comply with this AD within the compliance times specified, unless already done.
Required actions
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.
Unsafe condition
This AD was prompted by reports of deformation or fretting of the spline teeth on the air conditioning system drive ring and on the oil cooler blower shaft. The FAA is issuing this AD to detect deformation and fretting. The unsafe condition, if not addressed, could result in a failure of the oil cooler blower shaft, which could lead to loss of tail rotor authority and subsequent loss of helicopter control.
Affected ADs
None.
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