AD 2021-11-01 Prompted By The Engine Manufacturer Expanding The RPM (N2) Steady-State Operation Avoidance Range Limits

The FAA is superseding Airworthiness Directive (AD) 2013-20-13 for certain Bell Helicopter Textron Canada Limited (now Bell Textron Canada Limited) (Bell) Model 206B and 206L helicopters.

AD 2013-20-13 required installing a placard beneath the engine power dual tachometer and revising the Operating Limitations section of the existing Rotorcraft Flight Manual (RFM) for your helicopter. This AD was prompted by the engine manufacturer expanding the RPM (N2) steady-state operation avoidance range limits. This AD retains certain requirements of AD 2013-20-13, and requires revising certain sections of the existing RFM for your helicopter and installing or replacing a placard. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective July 15, 2021.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2013-20-13, Amendment 39-17619 (78 FR 66252, November 5, 2013), (AD 2013-20-13). AD 2013-20-13 applied to Bell Model 206B helicopters, serial number (S/N) 004 through 4675, including helicopters converted from Model 206A; and Bell Model 206L helicopters, S/N 45001 through 45153, and 46601 through 46617. The NPRM published in the Federal Register on March 11, 2021 (86 FR 13828). The NPRM proposed to require, within 25 hours time-in-service (TIS), revising the Operating Limitations and the Normal Procedures sections of the existing RFM for your helicopter and installing or replacing a placard. The NPRM was prompted by a determination from the manufacturers that the steady-state operation avoidance range limits needed to be expanded, amendments to the RFM needed to be incorporated, and a new placard (decal) needed to be installed.

Transport Canada AD CF-2018-23, dated August 22, 2018 (AD CF-2018-23), issued by Transport Canada, which is the aviation authority for Canada, corrects an unsafe condition for Bell Model 206B series helicopters including those converted from Model 206A, S/Ns up to 4690, and model 206L series helicopters, S/Ns 45001 through 45153 and 46601 through 46617. Transport Canada advises that Rolls Royce has expanded the RPM (N2) steady-state operation avoidance range limits due to several failures of the third stage turbine wheel. According to Transport Canada, Rolls Royce determined that detrimental vibrations could occur within a particular range of turbine speeds, which may be a contributing factor to these failures. Bell has also amended the RFMs and the engine starting procedures for RPM (N2) and provided a new decal (placard) to inform pilots to avoid steady-state operations at those engine turbine speeds. This condition, if not addressed, could result in turbine failure, engine power loss, and subsequent loss of control of the helicopter.

Accordingly, Transport Canada AD CF-2018-23 requires incorporating the amended RFM power plant operating limitations and engine starting procedures for RPM (N2) steady-state operation and installing a new decal.

FMI: www.regulations.gov