AD 2013-20-18
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| aircraft | Textron | Various | Airworthiness Directives; Bell Helicopter Textron, Inc. (Bell) Helicopters |
| aircraft | Bell | Helicopter Textron | Airworthiness Directives; Bell Helicopter Textron, Inc. (Bell) Helicopters |
Unsafe Condition
fatigue cracking of a yoke, failure of the yoke, and subsequent loss of control of the helicopter.
Required Actions
Within 10 hours time-in-service (TIS), review the helicopter records to determine all of the helicopter models on which an affected yoke has been installed since its production and the hours TIS of each affected yoke. If an affected part-numbered yoke has ever been installed on a Model 412CF helicopter or on a Model 412 or 412EP helicopter with a slope landing kit, P/N 412-704-012-101, installed, do the following: reidentify the P/N on the side of the yoke by using a vibrating stylus and etching two lines through the last three digits of the existing P/N and etching “137FM” adjacent to where you etched through the last three digits of the original P/N. This converts each affected yoke P/N to a new yoke P/N 412-010-101-137FM. The serial number remains the same. Treat the etched surface with chemical film, and apply primer and paint. Record the reidentified P/N on the applicable component history card or equivalent record. For each reidentified yoke, P/N 412-010-101-137FM, reduce the retirement life from 5,000 hours TIS to 4,500 hours TIS. Record the revised life limit on the applicable component history card or equivalent record. Revise the Airworthiness Limitations section of the applicable maintenance manual or the Instructions for Continued Airworthiness by reducing the retirement life from 5,000 hours TIS to 4,500 hours TIS for each reidentified yoke, P/N 412-010-101-137FM.
Compliance Time
Within 10 hours time-in-service (TIS)
Affected Aircraft
Model 412 and 412EP helicopters with a main rotor yoke assembly (yoke), part number (P/N) 412-010-101-123, -127, -129, or -133, installed; and Model 412CF helicopters with a yoke, P/N 412-010-101-127 or -129, installed; certificated in any category.
Source: Official FAA Source ↗
Retrieved: Apr 6, 2026
Rights: U.S. Government Public Domain
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