Airworthiness Directive · Amendment 39-15833 · Bell Helicopter Textron Inc. Model 412, 412CF, and 412EP Helicopters
Bell Helicopter Textron Inc. Model 412, 412CF, and 412EP Helicopters
Superseded. A later AD replaced this one: AD 2013-20-18. Comply with the one in force.
The following model helicopters with the listed part-numbered main rotor yoke assembly (yoke), installed, certificated in any category.
| Model | With yoke part number (P/N) installed |
|---|---|
| 412 and 412EP | 412-010-101-123, -127, -129, or -133 |
| 412CF | 412-010-101-127, -129 |
This amendment adopts a new airworthiness directive (AD) for the specified Bell Helicopter Textron Inc. (Bell) model helicopters. This action requires reidentifying a certain part-numbered main rotor yoke (yoke) based on whether it was ever installed on a Model 412CF helicopter or on a Model 412 or 412EP helicopter with a slope landing kit. This AD also requires reducing the retirement life of the reidentified yokes from 5,000 hours time-in-service (TIS) to 4,500 hours TIS. Also, this AD requires recording the reidentified yoke part number (P/N) and the reduced retirement life on the component history card or equivalent record. This amendment is prompted by fatigue analysis that shows that the retirement life should be reduced on certain yokes. The actions specified in this AD are intended to prevent fatigue cracking of a yoke, failure of a yoke, and subsequent loss of control of the helicopter.
To prevent fatigue cracking of a yoke, failure of the yoke, and subsequent loss of control of the helicopter, do the following:
(a) Review the helicopter records to determine all of the helicopter models on which the affected yoke has been installed since its production and the hours TIS of each affected yoke.
(b) If an affected part-numbered yoke is installed or has ever been installed on a Model 412CF helicopter or on a Model 412 or 412EP helicopter with a (BHT-412-SI-62) slope landing kit, P/N 412-704-012-101, installed, do the following:
(1) Reidentify the P/N on the existing yoke data plate 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.
Note 1: The “FM” P/N suffix denotes a field modified part.
(2) Record the reidentified P/N on the applicable component history card or equivalent record.
(c) If you cannot determine all the model helicopters on which an affected yoke has been installed since its production or whether it has ever been installed on a Model 412 or 412EP helicopter with a (BHT-412-SI-62) slope landing kit, P/N 412-704-012-101, installed, reidentify the yoke P/N as P/N 412-010-101-137FM using a vibrating stylus in accordance with paragraph (b)(1) of this AD. Record the reidentified P/N on the applicable component history card or equivalent record.
(d) 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.
Note 2: Bell Helicopter Textron, Inc. Alert Service Bulletins No. 412-08-128 and No. 412CF-08-35, both dated March 4, 2008, pertain to the subject of this AD.
(e) This AD revises the Airworthiness Limitations section of the applicable maintenance manual or the Instructions for Continued Airworthiness (ICAs) 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.
(f) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Contact the Manager, Rotorcraft Directorate, FAA, ATTN: Michael Kohner, Aviation Safety Engineer, Rotorcraft Certification Office, Fort Worth, Texas 76193-0170, telephone (817) 222-5170, fax (817) 222-5783, for information about previously approved alternative methods of compliance.
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.
