AD 2011-15-51

To detect loose or misaligned parts of the servo that could lead to failure of the servo and subsequent loss of control of the helicopter, do the following:

(a) Before further flight, for those helicopters with a servo serial number (S/N) on the modification plate listed in Table 1 of Bell Alert Service Bulletin (ASB) No. 407-11-96, dated June 29, 2011, for the Model 407 helicopters or Table 1 of ASB 427-11-35, dated June 29, 2011, for the Model 427 helicopters, do the following:

(1) Retract the boot depicted as “230” in Figure 1 of this AD:

Note 1: Bell ASB 427-05-12, Revision A, dated November 14, 2005; HR Textron SBs 41011300-67-01, 41011400-67-01, and 41011700-67-01, all Revision 2, all dated November 9, 2005, which are not incorporated by reference, contain information pertaining to the subject of this AD.

(2) Applying only hand pressure, determine whether the nut, shaft, or clevis assembly, depicted as “225,” “215,” and “205,” respectively, in Figure 1 of this AD, turns independently. If the shaft turns independently of the nut or the clevis assembly, before further flight, replace the servo with an airworthy servo.

(3) If the shaft does not turn independently, inspect to determine whether at least one tab of the lock washer is bent flush against a flat surface of the nut and at least one tab of the lock washer is bent flush against a flat surface of the clevis assembly.

(i) If at least one lock washer tab is not aligned and bent flush with a nut flat surface and at least one lock washer tab is not aligned and bent flush with a flat surface of the clevis assembly, before further flight, replace the servo with an airworthy servo.

(ii) If any tab of the lock washer is not bent flush against either a flat surface of the nut or clevis assembly, bend the tab flush against a flat surface.

(4) After accomplishing paragraph (a)(1) through (a)(3) of this AD, reidentify the servo by metal-impression stamping or by vibro-etching “67-01” onto the modification plate.

(b) For those servo P/Ns with a S/N less than the S/Ns listed in the following Table A of this AD but NOT specifically included in the list of S/Ns in Table 1 referenced in paragraph (a) of this AD, within 25 hours time-in-service, inspect the nut, shaft, and clevis assembly and accomplish the requirements of paragraphs (a)(1) through (a)(4) of this AD.

(c) Before installing a servo with a P/N and S/N identified in paragraphs (a) or (b) of this AD, not identified by “67-01” on the modification plate, inspect the servo by following the requirements of this AD.

(d) 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, Safety Management Group, FAA, ATTN: Matt Wilbanks, Aviation Safety Engineer, 2601 Meacham Blvd, Fort Worth, Texas 76137, telephone (817) 222-5051, fax (817) 222-5961, for information about previously approved alternative methods of compliance.

(e) The Joint Aircraft System/Component (JASC) Code is: 6730: Rotorcraft Servo System.

(f) The affected servo serial numbers are listed in Table 1 of Bell Alert Service Bulletin (ASB) No. 407-11-96, dated June 29, 2011, for the Model 407 helicopters or Table 1 of ASB 427-11-35, dated June 29, 2011, for the Model 427 helicopters. The Director of the Federal Register approved this incorporation by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Bell Helicopter Textron Canada Limited, 12,800 Rue de l'Avenir, Mirabel, Quebec J7J1R4, telephone (450) 437-2862 or (800) 363-8023, fax (450) 433-0272, or at http://www.bellcustomer.com/files/. Copies may be inspected at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.