AD 2012-18-09 Airworthiness Directives; Bell Helicopter Textron Canada Helicopters

This AD becomes effective October 22, 2012.

(1) The Manager, Safety Management Group, FAA, may approve AMOCs for this AD. Send your proposal to: Sharon Miles, 2601 Meacham Blvd., Fort Worth, Texas 76137; telephone: (817) 222-5122; fax: 817-222-5961; email: sharon.y.miles@faa.gov. (2) For operations conducted under a 14 CFR part 119 operating certificate or under 14 CFR part 91, subpart K, we suggest that you notify your principal inspector, or lacking a principal inspector, the manager of the local flight standards district office or certificate holding district office, before operating any aircraft complying with this AD through an AMOC.

The subject of this AD is addressed in the Transport Canada Civil Aviation (TCCA) AD CF-2010-33, dated September 30, 2010.

(1) For helicopters with 7000 hours or less time-in-service (TIS), at the next 600 hours scheduled inspection, or 90 days, whichever comes first; and for helicopters with more than 7000 hours TIS, within 150 hours TIS or 90 days, whichever comes first, replace the tailboom-attachment hardware (attachment hardware) as follows: (i) Remove the left upper bolt, washers, and nut. (ii) Install a new bolt, part number (P/N) NAS627-30; washer, P/N 140-007-29S25E6; washer(s), P/N NAS1149G0732P; and new nut, P/N 42FLW-720 in accordance with paragraphs 2.a) through paragraph 3.e) of the “Accomplishment Instructions: Replacement of tailboom attachment bolts and nuts” section and Figure 2 in the BHTC Alert Service Bulletin No. 407-10-93, Revision A, dated August 30, 2010 (ASB). (iii) Remove the opposite right upper bolt, washers, and nut, and accomplish the requirements in paragraph (e)(1)(ii) of this AD. (iv) Remove the left lower bolt, washers, and nut. (v) Install a new bolt, (P/N) NAS626-26; washer, P/N 140-007-25S22E6; washer(s), P/N NAS1149G0663P; and new nut, P/N 42FLW-624 in accordance with paragraphs 6.a) through 7.e) of the “Accomplishment Instructions: Replacement of tailboom attachment bolts and nuts” section and Figure 2 in the ASB. (vi) Remove the right lower bolt, washers, and nut, and accomplish the requirements in paragraph (e)(1)(v) of this AD. (2) After installation of the new attachment hardware, at intervals of not less than 1 hour TIS but not exceeding 5 hours TIS, determine the torque of each nut until the torque stabilizes at each attachment location, referring to Figure 2 of the ASB. Apply the minimum specified torque of the range, plus the minimum acceptable tare torque of 14 inch/lbs (1.58 Nm) for the upper nuts, and 9.5 inch/lbs (1.07 Nm) for the lower nuts. (3) At intervals not to exceed 300 hours TIS, determine the torque of each of the four attachment nuts, referring to Figure 2 of the ASB. Apply the minimum specified torque of the range plus the minimum acceptable tare torque of 14 inch/lbs (1.58 Nm) for the upper nuts, and 9.5 inch/lbs (1.07 Nm) for the lower nuts. If the proper torque has not been retained since the last torque determination, remove and inspect the tailboom assembly for damage, corrosion, improper assembly, and condition. If the tailboom assembly is airworthy, replace the attachment hardware in accordance with the requirements in paragraphs (e)(1)(i) through (e)(1)(vi) and determine that the torque has stabilized in accordance with paragraph (e)(2) of this AD. Replace any unairworthy tailboom assembly with an airworthy tailboom assembly.

This AD defines the unsafe condition as an incorrect torque value of the tailboom attachment bolt (bolt) specified in the BHTC Model 407 Maintenance Manual and applied during manufacturing, which exceeds the torque range recommended for the bolts. This condition could result in an over-torque of the bolt, bolt failure, loss of the tailboom, and subsequent loss of control of the helicopter.