AD 2011-12-16 Airworthiness Directives; Schweizer Aircraft Corporation (Schweizer) Model 269A, A-1, B, C, C-1, and TH-55 Series Helicopters

Makes named: schweizer. Models named: 269A, A-1, B, C. Read the applicability below — it usually turns on serial or part numbers too.

Schweizer Model 269A, A-1, B, C helicopters (serial number (S/N) 1846 and larger); C-1 helicopters (S/N 0156 and larger); and TH-55 series helicopters with an Aft Cluster Fitting Modification Kit, part number (P/N) SA-269K-106, installed; certificated in any category.

Required as indicated, unless already done. (1) Before further flight, remove both the left-hand and right-hand locknuts, P/N MS21043-3. Reinstall the locknuts while determining the locknut drag torque. If the drag torque is a minimum of 2 in-lbs., retorque the locknut to 23 in-lbs. If the drag torque is not at least 2 in-lbs, replace the locknut with an airworthy locknut. (2) Within 10 hours time-in-service, modify each expandable bolt, P/N ADB221-1A, torque locknut, P/N MS21043-3, and install cotter pin, P/N MS24665-132 or MS24665-151, in accordance with the Procedure Section, Part II, of Schweizer Service Bulletin (SB) No. B-295, dated December 21, 2010, for Model 269A, A-1, B, C, and TH-55 series helicopters or SB No. C1B-032, dated December 21, 2010, for Model 269C-1 helicopters. (3) Before installing an expandable bolt, P/N ADB221-1A, to secure the tailboom support strut to the tailboom aft cluster fitting, modify the expandable bolt in accordance with paragraph (e)(2) of this AD. (f) Modifying both expandable bolts by torquing the locknuts and installing the cotter pins as required by this AD is terminating action for the requirements of paragraph (e)(1) and (e)(2) of this AD. Special Flight Permit (g) Special flight permits will not be issued. Alternative Methods of Compliance (AMOCs) (h) The Manager, New York Aircraft Certification Office (NYACO), FAA, has the authority to approve AMOCs for this AD if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the manager of the NYACO, send it to the attention of the Program Manager, Continuing Operational Safety. Note: Before using any approved AMOC, we request that you notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office or certificate holding district office. Related Information (i) For more information about this AD, contact Stephen Kowalski, Aviation Safety Engineer, FAA, Airframe and Propulsion Branch, ANE-171, 1600 Stewart Ave., Suite 410, Westbury, New York 11590, telephone (516) 228-7327, fax (516) 794-5531.

This AD was prompted by a locknut working loose on the tailboom aft cluster fitting strut because the locknut installed on one expandable bolt did not have the proper threads. This AD contains terminating action to require modifying each expandable bolt to allow installing a cotter pin to prevent the strut and driveshaft separating from the helicopter and subsequent loss of control of the helicopter.