FAA Aviation Safety 

## EMERGENCY AIRWORTHINESS DIRECTIVE www.faa.gov/aircraft/safety/alerts/

DATE: December 20, 2010 AD #: 2011-01-52 Background This emergency AD is prompted by a locknut wo rking loose on the tailboo m aft cluster fitting strut. Further investigation revealed that the lock nut installed on the expanda ble bolt did not have the proper threads. This condition, if not corrected, could re sult in the strut and driveshaft separating from the helicopter and subsequent loss of control of the helicopter. FAA’s Determination We are issuing this AD because we evaluated a ll the relevant information and determined the unsafe condition described previously is likely to exist or develop in other helicopters of these same type designs. AD Requirements This AD requires, before further flight, unless accomplished prev iously, removing the locknut, part number MS21043-3. Reinstalling the loc knut while determining th e locknut drag torque is then required. If the drag torque is a minimum of 2 in-lbs, retorquing the locknut to 23 in-lbs is required. If the drag torque is not at least 2 in-lbs, replacing the loc knut with an airworthy locknut is required. Authority for this Rulemaking Title 49 of the United States Code specifies the FAA’s authority to issue rules on aviation safety. Subtitle I, Section 106, de scribes the authority of the FAA Administra tor. Subtitle VII, Aviation Programs, describes in more deta il the scope of the Agency’s authority. We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “Gener al requirements.” Under that section, Congress charges the FAA with promoting safe flight of ci vil aircraft in air commerce by pres cribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority becau se it addresses an unsafe condition that is likely to exist or develop on products iden tified in this rulemaking action. Pursuant to this Authority delegated to me by the Administrator, we are hereby issuing this Emergency Airworthiness Directive (AD). 2011-01-52 SCHWEIZER AI RCRAFT CORPORATION : Directorate Identifier 2010-SW-111- AD. Effective Date (a) This Emergency AD is effective upon receipt.

1Affected A Ds (b) None. Applicability (c) This AD applies to Model 269A, A-1, B, C, C- 1, and Th-55 series helicopters, that have an Aft Cluster Fitting Modification Kit, part number SA-269K-106, inst alled; Model 269C helicopters, serial numbers 1846 and larger; and Model 269C-1 helicopters, serial numbers 0156 and larger, certificated in any category. Unsafe Condition (d) This AD is prompted by a locknut working loose on the tailboom aft cluster fitting strut. Further investigation revealed th at the locknut installed on the expandable bolt did not have the proper threads. This condition, if not corrected, could re sult in the strut and driveshaft separating from the helicopter and subsequent loss of control of the helicopter. Compliance (e) Required before further flight, unless accomplished previously, remove the locknut, part number MS21043-3. Reinstall the loc knut while determining the locknu t drag torque. If the drag torque is a minimum of 2 in-lbs, re torque the locknut to 23 in-lbs. If the drag torque is not at least 2 in-lbs, replace the locknut with an airworthy locknut. Special Flight Permit (f) Special flight permits will not be issued. Alternative Methods of Compliance (AMOCs) (g) The Manager, New York Aircraft Certific ation 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 send ing information directly to the manager of the NYACO, send it to the attention of the Conti nued Operational Safety program manager. Note: Before using any approved AMOC, we request that you no tify your appropriate principal inspector, or lacking a principal inspector, your local F light Standards District Office. Other Information (h) For further information about this AD, c ontact: Stephen Kowalski, Aerospace Engineer, Airframe and Propulsion Branch, ANE-171, 1600 St ewart Ave., suite 410, Westbury, New York 11590, telephone (516) 228-7327, fax (516) 794-5531. Subject (i) The Joint Aircraft System Component (JASC) Code is 5302: Rotorcraft Tailboom.

2Issued in Fo rt Worth, Texas, on December 20, 2010.

M. Monica Merritt, Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

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