FAA Aviation Safety 

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

DATE: October 13, 2011 AD #: 2011-22-51 Emergency airworthiness direc tive (AD) 2011-22-51 is sent to owners and operators of Sikorsky Aircraft Corporation (Sikorsky) M odel S-70, S-70A, S-70C, S-70C(M), and S-70C(M1) helicopters. Background This emergency AD was prompted by an accident that resulted from the blockage of the internal oil passages of the inte rmediate gearbox (IGB). The blockage occurred when a plug was left in the IGB during coating of the IGB housing. The blockage caused insufficient lubrication of the IGB, which overheated, seized-up, a nd caused a fracture in the output sh aft that drives the tail rotor. This condition, if not corrected, coul d result in loss of tail rotor driv e and subsequent loss of control of the helicopter. Relevant Service Information We reviewed Sikorsky Alert Se rvice Bulletin No. 70-06-29A, dated October 11, 2011 (ASB). The ASB specifies:

 A one-time borescope inspection of the lubrication passages from the oil scupper to the input and output housing.

 Disassembling the IGB for inspection as an alternative to the borescope inspection.

 Adding an “A” suffix to the serial number of all IGBs that have been inspected. 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 products of the same type designs. AD Requirements This AD requires borescope inspecting the IGB fo r any obstruction in the oil passages. As an alternative to the boresc ope inspection, this AD allows disassembling the IGB and inspecting the oil passages for any obstruction. If there is any obstruc tion in any oil passage, replace the IGB with an airworthy IGB before further fli ght. These actions are required befo re further flight and must be accomplished in accordance with specified por tions of the ASB described previously. Differences Between This AD and the Service Information This AD does not apply to the Model H-60 helic opter as it does not have a U.S. type certificate. Also, this AD does not require returning any parts to Si korsky nor does it require marking the IGB after inspection. 1Authority 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. Presentation of the Actual AD We are issuing this AD under 49 U.S.C. Sectio n 44701 according to the authority delegated to me by the Administrator. 2011-22-51 SIKORSKY AIRCRAFT CORPORATION (Sikorsky) : Directorate Identifier 2011- SW-056-AD. (a) Effective Date This Emergency AD is effective upon receipt. (b) Affected ADs
None. (c) Applicability Sikorsky Model S-70, S-70A, S-70C, S-70C(M), and S-70C(M1) helicopters with an intermediate gearbox (IGB), part number 70357- 06300-044, with 100 or less hours time-in-service since new or overhaul. (d) Subject The Joint Aircraft System Component (JASC)/A ir Transport Associat ion (ATA) of America Code is 6520: Tail Rotor Gearbox. (e) Unsafe Condition This AD was prompted by an accident that result ed from the blockage of the internal oil passages of the IGB. The blockage occurred when a plug installed during coating of the IGB housing was left in the IGB oil passage. The blockage cau sed insufficient lubrication of the IGB, which overheated, seized-up, and caused a fr acture in the output shaft that drives the tail rotor. We are issuing this AD to prevent loss of tail rotor drive and subsequent loss of control of the helicopter. (f) Compliance Before further flight, unless accomplished previously.

2(g) Required Actions (1) Boresco pe inspect the IGB for any obstruction in the oil passages. Borescope inspect in accordance with the following por tions of Sikorsky Alert Servi ce Bulletin No. 70-06-29A, dated October 11, 2011 (ASB): (i) The Accomplishment Instructions, Secti on 3., paragraphs A.(1) through A.(3)(a); (ii) Equipment and Materials and Insp ection sections of Appendix 1; and Note 1: This AD does not require returning any parts to Sikorsky. (iii) Figures 1 through 10 of Appendix 1. (2) As an alternative to the requirements of pa ragraph (g)(1) of this AD, disassemble the IGB and inspect the oil passa ges for any obstruction. Note 2: Removing any obstruction fro m the IGB does not make it airworthy. (3) If there is any obstruction in any oil pass age, replace the IGB w ith an airworthy IGB before further flight. (h) Special Flight Permit Special flight permits are prohibited. (i) Alternative Methods of Compliance (AMOCs) (1) The Manager, Boston Aircraft Certifica tion Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested us ing 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 dire ctly to the manager of the ACO, send it to the attention of the person identified in the Related Information section of this AD. (2) Before using any approved AMOC, we sugge st that you notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local fli ght standards district office/certificate holding district office. (j) Related Information (1) For further information about this AD, c ontact: Mike Davison, Flight Test Engineer, Boston ACO, FAA, 12 New England Executive Park, phone: (781) 238-7156, fax: (781) 238-7170, e-mail: michael.davison@faa.gov. (2) For copies of the service information refe renced in this AD, contact Sikorsky Aircraft Corporation, Attn: Manager, Commercial Tec hnical Support, mailstop s581a, 6900 Main Street, Stratford, CT, telephone (203) 383-4866, e-mail address tsslibrary@sikorsky.com , or at http://www.sikorsky.com

.

3Issued in Fort Worth, Texas, on October 13, 2011.

Jorge R. Castillo, Acting Manager, Rotorcraft Directorate, Aircraf t Certification Service.

4