AD 2001-25-06 Airworthiness Directives; Sikorsky Aircraft Corporation Model S-76B and S-76C Helicopters

Models named: S-76B, S-76C. Read the applicability below — it usually turns on serial or part numbers too.

Model S-76B helicopters, serial numbers (S/N) 760430, 760441 through 760445, 760448 through 760452, 760454, 760455, 760458, 760462, and 760465, and Model S-76C helicopters, S/N 760420, 760436, 760438, 760440, 760453, 760456, 760457, 760459, 760460, 760461 760463, 760464, 760466 through 760487, certificated in any category. Note 1: This AD applies to each helicopter identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For helicopters that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (b) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Required within 30 days after the effective date of this AD, unless accomplished previously. To prevent an attitude and heading reference (AHRS) fail signal to both autopilots due to a failure of the essential bus, loss of both autopilot functions, and subsequent loss of control of the helicopter, accomplish the following: (a) Modify Nos. 1 and 2 AHRS WARN circuits in accordance with the Accomplishment Instructions, paragraphs 3.A. through 3.D, of Sikorsky Aircraft Corporation Alert Service Bulletin No. 76-34-7A (320A), Revision A, dated September 17, 2001. (b) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Boston Aircraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Boston Aircraft Certification Office. Note 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Boston Aircraft Certification Office. (c) Special flight permits may be issued in accordance with 14 CFR 21.197 and 21.199 to operate the helicopter to a location where the requirements of this AD can be accomplished. (d) The modification shall be done in accordance with the Accomplishment Instructions, paragraphs 3.A. through 3.D., of Sikorsky Aircraft Corporation Alert Service Bulletin No. 76-34-7A (320A), Revision A, dated September 17, 2001. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Sikorsky Aircraft Corporation, Attn: Manager, Commercial Tech Support, 6900 Main Street, Stratford, Connecticut 06614, phone (203) 386-3001, fax (203) 386-5983. 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 Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. (e) This amendment becomes effective on January 4, 2002. Issued in Fort Worth, Texas, on November 29, 2001. David A. Downey, Manager, Rotorcraft Directorate, Aircraft Certification Service. [FR Doc. 01-31039 Filed 12-19-01; 8:45 am] BILLING CODE 4910-13-U