AD 91-08-03

91-08-03 SIKORSKY AIRCRAFT: Amendment 39-6958. Docket No. 91-ASW-05.

Applicability: All Sikorsky Aircraft Model S-76A helicopters, certificated in any category.

Compliance: Required as indicated, unless already accomplished.

To prevent fatigue failure of the vertical pylon forward spar, which could result in loss of the helicopter, accomplish the following:

(a) Within the next 25 hours time in service determine if forward spar cap angles, part numbers (P/N's) 76201-05001-103 and 76201-05001-104, are installed and if it is equipped with Sikorsky Modification Kit 76070-20086, then--

(1) If the affected helicopter has Sikorsky Modification Kit 76070-20086 installed, no further action is necessary; however

(2) If the affected helicopter has the original unmodified forward spar cap angles with 1,395 or more hours time in service after the effective date of this AD, comply with paragraph (c), unless already accomplished, and thereafter at intervals notto exceed 1,420 hours time in service.

NOTE: Information pertaining to Kit 76070-20086 is contained in Sikorsky Alert Service Bulletin No. 76-55-12.

(b) For those helicopters with the original unmodified forward spar cap angles specified in paragraph (a)(2) with less than 1,395 hours time in service after the effective date of this AD, compliance with paragraph (c) is required prior to accumulation of 1,420 hours time in service, unless already accomplished, and thereafter at intervals not to exceed 1,420 hours time in service.

(c) Remove and replace the forward spar cap angles with new parts of the same part numbers.

(d) In accordance with FAR Sections 21.197 and 21.199, the helicopter may be flown to a base where compliance with the AD may be accomplished.

(e) Upon submission of substantiating data by an owner or operator through an FAA Airworthiness Inspector, an alternate method of compliance or adjustment of the compliance times, which provides an equivalent level of safety, may be used if approved by the Manager, Boston Aircraft Certification Office, Engine and Propeller Directorate, FAA, 12 New England Executive Park, Burlington, Massachusetts 01803.

This Amendment (39-6958, AD 91-08-03) becomes effective on May 3, 1991.