91-24-13 SIKORSKY AIRCRAFT: Amendment 39-8100. Docket No. 91-ASW-07.
Applicability: All Sikorsky Aircraft Model S-76A helicopters, certificated in any category, equipped with forward spar cap angles, part numbers (P/N's) 76201-05001-103 and 76201-05001-104, forward spar web, P/N 76201-05001-101, and forward spar web doubler, P/N 76201-05001-107, and not equipped with Modification Kit 76070-20086 installed in accordance with Sikorsky Alert Service Bulletin No. 76-55-12, dated June 6, 1986.
Compliance: Required as indicated, unless already accomplished.
To prevent failure of the helicopter vertical pylon forward spar cap, web, and web doubler, accomplish the following:
(a) For helicopters that have attained 100 or more hours' time in service, comply with paragraph (c) within the next 25 hours' time in service after the effective date of this AD unless already accomplished within the last 25 hours' time in service, and thereafter at intervals not to exceed 50 hours' time in service from the last inspection.
(b) For helicopters that have not attained 100 hours' time in service on the effective date of this AD, comply with paragraph (c) before attaining 125 hours' time in service, and thereafter at intervals not to exceed 50 hours' time in service.
(c) Inspect for cracks in the forward spar cap angles, spar web, and web doubler and in repairs and reinforcements in the area of the tail rotor shaft cutout in the pylon forward spar and areas adjacent to the fuselage shear deck as follows:
(1) Remove the tail rotor drive shaft fairings in the vicinity of the vertical pylon, exposing the shear deck and vertical pylon forward spar.
(2) Clean all accessible areas around the tail rotor drive shaft cutout area in the vertical pylon forward spar using a clean cloth dampened with solvent P-D-680, Type II, or FAA-approved equivalent.
(3) Using a light, visually inspect the forward side of the spar for cracks in all areas adjacentto the shear deck attachment to the forward spar web and the web doubler.
(4) Using a light and mirror, visually inspect the aft side of the spar for cracks. Inspect through the tail rotor drive shaft cutout.
(5) If cracks are found in the spar web or spar web doubler or in their repair or reinforcement parts, accomplish the following:
(i) For each part, if multiple cracks are found or if a single crack equal to or in excess of 2 1/2 inches in length is found, replace cracked parts prior to further flight with new parts of the same part number; or if not previously repaired or reinforced, incorporate a repair procedure contained in Sikorsky Overhaul and Repair Instructions (O&RI) 76200-014B, or later FAA-approved revisions, or an equivalent procedure approved as noted in paragraph (d) of this AD.
(ii) If a single crack is less than 2 1/2 inches in length, visually inspect the part for crack length prior to the first flight of each day, and--
(A) Within 25 hours' time in service after finding a crack, replace or repair the part in accordance with paragraph (c)(5)(i), except
(B) Replace or repair the affected part in accordance with paragraph (c)(5)(i) before further flight, whenever the crack length reaches 2 1/2 inches.
(6) If a crack is found in the spar cap angles, replace the cracked spar cap angles prior to further flight with a new spar cap angle of the same part number in accordance with Sikorsky Maintenance Manual SA 4047-76-2, or approved equivalent procedures as noted in paragraph (d) of this AD.
(7) Reinstall the tail rotor drive shaft fairings after the inspections and rework, as necessary, of paragraphs (c)(1) through (c)(6) are completed.
(d) Alternate inspections, repairs, modifications, or other means of compliance which provide an equivalent level of safety, may be used if approved by the Manager, Boston Aircraft Certification Office, FAA, New England Region, 12 New England Executive Park,Burlington, Massachusetts, 01803.
(e) On request of an operator, an FAA maintenance inspector, subject to prior approval of the Manager, Boston Aircraft Certification Office, may extend the repetitive inspection interval specified in this AD if the request contains justifying data.
(f) This amendment supersedes Amendment 39-4711 (48 FR 39052, August 29, 1983), AD 83-17-07, as amended by Amendment 39-5017 (50 FR 15099, April 17, 1985), AD 83-17-07 R1, and by Amendment 39-5332 (51 FR 24134, July 2, 1986), AD 83-17-07 R2.
(g) This amendment (39-8100, AD 91-24-13) becomes effective on December 20, 1991.