89-04-01 R3 SIKORSKY AIRCRAFT: Amendment 39-6131, as revised by Amendment 39- 6279 and 39-6340, is further revised by Amendment 39-6451. Docket No. 88-ASW-56.
Applicability: Model S-61N and S-61NM helicopters, certificated in any category.
Compliance: Required as indicated, unless already accomplished.
To preclude possible fracture of the sponson truss assembly components, accomplish the following:
(a) Within the next 100 hours' time in service after the effective date of this AD, conduct a hardness test of each welded lug of sponson truss tube assemblies, Part Number (P/N) S6125-51212-4 and 61250-51233-042, aft lower truss tube assembly-left side; S6125- 51212-5 and 61250-51233-043, aft lower truss tube assembly-right side; S6125-51214-3 and 61250-51235-041, forward upper truss assembly-left and right side; and S6125-51214-4 and 61250-51235-042, aft upper truss tube assembly-left and right side as follows:
NOTE: Tube assemblies with single piece end fittings do not require a hardness check of the lug.
(1) Remove paint from lugs using a clean cloth dampened with suitable paint remover.
NOTE: Paint remover in compliance with MIL-R-81294 is acceptable.
(2) Rinse lugs with fresh water and wipe dry.
(3) Using a portable calibrated Rockwell hardness tester such as Wilson Model M-51, or FAA-approved equivalent, conduct a hardness test on any exposed area of the lug that is inboard of the edge and away from the weld, using the Rockwell C-scale. Repeat the test three times. Maintain a distance of at least three penetration diameters between tester indentations.
NOTE: Removal of the truss component from the helicopter for the hardness test is not required; however, removal is recommended to improve consistency of hardness readings obtained.
(4) If the variation of hardness readings exceeds a three-point spread on the Rockwell C-scale, repeat the test until any three readings have a variation within a three-point spread.
(5) Determine the average of these three readings and mark the average value of three Rockwell C-scale hardness readings on the welded lug to indicate the test has been done. Use a vibro-peen pencil or equivalent FAA-approved marking method.
(6) Dispose of the components as follows:
(i) If the lug average hardness is less than Rockwell C34, replace the component with a serviceable part before further flight.
(ii) If the lug average hardness is in the proper range, Rockwell C39 to C43, the component is serviceable provided the component is inspected for cracks in accordance with the requirements of paragraph (b) of this AD.
(iii) If the lug average hardness is a range of Rockwell C34 to less than C39 or above C43, the part is serviceable provided the component is inspected for cracks as prescribed in paragraph (b)(1) through (9) of this AD at intervals not to exceed 500 landings and removed from service not later than June 30, 1989.(7) Repaint cleared areas with primer coating and paint, and reinstall jacking pad if removed for lug inspection.
NOTE: Sikorsky Aircraft Alert Service Bulletin No. 61B25-15, Part IIA, pertains to the hardness test required by this AD.
(b) Prior to the accumulation of 1,000 landings after the effective date of this AD, and thereafter at intervals not to exceed those landing intervals stated in Table 1, inspect the sponson truss tube assemblies for cracks in the locations noted in the table as follows:
TABLE 1
INSPECTION SCHEDULE AND LOCATIONS
Paragraph (b)
Inspection Interval,
Number of Landings
Sponson Truss
Tube Assembly
P/N
Inspection Locations
2500
S6125-51212-1
61250-51233-041
Inboard & outboard tube-to-fitting
welds and clevis. Two welded
manufacturing holes
S6125-51212-4, -5
S6125-51214-3, -4
61250-51233-042, -043
61250-51235-041, -042
Inboard & outboard tube-
to-fitting welds
Two welded manufacturing holesS6125-51213-1, -041
Inboard tube-to-fitting weld
61250-51234-041
Welded manufacturing hole
4700
S6125-51212-4, -5
Lug-to-fitting weld
S6125-51214-3, -4
Lug hole
61250-51233-042, -043
Lug hole
61250-51235-041, -042
Lug-to-fitting weld
(if applicable)
S6125-51217-1, -041
Clevis lug hole
(1) Raise the helicopter using jacks to unload the trusses.
NOTE: Jacking is described in Sikorsky Maintenance Manual, SA 4045-80, Section 7-2- 0.
(2) Remove the left and right upper and lower truss tube assemblies, and diagonal brace assemblies from the helicopter sponsons.
NOTE: Sponson removal is described in Sikorsky Maintenance Manual, SA 4045-80, Section 32-10-1.
(3) Remove paint from lugs, fittings, and welded manufacturing holes indicated in Table 1 using a clean cloth dampened with suitable paint remover (ref. paragraph (a)(1) NOTE.) Rinse with fresh water and dry.
(4) Inspect the cleanedareas identified in Table 1, using a fluorescent penetrant or equivalent inspection method.
(5) If cracks are found, replace the component with a serviceable part prior to further flight.
(6) If no cracks are found, repaint cleaned areas with suitable primer coating and paint.
(7) Reassemble and install the sponson.
(8) Seal pockets, joints, rivets, bolts, nuts, and inspection holes of all tube and brace assemblies with brush-type sealing compound such as PR-1440, Class A, Products Research and Chemical Corporation, or Pro-Seal 890, Class A, Essex Chemical Co., or FAA-approved equivalent, after reassembly of landing gear.
(9) Remove jacks.
NOTE: Sikorsky Alert Service Bulletin No. 61B25-15, Part III A (3), (4), (6), (7), (8), and (9) pertains to the inspections required by this AD.
An alternate method of compliance or adjustment of the compliance schedule which provides an equivalent level of safety, may be used if approved by the Manager, Boston Aircraft Certification Office, Engine and Propeller Directorate, Aircraft Certification Service, FAA, 12 New England Executive Park, Burlington, Massachusetts 01803, telephone (617) 273-7118.
Substantiating data compiled by an owner or operator must be submitted through the cognizant FAA Aviation Safety Inspector to support and recommend the request for compliance time adjustment.
This amendment further amends Amendment 39-6131 (54 FR 6512; February 13, 1989), AD 89-04-01, as amended by Amendment 39-6279, AD 89-04-01 R1, (54FR 31505; July 31, 1989) and by Amendment 39-6340, AD 89-04-01 R2, (54 FR 40639; October 3, 1989).
This amendment (39-6451, AD 89-04-01 R3) becomes effective on February 5, 1990.