AD 99-07-16

This amendment adopts a new airworthiness directive (AD), applicable to Sikorsky Aircraft-manufactured Model CH-54A helicopters, that requires an initial and recurring inspections and rework or replacement, if necessary, of the second stage lower planetary plate (plate). This amendment is prompted by cracked plates that have been found during overhaul and inspections. The actions specified by this AD are intended to prevent failure of the plate due to fatigue cracking, which could result in failure of the main gearbox, failure of the drive system, and subsequent loss of control of the helicopter.

Final rule

99-07-16 COLUMBIA HELICOPTER; HEAVY LIFT; SILVER BAY LOGGING: Amendment 39-11102. Docket No. 97-SW-60-AD.\n\n\tApplicability: Model CH-54A helicopters with lower planetary plate, part number (P/N) 6435-20229-102, installed, certificated in any category.\n\n\tNOTE 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 (d) 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.\n\n\tCompliance: Required as indicated, unless accomplished previously.\n\n\tTo prevent failure of the second stage lower planetary plate (plate), P/N 6435-20229-102, due to fatigue cracking, which could lead to failure of the main gearbox, failure of the drive system, and subsequent loss of control of the helicopter, accomplish the following:\n\n\t(a)\tOn or before accumulating 1,300 hours time-in-service (TIS), conduct a fluorescent magnetic particle inspection of the plate, P/N 6435-20229-102, in the circumferential and longitudinal directions using the wet continuous method. Pay particular attention to the area around the 9 lightening holes.\n\n\t\t(1)\tIf any crack is discovered, replace the plate with an airworthy plate.\n\n\t\t(2)\tIf no crack is discovered, rework the plate as follows:\n\n\t\t\t(i)\tLocate the center of each 1.750 inch-diameter lightening hole and machine holes 0.015 to 0.020 oversize on a side (0.030 to 0.040 diameter oversize). Machined surface roughness mustnot exceed 63 microinches AA rating (see Figure 1).\n\n\t\t\t(ii)\tRadius each hole 0.030 to 0.050 inches on each edge as shown in Figure 1.\n\n\t\t\t(iii)\tMask the top and bottom surfaces of the plate to expose 3.20 inch minimum width circumferential band as shown in Figure 1.\n\n\t\t\t(iv)\tVapor blast or bead exposed surfaces to remove protective finish. Use 220 aluminum oxide grit at a pressure of 80 to 90 pounds per square inch.\n\n\t\t\t(v)\tShot peen exposed surfaces and inside and edges of lightening holes to 0.008 - 0.012A intensity. Use cast steel shot, size 170; 200 percent coverage is required. Use the tracer dye inspection method to ensure the required coverage. Also, visually inspect the shot peened surfaces for correct shot peen coverage. Inspect the intensity of the shot by performing an Almen strip height measurement.\n\n\t\t\t(vi)\tClean reworked surfaces using acetone. Touch up the reworked areas using Presto Black or an equivalent touchup solution. Ensure that the touchup solution is at a temperature between 70° F to 120° F during use. Keep the reworked surfaces wet with touchup solution for 3 minutes to obtain a uniform dark color. Rinse and dry the reworked areas.\n\n\t\t\t(vii)\tPolish the reworked surfaces with a grade 00 or finer steel wool and polish with a soft cloth. Coat the reworked surfaces with preservative oil.\n\n\t\t\t(viii)\tIdentify the reworked plate by adding "TS-107" after the part number using a low-stress depth-controlled impression-stamp with a full fillet depth of not more than 0.003 inch (see Figure 1).\n\n\t(b)\tFor any plate, P/N 6435-20229-102, that has been reworked and identified with "TS-107," on or before the accumulation of 1,500 hours TIS and thereafter at intervals not to exceed 70 hours TIS, accomplish the following:\n\n\t\t(1)\tInspect the plate for a crack in the area around all nine lightening holes using a Borescope or equivalent inspection method (see Figure 2).\n\n\t\t(2)\tIf a crack is found, replace the plate with an airworthyplate.\n\n\t(c)\tOn or before the accumulation of 2,600 hours TIS, remove from service plates, P/N 6435-20229-102, reidentified as P/N 6435-20229-102-TS-107 after rework. This AD revises the airworthiness limitation section of the maintenance manual by establishing a retirement life of 2,600 hours TIS for the main gearbox assembly second stage lower planetary plate, P/N 6435-20229-102, reidentified as P/N 6435-20229-102-TS-107 after rework.\n\n\t(d)\tAn 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, Rotorcraft Certification Office, FAA, Rotorcraft Directorate. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Rotorcraft Certification Office.\n\n\tNOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Rotorcraft Certification Office.\n\n\t(e)\tSpecial flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the helicopter to a location where the requirements of this AD can be accomplished.\n\n\t(f)\tThis amendment becomes effective on May 6, 1999.\n\n\n\n\nRework of Second Stage\nLower Planetary Plate (6435-20229-102)\nFigure 1\nAD 99-07-16\n\n\n\nBorescope Inspection of\nSecond Stage Lower Planetary Plate\nFigure 2\nAD 99-07-16

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to Sikorsky Aircraft-manufactured Model CH-54A helicopters was published in the Federal Register on February 10, 1998 (63 FR 6685). That action proposed to require an initial and recurring inspections and rework or replacement, if necessary, of the plate. It is believed that cracks on the plate, part number 6435-20229-102, initiate at and radiate from the lightening holes in the plate web due to fatigue.\n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comment received.\n\n\tThe sole commenter states that the inclusion of an Erickson Air-Crane Company Service Bulletin (SB) in the Compliance Section of the AD should be removed. The commenter states that the FAA does not have the authority to utilize Erickson Air-Crane Company documentation for continued airworthiness of CH-54A model helicopters or any other helicopters other than Erickson Air-Crane S-64E helicopters. The FAA concurs with the comment to the extent that the Erickson Air-Crane SB only applies to the Erickson Air-Crane Company Model S-64E series helicopters. However, Note 2 of the Notice of Proposed Rulemaking (NPRM) only stated that the Erickson Air-Crane SB pertained to the same subject as is addressed by the FAA in this rule. It was not incorporated by reference into the compliance procedures proposed by the NPRM. However, to avoid any confusion as to the model applicability, the FAA has deleted proposed Note 2 relating to the Erickson Air-Crane Company SB because the note is unnecessary. Also, the wording of Note 1 has changed from that published in the NPRM.\n\n\tAfter careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.\n\n\tThe FAA estimates that 9 helicopters of U.S. registry will be affected by this AD, that it will take approximately 8 work hours per helicopter to accomplish the proposed inspections and 56 hours to remove and replace the plate, and that the average labor rate is $60 per work hour. Required parts will cost approximately $8,000 per helicopter. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $106,560; $4,320 to accomplish the inspections and rework, and $102,240 to replace the plate in the main gearbox assembly in all 9 helicopters, if necessary.\n\n\tThe regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.\n\n\tFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the FAA, Office of the Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas.\n\nList of Subjects in 14 CFR Part 39\n\tAir transportation, Aircraft, Aviation safety, Safety.\n\nAdoption of the Amendment\n\tAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:\n\nPART 39 - AIRWORTHINESS DIRECTIVES\n\t1. The authority citation for part 39 continues to read as follows:\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701.\n\n§ 39.13 (Amended)\n\t2. Section 39.13 is amended by adding a new airworthiness directive to read as follows: