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Airworthiness Directives; Sikorsky Aircraft-Manufactured Model CH-54A Helicopters

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Information about this document as published in the Federal Register.

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Federal Aviation Administration, DOT.


Final rule.


This amendment supersedes an existing airworthiness directive (AD) that applies to Sikorsky Aircraft-manufactured Model CH-54A helicopters. That AD currently requires initial and recurring inspections and rework or replacement, if necessary, of the second stage lower planetary plate (plate). This AD requires the same actions as the existing AD but would add two additional type certificate (TC) holders to the applicability of the AD and change one TC holder who has transferred ownership of the affected helicopters since the issuance of the existing AD. This amendment is prompted by the discovery that the applicability section of the existing AD is incomplete. 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.


October 19, 2000.

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Uday Garadi, Aviation Safety Engineer, FAA, Rotorcraft Directorate, Rotorcraft Standards Staff, Fort Worth, Texas 76193-0110, telephone (817) 222-5123, fax (817) 222-5961.

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A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 99-07-16, Amendment 39-11102 (64 FR 15669, April 1, 1999), which applies to Sikorsky Aircraft-manufactured Model CH-54A helicopters, was published in the Federal Register on April 20, 2000 (65 FR 21159). That action proposed to require initial and recurring inspections and rework or replacement, if necessary, of the plate.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

The sole commenter indicates that the cost figures utilized in the economic analysis are incorrect. The FAA agrees; therefore, the approximate cost of procuring a new plate assembly is revised to $37,333. The total cost impact of the AD is estimated to be $507,360 to replace the plate assemblies in the entire fleet, if necessary.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed except for the change in the economic analysis.

The FAA estimates that 12 helicopters of U.S. registry will be affected by this AD. It will take approximately 8 work hours per helicopter to accomplish the inspection; 24 work hours per Start Printed Page 55454helicopter to remove and rework the assembly; and 56 work hours to remove and replace the assembly from each helicopter, if necessary. Required parts, if an assembly needs to be replaced, will cost approximately $37,333. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $511,356 ($42,613 per helicopter, assuming inspecting the plate once, reworking the assembly once, and replacing the assembly).

The regulations adopted herein will not have a substantial direct effect 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, it is determined that this final rule does not have federalism implications under Executive Order 13132.

For 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.

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List of Subjects in 14 CFR Part 39

  • Air transportation
  • Aircraft
  • Aviation safety
  • Safety
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Adoption of the Amendment

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Accordingly, 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:

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1. The authority citation for part 39 continues to read as follows:

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Authority: 49 U.S.C. 106(g), 40113, 44701.

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2. Section 39.13 is amended by removing Amendment 39-11102 ( 64 FR 15669, April 1, 1999), and by adding a new airworthiness directive (AD), Amendment 39-11901, to read as follows:

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2000-18-14  Siller Helicopters; Aviation International Rotors, Inc. (AIR, INC); Columbia Helicopters, Inc.; Chet Raspberry, Inc. (CRI); Silver Bay Logging, Inc.: Amendment 39-11901. Docket No. 99-SW-81-AD. Supersedes AD 99-07-16, Amendment 39-11102, Docket No. 97-SW-60-AD.

Applicability: Model CH-54A helicopters with lower planetary plate, part number (P/N) 6435-20229-102, installed, 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 (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.

Compliance: Required as indicated, unless accomplished previously.

To 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:

(a) On 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.

(1) If any crack is discovered, replace the plate with an airworthy plate prior to further flight.

(2) If no crack is discovered, rework the plate as follows:

(i) Locate 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 must not exceed 63 microinches AA rating (see Figure 1).

(ii) Radius each hole 0.030 to 0.050 inches on each edge as shown in Figure 1.

(iii) Mask the top and bottom surfaces of the plate to expose 3.20 inch minimum width circumferential band as shown in Figure 1.

(iv) Vapor 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.

(v) Shot 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.

(vi) Clean 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.

(vii) Polish the reworked surfaces with a grade 00 or finer steel wool and polish with a soft cloth. Coat the reworked surfaces with preservative oil.

(viii) Identify 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).

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(b) For 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:

(1) Inspect the plate for a crack in the area around all nine lightening holes using a Borescope or equivalent inspection method (see Figure 2).

(2) If a crack is found, replace the plate with an airworthy plate prior to further flight.

(c) On 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.

(d) 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, Rotorcraft Certification Office, Rotorcraft Directorate, FAA. 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.

Note 2:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Rotorcraft Certification Office.

(e) Special 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.

(f) This amendment becomes effective on October 19, 2000.

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Issued in Fort Worth, Texas, on September 5, 2000.

Henry A. Armstrong,

Manager, Rotorcraft Directorate, Aircraft Certification Service.

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[FR Doc. 00-23583 Filed 9-13-00; 8:45 am]