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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-SW-60-AD]

Airworthiness Directives; Sikorsky Aircraft-Manufactured Model

CH-54A Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness

directive (AD) that is applicable to Sikorsky Aircraft-manufactured

Model CH-54A helicopters. This proposal would require an initial and

recurring inspections and rework or replacement, if necessary, of the

second stage lower planetary plate (plate). This proposal is prompted

by cracked plates that have been found during overhaul and inspections.

The actions specified by the proposed 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.

DATES: Comments must be received on or before April 13, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Office of Regional Counsel, Southwest Region,

Attention: Rules Docket No. 97-SW-60-AD, 2601 Meacham Blvd., Room 663,

Fort Worth, Texas 76137. Comments may be inspected at this location

between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal

holidays.

FOR FURTHER INFORMATION CONTACT: Mr. Uday Garadi, Aerospace Engineer,

FAA, Rotorcraft Directorate, Rotorcraft Certification Office, Fort

Worth, Texas 76193-0170, telephone (817) 222-5157, fax (817) 222-5959.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the

proposed rule by submitting such written data, views, or arguments as

they may desire. Communications should identify the Rules Docket number

and be submitted in triplicate to the address specified above. All

communications received on or before the closing date for comments,

specified above, will be considered before taking action on the

proposed rule. The proposals contained in this notice may be changed in

light of the comments received.

Comments are specifically invited on the overall regulatory,

economic, environmental, and energy aspects of the proposed rule. All

comments submitted will be available, both before and after the closing

date for comments, in the Rules Docket for examination by interested

persons. A report summarizing each FAA-public contact concerned with

the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this notice must submit a self-addressed,

stamped postcard on which the following

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statement is made: ``Comments to Docket No. 97-SW-60-AD.'' The postcard

will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request

to the FAA, Office of Regional Counsel, Southwest Region, Attention:

Rules Docket No. 97-SW-60-AD, 2601 Meacham Blvd., Room 663, Fort Worth,

Texas 76137.

Discussion

This notice proposes the adoption of a new AD that is applicable to

Sikorsky-manufactured Model CH-54A helicopters. This proposal would

require an initial and recurring inspections and rework of the plate or

replacement, if necessary. It is believed that cracks on the plate

initiate at and radiate from the lightening holes in the plate web due

to fatigue. This condition, if not corrected, could result in failure

of the main gearbox, failure of the drive system, and subsequent loss

of control of the helicopter.

Since an unsafe condition has been identified that is likely to

exist or develop on other Sikorsky-manufactured Model CH-54A

helicopters of the same type design, the proposed AD would require an

initial and recurring inspections and replacement, if necessary, of the

plate.

The FAA estimates that 9 helicopters of U.S. registry would be

affected by this proposed AD, that it would 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 would 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.

The regulations proposed herein would 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

proposal would not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this proposed

regulation (1) is not a ``significant regulatory action'' under

Executive Order 12866; (2) is not a ``significant rule'' under the DOT

Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);

and (3) if promulgated, 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 copy of the draft

regulatory evaluation prepared for this action is contained in the

Rules Docket. A copy of it may be obtained by contacting the Rules

Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration proposes to amend

part 39 of the Federal Aviation Regulations (14 CFR part 39) as

follows:

PART 39--AIRWORTHINESS DIRECTIVES

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

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

2. Section 39.13 is amended by adding a new airworthiness directive

to read as follows:

Sec. 39.13 [Amended]

Columbia Helicopter; Heavy Lift; Silver Bay Logging: Docket No. 97-

SW-60-AD.

Applicability: 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

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 use the authority

provided in paragraph (d) to request approval from the FAA. This

approval may address either no action, if the current configuration

eliminates the unsafe condition, or different actions necessary to

address the unsafe condition described in this AD. Such a request

should include an assessment of the effect of the changed

configuration on the unsafe condition addressed by this AD. In no

case does the presence of any modification, alteration, or repair

remove any helicopter from the applicability of this AD.

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.

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

(i) Locate the center of each 1.750 inch-diameter lightning 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; two hundred 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 deg.

F to 120 deg. F during use. Keep the reworked surfaces wet with

touchup solution for three 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.

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(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, re-

identified as P/N 6435-20229-102-TS-107 after rework.

Note 2: Erickson Air-Crane Company Service Bulletin No. 64B35-

7C, dated November 8, 1995 pertains to the subject of this AD.

(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,

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.

Note 3: 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.

Issued in Fort Worth, Texas, on February 3, 1998.

Eric Bries,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 98-3228 Filed 2-9-98; 8:45 am]

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