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; Amendment 39-11102; AD 99-07-16]

RIN 2120-AA64

Airworthiness Directives; Sikorsky Aircraft-manufactured Model

CH-54A Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: 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.

EFFECTIVE DATE: May 6, 1999.

FOR FURTHER INFORMATION CONTACT: 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: 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.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comment received.

The 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.

After 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.

The 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.

The 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.

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.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

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:

[[Page 15670]]

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.

Sec. 39.13 [Amended]

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

to read as follows:

AD 99-07-16 Columbia Helicopter; Heavy Lift; Silver Bay Logging:

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.

(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 deg.

F to 120 deg. 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).

BILLING CODE 4910-13-P

[[Page 15671]]

[GRAPHIC] [TIFF OMITTED] TR01AP99.000

[[Page 15672]]

(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.

[GRAPHIC] [TIFF OMITTED] TR01AP99.001

BILLING CODE 4910-13-C

[[Page 15673]]

(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,

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 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 May 6, 1999.

Issued in Fort Worth, Texas, on March 25, 1999.

Mark R. Schilling,

Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.

[FR Doc. 99-7978 Filed 3-31-99; 8:45 am]

BILLING CODE 4910-13-P