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

[Federal Register Volume 64, Number 140 (Thursday, July 22, 1999)]
[Rules and Regulations]
[Pages 39398-39403]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-18683]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-SW-59-AD; Amendment 39-11235; AD 99-15-14]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

EFFECTIVE DATE: August 26, 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-54B helicopters was published in the Federal Register on April 
16, 1999 (64 FR 18835). 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. No comments were received on the 
proposal or the FAA's determination of the cost to the public. The FAA 
has determined that air safety and the public interest require the 
adoption of the rule as proposed.
    The FAA estimates that 4 helicopters of U.S. registry will be 
affected by this AD, that it will take approximately 8 work hours per 
helicopter to accomplish the borescope inspection, 1 work hour to 
inspect the main gearbox oil filter pack, 140 work hours to remove and 
replace the main gearbox assembly, if necessary, and 20 work hours to 
rework 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 AD on U.S. operators is 
estimated to be $67,760; $2,160 to accomplish the initial inspections 
and $65,600 to replace the plate in the main gearbox assembly in all 4 
helicopters, if necessary. Daily preflight inspections of the main 
gearbox oil filter pack will cost $60 per helicopter for each day 
flight is conducted.
    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 Office of the Regional Counsel, Southwest 
Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas 76137.

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

[[Page 39399]]

Administrator, the Federal Aviation Administration amends 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.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding a new airworthiness directive 
to read as follows:

AD 99-15-14  Blue Bird Helicopters: Amendment 39-11235. Docket No. 
97-SW-59-AD.

    Applicability: CH-54B helicopters with main gearbox second stage 
lower planetary plate (plate), part number (P/N) 6435-20516-101, 
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 (c) 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 plate due to fatigue cracking, which 
could lead to failure of the main gearbox and subsequent loss of 
control of the helicopter, accomplish the following:
    (a) For main gearbox assemblies containing plate, part number 
(P/N) 6435-20516-101, with 1,600 or more hours time-in-service 
(TIS):

    Note 2: If the TIS hours of the plate is not known, use the main 
gearbox assembly's total operating time.

    (1) Prior to the first flight of each day, inspect the main oil 
filter for magnesium contamination. If magnesium contamination is 
discovered, replace the main gearbox assembly.
    (2) Within the next 100 hours TIS after the effective date of 
this AD, and thereafter at intervals not to exceed 200 hours TIS, 
conduct a borescope inspection of the plate for cracks in the area 
of the nine lightening holes (see Figure 1). If a crack is found, 
replace the plate with an airworthy plate. The plate, P/N 6435-
20516-101, is part of the main gearbox second stage planetary set 
(P/N 6435-20514-041), which is a serialized matched set, and must be 
replaced as a set.

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    (b) At the next overhaul of the main gearbox assembly, inspect 
and rework the plate, P/N 6435-20516-101, as follows:
    (1) Fluorescent magnetic particle inspect the plate per ASTM 
E1444 in circumferential and longitudinal directions using a wet 
continuous method. Pay particular attention to the area around the 
nine 1.750-inch diameter lightening holes.
    (2) If a crack is found, the plate is unairworthy. Replace it 
with an airworthy plate.
    (3) If no crack is found, rework the plate as follows, ensuring 
that all plate surfaces are free of any crack, scratch, dent, or 
corrosion.
    (i) Measuring from the center of each 1.750-inch diameter 
lightening hole, machine 0.015/0.020 inch from the radius of the 
hole (see Figure 2). Machined surface roughness shall not exceed 63 
microinches AA rating.

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[[Page 39403]]

    (ii) Apply a 0.030/0.050-inch radius on the top and bottom edge 
of each hole.
    (4) Fluorescent magnetic particle inspect the reworked areas per 
ASTM E1444 in circumferential and longitudinal directions using a 
wet continuous method.
    (5) If a crack is found, the plate is unairworthy. Replace it 
with an airworthy plate.
    (6) If no crack is found, rework the plate as follows:
    (i) Remove the protective finish from the specified areas on the 
top and bottom of the plate as follows:
    (A) Mask the top and bottom of the plate leaving exposed a 3.20-
inch minimum circumferential band centered on 13.75-inch diameter of 
plate (see Figure 2). Mask the area to protect the thrust washer and 
the surrounding areas from vapor blast.
    (B) Using a vapor blast machine, remove the protective finish 
from the exposed circumferential band on the top and bottom of the 
plate. Use No. 220 aluminum oxide grit at a pressure of 80-90 pounds 
per square inch.
    (ii) Shot peen the specified areas on the plate by remasking the 
top and bottom of the plate leaving exposed the 3.20-inch minimum 
circumferential band centered on 13.75-inch diameter of the plate. 
Mask the area to protect the thrust washer and the surrounding areas 
from the shot peening process.
    (iii) Shot peen the inside diameter of the lightening holes and 
the upper and lower surfaces of the plate in the 3.20-inch minimum 
circumferential band to 0.008 to 0.012A intensity, ensuring 200% 
coverage per MIL-S-13165C or latest revision. Use cast steel shot, 
size 170. Use a tracer dye inspection method.

    Note 3: Overspray is permitted to allow a feathering application 
during the peening process from the peened surface to the non-peened 
surface.

    (iv) Finish the reworked surfaces as follows:
    (A) Clean the surfaces thoroughly with acetone (Fed. Spec O-A-
51, or equivalent).
    (B) Apply Presto black or blueing touchup solution to the 
reworked surfaces with cotton swabs. The solution temperature must 
be between 21 deg. C and 49 deg. C (70 deg. F to 120 deg. F). Keep 
the surfaces wet for about three minutes to get a uniform dark 
color.
    (C) Rinse the surface in cold running water and dry with forced 
air.

    Note 4: A hot water rinse may be used after the cold water rinse 
to speed up drying time.

    (D) Using steel wool, Grade 00 or finer, rub the surfaces 
lightly. Polish with a soft cloth and then coat with a preservative 
oil (MIL-C-15074).
    (v) Identify the reworked plate by stamping the number of this 
AD after the part number. Use a low-stress depth-controlled 
impression-stamp with full fillet depth of no more than 0.003 inch 
(see Figure 2). Marking must be such that it cannot be construed as 
part of the part number.
    (c) 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 5: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Rotorcraft Certification Office.

    (d) 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.
    (e) This amendment becomes effective on August 26, 1999.

    Issued in Fort Worth, Texas, on July 15, 1999.
Henry A. Armstrong,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 99-18683 Filed 7-21-99; 8:45 am]
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