AD Amdt-39-10943

[Federal Register Volume 63, Number 241 (Wednesday, December 16, 1998)]
[Rules and Regulations]
[Pages 69177-69178]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 98-33106]



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Federal Register / Vol. 63, No. 241 / Wednesday, December 16, 1998 / 
Rules and Regulations

[[Page 69177]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-SW-29-AD; Amendment 39-10943; AD 98-26-02]


Airworthiness Directives; Sikorsky Aircraft Corporation Model S-
61A, D, E, L, N, NM, R, and V 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 Corporation Model S-61A, D, E, L, N, 
NM, R, and V helicopters, that requires a nondestructive inspection 
(NDI) for cracks in the main rotor shaft (shaft), and requires removal 
of any shaft with a crack and replacement with an airworthy shaft. This 
AD also requires appropriate marking of shafts and log book entries by 
the operator to determine the shaft retirement life, and establishes a 
new retirement life for the shaft. This amendment is prompted by four 
reports of cracks occurring in helicopters that were utilized in 
repetitive external lift (REL) operations. The actions specified by 
this AD are intended to detect a fatigue crack in the shaft that could 
result in shaft structural failure, loss of power to the main rotor, 
and subsequent loss of control of the helicopter.

DATES: Effective January 20, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of January 20, 1999.

ADDRESSES: The service information referenced in this AD may be 
obtained from Sikorsky Aircraft Corporation, Attn: Manager, Commercial 
Tech Support, 6900 Main Street, P.O. Box 9729, Stratford, CT 06497-
9129. This information may be examined at the FAA, Office of the 
Regional Counsel, Southwest Region, 2601 Meacham Blvd., Room 663, Fort 
Worth, Texas 76137; or at the Office of the Federal Register, 800 North 
Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT:
Wayne Gualzetti, Aerospace Engineer, ANE-150, 12 New England Executive 
Park, Burlington, MA 01803, telephone (781) 238-7156, fax (781) 238-
7199.

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 Corporation 
Model S-61A, D, E, L, N, NM, R, and V helicopters was published in the 
Federal Register on September 18, 1997 (62 FR 48961). That action 
proposed to require a NDI of the shaft, part number (P/N) S6135-20640-
001, S6135-20640-002, or S6137-23040-001, used in REL operations within 
the next 1,000 hours time-in-service (TIS). The NDI must be performed 
in accordance with the Overhaul Manual. That action also proposed to 
establish retirement lives for certain shafts utilized in REL 
operations. For shafts installed on helicopters utilized in REL 
operations that have not been modified in accordance with Sikorsky 
Customer Service Notice (CSN) 6135-10, dated March 18, 1987, and 
Sikorsky Alert Service Bulletin (ASB) No. 61B35-53, dated December 2, 
1981, the retirement life would be 1,500 hours TIS. For shafts 
installed on helicopters utilized in REL operations that have been 
modified in accordance with Sikorsky CSN 6135-10, dated March 18, 1987, 
and Sikorsky ASB No. 61B35-53, dated December 2, 1981, the retirement 
life would be 2,000 hours TIS.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    Several commenters state that the cost of a replacement shaft, 
which is $44,753, should be stated in the AD to indicate the severity 
of the cost impact this AD will have on owners and operators. The FAA 
concurs and will include the cost of the shaft in the AD.
    One commenter states that issuance of the AD is unnecessary 
because, over a period of 38 years, there have been only two 
occurrences of shaft cracks. The FAA does not concur. There have been a 
total of four reported instances of cracked shaft flanges. All four 
shafts were used in REL operations. Subsequent tests conducted by the 
manufacturer confirmed the failure due to REL cycles and the need for 
the life limitation.
    The same commenter states that the AD should be applicable to Model 
CH-3C, CH-3E, HH-3C, and HH-3E helicopters. The FAA concurs since these 
restricted category helicopters are equipped with the same main gearbox 
and shaft. These models will be the subject of future rulemaking 
action.
    Two commenters state that the proposed retirement life should be 
increased from 2,000 hours TIS to 2,500 hours TIS. The change is 
requested so that the shaft retirement time will be in line with 
existing gearbox overhaul requirements. The FAA partially concurs. This 
change will allow the shaft replacement to be conducted concurrently 
with any recommended gearbox overhaul actions. Based on a further 
evaluation of the dowel pin cracking and the fretting cracking, the FAA 
has determined that the retirement life can safely be increased from 
the proposed 2,000 hours TIS to 2,200 hours TIS. This will allow 
operators to get two overhaul cycles of 1,100 hours TIS for each shaft 
used in REL operations. Therefore, the retirement life is extended from 
2,000 hours TIS to 2,200 hours TIS for shafts that have been modified 
in accordance with the Sikorsky service information described 
previously. This change also will allow operators to avoid excessive 
disassembly and re-assembly of the gearbox for overhauls and shaft 
removal based on an approved 1,100 hours TIS gearbox overhaul cycle.
    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 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 30 helicopters of U.S. registry that are 
involved in REL operations will be affected by this AD, that it will 
take approximately 2.2 work hours per helicopter to accomplish the

[[Page 69178]]

required actions during the next scheduled overhaul, and that the 
average labor rate is $60 per work hour. Required parts will cost 
approximately $50 for the inspection and $44,753 for each shaft. Based 
on these figures, the total cost impact of the AD on U.S. operators is 
estimated to be $1,348,050, assuming all 30 shafts are replaced.
    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 location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, 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:

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 98-26-02  Sikorsky Aircraft Corporation: Amendment 39-10943. 
Docket No. 96-SW-29-AD.

    Applicability: Model S-61A, D, E, L, N, NM, R, and V 
helicopters, with main rotor shaft (shaft), part number (P/N) S6135-
20640-001, S6135-20640-002, or S6137-23040-001, 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 (e) 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 change 
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 detect a fatigue crack in the shaft that could result in 
shaft structural failure, loss of power to the main rotor, and 
subsequent loss of control of the helicopter, accomplish the 
following:
    (a) Within the next 30 calendar days or 240 hours time-in-
service (TIS) after the effective date of this AD, whichever occurs 
first, determine if the shaft has been used in repetitive external 
lift (REL) operations. REL operation is defined as operation during 
which the average number of external lifts equals or exceeds six per 
flight hour for any 250 hour TIS period during the main gearbox 
overhaul interval. An external lift is defined as a flight cycle in 
which an external load is picked up, the helicopter is repositioned 
(through flight or hover), and the helicopter hovers and releases 
the load and departs or lands and departs. Record the total number 
of hours TIS during which external lifts have been conducted, as 
well as the number of external lifts conducted during each hour, on 
the component log card or equivalent record. If the number of 
external lifts cannot be determined, assume 6 external lifts were 
conducted during each hour TIS in which external lifts were 
conducted. If the hours TIS of external lift operations cannot be 
determined, assume REL operations were conducted.
    (b) For shafts used in REL operations, within the next 1,100 
hours TIS after the effective date of this AD, conduct a non-
destructive inspection (NDI) for cracks in the shaft in accordance 
with the Overhaul Manual. If a crack is discovered in a shaft, 
remove the shaft and replace it with an airworthy shaft. Mark the 
removed airworthy shafts and the replacement shafts in accordance 
with the Accomplishment Instructions in paragraphs 2E and 2f of 
Sikorsky Aircraft Corporation Alert Service Bulletin (ASB) No. 
61B35-68, dated July 19, 1996. Once a shaft has been designated and 
marked as an REL shaft, it is life-limited accordingly for the 
remainder of that shaft's airworthy service life.
    (c) Retire all shafts that have been used in REL operations as 
follows:
    (1) Shafts that have been modified in accordance with Sikorsky 
Customer Service Notice 6135-10, dated March 18, 1997, and Sikorsky 
ASB No. 61B35-53, dated December 2, 1981 (modified REL shafts), must 
be removed from service on or before attaining 2,200 hours TIS.
    (2) Shafts that have not been modified in accordance with 
Sikorsky Customer Service Notice 6135-10, dated March 18, 1987, and 
Sikorsky ASB 61B35-53, dated December 1981 (unmodified REL shafts), 
must be removed from service on or before attaining 1,500 hours TIS.
    (d) This AD revises the Limitations section of the maintenance 
manual by establishing new retirement lives of 1,500 hours TIS for 
unmodified REL shafts and 2,200 hours TIS for modified REL shafts.
    (e) 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, Boston Aircraft Certification 
Office. Operators shall submit their requests through an FAA 
Principal Maintenance Inspector, who may concur or comment and then 
send it to the Manager, Boston Aircraft Certification Office.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Boston Aircraft Certification Office.

    (f) 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.
    (g) The marking of the shaft shall be done in accordance with 
Sikorsky Aircraft Corporation Alert Service Bulletin No. 61B35-68, 
dated July 19, 1996. This incorporation by reference was approved by 
the Director of the Federal Register in accordance with 5 U.S.C. 
552(a) and 1 CFR part 51. Copies may be obtained from Sikorsky 
Aircraft Corporation, Attn: Manager, Commercial Tech Support, 6900 
Main Street, P.O. Box 9729, Stratford, CT 06497-9129. Copies may be 
inspected at the FAA, Office of the Regional Counsel, Southwest 
Region, 2601 Meacham Blvd., Room 663, Fort Worth, Texas; or at the 
Office of the Federal Register, 800 North Capitol Street, NW., suite 
700, Washington, DC.
    (h) This amendment becomes effective on January 20, 1999.

    Issued in Forth Worth, Texas, on December 7, 1998.
Henry A. Armstrong,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 98-33106 Filed 12-15-98; 8:45 am]
BILLING CODE 4910-13-U