Document ID: FAA-2006-24587-0019
Agency: faa
Document Type: Rule
Title: Airworthiness Directives: Sikorsky Aircraft Corporation Model S-76A, B, and C Helicopters
Posted Date: 2010-05-13T04:00Z

[Federal Register Volume 75, Number 92 (Thursday, May 13, 2010)]
[Rules and Regulations]
[Pages 26885-26887]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-10588]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2006-24587; Directorate Identifier 2006-SW-05-AD; 
Amendment 39-16281; AD 2010-10-02]
RIN 2120-AA64

Airworthiness Directives; Sikorsky Aircraft Corporation Model S-
76A, B, and C Helicopters

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) for 
Sikorsky Aircraft Corporation (Sikorsky) Model S-76A, B, and C 
helicopters that requires inspecting each installed Woodward HRT 
(formerly HR Textron) main rotor servo actuator (servo actuator) for a 
high rate of leakage and replacing each affected servo actuator with a 
servo actuator containing a newly re-designed servo actuator piston. 
This amendment is prompted by a National Transportation Safety Board 
(NTSB) Safety Recommendation issued in response to an accident 
involving a Model S-76C helicopter. In the NTSB Safety Recommendation, 
the performance of a servo actuator piston upon reaching 3,000 hours 
time-in-service (TIS) was questioned as a result of piston head seal 
leakage and piston head plasma spray flaking. The actions specified by 
this AD are intended to prevent degraded servo actuator performance as 
a result of piston head seal leaking and plasma spray flaking, which 
could result in subsequent loss of control of the helicopter.

DATES: Effective June 17, 2010.

ADDRESSES: You may get the service information identified in this AD 
from Sikorsky Aircraft Corporation, Attn: Manager, Commercial Technical 
Support, 6900 Main Street, Stratford, Connecticut, phone (203) 383-
4866, e-mail address tsslibrary@sikorsky.com.
    Examining the Docket: You may examine the docket that contains this 
AD, any comments, and other information on the Internet at http://www.regulations.gov, or at the Docket Operations office, West Building 
Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, 
DC.

FOR FURTHER INFORMATION CONTACT: Terry Fahr, Aviation Safety Engineer, 
Boston Aircraft Certification Office, 12 New England Executive Park,

[[Page 26886]]

Burlington, MA 01803, telephone (781) 238-7155, fax (781) 238-7170.

SUPPLEMENTARY INFORMATION: A revised proposal to amend 14 CFR part 39 
to include an AD for Sikorsky Model S-76A, B, and C helicopters was 
published in the Federal Register on February 11, 2009 (74 FR 6835). 
That action, a supplemental notice of proposed rulemaking (SNPRM), 
proposed to require inspecting each installed servo actuator for a high 
rate of leakage, and if there is a high rate of leakage, replacing the 
servo actuator piston or replacing the servo actuator. The SNPRM also 
proposed replacing each affected servo actuator piston, part number (P/
N) 41004321 or RW41004321, upon reaching 3,000 hours TIS, with a newly-
designed servo actuator piston, P/N 41012001, or replacing an affected 
servo actuator with a servo actuator containing a newly-designed servo 
actuator piston. That action revised our previous proposal, issued on 
April 21, 2006, which was published in the Federal Register on May 2, 
2006 (71 FR 25783), and which proposed to require inspecting the 
hydraulic fluid for contamination; removing the requirement to reduce 
the interval for overhauling an affected servo actuator from 3,000 to 
2,000 hours TIS; revising the initial inspection time; and removing the 
600 hours TIS repetitive hydraulic fluid leak inspection.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the three comments received in response to the SNPRM. Comments 
submitted in response to the NPRM were addressed in the SNPRM.
    One commenter, Copterline Oy, states through their law firm that 
the design of the overhauled servo actuator piston head has not been 
approved by the FAA and is therefore not airworthy. They state that the 
cause of an accident involving a Sikorsky Model S-76 helicopter, which 
occurred on August 10, 2005, was plasma flaking from the piston head of 
the pistons in the forward servo actuator, which quickly led to a 
deterioration of the seals that are intended to prevent leakage. The 
commenter also states that ``testing for leakage at 500 or even 100 
hour intervals will not provide any assurance that the servo actuator 
will function even few hours after the test has been performed.'' They 
conclude that ``all unairworthy servo actuators with plasma coating 
lapped over and across the head of the piston should be removed from 
service immediately'', and that ``helicopters with these servo 
actuators should not be designated as airworthy and, accordingly, 
should be grounded and not permitted to operate.''
    We do not agree with the commenter that helicopters with the 
overhauled servo pistons in the servo actuator should be grounded 
because that makes them unairworthy. The overhaul of the pistons was 
accomplished under the authority of the repair station of the Sikorsky 
servo piston supplier using overhaul data acceptable to the FAA. The 
plasma coating work performed on the overhauled piston was a 
maintenance activity performed under the Woodward HRT (formerly HR 
Textron) overhaul procedures approved by Sikorsky and according to 
acceptable practices. The purpose of these overhaul procedures was to 
restore the piston head to its original design specifications. Our 
review of the service history of the Model S-76 helicopters prior to 
the August 2005 accident found no incidents of loss of control of a 
helicopter as a result of servo actuator leakage or plasma spray 
flaking. However, because of safety concerns surrounding the overhaul 
of these two servo pistons and the plasma spray flaking, this AD 
requires phasing these overhauled pistons out of service. No later than 
3,000 hours TIS or upon discovering fluid leakage exceeding 700 cc per 
minute, any overhauled piston must be replaced with a non-overhauled 
piston--either P/N 41012001-001, that has improved bonding qualities, 
or P/N 41012001. When these non-overhauled pistons are installed, the -
109 and -110 servo actuators must be re-identified as either Sikorsky 
or Woodward HRT -111 servo actuators. It is our intent that, although 
the servo actuator piston may no longer be overhauled, the servo 
actuator may be overhauled using a non-overhauled piston. Thus, the -
109 and -110 servo actuators are being phased out along with overhauled 
servo pistons.
    A second commenter, the NTSB, states: ``When checking servo 
actuators for contamination and leakage, the inspections must be 
redundant enough and the inspection intervals short enough to ensure 
that missing a problem during any single inspection does not result in 
a potential catastrophic failure of the aircraft.'' They state that we 
should require overhauling any affected servo actuator at intervals of 
2,000 hours TIS, and require a 600 hours TIS repetitive hydraulic fluid 
leak inspection, as stated in the proposed AD that we issued on April 
21, 2006 (71 FR 25783, May 2, 2006).
    We do not agree. Our review of the Model S-76 helicopter service 
history data prior to the August 2005 accident found no evidence of a 
helicopter control issue associated with servo actuator leakage or 
plasma spray flaking. Therefore, we believe that requiring an 
additional leakage rate inspection at 1,500 hours TIS, and, if leakage 
exceeding 700 cc per minute is found, requiring replacement of the 
servo actuator piston or replacement of the servo actuator with an 
airworthy servo actuator is sufficient to prevent degraded servo 
actuator performance as a result of piston head seal leaking and plasma 
spray flaking.
    A third commenter, Sikorsky, states that they support ``the 
majority of this SNPRM.'' However, they suggest that we replace ``HR 
Textron'' with their new name, ``Woodward HRT''; include, ``reworked 
piston'', P/N RW41004321, for removal; and add replacement piston, 
Woodward HRT P/N 4102001-001. Our understanding is that a ``reworked 
piston'' is the same as an ``overhauled piston.'' We agree and have 
made those changes.
    Sikorsky further states that the 1,500 hours check represents a new 
restrictive requirement to Chapter 4 of the Airworthiness Limitations 
and Inspection Requirements (ALIR). The 1,500 hours time-since-new 
(TSN) or time-since-overhaul (TSO) action in the AD is an 
``inspection'' that must be performed by a mechanic, not a ``check'' 
that we sometimes allow a pilot to perform. We agree that this revises 
the airworthiness limitations of the maintenance manual, and we have 
placed a statement indicating that in the AD. Further, Sikorsky states 
that this ``check'' should be performed in accordance with the 
maintenance manual. Because we have not specified an alternative manner 
for performing this ``inspection'', you must use a procedure that is 
acceptable to the FAA, which most probably will be the procedures 
stated in the maintenance manual. This is true of any maintenance 
action on all products. It is generally understood, and need not be 
stated in every AD. Therefore, no change is being made to the AD based 
on this comment. The substance of other general comments by Sikorsky 
has been addressed in the SNPRM.
    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 previously stated 
changes.
    We estimate that this AD will affect 300 helicopters (900 servo 
actuators) of U.S. registry. We also estimate that the leakage rate 
inspection will take about 1 work hour per servo actuator at an

[[Page 26887]]

average labor rate of $85 per work hour, and the two leakage rate 
inspections on 900 servo actuators will cost about $153,000. We 
estimate that 6 servo actuators, Sikorsky P/N 76650-09805-109 or -110, 
will need to be replaced with servo actuators, Sikorsky P/N 76650-
09805-111. Assuming an estimated 8 work hours per servo actuator for 
installation and a cost of $57,000 per servo actuator, the total cost 
of installing these servo actuators will be $346,080. We estimate that 
the cost of replacing the pistons in the remaining 894 servo actuators 
will cost $7,321,860, assuming 14 work hours to replace the pistons and 
install the servo actuator, and a cost of $3,500 per piston (2 pistons 
per servo). Therefore, the total estimated cost of this AD is 
$7,820,940.

Regulatory Findings

    We have determined that this AD will not have federalism 
implications under Executive Order 13132. This AD 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.
    For the reasons discussed above, I certify that the 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. 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.
    We prepared an economic evaluation of the estimated costs to comply 
with this AD. See the AD docket to examine the economic evaluation.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, Section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

0
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

0
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]

0
2. Section 39.13 is amended by adding a new airworthiness directive to 
read as follows:

2010-10-02 Sikorsky Aircraft Corporation: Amendment 39-16281. Docket 
No. FAA-2006-24587; Directorate Identifier 2006-SW-05-AD.
    Applicability: Model S-76A, B, and C helicopters, with a main 
rotor servo actuator (servo actuator), Sikorsky Aircraft Corporation 
(Sikorsky) part number (P/N) 76650-09805-109 or -110 (also marked as 
HR Textron or Woodward HRT P/N 3006760-109 or -110), installed, 
certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To detect leaking in a servo actuator, which could lead to 
degraded servo actuator performance and subsequent loss of control 
of the helicopter, do the following:
    (a) For a servo actuator with 1,500 or less hours time since new 
(TSN) or time since overhaul (TSO), determine the leakage rate on or 
before reaching 1,500 hours TSN or TSO. This 1,500 hour TSN or TSO 
inspection revises the airworthiness limitations section of the 
applicable maintenance manual.
    (b) For a servo actuator with 2,250 or less hours TSN or TSO, 
but more than 1,500 hours TSN or TSO, determine the leakage rate on 
or before reaching 2,250 hours TSN or TSO.
    (c) If the leakage rate in any servo actuator exceeds 700 cc per 
minute when performing the leakage rate inspection specified in 
paragraph (a) or (b) of this AD, then:
    (1) Replace that servo actuator piston, HR Textron or Woodward 
HRT P/N 41004321 or P/N RW41004321, with a servo actuator piston, P/
N 41012001 or P/N 41012001-001, and re-identify the servo actuator 
on the servo actuator data plate as Sikorsky P/N ``76650-09805-111'' 
and Woodward HRT P/N ``3006760-111'' using a metal stamp method; or
    (2) Replace the servo actuator with an airworthy servo actuator, 
Sikorsky P/N 76650-09805-111, Woodward HRT P/N 3006760-111.
    (d) On or before 3,000 hours TSN or TSO, whichever occurs first, 
replace each servo actuator piston and re-identify the servo 
actuator as specified in paragraph (c)(1) of this AD or replace each 
servo actuator as specified in paragraph (c)(2) of this AD.
    (e) Modifying and re-identifying each servo actuator as 
specified in paragraph (c)(1) of this AD or replacing each servo 
actuator as specified in paragraph (c)(2) of this AD is terminating 
action for the requirements of this AD for the modified and re-
identified or replaced servo actuator.
    (f) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Contact the Manager, Boston Aircraft Certification Office, FAA, 
ATTN: Terry Fahr, Aviation Safety Engineer, 12 New England Executive 
Park, Burlington, MA 01803, telephone (781) 238-7155, fax (781) 238-
7170, for information about previously approved alternative methods 
of compliance.
    (g) The Joint Aircraft System/Component (JASC) Code is 6730: 
Rotorcraft Servo System.
    (h) This amendment becomes effective on June 17, 2010.

    Issued in Fort Worth, Texas, on April 27, 2010.
Mark R. Schilling,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 2010-10588 Filed 5-12-10; 8:45 am]
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