Document ID: FAA-2006-24587-0015
Agency: faa
Document Type: Rule
Title: Airworthiness Directives: Sikorsky Aircraft Corporation Model S-76A, B, and C Helicopters
Posted Date: 2009-02-11T05:00Z

[Federal Register: February 11, 2009 (Volume 74, Number 27)]
[Proposed Rules]
[Page 6835-6839]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr11fe09-9]

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Proposed Rules
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains notices to the public of
the proposed issuance of rules and regulations. The purpose of these
notices is to give interested persons an opportunity to participate in
the rule making prior to the adoption of the final rules.

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[[Page 6835]]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2006-24587; Directorate Identifier 2006-SW-05-AD]
RIN 2120-AA64

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

AGENCY: Federal Aviation Administration, DOT.

ACTION: Supplemental notice of proposed rulemaking; reopening of
comment period.

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

SUMMARY: This document revises an earlier proposed airworthiness
directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-
76A, B, and C helicopters. That AD proposed to require inspecting each
installed HR Textron main rotor servo actuator (servo actuator) for a
high rate of leakage and for contaminated hydraulic fluid and reducing
the time-in-service (TIS) interval for overhauling each servo actuator.
That proposal was prompted by a National Transportation Safety Board
(NTSB) Safety Recommendation issued in response to an accident
involving a Model S-76 helicopter. In the NTSB Recommendation, the
performance of an HR Textron servo actuator was questioned as a result
of piston head seal leakage and piston head plasma spray flaking. Since
the issuance of the initial proposal, and based on further information
obtained from the accident investigation, the comments to the proposal,
and other test and service history data since we issued the initial
proposal, we continue to believe that servo actuator pistons may
experience piston head seal leakage and plasma spray flaking, but have
determined that the full scope of the initial proposal is unnecessary.
We believe that the piston head seal leakage and plasma spray flaking
can be addressed by leakage rate inspections and replacement of the
current servo actuator pistons with an improved design not as
susceptible to plasma spray flaking. Therefore, we are revising the
proposed rule by removing the requirement to inspect 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. We are proposing
to add a 2,250 hours TIS hydraulic fluid leakage inspection and to add
a requirement to either install a new design servo actuator or replace
the servo actuator pistons when there is excessive leakage or upon
reaching a certain time interval. These actions 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: Comments must be received on or before April 13, 2009.

ADDRESSES: Use one of the following addresses to submit comments on
this proposed AD:
     Federal eRulemaking Portal: Go to http://
www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue, SE., Washington, DC 20590.
     Hand Delivery: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays.
    You may get the service information identified in this proposed AD
from Sikorsky Aircraft Corporation, Attn: Manager, Commercial Technical
Support, 6900 Main Street, Stratford, Connecticut, phone (203) 383-
4866, email address tsslibrary@sikorsky.com, or at http://
www.sikorsky.com.

FOR FURTHER INFORMATION CONTACT: Terry Fahr, Aviation Safety Engineer,
Boston Aircraft Certification Office, 12 New England Executive Park,
Burlington, MA 01803, telephone (781) 238-7155, fax (781) 238-7170.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to submit any written data, views, or arguments
regarding this proposed AD. Send your comments to the address listed
under the caption ADDRESSES. Include the docket number ``FAA-2006-
24587, Directorate Identifier 2006-SW-05-AD'' at the beginning of your
comments. We specifically invite comments on the overall regulatory,
economic, environmental, and energy aspects of the proposed AD. We will
consider all comments received by the closing date and may amend the
proposed AD in light of those comments.
    We will post all comments we receive, without change, to http://
www.regulations.gov, including any personal information you provide. We
will also post a report summarizing each substantive verbal contact
with FAA personnel concerning this proposed rulemaking. Using the
search function of our docket Web site, you can find and read the
comments to any of our dockets, including the name of the individual
who sent or signed the comment. You may review the DOT's complete
Privacy Act Statement in the Federal Register published on April 11,
2000 (65 FR 19477-78).

Examining the Docket

    You may examine the AD docket, which contains the proposed AD, any
comments, and other information, on the Internet at http://
www.regulations.gov or in person at the Docket Operations Office
between 9 a.m. and 5 p.m., Monday through Friday, except Federal
holidays. The street address for the Docket Operations office
(telephone (800) 647-5527) is in the ADDRESSES section. Comments will
be available in the AD docket shortly after receipt.

Discussion

    A proposal to amend 14 CFR part 39 to add an AD for Sikorsky Model
S-76A, B, and C helicopters with HR Textron servo actuators, part
number (P/N) 76650-09805, installed, was published in the Federal
Register on May 2, 2006 (71 FR 25783). That notice of proposed
rulemaking (NPRM) incorrectly referenced the ``HR Textron servo
actuator, P/N 76650-09805.'' It should have stated ``servo actuator,
Sikorsky P/N 76650-09805 (HR Textron P/N 3006760).'' That NPRM proposed
to

[[Page 6836]]

require, within 25 hours TIS, and thereafter at intervals not to exceed
600 hours TIS, determining the leakage rate for each of the three
installed servo actuators by installing a test line in each servo
actuator return port and turning on the hydraulic power. If the leakage
rate exceeded 700 cc per minute in any servo actuator, we proposed to
require replacing that servo actuator with an airworthy servo actuator
before further flight. That proposed AD would have also required
inspecting the hydraulic fluid for contamination using a patch test kit
or an independent laboratory analysis method. If the inspection
indicated that the hydraulic fluid was contaminated, the proposed AD
would have required flushing and refilling the hydraulic system with
uncontaminated hydraulic fluid before further flight. The proposed AD
also would have required reducing the TIS interval for overhauling an
affected servo actuator from 3,000 to 2,000 hours TIS.
    Since issuing that NPRM, we have received comments from 10
commenters, including two separate comments from the manufacturer, and
a comment from the NTSB. We have reviewed the comments on that proposed
rule and further analyses and test data.
    Seven commenters recommended that the NPRM be withdrawn. Another
commenter recommended that no AD be published ``until the FAA is
absolutely certain that existing manufacturer's maintenance criteria
were performed by experienced technicians.''
    One of these commenters, Air Logistics, states several reasons why
the NPRM should be withdrawn. First, they cite their 30 years of
operational experience with Sikorsky helicopters, during which they had
not experienced any servo failures. Second, they state that the results
of Sikorsky testing indicates that servo actuators with leakage rates
as high as 3000 cc per minute in one stage had the capacity to perform
the entire mission spectrum. Third, they have conducted their own
internal leak tests and hydraulic oil analyses and no defects or
contaminations were found. Fourth, they state there is ``no evidence''
presented by the NTSB or FAA to justify the NPRM. Finally, they state
that the 1,000 hour TIS reduction would impose thousands of dollars of
unnecessary expense without improving safety.
    Another commenter, Sikorsky Aircraft Corporation, states that the
NPRM should be withdrawn for several reasons. First, they state that
the scope of the NPRM is without authority because there is no unsafe
condition and the NPRM is based on an NTSB recommendation founded upon
``preliminary speculation'' regarding the root cause of an aircraft
mishap that has been shown by testing and analysis to be without merit.
Second, they state that they have 28 years and 9 million servo actuator
flight hours, operational testing, materials analysis, and assessments
of servo actuator operation within the fleet with no related
operational problems. Third, they state that the existing maintenance
program is adequate to assure safe, airworthy operation of the
hydraulic system and its associated hardware, ``including the main
rotor servo actuator, within the current defined overhaul intervals
based on operator data.'' ``This servo design has performed for over 25
years with no service anomalies.'' Fourth, they cite ``extensive
laboratory testing'' conducted by them demonstrating that ``normal
servo control is maintained throughout the certified flight envelope,
even with leakage and wear particle conditions up to three times the
[Sikorsky S76] Maintenance Manual limits'', and state that the ``servo
actuator is airworthy for the entire certificated flight envelope even
with significant fluid contamination and internal leakage, while
operating on one stage only.'' Fifth, they state that implementing the
AD would create an unnecessary maintenance burden on the operators and
increase fleet operating costs while providing no benefit.
Additionally, the commenter provided several additional ``Specific
Comments''. These specific comments further argue the contention that
(1) performance of the servo is compromised by internal leakage and
plasma spray flaking is incorrect; (2) servo internal leakage and
hydraulic fluid contamination from flaking spray could result in loss
of control of the aircraft is incorrect; (3) more frequent leakage
tests are required to maintain servo airworthiness is unfounded; (4)
more frequent hydraulic fluid cleanliness inspections are unwarranted;
and (5) reducing the servo overhaul interval is unnecessary.
    Another commenter, Carl Violette, states that the NPRM should be
withdrawn for several reasons. First, he cites his experience of 25
years and 60,000 flight hours of maintaining accident-free operations
of the Model ``S-76 variants.'' Second, he states that overhauling all
three Model S-76 servo actuators 1,000 hours TIS early when the leakage
rates are so low is ``ludicrous.'' Third, he states that the 600 hour
TIS inspection interval ``doesn't make sense'' considering the existing
100 hour TIS inspection. Fourth, he states that performing
contamination inspections on the aircraft is ``pointless'' since the
fluid is usually supplied by the hydraulic mule, which has a finer
filter than the aircraft one, and therefore one would only find
filtered hydraulic fluid in the aircraft. Fifth, he states that the
NPRM will increase helicopter operating costs from $15 per hour to
$22.50 per hour, and will cost their company an additional $9,000 per
year without any failed servo actuators. Sixth, he states that the
servo actuator ``jump'' check performed by the pilot each time the
aircraft is started is a ``better check'' and would inform the pilots
if there were any issues with the servo actuators. Seventh, he states
that there is ``no way'' that the servo actuator could extend beyond
the pilot's inputs without a mechanical breakage somewhere, and that
minuscule flakes won't prevent the 3,000 PSI fluid from going where it
wants to go. Eighth, Mr. Violette commented that he found it
``cavalier'' that so little research was done on this proposal in light
of the seriousness of the incident. He questioned the proposed
frequency of the leakage checks, and why this leakage prompts us to
lower the overhaul interval. He further stated that if contamination
checks are required, then more guidance is required. He stated, ``If a
patch test is done, what is the accept/reject criteria? Can I send
fluid to a lab instead? What are their accept/reject criteria? When
should I replace a servo?'' He stated that he doesn't understand how
the proposed AD makes the aircraft safer.
    Another commenter, Helicopter Support, Inc., states that the NPRM
should be withdrawn for several reasons. First, in 20 years of overhaul
and repair experience, they found flaking of the Model S-76 servo
actuator piston plasma spray in only extremely rare circumstances.
Second, Sikorsky testing showed ``no connection between internal
leakage of the main rotor servo actuator and subsequent loss of control
of the helicopter.'' Third, a reduction in the overhaul interval from
3,000 to 2,000 hours TIS would impose an unnecessary financial burden,
and would increase maintenance costs and negatively impact flight
availability. Fourth, the maintenance procedures called out in Chapters
5 & 29 of the Sikorsky S-76 Maintenance Manual ``are sufficient to
identify leakage and contamination'' in the servo actuator system.
Fifth, performing the leakage rate check is subjective and can lead to
costly false removals of the servo actuator. Sixth, the 600 hours TIS
patch test can be addressed by the 12 month

[[Page 6837]]

patch test requirement in the Sikorsky S-76 Maintenance Manual.
    Another commenter, Aero Med Spectrum Health, cited their 14 or more
years of operating both Model S-76A and Model S-76B helicopters without
any operational problems or internal failures of the servo actuators,
or anomalies reported by the crew, as evidence that the AD is
unnecessary.
    Another commenter, HR Textron, stated that the AD is unnecessary
because the NPRM is based on ``speculation of an NTSB investigator''
with respect to a Model S-76 helicopter accident that has been shown to
be ``without substance or merit,'' and extensive testing by HR Textron
and Sikorsky have demonstrated that ``internal leakage and/or plasma
spray flaking do not create an unsafe condition.'' Further, information
on the flight data recorder of the accident helicopter ``do not support
the theory that a mechanical malfunction of the servo caused the
mishap.''
    Another commenter, Jay Deering, feels that the AD is
``unnecessary'' and will cause undue hardship for the operator.
    Another commenter, Steve Strollo, states that the ``AD should not
be published until the FAA is absolutely certain that existing
manufacturer's maintenance criteria were performed by experienced
technicians.'' He further states that in his 26 years as an A&P
mechanic, he has seen only one serious servo actuator failure due to
``tissue thin wall thickness along the entire length of the tube'' and
the pilots were unaware of the malfunction. He has never experienced
excessive contamination of a hydraulic system, or a failed patch test.
Also, he believes that degradation of the accident servo ``did not
occur overnight'' and that if the 300 hours TIS inspection is performed
correctly, damage to the servo actuator can be easily spotted.
    Regarding Mr. Strollo's comment referencing the 300 hours TIS
inspection, that is an inspection pertaining to ``noticeable wear of
the chrome plating on the visible surface'' of the servo actuator
piston that is not required by an AD and is not relevant to this
proposal.
    Two commenters, Copterline Oy (Copterline) and the NTSB, supported
the NPRM.
    One commenter, Copterline, was the operator of the Sikorsky Model
S-76 helicopter that crashed shortly after taking off in Estonia in
2005 and prompted the NTSB safety recommendation. Copterline states
that the NPRM should be adopted in its entirety and expanded to include
other servo actuators in which there is ``a possibility for
manufacturing process error'' which can cause plasma coating to
delaminate and block the servo actuator return ports, leading to loss
of control of the helicopter. They state that ``the reason why the
Plasma coating flakes off remains unaddressed.'' They state that the
NPRM should be expanded to include additional testing--for example, x-
ray, ultrasonic, or other appropriate testing--to confirm that the
plasma coating has adhered to the servo actuator pistons, which will
further reduce risk. This commenter states that the NPRM should be more
comprehensive. Copterline also states that the NPRM should propose a
reduction in the servo actuator piston life limit until the plasma
spray flaking problem has been resolved. Copterline cites NTSB
laboratory findings and states that it agrees with Sikorsky that when
one of the two return flow ports is blocked, safe operations can be
conducted. However, if both return ports of the control valve have been
blocked, the bypass function is not available and the blocked side will
jam the other stage. They state that the ``laboratory testing results
justify the NTSB's concern.'' Copterline also states that the proposed
AD actions and even the additional requirements that they propose
``would not adversely affect the S-76 operators and, in practise, [sic]
would not materially increase operating costs of the S-76 fleet.'' This
commenter also states that continued accidents would be reflected in
increased insurance premiums that would more than offset any short term
savings associated with not taking appropriate action.
    Additionally, this commenter attached a copy of its ``Detailed
Comments to Sikorsky's Comments on FAA and AOL'' Web sites. These
comments are consistent with those made to the NPRM.
    Another commenter, the NTSB, also supports the NPRM, and states
that ``results of the Safety Board and Sikorsky tests demonstrate the
need for issuance of a final rule consistent with the proposed AD as
soon as possible.''
    Based on the comments summarized previously and our re-evaluation
of the published proposal, we agree with various portions of the
comments proposing withdrawal of the NPRM and portions of those
supporting the NPRM. With respect to those comments citing operational
experience, lack of supportive evidence by the FAA or NTSB, testing
results, adequacy of existing maintenance programs, imposition of
costly procedures without an increase in safety, and inappropriateness
of the proposed procedures as evidence supporting withdrawal, we have
determined that portions of the initial proposal are unnecessary to
correct the unsafe condition, although there is still uncertainty about
the root cause of the accident. Based on our reevaluation, we continue
to believe that servo actuator pistons may experience piston head seal
leakage and plasma spray flaking, but this does not justify the full
scope of the initial proposal. We believe that the piston head seal
leakage and plasma spray flaking can be addressed adequately by leakage
rate inspections and replacement of the current servo actuator pistons
with an improved design not as susceptible to plasma spray flaking. The
reduction in the overhaul interval from 3,000 to 2,000 hours TIS is not
necessary if the leakage rate inspection is performed, and the leakage
rate inspection is a better way of determining servo actuator condition
than the hydraulic fluid patch test. Therefore, in order to prevent
degraded servo actuator performance as a result of piston head seal
leaking and plasma spray flaking, which may result in subsequent loss
of control of the helicopter, we are revising the proposed rule by
removing the requirement to inspect the hydraulic fluid for
contamination using a patch test kit or an independent laboratory
analysis method; 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. We are proposing to add a
2,250 hours TIS hydraulic fluid leakage inspection to the currently
required 1,500 hours TIS hydraulic fluid leakage inspection; and
proposing to add a requirement to either install a new design servo
actuator, Sikorsky part number (P/N) 76650-09805-111 (HR Textron P/N
3006760-111), or replace the servo actuator pistons, P/N 41004321 with
P/N 41012001 or P/N 41012001-001, in servo actuators, Sikorsky P/N
76650-09805-109 and -110 (HR Textron P/N 3006760-109 and -110), either
because of excessive leakage at the 1,500 or 2,250 hours TIS leakage
inspection, or upon reaching the 3,000 hours TSN or TSO maintenance
interval.
    Regarding the comments in opposition to our proposal because of the
cost, we agree that the initial proposal and these revised proposals
would increase the operator's maintenance costs. While the total
estimated cost amount of the impact contained in the economic
evaluation in

[[Page 6838]]

this SNPRM is larger than that contained in the previous NPRM, those
cost amounts are only estimates based on different assumptions that are
difficult to project. We believe that the reduction in the proposed
requirements in this SNPRM will result in an overall lesser adverse
economic impact on operators. Economic consideration is not and cannot
be the paramount consideration in AD actions. The overall safety
benefits must be considered. ADs are issued to correct unsafe
conditions, and to return the type certificate to the approved minimum
level of safety.
    Since we believe that the proposed leakage rate check and
incorporation of the new servo actuator piston design are sufficient to
address degraded servo actuator performance as a result of piston head
seal leakage and plasma spray flaking, Copterline's proposed additional
x-ray, ultrasonic, or other appropriate tests to verify adhesion of the
piston plasma coating are not necessary, and would increase the
operators' costs without an increased level of safety. Furthermore, we
have determined, as previously mentioned, that we need to address
degraded servo actuator performance due to internal leakage and piston
head plasma spray flaking, which could potentially lead to loss of
control of the helicopter. Therefore, we are revising the initial
proposal to require only the leakage rate inspections and replacement
of the servo actuators, Sikorsky P/N 76650-09805-109 and -110, with
servo actuators, Sikorsky P/N 76650-09805-111, or replacement of servo
actuator pistons, P/N 41004321, with P/N 41012001 or P/N 41012001-001,
in Sikorsky servo actuators, P/N 76650-09805-109 and -110.
    Copterline also states that inconclusive investigations into
previous ``unsolved accidents'' involving Sikorsky Model S-70, S-76,
and H-53 helicopters should be re-examined to determine if there is any
relationship between those accidents and the more recent accident
involving the Copterline helicopter that prompted issuing the NPRM.
    We do not agree that additional review of previous accidents
involving Sikorsky helicopter models is necessary. Investigations of
previous Model S-76 helicopter accidents indicated no evidence of
involvement of the servo actuators, therefore, we believe there is no
relationship to the Copterline accident. Moreover, these servo
actuators on those other Sikorsky model helicopters are significantly
different in design, not susceptible to the same plasma flaking and
seal leakage problems as the Model S-76 servo actuator, and would not
provide useful information for evaluating the failure modes of the
Model S-76 servo actuator.
    Copterline expressed concern that the servo actuator does not meet
the part 29 certification requirements to be a ``fail-safe component'',
and that it was not designed for the situation in which both return
ports are blocked, which could cause the servo actuator to jam. As
previously noted, they cite the NTSB laboratory findings as evidence
that this dual blockage occurred, leading to the accident. Copterline
states that the manufacturer of the servo actuator or the helicopter
must demonstrate and prove that the servo actuator is a fail-safe
component and that the Model S-76 helicopter meets all the type
certification requirements.
    We disagree with Copterline's statement that the S-76 servo
actuator does not meet part 29 certification requirements. The design
of the affected Model S-76 helicopter servo actuator meets the fail-
safe design regulatory requirements that were in effect at the time of
initial certification of the Model S-76 helicopter. The inspection
requirements of this revised proposal will assure that the Model S-76
servo actuator remains airworthy.
    Copterline states that ``the FAA should require Sikorsky to make
all Servo testing reports available without delay.'' Copterline also
states that ``servo testing results and findings for cases where both
return flow ports are blocked should be released immediately, if they
exist.'' Also, Copterline states that the ``specially manufactured and
modified servo used in the Sikorsky testing'' did not demonstrate
conclusively what happened in the accident servo actuators. They
further state that the Sikorsky testing does not establish that a servo
actuator on the helicopter involved in the accident did not
malfunction.
    We agree with the comment that all testing results and findings
should be released and to our knowledge, all relevant and requested FAA
agency records have been made available. With respect to the comment
that Sikorsky did not demonstrate conclusively what happened in the
accident, the parties involved in the accident investigation have
conducted extensive investigations to determine the cause of the
accident. Although the Estonian authorities have released a final
report identifying a cause of the accident, these parties have not and
may not ever agree on the cause of the accident. As previously
mentioned, the FAA has determined, based on further information
obtained from the Copterline accident investigation and other test and
service history data since we issued the NPRM, that a need exists to
address degraded servo actuator performance due to internal leakage and
piston head plasma spray flaking. This is reflected in this proposal.
    Sikorsky states with respect to the accident, that the physical
evidence does not support the theory that a mechanical malfunction of
the servo caused the accident, and that it is physically impossible for
the Model S-76 helicopter to perform these maneuvers without being
influenced by an external force such as a waterspout. Copterline states
Sikorsky's comment is incorrect when it states that it is physically
impossible for the Model S-76 helicopter to perform the maneuvers
recorded on its own even if the servo actuator malfunctioned, and cites
the accident helicopter's flight data recorder (FDR) data as evidence
that the accident helicopter stalled at 130 knots, and this stall is
the external force that explains the maneuvers. They also state that if
there had been any weather related cause to the accident, that it could
have been read from the FDR data, and that there isn't any data to
support Sikorsky's theory of a waterspout.
    The weather data and laboratory test data are inconclusive. We have
determined that the Model S-76 servo actuator pistons may experience
piston head seal leakage and plasma spray flaking, and are proposing
the 1,500 and 2,250 hours TIS leakage inspections and servo actuator
replacement to address this unsafe condition.
    Finally, Sikorsky, in a second comment, states that the comments
submitted by the NTSB in response to the previously issued NPRM are
inaccurate or inconsistent with physical evidence or recorded test
data. Sikorsky states that the Sikorsky testing fully demonstrated that
all flight loads can be sustained in a triple ``failure'' condition,
and that a ``combined failure'' with high leakage rates (3 times the
in-service allowable leakage), 100 percent blockage of one of the two
C3 ports, and loads associated with high airspeeds (and more
significantly, the entire certified flight spectrum), will not
overpower the servo actuator. They further state that they have briefed
the NTSB and FAA on results of these tests and maintain that the
testing demonstrates that the servo actuator design is safe and robust.
    As stated previously, the final report on the accident
investigation has been released, and the parties involved in the
investigation have not and may never agree on the cause of the
accident. However, we have determined that there

[[Page 6839]]

is a need to require the servo actuator leakage rate inspections and
replacing each affected servo actuator with a servo actuator containing
a newly re-designed servo actuator piston to prevent degraded servo
actuator performance as a result of piston head seal leakage and plasma
spray flaking.
    Since this proposal changes the scope and the requirements of the
originally proposed rule, we have determined that it is necessary to
reopen the comment period to provide additional opportunity for public
comment.
    We estimate that this proposed AD would affect 300 helicopters (900
servo actuators) of U.S. registry. We also estimate that the leakage
rate inspection would take about 1 work hour per servo actuator at an
average labor rate of $80 per work hour, and the two leakage rate
inspections on 900 servo actuators would cost about $144,000. We
estimate that 6 servo actuators, Sikorsky P/N 76650-09805-109 or -110,
would 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 would be $345,840. We estimate that
the cost of replacing the pistons in the remaining 894 servo actuators
would cost $7,259,280, 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
proposal is $7,749,120.

Regulatory Findings

    We have determined that this proposed AD would not have federalism
implications under Executive Order 13132. Additionally, this proposed
AD would 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 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. 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 a draft economic evaluation of the estimated costs to
comply with this proposed AD. See the AD docket to examine the draft
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.

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.

Sec.  39.13  [Amended]

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

Sikorsky Aircraft Corporation: 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 part number (P/N)
76650-09805-109 or -110 (also marked as HR Textron 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-in-
service (TIS) since new (TSN) or TIS since overhaul (TSO), determine
the leakage rate on or before reaching 1,500 hours TSN or TSO.
    (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 P/N 41004321,
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 HR Textron 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, HR Textron 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.

    Issued in Fort Worth, Texas, on January 16, 2009.
Mark R. Schilling,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
16
 [FR Doc. E9-1688 Filed 2-10-09; 8:45 am]

BILLING CODE 4910-13-P