Airworthiness Directives; Sikorsky Aircraft Corporation Model S-76A, B, and C Helicopters, 6835-6839 [E9-1688]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 74, Number 27 (Wednesday, February 11, 2009)]
[Proposed Rules]
[Pages 6835-6839]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-1688]


========================================================================
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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Federal Register / Vol. 74, No. 27 / Wednesday, February 11, 2009 / 
Proposed Rules

[[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 https://
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 https://
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 https://
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 https://
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