
[Federal Register Volume 76, Number 85 (Tuesday, May 3, 2011)]
[Rules and Regulations]
[Pages 24798-24802]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-10521]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2010-0821; Directorate Identifier 2010-NE-30-AD; 
Amendment 39-16657; AD 2011-08-07]
RIN 2120-AA64


Airworthiness Directives; Rolls-Royce plc (RR) RB211-Trent 875-
17, RB211-Trent 877-17, RB211-Trent 884-17, RB211-Trent 884B-17, RB211-
Trent 892-17, RB211-Trent 892B-17, and RB211-Trent 895-17 Turbofan 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are adopting a new airworthiness directive (AD) for the 
products listed above. This AD results from mandatory continuing 
airworthiness information (MCAI) issued by an aviation authority of 
another country to identify and correct an unsafe condition on an 
aviation product. The MCAI describes the unsafe condition as:

    In January 2009 a Trent 895 powered Boeing 777-200 aircraft 
experienced release of a low pressure (LP) compressor blade which 
failed due to fatigue cracking in the root section of the blade. The 
released blade (undercut root standard) had received a part life 
processing to apply a compression layer to the blade root (Service 
Bulletin SB 72-D672--Introduction of Laser Shock Peening (LSP)) and 
also a part life upgrade to the retention feature lubrication 
system. Investigation has revealed that the effectiveness of this 
upgraded blade root lubrication coating system may be reduced 
dependant on the extent of previous running with the earlier 
standard, leading to increased blade root stress levels. In the 
specific case of the released blade, a review of its in-service 
modification history has shown that it operated for a relatively 
high number of flight cycles prior to the compression layer 
processing and the new retention feature lubrication system. A 
review of the Engine Health Monitoring data has also identified it 
operated at high N1 speeds compared to the Trent 800 fleet average 
N1 speeds. The combination of these factors has resulted in 
increased fatigue life usage which is considered to have led to 
crack initiation and propagation prior to reaching the blades 
declared life limit. A review of all in-service undercut/LSP 
standard Trent 800 LP compressor blades has identified specific 
blades that carry a similar increased susceptibility to cracking.
    This AD is issued to mitigate the risk of possible multiple fan 
blades failure affecting those blades identified as described above 
which could lead to high energy non contained debris from the 
engine.

    We are issuing this AD to prevent LP compressor blades from failing 
due to blade root cracks, which could lead to uncontained engine 
failure and damage to the airplane.

DATES: This AD becomes effective June 7, 2011. The Director of the 
Federal Register approved the incorporation by reference of certain 
publications listed in this AD as of June 7, 2011.

ADDRESSES: The Docket Operations office is located at Docket Management 
Facility, U.S. Department of Transportation, 1200 New Jersey Avenue, 
SE., West Building Ground Floor, Room W12-140, Washington, DC 20590-
0001.

FOR FURTHER INFORMATION CONTACT: Alan Strom, Aerospace Engineer, Engine 
Certification Office, FAA, Engine & Propeller Directorate, 12 New 
England Executive Park, Burlington, MA 01803; e-mail: 
alan.strom@faa.gov; telephone (781) 238-7143; fax (781) 238-7199.

SUPPLEMENTARY INFORMATION: 

Discussion

    We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR 
part 39 to include an AD that would apply to the specified products. 
That NPRM was published in the Federal Register on January 14, 2011 (76 
FR 2605). That NPRM proposed to correct an unsafe condition for the 
specified products. The MCAI states that:

    In January 2009 a Trent 895 powered Boeing 777-200 aircraft 
experienced release of a low pressure (LP) compressor blade which 
failed due to fatigue cracking in the root section of the blade. The 
released blade (undercut root standard) had received a part life 
processing to apply a compression layer to the blade root (Service 
Bulletin SB 72-D672--Introduction of Laser Shock Peening (LSP)) and 
also a part life upgrade to the retention feature lubrication 
system. Investigation has revealed that the effectiveness of this 
upgraded blade root lubrication coating system may be reduced 
dependant on the extent of previous running with the earlier 
standard, leading to increased blade root stress levels. In the 
specific case of the released blade, a review of its in-service 
modification history has shown that it operated for a relatively 
high number of flight cycles prior to the compression layer 
processing and the new retention feature lubrication system. A 
review of the Engine Health Monitoring data has also identified it 
operated at high N1 speeds compared to the Trent 800 fleet average 
N1 speeds. The combination of these factors has resulted in 
increased fatigue life usage which is considered to have led to 
crack initiation and propagation prior to reaching the blades 
declared life limit. A review of all in-service undercut/LSP 
standard Trent 800 LP compressor blades has identified specific 
blades that carry a similar increased susceptibility to cracking.

[[Page 24799]]

    This AD is issued to mitigate the risk of possible multiple fan 
blades failure affecting those blades identified as described above 
which could lead to high energy non contained debris from the 
engine.

Comments

    We gave the public the opportunity to participate in developing 
this AD. We considered the comments received.

Request To Ensure Cyclic Requirements Are Equivalent to Calendar-Based 
Requirements

    Two commenters, the Boeing Company and American Airlines, request 
that we ensure that the cyclic requirements in the AD are equivalent to 
the calendar-based requirements in the MCAI and Alert Service Bulletin 
(ASB) No. RB.211-72-AG244, Revision 1, dated January 26, 2010. American 
Airlines' engine serial number (S/N) 51137 is identified as having an 
allowable inspection threshold of 1,680 cycles from the effective date 
of the proposed AD. Based on American Airlines' cyclic usage, the FAA 
AD would allow the blades to operate until March 1, 2014, while the RR 
ASB would only allow the blades to operate until January 1, 2013. The 
proposed AD appears to be less conservative for the blades in engine S/
N 51137.
    We agree. We moved engine S/N 51137 from being listed with the 
1,680 cycles threshold, to being listed with a 1,027 cycles threshold 
in row 3C of Table 1 of the AD.

Recommendation To Retain Compliance Calendar Date Format

    One commenter, RR, recommends that the FAA retain the calendar date 
format as specified in the referenced ASB No. RB.211-72-AG244, Revision 
1, dated January 26, 2010 for compliance, rather than converting to 
cycles for the inspection threshold for the sub-population of fan sets. 
At the request of the National Transportation Safety Board, RR analyzed 
the modification and installation data for each fan set using both 
hours and cycles. For some operators, the highest risk value was based 
on hours and for others it was cycles. Whichever gave the highest risk 
value, together with the average utilization, was then used to 
determine the dates at which the blades need to have their initial 
inspection. Therefore, converting to cycles may not be correct for some 
operators. Rolls-Royce states that it will monitor N1 speed usage. A 
higher N1 speed usage could result in the risk values being affected 
and result in RR ASB No. RB.211-72-AG244, being revised and re-issued. 
Any change to that ASB would necessitate changing the FAA AD. By 
retaining the date format and the FAA AD referencing that SB then any 
future changes to the dates in the Appendices of the SB will not affect 
the AD. The SB is clear and simple, making it easy for the operators to 
monitor their affected fan blades. Monitoring a number of fan blades 
using cycles would make the monitoring more difficult for the operator.
    We do not agree. We determined the cycles listed in Table 1 of the 
AD based on projected operator usage, from the calendar dates in the RR 
ASB. The SB dates were developed based on the logic given in the first 
justification paragraph above. The cyclic requirements in the AD are 
inherently consistent with each operator's risk values. We did not 
change the AD.

Request for Clarification of Incorporation by Reference Requirements

    One commenter, Delta Airlines, states that the proposed AD requires 
use of Appendix 1 of RR ASB No. RB.211-72-AG244 to determine whether 
blades should be rejected after inspection. Appendix 1 only applies to 
blades that have been removed from the engine. Delta Airlines requests 
that the AD be changed so it is clear that the blades can be inspected 
either in or out of the engine, with appropriate rejection criteria for 
each method.
    We agree. Our intent is not to restrict the inspections to blades 
removed from the engine. We added Appendix 2 to the incorporation by 
reference, to include blades not removed.
    Delta Airlines also requests that we change the incorporation-by-
reference requirement, to state that when re-applying dry film 
lubricant (DFL) to the fan blades after inspection, either Aircraft 
Maintenance Manual (AMM) task 72-31-11-400-801-R00, or RR SB No. 
RB.211-72-D347, may be used. The commenter states that the latest 
information from RR SB No. RB.211-72-D347 is already in AMM task 72-31-
11-400-801-R00.
    We partially agree. We agree with specifying in the AD, that blades 
that pass inspection need to have DFL applied before installing the 
blades. We do not agree that the AMM or RR No. RB.211-72-D347 need to 
be incorporated by reference in this AD, as this equates to standard 
maintenance. Under paragraph (e)(3), we added a paragraph that states, 
for blades that pass inspection, re-apply dry film lubricant, and 
install all blades in their original position.

Request for Previous Credit

    Delta Airlines requests that we give previous credit for previous 
accomplishments of inspections using the original issue of RR ASB No. 
RB.211-72-AG244, before the effective date of the AD.
    We agree. We changed the AD to add previous credit for that ASB.

Request To Eliminate Reporting Requirements

    Delta Airlines requests that we eliminate the reporting 
requirements from the AD, which were required by default since the 
proposed AD required using all of paragraph 3 of RR ASB No. RB.211-72-
AG244, Revision 1, dated January 26, 2010, and all of Appendix 1, of 
that AD. The commenter states that these are administrative tasks that 
do not need to be part of the AD. Each operator is required to document 
maintenance and AD compliance per the applicable regulations, and each 
has their own approved processes for doing so.
    We agree and eliminated the reporting requirements by specifying 
only the paragraphs needed to perform the inspections in the AD.

Concern That AD Compliance May Be Misinterpreted

    Delta Airlines requests that we revise the AD to state that after 
the effective date of this AD, blade serial numbers that are listed in 
RR No. RB.211-72-AG244, which have reached or are within 100 cycles of 
the initial inspection thresholds of Table 1 of the proposed AD, may 
only be installed as replacement blades in other engines if they have 
been successfully inspected per paragraph (e)(3) of this AD before 
installation. However, they may be removed and reinstalled in the same 
engine without paragraph (e)(3) inspections provided they do not exceed 
the initial and repetitive inspection intervals of paragraphs (e)(1) 
and (e)(2).
    Also, Delta Airlines requests that we revise the AD to state that 
blades that have been ultrasonically inspected prior to the AD 
effective date, but which have not yet reached Table 1 thresholds, 
should be considered not yet ``initially inspected,'' and thus not 
subject to the repetitive inspection requirements of paragraph (e)(2) 
until they reach the Table 1 inspection thresholds. On the same 
subject, American Airlines requests that the AD include a note similar 
to the SB to the same effect as the above recommendation. Delta 
Airlines and American Airlines are concerned that the AD might be 
interpreted that serviceable spare blades

[[Page 24800]]

in stock (or blades being swapped from one engine to another) with 
serial numbers listed in RR ASB No. RB.211-72-AG244, must have 
ultrasonic inspection (UI) accomplished before being installed even if 
they do not require initial inspection for thousands of cycles into the 
future. Delta Airlines also states that the existing UI requirements in 
the AD may lead to confusion as to whether the paragraph (e)(2) 
repetitive requirements apply to blades that have been inspected for 
other reasons prior to the Table 1 threshold.
    We agree with the comments that the AD could be more clear as to 
when the inspections must start, and whether UI for other reasons prior 
to the thresholds in Table 1 would trigger the repetitive inspection 
requirements of paragraph (e)(2). We do not agree with the wording of 
the proposed change because it is simpler to define the phrase, 
``affected blade.'' The requirement of paragraph (e)(5) of the proposed 
AD, does not require inspections more often than every 100 cycles for 
any affected blade, since proposed AD paragraph (e)(5) refers to 
paragraph (e)(2) (repetitive UIs required by this AD). We added a 
definition to the AD compliance to state for the purpose of this AD, an 
affected blade is a blade listed in Table 1 of this AD that has 
accumulated cycles within 100 cycles, of the initial inspection 
thresholds in Table 1 of this AD.

Engine Serial Numbers Are for Reference Only

    Delta Airlines and American Airlines request that we add a 
statement to the AD, stating that the engine serial numbers in Table 1 
of the proposed AD are for reference only, and that the AD requirements 
apply to the blade serial numbers, not the engine serial numbers. The 
Table 1 listing of engine serial numbers could imply the engine 
requires initial and repetitive inspections even if blades were 
replaced with non-affected blades.
    We agree. We intend for the AD to apply to the specific fan blade 
serial numbers listed in RR ASB No. RB.211-72-AG244, Revision 1, dated 
January 26, 2010. The engine serial numbers are listed for convenience 
only. We changed Table 1 to state that engine serial numbers are 
provided for reference only.

Request To Correct Table 1

    American Airlines states that engine serial number 51280 appears to 
be in the wrong row of Table 1 of the proposed AD. They request that we 
correct the Table by moving the serial number from the top of row 3E to 
the bottom of row 3D, in that table.
    We partially agree. We reviewed the proposed AD, as published in 
the Federal Register, and found it to be correct. We reviewed the 
proposed AD version in the FAA Regulatory Library (RGL), and found that 
Table 1 had the error you found. We contacted the staff that oversees 
the RGL, and they corrected Table 1.

Request That All Thresholds Be Given the Same Index

    Delta Airlines requests that all thresholds in Table 1 of the 
proposed AD be the same for a given index. Delta Airlines noticed that 
most fan blade serial numbers being used in their engines were singled 
out with a lower threshold than the rest of the blades listed in 
corresponding appendices of the SB.
    We do not agree. We changed the inspection requirements in the 
proposed AD from calendar-based requirements to cycle-based 
requirements. Because the intent of the AD is to have the same level of 
safety as the EASA AD, the cyclic usage of each operator was taken into 
account when converting from calendar to cyclic thresholds. The intent 
is for the number of cycles quoted to equate to the calendar times 
shown in the EASA AD. Since operators fly on different routes and have 
different procedures, the number of cycles accumulated in a given 
calendar period will vary as a consequence. We did not change the AD.

Request To Verify Row Identifiers in Table 1

    American Airlines requests that the FAA verify that the row 
identifiers in Table 1 of the AD, correspond to the Appendix 
identifiers in RR ASB No. RB.211-72-AG244, Revision 1, dated January 
26, 2010, to ensure that operators properly understand the AD 
requirements.
    We partially agree. We agree with ensuring that Table 1 is clearly 
understood, to avoid operators from having problems complying with the 
AD. We do not agree with changing the AD, because Table 1 of the AD 
provides sufficient clarity in defining the compliance time criteria 
and what the appropriate sections of the ASB are, to be used. The row 
identifiers in Table 1 of the AD do correspond to the Appendix 
identifiers in RR ASB No. RB.211-72-AG244, Revision 1, dated January 
26, 2010. We did not change the AD.

Conclusion

    We reviewed the available data, including the comments received, 
and determined that air safety and the public interest require adopting 
the AD with the changes described previously. We determined that these 
changes will not increase the economic burden on any operator or 
increase the scope of the AD.

Costs of Compliance

    Based on the service information, we estimate that this AD will 
affect about 20 engines installed on airplanes of U.S. registry. We 
also estimate that it will take about 18 work-hours per engine to 
perform the inspections in one year's time. The average labor rate is 
$85 per work-hour. We estimate that one LP compressor blade per year 
will need replacement, at a cost of about $82,000. Based on these 
figures, we estimate the annual cost of the AD on U.S. operators to be 
$112,600. Our cost estimate is exclusive of possible warranty coverage.

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.

Regulatory Findings

    We 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 this AD:
    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

[[Page 24801]]

    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 regulatory evaluation of the estimated costs to 
comply with this AD and placed it in the AD docket.

Examining the AD Docket

    You may examine the AD docket 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 AD docket contains this AD, the regulatory evaluation, 
any comments received, and other information. The street address for 
the Docket Operations office (phone (800) 647-5527) is provided in the 
ADDRESSES section. Comments will be available in the AD docket shortly 
after receipt.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA amends 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. The FAA amends Sec.  39.13 by adding the following new AD:

2011-08-07 Rolls-Royce plc: Amendment 39-16657. Docket No. FAA-2010-
0821; Directorate Identifier 2010-NE-30-AD.

Effective Date

    (a) This airworthiness directive (AD) becomes effective June 7, 
2011.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Rolls-Royce plc (RR) RB211-Trent 875-17, 
RB211-Trent 877-17, RB211-Trent 884-17, RB211-Trent 884B-17, RB211-
Trent 892-17, RB211-Trent 892B-17, and RB211-Trent 895-17 turbofan 
engines.

Reason

    (d) This AD results from mandatory continuing airworthiness 
information (MCAI) issued by an aviation authority of another 
country to identify and correct an unsafe condition on an aviation 
product. We are issuing this AD to prevent low-pressure (LP) 
compressor blades from failing due to blade root cracks, which could 
lead to uncontained engine failure and damage to the airplane.

Actions and Compliance

    (e) Unless already done, do the following actions.
    (1) Using the corresponding compliance threshold in Table 1 of 
this AD, perform an initial ultrasonic inspection (UI) of the 
affected LP compressor blades identified by serial number (S/N) in 
Appendices 3A through 3F of RR Alert Service Bulletin (ASB) No. 
RB.211-72-AG244, Revision 1, dated January 26, 2010.

                 Table 1--Initial Inspection Thresholds
------------------------------------------------------------------------
Appendix Number of RR ASB No.
 RB.211-72-AG244, Revision 1,    Initial Inspection Threshold  (Engine
 that identifies affected LP   Serial Nos. (ESN) are for reference only)
   compressor blades by S/N
------------------------------------------------------------------------
3A...........................  120 flight cycles after the effective
                                date of this AD.
3B...........................  Blades shown in RR ASB No. RB.211-72-
                                AG244, Revision 1 as fitted to ESN
                                51039--802 flight cycles after the
                                effective date of this AD.
                               ESNs 51146, 51177, 51145, and 51149--380
                                flight cycles after the effective date
                                of this AD.
3C...........................  Blades shown in RR ASB No. RB.211-72-
                                AG244, Revision 1 as fitted to ESN 51001
                                and blade S/N RGG16694--1,680 flight
                                cycles after the effective date of this
                                AD.
                               ESN 51145, 51149, 51150 and 51204--796
                                flight cycles after the effective date
                                of this AD.
                               ESN 51160--1,160 flight cycles after the
                                effective date of this AD.
                               ESN 51137--1,027 flight cycles after the
                                effective date of this AD.
3D...........................  Blades shown in RR ASB No. ASB RB.211-72-
                                AG244, Revision 1 as fitted to ESN 51193
                                and blade S/N RGG20216--1,212 flight
                                cycles after the effective date of this
                                AD.
                               ESN 51200--1,237 flight cycles after the
                                effective date of this AD.
                               ESN 51280--1,551 flight cycles after the
                                effective date of this AD.
3E...........................  Blades shown in RR ASB No. RB.211-72-
                                AG244, Revision 1 as fitted to ESN
                                51004, ``na'' and blade S/Ns RGG12590,
                                RGG14081, and RGG15419--3,433 flight
                                cycles after the effective date of this
                                AD.
                               ESN 51156--1,627 flight cycles after the
                                effective date of this AD.
3F...........................  Blades shown in RR ASB No. RB.211-72-
                                AG244, Revision 1 as fitted to ESN
                                51175, 51194, 51201, 51205, and 51228--
                                2,042 flight cycles after the effective
                                date of this AD.
                               ESN 51264--4,309 flight cycles after the
                                effective date of this AD.
                               ESN 51443--2,636 flight cycles after the
                                effective date of this AD.
                               Blade S/N RGG15698--2,638 flight cycles
                                after the effective date of this AD.
------------------------------------------------------------------------

    (2) Thereafter, perform repetitive UIs of the affected LP 
compressor blades within every 100 flight cycles.
    (3) Use paragraphs 3.A.(1) through 3.A.(2) of Accomplishment 
Instructions of RR ASB No. RB.211-72-AG244, Revision 1, dated 
January 26, 2010, paragraphs 1 through 3.B. of Appendix 1, and 
paragraphs 1 through 3.C. of Appendix 2, of that ASB, to perform the 
UIs.
    (4) Remove blades from service before further flight that fail 
the inspection criteria in Appendix 1 of RR ASB No. RB.211-72-AG244, 
Revision 1, dated January 26, 2010.
    (5) For blades that pass inspection, re-apply dry film 
lubricant, and install all blades in their original position.
    (6) After the effective date of this AD, do not install any 
affected LP compressor blade unless it has passed the initial and 
repetitive UIs required by this AD.

Previous Credit

    (f) An initial UI performed before the effective date of this AD 
using RR ASB No. RB.211-72-AG244, dated August 7, 2009, satisfies 
the initial UI requirements of this AD.

FAA AD Differences

    (g) This AD differs from European Aviation Safety Agency (EASA) 
AD 2010-0097, dated May 26, 2010. The EASA AD uses calendar

[[Page 24802]]

dates for initial inspection thresholds. This AD uses flight cycles.

Alternative Methods of Compliance

    (h) The Manager, Engine Certification Office, FAA, has the 
authority to approve AMOCs for this AD, if requested using the 
procedures found in 14 CFR 39.19.

Related Information

    (i) Refer to EASA AD 2010-0097, dated May 26, 2010, for related 
information.
    (j) Contact Alan Strom, Aerospace Engineer, Engine Certification 
Office, FAA, Engine & Propeller Directorate, 12 New England 
Executive Park, Burlington, MA 01803; e-mail: alan.strom@faa.gov; 
telephone (781) 238-7143; fax (781) 238-7199.

Definition

    (k) For the purpose of this AD, an affected blade is a blade 
listed in Table 1 of this AD that has accumulated cycles within 100 
cycles, of the initial inspection thresholds in Table 1 of this AD.

Material Incorporated by Reference

    (l) You must use Rolls-Royce plc Alert Service Bulletin No. 
RB.211-72-AG244, Revision 1, dated January 26, 2010, Appendix 1, 
Appendix 2, and Appendices 3A through 3F of that ASB, to do the 
actions required by this AD.
    (1) For service information identified in this AD, contact 
Rolls-Royce plc, P.O. Box 31, DERBY, DE24 8BJ, UK; telephone 44 1332 
242424; fax 44 1332 249936; e-mail: royce.com">tech.help@rolls-royce.com.
    (2) You may review copies at the FAA, New England Region, 12 New 
England Executive Park, Burlington, MA; or at the National Archives 
and Records Administration (NARA). For information on the 
availability of this material at NARA, call (202) 741-6030, or go 
to: http://www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued in Burlington, Massachusetts, on April 1, 2011.
Peter A. White,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 2011-10521 Filed 5-2-11; 8:45 am]
BILLING CODE 4910-13-P


