Document ID: FAA-2012-0071-0009
Agency: faa
Document Type: Rule
Title: Airworthiness Directives: Pratt&Whitney Canada, Auxiliary Power Units
Posted Date: 2012-09-17T04:00Z

[Federal Register Volume 77, Number 180 (Monday, September 17, 2012)]
[Rules and Regulations]
[Pages 57001-57003]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-22532]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2012-0071; Directorate Identifier 2012-NE-05-AD; 
Amendment 39-17191; AD 2012-18-14]
RIN 2120-AA64

Airworthiness Directives; Pratt & Whitney Canada, Auxiliary Power 
Units

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are adopting a new airworthiness directive (AD) for certain 
serial numbers of Pratt & Whitney Canada (P&WC) PW901A auxiliary power 
units (APUs) approved under Technical Standard Order TSO-C77A and 
installed on, but not limited to, Boeing 747-400 series airplanes. This 
AD requires modifications of the rear gas generator case, exhaust duct 
support, and turbine exhaust duct flanges. This AD was prompted by 
several events of high-pressure turbine blade fracture leading to 
separation of the rear gas generator case and release of high energy 
debris. We are issuing this AD to prevent separation of the rear gas 
generator case and release of high energy debris, which could result in 
injury and damage to the airplane.

DATES: This AD becomes effective October 22, 2012. The Director of the 
Federal Register approved the incorporation by reference of certain 
publications listed in this AD as of October 22, 2012.

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: Mazdak Hobbi, Aerospace Engineer, New 
York Aircraft Certification Office, FAA, Engine & Propeller 
Directorate, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: 
516-228-7330; fax: 516-794-5531; email: mazdak.hobbi@faa.gov.

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 February 27, 2012 
(77 FR 11421). That NPRM proposed to correct an unsafe condition for 
the specified products. Transport Canada, which is the aviation 
authority for Canada, has issued AD CF-2011-40, dated October 26, 2011 
(referred to after this as ``the MCAI''), to correct an unsafe 
condition for the specified products. The MCAI states:

    The PW901A Auxiliary Power Units have experienced several events 
of High Pressure Turbine (HPT) blade fracture, some of which have 
resulted in the separation of the rear gas generator case, exhaust 
duct support, the turbine exhaust duct flanges and the release of 
high energy debris. Subsequent investigation revealed the turbine 
exhaust duct can separate under excessive load conditions resulting 
from extreme engine distress such as HPT blade fractures.

You may obtain further information by examining the MCAI in the AD 
docket.

Comments

    We gave the public the opportunity to participate in developing 
this AD. We considered the comments received. The following presents 
the comments received on the proposal and the FAA's response to each 
comment.

Support for the NPRM

    The Boeing Company indicated it supported the content of the 
proposed rule.

Request To Increase Compliance Time

    Several commenters believed the compliance time in the AD should be 
extended. Atlas Air requested that the compliance time be increased 
from 42 to 60 months. Atlas Air noted that the 42-month requirement 
would force them to remove APUs prior to their 8,000 hours soft time 
threshold which is based on their budget and operating experience and 
reliability. This threshold would increase the maintenance burden and 
cost to Atlas Air.
    KLM Royal Dutch Airlines (KLM) also requested that the compliance 
date be extended. KLM indicated that requiring all the affected APUs be 
modified in 42 months would require forced unscheduled replacements.
    United Airlines (UAL) also requested that the compliance time be 
extended from 42 to 48 months. United indicated that the 42-month 
compliance time would require engines to be removed prematurely and 
cause capacity problems for repair shops.
    We do not agree. We have no data that justifies extending the 
compliance time to 48 months. Operators who want to a longer compliance 
interval may request an AMOC using the procedures in 14 CFR part 39. 
Operators contemplating an AMOC request are reminded that they must 
show that their extension will

[[Page 57002]]

provide the same level of safety as provided by the 42-month compliance 
interval.

Request To Increase Compliance Time for Those APUs Incorporating 
Previous SB

    KLM also requested a longer compliance period for APU's modified 
per SB 3910001-49-16250. KLM commented that the risk for these blades 
is lower than the pre-SB blades. United Parcel Service Company also 
requested that the compliance period be increased from 42 to 60 months 
for APUs having SB-16250 previously incorporated (improved HPT blades).
    We do not agree. We have no data supporting the conclusion that 
APUs modified per SB 3910001-49-16250 have a lower risk of separation 
of the rear gas generator case or that an increased compliance time is 
justified for these blades. We did not change the AD based on this 
comment.

Question on Compliance Date

    KLM asked what the compliance date for this AD would be, since the 
compliance date in AD CF-2011-40, dated October 26, 2011, is different 
from the date in Pratt & Whitney Canada Service Bulletin (SB) 3910001-
49-16255, Revision No. 2, dated March 1, 2011.
    The compliance date for this AD will be 35 days after the date the 
AD is published in the Federal Register. We did not change the AD based 
on this comment.

Comment on Failure To Address Root Cause

    KLM indicated that accomplishing SB 391001-49-16255, Revision No. 
2, dated March 1, 2011, and our AD will not prevent high pressure 
turbine blades from failing.
    We do not agree. The root cause of the failure of the HPT blades is 
excessive load resulting from extreme engine distress, which leads to 
turbine exhaust duct separation. Accomplishing SB 391001-49-A16255, 
Revision No. 2, dated March 1, 2011, will mitigate excessive load by 
modifying the rear gas generator case, exhaust duct support and the 
turbine exhaust duct flanges. We did not change the AD based on this 
comment.

Comment on Increased Man-hours Needed To Accomplish the AD

    KLM noted that not all APUs can be modified during an overhaul. 
Therefore, extra man-hours will be required to perform this 
modification.
    We do not agree. The man-hours indicated in the SB and in this AD 
are sufficient to modify the APU. The number of hours required to 
perform an engine overhaul is not the subject of this AD. We did not 
change the AD based on this comment.

Request To Clarify ``Preventative Maintenance'' in Compliance Statement

    Southern Air indicated that compliance paragraph (e)(1) is 
misleading wherein it states ``within 42 months after effective date of 
the AD or the first time any maintenance is done other than 
preventative maintenance, whichever occurs first * * *.'' Southern Air 
believes the statement should read: ``42 months after the effective 
date of the AD or when maintenance which requires unmating of the 
flanges, or overhaul, whichever occurs first.''
    UAL indicated the term ``preventative maintenance'' in paragraph 
(e)(1) is vague and ambiguous. UAL noted that as currently stated the 
AD would have to be accomplished if one was replacing a line 
replaceable unit like an exciter or starter. UAL suggested that the 
maintenance be accomplished when the exhaust support duct is 
accessible, i.e., removed from the APU.
    We agree. We changed paragraph (e)(1) of the AD to read ``Within 42 
months after the effective date of this AD or the first time the APU or 
module is at a maintenance facility that can perform the modifications, 
regardless of the maintenance action or reason for APU removal, 
whichever occurs first, modify the rear gas generator case, exhaust 
duct support, and turbine exhaust duct flanges.''

Request Not To Mandate Use of Service Bulletin in Compliance Section

    UAL commented that several steps in the accomplishment instructions 
in P&WC SB No. 3910001-49-A16255, Revision No. 2, do not offer an 
increase in safety and should not be mandated by the AD. UAL noted that 
the component maintenance manual offers sufficient instructions to 
perform the required modifications.
    We do not agree. UAL did not identify any unnecessary steps, we 
know of none, and our inquiry of the OEM did not identify any 
unnecessary steps. If the OEM determined that the component maintenance 
manual was adequate, it would have been referenced in SB No. 3910001-
49-A16255, Revision No. 2. We did not change the AD based on this 
comment.

Questions on APU Continuing To Meet Type Certification Requirements

    KLM asked that since the APU was originally certified to a TSO 
should the certification basis be maintained during the lifetime of 
operation.
    We reply to KLM's multi-layered comment as follows. First, we 
granted TSO approval to PWC for this APU on September 20, 1988. Second, 
the corrective actions required by this AD should return the product to 
the level of safety intended by its certification basis. Finally, 
whether or not an OEM covers the cost of actions mandated by our AD 
actions is between the OEM and the product owner/operator.

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 affects 
about 135 APUs installed on airplanes of U.S. registry. The average 
labor rate is $85 per work-hour. Required parts cost about $39,899 per 
APU. Based on these figures, we estimate the cost of the AD on U.S. 
operators to be $5,386,365.

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

[[Page 57003]]

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
    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:

2012-18-14 Pratt & Whitney Canada: Amendment 39-17191; Docket No. 
FAA-2012-0071; Directorate Identifier 2012-NE-05-AD.

(a) Effective Date

    This airworthiness directive (AD) becomes effective October 22, 
2012.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to Pratt & Whitney Canada (P&WC) PW901A 
auxiliary power units (APUs) approved under Technical Standard Order 
TSO-C77A and installed on, but not limited to, Boeing 747-400 series 
airplanes. The affected APU serial numbers are PCE 900001 through 
PCE 900776 inclusive.

(d) Reason

    This AD was prompted by several events of high-pressure turbine 
blade fracture leading to separation of the rear gas generator case 
and release of high energy debris. We are issuing this AD to prevent 
separation of the rear gas generator case and release of high energy 
debris, which could result in injury and damage to the airplane.

(e) Actions and Compliance

    Unless already done, do the following actions.
    (1) Within 42 months after the effective date of this AD or the 
first time the APU or module is at a maintenance facility that can 
perform the modifications, regardless of the maintenance action or 
reason for APU removal, whichever occurs first, modify the rear gas 
generator case, exhaust duct support, and turbine exhaust duct 
flanges.
    (2) Use paragraphs 3.A. through 3.B(3)(f) of Accomplishment 
Instructions, and paragraph 4.A. of Appendix, of P&WC Alert Service 
Bulletin (SB) No. 39100001-49-A16255, Revision No. 2, dated March 1, 
2011, to do the modifications.

(f) Credit for Previous Action

    APUs modified before the effective date of this AD using P&WC 
Alert SB No. A16255R1, dated September 12, 2008, or P&WC Alert SB 
No. A16255, dated December 12, 2007, meet the modification 
requirements of this AD.

(g) Alternative Methods of Compliance (AMOCs)

    The Manager, New York Aircraft Certification Office, FAA, may 
approve AMOCs for this AD. Use the procedures found in 14 CFR 39.19 
to make your request.

(h) Related Information

    (1) For more information about this AD, contact Mazdak Hobbi, 
Aerospace Engineer, New York Aircraft Certification Office, FAA, 
Engine & Propeller Directorate, 1600 Stewart Avenue, Suite 410, 
Westbury, NY 11590; phone: 516-228-7330; fax: 516-794-5531; email: 
mazdak.hobbi@faa.gov.
    (2) Refer to Transport Canada AD CF-2011-40, dated October 26, 
2011, and P&WC SB No. A16255R2, dated March 1, 2011, for related 
information.

(i) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference (IBR) of the following service 
information under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use the following service information to do the 
actions required by this AD, unless the AD specifies otherwise:
    (i) Pratt & Whitney Canada Alert Service Bulletin No. 3910001-49 
A16255, Revision No. 2, dated March 1, 2011.
    (ii) Reserved.
    (3) For service information identified in this AD, contact Pratt 
& Whitney Canada Corp., 1000 Marie-Victorin, Longueuil, Quebec, 
Canada J4G 1A1; phone: 450-677-9411.
    (4) You may view this service information at the FAA, Engine & 
Propeller Directorate, 12 New England Executive Park, Burlington, 
MA. For information on the availability of this material at the FAA, 
call 781-238-7125.
    (5) You may view this service information 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 August 27, 2012.
Colleen M. D'Alessandro,
Assistant Manager, Engine & Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 2012-22532 Filed 9-14-12; 8:45 am]
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