[Federal Register Volume 77, Number 192 (Wednesday, October 3, 2012)]
[Rules and Regulations]
[Pages 60288-60296]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-23791]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2012-0060; Directorate Identifier 2012-NE-02-AD; 
Amendment 39-17123; AD 2012-14-09]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney (P&W) Division 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 certain 
P&W PW4000 series turbofan engines. This AD was prompted by reports of 
3rd and 4th stage vane fractures in the low-pressure turbine (LPT) of 
certain PW4000-94'' and PW4000-100'' turbofan engines. This AD requires 
dimensional inspections of LPT 3rd stage vanes and the rear turbine 
case, inspection of LPT 4th stage vanes at the next LPT overhaul and 
removal of vanes with non-conforming airfoil fillet radii and vanes 
with more than one strip and recoat repair. This AD also requires 
disassembly and reassembly of the 2nd stage high-pressure turbine (HPT) 
rotor and 3rd stage LPT rotor at the next HPT and LPT overhauls. We are 
issuing this AD to prevent 3rd and 4th stage vane fractures in the LPT, 
damage to the LPT rotor, uncontained engine failure, and damage to the 
airplane.

DATES: This AD is effective November 7, 2012.

ADDRESSES: For more information about this AD, contact James Gray, 
Aerospace Engineer, Engine Certification Office, FAA, Engine & 
Propeller Directorate, 12 New England Executive Park, Burlington, MA; 
phone: 781-238-7742; fax: 781-238-7199; email: [email protected].

Examining the AD Docket

    You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility 
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 address for the 
Docket Office (phone: 800-647-5527) is Document Management Facility, 
U.S. Department of Transportation, Docket Operations, M-30, West 
Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE., 
Washington, DC 20590.

[[Page 60289]]


FOR FURTHER INFORMATION CONTACT: James Gray, Aerospace Engineer, Engine 
Certification Office, FAA, Engine & Propeller Directorate, 12 New 
England Executive Park, Burlington, MA; phone: 781-238-7742; fax: 781-
238-7199; email: [email protected].

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 published in the Federal Register on March 2, 2012 (77 FR 
12755). That NPRM proposed to require dimensional inspections of 3rd 
stage vanes and the rear turbine case. That NPRM also proposed to 
require inspection of 4th stage vanes at the next LPT overhaul and 
removal of vanes with non-conforming airfoil fillet radii and vanes 
with more than one strip and recoat repair. That NPRM also proposed to 
require disassembly and reassembly of the 2nd stage HPT rotor and 3rd 
stage LPT rotor at the next HPT and LPT overhauls.

Comments

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

Agreement With the Proposed AD

    Two commenters, Boeing and FedEx, agreed with the intent of the 
proposed AD.

Request To Change Compliance Time for the 4th Stage Vanes

    One commenter, China Cargo Airlines, requested that we change the 
inspection compliance time for the LPT 4th stage vanes from ``next LPT 
overhaul'' to ``next engine overhaul.'' The commenter stated that LPT 
overhauls are typically performed every other shop visit, which could 
be in six-to-eight years. The commenter thought that the risk of having 
a 4th stage vane failure during that time was too high.
    We do not agree. We determined that performing the inspections at 
the next LPT overhaul after the effective date of the AD provides an 
acceptable level of safety, and that we do not need to reduce the 
interval. We did not change the AD.

Request for Credit for Prior Compliance

    FedEx requested that a statement be included authorizing credit for 
prior compliance as they have already been performing the requirements 
of the proposed AD.
    We do not agree. Paragraph (e) of the proposed AD already allows 
credit for prior compliance. That paragraph states to comply with the 
AD within the compliance times specified, unless already done. We did 
not change the AD.

Request To Reference Pratt & Whitney Special Instruction No. 17F-09

    One commenter, Martinair Holland, requested that we add a reference 
to Pratt & Whitney Special Instruction No. 17F-09 as an alternate 
method of compliance (AMOC) for paragraph (e)(1)(iii). The commenter 
stated that they have been checking the 3rd stage vanes for adequate 
engagement using that Special Instruction.
    We do not agree. The AD requires dimensional inspections that are 
not included in Special Instruction No. 17F-09. Also, we do not include 
AMOCs in the requirements of an AD. You may, however, seek an AMOC 
using the procedures specified in the AD. We did not add that Special 
Instruction reference to the AD.

Request To Add Service Bulletins as Alternate Methods of Compliance

    Martinair Holland, United Airlines, and Onur Air, requested that we 
add references to Pratt & Whitney Service Bulletins (SBs) PW4ENG 72-
798, PW4ENG 72-804, and PW4G-100-72-221, as alternate methods of 
compliance to paragraph (e)(1)(v). The commenters stated that they have 
been inspecting the LPT 4th stage vanes using these SBs.
    We do not agree. Paragraph (e) of the proposed AD states to comply 
with the AD within the compliance times specified, unless already done. 
If you have already done the proposed actions, then no further action 
is required to comply with paragraph (e)(1)(v). Also, as noted above, 
we do not include AMOCs in the requirements of an AD. We did not change 
the AD.

Request To Include the Part Numbers (P/Ns) of the LPT 4th Stage Vanes

    Pratt & Whitney requested that we include the P/Ns of the LPT 4th 
stage vanes that are subject to the one-time strip and recoat 
requirement. The commenter stated that it is possible that future 
designs of LPT 4th stage vanes would not be restricted to a single 
strip and recoat requirement.
    We agree. We listed the P/Ns of the affected LPT 4th stage vanes in 
the AD.

Request To Define the Word ``Guidance''

    United Airlines requested that we define the word ``guidance'' 
which we used in paragraph (g) of the proposed AD, or, that we revise 
the wording to specifically detail the inspection/build procedure to be 
used. The commenter states that using the term ``guidance'' does not 
denote a specific requirement and only suggests a general direction to 
be followed.
    We agree. Use of the word ``guidance'' in this AD may have caused 
confusion. We deleted the ``guidance'' paragraphs listed under Related 
Information from the AD.

Request To Update Guidance Service Information

    Pratt & Whitney and United Parcel Service Co. (UPS) requested that 
we add the words ``or later'' after the service information date 
references in paragraph (g) of the proposed AD. They also requested 
that we clarify that the referenced service information could be 
updated, and compliance to that updated service information would be 
acceptable. One of the commenters was concerned that service 
information listed as guidance would be controlled in the same way as 
service information that is incorporated by reference in the AD.
    We do not agree. We do not know how documents will be revised in 
the future. This AD, however, was revised to remove references to 
related service information, and therefore the comment no longer 
applies. We did not change the AD.

Request To Remove the Term ``Overhaul''

    United Airlines and UPS requested that we remove the term 
``overhaul,'' such as ``LPT overhaul'' and ``HPT overhaul'' from the 
proposed AD compliance, as the term ``overhaul'' is not industry 
standard and therefore subjective. The commenters suggested a few 
alternatives to use instead of the term ``overhaul.''
    We partially agree. We do not agree that the term ``overhaul'' 
should be removed, but we do agree that it should be defined. We added 
a definition paragraph which states that, for the purpose of this AD, 
an overhaul is when all disks in the rotor are removed from the engine 
and the blades are removed.

Request To Clarify Approved Methods of Compliance

    UPS requested that we clarify that the service information listed 
under Related Information are approved methods of compliance to the 
proposed AD. They further stated that, as-written, it is not clear that 
they are approved methods of compliance.
    We agree that the AD should be clarified. We revised the AD by

[[Page 60290]]

removing references to related service information.

Request To Duplicate the Strip and Recoat Requirements

    United Airlines requested that we duplicate the strip and recoat 
requirements and make them part of Inspection/Check-01 or Inspection/
Check-03 of the PW4000 Engine Cleaning Inspection and Repair (CIR) 
Manual. The commenter stated that the strip and recoat limits are 
currently located in repair-14 of the PW4000 CIR Manual, but repair-14 
is not always required to return a vane cluster to service. The 
commenter stated that the strip and recoat requirements need to be part 
of the normal inspection process.
    We do not agree. The AD mandates that the inspection be performed 
once, at the next LPT overhaul. That inspection will purge the fleet of 
LPT 4th stage vanes that have had more than one strip and recoat 
repair. After that inspection, LPT 4th stage vanes are not allowed to 
have more than one strip and recoat repair, as specified in the 
installation prohibition paragraph (f). Revising the engine manuals to 
relocate the inspection requirements is unnecessary. We did not change 
the AD.

Request To Remove Reference to 4th Stage Vanes With an Unknown Number 
of Strip and Recoat Repairs

    United Airlines stated that there is no way to identify vanes with 
an unknown number of strip and recoat repairs. The commenter stated 
that if there were no markings on the vane, it would indicate that no 
strip and recoat repairs were performed. This could lead to scrapping 
vanes that could otherwise be repaired and returned to service.
    We agree. We changed the AD to eliminate the reference to LPT 4th 
stage vanes with an unknown number of strip and recoat repairs.

Request To Make the CIR Inspections More Specific

    United Airlines requested that in proposed AD paragraph (e)(1)(iv) 
we make the CIR inspections more specific for the LPT case dimensions. 
The commenter stated that there are different ways to perform the 
measurements and it is not clear whether the dimension to measure is 
based on an average or an individual diametric dimension.
    We do not agree. A specific measurement technique is not defined 
because multiple measurement techniques exist that are acceptable. The 
only diametric dimensional inspection required by the AD is index 24, 
which would be acceptable to measure based on an average dimension. We 
did not change the AD.

Request To Change ``Ensure Adequate Engagement''

    United Airlines requested that in proposed AD paragraphs 
(e)(1)(iii) and (e)(1)(iv), we change ``ensure adequate engagement'' to 
``dimensionally inspect the applicable LPT case slot serviceable 
dimensions and 3rd stage vane serviceable dimensions per the 
appropriate CIR.'' The commenter also requested that we list the 
specific dimensions to inspect by index number. The commenter stated 
that no mechanic can deduce what an adequate engagement is because it 
is not specific enough.
    We agree. We changed paragraph (e)(1)(iii) to ``dimensionally 
examine index 13 through index 34 of the LPT 3rd stage vane cluster 
assembly.'' We also changed paragraph (e)(1)(iv) to ``dimensionally 
examine index 23 and index 24 of the vane engagement slots on the rear 
turbine case, where the 3rd stage vane is installed.'' We also listed 
the specific dimensions to inspect by index number, and included the 
supporting figures in this AD.

Request To Eliminate Paragraphs

    United Airlines requested that we eliminate paragraphs (e)(1)(ii) 
through (e)(1)(iv) and (e)(2). The commenter stated that these 
paragraphs are related to procedures that are in the engine manual that 
operators are already performing. If they are left in the AD, they will 
add a significant burden in the amount of time and paperwork required 
to manage and verify compliance to the AD.
    We do not agree. The actions in the paragraphs the commenter wants 
eliminated from the AD represent changes to the manuals that were 
specifically incorporated to address 3rd and 4th stage vane failures. 
Although air carriers operating under 14 Code of Federal Regulations 
(CFR) Part 121 are likely using the most current versions of the engine 
manuals, not all operators, for example, part 91 operators, may be 
required to incorporate the latest versions of the engine manuals. 
Therefore, we must maintain these requirements in the AD to ensure that 
all operators comply to resolve the unsafe condition. We did not change 
the AD.

Revision to Cost of Compliance

    In reviewing the cost of compliance estimate made in the NPRM (77 
FR 12755, March 2, 2012), we determined that we were unable to 
substantiate our prorated cost estimate for limiting the number of 
strip and recoat repairs since we do not know how many vanes are 
operating with more than one strip and recoat repair. We, therefore, 
removed the estimate of the useful part life expectancy and only 
included the replacement parts cost. The total cost estimate changed 
from $32,147,170 to $9,214,170.

Conclusion

    We reviewed the relevant data, considered the comments received, 
and determined that air safety and the public interest require adopting 
the AD with the changes described previously. We have determined that 
these changes:
     Are consistent with the intent that was proposed in the 
NPRM (77 FR 12755, March 2, 2012) for correcting the unsafe condition; 
and
     Do not add any additional burden upon the public than was 
already proposed in the NPRM (77 FR 12755, March 2, 2012).
    We also determined that these changes will not increase the 
economic burden on any operator or increase the scope of the AD.

Costs of Compliance

    We estimate that this AD affects 807 engines installed on airplanes 
of U.S. registry. We estimate that it will take 2 work-hours per engine 
to perform the LPT 3rd stage vane cluster assembly and rear turbine 
case inspections. The average labor rate is $85 per work-hour. We 
expect that about 1,870 LPT 4th stage vane cluster assemblies will be 
found with the non-conforming casting identification. Replacement parts 
cost about $4,854. Based on these figures, we estimate the cost of the 
AD on U.S. operators to be $9,214,170.

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

[[Page 60291]]

products identified in this rulemaking action.

Regulatory Findings

    This AD will not have federalism implications under Executive Order 
13132. This AD will not have a substantial direct effect on the States, 
on the relationship between the national government and the States, or 
on the distribution of power and responsibilities among the various 
levels of government.
    For the reasons discussed above, I certify that this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979),
    (3) Will not affect intrastate aviation in Alaska, and
    (4) 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.

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 airworthiness 
directive (AD):

2012-14-09 Pratt & Whitney Division: Amendment 39-17123; Docket No. 
FAA-2012-0060; Directorate Identifier 2012-NE-02-AD.

(a) Effective Date

    This AD is effective November 7, 2012.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to the following Pratt & Whitney Division 
turbofan engines:
    (1) PW4000-94'' engine models PW4050, PW4052, PW4056, PW4152, 
PW4156, PW4650, PW4060, PW4060A, PW4060C, PW4062, PW4062A, PW4156A, 
PW4158, PW4160, PW4460, and PW4462 including models with any dash 
number suffix.
    (2) PW4000-100'' engine models PW4164, PW4164C, PW4164C/B, 
PW4168, PW4168A, PW4164-1D, PW4164C-1D, PW4164C/B-1D, PW4168-1D, 
PW4168A-1D, and PW4170.

(d) Unsafe Condition

    This AD was prompted by reports of 3rd and 4th stage vane 
fractures in the low-pressure turbine (LPT) of certain PW4000-94'' 
and PW4000-100'' turbofan engines. These fractures caused an 
uncontained engine failure and an LPT case puncture, and resulted in 
multiple in flight shutdowns. We are issuing this AD to prevent 3rd 
and 4th stage vane fractures in the LPT, damage to the LPT rotor, 
uncontained engine failure, and damage to the airplane.

(e) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.
    (1) At the next LPT overhaul, do the following:
    (i) Remove LPT 4th stage vanes that have a P/N listed in Table 1 
to paragraph (e) of this AD from service if more than one strip and 
recoat repair has been performed.

       Table 1 to Paragraph (e)--Affected LPT 4th Stage Vane P/Ns
------------------------------------------------------------------------
 
------------------------------------------------------------------------
      50N174      50N674-01     51N174-001     51N374-001     52N574-01
   50N474-01      50N774-01     51N174-002      51N674-01     52N674-01
  50N474-001     50N774-001     51N174-003      52N274-01     51N774-01
   50N574-01      51N174-01      51N374-01      52N474-01     52N774-01
------------------------------------------------------------------------

    (ii) Re-assemble the 3rd stage LPT rotor blades by alternating 
heavy blades next to light blades and balancing blades of similar 
weights 180 degrees across the rotor.
    (iii) Dimensionally examine index 13 through index 34 of the LPT 
3rd stage vane cluster assembly. Use Table 2 to paragraph (e) of 
this AD and Figure 1, Figure 2, and Figure 3 to paragraph (e) of 
this AD to determine whether the vane is eligible for installation.

                           Table 2 to Paragraph (e)--Determination of Vane Eligibility
----------------------------------------------------------------------------------------------------------------
                  Inspect:                                     Eligible for installation limits:
----------------------------------------------------------------------------------------------------------------
13..........................................  1.820-1.830 inches (46.23-46.48 mm).
14..........................................  1.920-1.930 inches (48.77-49.02 mm).
15..........................................  3.200 inches (81.280 mm) Basic.
16..........................................  0.900 inch (22.860 mm) Basic.
17..........................................  0.365 inch (9.271 mm) Basic.
18..........................................  0.350 inch (8.890 mm) Basic.
19..........................................  0.160 inch (4.064 mm) Basic.
20..........................................  0.772 inch (19.609 mm) Basic.
21..........................................  72[deg] Basic.
22..........................................  22.382 inch (568.503 mm) Radius--Origin on Plane S Basic.
23..........................................  21.052 inch (534.721 mm) Radius--Origin on Plane S, concentric
                                               with Index 8 Basic.
24..........................................  Angle from Plane S to Plane SL 3[deg]4'37'' Basic.
25..........................................  Angle from Plane S to Plane SM 6[deg]9'14'' Basic.
26..........................................  90[deg] Basic for typical airfoil section.
27:
    Distance from rear foot outer diameter
     surface to airfoil section along Planes
     S, SL, and SM.
        For Section B-B:....................  5.241 inches (133.121 mm).

[[Page 60292]]

 
        For Section E-E:....................  3.181 inches (80.797 mm).
        For Section J-J:....................  1.935 inches (49.149 mm).
28:
    Airfoil chord at Section J-J (1.935       1.346 inches (34.188 mm) minimum.
     inches (49.149 mm) from rear foot outer
     diameter surface at Planes S, SL, and
     SM).
    At Section E-E (3.181 inches (80.797 mm)  1.314 inches (33.376 mm) minimum.
     from rear foot outer diameter surface
     at Planes S, SL, and SM).
    At Section B-B (5.241 inches (133.121     1.188 inches (30.175 mm) minimum.
     mm) from rear foot outer diameter
     surface at Planes S, SL, and SM).
29:
    Airfoil thickness at Section J-J (1.935   0.239 inch (6.071 mm) minimum.
     inches (49.149 mm) from rear foot outer
     diameter surface at Planes S, SL, and
     SM).
    At Section E-E (3.181 inches (80.797 mm)  0.183 inch (4.648 mm) minimum.
     from rear foot outer diameter surface
     at Planes S, SL, and SM).
    At Section B-B (5.241 inches (133.121     0.139 inch (3.531 mm) minimum.
     mm) from rear foot outer diameter
     surface at Planes S, SL, and SM).
30:
    Distance to trailing edge measurement...  0.062 inch (1.575 mm).
31:
    Airfoil trailing edge thickness.........  0.030 inch (0.762 mm) minimum.
32:
    Dimension...............................  0.315-0.324 inch (8.001-8.230 mm) diameter.
33:
    Dimension...............................  6.785-6.795 inches (172.34-172.59 mm).
34:
    Dimension...............................  0.692-0.714 inch (17.58-18.14 mm).
----------------------------------------------------------------------------------------------------------------

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    (iv) Dimensionally examine index 23 and index 24 of the vane 
engagement slots on the rear turbine case, where the 3rd stage vane 
is installed. Use Table 3 to paragraph (e) of this AD and Figure 4 
to paragraph (e) of this AD to determine whether the case is 
eligible for installation.

       Table 3 to Paragraph (e)--Determination of Case Eligibility
------------------------------------------------------------------------
             Inspect:                Eligible for installation limits:
------------------------------------------------------------------------
23...............................  1.875 inch (47.625 mm) minimum.
24...............................  0.097 inch (2.464 mm) minimum.
------------------------------------------------------------------------


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[GRAPHIC] [TIFF OMITTED] TR03OC12.003

    (v) Inspect the 44 LPT 4th stage vane cluster assemblies P/N 
52N774-01 for casting identification ``51N554AT 1447 2S1C1'' and P/N 
52N674-01 for casting identification ``51N454AT 655 2S1C1.'' Remove 
the vane cluster assembly from service if either of these casting 
identifications is found.
    (2) At the next high-pressure turbine (HPT) overhaul, re-
assemble the 2nd stage HPT rotor blades by alternating heavy blades 
next to light blades and balancing blades of similar weights 180 
degrees across the rotor.

(f) Installation Prohibition

    After the effective date of this AD, do not install or reinstall 
into any engine any LPT 4th stage vanes with a P/N listed in Table 1 
to paragraph (e) of this AD that are at piece-part exposure and have 
had more than one strip and recoat repair.

(g) Definitions

    (1) For the purpose of this AD, an HPT or LPT overhaul occurs 
when all disks in the rotor are removed from the engine and the 
blades are removed.
    (2) For the purpose of this AD, piece-part exposure means that 
the part is removed from the engine and completely disassembled.

(h) Alternative Methods of Compliance (AMOCs)

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

(i) Related Information

    For more information about this AD, contact James Gray, 
Aerospace Engineer, Engine Certification Office, FAA, Engine & 
Propeller Directorate, 12 New England Executive Park, Burlington, 
MA; phone: 781-238-7742; fax: 781-238-7199; email: 
[email protected].

(j) Material Incorporated by Reference

    None.

    Issued in Burlington, Massachusetts, on September 20, 2012.
Diane M. Cook,
Acting Manager, Engine & Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-23791 Filed 10-2-12; 8:45 am]
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