[Federal Register Volume 77, Number 42 (Friday, March 2, 2012)]
[Proposed Rules]
[Pages 12755-12757]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-5094]


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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]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney (PW) Division Turbofan 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to adopt a new airworthiness directive (AD) for 
certain PW4000 series turbofan engines. This proposed 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, an LPT case 
puncture, and multiple in flight shutdowns. We are proposing this AD to 
prevent 3rd and 4th stage vane fractures in the LPT, which could damage 
the LPT rotor and lead to an uncontained engine failure and damage to 
the airplane.

DATES: We must receive comments on this proposed AD by May 1, 2012.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
     Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue SE., Washington, DC 20590.
     Hand Delivery: Deliver to Mail address above between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    For service information identified in this proposed AD, contact 
Pratt & Whitney, 400 Main St., East Hartford, CT 06108; phone: 860-565-
4321. You may review copies of the referenced service information at 
the FAA, Engine & Propeller Directorate, 12 New England Executive Park, 
Burlington, MA 01803. For information on the availability of this 
material at the FAA, call 781-238-7125.

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 proposed AD, the regulatory 
evaluation, any comments received, and other information. The street 
address for the Docket Office (phone: 800-647-5527) is in the ADDRESSES 
section. Comments will be available in the AD docket shortly after 
receipt.

FOR FURTHER INFORMATION CONTACT: James Gray, Aerospace Engineer, Engine 
Certification Office, FAA, 12 New England Executive Park; phone: 781-
238-7742; fax: 781-238-7199; email: james.e.gray@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposal. Send your comments to an address listed 
under the ADDRESSES section. Include ``Docket No. FAA-2012-0060; 
Directorate Identifier 2012-NE-02-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of this proposed AD. We 
will consider all comments received by the closing date and may amend 
this proposed AD because of those comments.
    We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact we 
receive about this proposed AD.

Discussion

    We have received reports of 3rd and 4th stage vane fractures in the 
LPT of certain PW4000-94'' and PW4000-100'' turbofan engines. These 
fractures caused an uncontained engine failure, an LPT case puncture, 
and multiple in flight shutdowns. We have identified four primary root 
causes for LPT vane failures:
    1. Inadequate retention of the vane in the case due to dimensional 
tolerances which causes 3rd stage vane liberations. This AD requires 
dimensional inspections of the 3rd stage vanes at their retention 
points and case at LPT assembly after overhaul.
    2. Non-uniform airfoil fillet radii found on vanes produced prior 
to 2005 which causes 4th stage vane fractures. This AD removes these 
vanes, identified by the casting identifier, from service at the next 
LPT overhaul.
    3. Multiple strip-and-recoat repairs of the 4th stage vanes which 
degrade the structural integrity of the vanes and cause 4th stage vane 
fractures. This AD removes from service 4th stage vanes with multiple 
strip-and-recoat repairs. This AD also prohibits approving for return 
to service any 4th stage vane with more than one strip-and-recoat 
repair.
    4. Aerodynamic excitation of the vanes which causes 4th stage vane 
fractures. The excitation is attributed to the rotor assembly methods 
for the upstream rotor stages. This AD requires reassembling the 2nd 
stage HPT blades at the next HPT overhaul and the 3rd stage LPT blades 
at the next LPT overhaul, using the latest assembly technique.
    The actions proposed in this AD are intended to address each of the 
root causes identified above. This condition, if not corrected, could 
result in 3rd and 4th stage vane fractures in the LPT, which could 
damage the LPT rotor and lead to an uncontained engine failure and 
damage to the airplane.

FAA's Determination

    We are proposing this AD because we evaluated all the relevant 
information and determined the unsafe condition described previously is 
likely to exist or develop in other products of the same type designs.

Proposed AD Requirements

    This proposed AD would require dimensional inspections of 3rd stage 
vanes and the rear turbine case. This AD also requires 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. This AD also requires disassembly and reassembly of the 
2nd stage HPT rotor and 3rd stage LPT rotor at the next HPT and LPT 
overhauls.

Costs of Compliance

    We estimate that this proposed AD affects 807 engines installed on 
airplanes of U.S. registry. We estimate that it would take 2 work-hours 
per engine to perform the LPT 3rd stage vane cluster assembly and rear 
turbine case inspections. The average labor rate

[[Page 12756]]

is $85 per work-hour. We expect that approximately 1,870 LPT 4th stage 
vane cluster assemblies will be found with the non-conforming casting 
identification. Replacement parts cost about $4,854. We estimate that 
limiting 4th stage vanes to one strip-and-recoat repair will remove \1/
3\ of the useful part life expectancy of the vanes on 323 engines at a 
prorated cost of $71,000 per engine. We do not associate any additional 
costs with reassembling 2nd stage HPT blades and 3rd stage LPT blades 
using the latest procedures as this is done at overhaul. Based on these 
figures, we estimate the cost of the proposed AD on U.S. operators to 
be $32,147,170.

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 products identified in this 
rulemaking action.

Regulatory Findings

    We determined that this proposed AD would not have federalism 
implications under Executive Order 13132. 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 this 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),
    (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.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 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. The FAA amends Sec.  39.13 by adding the following new 
airworthiness directive (AD):

Pratt & Whitney Division: Docket No. FAA-2012-0060; Directorate 
Identifier 2012-NE-02-AD.

(a) Comments Due Date

    We must receive comments by May 1, 2012.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to the following Pratt & Whitney Division (PW) 
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, which could damage the LPT 
rotor and lead to an 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 from service if more than one 
strip and recoat repair has been performed, or if the number of 
strip and recoat repairs are unknown. After the effective date of 
this AD, do not install or reinstall into any engine any LPT 4th 
stage vanes that have had more than one strip and recoat repair.
    (ii) Re-assemble the 3rd stage LPT rotor blades using a method 
that will alternate heavy blades next to light blades and balance 
blades of similar weights 180 degrees across the rotor.
    (iii) Inspect the LPT 3rd stage vane cluster assembly. Ensure 
adequate engagement between the vane cluster assembly and the rear 
turbine case.
    (iv) Examine the vane and airseal engagement slots on the rear 
turbine case where the 3rd stage vane is installed. Ensure adequate 
engagement exists for assembly of the 3rd stage vane cluster 
assembly and the rear turbine case.
    (v) Inspect the 44 LPT 4th stage vane cluster assemblies PN 
52N774-01 for casting identification ``51N554AT 1447 2S1C1'' and PN 
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 HPT overhaul, re-assemble the 2nd stage HPT 
rotor blades using a method that will alternate heavy blades next to 
light blades and balance blades of similar weights 180 degrees 
across the rotor.

(f) Alternative Methods of Compliance (AMOCs)

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

(g) Related Information

    (1) Guidance on the assembly method of paragraph (e)(1)(ii) of 
this AD can be found in the applicable engine manual: PN 50A605 or 
PN 50A822 Task 72-53-03-440-001, dated September 15, 2006; or PN 
50A443 Task 72-53-03-440-001, dated May 1, 2007; or PN 51A342 Task 
72-53-03-440-002-003, dated September 15, 2006.
    (2) Guidance on the dimensional inspection of paragraph 
(e)(1)(iii) of this AD can be found in the Clean Inspect Repair 
Manual, PN 51A357 Task 72-53-23-200-004, dated January 15, 2011.
    (3) Guidance on the dimensional inspections of paragraph 
(e)(1)(iv) of this AD can be found in the Clean Inspect Repair 
Manual, PN 51A357 Subtask 72-53-17-220-060, dated September 15, 
2009.
    (4) Guidance on the assembly method of paragraph (e)(2) of this 
AD can be found in the applicable engine manual: PN 50A605, 
PN50A822, or PN50A443 Task 72-52-02-440-001, dated May 1, 2010; or 
PN 51A342 Task 72-52-02-440-001, dated September 15, 2011.
    (5) For more information about this AD, contact James Gray, 
Aerospace Engineer, Engine Certification Office, FAA, 12 New England 
Executive Park; phone: 781-238-7742; fax: 781-238-7199; email: 
james.e.gray@faa.gov.
    (6) For service information identified in this AD, contact Pratt 
& Whitney, 400 Main St., East Hartford, CT 06108; phone: 860-565-
4321. You may review copies of the referenced service information at 
the FAA,

[[Page 12757]]

Engine & Propeller Directorate, 12 New England Executive Park, 
Burlington, MA 01803. For information on the availability of this 
material at the FAA, call 781-238-7125.

    Issued in Burlington, Massachusetts, on February 27, 2012.
Peter A. White,
Manager, Engine & Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-5094 Filed 3-1-12; 8:45 am]
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