[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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