Document ID: FAA-2008-1131-0008
Agency: faa
Document Type: Rule
Title: Airworthiness Directives; Pratt and Whitney Models PW2037, PW2037(M), and PW2040 Turbofan Engines
Posted Date: 2009-05-13T04:00Z

[Federal Register: May 13, 2009 (Volume 74, Number 91)]
[Rules and Regulations]               
[Page 22426-22429]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr13my09-4]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-1131; Directorate Identifier 2008-NE-37-AD; 
Amendment 39-15903; AD 2009-10-08]
RIN 2120-AA64

 
Airworthiness Directives; Pratt & Whitney Models PW2037, 
PW2037(M), and PW2040 Turbofan Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
Pratt & Whitney models PW2037, PW2037(M), and PW2040 turbofan engines 
with high-pressure turbine (HPT) 2nd stage hubs that have previously 
been exposed to Pratt & Whitney cleaning procedure SPOP 10 or SPOP 9 or 
equivalent procedure. This AD requires a onetime optical comparator 
inspection (OCI) of the blade retention slots of the affected HPT 2nd 
stage hubs at the next HPT overhaul after the effective date of the AD. 
This AD results from an uncontained release of HPT 2nd stage blades and 
blade retention lugs. We are issuing this AD to remove nonconforming 
HPT 2nd stage hubs, which could result in an uncontained release of 
turbine blades and blade retention lugs, and damage to the airplane.

DATES: This AD becomes effective June 17, 2009.

ADDRESSES: You can get the service information identified in this AD 
from Pratt & Whitney, 400 Main Street, East Hartford, CT 06108.
    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: Mark Riley, Aerospace Engineer, Engine 
Certification Office, FAA, Engine and Propeller Directorate, 12 New 
England Executive Park, Burlington, MA 01803; e-mail: 
mark.riley@faa.gov; telephone (781) 238-7758, fax (781) 238-7199.

SUPPLEMENTARY INFORMATION: The FAA proposed to amend 14 CFR part 39 
with a proposed AD. The proposed AD applies to PW models PW2037, 
PW2037(M), and PW2040 turbofan engines. We published the proposed AD in 
the Federal Register on November 14, 2008 (73 FR 67427). That action 
proposed to require inspecting all HPT 2nd stage hubs at the next HPT 
overhaul after the effective date of the AD.

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 (telephone (800) 647-5527) is provided in 
the ADDRESSES section. Comments will be available in the AD docket 
shortly after receipt.

Comments

    We provided the public the opportunity to participate in the 
development of this AD. We have considered the comments received.

Recommend Referring to the Inspection as ``Special Dimensional 
Inspection''

    Pratt & Whitney recommends that the inspection in the proposed AD 
be referred to as a ``Special Dimensional Inspection'' per Pratt & 
Whitney Alert Service Bulletin (ASB) PW2000 72-734, which is approved 
by the FAA. The proposed AD currently specifies an Optical Comparator 
Inspection (OCI). Use of the term ``Special Dimensional Inspection'' 
instead of OCI will provide better alignment with the inspection 
procedures that Pratt & Whitney is presently developing and for which 
it will seek FAA approval, to use as an alternative to OCI.
    We do not agree. The inspection is an OCI. Therefore, identifying 
the type of inspection the AD requires by its name is proper. We did 
not change the AD.

Request To Revise the Estimated Cost

    Pratt & Whitney and two air carriers request that we revise the 
estimated cost to perform an OCI. Pratt & Whitney states that the cost 
is higher than previously anticipated and we should add about $4,000 to 
the cost of each disk overhaul. Delta Air Lines states that the total 
cost is actually closer to $8,000 and it should include shipping 
($1,000), vendor charges ($5,900), and should take into account 
additional inventory required ($180,000 per hub) due to out-of-service 
time required to support the off-site inspection.
    We partially agree. We agree that the cost estimate in the proposed 
AD is not accurate. We do not agree that it should consider shipping 
charges or additional inventory requirements unique to each operator. 
We changed the cost to perform the OCI to $4,000 for each HPT stage 2 
hub as quoted by Pratt & Whitney and updated the total to $3,048,000.

Request for Clarification of the Inspection Being a Onetime Inspection

    Pratt & Whitney and two air carriers request clarification in the 
AD to state that the inspection is a onetime inspection. Also, Delta 
Air Lines comments that repetitive inspections should be required 
unless the cause of the hub out-of-tolerance condition is addressed. 
They also stated that the cause of the hub out-of-tolerance condition 
is not known and repetitive inspections are therefore required.
    We partially agree. We agree that we need to clarify that the OCI 
is a onetime inspection requirement. We changed the AD to clarify that 
the OCI is a onetime inspection requirement. We do not agree that the 
AD should require repetitive inspections. If we determine at a later 
date that repetitive inspections are required, we may issue an AD to 
require them.

Proposal To Eliminate the Fluorescent Penetrant Inspection

    Pratt & Whitney and United Airlines propose that we eliminate the 
fluorescent penetrant inspection (FPI) requirement for the HPT 2nd 
stage hub. FPI of the HPT 2nd stage hub is redundant, since it is 
already mandated per FAA AD 2005-18-03.
    We agree. We changed the AD to only require a onetime OCI of the 
HPT 2nd stage hub after the fluorescent penetrant

[[Page 22427]]

inspection and all shop cleaning processes have been completed.

Proposal To Reduce the Affected Population of HPT 2nd Stage Hubs

    Pratt & Whitney proposes that we reduce the affected population of 
HPT 2nd stage hubs to only those that have been exposed to Pratt & 
Whitney cleaning procedure SPOP 10 or SPOP 9 (cleaning processes that 
have similar abrasive characteristics) during their shop overhaul 
history. Based on recent findings from the NTSB-led investigation, the 
blade slot dimensional variations on the event hub and on other 
inspected hubs resulted from a specific process used during the 
cleaning of hubs during the normal overhaul process.
    We agree. We changed the AD applicability to state that this AD 
applies to Pratt & Whitney models PW2037, PW2037(M), and PW2040 
turbofan engines with HPT 2nd stage hubs that have previously been 
exposed to Pratt & Whitney cleaning procedure SPOP 10 or SPOP 9 or 
equivalent procedure.

Proposal To Delay Issuance of AD

    United Airlines proposes that we delay issuance of the AD, because 
initial OCI results are showing a 25% reject rate. This suggests that 
the proposed inspections will not detect the problem that led to the 
one industry failure. Otherwise, the industry failure rate would be 
higher. Consequently, issuing the AD would be premature, as the failure 
mechanism is not understood, and it is not clear that the proposed 
inspections will prevent future failures.
    We do not agree. The investigation identified that an out-of-
tolerance condition of the HPT 2nd stage hub blade slots is the cause 
of the failure event. However, the root cause of the out-of-tolerance 
condition is still under investigation, but is believed to have been 
caused by aggressive cleaning with an abrasive media blast. Inspection 
of the HPT 2nd stage hub blade slots is required to identify hubs that 
are out-of-tolerance, to minimize the risk of future failures. Pratt & 
Whitney is reviewing the current acceptance criteria for the OCI of HPT 
2nd stage hub blade slots, and if appropriate, may revise these limits 
to reduce the current reject rate. We did not change the AD.

Proposal To Remove the Reporting Requirement From the AD

    Three air carriers propose that we remove the requirement for 
operators to be responsible for reporting HPT 2nd stage hub OCI results 
within 72 hours of the inspection. Delta Air Lines also asks if they 
are required to report OCI results after the 6-month period, since not 
all of their HPT 2nd stage hubs will go through overhaul within 6 
months. The three air carriers state that it will be extremely 
difficult for operators to comply with the reporting requirements of 
the proposed rule, because it will not be the operators performing the 
inspections. The sole source that performs the inspections, (Pratt & 
Whitney), should be responsible for reporting to the FAA.
    We agree. We removed the reporting requirement from the AD.

Request That an Alternate Inspection Be Developed That Is Not Source-
Approved

    Two air carriers request that an alternate inspection method be 
developed that is not source-approved and will permit all overhaul 
shops the capability to perform the inspection. They state that Pratt & 
Whitney is currently the only source-approved vendor for the OCI. 
Operators are experiencing turn times in excess of 30 days, which is a 
hardship to them.
    We agree that an alternate inspection procedure that can be 
performed by all overhaul facilities is preferred. However, we are 
unaware of any that may exist. We will evaluate any proposed 
alternative inspection an operator may submit as an alternative method 
of compliance. We did not change the AD.

Compliance Time Should Be Revised

    The National Transportation Safety Board (NTSB), states that the 
compliance time should be revised to reflect the recommended compliance 
time in the NTSB Urgent Safety Recommendation A-08-85. That compliance 
time requires removal of all PW2037 2nd stage turbine hubs for 
inspection when they have accumulated significantly fewer hours and/or 
cycles than the incident engine (10,880 hours and/or 4,392 cycles). The 
10,880 hours and 4,392 cycles referenced in A-08-85 were based on the 
time and cycles that the incident engine had accumulated from the last 
overhaul until engine failure. Metallurgical examination of the failed 
hub was not able to discern any fatigue striations, so it is unknown 
how long it took those fatigue cracks to progress to failure. 
Typically, when the cause of the failure, or length of time for a crack 
to progress to failure is unknown, the time and/or cycles, whichever is 
less, since the part was new or overhauled until failure, is divided by 
a factor of two or three to establish a compliance schedule.
    We do not agree. The field management plan defined in the proposed 
AD is based on a risk analysis performed by Pratt &Whitney, which we 
reviewed and concluded is adequate. Further, additional field data 
received to-date has not indicated any increased risk, or that a more 
restrictive field plan is required. We did not change the AD.

Proposed OCI Procedure Should Be Revised

    The NTSB states that the proposed OCI procedure should be revised 
to also require that the blade slots be measured using a coordinate 
measuring machine (CMM) or another dimensional inspection device 
capable of measuring deviations in the center of the blade slots. The 
OCI procedure is limited to only measure the blade slot profile on the 
forward and aft ends of the blade slot. The current procedure does not 
measure the center portion of the blade slot.
    We partially agree. We agree that the current OCI procedure is 
limited such that it cannot measure the center portion of the blade 
slot. However, we disagree that the OCI procedure is not an acceptable 
inspection method to identify non-conforming hubs. We verified that the 
OCI procedure can identify HPT 2nd stage hubs with non-conforming blade 
retention slots. We established limits for OCI that ensured that no 
parts with non-conformances similar to the event hub would be released 
into service. We continue to work with Pratt & Whitney to identify 
other improved inspection methods that can be used as an alternate to 
OCI. We did not change the AD.

AD Compliance Should Also Include Inspection of the HPT 2nd Stage Blade 
Root Serrations for Uneven Contact Wear

    The NTSB states that the AD compliance should also include 
inspection of the HPT 2nd stage blade root serrations for uneven 
contact wear, as defined in the PW2000 Engine Manual, Task 72-52-17-
200-014, Inspection/Check 14. The AD should also specify an action to 
take with the HPT 2nd stage hubs if any HPT 2nd stage blades are 
detected with uneven wear. The HPT 2nd stage blades removed from the 
incident engine showed evidence of uneven contact wear on the blade 
root serrations. The AD should therefore also include inspection of the 
HPT 2nd stage blades and include an action to take with the hub if 
blades are detected to have root serrations with uneven wear.
    We do not agree. Inspection of the HPT 2nd stage blade root 
serrations was

[[Page 22428]]

incorporated in the PW2000 Engine Manual to address a non-conformance 
issue for the blades and is performed during normal inspection. All 
blades that are identified with uneven wear on the root serrations are 
rejected and removed from service. The cause of failure of the incident 
engine was due to a nonconformance of the HPT 2nd stage hub blade 
retention slots. All HPT 2nd stage hubs that have previously been 
exposed to Pratt & Whitney cleaning procedure SPOP 10 or SPOP 9 or 
equivalent procedure will require OCI per the AD. All non-conforming 
hubs will be identified by OCI and removed from service. We did not 
change the AD.

AD Should Mandate That All of the HPT 2nd Stage Hub Blade Slots Be 
Inspected Using OCI

    The NTSB states that the AD should mandate that all of the HPT 2nd 
stage hub blade slots be inspected using OCI. The current procedure 
only requires that every fourth blade retaining slot in the hub be 
inspected. The incident engine had cracks in several adjacent blade 
retaining lugs that resulted in the simultaneous release of multiple 
blades that exceeded the turbine case's containment capability. If only 
every fourth slot in the hub is inspected, then two adjacent 
nonconforming blade slots could slip through the inspection and result 
in an uncontained engine failure.
    We do not agree. Inspecting every fourth blade retaining slot will 
identify all non-conforming hubs. HPT 2nd stage hubs that are 
aggressively cleaned using a grit blast procedure will typically have a 
high number of non-conforming slots. Field inspection data to-date 
indicates that this assumption currently remains valid. We did not 
change the AD.

Conclusion

    We have carefully 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 have determined that these changes will neither increase the 
economic burden on any operator nor increase the scope of the AD.

Costs of Compliance

    We estimate that this AD will affect 762 engines installed on 
airplanes of U.S. registry. We also estimate that it will take about 50 
work-hours per engine to perform the actions, and that the average 
labor rate is $80 per work-hour. No parts are required. Based on these 
figures, we estimate the total cost of the AD to U.S. operators to be 
$3,048,000.

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 have 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 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); 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 summary of the costs to comply with this AD and 
placed it in the AD Docket. You may get a copy of this summary at the 
address listed under ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

0
Accordingly, under the authority delegated to me by the Administrator, 
the Federal Aviation Administration 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:

2009-10-08 Pratt & Whitney: Amendment 39-15903. Docket No. FAA-2008-
1131; Directorate Identifier 2008-NE-37-AD.

Effective Date

    (a) This airworthiness directive (AD) becomes effective June 17, 
2009.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Pratt & Whitney models PW2037, PW2037(M), 
and PW2040 turbofan engines with high-pressure turbine (HPT) 2nd 
stage hubs that have previously been exposed to Pratt & Whitney 
cleaning procedure SPOP 10 or SPOP 9 or equivalent procedure. These 
engines are installed on, but not limited to, Boeing 757-200 and 
757-300 airplanes.

Unsafe Condition

    (d) This AD results from an uncontained release of HPT 2nd stage 
blades and blade retention lugs. We are issuing this AD to remove 
nonconforming HPT 2nd stage hubs, which could result in an 
uncontained release of turbine blades and blade retention lugs, and 
damage to the airplane.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed at the next HPT overhaul, unless the actions have 
already been done.

Onetime Optical Comparator Inspection (OCI) of HPT 2nd Stage Hubs

    (f) Perform a onetime optical comparator inspection of the HPT 
2nd stage hubs after a fluorescent penetrant inspection and all shop 
cleaning processes have been completed. Pratt & Whitney Alert 
Service Bulletin No. PW2000 A72-734, dated November 3, 2008, 
contains information about the optical comparator inspection.
    (g) Remove from service any hubs that fail the optical 
comparator inspection.

Definition

    (h) This AD defines an HPT overhaul as when the HPT is at its 
piece-part level.

Alternative Methods of Compliance

    (i) The Manager, Engine Certification Office, has the authority 
to approve alternative methods of compliance for this AD if 
requested using the procedures found in 14 CFR 39.19.

Related Information

    (j) Contact Mark Riley, Aerospace Engineer, Engine Certification 
Office, FAA, Engine and Propeller Directorate, 12 New England 
Executive Park, Burlington, MA 01803; e-mail: mark.riley@faa.gov; 
telephone (781) 238-7758, fax (781) 238-7199, for more information 
about this AD.
    (k) Pratt & Whitney Alert Service Bulletin No. PW2000 A72-734, 
dated November 3, 2008, contains information about the optical 
comparator inspection.

[[Page 22429]]

Material Incorporated by Reference

    (l) None.

    Issued in Burlington, Massachusetts, on May 4, 2009.
Peter A. White,
Assistant Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. E9-10953 Filed 5-12-09; 8:45 am]

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