AD 99-20-03 ACTIVE

This amendment adopts a new airworthiness directive (AD), applicable to Pratt & Whitney (PW) PW2000 series turbofan engines, that requires initial and repetitive inspections of certain High Pressure Turbine (HPT) stage 1 and stage 2 disks utilizing an improved ultrasonic inspection method performed at an approved facility when the disk is exposed during a shop visit, and if a crack indicating a subsurface anomaly is found, removal from service and replacement with a serviceable part. This amendment is prompted by the results of a stage 1 HPT disk fracture investigation, which has identified a population of HPT stage 1 and 2 disks that may have subsurface anomalies formed during a forging process. The actions specified by this AD are intended to prevent HPT disk fracture, which could result in an uncontained engine failure, and damage to the aircraft.

Final rule.

99-20-03 PRATT & WHITNEY: Amendment 39-11333. Docket 99-NE-02-AD. Issued September 16, 1999.
Applicability: Pratt & Whitney PW2037, PW2040, PW2037M, PW2240, and PW2337 series turbofan engines, installed on but not limited to Boeing 757 and Ilyushin IL-96T series airplanes.
Note 1: This airworthiness directive (AD) applies to each engine identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For engines that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should includespecific proposed actions to address it.
Compliance: Required as indicated, unless accomplished previously.
To prevent high pressure turbine (HPT) disk fracture, which could result in an uncontained engine failure and damage to the aircraft, accomplish the following:
(a) For engines with a HPT stage 1 or stage 2 disk installed that has a serial number listed in the Accomplishment Instructions section of PW Service Bulletin (SB) PW2000 72-628, dated January 4, 1999, perform initial and repetitive ultrasonic inspections in accordance with PW SB PW2000 72-628, dated January 4, 1999 at each separation of the HPT disk from the HPT module after the effective date of this AD. The disk must be sent to an approved facility listed in the Vendor Services or Special Components/Materials section of PW SB PW2000 72-628, dated January 4, 1999, for ultrasonic inspection.
(b) Remove from service those HPT disks found with a crack indicating a subsurface anomaly and replace with a serviceable part.
(c) For engines that do not have a HPT stage 1 or Stage 2 disk installed that has a serial number listed in the Accomplishment Instructions section of PW SB PW2000 72-628, dated January 4, 1999, no inspections are required.
(d) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Engine Certification Office. Operators shall submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office.
Note 2: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office.
(e) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the aircraft to a location where the requirements of this AD can be accomplished.
(f) The actions required by this AD shall be done in accordance with the following PW SB:

Document No
Pages
Date
PW2000 72-628
1-13
January 4, 1999
Total Pages: 13.

This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone (860) 565-8770, fax (860) 565-4503. Copies may be inspected at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.
(g) This amendment becomes effective on November 23, 1999.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to Pratt & Whitney (PW) PW2037, PW2040, PW2037M, PW2240, and PW2337 series turbofan engines was published in the Federal Register on March 23, 1999 (64 FR 13932). That action proposed to require initial and repetitive inspections of certain stage 1 and stage 2 high pressure turbine (HPT) disks using an improved ultrasonic method whenever the disk is exposed during a shop visit. The inspection must be performed at an approved facility listed in PW Service Bulletin (SB) PW2000 72-628, dated January 4, 1999. If a crack indicating a subsurface anomaly is found, the disk must be removed from service and replaced with a serviceable part.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
Two commenters notethat the proposed rule is more restrictive than the PW SB, which addresses the same issue. The PW SB is a Category 6 SB ( perform upon piece-part exposure). The proposed rule requires inspection upon disk separation from the module. One of the commenters estimates that 25% of the HPT modules entering its shop that get separated do not have the disks debladed. That commenter does not perform a "heavy" maintenance on HPT's upon each exposure. Approximately 25% of its HPT shop visits are for repair only. Due to the additional labor cost to perform the increased requirements of the proposed rule and the potential for increased scrap, that commenter suggests that the rule be modified to the requirements of the PW SB.
The FAA does not concur. The change from the PW SB compliance requirements to the requirements of the proposed rule were intentional, and were predicated by the fact that the risk factor for this problem was relatively high at 0.485 disk fractures predicted over the remaining life of the program. The affected engines generally contain two suspect disks each. The FAA therefore determined to increase the compliance requirements over the PW SB. Furthermore, the FAA has determined that only four additional engines would likely require inspection upon disk separation from the module as opposed to the SB's compliance time of piece-part exposure. The impact of this change is predicted to be a small burden economically on operators, and increases operational safety.
One commenter expresses concern that only one inspection source is available for the requirements of the proposed rule, and that this one source would limit shop timing and capacity. The commenter recommends that the issuance of the AD be no sooner than 90 days after the end of the comment period or July 20, 1999. The FAA does not concur. Discussions with PW indicate that shop capacity and timing will not be a factor with the vendors and the timing in the proposed rule. The manufacturerbelieves that adequate shop capacity to handle the inspection requirements exists now. A second inspection source is being developed at this time, however, which should ease shop capacity concerns.
One commenter states that the impact to their operation will be minor. They have 20 disks affected by the proposed rule, and most are approaching their life limits and will be scrapped at the next shop visit. The commenter has no objections to the rule as proposed.
One commenter concurs with the rule as proposed.
The AD was edited to clarify the shipping requirements discussed in the financial assessment in the compliance section. Due to the complexity of the ultrasonic inspection, the compliance plan requires that the disks be inspected at an approved facility to ensure that the inspections meet the intent. As the inspection requires using a complex process and unique equipment, the AD requires that only approved facilities perform the inspection. This is not a change from the original proposed rule, but paragraph (a) of the compliance section has been edited to make this requirement more clear.
In addition, to simplify the AD, the definition of HPT disk piece part accessibility of paragraph (c) was deleted and incorporated into paragraph (a).
After careful review of the available data, including the comment noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.
There are approximately 332 affected disks installed in engines in the worldwide fleet. The FAA estimates that 166 engines installed on aircraft of US registry would be affected by this proposed AD, that the shipping cost per disk to the facility which will inspect the disk and its return will be approximately $210 per disk, that no engines will require an unplannedHPT module disassembly/assembly, that the inspection will take approximately 12 work hours per disk to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Some disks will require multiple inspections during their service life. Based on these figures, the total cost impact of the AD on US operators is estimated to be $450,000. The manufacturer has advised the FAA that the all costs relative to the inspection will be reimbursed to the operator.
The regulations adopted herein will not have substantial direct effects 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. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this action (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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

The service information referenced in this AD may be obtained from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone (860) 565-8770, fax (860) 565-4503. This information may be examined at the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.

Peter White, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7128, fax (781) 238-7199.