2010-17145. Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Pratt & Whitney PW4000 series turbofan engines. This proposed AD would require initial and repetitive borescope inspections (BSI) or fluorescent penetrant inspections (FPI) for cracks in the anti-vortex tube (AVT) shelf slots on the 10th stage disk of the high-pressure compressor (HPC) drum rotor disk assembly. This proposed AD results from 47 reports received since 2007 of HPC 10th stage disks found cracked in the AVT shelf slots during shop visit inspections. We are proposing this AD to prevent failure of the HPC 10th stage disk, uncontained engine failure, and damage to the airplane.

DATES:

We must receive any comments on this proposed AD by September 13, 2010.

ADDRESSES:

Use one of the following addresses to comment on this proposed AD.

• Federal eRulemaking Portal: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility, U.S. Department of Transportation, 1200 New Jersey Avenue, SE., West Building Ground Floor, Room W12-140, Washington, DC 20590-0001.
• Hand Delivery: Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.
• Fax: [phone].

Contact Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone [phone]; fax [phone], for a copy of the service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT:

James Gray, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; e-mail: [e-mail]; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send us any written relevant data, views, or arguments regarding this proposal. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2010-0596; Directorate Identifier 2010-NE-22-AD” in the subject line of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light 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 with FAA personnel concerning this proposed AD. Using the search function of the Web site, anyone can find and read the comments in any of our dockets, including, if provided, the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78).

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 proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Operations office (telephone [phone]) is the same as the Mail address provided in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

Discussion

Since 2007, we have received 47 reports of HPC 10th stage disks found cracked in the AVT shelf slots during shop visit inspections. Investigation has revealed the root cause of the cracks to be the slot configuration in the 9th stage compressor stator inner shroud. The number of slots matches the number of anti-vortex tubes and causes an aerodynamic interaction during engine operation. This interaction results in high-cycle-fatigue cracks in the AVT shelf slots on the 10th stage disk of the HPC drum rotor disk assembly. This condition, if not corrected, could result in failure of the HPC 10th stage disk, uncontained engine failure, and damage to the airplane.

Relevant Service Information

We have reviewed and approved the technical contents of Pratt & Whitney Service Bulletin (SB) No. PW4ENG 72-799, dated January 22, 2010, and SB No. PW4G-100-72-226, dated April 22, 2010, that describe procedures for inspecting for cracks in the AVT shelf slots on the 10th stage disk of the HPC drum rotor disk assembly.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other products of this same type design. We are proposing this AD, which would require initial and repetitive BSI or FPI for cracks in the AVT shelf on the 10th stage disk of the HPC drum rotor disk assembly. The proposed AD would require you to use the service information described previously to perform these actions.

Interim Actions

These actions are interim actions and we may take further rulemaking actions in the future.

Costs of Compliance

We estimate that this proposed AD would affect 869 engines installed on airplanes of U.S. registry. We also estimate that it would take about one work-hour per engine to perform a proposed inspection, and that the average labor rate is $85 per work-hour. Required parts would cost about $303,010 per HPC drum rotor disk assembly. About 61 HPC drum rotor disk assemblies would need replacement due to cracks. Based on these figures, we estimate the cost of the AD on U.S. operators to be $18,557,475.

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 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 that the proposed AD:

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); and

3. Would 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 regulatory evaluation of the estimated costs to comply with this proposed AD. 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
• Incorporation by reference
• Safety

The Proposed Amendment

Under the authority delegated to me by the Administrator, the Federal Aviation Administration 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.

§ 39.13

[Amended]

2. The FAA amends § 39.13 by adding the following new airworthiness directive:

Pratt & Whitney: Docket No. FAA-2010-0596; Directorate Identifier 2010-NE-22-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this airworthiness directive (AD) action by September 13, 2010.

Affected ADs

(b) None.

Applicability

(c) This AD applies to the following Pratt & Whitney turbofan engines with a ring case configuration rear high-pressure compressor (HPC) installed. These engines are installed on, but not limited to, Boeing 747-200, 767-200/-300, and MD-11 airplanes, and Airbus A300-600, A310-300, A330-300, and A330-200 airplanes.

PW4000-94” Engines

(1) PW4000-94” series engine models PW4050, PW4052, PW4056, PW4060, PW4060A, PW4060C, PW4062, PW4062A, PW4152, PW4156, PW4156A, PW4158, PW4160, PW4460, PW4462, and PW4650, including all models with a dash number suffix.

PW4000-100” Engines

(2) PW4000-100” series engine models PW4168A-1D and PW4170 with serial numbers P735001 through P735039; and

(3) All engines converted to PW4164-1D, PW4168-1D, PW4168A-1D, or PW4170 model engines.

Unsafe Condition

(d) This AD results from 47 reports received since 2007 of HPC 10th stage disks found cracked in the AVT shelf slots during shop visit inspections. We are issuing this AD to prevent failure of the HPC 10th stage disk, uncontained engine failure, and damage to the airplane.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified unless the actions have already been done.

Initial Inspection of the AVT Shelf Slots

(f) For engines listed in paragraphs (c)(1) and (c)(3) of this AD, do the following:

(1) Remove the low-pressure turbine (LPT) shaft and borescope-inspect (BSI) for cracks in the AVT shelf slots on the 10th stage disk of the HPC drum rotor disk assembly; or

(2) Remove the HPC drum rotor disk assembly and fluorescent-penetrant inspect (FPI) for cracks in the AVT shelf slots on the 10th stage disk of the HPC drum rotor disk assembly.

(3) Perform the inspection:

(i) Within 7,200 cycles-in-service (CIS) since incorporation of any of the following Pratt & Whitney Service Bulletins: (SB) No. PW4ENG 72-755, SB No. PW4ENG 72-756, SB No. PW4ENG 72-757, SB No. PW4ENG 72-759, or SB No. PW4G-100-72-220; or

(ii) Within 1,000 CIS after the effective date of this AD, whichever occurs later.

(4) If a crack is found, remove the HPC drum rotor disk assembly from service.

(g) For engines listed in paragraph (c)(2) of this AD, do the following:

(1) Remove the LPT shaft and BSI for cracks in the AVT shelf slots on the 10th stage disk of the HPC drum rotor disk assembly; or

(2) Remove the HPC drum rotor disk assembly and FPI for cracks in the AVT shelf slots on the 10th stage disk of the HPC drum rotor disk assembly.

(3) Perform the inspection:

(i) Within 7,200 cycles-since-new; or

(ii) Within 1,000 CIS after the effective date of this AD, whichever occurs later.

(4) If a crack is found, remove the HPC drum rotor disk assembly from service.

Repetitive Inspections of the AVT Shelf Slots

(h) Thereafter, perform a BSI or FPI for cracks in the AVT shelf slots on the 10th stage HPC disk of the HPC drum rotor disk assembly within every 7,200 cycles-since-last-inspection.

(i) If a crack is found, remove the HPC drum rotor disk assembly from service.

Relevant Service Bulletins

(j) Use paragraphs 3.A through 3.H of the Accomplishment Instructions of Pratt & Whitney SB No. PW4ENG 72-799, dated January 22, 2010, to perform the BSIs for engines listed in paragraph (c)(1) of this AD.

(k) Use paragraphs 3.A through 3.H of the Accomplishment Instructions of Pratt & Whitney SB No. PW4G-100-72-226, dated April 22, 2010, to perform the BSIs for engines listed in paragraphs (c)(2) and (c)(3) of this AD.

Alternative Methods of Compliance

(l) 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.

Interim Actions

(m) These actions are interim actions and we may take further rulemaking actions in the future.

Related Information

(n) Contact James Gray, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; e-mail: [e-mail]; telephone [phone]; fax [phone], for more information about this AD.

(o) Pratt & Whitney SB No. PW4ENG 72-799, dated January 22, 2010, and SB No. PW4G-100-72-226, dated April 22, 2010, pertain to the subject of this AD. Contact Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone [phone]; fax [phone], for a copy of this service information.

Issued in Burlington, Massachusetts, on July 8, 2010.

Peter A. White,

Assistant Manager, Engine and Propeller Directorate, Aircraft Certification Service.