2010-32156. Airworthiness Directives; General Electric Company GE90-76B; GE90-77B; GE90-85B; GE90-90B; and GE90-94B Turbofan Engines

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD would require initial and repetitive fluorescent penetrant inspections (FPIs) and eddy current inspections (ECIs) of the high-pressure compressor rotor (HPCR) 8-10 stage spool, part numbers (P/Ns) 1844M90G01 and 1844M90G02, for cracks between the 9-10 stages, at each piece-part exposure. This proposed AD was prompted by cracks discovered on one HPCR 8-10 spool between the 9-10 stages in the weld joint. We are proposing this AD to prevent failure of the HPCR 8-10 stage spool, uncontained engine failure, and damage to the airplane.

DATES:

We must receive comments on this proposed AD by February 7, 2011.

ADDRESSES:

You may send comments by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: [phone].
• 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.

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: [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Jason Yang, Aerospace Engineer, Engine Certification Office, FAA, 12 New England Executive Park, Burlington, MA 01803; phone: [phone]; fax: [phone]; e-mail: [e-mail].

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-2010-1024; Directorate Identifier 2010-NE-34-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

General Electric Company (GE) recently informed us of cracks discovered during a shop visit of a GE90-94B turbofan engine. The cracks were in the HPCR 8-10 stage spool weld joint between the 9-10 stages. These cracks can lead to failure of the HPCR 8-10 stage spool. GE informed us that the cracking is caused by defects during part manufacture, in the inertia weld process. This unsafe condition could also occur on GE90-76B; GE90-77B; GE90-85B; and GE90-90B turbofan engines, as they use the same design HPCR 8-10 stage spool. GE90 Engine Manual Chapter 5 requires mandatory inspections of the HPCR 8-10 stage spool, specifically, inspection of the weld joint between the 8-9 stages. Because of the cracking between the 9-10 stages in the weld joint, GE has updated Chapter 5 to include inspection of the weld joint between the 9-10 stages. They also changed the inertia weld process during manufacture. These cracks, if not corrected, could result in failure of the HPCR 8-10 stage spool, 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 design.

Proposed AD Requirements

This proposed AD would require initial and repetitive FPIs and ECIs of the HPCR 8-10 stage spool, P/Ns 1844M90G01 and 1844M90G02 for cracks, at each piece-part exposure.

Costs of Compliance

We estimate that this proposed AD would affect 33 GE90-76B; GE90-77B; GE90-85B; GE90-90B; and GE90-94B engines installed on airplanes of U.S. registry. We also estimate that it would take about 2 work-hours per engine to perform one proposed inspection, and that the average labor rate is $85 per work-hour. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $5,610 for one inspection cycle.

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
• 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.

§ 39.13

[Amended]

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

General Electric Company: Docket No. FAA-2010-1024; Directorate Identifier 2010-NE-34-AD.

Comments Due Date

(a) We must receive comments by February 7, 2011.

Affected ADs

(b) None.

Applicability

(c) This AD applies to General Electric Company GE90-76B; GE90-77B; GE90-85B; GE90-90B; and GE90-94B turbofan engines with a high-pressure compressor rotor (HPCR) 8-10 stage spool, part number (P/N) 1844M90G01 or 1844M90G02, installed. These engines are installed on but not limited to Boeing 777 series airplanes.

Unsafe Condition

(d) This AD was prompted by cracks discovered on one HPCR 8-10 spool between the 9-10 stages in the weld joint. We are issuing this AD to prevent failure of the HPCR 8-10 stage spool, uncontained engine failure, and damage to the airplane.

Compliance

(e) Comply with this AD within the compliance times specified, unless already done.

Inspections of the HPCR 8-10 Stage Spool

(f) At the next piece-part exposure after the effective date of this AD of the HPCR 8-10 stage spool, perform a fluorescent penetrant inspection (FPI) and eddy current inspection (ECI) of the weld joint between the 9-10 stages of the HPCR 8-10 stage spool for cracks.

(g) Thereafter, perform repetitive FPIs and ECIs of the weld joint between the 9-10 stages of the HPCR 8-10 stage spool for cracks at every piece-part exposure of the HPCR 8-10 stage spool.

(h) Remove from service any HPCR 8-10 stage spool found cracked.

(i) Guidance on performing the FPI can be found in GE90 (GEK100700) Engine Manual, Chapter 72-31-08, Inspection 001.

(j) Guidance on performing the ECI can be found in GE90 (GEK100700) Engine Manual, Chapter 72-31-08, Special Procedures 001.

Definition

(k) For the purpose of this AD, piece-part exposure is when the HPCR stage 8-10 spool is completely disassembled using the disassembly instructions in the GE90 Engine Manual.

Alternative Methods of Compliance (AMOCs)

(l) The Manager, Engine Certification Office, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19.

Related Information

(m) For more information about this AD, contact Jason Yang, Aerospace Engineer, Engine Certification Office, FAA, 12 New England Executive Park, Burlington, MA 01803; phone: [phone]; fax: [phone]; e-mail: [e-mail].

(n) For service information identified in this AD, contact General Electric Company, GE—Aviation, Room 285, 1 Neumann Way, Cincinnati, OH 45215, telephone [phone]; fax [phone]; e-mail: [e-mail]. For information on the availability of this material at the FAA, call 781-238-7125.

Issued in Burlington Massachusetts, on December 10, 2010.

Peter A. White,

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