E8-16883. Airworthiness Directives; General Electric Company (GE) CT58 Series Turboshaft Engines

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain GE CT58 series turboshaft engines. This proposed AD would require recalculating the lives of certain part numbered compressor spools using a new repetitive heavy lift (RHL) multiplying factor. This proposed AD results from reports of cracks originating from the inner faces of the locking screw holes in the compressor spool. We are proposing this AD to prevent cracks due to RHL missions. Cracks could result in an uncontained rotor burst and damage to, or loss of, the helicopter and serious injuries to any person onboard.

DATES:

We must receive any comments on this proposed AD by September 22, 2008.

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].

You can get the service information identified in this proposed AD from GE Aircraft Engines Customer Support Center, M/D 285, 1 Neumann Way, Evendale, OH 45215; telephone [phone]; fax [phone]; e-mail [e-mail].

FOR FURTHER INFORMATION CONTACT:

Christopher J. Richards, Aerospace Engineer, Engine Certification Office, FAA, Engine & 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-2008-0808; Directorate Identifier 2008-NE-18-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

We have received reports of nine compressor spools, with cracks originating from the inner faces of the locking screw holes in compressor spools used in RHL missions. We have not received any reports of in-flight events occurring because of the cracking. GE, the engine manufacturer, has developed a new RHL multiplying factor for use when calculating compressor spool lives on engines used for RHL missions. The new, larger multipliers will prevent the cracks from propagating to failure by causing the spools to meet their service life limits sooner, resulting in earlier removal from the engine. This condition, if not corrected, could result in an uncontained rotor burst and damage to, or loss of, the helicopter and serious injuries to any person onboard.

Relevant Service Information

We have reviewed and approved the technical contents of GE Alert Service Bulletin (ASB) CT58 S/B 72-A0162, Revision 12, dated April 17, 2008, that describes procedures for calculating the compressor spool cycles using RHL mission multipliers.

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 recalculating the cycles on certain compressor spools using new RHL mission multipliers within 30 days after the effective date of the proposed AD.

Costs of Compliance

We estimate that this proposed AD would affect 89 engines installed on helicopters of U.S. registry. We also estimate that it would take about 0.5 work-hour per engine to perform the proposed actions, and that the average labor rate is $80 per work-hour. Prorated life lost for the compressor spools would cost about $16,972 per engine. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $1,514,068.

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
• 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:

General Electric Company (GE): Docket No. FAA-2008-0808; Directorate Identifier 2008-NE-18-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this airworthiness directive (AD) action by September 22, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to GE CT58 series turboshaft engines with a compressor spool, part number (P/N) 5920T82G07, 6010T57G07, or 6010T57G08, installed. These engines are installed on, but not limited to, Sikorsky S-61A, S-61L, S-61N, S-61R, S-62, and Columbia 107-II helicopters.

Unsafe Condition

(d) This AD results from reports of cracks originating from the inner faces of the locking screw holes in the compressor spool. We are issuing this AD to prevent cracks due to repetitive heavy lift (RHL) missions. Cracks could result in an uncontained rotor burst and damage to, or loss of, the helicopter and serious injuries to any person onboard.

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.

Recalculating Compressor Spool Cycles

(f) Within 30 days after the effective date of this AD, recalculate the life of compressor spools, P/N 5920T82G07, 6010T57G07, or 6010T57G08, using an RHL mission multiplying factor of both 3.7 cycles per hour and 6.0 cycles per hour. GE Alert Service Bulletin CT58 S/B 72-A0162, Revision 12, dated April 17, 2008, contains information on calculating life cycles for the compressor spools.

Removing Compressor Spools Based on the New Recalculated Cycles

(g) Before January 1, 2010, remove the compressor spools, P/N 5920T82G07, 6010T57G07, or 6010T57G08, at the earlier of when:

(1) The compressor spool reaches its part life limit as calculated using an RHL multiplying factor of 3.7, or

(2) You can see the spool at shop visit after it has reached its part life limit using an RHL multiplying factor of 6.0.

(h) On January 1, 2010 and thereafter, remove the engine before the compressor spool exceeds its part life limit as calculated using an RHL multiplying factor of 6.0.

(i) As of January 1, 2010, don't use an RHL multiplying factor of 3.7 to calculate the life of the compressor spool.

Installation Prohibition

(j) After the effective date of this AD, don't install any engine that has a compressor spool installed that meets or exceeds the life limits as calculated in paragraph (g)(1) through (g)(2) or (h) of this AD.

Alternative Methods of Compliance

(k) 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

(l) GE Alert Service Bulletin CT58 S/B 72-A0162, Revision 12, dated April 17, 2008, pertains to the subject of this AD.

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

Issued in Burlington, Massachusetts, on July 17, 2008.

Marc Bouthillier,

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