2011-10522. Airworthiness Directives; General Electric Company CT7-8, CT7-8A, CT7-8A1, CT7-8E, and CT7-8F5 Turboshaft 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 the installation of an accessory gearbox (AGB) axis-A oil slinger nut to the axis-A shaft assembly. This proposed AD was prompted by four reports of unrecoverable engine stalls, during hover in a left-roll attitude. We are proposing this AD to prevent an unrecoverable engine stall, leading to a helicopter forced landing or accident.

DATES:

We must receive comments on this proposed AD by June 16, 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.

For service information identified in this proposed AD, contact GE-Aviation, M/D Rm. 285, One Neumann Way, Cincinnati, OH 45215; telephone: [phone]; e-mail: [e-mail]. You may review copies of the referenced service information at the FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA. For information on the availability of this material at the FAA, call 781-238-7125.

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:

Walter Meibaum, Aerospace Engineer, Engine & Propeller Directorate, 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-2011-0392; Directorate Identifier 2011-NE-12-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

We received four reports of General Electric Company (GE) CT7-8 series turboshaft helicopter engines experiencing unrecoverable engine stalls, during hover in a left-roll attitude. Investigation revealed that during a prolonged left roll, excessive return oil from the AGB may return to the A-sump and exceed the sump's scavenging capability. The sump then floods, leading to over-heated oil, which preheats the air entering the engine's compressor. This preheated air causes inlet thermal distortion. This condition, if not corrected, could result in an unrecoverable engine stall, leading to a helicopter forced landing or accident.

Relevant Service Information

We reviewed GE Aircraft Engines CT7-8 Turboshaft Engine Service Bulletin (SB) No. CT7-8 S/B 72-0033, dated February 11, 2011. The SB describes procedures for installing the AGB axis-A oil slinger nut to the axis-A shaft assembly.

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 engines of the same type design.

Proposed AD Requirements

This proposed AD would require the installation of an AGB axis-A oil slinger nut to the axis-A shaft assembly.

Costs of Compliance

We estimate that this proposed AD would affect 80 engines installed on helicopters of U.S. registry. We also estimate that it would take about one work-hour per engine to perform the actions required by this proposed AD, and that the average labor rate is $85 per work-hour. Required parts would cost about $700 per engine. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $62,800.

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
• Incorporation by reference
• 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-2011-0392; Directorate Identifier 2011-NE-12-AD.

Comments Due Date

(a) We must receive comments by June 16, 2011.

Affected ADs

(b) None.

Applicability

(c) This AD applies to the following General Electric Company (GE) turboshaft engines:

(1) CT7-8, all engine serial numbers (S/Ns).

(2) CT7-8A, engine S/Ns 947565 and below.

(3) CT7-8A1, engine S/Ns 530017 and below.

(4) CT7-8E, engine S/Ns 953068 and below, and S/Ns 953070 and 953072.

(5) CT7-8F5, engine S/Ns 731005 and below, and S/Ns 731007, 731008, 817021, and 817022.

Unsafe Condition

(d) This AD was prompted by four reports of unrecoverable engine stalls, during hover in a left-roll attitude. We are issuing this AD to prevent an unrecoverable engine stall, leading to a helicopter forced landing or accident.

Compliance

(e) Comply with this AD at the next engine shop visit, the next 1,500-hour helicopter inspection, or before operation after next engine installation, whichever occurs first, unless already done.

Installation of Accessory Gearbox (AGB) Axis-A Oil Slinger Nut

(f) Install the AGB axis-A oil slinger nut to the axis-A shaft assembly. Use Accomplishment Instructions, paragraphs 3.A. through 3.C. of GE Aircraft Engines CT7-8 Turboshaft Engine Service Bulletin No. CT7-8 S/B 72-0033, dated February 11, 2011, to do the installation.

Alternative Methods of Compliance (AMOCs)

(g) 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

(h) For more information about this AD, contact Walter Meibaum, Aerospace Engineer, Engine & Propeller Directorate, FAA, 12 New England Executive Park, Burlington, MA 01803; phone: [phone]; fax: [phone]; e-mail: [e-mail].

(i) For service information identified in this AD, contact GE-Aviation, M/D Rm. 285, One Neumann Way, Cincinnati, OH 45215; telephone: [phone]; e-mail: [e-mail]. You may review copies of the referenced service information at the FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA. For information on the availability of this material at the FAA, call 781-238-7125.

Issued in Burlington, Massachusetts, on April 25, 2011.

Peter A. White,

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