E8-16884. Airworthiness Directives; General Electric Company CF34-1A, -3A, -3A1, -3A2, -3B, and -3B1 Turbofan 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 General Electric Company (GE) CF34-1A, -3A, -3A1, -3A2, -3B, and -3B1 turbofan engines with high-pressure (HP) rotor 4-step air balance piston stationary seals (4-step seals), part numbers 4923T54G01, 6019T90G03, 6037T99G01, 6037T99G02, and 6037T99G03, installed. This proposed AD would require removing the 4-step seals and incorporating an 8-step seal at the next piece-part exposure. This proposed AD results from the investigation of an airplane accident. Both engines experienced high-altitude flameouts. Rotation of the HP rotors was not maintained during descent and the engines could not be restarted. We are proposing this AD to prevent the inability to restart both engines after flameout due to excessive friction of the 4-step seal, which could result in subsequent forced landing of the airplane.

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 General Electric Company via Lockheed Martin Technology Services, 10525 Chester Road, Suite C, Cincinnati, Ohio 45215, telephone [phone], fax [phone].

FOR FURTHER INFORMATION CONTACT:

Kenneth Steeves, Aerospace Engineer, Engine Certification Office, Engine and Propeller Directorate, FAA, 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-2007-0419; Directorate Identifier 2007-NE-52-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. This includes, 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

In October 2004, a Bombardier CL600-2B19 Regional Jet airplane experienced high-altitude flameouts of both engines while on a ferry flight. After flameout, when the airplane was descending, sufficient airspeed was not maintained to ensure rotation of the HP rotors and they stopped rotating. During repeated unsuccessful engine restart attempts on both engines, the HP rotors did not obtain sufficient rotational speeds for the engines to restart. The airplane eventually crashed while attempting to glide to an airport, and the crew was fatally injured. When these engines experience a high-altitude flameout, the engines are immediately subjected to rapid cooling due to the extremely cold air flowing around and through them. The static seal parts cool more rapidly than the rotors, and shrink until they contact the rotating seal surfaces. If the speed of the airplane is not sufficient to maintain windmill rotation of the HP rotors, the rotors will stop rotating and could lock if sufficient friction develops between the rotating and static air balance piston seal surfaces. This condition, if not corrected, could result in the inability to restart the engines and the subsequent forced landing of the airplane. Investigation by GE determined that under certain conditions, the existing 4-step seals used in CF34-1A, -3A, -3A1, -3A2, -3B, and -3B1 turbofan engines can come into contact with the rotating seal surfaces and create friction. In a worse case, this friction could cause locking of the HP rotors, called “rotor lock”. GE is introducing 8-step seals for all CF34-1A, -3A, -3A1, -3A2, -3B, and -3B1 turbofan engines. The 8-step seals will reduce potential drag in the rotor system and enhance the windmilling capabilities of HP rotors. This will ultimately reduce the possibility of the HP rotor locking after a high-altitude flameout when HP rotor rotation is not maintained during descent.

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 removing the 4-step seal at next piece-part exposure and incorporating an 8-step seal, either by modifying the existing 4-step seal to an 8-step seal or by replacing it with an 8-step seal.

Costs of Compliance

We estimate that this proposed AD would affect 2,722 CF34-1A, -3A, -3A1, -3A2, -3B, and -3B1 turbofan engines installed on airplanes of U.S. registry. We also estimate that this proposed AD will not impose any additional labor or material costs as most of the seals will require replacement when they are removed from the engine during scheduled engine overhaul. For those few seals that can be reworked, we estimate that it would take about 5 work-hours per engine to perform the proposed seal modification, and that the average labor rate is $80 per work-hour. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $108,800.

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 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: Docket No. FAA-2007-0419; Directorate Identifier 2007-NE-52-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 General Electric Company (GE) CF34-1A, -3A, -3A1, -3A2, -3B, and -3B1 turbofan engines, with high-pressure (HP) rotor 4-step air balance piston stationary seals (4-step seals), part numbers (P/Ns) 4923T54G01, 6019T90G03, 6037T99G01, 6037T99G02, and 6037T99G03, installed. These engines are installed on, but not limited to, Bombardier, Inc. airplane models CL-600-2A12, -2B16, and -2B19.

Unsafe Condition

(d) This AD results from the investigation of an airplane accident. Both engines experienced high-altitude flameouts. Rotation of the HP rotors was not maintained during descent and the engines could not be restarted. We are issuing this AD to prevent the inability to restart both engines after flameout due to excessive friction of the 4-step seal, which could result in subsequent forced landing of the airplane.

Compliance

(e) You are responsible for having the actions required by this AD performed at the next piece-part exposure after the effective date of this AD, unless the actions have already been done.

(f) Remove the 4-step seals, P/Ns 4923T54G01, 6019T90G03, 6037T99G01, 6037T99G02, and 6037T99G03.

(g) Incorporate an 8-step seal, either by modifying the existing 4-step seal to an 8-step seal, or by replacing it with an 8-step seal.

(h) Information on modifying the seal and part number configuration charts, can be found in GE Service Bulletin (SB) No. CF34-AL S/B 72-0238, dated July 27, 2007 (CL-600-2B19), and SB No. CF34-BJ S/B 72-0217, dated July 27, 2007 (CL-600-2A12 and CL-600-2B16).

Definition

(i) For the purposes of this AD, piece-part exposure means when the 4-step seal is removed from the combustion module in accordance with the disassembly instructions in the engine manufacturer's, or other FAA-approved engine manual.

Alternative Methods of Compliance

(j) 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

(k) Contact Kenneth Steeves, Aerospace Engineer, Engine Certification Office, Engine and Propeller Directorate, FAA, 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 16, 2008.

Marc Bouthillier,

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