E7-13835. Airworthiness Directives; General Electric Company (GE) CF6-80C2D1F 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 GE CF6-80C2D1F turbofan engines, installed on McDonnell Douglas Corporation MD-11 series airplanes. This proposed AD would require removing previous software versions from the engine electronic control unit (ECU). Engines with new version software will have increased margin to flameout. This proposed AD results from reports of engine flameout events during flight, including reports of events where all engines simultaneously experienced a flameout or other adverse operation. Although the root cause investigation is not yet complete, we believe that exposure to ice crystals during flight is associated with these flameout events. We are proposing this AD to minimize the potential of an all-engine flameout event caused by ice accretion and shedding during flight.

DATES:

We must receive any comments on this proposed AD by September 17, 2007.

ADDRESSES:

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

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• 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.
• 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:

John Golinski, 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-2007-28319; Directorate Identifier 2007-NE-27-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://dms.dot.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 DOT Web site, anyone can find and read the comments in any of our dockets, including 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) or you may visit http://dms.dot.gov.

Examining the AD Docket

You may examine the AD docket on the Internet at http://dms.dot.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

GE CF6-80C2 and CF6-80E1 series turbofan engines continue to experience flameout events that are due to ice accretion and shedding into the engine during flight. Although the investigation is not yet complete, we believe that the ice accretion is caused by exposure to ice crystals during flight. Industry reports 35 airplane flameout events, including reports of multi-engine events where all engines on the airplane simultaneously experienced a flameout. Some of these events had high pressure compressor blade damage that may have been caused by impact with shedding ice. In all events, the engines restarted and continued to operate normally for the remainder of the flight.

This proposed AD addresses only the CF6-80C2D1F turbofan engines, installed on McDonnell Douglas Corporation MD-11 series airplanes. We believe this model of CF6-80C2 engine is susceptible to flameouts caused by ice accretion and shedding into the engine during flight. Similar AD actions for other CF-80C2 and CF6-80E1 series engines may be forthcoming.

We view an all-engine flameout event as an unsafe condition particularly for low-altitude events, or other factors that might result in the inability to restart the engines and regain control of the airplane. Since some aspects of this problem are not completely understood, this proposed AD is considered an interim action due to GE's on-going investigation. Future AD action might become necessary based on the results of the investigation and field experience. This condition of insufficient margin to engine flameout due to ice accretion and shedding during flight, if not addressed, could result in an all-engine flameout event during flight.

Relevant Service Information

We have reviewed and approved the technical contents of GE Service Bulletin (SB) No. CF6-80C2 S/B 73-0351, dated April 11, 2007. That SB describes procedures for removing certain software versions from the ECU, and installing a software version that is FAA-approved. The new FAA-approved software version described in the SB modifies the variable bleed valve schedule, which will provide an increased margin to flameout. This increased margin is expected to reduce the rate of flameout occurrences due to ice accretion and shedding during flight.

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 certain software versions from the engine ECU.

Interim Action

These actions are interim actions due to the on-going investigation. We may take further rulemaking actions in the future, based on the results of the investigation and field experience.

Costs of Compliance

We estimate that this proposed AD would affect 175 CF6-80C2D1F turbofan engines installed on McDonnell Douglas Corporation MD-11 series airplanes of U.S. registry. We estimate it would take about 3 work-hours per ECU to perform the proposed actions if done at ECU shop visit, and 6 work-hours per ECU if done at engine shop visit. We estimate that 50% of the ECUs would be worked at ECU shop visit and the remaining 50% worked at engine shop visit. The average labor rate is $80 per work-hour. Based on these figures, we estimate the cost to U.S. operators to be $63,120. Our cost estimate is exclusive of warranty coverage.

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-2007-28319; Directorate Identifier 2007-NE-27-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this airworthiness directive (AD) action by September 17, 2007.

Affected ADs

(b) None.

Applicability

(c) This AD applies to General Electric Company (GE) CF6-80C2D1F turbofan engines, installed on McDonnell Douglas Corporation MD-11 series airplanes.

Unsafe Condition

(d) This AD results from reports of engine flameout events during flight, including reports of events where all engines simultaneously experienced a flameout or other adverse operation. We are issuing this AD to minimize the potential of an all-engine flameout event, due to ice accretion and shedding during flight. Exposure to ice crystals during flight is believed to be associated with these flameout events.

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.

Interim Action

(f) These actions are interim actions due to the on-going investigation, and we may take further rulemaking actions in the future based on the results of the investigation and field experience.

Engine Electronic Control Unit (ECU) Software Removal

(g) At the next shop visit of the engine or of the ECU, whichever occurs first, and not to exceed 60 months from the effective date of this AD, remove the following software versions from the ECUs:

Table 1.—Removal of ECU Software Versions

Software version	Installed in ECU part No.
(1) 8.5.A	1851M51P01, 1851M51P02, 1851M52P01, 1851M52P02, 1851M53P01, 1851M53P02
(2) 8.3.C	1471M69P01, 1471M69P02, 1519M91P01
(3) 8.3.D	1519M91P02
(4) 8.3.E	1519M91P03, 1519M91P04
(5) 8.3.F	1519M91P05
(6) 8.3.G	1519M91P06, 1820M34P01
(7) 8.3.H	1519M91P07, 1820M34P02
(8) 8.3.J	1519M91P09, 1519M91P10, 1820M34P04, 1820M34P05

Previous Software Versions of ECU Software

(h) For a period of 24 months after the effective date of this AD, once an ECU containing a software version not listed in Table 1 of this AD is installed on an engine, that ECU can be replaced with an ECU containing a previous version of software listed in Table 1.

(i) Once the software version listed in Table 1 of this AD has been removed and new FAA-approved software version is installed in an ECU, reverting to those older software versions in that ECU is prohibited.

(j) After 60 months from the effective date of this AD, use of an ECU with a software version listed in Table 1 of this AD is prohibited.

Definitions

(k) For the purposes of this AD:

(1) Next shop visit of the ECU is when the ECU is removed from the engine for overhaul or maintenance after the effective date of this AD.

(2) Next shop visit of the engine is when the engine is removed from the airplane for maintenance in which a major flange is disassembled after the effective date of this AD. The following engine maintenance actions, either separately or in combination with each other, are not considered a next shop visit of the engine:

(i) Removal of the upper high pressure compressor (HPC) stator case solely for airfoil maintenance.

(ii) Module-level inspection of the HPC rotor stages 3-9 spool.

(iii) Replacement of stage 5 HPC variable stator vane bushings or lever arms.

(iv) Removal of the accessory gearbox.

(v) Replacement of the inlet gearbox polytetrafluoroethylene seal.

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.

Special Flight Permits

(m) Special flight permits are not authorized.

Related Information

(n) Information on removing ECU software and installing new software, which provides increased margin to flameout, can be found in GE Service Bulletin No. CF6-80C2 S/B 73-0351, dated April 11, 2007.

(o) Contact John Golinski, 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.

Issued in Burlington, Massachusetts, on July 11, 2007.

Francis A. Favara,

Manager, Engine and Propeller Directorate, Aircraft Certification Service.