E6-4700. Airworthiness Directives; General Electric Company CT7-5, -7, and -9 Series Turboprop Engines

AGENCY:

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

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to supersede an existing airworthiness directive (AD) for General Electric Company (GE) CT7-5A2, -5A3, -7A, -7A1, -9B, -9B1, and -9B2 turboprop engines, with certain part number (P/N) and serial number stage 2 turbine aft cooling plates installed. That AD currently requires a onetime eddy current inspection (ECI) of boltholes in certain P/N stage 2 turbine aft cooling plates. This proposed AD would expand the population of affected CT7 turboprop engine models, but would reduce the number of cooling plates affected. It would also require a onetime ECI of boltholes in certain P/N stage 2 turbine aft cooling plates. This proposed AD results from the manufacturer identifying the affected stage 2 turbine aft cooling plates by serial number. We are proposing this AD to prevent separation of the stage 2 turbine aft cooling plate, resulting in uncontained engine failure and damage to the airplane.

DATES:

We must receive any comments on this proposed AD by May 30, 2006.

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: Docket Management Facility; U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC 20590-0001.
• Fax: [phone].
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

Contact General Electric Aircraft Engines CT7 Series Turboprop Engines, 1000 Western Ave, Lynn, MA 01910; telephone [phone], fax [phone], for the service information identified in this proposed AD.

FOR FURTHER INFORMATION CONTACT:

Mark Bouyer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments regarding this proposal. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2005-20944; Directorate Identifier 2003-NE-64-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 DMS 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 docket that contains the proposal, any comments received and any final disposition in person at the DMS Docket Offices between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Office (telephone [phone]) is located on the plaza level of the Department of Transportation Nassif Building at the street address stated in ADDRESSES. Comments will be available in the AD docket shortly after the DMS receives them.

Discussion

On April 19, 2005, the FAA issued AD 2005-18-01, Amendment 39-14247 (70 FR 54835, September 19, 2005). That AD requires a onetime ECI of boltholes in certain P/N stage 2 turbine aft cooling plates. That AD resulted from reports of six stage 2 turbine aft cooling plate boltholes found cracked during inspection. That condition, if not corrected, could result in stage 2 turbine aft cooling plate separation, resulting in uncontained engine failure and damage to the airplane.

Actions Since AD 2005-18-01 Was Issued

Since that AD was issued, GE determined that it is necessary to expand the population of affected CT7 turboprop engine models to include CT7-9C/-9C3/-9D/-9D2 turboprop engines with stage 2 turbine aft cooling plate P/N 6064T07P01, 6064T07P02, 6064T07P05, or 6068T36P01 installed. GE also defined the affected population of cooling plates by serial number. This proposed AD includes these model engines.

Relevant Service Information

We have reviewed and approved the technical contents of GE Alert Service Bulletin CT7-TP S/B 72-A0464, Revision 4, dated December 12, 2005, that describes procedures for performing an ECI of boltholes in certain P/N stage 2 turbine aft cooling plates and replacing the cooling plate, if necessary, with one with a serial number not listed in Section 4, Appendix A, of the SB.

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. For that reason, we are proposing this AD, which would expand the population of affected CT7 turboprop engine models, but would reduce the actual cooling plate population by specifying the affected cooling plates by serial number. This proposed AD would also require a onetime ECI of boltholes in certain P/N stage 2 turbine aft cooling plates, and replacement of the cooling plates if necessary. The proposed AD would require that you do these actions using the service information described previously.

Costs of Compliance

We estimate that this proposed AD would affect 494 engines installed on airplanes of U.S. registry. We also estimate that it would take about 1 work hour per engine to perform the proposed actions, and that the average labor rate is $80 per work hour. Based on the number of cracks found in the inspected engines, we estimate that 2.5% of the 494 engines will require replacing stage 2 turbine aft cooling plates because of rejection by the onetime ECI. Required parts would cost about $17,000 per engine. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $243,520.

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 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); 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. See the ADDRESSES section for a location to examine the regulatory evaluation.

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 removing Amendment 39-14247 (70 FR 54835, September 19, 2005) and by adding a new airworthiness directive, to read as follows:

General Electric Company: Docket No. FAA-2005-20944; Directorate Identifier 2003-NE-64-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this airworthiness directive (AD) action by May 30, 2006.

Affected ADs

(b) This AD supersedes AD 05-18-01, Amendment 39-14247.

Applicability

(c) This AD applies to General Electric Company (GE) CT7-5A2/-5A3/-7A/-7A1/-9B/-9B1/-9B2/-9C/-9C3/-9D/-9D2 turboprop engines with stage 2 turbine aft cooling plates, part number (P/N) 6064T07P01, 6064T07P02, 6064T07P05, or 6068T36P01 installed. These engines are installed on, but not limited to, Construcciones Aeronauticas, SA CN-235 series and SAAB Aircraft AB SF340 series airplanes.

Unsafe Condition

(d) This AD results from the manufacturer identifying the affected stage 2 turbine aft cooling plates by serial number. We are issuing this AD to prevent separation of the stage 2 turbine aft cooling plate, resulting in uncontained engine failure and damage to the airplane.

Compliance

(e) You are responsible for having the actions required by this AD performed at the next engine or hot section module shop visit, but before accumulating an additional 6,000 cycles-in-service after the effective date of the AD, unless already done.

Onetime Eddy Current Inspection (ECI)

(f) Perform a onetime ECI of the stage 2 turbine aft cooling plates P/N 6064T07P01, 6064T07P02, 6064T07P05, or 6068T36P01, that are listed by serial number in Section 4, Appendix A, of GE Alert Service Bulletin No. CT7-TP S/B 72-A0464, Revision 04, dated December 12, 2005. Use 3.(1) through 3.B.(3) of GE Alert Service Bulletin (ASB) No. CT7-TP S/B 72-A0464, Revision 4, dated December 12, 2005 to perform the inspection.

(g) For stage 2 turbine aft cooling plates that do not pass the Return to Service Criteria, do either of the following:

(1) Replace the stage 2 turbine aft cooling plate with a new cooling plate that has a serial number that is not listed in Section 4, Appendix A, of GE Alert Service Bulletin No. CT7-TP S/B 72-A0464, Revision 04, dated December 12, 2005, or

(2) Replace the stage 2 turbine aft cooling plate with a cooling plate that meets the acceptance criteria of 3.B.(1) through 3.B.(3) of GE Alert Service Bulletin (ASB) No. CT7-TP S/B 72-A0464, Revision 4, dated December 12, 2005.

(h) After the effective date of this AD, do not install any stage 2 turbine aft cooling plates with serial numbers identified in Section 4, Appendix A, without inspecting the cooling plate as specified in 3.B.(1) through 3.B.(3) of GE Alert Service Bulletin No. CT7-TP S/B 72-A0464 Revision 04, December 12, 2005.

Previous Credit

(i) Eddy current inspections of the stage 2 turbine aft cooling plate boltholes done before the effective date of this AD that use GE ASB No. CT7-TP S/B 72-A0464, dated February 25, 2003; or Revision 1, dated March 12, 2003; or Revision 2, dated May 9, 2003; or Revision 3, dated July 23, 2004, comply with the requirements specified in this AD.

Definition of Engine or Hot Section Module Shop Visit

(j) For the purposes of this AD, an engine or hot section module shop visit is defined as the introduction of the engine or hot section module into a shop that includes separating major case flanges.

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) None.

Issued in Burlington, Massachusetts, on March 24, 2006.

Thomas Boudreau,

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