The FAA proposed to amend 14 CFR part 39 with a proposed AD. The proposed AD applies to GE CT7-5A2, -5A3, -7A, - 7A1, -9B, -9B1, and -9B2 turboprop engines, with certain P/N and serial number stage 2 turbine aft cooling plates installed. We published the proposed AD in the Federal Register on March 31, 2006 (71 FR 16248). That action proposed to expand the population of affected CT7 turboprop engine models required to undergo a onetime ECI of boltholes in certain P/N stage 2 turbine aft cooling plates. That action also proposed to reduce the number of cooling plates affected by identifying the serial numbers.
Examining the AD Docket
You may examine the docket that contains the AD, any comments received, and any final disposition in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Office (telephone (800) 647-5227) 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.
Comments
We provided the public the opportunity to participate in the development of this AD. We have considered the comments received.
Clarification of ECI Requirements
GE suggests that we clarify paragraph (f) of this AD to limit the required ECI to stage 2 turbine aft cooling plates that are being returned to service. This change would eliminate any requirement to ECI cooling plates that are not going to be reused. We agree. If the cooling plate is not going to be reused, there is no need to ECI it immediately after it is removed. Paragraph (h) of this AD requires an ECI of all cooling plates affected by this AD before they are returned to service. We made the clarification to paragraph (f).
Clarification of Onetime Inspection
GE proposes that we add a terminating action statement to clarify that the ECI is a onetime inspection and repetitive inspections of the stage 2 turbine aft cooling plate is unnecessary. We do not agree. This information is already included in paragraph (f), which specifies that the inspection is a onetime ECI. We did not change the AD.
Question on Compliance Threshold of 6,000 Cycles-in-Service (CIS)
GE also questions whether the calculated compliance threshold of 6,000 CIS is viable given the amount of time required to publish the AD. We do not agree. The number of engine cycles that will accumulate during the AD review process will not change the safety assessment that is based on the calculated compliance time. We did not change the AD.
Conclusion
We have carefully reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We have determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.
Costs of Compliance
We estimate that this AD will affect 494 engines installed on airplanes of U.S. registry. We also estimate that it will take about 1 work-hour per engine to perform the 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 percent of the 494 engines will require replacing stage 2 turbine aft cooling plates because of rejection by the onetime ECI. Required parts will cost about $17,000 per engine. Based on these figures, we estimate the total cost of the 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 authoritydescribed 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 AD will not have federalism implications under Executive Order 13132. This AD will 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 this AD:
(1) Is not a "significant regulatory action'' under Executive Order 12866;(2) Is not a "significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and
(3) 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.
We prepared a summary of the costs to comply with this AD and placed it in the AD Docket. 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, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, under the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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.
Sec. 39.13 [Amended]
2. The FAA amends Sec. 39.13 by removing Amendment 39-14247 70 FR 54835, September 19, 2005, and by adding a new airworthiness directive, Amendment 39-15018, to read as follows: