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Proposed Rule

Airworthiness Directives; General Electric Aircraft Engines CT7 Series Turboprop Engines

Document Details

Information about this document as published in the Federal Register.

Published Document

This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

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AGENCY:

Federal Aviation Administration, DOT.

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ACTION:

Supplemental notice of proposed rulemaking (NPRM).

SUMMARY:

This action revises an earlier proposed airworthiness directive (AD), applicable to certain General Electric Aircraft Engines (GEAE) CT7 series turboprop engines, that would have required initial and repetitive inspections and replacement of possibly improperly hardened PGB input pinions for certain serial number (SN) propeller gearboxes (PGB's). This action revises the proposed rule by eliminating the requirement for a one-time removal of possibly improperly hardened PGB input pinions, proposes a requirement to replace certain left-hand and right-hand idler gears at time of overhaul of PGB's, and proposes the replacement of certain SN PGB's before accumulating 2,000 flight hours. This proposal is prompted by an on-going investigation that concluded that low-time PGB removals are due to accelerated wear of the PGB idler gears, rather than improperly hardened PGB input pinions. The actions specified by the proposed AD are intended to prevent separation of PGB left-hand and right-hand idler gears, which could result in uncontained PGB failure and internal bulkhead damage, possibly prohibiting the auxilliary feathering system from fully feathering the propeller on certain PGB's.

DATES:

Comments must be received by August 12, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 99-NE-48-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may be inspected at this location, by appointment, between 8 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. Comments may also be sent via the Internet using the following address: “9-ane-adcomment@faa.gov”. Comments sent via the Internet must contain the docket number in the subject line.

The service information referenced in the proposed rule may be obtained from General Electric Aircraft Engines CT7 Series Turboprop Engines, 1000 Western Ave, Lynn, MA 01910; telephone (781) 594-3140, fax (781) 594-4805. This information may be examined, by appointment, at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA.

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FOR FURTHER INFORMATION CONTACT:

Barbara Caufield, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park; telephone (781) 238-7146, fax (781) 238-7199.

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SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 99-NE-48-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRM's

Any person may obtain a copy of this NPRM by submitting a request to the FAA, New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 99-NE-48-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to add an AD, applicable to General Electric Aircraft Engines (GEAE) CT7 series turboprop engines, was published as a notice of proposed rulemaking (NPRM) in the Federal Register on May 4, 2000 (65 FR 25892). That NPRM proposed initial and repetitive inspections of the PGB oil filter impending bypass button (IBB) for extension.

If the PGB oil filter IBB was extended, the proposed AD would have required follow-on inspections, maintenance, and if necessary, replacement of the PGB with a serviceable PGB. In addition, that proposed AD would have required, at the next return of the PGB to a CT7 turboprop overhaul facility after the effective date of the proposed AD, replacing possibly improperly hardened PGB input pinions with PGB input pinions manufactured with the proper hardening process. That proposed AD was prompted by reports of improperly hardened propeller gearbox (PGB) input pinions installed on General Electric Aircraft Engines (GEAE) CT7 series turboprop engines.

Since the issuance of that proposed AD, the FAA has determined that low-time PGB removals are not related to improperly hardened PGB input pinions. Analyses by the manufacturer and fleet operating experience have shown that improperly hardened PGB input pinions do not create an unsafe condition. It has been determined that low-time PGB removals are caused by accelerated wear of the PGB idler gears. The accelerated wear is caused by nonconforming gear surface conditions, which subject the gears to premature distress. This condition has been linked to the original manufacturer of a specific population of PGB gears. This condition, if not corrected, could result in separation of PGB left-hand and right-hand idler gears, which could result in uncontained PGB failure. For PGB's that are mated to Hamilton Standard propellers, separation of an idler gear that results in PGB internal bulkhead damage could possibly prohibit the auxilliary feathering system from fully feathering the propeller.

Since this change expands the scope of the originally proposed rule, the FAA has determined that it is necessary to reopen the comment period to provide additional opportunity for public comment.

Manufacturer's Service Bulletins (SB's)

The FAA has reviewed and approved the technical contents of GEAE CT7 Turboprop Service Bulletin CT7-TP S/B 72-0453, dated July 27, 2001, that describes procedures for inspections of the PGB oil filter impending bypass button (IBB) for extension, and if the oil filter IBB is extended, follow-on inspections, maintenance, and replacement actions. This SB also identifies PGB's by SN that require inspection. The FAA has also reviewed and approved the technical contents of GEAE CT7 Turboprop Service Bulletin CT7-TP S/B 72-0452, dated July 27, 2001, that requires replacement of certain SN's of left-hand and right-hand idler gears with serviceable gears. This SB also identifies affected PGB's by SN. Start Printed Page 40625

FAA's Determination of an Unsafe Condition and Proposed Actions

Since an unsafe condition has been identified that is likely to exist or develop on other GEAE CT7 series turboprop engines of the same type design, the proposed AD would require:

  • Initial inspection of the PGB oil filter IBB for extension within 50 hours time-in-service (TIS) after the effective date of this AD and,
  • If the PGB oil filter IBB is extended, follow-on inspections, maintenance, and replacement actions.
  • Repetitive inspections of the PGB oil filter IBB before the first flight of each operational day.
  • Replacing certain left-hand and right-hand idler gears with serviceable gears at the next return of the PGB to a CT7 turboprop overhaul facility.
  • Replacing certain PGB's that are mated to a Hamilton Standard propeller before accumulating 2,000 engine flight hours.

Since this change expands the scope of the originally proposed rule, the FAA has determined that it is necessary to reopen the comment period to provide additional opportunity for public comment.

Economic Analysis

There are approximately 150 engines of the affected design installed on airplanes of US registry that would be affected by this proposed AD. The FAA estimates that each IBB inspection would take approximately 0.25 work hours per engine, and the average labor rate is $60 per work hour. Inspection and replacement of idler gears would take approximately four work hours per engine at time of PGB overhaul. Replacement cost for idler gears per PGB is estimated to be $140,670. Replacement of a PGB would take approximately 48 hours. Therefore, the total cost on US operators would be approximately $21,138,750.

Regulatory Analysis

This proposed rule does not have federalism implications, as defined in Executive Order 13132, because it 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. Accordingly, the FAA has not consulted with state authorities prior to publication of this proposed rule.

For the reasons discussed above, I certify that 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); and (3) if promulgated, 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. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

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List of Subjects in 14 CFR Part 39

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The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

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PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

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Authority: 49 U.S.C. 106(g), 40113, 44701.

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[Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

General Electric Aircraft Engines: Docket No. 99-NE-48-AD.

Applicability

General Electric Aircraft Engines (GEAE) CT7 series turboprop engines, with propeller gearboxes (PGB's) identified by serial number (SN) in Table 1 of GEAE CT7 Turboprop Service Bulletin CT7-TP S/B 72-0452, dated July 27, 2001. These engines are installed on but not limited to SAAB 340 series airplanes.

Note 1:

This AD applies to each engine identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For engines that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (f) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance

Compliance with this AD is required as indicated, unless already done.

To prevent separation of PGB left-hand and right-hand idler gears, which could result in uncontained PGB failure and internal bulkhead damage, possibly prohibiting the auxilliary feathering system from fully feathering the propeller on certain PGB's, do the following:

(a) Inspect the PGB oil filter impending bypass button (IBB) for extension in accordance with the following schedule:

(1) Initially inspect within 50 hours time-in-service (TIS) after the effective date of this AD.

(2) Thereafter, inspect each operational day.

(b) If the PGB oil filter IBB is extended, replace the oil filter and perform follow-on inspections in accordance with 3.A of the Accomplishment Instructions of GEAE CT7 Turboprop Service Bulletin CT7-TP S/B 72-0453, dated July 27, 2001.

(c) At the next return of the PGB to a CT7 turboprop overhaul facility after the effective date of this AD, replace left-hand and right-hand idler gears in accordance with the Accomplishment Instructions of GEAE CT7 Turboprop Service Bulletin CT7-TP S/B 72-0452, dated July 27, 2001.

(d) If the PGB is mated to a Hamilton Standard propeller and the left-hand and right-hand idler gears have not been replaced in accordance with the Accomplishment Instructions of GEAE CT7 Turboprop Service Bulletin CT7-TP S/B 72-0452, dated July 27, 2001, replace the PGB before accumulating an additional 2,000 engine flight hours after the effective date of this AD.

Terminating Action

(e) Replacement of left-hand and right-hand idler gears in accordance with paragraph (c) of this AD, or replacement of the PGB in accordance with paragraph (d) of this AD constitutes terminating action to the repetitive inspections required by paragraph (a) of this AD.

Alternative Method of Compliance

(f) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Engine Certification Office (ECO). Operators must submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, ECO.

Note 2:

Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the ECO.

Special Flight Permits

(g) Special flight permits may be issued only for an airplane that has not more than one engine with a PGB oil filter IBB extended, to operate the airplane to a location where the requirements of this AD can be done.

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Issued in Burlington, Massachusetts, on June 4, 2002.

Francis A. Favara,

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

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[FR Doc. 02-14857 Filed 6-12-02; 8:45 am]

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