Airworthiness Directives; Aerospatiale Model ATR72 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Supplemental notice of proposed rulemaking; reopening of comment period.

SUMMARY:

This document revises an earlier proposed airworthiness directive (AD), applicable to all Aerospatiale Model ATR72 series airplanes, that would have required a revision to the Airworthiness Limitations Section of the Instructions for Continued Airworthiness to incorporate inspections to detect fatigue cracking in certain structure, inspection intervals, and life limits for certain components. That proposal was prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. This new action revises the proposed rule to require the incorporation of revised and new inspections and life limits. The actions specified by this new proposed AD are intended to ensure that fatigue cracking of certain structural elements is detected and corrected; such fatigue cracking could adversely affect the structural integrity of these airplanes.

DATES:

Comments must be received by September 18, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 97-NM-273-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to (425) 227-1232.

Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 97-NM-273-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.

The service information referenced in the proposed rule may be obtained from Aerospatiale, 316 Route de Bayonne, 31060 Toulouse, Cedex 03, France. This information may be examined at the FAA, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Norman B. Martenson, Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2110; fax (425) 227-1149.

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 shall 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 notice may be changed in light of the comments received.

Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
• For each issue, state what specific change to the proposed AD is being requested.
• Include justification (e.g., reasons or data) for each request.

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 notice must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 97-NM-273-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, ANM-114, Attention: Rules Docket No. 97-NM-273-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to add an airworthiness directive (AD), applicable to all Aerospatiale Model ATR72 series airplanes, was published as a notice of proposed rulemaking (NPRM) in the Federal Register on August 3, 1999 (64 FR 42054). That NPRM would have required a revision to the Airworthiness Limitations Section of the Instructions for Continued Airworthiness to incorporate inspections to detect fatigue cracking in certain structure, inspection intervals, and life limits for certain components. That NPRM was prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. Such fatigue cracking, if not corrected, would adversely affect the structural integrity of these airplanes.

Comments

Due consideration has been given to the comments received in response to the NPRM.

Necessity for Rulemaking

One commenter, an operator, questions the need to issue the proposed AD. The commenter notes that a listing of airworthiness limitations is required for type certification, as specified by section 25.1529 of the Federal Aviation Regulations (14 CFR 25.1529) and Appendix H, paragraph H25.4. The commenter states that this listing is included in its Operations Specifications, and that such specifications would never be approved with any airworthiness limitations that were beyond the limits specified by the manufacturer. In light of this, the commenter considers the actions required by the proposed rule to be redundant.

The FAA infers that the commenter requests that the proposed AD be withdrawn. The FAA does not concur. As stated in the NPRM, all products certificated to comply with the airworthiness standards requiring “damage tolerance assessments” must have Instructions for Continued Airworthiness (or, for some products, maintenance manuals), that include an Airworthiness Limitations Section (ALS).

Based on in-service data or post-certification testing and evaluation, the manufacturer may revise the ALS to include new or more restrictive life limits and structural inspections, or it may become necessary for the FAA to impose new or more restrictive life limits and structural inspections, in order to ensure continued structural integrity and continued compliance with damage tolerance requirements. However, in order to require compliance with these new inspection requirements and life limits for previously certificated airplanes, the FAA must engage in rulemaking; namely, the issuance of an AD. Because loss of structural integrity would constitute an unsafe condition, it is appropriate to impose such requirements through the AD process. Although prudent operators already may have incorporated the latest revisions of the ALS, issuance of this AD ensures that all operators take appropriate action to correct the identified unsafe condition.

The practice of requiring a revision to the ALS, rather than requiring individual inspections, has been used for several years and is not a novel or unique procedure. Requiring ALS revisions is advantageous for operators because it allows them to record AD compliance status only once—at the time they make the revision—rather than after every inspection. It also has the advantage of keeping all airworthiness limitations, whether imposed by original certification or by the requirements of an AD, in one place within the operator's maintenance program, thereby reducing the risk of non-compliance because of oversight or confusion. In addition, for a large fleet of airplanes with several small operators, it is possible that operators may not receive revisions to the ALS. The AD process ensures that these operators are aware of the revisions to the ALS. No change to this proposed AD is necessary in this regard.

Request To Include Certification Maintenance Requirements Tasks

One commenter, the manufacturer, states that the “Time Limits” section of the Maintenance Planning Document (MPD) also includes Certification Maintenance Requirements (CMR) tasks that are applicable to the equipment and systems and are necessary to keep the certificated airworthiness standard. The commenter suggests adding a paragraph to the proposed AD to require accomplishment of the CMR tasks.

The FAA does not concur. Although the FAA agrees that accomplishment of CMR tasks is necessary to maintain these airplanes in an airworthy condition, the necessity for those actions is based on statistical safety analyses of various airplane systems prior to issuance of an airplane Type Certificate (TC). Thus, CMR tasks are undertaken for a different purpose than the actions required by this AD, and are intended to address a different unsafe condition than is addressed in this AD. However, if CMR tasks are added or made more restrictive following issuance of the TC, the FAA will consider separate rulemaking action to require accomplishment of those additional actions. No change to the AD is necessary in this regard.

Revisions to Service Information

Two commenters advise the FAA that Revision 3 of the “Time Limits” section of the ATR72 MPD was issued in January 1998, and suggest that the proposed AD address the use of the later revision of that document. The manufacturer also advises that Revision 4 of the “Time Limits” section for Model ATR72 series airplanes, dated July 1999, is in the process of review and approval by the appropriate airworthiness authorities. The manufacturer suggests delaying issuance of the final rule until approval of this latest revision is granted.

The FAA has received and reviewed the latest revision of the service information. Revision 4 differs from Revision 1, dated February 1996 (which was referenced in the proposed AD as the appropriate source of service information), in that it revises certain life limits for structural components or parts of the landing gear, engine components, and various equipment; and structural inspection times to detect fatigue cracking of certain Structural Significant Items; and, for Model ATR72-212A series airplanes, adds new life limits and inspection thresholds and intervals. The FAA has determined that the actions required by this AD must be accomplished in accordance with Revision 4 of the “Time Limits” section of the MPD, and is proposing such in this supplemental NPRM. Paragraph (a) of this proposed AD has been changed accordingly.

Use of Subsequent Service Information Revisions

One commenter requests that the FAA revise the proposed AD to refer to the current revision of the “Time Limits” section of the MPD, “or later approved revisions.” The commenter suggests that only referring to the current revision in the AD may lead to confusion about the validity of subsequent revisions.

The FAA does not concur. To use the phrase “or later approved revisions” in an AD when referring to future revisions of service information violates Office of the Federal Register (OFR) regulations regarding approval of materials that are “incorporated by reference” in rules. The AD may only refer to the service information that was submitted and approved by the OFR for “incorporation by reference.” In order for operators to use later revisions of the service information, either the AD must be revised to reference the specific later revisions, or the FAA must approve their use as an alternative method of compliance with this AD. No change to the AD is necessary in this regard.

MPD Section Reference

Two commenters state that, although the “Time Limits” section of the MPD is incorrectly referenced in the proposed AD as Section 9, the correct reference is Section 13. The FAA acknowledges the correction. However, to avoid any confusion in case the section number changes in the future, the FAA has removed the reference to the specific section of the “Time Limits” section in paragraph (a) of this AD.

Conclusion

Since the changes previously described expand the scope of the original proposed rule, the FAA has determined that it is necessary to reopen the comment period to provide additional opportunity for public comment.

Cost Impact

There are approximately 173 Aerospatiale Model ATR72 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 39 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 1 work hour per airplane to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $2,340, or $60 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

Regulatory Impact

The regulations proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

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.”

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

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:

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.