AD 98-19-05

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 757-200 series airplanes was published in the Federal Register on September 25, 1997 (62 FR 50263). That action proposed to require the application of a sealant, secondary fuel barrier, and corrosion-inhibiting compound to certain portions of the wing center section.

Comments

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

Support for the Proposal

One commenter supports the proposed rule.

Request for Extension of the Compliance Time

Several commenters request that the compliance time for the actions required by this proposed AD be extended, and suggest that the compliance thresholds be revised to coincide with the next scheduled heavy maintenance check.Compliance times of 36 months, 48 months, and 72 months are suggested as appropriate for the extension. The commenters state that the extensive access required to fully clean the corrosion inhibiting compound applied at the factory, the cure times for the sealants, and the application of the corrosion inhibiting compounds, are all factors making it prohibitive to incorporate the modification during "C" checks. One commenter estimates that it could save $36,000 by retrofitting its 17 airplanes during a heavy maintenance check instead of during a "C" check. Another operator states that to accomplish the modification on its affected fleet of airplanes within 18 months would require special scheduling and would create an economic burden. Another commenter states that it does not agree with the logic used to determine the urgency of this issue because there have not been any reports or evidence of fuel vapors reaching the pressurized area.

The FAA concurs that the compliance timescan be extended somewhat. The intent of the AD is that the inspections be conducted during a regularly scheduled maintenance visit for the majority of the affected fleet, when the airplanes would be located at a base where special equipment and trained personnel would be readily available, if necessary. Based on the information supplied by the commenters, the FAA now recognizes that a compliance time of 48 months corresponds more closely to the interval representative of most of the affected operators' normal maintenance schedules. Paragraph (a) of the final rule has been revised to require accomplishment of the required actions "at the next scheduled heavy maintenance check (i.e., a "4C" check) or within 48 months after the effective date of the AD, whichever occurs first." The FAA does not consider that this extension will adversely affect safety. The affected area is small, approximately 200 square inches, and there have been no reported leaks in this area of the front spar of the wing center section. In addition, the barrier does not function as the primary barrier but is designed to provide a fume-proof and fuel-proof barrier in the event of a failure of the fastener sealant or structural cracks in the center section.

Request for Use of Equivalent Methods and Finishes

One commenter requests that the proposed AD be revised to allow the use of an "industry accepted standard or practice" material, in lieu of "original equipment manufacturer approved parts and procedures." The commenter states that Boeing Service Bulletin 757-57-0053, dated February 6, 1997, lists secondary fuel barrier BMS 5-81, Type II, which is not stocked by the airplane manufacturer or this operator.

The FAA does not concur with the commenter's request. The material in question, secondary fuel barrier, is used on all current generation Boeing airplanes and, from time to time, may require replacement following structural work on the fuel tank walls. Although such material may not currently be stocked by this operator, it should be readily available. Further, BMS 5-81, Type II, has specific property requirements needed to ensure a fume-proof and fuel-proof barrier over the life of the airplane. Allowing use of other substances without a detailed review by the FAA could compromise the performance of the barrier. However, for any material or process an operator may wish to substitute, the operator may request approval of an alternative method of compliance in accordance with the provisions of paragraph (b) of this AD.

Request for Revision of Cost Impact Information

Two commenters state that the proposed AD underestimates the cost of the modification, in that the economic analysis did not include the 18 to 36 work hours required to gain access to the front spar of the wing center section and to return the airplane to a serviceable condition. Another commenter states that the airplane downtime required to accomplish the modification during a "C" check was not included in the cost impact information.

The FAA acknowledges that the cost impact information, below, describes only the "direct" costs of the specific actions required by this AD. The estimate of 2 work hours necessary to accomplish the required actions was provided to the FAA by the manufacturer, and represents the time necessary to perform only the actions actually required by this AD. The FAA recognizes that, in accomplishing the requirements of any AD, operators may incur "incidental" costs in addition to the "direct" costs. The cost analysis in AD rulemaking actions, however, typically does not include incidental costs, such as the time required to gain access and close up; planning time; or time necessitated by other administrative actions. Because incidental costs may vary significantly from operator to operator, they are almost impossible to calculate.

Furthermore, because the FAA generally attempts to impose compliance times that coincide with operators' scheduled maintenance, the FAA considers it inappropriate to attribute the costs associated with aircraft "downtime" to the cost of the AD because, normally, compliance with the AD will not necessitate any additional downtime beyond that of a regularly scheduled maintenance hold. Even if, in some cases, additional downtime is necessary for some airplanes, the FAA does not possess sufficient information to evaluate the number of airplanes that may be so affected or the amount of additional downtime that may be required. Therefore, attempting to estimate such costs would be futile. No change to the final rule is necessary.

Explanation of Changes Made to Proposal

Since the issuance of the proposed AD, the manufacturer has issued Boeing Service Bulletin 757-57-0053, Revision 1, dated January 15, 1998. This revision is essentially the same as Boeing Service Bulletin 757-57-0053, dated February 6, 1997 (which is cited in the proposal as the appropriate source of service information for accomplishment of the requirements of the AD), with minor editorial changes incorporated. The FAA has reviewed and approved this revision as an additional source of service information for accomplishment of the actions required by this AD, and has revised the final rule accordingly.

Conclusion

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact

There are approximately 724 Boeing Model 757-200 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 463 airplanes of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per airplane to accomplish the required actions, and that the averagelabor rate is $60 per work hour. Required parts will cost approximately $100 per airplane. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $101,860, or $220 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the 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 adopted herein will not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) isnot 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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment

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

PART 39 - AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continuesto read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) 2. Section 39.13 is amended by adding the following new airworthiness directive: