Airworthiness Directives; Boeing Model 757 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Final rule.

SUMMARY:

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 757 series airplanes, that requires replacement of transmission assemblies for the trailing edge flaps with modified transmission assemblies. This amendment is prompted by reports of broken bolts that attach the transmission assemblies for the trailing edge flaps. The actions specified by this AD are intended to prevent damage to the flap system, adjacent system, or structural components; and excessive skew of the trailing edge flap; which could result in reduced controllability of the airplane.

DATES:

Effective April 4, 2000.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of April 4, 2000.

ADDRESSES:

The service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT:

Robert C. Jones, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1118; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION:

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 series airplanes was published in the Federal Register on October 19, 1999 (64 FR 56279). That action proposed to require replacement of transmission assemblies for the trailing edge flaps with modified transmission assemblies.

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 To Allow Use of Other Service Information

One commenter requests that paragraph (b) of the proposed rule be revised to allow installation of a transmission assembly modified in accordance with the original issue of Boeing Alert Service Bulletin 757-27A0127, dated September 10, 1998. The commenter states that this would be consistent with “NOTE 2” of the proposed rule, which states, “Replacements accomplished in accordance with Boeing Alert Service Bulletin 757-27A0127, * * * are considered acceptable for compliance with paragraph (a) of this AD.”

The FAA concurs with the commenter's request, and has revised paragraph (b) to read, “ * * * no person shall install on any airplane, a trailing edge flap transmission assembly, unless it has been modified in accordance with this AD.”

Request To Allow Installation of a New Transmission

One commenter requests that paragraph (b) of the notice of proposed rulemaking (NPRM) be revised to allow installation of a new transmission that incorporates the upgraded torque limiter. The commenter states that some operators may choose to purchase a new transmission from the supplier, instead of modifying the existing unit.

The FAA concurs with the commenter's request. The FAA's intent was to allow installation of a new flap transmission assembly equipped with the new torque limiter or a modified flap transmission assembly. Therefore, in accordance with the commenter's request, paragraph (b) of this final rule has been revised to specify that no person shall install a trailing edge flap assembly, unless it has been modified in accordance with this AD, or, in the case of new transmission assemblies, it incorporates the new torque limiter. In addition, paragraph (a) of this final rule has been revised to clarify that replacement of existing transmission assemblies with new transmission assemblies that incorporate new torque limiters is acceptable for compliance with this AD.

Request To Clarify Preamble of Proposed Rule

One commenter requests that one sentence in the “Explanation of Relevant Service Information” section in the preamble of the proposed rule be revised. The proposed rule states that, “The modified transmission assemblies include new torque limiters that can prevent damage to the airplane from high system loads at the transmission assemblies, and can prevent excessive skew of the trailing edge flap.” The commenter requests that the last clause of the sentence be revised to read, “* * * and can, in some conditions, prevent excessive skew of the trailing edge flap.” The commenter states that, while a properly functioning torque limiter is expected to prevent excessive skew of the flap under some skew conditions, it is not certain that a properly functioning torque limiter will lock out under all circumstances to prevent a skewing flap from being damaged by drive system loads.

The FAA concurs with the intent of the commenter's request. While the new torque limiters represent a significant improvement over the existing torque limiters and are effective in preventing damage due to a jam, the FAA recognizes that the new torque limiters may not prevent excessive skew in all flight conditions. Also, because the new torque limiters may not prevent loss of controllability in all flight conditions, the FAA may consider further regulatory action in the future. However, despite the FAA's concurrence, no change to the final rule is necessary in this regard because the subject section is not restated in the final rule.

Request To Revise Cost Estimate

One commenter requests that the FAA revise the cost estimate of the proposed AD from $43,512,000 ($87,024 per airplane), to $44,172,000 ($88,344 per airplane). The commenter states that the suggested change is consistent with the estimates in the service bulletin.

The FAA does not concur with the commenter's request to revise the cost estimate. The estimate of 32 work hours specified in the NPRM represents the time necessary to perform only the actions actually required by this AD (i.e., replacement of transmission assemblies for the trailing edge flaps with modified transmission assemblies). 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. Thus, the FAA finds that the number of work hours estimated in the NPRM is consistent with the estimated number of work hours for accomplishing Part 1 of the service bulletin (excluding the work hours for “incidental” actions), and no change to the final rule is necessary in this regard.

Request To Extend Compliance Time

One commenter requests that the compliance time for the actions specified in paragraph (a) of the proposed rule be extended from 36 months to 48 months, to allow the proposed actions to be accomplished on all affected airplanes at a “4C” check. (The commenter considers the “4C” check interval to be 72 months.) Alternatively, the commenter suggests that the compliance time be revised to “at the airplane's first scheduled ‘4C’ check”, for airplanes that have not undergone a scheduled “4C” check since delivery, or within 36 months after the effective date of this AD, for airplanes that have undergone a scheduled “4C” check since delivery. The commenter states that most airplanes affected by this AD will have completed at least one “4C” check cycle by the end of the proposed 36-month compliance time. Thus, most operators would be able to accomplish the proposed AD on their airplanes during a “4C” check, which would allow accomplishment of this AD with only minimal schedule disruption. However, the commenter states that there are a few airplanes that will not complete a “4C” check cycle by the end of the proposed 36-month compliance time. According to the commenter, a 36-month compliance time would place an undue burden on operators that are not able to comply with the AD at a “4C” check because it would necessitate accomplishment of the requirements of this AD at a shorter check, thus delaying the airplane's return to revenue service. The commenter contends that extension of the compliance time to 48 months would not adversely affect the safety of airplanes subject to this AD, especially since airplanes that will not complete a “4C” check cycle by the 36 month compliance time are the newest, lowest-time, airplanes.

The FAA does not concur with the commenter's request to extend the compliance time for the actions specified in paragraph (a) of this AD. As stated in the preamble of the proposed rule, in developing an appropriate compliance time for this AD, the FAA considered not only the manufacturer's recommendation, but the degree of urgency associated with addressing the subject unsafe condition and the availability of required parts. With regard to the commenter's contention that an extension of the compliance time would not adversely affect safety, the FAA finds that the relative newness of the airplane or a low number of flight hours may have no effect on how the torque limiter operates in service. In light of all of these factors, the FAA finds a 36-month compliance time for initiating the required actions to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety, and wherein an ample number of required parts will be available for the modification of the U.S. fleet. No change to the final rule is necessary in this regard.

Request To Allow Installation of Unmodified Transmissions

One commenter requests that the FAA revise paragraph (b) of the proposed rule to allow installation of unmodified transmission assemblies for the trailing edge flaps for up to 18 months after the effective date of this AD. [Paragraph (b) of the proposal reads, “As of the effective date of this AD, no person shall install on any airplane, a trailing edge flap transmission assembly, unless it has been modified in accordance with Boeing Service Bulletin 757-27A0127, Revision 1, dated September 2, 1999.”] The commenter states that the proposed paragraph (b) seems “unnecessarily restrictive,” and that allowing installation of unmodified transmission assemblies for up to 18 months after the effective date of the AD would provide needed flexibility to operators until an ample supply of torque brake retrofit kits and seed units is available.

The FAA does not concur with the commenter's request. The FAA does not consider it to be in the interest of safety to allow installation of deficient transmission assemblies after the effective date of this AD. The FAA finds that the manufacturer's coordination with operators during preparation of the service bulletin, coupled with the time required for the rulemaking process (including the comment period following issuance of the proposed rule), has provided adequate time for operators to be able to install only modified transmissions (or new transmissions that incorporate the new torque limiter) after the effective date of this AD. As noted above, the FAA has been assured by the manufacturer that an ample number of required parts will be available for modification of the U.S. fleet. Therefore, no change to the final rule is necessary in this regard.

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 previously described. 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 796 Model 757 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 500 airplanes of U.S. registry will be affected by this AD, that it will take approximately 32 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will cost approximately $85,104 per airplane. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $43,512,000, or $87,024 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 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 final rule does not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this action (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. 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 continues to read as follows:

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

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

2000-04-18 Boeing: Amendment 39-11601. Docket 98-NM-354-AD.

Applicability: Model 757 series airplanes, as listed in Boeing Service Bulletin 757-27A0127, Revision 1, dated September 2, 1999; certificated in any category.

Note 1:

This AD applies to each airplane 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 airplanes 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 (c) 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: Required as indicated, unless accomplished previously.

To prevent damage to the flap system, adjacent system, or structural components; and excessive skew of the trailing edge flap; which could result in reduced controllability of the airplane; accomplish the following:

Replacement

(a) Within 36 months after the effective date of this AD, replace the transmission assemblies for the trailing edge flaps with transmission assemblies modified in accordance with Boeing Service Bulletin 757-27A0127, Revision 1, dated September 2, 1999; or with new transmission assemblies that incorporate newly designed torque limiters; in accordance with the service bulletin.

Note 2:

Replacements accomplished in accordance with Boeing Alert Service Bulletin 757-27A0127, dated September 10, 1998, are considered acceptable for compliance with paragraph (a) of this AD.

Spares

(b) As of the effective date of this AD, no person shall install on any airplane, a trailing edge flap transmission assembly, unless it has been modified in accordance with this AD, or, in the case of a new transmission assembly, unless it incorporates a newly designed torque limiter.

Alternative Methods of Compliance

(c) 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, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO.

Note 3:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.

Special Flight Permits

(d) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

Incorporation by Reference

(e) The actions shall be done in accordance with Boeing Service Bulletin 757-27A0127, Revision 1, dated September 2, 1999. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

(f) This amendment becomes effective on April 4, 2000.