Airworthiness Directives; Boeing Model 747-100, -200, -300, 747SR, and 747SP Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Boeing Model 747-100, -200, -300, 747SR, and 747SP series airplanes, that currently requires a one-time inspection to detect cracking of the longeron splice fittings at stringer 11, on the left and right sides at body station 2598, and replacement of any cracked fitting with a new fitting. This action would reduce the compliance time for accomplishment of the currently required inspection and add a new requirement for repetitive inspections. This proposal is prompted by reports that fatigue cracking was found on longeron splice fittings. The actions specified by the proposed AD are intended to detect and correct such fatigue cracking, which could result in reduced controllability of the horizontal stabilizer.

DATES:

Comments must be received by April 7, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 97-NM-88-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.

The service information referenced in the proposed rule may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Rick Kawaguchi, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-1153; fax (425) 227-1181.

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.

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-88-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, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 97-NM-88-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On December 19, 1997, the FAA issued AD 97-26-21, amendment 39-10264 (62 FR 67550, December 29, 1997), applicable to certain Boeing Model 747-100, -200, -300, 747SR, and 747SP series airplanes. That AD requires a one-time inspection to detect cracking of the longeron splice fittings at stringer 11, on the left and right sides at body station 2598, and replacement of any cracked fitting with a new fitting. That action was prompted by reports that fatigue cracking was found on longeron splice fittings. The requirements of that AD are intended to detect and correct such fatigue cracking, which could result in reduced controllability of the horizontal stabilizer.

In the preamble to AD 97-26-21, the FAA indicated that the actions required by that AD were considered “interim action” and that further rulemaking action to propose repetitive inspections for all affected airplanes was being considered. The FAA now has determined that further rulemaking action is indeed necessary, and this proposed AD follows from that determination.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Service Bulletin 747-53A2410, Revision 3, dated March 12, 1998, including Addendum. That service bulletin describes procedures for repetitive detailed visual inspections to detect cracking of the longeron splice fittings at stringer 11, on the left and right sides at body station 2598, and replacement of any cracked fitting with a new fitting. The procedures described in that service bulletin are essentially similar to those described in Boeing Alert Service Bulletin 747-53A2410, Revision 2, dated October 30, 1997, which was referenced in AD 97-26-21 as the appropriate source of service information. Among other things, Revision 3 of the service bulletin includes a new table that clarifies what fastener kits are necessary for each splice fitting replacement. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would supersede AD 97-26-21 to continue to require an inspection to detect cracking of the longeron splice fittings at stringer 11, on the left and right sides at body station 2598, and replacement of any cracked fitting with a new fitting. The proposed AD would reduce the compliance time for accomplishment of the currently required inspection and add a new requirement for repetitive inspections. The actions would be required to be accomplished in accordance with the service bulletin described previously, except as discussed below.

Differences Between Service Bulletin and Proposed AD

The logic diagram in the service bulletin recommends a grace period of 500 flight cycles or 2,000 flight hours (whichever occurs first) for airplanes that have accumulated more than 22,000 total flight cycles or 78,000 total flight hours. Operators should note that this proposed AD does not provide a grace period for these airplanes. This proposed AD would require accomplishment of the initial inspection no later than the accumulation of 22,000 total flight cycles or 78,000 total flight hours, whichever occurs first. In AD 97-26-21, the FAA provides a grace period of 90 days after January 13, 1998 (the effective date of AD 97-26-21), in place of the grace period of 500 flight cycles or 2,000 flight hours recommended in the service bulletin. Because one of the purposes of the proposed AD is to reduce the initial compliance time for the inspection, the FAA finds that it would be inappropriate to allow airplanes that are approaching the inspection threshold of 22,000 total flight cycles or 78,000 total flight hours, i.e., the time when they would be required to accomplish the inspection required by AD 97-26-21, to continue to fly for additional time beyond the threshold specified in that AD. Also, since no additional airplanes would be added to the applicability of this proposed AD, all airplanes that would be subject to this proposed AD are currently subject to AD 97-26-21, and the grace period provided in AD 97-26-21 has already passed, this proposed AD does not restate that grace period.

Explanation of Compliance Time

The FAA finds that the service bulletin is not clear about the initial inspection threshold for airplanes with fewer than 17,000 total flight cycles or 63,000 total flight hours. Boeing has advised the FAA that it intended to provide an initial inspection threshold of 17,000 total flight cycles or 63,000 total flight hours (whichever occurs first), with a grace period of 1,800 flight cycles or 7,000 flight hours for airplanes that have already exceeded these thresholds upon receipt of the service bulletin. Therefore, this proposed AD provides compliance times that are consistent with Boeing's intent.

Cost Impact

There are approximately 685 airplanes of the affected design in the worldwide fleet. The FAA estimates that 99 airplanes of U.S. registry would be affected by this proposed AD.

The inspection that is currently required by AD 97-26-21 takes approximately 32 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions on U.S. operators is estimated to be $190,080, or $1,920 per airplane.

The proposed AD would require the same inspection currently required by AD 97-26-21 to be accomplished repetitively. Therefore, the cost impact of the proposed requirements of this AD on U.S. operators is estimated to be $190,080, or $1,920 per airplane, per inspection cycle.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or 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.