Airworthiness directives: Boeing,
[Federal Register: November 5, 1999 (Volume 64, Number 214)]
[Proposed Rules]
[Page 60386-60388]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr05no99-18]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-231-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 747 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking (NPRM).
SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 747 series airplanes. This proposal would require repetitive inspections to detect cracking of the forward and aft inner chords and the splice fitting of the forward inner chord of the station 2598 bulkhead, and repair, if necessary. This proposal is prompted by reports of fatigue cracking found in those areas. The actions specified by the proposed AD are intended to detect and correct such cracking, which could result in reduced structural capability of the bulkhead and the inability of the structure to carry horizontal stabilizer flight loads.
DATES: Comments must be received by December 20, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-231-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: Bob Breneman, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2776; 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 filedin 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 99-NM-231-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. 99-NM-231-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.
Discussion
The FAA has received reports indicating that fatigue cracking has been detected in the forward and aft inner chords and the splice fitting of the forward inner chord of the station 2598 bulkhead on Boeing Model 747 series airplanes. The horizontal stabilizer hinge fittings are attached to the station
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2598 bulkhead. The bulkhead includes a large cutout that gives access to the rear spar of the horizontal stabilizer. The reports indicate that the cracking was detected around the upper corners of the cutout. In addition, a recent report indicates that a fatigue crack was detected in the station 2598 splice fitting where it attaches to the upper and lower sections of the bulkhead forward inner chord. Such cracking, if not detected and corrected, could result in reduced structural capability of the bulkhead and the inability of the structure to carry horizontal stabilizer flight loads.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2427, dated December 17, 1998, which describes procedures for a one-time high frequency eddy current (HFEC) inspection and repetitive detailed visual inspections to detect cracking of the forward and aft inner chords of the station 2598 bulkhead, and repair, if necessary.
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 require a one-time HFEC inspection and repetitive detailed visual inspections to detect cracking of the forward and aft inner chords of the station 2598 bulkhead, and repair, if necessary. These actions would be required to be accomplished in accordance with the alert service bulletin described previously, except as discussed below. The proposed AD also would require a one-time HFEC inspection and repetitive detailed visual inspections to detect cracking of the splice fitting of the forward inner chord of the station 2598 bulkhead. Such inspections of the splice fitting of the forward inner chord would be required to be accomplished in accordance with procedures included in paragraphs (a)(2) and (b)(2) of this AD. If any cracking is found during such inspections, repair would be required to be accomplished in accordance with a method approved by the FAA, as specified in paragraph (d) of this proposed AD.
Differences Between Proposed Rule and Alert Service Bulletin
Operators should note that, although the alert service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, this proposed AD would require the repair of those conditions to be accomplished in accordance with a method approved by the FAA, or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings.
Operators also should note that, as described previously, this proposed AD would require a one-time HFEC inspection and repetitive detailed visual inspections to detect cracking of the splice fitting of the forward inner chord of the station 2598 bulkhead. The alert service bulletin does not specify such inspections of the splice fitting. Also, though this inspection area is shown in Figure 2, Detail A, and Figure 3, Detail A, of the alert service bulletin, the inspection area is not highlighted in those figures.
Interim Action
This is considered to be interim action. The manufacturer has advised that it currently is developing a modification that will positively address the unsafe condition addressed by this AD. Once this modification is developed, approved, and available, the FAA may consider additional rulemaking.
Cost Impact
There are approximately 1,301 airplanes of the affected design in the worldwide fleet. The FAA estimates that 260 airplanes of U.S. registry would be affected by this proposed AD.
It would take approximately 2 work hours per airplane to accomplish the proposed HFEC inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed inspection on U.S. operators is estimated to be $31,200, or $120 per airplane.
It would take approximately 2 work hours per airplane to accomplish the proposed detailed visual inspections, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed inspections on U.S. operators is estimated to be $31,200, or $120 per airplane, per inspection cycle.
The cost impact figures discussed above are 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 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 proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
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
-
The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
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Section 39.13 is amended by adding the following new airworthiness directive:
Boeing: Docket 99-NM-231-AD.
Applicability: All Model 747 series airplanes, 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 (e) 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
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been eliminated, the request should include specific proposed actions to address it.
Compliance: Required as indicated, unless accomplished previously.
To detect and correct cracking of the forward and aft inner chords and the splice fitting of the forward inner chord of the station 2598 bulkhead, which could result in reduced structural capability of the bulkhead and the inability of the structure to carry horizontal stabilizer flight loads, accomplish the following:
Initial Inspection
(a) Prior to the accumulation of 13,000 total flight cycles, or within 1,000 flight cycles after the effective date of this AD, whichever occurs later: Accomplish the requirements specified in paragraphs (a)(1) and (a)(2) of this AD.
(1) Perform a high frequency eddy current inspection (HFEC) to detect cracking of the forward and aft inner chords of the station 2598 bulkhead, in accordance with Boeing Alert Service Bulletin 747- 53A2427, dated December 17, 1998.
(2) Perform an HFEC inspection to detect cracking of the splice fitting along the upper and lower attachment to the forward inner chord of the station 2598 bulkhead, as shown in Figure 2, Detail A, of Boeing Alert Service Bulletin 747-53A2427, dated December 17, 1998.
Note 2: Operators should note that the inspection area specified in paragraph (a)(2) of this AD is NOT highlighted in Figure 2, Detail A, of Boeing Alert Service Bulletin 747-53A2427, dated December 17, 1998.
Repetitive Inspections
(b) Within 3,000 flight cycles after accomplishment of the inspections required by paragraph (a) of this AD: Accomplish the inspections specified in paragraphs (b)(1) and (b)(2) of this AD. Repeat the inspection thereafter at intervals not to exceed 3,000 flight cycles.
(1) Perform a detailed visual inspection to detect cracking of the forward and aft inner chords of the station 2598 bulkhead, in accordance with Boeing Alert Service Bulletin 747-53A2427, dated December 17, 1998.
Note 3: For the purposes of this AD, a detailed visual inspection is defined as: ``An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.''
(2) Perform a detailed visual inspection to detect cracking of the splice fitting along the upper and lower attachment to the forward inner chord of the station 2598 bulkhead, as shown in Figure 3, Detail A, of Boeing Alert Service Bulletin 747-53A2427, dated December 17, 1998.
Note 4: Operators should note that the inspection area specified in paragraph (b)(2) of this AD is NOT highlighted in Figure 3, Detail A, of Boeing Alert Service Bulletin 747-53A2427, dated December 17, 1998.
Repair
(c) If any cracking is detected during the inspections required by paragraph (a)(1) or (b)(1) of this AD, prior to further flight, repair in accordance with Boeing Alert Service Bulletin 747-53A2427, dated December 17, 1998, except as provided by paragraph (d) of this AD.
(d) If any cracking is detected during the inspections required by paragraph (a)(2) or (b)(2) of this AD, or where the alert service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, prior to further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative (DER) who has been authorized by the Manager, Seattle ACO, to make such findings. For a repair method to be approved by the Manager, Seattle ACO, or a Boeing DER, as required by this paragraph, the approval letter must specifically reference this AD.
Alternative Methods of Compliance
(e) 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 ACO. 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 5: 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
(f) 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. Issued in Renton, Washington, on November 1, 1999. D. L. Riggin, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 99-29056Filed11-4-99; 8:45 am]
BILLING CODE 4910-13-U
