02-30349. Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200F, 747-200C, 747-300, 747-400, 747-400D, 747-400F, and 747SR 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 series airplanes, that currently requires inspections for cracking of the forward end clevis lugs of the flap track, and replacement of the flap track with a new flap track, if necessary. That AD also provides for an optional modification of the forward end clevis lugs, which terminates the required inspections. This action would expand the applicability of the existing AD, and would require new repetitive inspections for evidence of rotation or migration of the bushings or cracking of the lugs of the forward end clevis of the flap tracks that support the wing trailing edge flaps, and corrective actions if necessary. This action also would require an eventual terminating action. This action is necessary to prevent cracking and fracture of the forward end clevis of the flap track, which could result in reduced structural capability of the flap and reduced controllability of the airplane. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by January 16, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2002-NM-55-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2002-NM-55-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 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:

Tamara Anderson, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

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 action 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 action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2002-NM-55-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. 2002-NM-55-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has previously issued AD 90-24-09, amendment 39-6815 (55 FR 48228, November 20, 1990), applicable to certain Boeing Model 747 series airplanes. That AD requires inspections of the forward end clevis lugs of the flap track, and replacement of the flap track with a new flap track, if necessary. That AD also provides for an optional modification of the forward end clevis lugs, which terminates the required inspections. That action was prompted by reports of cracked or failed clevis lugs on two flap tracks. The requirements of that AD are intended to prevent separation of the wing trailing edge flap track from the airplane and reduction in the controllability of the airplane.

Actions Since Issuance of Previous Rule

Since the issuance of that AD, the FAA has received many reports of rotated and migrated bushings of the forward end clevis of the flap tracks that support the wing trailing edge flaps. Rotation and migration of the bushings has been attributed to insufficient interference fit. These findings occurred on airplanes not included in the applicability of the existing AD. In some cases, the rotation or migration of bushings resulted in stress corrosion cracking and fracture of the forward end clevis. This condition, if not corrected, could result in reduced structural capability of the flap and reduced controllability of the airplane.

Explanation of Relevant Service Information

The existing AD refers to Boeing Service Bulletin 747-57-2231, Revision 2, dated September 27, 1990, as the applicable source of service information for the actions required by that AD. Since the issuance of the existing AD, the FAA has reviewed and approved Boeing Service Bulletin 747-57-2307, Revision 1, dated January 17, 2002. That service bulletin replaces Boeing Service Bulletin 747-57-2231, and describes actions similar to those in Boeing Service Bulletin 747-57-2231, Revision 2, as described below. Modification of the forward end clevis lugs as described in Boeing Service Bulletin 747-57-2231, Revision 2, eliminates the need to do the actions in Boeing Service Bulletin 747-57-2307, Revision 1.

Boeing Service Bulletin 747-57-2307, Revision 1, describes procedures for repetitive detailed inspections for evidence of rotation or migration of the bushings or cracking of the lugs of the forward end clevis of the flap tracks that support the wing trailing edge flaps, and corrective actions if necessary. Evidence of migration or rotation of the bushings includes cracked or missing sealant around the bushing flange, or a gap between the bushing flange and the lug face. If migration or rotation of the bushings is found, but there is no cracking of the lugs, corrective actions include application of corrosion-inhibiting compound to the area around the flanged and shank ends of the migrated or rotated bushings, and repetitive inspections at a reduced interval. If any cracking is found, corrective actions involve replacement of the flap track with a new track. Replacement with a new track having certain part numbers eliminates the need for the repetitive inspections described previously for the replaced track.

The service bulletin also describes procedures for a terminating modification'replacement of the bushings of the forward end clevis with new bushings with a higher interference fit (including machining, performing magnetic particle inspections, and applying cadmium plating to the clevis bore and bushing). If migration or rotation of the bushings is found, but there is no cracking of the lugs, it may be necessary to do this terminating modification before further flight or at a reduced compliance time, depending on what group the airplane is listed in. The service bulletin recommends eventually doing this terminating modification on any forward end clevis for which the flap track is not replaced with a new flap track with certain part numbers, or on which the modification described in Boeing Service Bulletin 747-57-2231, Revision 2, has not been done. Doing the terminating modification eliminates the need for the repetitive inspections described previously.

Doing the actions specified in Boeing Service Bulletin 747-57-2307, Revision 1, is intended to adequately address the identified unsafe condition.

Explanation of Change to Requirements of Existing AD

Paragraph (a) of the existing AD requires visual inspections of the forward end clevis lugs of the flap tracks for cracking. Under the heading “Restatement of Requirements of AD 90-24-09,” we have revised paragraph (a) of this proposed AD to specify that the required inspection is considered to be a “detailed” inspection. Note 2 of this proposed AD defines such an inspection.

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 90-24-09 to continue to require inspections of the forward end clevis lugs of the flap track, and replacement of the flap track with a new flap track, if necessary. The proposed AD also would require the actions specified in Boeing Service Bulletin 747-57-2307, Revision 1, described previously, except as discussed below. Doing a modification according to Boeing Service Bulletin 747-57-2231, Revision 2; or Boeing Service Bulletin 747-57-2307, Revision 1; would terminate the requirements of this proposed AD.

Difference Between Proposed AD and Service Bulletin

Certain compliance times in the proposed AD would differ from those specified in Boeing Service Bulletin 747-57-2307, Revision 1, as explained below.

For certain airplanes not inspected previously, the service bulletin specifies an inspection threshold of 8 years after airplane delivery or 30,000 [total] flight hours, whichever occurs sooner. However, for these same airplanes, paragraph (e)(2)(i) of this proposed AD specifies an inspection threshold of 8 years after the earlier of the date of issuance of the ORIGINAL Airworthiness Certificate or the date of issuance of the Export Certificate of Airworthiness. This decision is based on our determination that “date of delivery” may be interpreted differently by different operators. We find that our proposed terminology is generally understood within the industry and records will always exist that establish these dates with certainty.

For airplanes not inspected previously that are near or over the threshold specified above, the service bulletin specifies a compliance time of 300 or 1,200 flight cycles after the issue date of the service bulletin, depending on the airplane's configuration. However, for all airplanes not inspected previously, paragraph (e)(2)(ii) of the proposed AD specifies a compliance time of the earlier of 300 flight cycles or 120 days after the effective date of the AD. This decision is based on new data received by the FAA that indicate that inspecting within 1,200 flight cycles may not provide an adequate level of safety. In light of these new data, we find a compliance time of 300 flight cycles or 120 days after the effective date of the AD, whichever occurs first, for completing 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.

Cost Impact

There are approximately 1,002 airplanes of the affected design in the worldwide fleet. The FAA estimates that 219 airplanes of U.S. registry would be affected by this proposed AD.

The actions that are currently required by AD 90-24-09 take approximately 2 work hours per airplane, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the currently required actions is estimated to be $120 per airplane, per inspection cycle.

The new inspections that are proposed in this AD action would take approximately 2 work hours per airplane, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the newly proposed inspections on U.S. operators is estimated to be $26,280, 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 proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions.

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.

§ 39.13

[Amended]

2. Section 39.13 is amended by removing amendment 39-6815 (55 FR 48228, November 20, 1990), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 2002-NM-55-AD. Supersedes AD 90-24-09, Amendment 39-6815.

Applicability: Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200F, 747-200C, 747-300, 747-400, 747-400D, 747-400F, and 747SR series airplanes; as listed in Boeing Service Bulletin 747-57-2307, Revision 1, dated January 17, 2002; 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 (k)(1) 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 cracking and fracture of the forward end clevis of the flap track, which could result in reduced structural capability of the flap and reduced controllability of the airplane, accomplish the following:

Restatement of Requirements of AD 90-24-09

Initial Inspection

(a) For airplanes listed in Boeing Service Bulletin 747-57-2231, Revision 2, dated September 27, 1990: Perform a detailed inspection of the forward end clevis lugs of the flap tracks for evidence of cracking, according to Boeing Service Bulletin 747-57-2231, Revision 2, dated September 27, 1990, and according to the following schedule:

(1) For airplanes listed in Group 1 in the service bulletin: Perform the inspection at flap track positions 1 through 8 within the next 30 days after December 5, 1990 (the effective date of AD 90-24-09, amendment 39-6815).

(2) For airplanes listed in Group 2 in the service bulletin: Perform the inspection at flap track positions 1, 2, 7, and 8 prior to the later of the following:

(i) Prior to the accumulation of 30,000 flight hours or 8 years after airplane delivery, whichever occurs first; or

(ii) Within 120 days after December 5, 1990.

(3) For airplanes listed in Group 3 in the service bulletin: Perform the inspection at flap track positions 1 through 8 prior to the later of the following:

(i) Prior to the accumulation of 30,000 flight hours or 8 years after airplane delivery, whichever occurs first; or

(ii) Within 120 days after December 5, 1990.

Flap Track Replacement

(b) If cracking is found during any inspection required by paragraph (a) of this AD, replace the flap track prior to further flight, according to Boeing Service Bulletin 747-57-2231, Revision 2, dated September 27, 1990.

Repetitive Inspections

(c) If no cracking is found during any inspection required by paragraph (a) of this AD, repeat the inspection required by paragraph (a) of this AD at intervals not to exceed 300 flight cycles for Group 1 airplanes, and 1,200 flight cycles for Group 2 and Group 3 airplanes, until paragraph (d), (e), or (i) of this AD has been done.

Optional Terminating Action

(d) For airplanes listed in Boeing Service Bulletin 747-57-2231, Revision 2, dated September 27, 1990: Accomplishment of the modification of the forward end clevis lugs of the flap tracks as specified in Boeing Service Bulletin 747-57-2231, Revision 2, dated September 27, 1990, constitutes terminating action for the requirements of paragraphs (a), (c), (e), and (i) of this AD.

New Requirements of this AD

Note 2:

For the purposes of this AD, a detailed 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.”

Detailed Inspections

(e) At the applicable compliance time specified in paragraph (e)(1) or (e)(2) of this AD, perform detailed inspections for evidence of rotation or migration of the bushings (including cracked or missing sealant around the bushing flange, or a gap between the bushing flange and the lug face) or cracking of the lugs of the forward end clevis of the flap tracks that support the wing trailing edge flaps, according to Part 1 of the Work Instructions in Boeing Service Bulletin 747-57-2307, Revision 1, dated January 17, 2002.

(1) For airplanes inspected before the effective date of this AD according to paragraph (a) of this AD: Do the inspection in paragraph (e) of this AD at the time specified in paragraph (e)(1)(i) or (e)(1)(ii) of this AD, as applicable. Doing this inspection terminates the requirements of paragraph (c) of this AD.

(i) For airplanes listed in Group 1 of Boeing Service Bulletin 747-57-2231, Revision 2: Inspect within 300 flight cycles after the most recent inspection per paragraph (a) or (c) of this AD.

(ii) For airplanes listed in Group 2 or 3 of Boeing Service Bulletin 747-57-2231, Revision 2: Inspect within 1,200 flight cycles after the most recent inspection per paragraph (a) or (c) of this AD.

(2) For airplanes NOT inspected before the effective date of this AD according to paragraph (a) of this AD: Do the inspection in paragraph (e) of this AD at the time specified in paragraph (e)(2)(i) or (e)(2)(ii) of this AD, whichever occurs later. This terminates the requirement to do paragraph (a) of this AD.

(i) Within 8 years after the EARLIER of the date of issuance of the ORIGINAL Airworthiness Certificate or the date of issuance of the Export Certificate of Airworthiness, or before the accumulation of 30,000 total flight hours, whichever occurs first.

(ii) Within 300 flight cycles or 120 days after the effective date of this AD, whichever occurs first.

Repetitive Inspections

(f) If no evidence of migration or rotation of the bushings or cracking of the lugs is found during the inspection required by paragraph (e) of this AD: Repeat the inspections at the applicable repetitive interval specified in Figure 1 of Boeing Service Bulletin 747-57-2307, Revision 1, dated January 17, 2002, until paragraph (d) or (i) of this AD has been done.

Corrective Actions and Repetitive Inspections

(g) If evidence of migration or rotation of the bushings is found during any inspection required by paragraph (e) or (f) of this AD, but NO cracking is found: Do paragraph (g)(1) or (g)(2) of this AD, as applicable, according to Boeing Service Bulletin 747-57-2307, Revision 1, dated January 17, 2002.

(1) For airplanes listed in Group 1 in the service bulletin and flap track numbers 3 and 6 on airplanes listed in Group 2 of the service bulletin: Before further flight, do the terminating modification in paragraph (i) of this AD, as specified in paragraph (i)(2) of this AD.

(2) For airplanes other than those identified in paragraph (g)(1) of this AD: Before further flight, apply corrosion-inhibiting compound according to the service bulletin, and do paragraphs (g)(2)(i) and (g)(2)(ii) of this AD at the intervals specified in those paragraphs, until paragraph (d) or (i) of this AD is done. Do paragraph (i) of this AD at the applicable time specified in paragraph (i)(2) of this AD.

(i) Repeat the inspections in paragraph (e) of this AD at the intervals specified in Figure 1 of the service bulletin.

(ii) Apply corrosion-inhibiting compound according to the service bulletin at intervals not to exceed 200 flight cycles.

Replacement of Flap Track

(h) If any cracking is found during any inspection required by paragraph (e), (f), or (g)(2)(i) of this AD: Before further flight, replace the cracked flap track with a new flap track, according to Boeing Service Bulletin 747-57-2307, Revision 1, dated January 17, 2002. Replacement with a new flap track having a part number listed in the “New Part Number” column of the table under paragraph 2.E. of the service bulletin constitutes terminating action for the requirements of this AD for the replaced track.

Terminating Modification

(i) At the applicable time specified in paragraph (i)(1) or (i)(2) of this AD: Do all actions (including but not limited to machining, performing magnetic particle inspections, and applying cadmium plating to the clevis bore and bushing) associated with replacing the bushings of the forward end clevis with new bushings with a higher interference fit on flap tracks 1, 2, 3, 4, 5, 6, 7, and 8; as applicable; according to Boeing Service Bulletin 747-57-2307, Revision 1, dated January 17, 2002. This replacement terminates the requirements of this AD.

(1) If no evidence of migration or rotation of the bushings or cracking of the lugs is found during any inspection required by paragraph (e) or (f) of this AD: Do the replacement within 8 years after the effective date of this AD.

(2) If any evidence of bushing migration or rotation is found during any inspection required by paragraph (e) or (f) of this AD: Do the replacement at the applicable time specified in Figure 1 of the service bulletin.

Credit for Actions According to Previous Revision of Service Bulletin

(j) Inspections, corrective actions, and terminating action done before the effective date of this AD according to Boeing Service Bulletin 747-57-2307, dated July 29, 1999, are considered acceptable for compliance with the corresponding action specified in this AD.

Alternative Methods of Compliance

(k)(1) 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. 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.

(2) Alternative methods of compliance, approved previously according to AD 90-24-09, amendment 39-6815, are approved as alternative methods of compliance with paragraphs (a), (b), (c), and (d) of this AD.

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

(l) 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 21, 2002.

Ali Bahrami,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.