01-10180. Airworthiness Directives; Boeing Model 747 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 inspection of the aft trunnion of the wing landing gear for cracks and corrosion, and corrective action, if necessary. This action would require new repetitive inspections for cracks or corrosion of the aft trunnion outer cylinders of the wing landing gear, follow-on actions, and repetitive overhaul of the wing landing gear. The new actions would also apply to airplanes not included in the applicability of the existing AD. The actions specified by the proposed AD are intended to find and fix cracking or corrosion of the aft trunnion of the wing landing gear, which could result in collapse of the wing landing gear and consequent reduced controllability of the airplane.

DATES:

Comments must be received by June 11, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-294-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. 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. 2000-NM-294-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 2000-NM-294-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. 2000-NM-294-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On August 7, 1990, the FAA issued AD 90-06-18 R1, amendment 39-6706 (55 FR 33650, August 17, 1990), applicable to certain Boeing Model 747 series airplanes, to require repetitive inspections of the aft trunnion of the wing landing gear for cracks and corrosion, and corrective action, if necessary. That AD also provides an optional modification which terminates the repetitive inspections. That action was prompted by reports of several incidents of landing gear collapse due to corrosion and fatigue cracks. The requirements of that AD are intended to prevent such landing gear collapse, which could result in the inability of the pilot to safely control the airplane.

Actions Since Issuance of Previous Rule

Since the issuance of AD 90-06-18 R1, the FAA has received several reports that operators have found cracked or fractured aft trunnion outer cylinders of the wing landing gear on airplanes modified per the optional terminating action provided in that AD. Cracked or fractured aft trunnion outer cylinders could result in collapse of the wing landing gear and consequent reduced controllability of the airplane. The FAA has also determined that this unsafe condition could occur on all Boeing Model 747 series airplanes, not just the airplanes included in the applicability of the existing AD.

Explanation of Relevant Service Information

The FAA has reviewed and approved Boeing Alert Service Bulletin 747-32A2465, Revision 1, dated July 20, 2000, which describes procedures for new repetitive detailed visual inspections using a borescope to find cracking or corrosion of the aft trunnion outer cylinders of the wing landing gear, and follow-on actions. If no cracking or corrosion is found, the follow-on action is application of corrosion preventative compound to the aft trunnion. If any cracking or corrosion is found, the service bulletin specifies to contact Boeing for repair instructions. Flag note 2 of Figure 1 of the service bulletin also references specific sections of the Boeing Overhaul Manual for procedures for repetitive overhaul of the wing landing gear. 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 90-06-18 R1 to continue to require, for certain airplanes, inspection of the aft trunnion of the wing landing gear for cracks and corrosion, and corrective action, if necessary. For all affected airplanes, this proposed AD would add requirements for new repetitive inspections for cracks or corrosion of the aft trunnion outer cylinders of the wing landing gear, follow-on actions, and repetitive overhaul of the wing landing gear. 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

Operators should note that, although the 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 per a method approved by the FAA, or per 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.

Cost Impact

There are approximately 1,132 airplanes of the affected design in the worldwide fleet.

In AD 90-06-18 R1, the FAA estimated that the actions in that AD would affect 163 airplanes of U.S. registry. The actions that are currently required by AD 90-06-18 R1 take approximately 45 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the FAA estimates the cost impact of the currently required actions on U.S. operators to be $440,100, or $2,700 per airplane, per inspection cycle.

The FAA estimates that this proposed AD would affect 233 airplanes of U.S. registry. The new inspections proposed in this AD action would take approximately 8 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the FAA estimates the cost impact of the proposed inspection on U.S. operators to be $111,840, or $480 per airplane, per inspection cycle.

The new overhaul proposed in this AD action would take approximately 320 work hours per airplane to accomplish, at an average labor rate of $60 per work hour. Based on these figures, the FAA estimates the cost impact of the proposed overhaul on U.S. operators to be $4,473,600, or $19,200 per airplane, per overhaul.

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 39-6706 (55 FR 33650, August 17, 1990), and by adding a new airworthiness directive (AD), to read as follows:

Boeing: Docket 2000-NM-294-AD. Supersedes AD 90-06-18 R1, Amendment 39-6706.

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 been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To find and fix cracking or corrosion of the aft trunnion of the wing landing gear, which could result in collapse of the wing landing gear and consequent reduced controllability of the airplane, accomplish the following:

Restatement of Requirements of AD 90-06-18 R1

Repetitive Inspections and Corrective Actions (Certain Airplanes)

(a) For airplanes listed in Groups 1, 2, and 3 in Boeing Service Bulletin 747-32-2190, Revision 4, dated October 26, 1989, inspect as follows:

(1) Within the next 120 days after August 17, 1990 (the effective date of AD 90-06-18 R1, amendment 39-6706), perform a visual inspection, or a visual-plus-eddy-current inspection, of the wing landing gear at the trunnion, for cracks and corrosion, in accordance with Boeing Service Bulletin 747-32-2190, Revision 4, dated October 26, 1989.

(2) If no cracks or corrosion are found, repeat the inspection described in paragraph (a)(1) of this AD at intervals not to exceed 6 months if the visual inspection option was selected for the previous inspection, or at intervals not to exceed 18 months if the visual-plus-eddy-current inspection option was selected for the previous inspection. Doing paragraph (b), (c), or (d) of this AD ends the repetitive inspections required by this paragraph.

(3) Except as provided by paragraph (a)(4) of this AD, if cracks or corrosion are found, prior to further flight, remove and rework or replace cracked/corroded parts in accordance with Boeing Service Bulletin 747-32-2190, Revision 4, dated October 26, 1989.

(4) If only corrosion is found, as an alternative to paragraph (a)(3) of this AD, accomplish the terminating action described in Boeing Service Bulletin 747-32-2190, Revision 4, dated October 26, 1989, within 12 months after detection of corrosion, but no later than 36 months after August 17, 1990; and high-frequency-eddy-current inspect the wing landing gear trunnion at intervals not to exceed 6 months, until the terminating action is accomplished. Doing paragraph (b), (c), or (d) of this AD ends the repetitive inspections required by this paragraph.

Optional Terminating Action for Requirements of Paragraph (a)

(b) For airplanes listed in Groups 1, 2, and 3 in Boeing Service Bulletin 747-32-2190, Revision 4, dated October 26, 1989: Modification in accordance with Boeing Service Bulletin 747-32-2190, Revision 4, dated October 26, 1989, constitutes terminating action for the reinspection requirements of paragraph (a) of this AD.

New Requirements of This AD

Repetitive Detailed Visual Inspections and Follow-On Actions (All Airplanes)

(c) Within 180 days after the effective date of this AD, do a detailed visual inspection using a borescope to find cracking and corrosion of the aft trunnion outer cylinders of the wing landing gear. Do the inspection per Figure 2 of Boeing Alert Service Bulletin 747-32A2465, Revision 1, dated July 20, 2000. The detailed visual inspection is contained in Part 1 of the service bulletin. Thereafter, repeat the inspection at intervals not to exceed 6 months.

(1) If no corrosion or cracking is found during any inspection per paragraph (c) of this AD, before further flight, apply corrosion preventative compound, per the service bulletin. Repeat the application of corrosion preventative compound after each inspection per paragraph (c) of this AD.

(2) If any corrosion or cracking is found during any inspection per paragraph (c) of this AD, before further flight, repair per a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; or per 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, as required by this paragraph, the approval letter must specifically reference this AD.

Note 2:

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.”

Overhaul (All Airplanes)

(d) At the applicable compliance time stated in paragraph (d)(1) or (d)(2) of this AD, and thereafter at intervals not to exceed 10 years, overhaul the wing landing gear per Flag Note 2 of Figure 1 of Boeing Alert Service Bulletin 747-32A2465, Revision 1, dated July 20, 2000. If any cracking or corrosion outside the overhaul limits is found during this overhaul, before further flight, repair per a method approved by the Manager, Seattle ACO; or per data meeting the type certification basis of the airplane approved by a Boeing Company 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, as required by this paragraph, the approval letter must specifically reference this AD. For affected airplanes, doing this overhaul ends the repetitive inspections required by paragraph (a) of this AD.

(1) For Group 1 airplanes listed in Boeing Alert Service Bulletin 747-32A2465, Revision 1, on which the wing landing gear has NOT been modified per Flag Note 1 of Figure 1 of the service bulletin: Overhaul the wing landing gear within 48 months after the effective date of this AD.

(2) For Group 1 airplanes listed in Boeing Alert Service Bulletin 747-32A2465, Revision 1, on which the wing landing gear HAS been modified per Flag Note 1 of Figure 1 of the service bulletin; OR for Groups 2 and 3 airplanes listed in Boeing Alert Service Bulletin 747-32A2465, Revision 1: Overhaul the wing landing gear within 10 years since delivery of the airplane or last overhaul, or within 180 days after the effective date of this AD, whichever comes later.

Alternative Methods of Compliance

(e)(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 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.

(2) Alternative methods of compliance, approved previously in accordance with AD 90-06-18 R1, amendment 39-6706, are approved as alternative methods of compliance for paragraphs (a) and (b) 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

(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 April 18, 2001.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.