Federal Aviation Administration, DOT.
Notice of proposed rulemaking (NPRM).
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 777-200 series airplanes. This proposal would require replacement of certain existing bushings of the aft trunnion of the outer cylinder of the main landing gear (MLG) with new bushings, and replacement of grease in an undercut on the aft trunnion, if necessary. This action is necessary to prevent stress corrosion cracking and consequent fracture of the aft trunnion of the outer cylinder of the MLG, which could result in collapse of the MLG. This action is intended to address the identified unsafe condition.
Comments must be received by February 12, 2001.
Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-147-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 (425) 227-1232. Comments may also be sent via the Internet using the following address: email@example.com. Comments sent via fax or the Internet must contain “Docket No. 2000-NM-147-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.Start Further Info
FOR FURTHER INFORMATION CONTACT:
Stan Wood, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2772; fax (425) 227-1181.End Further Info End Preamble Start Supplemental Information
Interested persons are invited to participate in the making of the proposed rule by submitting such written data, views, or arguments as Start Printed Page 82960they 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-147-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-147-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.
The FAA has received several reports of cracking of the aft trunnion of the outer cylinder of the main landing gear (MLG) on certain Boeing Model 767 series airplanes. The aft trunnion is attached to the MLG beam by the aft trunnion pin. Bushings are installed in the aft trunnion at the place where a cross bolt retains the aft trunnion pin. Moisture can enter the aft trunnion in the area of these bushings. There is also an undercut on the aft trunnion in the area of the cross bolt, which is filled with grease during assembly of the MLG. This grease in the undercut can dry out over time, which may allow moisture to enter the aft trunnion and undercut areas. The accumulation of moisture can result in the formation of corrosion pits on the aft trunnion, which can lead to stress corrosion cracking and consequent fracture of the aft trunnion. This condition, if not corrected, could result in collapse of the MLG.
The design of the aft trunnion of the outer cylinder of the MLG on certain Boeing Model 777-200 series airplanes is similar to that on the affected Model 767 series airplanes. Therefore, those Model 777-200 series airplanes are subject to the same unsafe condition found on the Model 767 series airplanes.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin 777-32A0025, dated April 6, 2000, which describes procedures for replacement of certain existing bushings of the aft trunnion of the outer cylinder of the MLG with new bushings installed with corrosion-inhibiting compound. The procedures include removing the existing bushings, performing a detailed visual inspection of the aft trunnion area for corrosion or other damage, removing corrosion, if necessary, and installing new bushings with corrosion-inhibiting compound. For airplanes listed under Group 1 in the service bulletin, the service bulletin also includes instructions for replacing grease in the undercut of the aft trunnion with corrosion-inhibiting compound. These actions will prevent moisture from entering the aft trunnion and undercut areas, where such moisture can lead to the formation of corrosion pits. (Airplanes listed under Group 2 do not have an undercut area.) 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 require accomplishment of the actions specified in the service bulletin described previously, except as discussed below.
Differences Between Service Bulletin and This AD
Operators should note that, although the effectivity listing of the service bulletin includes airplanes having line numbers (L/N) 2 through 29 inclusive; except L/N's 10, 14, and 18; this proposed AD would apply to airplanes having L/N's 1 through 29 inclusive, except L/N's 10, 14, and 18. The FAA has determined that the subject area on the airplane with L/N 1 is identical to the subject areas on the Model 777-200 series airplanes listed in the service bulletin; therefore, the airplane with L/N 1 is also subject to the identified unsafe condition. Also, Note 3 has been included in this proposed AD to clarify that L/N 1 has the configuration of a Group 1 airplane.
Operators also should note that, although the service bulletin specifies that the manufacturer may be contacted for instructions on repair of certain conditions, this AD requires 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.
There are approximately 26 airplanes of the affected design in the worldwide fleet. The FAA estimates that 12 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 36 work hours per airplane to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Required parts would cost approximately $13,228 per airplane. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $184,656, or $15,388 per airplane.
The cost impact figure discussed above is 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.
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, Start Printed Page 82961it 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.Start List of Subjects
List of Subjects in 14 CFR Part 39End List of Subjects
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:Start Part
PART 39—AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
2. Section 39.13 is amended by adding the following new airworthiness directive:
Boeing: Docket 2000-NM-147-AD.
Applicability: Model 777-200 series airplanes; line numbers (L/N) 1 through 29 inclusive, except L/N's 10, 14, and 18; certificated in any category; except those on which the outer cylinder of the main landing gear (MLG) has been replaced in accordance with Boeing Service Bulletin 777-32-0003, dated October 9, 1997.
This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 stress corrosion cracking and consequent fracture of the aft trunnion of the outer cylinder of the MLG, which could result in collapse of the MLG, accomplish the following:
Replacement of Bushings
(a) Within 5 years and 300 days since date of manufacture of the airplane, or within 1 year after the effective date of this AD, whichever occurs later, replace bushings in the aft trunnion of the outer cylinder with new bushings by doing paragraphs (a)(1), (a)(2), (a)(3), and (a)(4) of this AD; as applicable; in accordance with Boeing Alert Service Bulletin 777-32A0025, dated April 6, 2000.
(1) Remove bushings in the aft trunnion of the outer cylinder of the MLG.
(2) Perform a one-time detailed visual inspection of the aft trunnion area for corrosion or other damage.
(3) For airplanes listed in Group 1 of the service bulletin and the airplane having L/N 1: Replace grease in the undercut of the aft trunnion with corrosion-inhibiting compound.
(4) Install new bushings with corrosion-inhibiting compound.
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.”
For the purposes of this AD, the airplane having L/N 1 is considered to have the configuration of a Group 1 airplane.
(b) If any corrosion or other damage is found during the inspection required by paragraph (a)(2) of this AD: Prior to further flight, repair in accordance with Boeing Alert Service Bulletin 777-32A0025, dated April 6, 2000; except, where the service bulletin specifies to contact Boeing for instructions, prior to further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; 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, as required by this paragraph, the approval letter must specifically reference this AD.
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 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.
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 §§ 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 December 22, 2000.
John J. Hickey,
Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 00-33343 Filed 12-28-00; 8:45 am]
BILLING CODE 4910-13-P