[Federal Register Volume 63, Number 150 (Wednesday, August 5, 1998)]
[Proposed Rules]
[Pages 41739-41741]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-20834]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-53-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 767 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 767 series 
airplanes. This proposal would require a detailed visual inspection to 
detect corrosion inside the forward trunnion joint of the main landing 
gear (MLG); follow-on actions; and repair, if necessary. The proposal 
also provides for optional terminating action for the repetitive 
inspections. This proposal is prompted by reports of corrosion at the 
forward trunnion thrust face, tabs, and the internal threads of the 
forward trunnion of the MLG due to moisture in the forward trunnion 
joint. The actions specified by the proposed AD are intended to prevent 
corrosion of the forward trunnion joint, which could lead to a stress 
corrosion fracture of the forward trunnion and possible consequent 
collapse of the MLG.

DATES: Comments must be received by September 21, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 97-NM-53-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: James G. Rehrl, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington; telephone (425) 227-2783; 
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

[[Page 41740]]

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-53-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-53-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received several reports of corrosion at the forward 
trunnion thrust face and tabs, and at the internal threads of the 
forward trunnion of the outer cylinder of the main landing gear (MLG) 
on Boeing Model 767 series airplanes. During the first overhaul of 
those airplanes, similar corrosion damage was found on several of the 
MLG's that were removed from these airplanes. These MLG's had 
accumulated between 20,000 and 26,000 total hours time-in-service, and 
between 7,000 and 9,000 total landings. The presence of corrosion, due 
to moisture in the trunnion joint, could lead to stress corrosion 
cracking of the forward trunnion. Such stress corrosion cracking, if 
not corrected, could result in a stress corrosion fracture of the 
forward trunnion and possible consequent collapse of the MLG.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
767-32A0127, dated January 29, 1996, which describes procedures for 
performing a detailed visual inspection to detect corrosion inside the 
forward trunnion joint of the MLG; follow-on actions; and repair, if 
necessary. The follow-on actions include either application of chrome 
plating to the forward trunnion, or application of corrosion-inhibiting 
compound to the forward trunnion and repetitive inspections for 
corrosion thereafter. Application of the chrome plating to the forward 
trunnion would eliminate the need for the repetitive inspections.
    The service bulletin references Component Maintenance Manual 32-11-
40, dated June 1, 1994, as an additional source of service information.

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 alert service bulletin described previously.

Cost Impact

    There are approximately 455 Boeing Model 767 series airplanes of 
the affected design in the worldwide fleet. The FAA estimates that 151 
airplanes of U.S. registry would be affected by this proposed AD.
    It would take approximately 8 work hours per airplane to accomplish 
the proposed visual 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 $72,480, or $480 per 
airplane, per inspection cycle.
    The cost impact figures above do not account for the time to gain 
access to the forward trunnion joint or to return a main landing gear 
to service. In this case, however, the access and close-up work hours 
may account for the predominant portion of the total cost impact of 
this proposed AD. It is estimated that it would take approximately 65 
work hours to gain access to both forward trunnion joints, and 89 work 
hours to return the airplane to service. If these costs are included, 
the cost impact for the proposed visual inspections would be 
approximately $1,467,720, or $9,720 per airplane, per inspection cycle.
    The repair of the forward trunnions (two per airplane), which would 
include both corrosion blend-out repairs as well as the application of 
chrome plate to certain portions of the forward trunnion, would take 
approximately 72 work hours to accomplish, at an average labor rate of 
$60 per work hour. The cost of the repair kits would be approximately 
$16,000 per airplane. Based on these figures, the cost impact of the 
proposed repair on U.S. operators is estimated to be $3,068,320, or 
$20,320 per airplane.
    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

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

Boeing: Docket 97-NM-53-AD.

    Applicability: Model 767 series airplanes, manufacturer's line 
positions 001 through 455 inclusive, 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 (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

[[Page 41741]]

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

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent corrosion of the forward trunnion joint of the main 
landing gear (MLG), which could lead to a stress corrosion fracture 
of the forward trunnion and possible consequent collapse of the MLG, 
accomplish the following:
    (a) Within 6 years since the outer cylinder of the MLG was new, 
last overhauled, or installed (replaced) after the last corrosion 
repair in accordance with Boeing Alert Service Bulletin 767-32A0127, 
dated January 29, 1996; or within 18 months after the effective date 
of this AD; whichever occurs later: Perform a detailed visual 
inspection to detect corrosion inside the forward trunnion joint and 
the internal threads of the MLG; in accordance with the 
Accomplishment Instructions of Boeing Alert Service Bulletin 767-
32A0127, dated January 29, 1996.
    (1) If no corrosion of the forward trunnion joint is found, 
prior to further flight, accomplish either paragraph (a)(1)(i) or 
(a)(1)(ii) of this AD.
    (i) Apply chrome plating to the forward trunnion thrust and tab 
faces in accordance with the alert service bulletin. Accomplishment 
of this application of chrome plating constitutes terminating action 
for the requirements of this AD.
    (ii) Apply corrosion-inhibiting compound to the forward trunnion 
joint in accordance with the Accomplishment Instructions of the 
alert service bulletin. Repeat the detailed visual inspection 
thereafter at intervals not to exceed six years or until chrome 
plating is applied to the forward trunnion thrust and tab faces in 
accordance with the alert service bulletin.
    (2) If any corrosion of the forward trunnion joint is found, 
prior to further flight, accomplish either paragraph (a)(2)(i) or 
(a)(2)(ii) of this AD.
    (i) Repair the forward trunnion and apply chrome plating to the 
forward trunnion thrust and tab faces in accordance with the alert 
service bulletin. Accomplishment of this application of chrome 
plating constitutes terminating action for the requirements of this 
AD.
    (ii) Repair the forward trunnion and apply corrosion-inhibiting 
compound to the forward trunnion joint in accordance with the alert 
service bulletin. Repeat the detailed visual inspection thereafter 
at intervals not to exceed six years or until chrome plating is 
applied to the forward trunnion thrust and tab faces in accordance 
with the alert service bulletin.
    (b) Replacement, repair, or overhaul of the outer cylinder of 
the MLG that includes the application of chrome plating to the 
forward trunnion thrust and tab faces in accordance with Boeing 
Alert Service Bulletin 767-32A0127, dated January 29, 1996, 
constitutes terminating action for the requirements of this AD.
    (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 Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate. 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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (d) 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 July 29, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-20834 Filed 8-4-98; 8:45 am]
BILLING CODE 4910-13-U