[Federal Register Volume 64, Number 178 (Wednesday, September 15, 1999)]
[Proposed Rules]
[Pages 50016-50017]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-23997]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-124-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 757-200 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 all Boeing Model 757-200 series 
airplanes. This proposal would require repetitive clearing of the drain 
passage at the aft end of the main landing gear truck beam to ensure 
moisture and contaminants within the truck beam can properly drain. 
This proposal is prompted by reports of fracture of main landing gear 
truck beams. The actions specified by the proposed AD are intended to 
prevent stress corrosion cracking, leading to fracture of a main 
landing gear truck beam during ground operations, which could result in 
either reduced controllability of the airplane or a fire.

DATES: Comments must be received by November 1, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-124-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: Rick Kawaguchi, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-1153; 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 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 99-NM-124-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-124-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports indicating that the main landing gear 
truck beam on Boeing Model 757-200 series airplanes has fractured due 
to stress corrosion cracking originating at corrosion pits on the 
surface of the inside diameter of the truck beam. The inner surface of 
the truck beam is protected from corrosion by several methods, 
including coatings over the metal surface and a gravity drain hole in 
the aft end of the truck beam inner surface that allows any moisture 
that enters the area to drain out. The drain holes on the fractured 
truck beams were found to be plugged with coating material, preventing 
moisture from draining out of the inside of the truck beam, which may 
result in increased corrosion on the inner surface of the truck beam. 
The primary cause of the condition may be inadequate adhesion of the 
coating to the inner surface of the truck beam during manufacture. This 
condition, if not corrected, could result in stress corrosion cracking, 
leading to fracture of a main landing gear truck beam during ground 
operations, which could result in either reduced controllability of the 
airplane or a fire.

Explanation of Relevant Service Information

    The FAA has reviewed Boeing Service Letter 757-SL-32-060, dated 
March 31, 1999, which describes procedures for repetitive clearing of 
the drain passage at the aft end of the main landing gear truck beam to 
ensure moisture and contaminants within the truck beam can properly 
drain. Accomplishment of the actions specified in the service letter 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 letter described previously, except as discussed below.

[[Page 50017]]

Differences Between Proposed Rule and Service Letter

    Operators should note that, although the service letter recommends 
accomplishing the clearing procedure at the next convenient maintenance 
opportunity, and at planned maintenance intervals thereafter (such as 
``C'' checks), the FAA has determined that the next convenient 
maintenance opportunity and at ``C'' checks thereafter would not 
address the identified unsafe condition in a timely manner. In 
developing an appropriate compliance time for this AD, the FAA 
considered not only the manufacturer's recommendation, but the degree 
of urgency associated with addressing the subject unsafe condition, the 
average utilization of the affected fleet, and the time necessary to 
perform the inspection (less than one hour). In light of all of these 
factors, the FAA finds a compliance time of 4 years since the last 
overhaul of the main landing gear or since the date of manufacture of 
the main landing gear (for main landing gear that has not been 
overhauled), or within 90 days after the effective date of this AD, 
whichever occurs latest, for initiating the required actions to be 
warranted. For the repetitive clearing procedures, the FAA finds an 
interval of 6 months, if the drain was previously found to be clogged, 
or 18 months, if the drain was previously found to be unclogged, to be 
warranted. The FAA finds that these intervals are warranted in that 
they represent appropriate intervals of time allowable for affected 
airplanes to continue to operate without compromising safety.

Cost Impact

    There are approximately 750 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 300 airplanes of U.S. registry 
would be affected by this proposed AD, that it would take approximately 
1 work hour per airplane to accomplish the proposed inspection, and 
that the average labor rate is $60 per work hour. Based on these 
figures, the cost impact of the proposed AD on U.S. operators is 
estimated to be $18,000, or $60 per airplane, per inspection cycle.
    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 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 99-NM-124-AD.

    Applicability: All Model 757-200 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 (b) 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, leading to fracture of a 
main landing gear truck beam during ground operations, which could 
result in either reduced controllability of the airplane or a fire, 
accomplish the following:

Inspection

    (a) Within 4 years since the last overhaul of the main landing 
gear or since the date of manufacture of the main landing gear (for 
main landing gear which have not been overhauled), or within 90 days 
after the effective date of this AD, whichever occurs latest: Insert 
a wooden probe, or similar non-metallic object, into the aft drain 
hole of the main landing gear truck beam, to clear the drain passage 
and ensure it can properly drain, in accordance with Boeing Service 
Letter 757-SL-32-060, dated March 31, 1999.
    (1) If the aft drain hole is found unclogged, repeat the 
clearing procedure thereafter at intervals not to exceed 18 months.
    (2) If the aft drain hole is found clogged, repeat the clearing 
procedure thereafter at intervals not to exceed 6 months.

Alternative Methods of Compliance

    (b) 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.

Special Flight Permits

    (c) 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 September 8, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-23997 Filed 9-14-99; 8:45 am]
BILLING CODE 4910-13-P