[Federal Register Volume 66, Number 80 (Wednesday, April 25, 2001)]
[Proposed Rules]
[Pages 20763-20766]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-10180]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-294-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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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

[[Page 20764]]

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 (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. 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 (425) 
227-2771; 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 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

[[Page 20765]]

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.


Sec. 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,

[[Page 20766]]

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.
[FR Doc. 01-10180 Filed 4-24-01; 8:45 am]
BILLING CODE 4910-13-P