Document ID: FAA-2007-0004-0029
Agency: faa
Document Type: Notice
Title: Airworthiness Directives; Boeing Model 747 Airplanes
Posted Date: 2007-08-31T04:00Z

[Federal Register: August 31, 2007 (Volume 72, Number 169)]
[Proposed Rules]               
[Page 50282-50284]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr31au07-19]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-29065; Directorate Identifier 2007-NM-142-AD]
RIN 2120-AA64

 
Airworthiness Directives; Boeing Model 747 Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for certain Boeing Model 747 airplanes. This proposed AD would require 
inspecting the trunnion fork assembly of the wing landing gears to 
determine the part number and serial number and to determine the 
category of the trunnion fork assemblies. For certain airplanes, this 
proposed AD also would require, if necessary, various inspections to 
detect discrepancies of the trunnion fork assemblies, related 
investigative/corrective actions, and a terminating action. This 
proposed AD results from a report of a fractured trunnion fork 
assembly. We are proposing this AD to prevent a fractured trunnion fork 
assembly, which could result in the collapse of a wing landing gear on 
the ground and possible damage to hydraulic equipment and the aileron 
and spoiler cables. Such damage could result in reduced controllability 
of the airplane.

DATES: We must receive comments on this proposed AD by October 15, 
2007.

ADDRESSES: Use one of the following addresses to submit comments on 
this proposed AD.
     DOT Docket Web site: Go to http://dms.dot.gov and follow 
the instructions for sending your comments electronically.
     Government-wide rulemaking Web site: Go to http://
www.regulations.gov and follow the instructions for sending your 
comments electronically.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590.
     Fax: (202) 493-2251.
     Hand Delivery: Room W12-140 on the ground floor of the 
West Building, 1200 New Jersey Avenue, SE., Washington, DC, between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, 
Washington 98124-2207, for the service information identified in this 
proposed AD.

FOR FURTHER INFORMATION CONTACT: Berhane Alazar, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6577; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to submit any relevant written data, views, or 
arguments regarding this proposed AD. Send your comments to an address 
listed in the ADDRESSES section. Include the docket number ``FAA-2007-
29065; Directorate Identifier 2007-NM-142-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of the proposed AD. We will 
consider all comments received by the closing date and may amend the 
proposed AD in light of those comments.
    We will post all comments we receive, without change, to http://
dms.dot.gov, including any personal information you provide. We will 
also post a report summarizing each substantive verbal contact with FAA 
personnel concerning this proposed AD. Using the search function of 
that Web site, anyone can find and read the comments in any of our 
dockets, including the name of the individual who sent the comment (or 
signed the comment on behalf of an association, business, labor union, 
etc.). You may review DOT's complete Privacy Act Statement in the 
Federal Register published on April 11, 2000 (65 FR 19477-78), or you 
may visit http://dms.dot.gov.

[[Page 50283]]

Examining the Docket

    You may examine the AD docket on the Internet at http://
dms.dot.gov, or in person at the Docket Operations office between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays. The 
Docket Operations office (telephone (800) 647-5527) is located on the 
ground level of the West Building at the DOT street address stated in 
the ADDRESSES section. Comments will be available in the AD docket 
shortly after the Docket Management System receives them.

Discussion

    We have received a report indicating that a fractured trunnion fork 
assembly was found during push back and tow of an airplane. Analysis 
showed that a crack was initiated by fatigue on the inner surface and 
eventually fractured by ductile rupture. The analysis also showed that 
the crack most likely initiated as a result of two manufacturing 
anomalies. A fractured trunnion fork assembly could result in the 
collapse of a wing landing gear on the ground and possible damage to 
hydraulic equipment and the aileron and spoiler cables. Such damage 
could result in reduced controllability of the airplane.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 747-32A2482, dated 
June 14, 2007. The service information describes procedures for 
inspecting the pad-up area on the forward upper inboard surface of the 
trunnion fork assembly of both the left and right wing landing gears to 
determine the part number and serial number and to determine the 
category of the trunnion fork assemblies. For certain airplanes, the 
service information describes the following procedures, as applicable:
     Doing an initial detailed inspection for damage to the 
protective finish and for corrosion of the trunnion fork assembly, and 
an initial high frequency eddy current (HFEC) inspection to detect 
cracks of the trunnion fork assembly (Part 2).
     Doing an ultrasonic inspection to determine the wall 
thickness in the area forward of the outer cylinder attach lugs in 8 
zones, and a hardness measurement if the wall thickness is less than 
the specified value (Part 3).
     Doing related investigative/corrective actions if 
necessary. The related investigative actions include repetitive 
detailed and HFEC inspections (Part 2). The corrective actions include 
overhauling the trunnion fork assembly (Part 4), and replacing the 
trunnion fork assembly (Part 5); as applicable.
     Replacing the trunnion fork assembly of the wing landing 
gear with a certain trunnion fork assembly (Part 5). Accomplishing the 
replacement ends the need for the actions specified in the service 
information.
    Accomplishing the actions specified in the service information is 
intended to adequately address the unsafe condition. The compliance 
time for the initial detailed, HFEC, and ultrasonic inspections and 
replacement specified in the service information is either 18 months or 
6 years, depending on the category of the trunnion fork assembly. The 
compliance time for the related investigative/corrective actions 
specified in the service information ranges between before further 
flight and 10 years, depending on the condition of the trunnion fork 
assembly.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to exist or develop on other airplanes 
of this same type design. For this reason, we are proposing this AD, 
which would require accomplishing the actions specified in the service 
information described previously.

Costs of Compliance

    There are about 1,055 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 215 airplanes of 
U.S. registry. The proposed inspection for part number, serial number, 
and category would take about 1 work hour per airplane, at an average 
labor rate of $80 per work hour. Based on these figures, the estimated 
cost of this inspection proposed by this AD for U.S. operators is 
$17,200, or $80 per airplane.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, Section 106, describes the 
authority of the FAA Administrator. Subtitle VII, Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    We are issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701, ``General 
requirements.'' Under that section, Congress charges the FAA with 
promoting safe flight of civil aircraft in air commerce by prescribing 
regulations for practices, methods, and procedures the Administrator 
finds necessary for safety in air commerce. This regulation is within 
the scope of that authority because it addresses an unsafe condition 
that is likely to exist or develop on products identified in this 
rulemaking action.

Regulatory Findings

    We have determined that this proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD 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.
    For the reasons discussed above, I certify that the 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. 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.
    We prepared a regulatory evaluation of the estimated costs to 
comply with this proposed AD and placed it in the AD docket. See the 
ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 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. The Federal Aviation Administration (FAA) amends Sec.  39.13 by 
adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-29065; Directorate Identifier 2007-NM-
142-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by October 
15, 2007.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 747-100, 747-100B, 747-100B 
SUD, 747-200B,

[[Page 50284]]

747-200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SR, and 
747SP series airplanes, certificated in any category; as identified 
in Boeing Alert Service Bulletin 747-32A2482, dated June 14, 2007.

Unsafe Condition

    (d) This AD results from a report of a fractured trunnion fork 
assembly. We are issuing this AD to prevent a fractured trunnion 
fork assembly, which could result in the collapse of a wing landing 
gear on the ground and possible damage to hydraulic equipment and 
the aileron and spoiler cables. Such damage could result in reduced 
controllability of the airplane.

Compliance

    (e) You are responsible for having the actions required by this 
AD performed within the compliance times specified, unless the 
actions have already been done.

Service Bulletin

    (f) The term ``service bulletin,'' as used in this AD, means 
Boeing Alert Service Bulletin 747-32A2482, dated June 14, 2007.

Initial Inspection for Part Number, Serial Number, and Category

    (g) Within 18 months after the effective date of this AD, 
inspect the pad-up area on the forward upper inboard surface of the 
trunnion fork assembly of both the left and right wing landing gears 
to determine the part number and serial number and to determine the 
category of the trunnion fork assemblies, in accordance with the 
Accomplishment Instructions of the service bulletin.

Follow-On Actions for Category A, B, C, or D Trunnion Fork Assemblies

    (h) If any part number and serial number identified as Category 
A, B, C, or D in Tables 2 and 3 of paragraph 1.E., ``Compliance,'' 
of the service bulletin is found installed during the inspection 
required by paragraph (g) of this AD: At the applicable compliance 
time(s) listed in Table 4 or 5 of paragraph 1.E., ``Compliance,'' of 
the service bulletin, except as provided by paragraph (i) of this 
AD, do the applicable action(s) in Table 1 of this AD and applicable 
related investigative/corrective actions, in accordance with the 
Accomplishment Instructions of the service bulletin.

                   Table 1.--Requirements for Category A, B, C, or D Trunnion Fork Assemblies
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                For--                            Do--                    And--                     Or--
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(1) Categories A and D trunnion fork   A detailed inspection    An ultrasonic            Do the terminating
 assemblies.                            for damage to the        inspection to            action (Part 5).
                                        protective finish and    determine the wall
                                        for corrosion of the     thickness in the area
                                        trunnion fork assembly   forward of the outer
                                        and a high frequency     cylinder attach lugs
                                        eddy current (HFEC)      in 8 zones, and a
                                        inspection to detect     hardness measurement
                                        cracks (Part 2).         if applicable (Part 3).
(2) Categories B and C trunnion fork   An ultrasonic            None...................  None.
 assemblies.                            inspection to
                                        determine the wall
                                        thickness in the area
                                        forward of the outer
                                        cylinder attach lugs
                                        in 8 zones, and a
                                        hardness measurement
                                        (Part 3).
----------------------------------------------------------------------------------------------------------------

    (i) Where paragraph 1.E., ``Compliance,'' of the service 
bulletin specifies a compliance time after the date on the service 
bulletin, this AD requires compliance within the specified 
compliance time after the effective date of this AD.

Terminating Action

    (j) Replacing the trunnion fork assembly of the wing landing 
gear with a trunnion fork assembly identified in Part 5 of the 
service bulletin, in accordance with and at the applicable time 
specified in Table 4 or 5 of paragraph 1.E., ``Compliance,'' of the 
service bulletin, constitutes terminating action for the 
requirements of this AD for that side only.

Alternative Methods of Compliance (AMOCs)

    (k)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, has the authority to approve AMOCs for this AD, if requested in 
accordance with the procedures found in 14 CFR 39.19.
    (2) To request a different method of compliance or a different 
compliance time for this AD, follow the procedures in 14 CFR 39.19. 
Before using any approved AMOC on any airplane to which the AMOC 
applies, notify your appropriate principal inspector (PI) in the FAA 
Flight Standards District Office (FSDO), or lacking a PI, your local 
FSDO.

    Issued in Renton, Washington, on August 17, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E7-17284 Filed 8-30-07; 8:45 am]

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