
[Federal Register: April 14, 2008 (Volume 73, Number 72)]
[Rules and Regulations]               
[Page 19986-19989]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr14ap08-13]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-29062; Directorate Identifier 2007-NM-020-AD; 
Amendment 39-15462; AD 2008-08-10]
RIN 2120-AA64

 
Airworthiness Directives; Boeing Model 737-100, -200, -200C, -
300, -400, and -500 Series Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: We are adopting a new airworthiness directive (AD) for all 
Boeing Model 737-100, -200, -200C, -300, -400, and -500 series 
airplanes. For certain airplanes, this AD requires replacing the 
outboard stabilizing fitting and certain adjacent components of the 
main landing gear (MLG) support beam. This AD also requires repetitive 
inspections for discrepancies of the outboard stabilizing fitting, 
walking beam hanger, and rear spar attachment, and corrective actions 
if necessary. For certain airplanes, this AD provides an alternative 
one-time inspection of the outboard stabilizing fitting for 
discrepancies, and corrective actions if necessary, which would extend 
the compliance time for the replacement of the outboard stabilizing 
fitting. For certain other airplanes, this AD also requires performing 
a torque check of the aft pin of the outboard stabilizing fitting, and 
corrective actions if necessary. This AD results from reports of 
findings of fatigue cracking of the outboard stabilizing fitting and 
stress corrosion cracking of the bolts attaching the fitting to the 
wing rear spar. We are issuing this AD to detect and correct that 
cracking, which could result in disconnection of the MLG actuator from 
the rear spar and support beam, consequent damage to the hydraulic 
system, and possible loss of the ``A'' and ``B'' hydraulic systems and 
damage or jamming of the flight control cables. Damage or jamming of 
the flight control cables could result in loss of control of the 
airplane.

DATES: This AD is effective May 19, 2008.
    The Director of the Federal Register approved the incorporation by 
reference of certain publications listed in this AD as of May 19, 2008.

ADDRESSES: For service information identified in this AD, contact 
Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 
98124-2207.

Examining the AD Docket

    You may examine the AD docket on the Internet at http://
www.regulations.gov; or in person at the Docket Management Facility 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The AD docket contains this AD, the regulatory evaluation, 
any comments received, and other information. The address for the 
Docket Office (telephone 800-647-5527) is the Document Management 
Facility, U.S. Department of Transportation, Docket Operations, M-30, 
West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., 
Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Nancy Marsh, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 
917-6440; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Discussion

    We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR 
part 39 to include an airworthiness directive (AD) that would apply to 
all Boeing Model 737-100, -200, -200C, -300, -400, and -500 series 
airplanes. That NPRM was published in the Federal Register on August 
31, 2007 (72 FR 50278). For certain airplanes, that NPRM proposed to 
require replacing the outboard stabilizing fitting and certain adjacent 
components of the main landing gear (MLG) support beam. That NPRM also 
proposed to require repetitive inspections for discrepancies of the 
outboard stabilizing fitting, walking beam hanger, and rear spar 
attachment, and corrective actions if necessary. For certain airplanes, 
that NPRM proposed to provide an alternative one-time inspection of the 
outboard stabilizing fitting for discrepancies and corrective actions 
if necessary, which would extend the compliance time for the 
replacement of the outboard stabilizing fitting. For certain other 
airplanes, that NPRM proposed to require performing a torque check of 
the aft pin of the outboard stabilizing fitting, and corrective actions 
if necessary.

Comments

    We gave the public the opportunity to participate in developing 
this AD. We considered the comments received from the commenters.

Request To Change the Description of the Unsafe Condition

    Boeing asks that we change the description of the unsafe condition 
specified in the Summary and Discussion sections and in paragraph (d) 
of the AD. Boeing states that, Model 737-100, -200, -300, -400, and -
500 airplanes are equipped with ``A'' and ``B'' hydraulic systems, and 
an additional standby hydraulic system. Boeing notes that fracture or 
disconnect of any of the structural parts specified in Boeing Alert 
Service Bulletin 737-57A1266, Revision 1, dated January 3, 2007 
(referenced in the NPRM as the source of service information for 
accomplishing the actions), could result in damage to the ``A'' and 
``B'' hydraulic system tubes and damage or jamming of the flight 
control cables. Boeing adds that the standby hydraulic system is 
protected from any damage from a fracture or disconnect of any of the 
structural parts because it is not in the affected area. Additionally, 
Boeing states that if the ``A'' and ``B'' hydraulic systems fail, the 
standby system and manual reversion enable control of the airplane. 
Therefore, Boeing asks that the description of the unsafe condition be 
changed as follows: We are issuing this AD to detect and correct that 
cracking, which could result in disconnection of the MLG actuator from 
the rear spar and support beam, and consequent damage to the hydraulic 
system, and possible loss of the ``A'' and ``B'' hydraulic systems and 
damage or jamming of the flight control cables. Damage or jamming of 
the flight control cables could lead to a possible loss of control of 
the airplane.
    We agree with Boeing and have changed the description of the unsafe 
condition in the referenced sections as follows: ``We are issuing this 
AD to detect and correct that cracking, which could result in 
disconnection of the MLG actuator from the rear spar and support beam, 
consequent damage to the hydraulic system, and possible loss of the 
``A'' and ``B'' hydraulic systems and damage or jamming of the flight 
control cables. Damage or jamming of the flight control cables could 
result in loss of control of the airplane.'' However, the Discussion 
section is not restated in the final rule; therefore, we have made no 
change to the AD in this regard.

[[Page 19987]]

Request To Clarify Certain Language

    Boeing asks that the term ``titanium pin,'' as specified in the 
Relevant Service Information section, be changed to ``new pin.'' Boeing 
states that the new forward fuse pin is made from 15-5PH CRES stainless 
steel. Boeing also asks that the word ``components,'' also specified in 
the Relevant Service Information section, be changed to ``fuse pin'' to 
avoid ambiguity or possible confusion.
    We agree with Boeing that its suggested changes clarify the 
language; however, the Relevant Service Information section is not 
restated in the final rule. In addition, it is not necessary to further 
change the body of the AD because we already required ``new 
components'' for replacement parts. Therefore, we have made no change 
to the AD in this regard.

Request To Extend Compliance Time

    Air Transport Association (ATA), on behalf of one of its members, 
United Airlines (UAL), asks that the compliance period for paragraphs 
(g) and (h) of the AD be changed from 36 to 48 months to align with 
UAL's Model 737 heavy maintenance visit. The commenters' state that the 
work defined in the NPRM will require jacking and defueling of the 
aircraft, and extensive disassembly of the landing gear. The commenters 
add that these activities are conducive to depot-level maintenance 
only; the UAL heavy maintenance visit is done on a 48-month cycle.
    We do not agree with the requests to revise the compliance time 
from 36 to 48 months. In Boeing Alert Service Bulletin 737-57A1266, 
Revision 1, dated January 3, 2007, the manufacturer recommended that 
the actions be done within 36 months after the release of the service 
bulletin. In developing an appropriate compliance time for this AD, we 
considered the serious nature of the unsafe condition as well as the 
recommendations of the manufacturer, the availability of any necessary 
repair parts, and the practical aspect of accomplishing the required 
inspection within an interval of time that corresponds to the normal 
maintenance schedules of most affected operators. In light of these 
factors, we have determined that the 36-month compliance time, as 
proposed, is appropriate. We do not find it necessary to change the AD 
in this regard. However, under the provisions of paragraph (p) of the 
AD, we will consider approving requests for adjustments to the 
compliance time if data are submitted to substantiate that such an 
adjustment would provide an acceptable level of safety.

Clarification of Paragraph Reference

    We have changed the paragraph reference in paragraph (n) of the 
NPRM for clarification. Paragraph (n) specifies that accomplishment of 
the replacement of the tube assembly before the effective date of this 
AD is acceptable for compliance with the replacement specified in 
paragraph (l) of the NPRM; however, the correct reference is paragraph 
(m) of this AD.

Conclusion

    We reviewed the relevant data, considered the comments received, 
and determined that air safety and the public interest require adopting 
the AD with the changes described previously. We also determined that 
these changes will not increase the economic burden on any operator or 
increase the scope of the AD.

Costs of Compliance

    There are about 3,130 airplanes of the affected design in the 
worldwide fleet. This AD affects about 1,380 airplanes of U.S. 
registry.
    For all airplanes: The replacement takes between 20 and 24 work 
hours per airplane to do, depending on the airplane's configuration, at 
an average labor rate of $80 per work hour. Required parts will cost 
between $3,658 and $4,272 per airplane, depending on the airplane's 
configuration. Based on these figures, the estimated cost of the 
replacement is estimated to be up to between $7,256,040 and $8,544,960, 
or between $5,258 and $6,192 per airplane, depending on the airplane's 
configuration.
    For Groups 1 through 8 airplanes: The alternative inspection, if 
done, takes about 12 work hours per airplane to do, at an average labor 
rate of $80 per work hour. Based on these figures, the estimated cost 
of the alternative inspection is estimated to be up to $1,324,800, or 
$960 per airplane.
    For Group 9 airplanes: The general visual inspection takes about 2 
work hours per airplane to do, at an average labor rate of $80 per work 
hour. Based on these figures, the estimated cost of the general visual 
inspection is estimated to be up to $220,800, or $160 per airplane.
    For Groups 1 through 5 airplanes that had steel pins replaced per 
the original issue of the service bulletin: The torque check takes 
about 7 work hours per airplane to do, at an average labor rate of $80 
per work hour. Based on these figures, the estimated cost of the torque 
check is estimated to be up to $772,800, or $560 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

    This AD will not have federalism implications under Executive Order 
13132. This AD will 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 this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Is not a ``significant rule'' under 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.
    You can find our regulatory evaluation and the estimated costs of 
compliance in the AD Docket.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

0
Accordingly, under the authority delegated to me by the Administrator, 
the FAA amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
1. The authority citation for part 39 continues to read as follows:


[[Page 19988]]


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


Sec.  39.13  [Amended]

0
2. The FAA amends Sec.  39.13 by adding the following new AD:

2008-08-10 Boeing: Amendment 39-15462. Docket No. FAA-2007-29062; 
Directorate Identifier 2007-NM-020-AD.

Effective Date

    (a) This airworthiness directive (AD) is effective May 19, 2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to all Model 737-100, -200, -200C, -300, -
400, and -500 series airplanes, certificated in any category.

Unsafe Condition

    (d) This AD results from reports of findings of fatigue cracking 
of the outboard stabilizing fitting and stress corrosion cracking of 
the bolts attaching the fitting to the wing rear spar. We are 
issuing this AD to detect and correct that cracking, which could 
result in disconnection of the MLG actuator from the rear spar and 
support beam, consequent damage to the hydraulic system, and 
possible loss of the ``A'' and ``B'' hydraulic systems and damage or 
jamming of the flight control cables. Damage or jamming of the 
flight control cables could result in loss of control 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 Reference

    (f) The term ``alert service bulletin'' as used in this AD, 
means the Accomplishment Instructions of Boeing Alert Service 
Bulletin 737-57A1266, Revision 1, dated January 3, 2007.

Replacement/Repetitive Inspections

    (g) For airplanes identified as Groups 1 through 8, as specified 
in the alert service bulletin, except as provided by paragraphs (h) 
and (k) of this AD: Within 36 months after the effective date of 
this AD, replace the outboard stabilizing fitting, H-11 bolts, 
forward pin, and aft pin, as applicable, with new components by 
doing all the applicable actions in accordance with Part II of the 
alert service bulletin, except as provided by paragraph (j) of this 
AD. Within 120 months after accomplishing the replacement, do a 
general visual inspection for discrepancies of the outboard 
stabilizing fitting, walking beam hanger, and rear spar attachment 
fitting, and do all applicable corrective actions, by doing all the 
actions, except as provided by paragraph (j) of this AD, in 
accordance with Part V of the alert service bulletin. Do all 
corrective actions before further flight. Repeat the inspection at 
intervals not to exceed 120 months.

Alternative Inspection

    (h) For airplanes identified as Groups 1 through 8, as specified 
in the alert service bulletin, on which the existing H-11 bolts were 
replaced before the effective date of this AD with Inconel 718 
bolts, in lieu of doing the actions required by paragraph (g) of 
this AD: Within 4,500 flight cycles or 36 months after the effective 
date of this AD, whichever is later, do a magnetic test of the 
attach bolts in accordance with the alert service bulletin. If any 
bolt is magnetic, discontinue the alternative inspection specified 
in the alert service bulletin and accomplish the actions required by 
paragraph (g) before further flight. If none of the bolts are 
magnetic, do all the applicable actions in accordance with Part I of 
the alert service bulletin before further flight.
    (1) If any crack is found: Stop the inspection and before 
further flight do the actions required by paragraph (g) of this AD. 
Repetitive inspections must be done after replacing the fitting at 
the interval specified in paragraph (g) of this AD.
    (2) If no crack is found: Before further flight, replace the 
forward pin and aft pin, as applicable, in accordance with the alert 
service bulletin, and within 60 months after the effective date of 
this AD, do the remaining replacement required by paragraph (g) of 
this AD. Repetitive inspections must be done after replacing the 
fitting at the interval specified in paragraph (g) of this AD.
    (3) If damage other than cracking is found, or if the fitting 
lug hole is beyond hole size limits, before further flight, repair 
using a method approved in accordance with the procedures specified 
in paragraph (p) of this AD.

General Visual Inspection

    (i) For airplanes identified as Group 9, as specified in the 
alert service bulletin: Within 36 months or 4,500 flight cycles 
after the effective date of this AD, whichever occurs later, do a 
general visual inspection of the outboard stabilizing fitting and 
fasteners for discrepancies, and do all applicable corrective 
actions in accordance with Part IV of the alert service bulletin, 
except as provided by paragraphs (j) and (k) of this AD. Within 120 
months after the inspection specified in Part IV has been done, do a 
general visual inspection for discrepancies of the outboard 
stabilizing fitting, walking beam hanger and rear spar attachment 
fitting in accordance with Part V of the alert service bulletin, and 
do all applicable corrective actions in accordance with Part V of 
the alert service bulletin, except as provided by paragraphs (j) and 
(k). Do all applicable corrective actions before further flight. 
Repeat the Part V inspection at intervals not to exceed 120 months.

Exceptions To Alert Service Bulletin Specifications

    (j) During any inspection required by this AD, if any corrosion 
damage is found that cannot be removed, or if any damage is found 
that is outside the limits specified in the alert service bulletin, 
or if any discrepancy is found and the alert service bulletin 
specifies contacting the manufacturer for disposition of certain 
repair conditions: Before further flight, repair using a method 
approved in accordance with the procedures specified in paragraph 
(p) of this AD.
    (k) Certain sections in Parts I, II, and V of the alert service 
bulletin specify ``For 737-100 and -200 airplanes'' and ``For 737-
300 and -500 airplanes.'' However, those sections are applicable to 
Model 737-100, -200, and -200C airplanes, and Model 737-300, -400, 
and -500 airplanes, respectively.

Torque Check

    (l) For airplanes identified as Groups 1 through 5, as specified 
in the alert service bulletin, on which the aft pin of the aft 
outboard stabilizing fitting was replaced before the effective date 
of this AD, in accordance with Boeing Alert Service Bulletin 737-
57A1266, dated May 8, 2003: Within 36 months after the effective 
date of this AD, do a torque check to determine whether the aft pin 
is correctly installed. Do all applicable corrective actions before 
further flight. Do the actions in accordance with Part III of the 
alert service bulletin.

Concurrent Requirements

    (m) For airplanes identified as Groups 1 and 3, as specified in 
the alert service bulletin: Prior to or concurrently with 
accomplishment of paragraph (g) of this AD, do the replacement of 
the existing tube assembly of the outboard stabilizing fitting as 
specified in Part IV of Boeing Service Bulletin 737-57-1052, 
Revision 4, dated October 24, 1980.

Credit for Previously Accomplished Actions

    (n) Replacement of the tube assembly before the effective date 
of this AD in accordance with Boeing Service Bulletin 737-57-1073, 
Revision 4, dated April 12, 1985, is acceptable for compliance with 
the replacement specified in paragraph (m) of this AD.
    (o) For Groups 1 through 4, as specified in the alert service 
bulletin: Replacement of the H-11 bolts for the inboard stabilizing 
fitting before the effective date of this AD, in accordance with 
Boeing Service Bulletin 737-57-1231, dated December 1, 1994, is 
acceptable for compliance with the replacement of the H-11 bolts 
specified in paragraph (g) of this AD.

Alternative Methods of Compliance (AMOCs)

    (p)(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.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair required by this AD, if it is approved by an 
Authorized Representative for the Boeing Commercial Airplanes 
Delegation Option Authorization Organization who has been authorized 
by the Manager, Seattle ACO, to make those findings. For a repair 
method to be approved, the repair must meet the

[[Page 19989]]

certification basis of the airplane and the approval must 
specifically refer to this AD.

Material Incorporated by Reference

    (q) You must use Boeing Alert Service Bulletin 737-57A1266, 
Revision 1, dated January 3, 2007; and Boeing Service Bulletin 737-
57-1052, Revision 4, dated October 24, 1980; as applicable; to do 
the actions required by this AD, unless the AD specifies otherwise.
    (1) The Director of the Federal Register approved the 
incorporation by reference of this service information under 5 
U.S.C. 552(a) and 1 CFR part 51.
    (2) For service information identified in this AD, contact 
Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 
98124-2207.
    (3) You may review copies of the service information 
incorporated by reference at the FAA, Transport Airplane 
Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the 
National Archives and Records Administration (NARA). For information 
on the availability of this material at NARA, call 202-741-6030, or 
go to: http://www.archives.gov/federal_register/code_of_federal_
regulations/ibr_locations.html.

    Issued in Renton, Washington, on March 24, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-7561 Filed 4-11-08; 8:45 am]

BILLING CODE 4910-13-P
