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

[Federal Register Volume 73, Number 140 (Monday, July 21, 2008)]
[Rules and Regulations]
[Pages 42259-42262]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E8-16483]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0733; Directorate Identifier 2008-NM-114-AD; 
Amendment 39-15617; AD 2008-15-05]
RIN 2120-AA64


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

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule; request for comments.

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SUMMARY: We are adopting a new airworthiness directive (AD) for all 
Boeing Model 737-300, -400, and -500 series airplanes. This AD requires 
inspecting to determine if certain carriage spindles are installed, 
repetitive inspections for corrosion and indications of corrosion on 
affected carriage spindles, and if necessary, related investigative 
action and corrective action. This AD also provides optional 
terminating action. This AD results from a report of corrosion found on 
carriage spindles that are located on the outboard trailing edge flaps. 
We are issuing this AD to detect and correct corrosion of the carriage 
spindle, which could result in fracture. Fracture of both the inboard 
and outboard carriage spindles, in the forward ends through

[[Page 42260]]

the large diameters, on a flap, could adversely affect the airplane's 
continued safe flight and landing.

DATES: This AD is effective August 5, 2008.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of August 5, 
2008.
    We must receive comments on this AD by September 19, 2008.

ADDRESSES: You may send comments by any of the following methods:
    <bullet> Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
    <bullet> Fax: 202-493-2251.
    <bullet> 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.
    <bullet> Hand Delivery: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., 
Monday through Friday, except Federal holidays.
    For service information identified in this AD, contact Boeing 
Commercial Airplanes, 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 street address for 
the Docket Office (telephone 800-647-5527) is in the ADDRESSES section. 
Comments will be available in the AD docket shortly after receipt.

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 received a report of corrosion found on carriage spindles that 
are located on the outboard trailing edge flaps. The affected carriages 
were overhauled after February 2006. The carriage sub-assembly had been 
replaced with a new carriage sub-assembly that had a high velocity oxy-
fuel (HVOF) thermal coating applied to the spindle. The HVOF thermal 
coating had flaked off, exposing the base metal and allowing corrosion 
on the spindle. Boeing is examining parts returned from operators to 
find the cause of the coating flaking off. Corrosion of the carriage 
spindle, if not detected and corrected, could result in fracture of the 
spindle. One fractured carriage spindle on a flap can be compensated 
for with pilot inputs to the aileron or rudder, which increases pilot 
workload. Fracture of both the inboard and outboard carriage spindles, 
in the forward ends through the large diameters, on a single flap, 
could adversely affect the airplane's continued safe flight and 
landing.

Relevant Service Information

    We reviewed Boeing Alert Service Bulletin 737-57A1304, dated June 
2, 2008. The service bulletin describes procedures for:
    <bullet> An inspection or maintenance records check to determine if 
a suspect carriage spindle with HVOF thermal coating is installed;
    <bullet> Repetitive detailed inspections for corrosion and for 
potential indications of corrosion such as flaking metallic particles, 
disbonded sealant, or cracked paint or primer of the forward and aft 
ends of the affected carriage spindle (with the option to do a 
borescope inspection instead on the forward end only);
    <bullet> Related investigative actions if potential or no 
indications of corrosion are found; and
    <bullet> Corrective action if a corroded, cracked, or severed 
spindle is found.
    The related investigative actions involve (1) removing the carriage 
to do a detailed inspection of the entire surface of the spindle for 
corrosion if potential indications of corrosion were found or (2) for 
airplanes on which no corrosion indications were found during the 
detailed or optional borescope inspection, doing repetitive gap checks 
for differential movement (with an option to do a non-destructive test 
(NDT) ultrasonic inspection) for cracking that could indicate a severed 
spindle. The corrective action involves replacing a corroded, cracked, 
or severed carriage spindle with a new or serviceable carriage spindle. 
The service bulletin also provides for an optional terminating action 
that involves replacing an HVOF-coated carriage spindle with a non-HVOF 
coated carriage spindle.
    The service bulletin specifies a repetitive interval of 90 days for 
the detailed inspections (including optional borescope inspection) and 
a repetitive interval of 15 days or 150 flight cycles for the gap 
checks (including optional NDT ultrasonic inspections).

FAA's Determination and Requirements of This AD

    We are issuing this AD because we evaluated all the relevant 
information and determined the unsafe condition described previously is 
likely to exist or develop in other products of the(se) same type 
design(s). This AD requires accomplishing the actions specified in the 
service information described previously, except as discussed under 
``Difference Between the AD and the Service Information.''

Interim Action

    This is considered to be interim action. The inspection reports 
that are required by this AD will enable the manufacturer to obtain 
better insight into the nature, cause, and extent of the discrepant 
HVOF coating, and eventually to develop final action to address the 
unsafe condition. Once final action has been identified, the FAA might 
consider further rulemaking.

FAA's Justification and Determination of the Effective Date

    We received a report of corrosion found on carriage spindles that 
are located on the outboard trailing edge flaps. The HVOF coating on 
the affected carriage spindle had flaked off, exposing the base metal. 
Corrosion occurring on the exposed base metal can quickly lead to 
cracking and full fracture of the carriage spindle. Fracture of both 
the inboard and outboard carriage spindles, in the forward ends through 
the large diameters, on a single flap, could adversely affect the 
airplane's continued safe flight and landing. Because of our 
requirement to promote safe flight of civil aircraft and thus, the 
critical need to assure the structural integrity of the carriage 
spindle and the short compliance time involved with this action, this 
AD must be issued immediately.
    Because an unsafe condition exists that requires the immediate 
adoption of this AD, we find that notice and opportunity for prior 
public comment hereon are impracticable and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    This AD is a final rule that involves requirements affecting flight 
safety, and we did not provide you with notice and an opportunity to 
provide your comments before it becomes effective. However, we invite 
you to send any written data, views, or arguments about this AD. Send 
your comments to an address listed under the ADDRESSES section. Include 
``Docket No. FAA-2008-0733; Directorate Identifier 2008-

[[Page 42261]]

NM-114-AD'' at the beginning of your comments. We specifically invite 
comments on the overall regulatory, economic, environmental, and energy 
aspects of this AD. We will consider all comments received by the 
closing date and may amend this AD because of those comments.
    We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We 
will also post a report summarizing each substantive verbal contact we 
receive about this AD.

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:

    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:

2008-15-05 Boeing: Amendment 39-15617. Docket No. FAA-2008-0733; 
Directorate Identifier 2008-NM-114-AD.

Effective Date

    (a) This airworthiness directive (AD) is effective August 5, 
2008.

Affected ADs

    (b) None.

Applicability

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

Unsafe Condition

    (d) This AD results from a report of corrosion found on carriage 
spindles that are located on the outboard trailing edge flaps. We 
are issuing this AD to detect and correct corrosion of the carriage 
spindle, which could result in fracture. Fracture of both the 
inboard and outboard carriage spindles, in the forward ends through 
the large diameters, on a single flap, could adversely affect the 
airplane's continued safe flight and landing.

Compliance

    (e) Comply with this AD within the compliance times specified, 
unless already done.

Inspection To Determine Affected Carriage Spindle

    (f) Within 30 days after the effective date of this AD, inspect 
the carriage sub-assembly to determine whether an affected carriage 
spindle with a high velocity oxy-fuel (HVOF) thermal coating is 
installed, in accordance with the Accomplishment Instructions of 
Boeing Alert Service Bulletin 737-57A1304, dated June 2, 2008. A 
review of airplane maintenance records is acceptable in lieu of this 
inspection if the part number and/or serial number of the carriage 
can be conclusively determined from that review. If no affected 
carriage spindle is installed, no further action is required by this 
paragraph.

Repetitive Inspections, Related Investigative Actions, and Corrective 
Action

    (g) For airplanes on which any affected carriage spindle is 
installed: At the later of the times specified in paragraphs (g)(1) 
and (g)(2) of this AD, do a detailed inspection (or, as an option 
for the forward end of the spindle only, a borescope inspection 
technique may be used) of the spindle for corrosion and potential 
indications of corrosion of the carriage spindle, and do all 
applicable related investigative and corrective actions, in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 737-57A1304, dated June 2, 2008. Do all applicable 
related investigative actions and corrective actions before further 
flight. Repeat the detailed inspection (or, as an option for the 
forward end of the spindle only, the borescope inspection) and 
certain related investigative actions (i.e., the gap-check or 
optional non-destructive test (NDT) ultrasonic inspection) at the 
applicable compliance times specified in the service bulletin.
    (1) Within 30 days after the effective date of this AD.
    (2) Within 90 days after the installation of a new HVOF-coated 
spindle.

    Note 1: Boeing Alert Service Bulletin 737-57A1304, dated June 2, 
2008, references Boeing Alert Service Bulletin 737-57A1277, Revision 
1, dated November 25, 2003, for further information on accomplishing 
the related investigative actions.

Inspection Report

    (h) If any corrosion, cracking, or severed spindle is found 
during any inspection required by paragraph (g) of this AD: Within 
10 days after the inspection, or within 10 days after the effective 
date of this AD, whichever occurs later, submit a report of the 
inspection results to the Manager, Airline Support, Boeing 
Commercial Airlines Group, as specified in Note 2 of paragraph 1.D., 
``Description,'' of Boeing Alert Service Bulletin 737-57A1304, dated 
June 2, 2008. Information collection requirements contained in this 
AD have been approved by the Office of Management and Budget (OMB) 
under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 
et seq.) and have been assigned OMB Control Number 2120-0056.

Optional Terminating Action

    (i) Replacement of an HVOF-coated carriage spindle with a non-
HVOF coated carriage spindle in accordance with Boeing Alert Service 
Bulletin 737-57A1304, dated June 2, 2008, terminates the 
requirements of this AD for that carriage spindle only.

Parts Installation

    (j) As of the effective date of this AD, an HVOF-coated spindle 
may be installed on an airplane provided the actions required by 
paragraph (g) of this AD are done on that spindle.

Alternative Methods of Compliance (AMOCs)

    (k)(1) The Manager, Seattle ACO, FAA, ATTN: Nancy Marsh, 
Aerospace Engineer, Airframe Branch, ANM-120S, 1601 Lind Avenue, 
SW., Renton, Washington 98057-3356; telephone (425) 917-6440; fax 
(425) 917-6590; has the authority to approve AMOCs for this AD, if 
requested, using the procedures found in 14 CFR 39.19.

[[Page 42262]]

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

Material Incorporated by Reference

    (l) You must use Boeing Alert Service Bulletin 737-57A1304, 
dated June 2, 2008, 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 July 10, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-16483 Filed 7-18-08; 8:45 am]
BILLING CODE 4910-13-P

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