Document ID: FAA-2008-0612-0001
Agency: faa
Document Type: Rule
Title: Airworthiness Directives; Boeing Model 747 Airplanes
Posted Date: 2008-06-06T04:00Z

[Federal Register: June 6, 2008 (Volume 73, Number 110)]
[Proposed Rules]               
[Page 32246-32248]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr06jn08-12]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0612; Directorate Identifier 2008-NM-059-AD]
RIN 2120-AA64

 
Airworthiness Directives; Boeing Model 747 Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to adopt a new airworthiness directive (AD) for all 
Boeing Model 747 airplanes. This proposed AD would require inspecting 
for cracks in the left- and right-side Stringer 11 longeron adjacent to 
the horizontal stabilizer pivot bulkhead, and related investigative and 
corrective actions if necessary. This proposed AD results from a report 
of a crack found in the right-side Stringer 11 longeron horizontal 
flange, adjacent to the horizontal stabilizer pivot bulkhead, during a 
routine maintenance inspection. We are proposing this AD to detect and 
correct fatigue cracking of the longeron, which can propagate and cause 
damage to the adjacent horizontal stabilizer pivot bulkhead. This 
damage could result in loss of structural integrity and consequent 
inability of the bulkhead to carry flight loads, which could adversely 
affect controllability of the airplane.

DATES: We must receive comments on this proposed AD by July 21, 2008.

ADDRESSES: You may send comments by any of the following methods:
     Federal eRulemaking Portal: Go to http://
www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     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.
     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 proposed 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: Ivan Li, Aerospace Engineer, Airframe

[[Page 32247]]

Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind 
Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6437; 
fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments about this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include ``Docket No. FAA-2008-0612; 
Directorate Identifier 2008-NM-059-AD'' at the beginning of your 
comments. We specifically invite comments on the overall regulatory, 
economic, environmental, and energy aspects of this proposed AD. We 
will consider all comments received by the closing date and may amend 
this proposed 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 proposed AD.

Discussion

    We received a report of a crack found in the right-side Stringer 11 
longeron horizontal flange, adjacent to the horizontal stabilizer pivot 
bulkhead, during a routine maintenance inspection. The airplane had 
accumulated 28,311 total flight hours and 22,070 total flight cycles. 
The crack was visible in the exposed inboard edge of the longeron 
horizontal flange between the upper and lower Station 2598 horizontal 
stabilizer pivot bulkhead splice fittings. After removal of the 
fittings it was revealed that the crack had propagated and completely 
severed the longeron. Boeing analysis indicates that the severed 
longeron was a result of fatigue that had originated from a fastener 
hole in the longeron horizontal flange. Fatigue cracking of the 
longeron can propagate and cause damage to the adjacent horizontal 
stabilizer pivot bulkhead. This condition, if not corrected, could 
result in loss of structural integrity and consequent inability of the 
bulkhead to carry flight loads, which could adversely affect 
controllability of the airplane.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 747-53A2703, dated 
February 14, 2008. The service bulletin describes procedures for a 
surface high frequency eddy current (HFEC) inspection for cracks in the 
left- and right-side Stringer 11 longeron exposed surfaces and edges 
between Stations 2598 and 2607 adjacent to the horizontal stabilizer 
pivot bulkhead, and related investigative and corrective actions if 
necessary. The procedures for the related investigative and corrective 
actions are as follows:
     If any crack is found during the surface HFEC inspection: 
The procedures describe doing a detailed inspection for cracks in the 
adjacent skin panel and Station 2598 of the horizontal stabilizer pivot 
bulkhead structure. If any crack is found in the skin panel or bulkhead 
structure, the crack may be repaired as specified in the 747 structural 
repair manual, or contact Boeing for repair data and repair. After the 
repair is installed, the longeron is replaced with a new longeron.
     If no crack is found during the surface HFEC inspection: 
The procedures describe doing an open hole HFEC inspection of the 
longeron for cracks at the specified fastener hole locations.
     If any crack is found during the open hole HFEC 
inspection: The procedures describe oversizing any cracked hole to 
remove the crack, and the inspection is repeated for any remaining 
cracks. If any crack remains after oversizing the hole to the maximum 
allowed diameter, the longeron is removed and a detailed inspection is 
done for cracks in the adjacent skin panel and Station 2598 of the 
horizontal stabilizer pivot bulkhead structure. If any crack is found 
in the skin panel or bulkhead structure, the crack is repaired as 
specified in the 747 structural repair manual, or the procedures 
recommend contacting Boeing for repair data and repair. After the 
repair is installed, the longeron is replaced with a new longeron. If 
no crack is found, a new longeron is installed.
    The compliance times for the actions in the service bulletin are as 
follows:
     The compliance time for the initial surface HFEC 
inspection is before the accumulation of 20,000 total flight cycles, or 
within 1,500 flight cycles after the date on the service bulletin, 
whichever occurs later. If a new longeron is installed, the inspection 
is repeated before the accumulation of 20,000 flight cycles after the 
installation. If a longeron is repaired, or if no crack is found during 
the surface and open hole HFEC inspections, the applicable inspection 
is repeated at intervals not to exceed 3,000 flight cycles after the 
repair is done.
    The related investigative and corrective actions are to be done 
before further flight after the surface HFEC inspections are done. The 
above compliance times and actions apply to the left and right side 
longerons, independently.

FAA's Determination and Requirements of This Proposed AD

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

Difference Between the Proposed AD and Service Information

    The service bulletin specifies to contact the manufacturer for 
instructions on how to repair certain conditions, but this proposed AD 
would require repairing those conditions in one of the following ways:
     Using a method that we approve; or
     Using data that meet the certification basis of the 
airplane, and that have been approved by an Authorized Representative 
for the Boeing Commercial Airplanes Delegation Option Authorization 
Organization whom we have authorized to make those findings.

Costs of Compliance

    We estimate that this proposed AD would affect 165 airplanes of 
U.S. registry. We also estimate that it would take 3 work-hours per 
product to comply with this proposed AD. The average labor rate is $80 
per work-hour. Based on these figures, we estimate the cost of this 
proposed AD to the U.S. operators to be $39,600, or $240 per product.

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

[[Page 32248]]

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 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 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. 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, 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 FAA amends Sec.  39.13 by adding the following new AD:

Boeing: Docket No. FAA-2008-0612; Directorate Identifier 2008-NM-
059-AD.

Comments Due Date

    (a) We must receive comments by July 21, 2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to all Boeing Model 747-100, 747-100B, 747-
100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 
747-400F, 747SR, and 747SP series airplanes, certificated in any 
category.

Unsafe Condition

    (d) This AD results from a report of a crack found in the right-
side Stringer 11 longeron horizontal flange, adjacent to the 
horizontal stabilizer pivot bulkhead, during a routine maintenance 
inspection. We are issuing this AD to detect and correct fatigue 
cracking of the longeron, which can propagate and cause damage to 
the adjacent horizontal stabilizer pivot bulkhead. This damage could 
result in loss of structural integrity and consequent inability of 
the bulkhead to carry flight loads, which could adversely affect 
controllability of the airplane.

Compliance

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

Inspection/Related Investigative and Corrective Actions

    (f) Except as provided by paragraph (g) of this AD: At the 
applicable times specified in paragraph 1.E. of Boeing Alert Service 
Bulletin 747-53A2703, dated February 14, 2008, do a surface high 
frequency eddy current (HFEC) inspection for cracks in the left- and 
right-side Stringer 11 longeron exposed surfaces and edges between 
Station 2598 and 2607 adjacent to the horizontal stabilizer pivot 
bulkhead; and do all applicable related investigative and corrective 
actions before further flight, in accordance with the Accomplishment 
Instructions of the service bulletin, except as provided by 
paragraph (h) of this AD.

Exception to Compliance Times

    (g) Where Boeing Alert Service Bulletin 747-53A2703, dated 
February 14, 2008, specifies counting the compliance time from ``. . 
. the date on this service bulletin,'' this AD requires counting the 
compliance time from the effective date of this AD.

Exception to Corrective Actions

    (h) If any crack is found during any inspection required by this 
AD, and Boeing Alert Service Bulletin 747-53A2703, dated February 
14, 2008, specifies to contact Boeing for appropriate action: Before 
further flight, repair using a method approved in accordance with 
the procedures specified in paragraph (i) of this AD.

Alternative Methods of Compliance (AMOCs)

    (i)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, ATTN: Ivan Li, Aerospace Engineer, Airframe Branch, ANM-120S, 
FAA, Seattle ACO, 1601 Lind Avenue, SW., Renton, Washington 98057-
3356; telephone (425) 917-6437; fax (425) 917-6590 has the authority 
to approve AMOCs for this AD, if requested using 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 certification basis 
of the airplane.

    Issued in Renton, Washington, on May 29, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-12712 Filed 6-5-08; 8:45 am]

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