Document ID: FAA-2008-0148-0001
Agency: faa
Document Type: Rule
Title: Airworthiness Directives; Boeing Model 747 Airplanes
Posted Date: 2008-02-08T05:00Z

[Federal Register: February 8, 2008 (Volume 73, Number 27)]
[Proposed Rules]               
[Page 7486-7488]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr08fe08-15]                         

[[Page 7486]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0148; Directorate Identifier 2007-NM-299-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 a one-time 
inspection of certain fuselage skins at section 41 to find any external 
doublers that cover the inspection areas and to identify the external 
doublers that end on a stringer and those that do not, and related 
investigative and corrective actions if necessary. This proposed AD 
results from reports of cracks found at fastener locations in the 
fuselage skins at section 41. We are proposing this AD to detect and 
correct fuselage skin cracks at fastener locations along the skin-to-
stringer attachments, which could join together and become large and 
consequently result in rapid decompression of the cabin.

DATES: We must receive comments on this proposed AD by March 24, 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 
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-2008-0148; 
Directorate Identifier 2007-NM-299-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 have received two reports of cracks found at fastener locations 
in the fuselage skins at section 41. One operator reported finding skin 
cracks at a fastener location at stringer 5 (S-5) near station (STA) 
365, on a Model 747-200F series airplane. These cracks were found 
during incorporation of the skin modification specified in Boeing 
Service Bulletin 747-53-2272. The cracks were 0.25 inch long and 
located on the forward and aft side of the fastener hole. The airplane 
had accumulated 13,726 total flight cycles. In the other report, 
multiple skin cracks were found during Boeing Model 747-400 series 
airplane fatigue testing. That test article had accumulated 40,000 test 
cycles. The cracks were found at locations where there are no internal 
doublers, at stringers 10 and 13, and between STA 260 and STA 300. 
Fuselage skin cracks at fastener locations along the skin-to-stringer 
attachments, if not corrected, could join together and become large and 
consequently result in rapid decompression of the cabin.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 747-53A2704, dated 
October 4, 2007. The service bulletin describes procedures for doing a 
one-time general visual inspection of certain fuselage skins at section 
41 to find any external doublers that cover the inspection area and to 
identify the external doublers that end on a stringer and those that do 
not; and related investigative and corrective actions if necessary. The 
related investigative actions include the following:
     Removing any external doubler and doing a one-time 
detailed inspection and an open-hole high frequency eddy current (HFEC) 
inspection for any crack in the skin at the skin-to-stringer 
attachments, for an inspection area where the skin-to-stringer 
attachment is covered by an external doubler that ends on a stringer in 
the inspection area.
     Doing repetitive external HFEC inspections for any crack 
in the skin at the skin-to-stringer attachments, for an inspection area 
where the skin-to-stringer attachment is not covered by an external 
doubler.
    For the one-time general visual inspection, one-time detailed 
inspection, one-time open-hole HFEC inspection, and the initial 
external HFEC inspection, the service bulletin specifies a compliance 
time of 16,000 or 25,000 total flight cycles depending on the airplane 
configuration, or 2,000 flight cycles after the date on the service 
bulletin, whichever occurs later. The service bulletin also specifies 
that if a skin panel was replaced, the inspection threshold for the 
affected area can be calculated from the time it was replaced. For the 
repetitive external HFEC inspections, the service bulletin specifies a 
repeat interval of 3,000 flight cycles.
    The corrective actions include repairing any crack found in an 
inspection area, and installing a new external doubler where any 
external doubler has been removed from the inspection area. The service 
bulletin specifies accomplishing the corrective actions before further 
flight.

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(se) same type 
design(s). This proposed AD would require accomplishing the actions 
specified in the service

[[Page 7487]]

information described previously, except as discussed under 
``Differences Between the Proposed AD and Service Bulletin.''

Differences Between Proposed AD and Service Bulletin

    Although Figure 19 of the service bulletin specifies doing a 
``detailed visual inspection'' of the fastener holes, this proposed AD 
would require doing a ``detailed inspection.''
    This proposed AD expands the inspection area at certain skin-to-
stringer attachments. In Figure 3 of the service bulletin, S-5 and S-5A 
from STA 340 to STA 360 should be bold in the illustration to include 
those areas as part of the recommended inspection (similar to Figure 8 
for the right side). Also, in Figure 15 of the service bulletin, S-14A 
from STA 200 to STA 220 should be bold in the illustration to include 
that area as part of the recommended inspection (similar to Figure 17 
for the right side). Boeing is aware of these discrepancies, concurs 
with the changes, and has issued Information Notice (IN) 747-53A2704 IN 
01, dated December 19, 2007, to inform operators of the errors. We have 
included this information in paragraph (g) of this proposed AD.

Clarification of Proposed Requirements

    The service bulletin notes that, at locations where external 
doublers exist that do not end on a stringer in the inspection area, 
repetitive inspections of the skin for cracking at critical rows of 
fasteners are required in accordance with Boeing Document Number D6-
36181, ``Repair Assessment Guidelines--Model 747.'' These inspections 
would not be required by this AD, since compliance is already required 
by sections 91.410, 121.370, 125.248, and 129.32 of the Federal 
Aviation Regulations (14 CFR 91.410, 121.370, 125.248, and 129.32).

Costs of Compliance

    We estimate that this proposed AD would affect 165 airplanes of 
U.S. registry. We also estimate that it would take up to 64 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 $844,800 or $5,120 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 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-2008-0148; Directorate Identifier 2007-NM-
299-AD.

Comments Due Date

    (a) We must receive comments by March 24, 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 reports of cracks found at fastener 
locations in the fuselage skins at section 41. We are issuing this 
AD to detect and correct fuselage skin cracks at fastener locations 
along the skin-to-stringer attachments, which could join together 
and become large and consequently result in rapid decompression of 
the cabin.

Compliance

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

Repetitive Inspections and Related Investigative/Corrective Actions

    (f) At the applicable compliance times specified in Tables 1 and 
2 of paragraph 1.E. of Boeing Alert Service Bulletin 747-53A2704, 
dated October 4, 2007: Do a general visual inspection of the 
fuselage skins at section 41 to find any external doublers that 
cover the inspection area and to identify the external doublers that 
end on a stringer in the inspection area and those that do not, and 
do all the related investigative and corrective actions as 
applicable, by accomplishing all of the applicable actions specified 
in the Accomplishment Instructions of the service bulletin, except 
as provided by paragraph (g) of this AD. Repeat the related 
investigative actions thereafter at the interval specified in Tables 
1 and 2 of the service bulletin, as applicable.

Exceptions to the Service Bulletin

    (g) Where Tables 1 and 2 of paragraph 1.E. of Boeing Alert 
Service Bulletin 747-53A2704, dated October 4, 2007, specify 
counting the compliance time from ``* * * after the date on this 
service bulletin,'' this AD requires counting the compliance time 
from the effective date of this AD. Where Figure 19 of the service 
bulletin specifies doing a ``detailed visual inspection'' for any 
crack at fastener holes common to the stringer, this AD would 
require doing a detailed inspection. In Figure 3 of the service 
bulletin, also inspect the areas at stringer 5 (S-5) and S-5A 
between station (STA) 340 and STA 360 (similar to Figure 8 for the 
right side). In Figure 15 of the service bulletin, also inspect the 
area at S-14A between STA 200 and STA 220 (similar to Figure 17 for 
the right side).

Alternative Methods of Compliance (AMOCs)

    (h)(1) The Manager, Seattle Aircraft Certification Office, FAA, 
ATTN: Ivan Li, Aerospace Engineer, Airframe Branch, ANM-120S, 1601 
Lind Avenue, SW., Renton,

[[Page 7488]]

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, and the approval must specifically refer to this 
AD.

    Issued in Renton, Washington, on January 31, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E8-2352 Filed 2-7-08; 8:45 am]

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