[Federal Register Volume 71, Number 101 (Thursday, May 25, 2006)]
[Proposed Rules]
[Pages 30074-30078]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-8007]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2006-24877; Directorate Identifier 2005-NM-253-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747-100, 747-100B, 747-
200B, 747-200C, 747-200F, 747SR, and 747SP Series Airplanes

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

ACTION: Notice of proposed rulemaking (NPRM).

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[[Page 30075]]

SUMMARY: The FAA proposes to supersede an existing airworthiness 
directive (AD) that applies to certain Boeing Model 747 series 
airplanes. The existing AD currently requires repetitive inspections to 
detect cracks at certain stringer fastener locations; and repair, if 
necessary. For certain airplanes, the existing AD requires a 
modification in certain areas where reports indicate that cracking was 
prevalent. This modification terminates the repetitive inspections only 
for those areas, and is also an option for other airplanes affected by 
the existing AD. This proposed AD would require one-time inspections at 
a reduced inspection threshold of areas that may have Alodine-coated 
rivets installed, and repair if necessary. This proposed AD results 
from a report of cracking discovered in a skin lap joint that was 
previously inspected using the eddy current method. We are proposing 
this AD to prevent rapid decompression of the airplane due to 
disbonding and subsequent cracking of the skin panels.

DATES: We must receive comments on this proposed AD by July 10, 2006.

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: Docket Management Facility; U.S. Department of 
Transportation, 400 Seventh Street, SW., Nassif Building, room PL-401, 
Washington, DC 20590.
     Fax: (202) 493-2251.
     Hand Delivery: Room PL-401 on the plaza level of the 
Nassif Building, 400 Seventh Street, SW., 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 service information identified in this 
proposed AD.

FOR FURTHER INFORMATION CONTACT: Nicholas Kusz, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
917-6432; 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 ``Docket No. 
FAA-2006-24877; Directorate Identifier 2005-NM-253-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 the DOT's complete Privacy Act Statement in the 
Federal Register published on April 11, 2000 (65 FR 19477-78), or may 
can visit http://dms.dot.gov.

Examining the Docket

    You may examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility office 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The Docket Management Facility office (telephone (800) 647-
5227) is located on the plaza level of the Nassif 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

    On December 3, 1990, we issued AD 90-26-10, amendment 39-6836 (55 
FR 51401, December 14, 1990), for certain Boeing Model 747 series 
airplanes. That AD requires repetitive inspections to detect cracks at 
certain stringer fastener locations; and repair, if necessary. For 
certain airplanes, AD 90-26-10 requires a modification in certain areas 
where reports indicate that cracking was prevalent. This modification 
terminates the repetitive inspections only for those areas. That AD 
resulted from reports of multiple longitudinal skin cracks. We issued 
that AD to prevent rapid decompression of the airplane.

Actions Since Existing AD Was Issued

    Since 1985, Boeing has incorporated rivets coated with Alodine into 
production fuselage aluminum skins and post-production skin 
modification kits. Alodine coating on rivets provides a protective 
chemical conversion coating, but also increases electrical 
conductivity. Certain non-destructive inspection (NDI) methods rely on 
disruptions in the electromagnetic field around cracks in metallic 
structures to detect cracking. One such NDI method is the sliding probe 
eddy current inspection, which was one inspection method required by AD 
90-26-10. Conductivity of the Alodine-coated rivet could be strong 
enough to mask cracking in the fastener hole during eddy current 
inspections.
    Since we issued AD 90-26-10, cracking was discovered in a skin lap 
joint that was previously inspected using the eddy current method. The 
cracking was discovered during a full-scale fatigue test on a Model 737 
fuselage. The skin lap joints on Model 737 airplanes are similar to 
those on the affected Model 747 airplanes.
    The manufacturer has accomplished a comprehensive study of the 
effect of Alodine-coated rivets on all Boeing Airplane models. Based on 
the critical nature of the sliding probe eddy current inspection 
method, this study indicates that two existing ADs, AD 96-23-02 and AD 
90-26-10, require further rulemaking. We are proposing this NPRM to 
supersede AD 90-26-10, and Docket No. FAA-2006-24865 to supersede AD 
96-23-02. In addition, based on this study, the FAA does not propose to 
issue other ADs related to Alodine-coated rivets.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 747-53A2321, 
Revision 7, dated October 27, 2005 (the original issue of Boeing Alert 
Service Bulletin 747-53A2321, dated October 31, 1989, was referenced as 
the appropriate source of service information for accomplishing the 
required actions in AD 90-26-10). Revision 7 of the alert service 
bulletin describes the procedures that were required by AD 90-26-10, 
and includes new procedures for a one-time external detailed inspection 
for cracking of the skin area between the lap joints between stringer 6 
and stringer 14, from body station 340 to 520, which is designated as 
Area 1 by the original issue of Boeing Alert Service Bulletin 747-
53A2321; and a new external high-frequency eddy current inspection to 
ensure a thorough inspection for cracking of the areas where Alodine-
coated rivets are installed. Alodine-coated rivets may have been 
installed within Area 1 during accomplishment of a modification 
specified in Boeing Service

[[Page 30076]]

Bulletin 747-53-2275, which was mandated by AD 90-06-06, amendment 39-
6490 (55 FR 8374, March 7, 1990). The modification installed external 
doublers in a small portion of Area 1 and also replaced stringers 
throughout Area 1. The fasteners used for the stringer replacement and 
doubler installation may have been Alodine-coated rivets. However, the 
service bulletin excludes from this inspection those areas covered by 
the modification doublers. Accomplishing the actions specified in the 
service information is intended to adequately address the unsafe 
condition.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to develop on other airplanes of the 
same type design. For this reason, we are proposing this AD, which 
would supersede AD 90-26-10 and would retain the requirements of the 
existing AD. This proposed AD would also require accomplishing the 
actions specified in the alert service bulletin described previously, 
except as discussed under ``Difference Between the Proposed AD and the 
Alert Service Bulletin.''

Difference Between the Proposed AD and the Alert Service Bulletin

    Boeing Alert Service Bulletin 747-53A2321, Revision 7, 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.

Changes to Existing AD

    Paragraphs E. and F. of AD 90-26-10 allow for adjustment to the 
compliance threshold by not counting the flight cycles in which cabin 
differential pressure is at 2.0 pounds per square inch (psi) or less; 
or allow for multiplication by an adjustment factor based on continued 
mixed operation at lower cabin pressure differentials. This proposed AD 
would not allow those adjustments. However, this proposed AD states 
that operators may continue to adjust the repetitive inspection 
interval based on a lower cabin differential pressure until the next 
scheduled inspection. Thereafter, this proposed AD would not allow such 
adjustment. We have determined that an adjustment of flight cycles due 
to a lower cabin differential pressure is not substantiated and will 
not be allowed for use in determining the flight-cycle threshold for 
this proposed AD. There have been several instances on other in-service 
issues where analytical rationales have indicated that pressurization 
cycles of less than 2.0 psi should not be counted. However, when fleet 
records have been examined, the airplanes engaged in such operations 
have the same or greater occurrences of crack findings compared with 
those on which all pressurized flights are counted. As a result, we 
consider such matters based on all available factors, including 
individual operators' specific maintenance programs, technical 
rationale, and fleet experience. We have found that such provisions are 
applicable only to a small number of operators that may not pressurize 
their airplanes above 2.0 psi in all their flights. We have determined 
that the best way to handle such circumstances is for operators to 
request an AMOC in accordance with the procedures in paragraph (n) of 
this proposed AD, rather than by increasing the complexity of the AD by 
addressing each operator's unique situation.
    Boeing has received a Delegation Option Authorization (DOA). We 
have revised this proposed AD to delegate the authority to approve an 
alternative method of compliance for any repair that would be required 
by this proposed AD to the Authorized Representative for the Boeing DOA 
Organization.
    The ``detailed visual inspection'' specified in AD 90-26-10 is 
referred to as a ``detailed inspection'' in this proposed AD. We have 
included the definition for a detailed inspection in a note in the 
proposed AD.
    We have revised the applicability to identify the model 
designations as published in the most recent type certificate data 
sheet for the affected model.
    This proposed AD would retain certain requirements of AD 90-26-10. 
Since AD 90-26-10 was issued, the AD format has been revised, and 
certain Paragraphs have been rearranged. As a result, the corresponding 
Paragraph identifiers have changed in this proposed AD, as listed in 
the following table:

                      Revised Paragraph Identifiers
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                                             Corresponding  requirement
        Requirement in AD 90-26-10              in this  proposed AD
------------------------------------------------------------------------
Paragraph A...............................  Paragraph (f).
Paragraph C...............................  Paragraph (g).
Paragraph D...............................  Paragraph (h).
Paragraph E...............................  Paragraph (i).
Paragraph F...............................  Paragraph (j).
------------------------------------------------------------------------

Costs of Compliance

    There are about 132 airplanes of the affected design in the 
worldwide fleet. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD. This proposed AD would 
affect about 59 airplanes of U.S. registry. The average labor rate is 
$80 per work hour.

                                                 Estimated Costs
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              Action                Work hours           Parts           Cost per airplane        Fleet cost
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Inspection (required by AD 90-26-            48  None.................  $3,840, per          $226,560, per
 10).                                                                    inspection cycle.    inspection cycle.
Modification (required by AD 90-            620  69, 246..............  118,846............  7,011,914.
 26-10).
Inspection (new proposed action).            48  None.................  3,840, per           226,560, per
                                                                         inspection cycle.    inspection cycle.
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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

[[Page 30077]]

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 
removing amendment 39-6836 (55 FR 51401, December 14, 1990) and adding 
the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2006-24877; Directorate Identifier 2005-NM-
253-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by July 10, 
2006.

Affected ADs

    (b) This AD supersedes AD 90-26-10.

Applicability

    (c) This AD applies to Boeing Model 747-100, 747-100B, 747-200B, 
747-200C, 747-200F, 747SR, and 747SP series airplanes, certificated 
in any category; line numbers 001 through 430 inclusive.

Unsafe Condition

    (d) This AD results from a report of cracking discovered in a 
skin lap joint that was previously inspected using the eddy current 
method. We are issuing this AD to prevent rapid decompression of the 
airplane due to disbonding and subsequent cracking of the skin 
panels.

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.

Restatement of Certain Requirements of AD 90-26-10

Inspections

    (f) Prior to the accumulation of 12,000 flight cycles or within 
the next 1,000 flight cycles after January 22, 1991 (the effective 
date of AD 90-26-10), whichever occurs later, unless previously 
accomplished within the last 1,000 flight cycles, conduct an 
external detailed and external high frequency eddy current (HFEC) 
inspection for cracks of the fuselage skin from body station (BS) 
220 to BS 520, left and right hand side of the airplane between 
stringers (S)-6 and S-14, excluding the skin lap joints, in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 747-53A2321, dated October 31, 1989; or Revision 7, 
dated October 27, 2005. After the effective date of this AD, only 
Revision 7 may be used. Doing the inspections in this paragraph in 
accordance with Revision 7 of the service bulletin eliminates the 
need for doing the actions in paragraph (k) of this AD. Repeat the 
inspections thereafter at intervals not to exceed 2,000 flight 
cycles until the terminating modification in paragraph (g) of this 
AD is done, except as provided by paragraph (h) of this AD.


    Note 1: For the purposes of this AD, a detailed inspection is: 
``An intensive examination of a specific item, installation, or 
assembly to detect damage, failure, or irregularity. Available 
lighting is normally supplemented with a direct source of good 
lighting at an intensity deemed appropriate. Inspection aids such as 
mirror, magnifying lenses, etc., may be necessary. Surface cleaning 
and elaborate procedures may be required.''

Terminating Modification

    (g) For airplanes line numbers 001 through 200, prior to the 
accumulation of 20,000 total flight cycles, or within 48 months 
after January 22, 1991, whichever occurs later: Perform the 
terminating modification of the skin panel from BS 340 to BS 520, S-
6 to S-14, in accordance with the Accomplishment Instructions of 
Boeing Alert Service Bulletin 747-53A2321, dated October 31, 1989; 
or Revision 7, dated October 27, 2005. After the effective date of 
this AD, only Revision 7 may be used. The modification consists of 
replacing the skin panel with a new skin panel which was 
manufactured utilizing the improved hot phosphoric anodize bonding 
process.
    (h) Replacement of the skin panel required by paragraph (g) of 
this AD constitutes terminating action for the inspections from BS 
340 to BS 520 required by paragraphs (f) and (k) of this AD. The 
inspections from BS 220 to BS 340 required by paragraph (f) of this 
AD are to be continued.

Adjustments for Cabin Differential Pressure

    (i) Before the effective date of this AD: Flight cycles 
conducted at 2.0 pounds per square inch (psi) or less cabin 
differential pressure need not be counted for the purpose of this 
airworthiness directive.
    (j) Before the effective date of this AD: For Model 747SR 
airplanes only, the threshold and repetitive inspection intervals 
specified herein may be multiplied by the 1.2 adjustment factor 
based on continued mixed operation at lower cabin pressure 
differentials.

New Requirements of This AD

Inspections of Skins With Alodine-Coated Rivets

    (k) For airplanes identified in Figure 9 of the Accomplishment 
Instructions of Boeing Alert Service Bulletin 747-53A2321, Revision 
7, dated October 27, 2005, as requiring additional inspection: 
Within 150 flight cycles after the effective date of this AD, do the 
inspection in paragraph (k)(1) or (k)(2) of this AD in accordance 
with the Accomplishment Instructions of the service bulletin.
    (1) Do an external detailed inspection for cracking of Area 1, 
and repeat the inspection thereafter at intervals not to exceed 150 
flight cycles until one of the actions in paragraph (k)(1)(i), 
(k)(1)(ii), or (k)(1)(iii) is accomplished. Repeat the inspection of 
Area 1 thereafter in accordance with the requirements of paragraph 
(f) of this AD.
    (i) The inspection in accordance with paragraph (k)(1) of this 
AD has been done seven times at intervals not to exceed 150 flight 
cycles. If this option is used: Within 150 flight cycles after the 
seventh inspection, do the inspection required by paragraph (k)(2) 
of this AD.
    (ii) The inspection in accordance with paragraph (k)(2) has been 
accomplished.
    (iii) The inspections in accordance with paragraph (f) of this 
AD has been accomplished once in accordance with Revision 7 of the 
service bulletin.
    (2) Do an external HFEC inspection for cracking of Area 1 in 
accordance with the Accomplishment Instructions of Boeing Alert 
Service Bulletin 747-53A2321, Revision 7, dated October 27, 2005. 
Repeat the HFEC inspection of Area 1 thereafter in accordance with 
the requirements of paragraph (f) of this AD.

[[Page 30078]]

Repair

    (l) If any crack is found during any inspection required by this 
AD: Before further flight, repair in accordance with the 
Accomplishment Instructions of Boeing Alert Service Bulletin 747-
53A2321, dated October 31, 1989; or Revision 7, dated October 27, 
2005. After the effective date of this AD, only Revision 7 of the 
service bulletin may be used. Where Revision 7 of the service 
bulletin specifies to contact Boeing for repair instructions: Before 
further flight, repair using a method approved in accordance with 
the procedures specified in paragraph (n) of this AD.

Adjustments to Compliance Time: Cabin Differential Pressure

    (m) For the purposes of calculating the compliance threshold and 
repetitive interval for actions required by paragraph (f), (g), and 
(k) of this AD, on or after the effective date of this AD: All 
flight cycles, including the number of flight cycles in which cabin 
differential pressure is at 2.0 psi or less, must be counted when 
determining the number of flight cycles that have occurred on the 
airplane, and a 1.2 adjustment factor may not be used. However, for 
airplanes on which the repetitive interval for the actions required 
by paragraphs (f) and (k) of this AD have been calculated in 
accordance with paragraph (i) or (j) of this AD by excluding the 
number of flight cycles in which cabin differential pressure is at 
2.0 pounds psi or less, or by using a 1.2 adjustment factor: 
Continue to adjust the repetitive interval in accordance with 
paragraph (i) or (j) of this AD until the next inspections required 
by paragraph (f) or (k) of this AD are accomplished. Thereafter, no 
adjustment to compliance times based on paragraph (i) or (j) of this 
AD is allowed.

Alternative Methods of Compliance (AMOCs)

    (n)(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) Before using any AMOC approved in accordance with Sec.  
39.19 on any airplane to which the AMOC applies, notify the 
appropriate principal inspector in the FAA Flight Standards 
Certificate Holding District Office.
    (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.
    (4) AMOCs approved previously in accordance with AD 90-26-10 are 
acceptable for compliance with the requirements of this AD, provided 
that any alternative terminating action was not based upon 
inspection results using sliding probe low-frequency eddy current 
(LFEC), sliding probe HFEC, or mid-frequency eddy current (MFEC) 
inspection method; and provided that any alternative method future 
inspections did not incorporate sliding probe LFEC or MFEC 
inspection method.

    Issued in Renton, Washington, on May 16, 2006.
Kevin M. Mullin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E6-8007 Filed 5-24-06; 8:45 am]
BILLING CODE 4910-13-P