
[Federal Register: August 7, 2008 (Volume 73, Number 153)]
[Proposed Rules]               
[Page 45895-45898]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr07au08-17]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0846; Directorate Identifier 2008-NM-045-AD]
RIN 2120-AA64

 
Airworthiness Directives; Boeing Model 757-200, 757-200PF, and 
757-300 Series 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 
certain Boeing Model 757-200, 757-200PF, and 757-300 series airplanes. 
This proposed AD would require, for certain airplanes, measuring the 
electrical bond resistance at certain stations and doing any applicable 
repair; installing support brackets for the hot short protector and new 
support clamps for the wire bundles; installing the equipment of the 
hot short protector; and modifying an existing wire bundle and 
installing a new wire bundle. This proposed AD would also require, for 
certain other airplanes, measuring the electrical bond resistance at 
certain stations, measuring the electrical bonding resistance between 
the hot short protector and rear spar web, and doing any applicable 
repair. This proposed AD also would require revising the Airworthiness 
Limitations section of the Instructions for Continued Airworthiness. 
This proposed AD results from fuel system reviews conducted by the 
manufacturer. We are proposing this AD to prevent the center fuel tank 
densitometer from overheating and becoming a potential ignition source 
inside the fuel tank, which, in combination with flammable fuel vapors, 
could result in a center fuel tank explosion and consequent loss of the 
airplane.

DATES: We must receive comments on this proposed AD by September 22, 
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: Jen Pei, Aerospace Engineer, Systems 
and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone 
(425) 917-6409; fax (425) 917-6590.

SUPPLEMENTARY INFORMATION:

[[Page 45896]]

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-2008-0846; 
Directorate Identifier 2008-NM-045-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

    The FAA has examined the underlying safety issues involved in fuel 
tank explosions on several large transport airplanes, including the 
adequacy of existing regulations, the service history of airplanes 
subject to those regulations, and existing maintenance practices for 
fuel tank systems. As a result of those findings, we issued a 
regulation titled ``Transport Airplane Fuel Tank System Design Review, 
Flammability Reduction and Maintenance and Inspection Requirements'' 
(66 FR 23086, May 7, 2001). In addition to new airworthiness standards 
for transport airplanes and new maintenance requirements, this rule 
included Special Federal Aviation Regulation No. 88 (``SFAR 88,'' 
Amendment 21-78, and subsequent Amendments 21-82 and 21-83).
    Among other actions, SFAR 88 requires certain type design (i.e., 
type certificate (TC) and supplemental type certificate (STC)) holders 
to substantiate that their fuel tank systems can prevent ignition 
sources in the fuel tanks. This requirement applies to type design 
holders for large turbine-powered transport airplanes and for 
subsequent modifications to those airplanes. It requires them to 
perform design reviews and to develop design changes and maintenance 
procedures if their designs do not meet the new fuel tank safety 
standards. As explained in the preamble to the rule, we intended to 
adopt airworthiness directives to mandate any changes found necessary 
to address unsafe conditions identified as a result of these reviews.
    In evaluating these design reviews, we have established four 
criteria intended to define the unsafe conditions associated with fuel 
tank systems that require corrective actions. The percentage of 
operating time during which fuel tanks are exposed to flammable 
conditions is one of these criteria. The other three criteria address 
the failure types under evaluation: single failures, single failures in 
combination with a latent condition(s), and in-service failure 
experience. For all four criteria, the evaluations included 
consideration of previous actions taken that may mitigate the need for 
further action.
    We have determined that the actions identified in this AD are 
necessary to reduce the potential of ignition sources inside fuel 
tanks, which, in combination with flammable fuel vapors, could result 
in fuel tank explosions and consequent loss of the airplane.
    Boeing has found that no separation was provided for the fuel 
quantity indication system (FQIS) wires. A potential hot short of the 
FQIS lead wire could cause the densitometer in the center fuel tank to 
overheat. In situations where the fuel level in the center fuel tank is 
low, the overheated densitometer could ignite flammable fuel vapors 
inside the center fuel tank. This condition, if not corrected, could 
result in a center fuel tank explosion and consequent loss of the 
airplane.

Other Related Rulemaking

    On April 29, 2008, we issued AD 2008-10-11, amendment 39-15517 (73 
FR 25974, May 8, 2008), applicable to all Boeing Model 757 airplanes. 
That AD requires revising the Airworthiness Limitations (AWLs) section 
of the Instructions for Continued Airworthiness (ICA) by incorporating 
new limitations for fuel tank systems to satisfy SFAR 88 requirements. 
That AD also requires the initial inspection of certain repetitive AWL 
inspections to phase in those inspections, and repair if necessary. 
That AD resulted from a design review of the fuel tank systems. We 
issued that AD to prevent the potential for ignition sources inside 
fuel tanks caused by latent failures, alterations, repairs, or 
maintenance actions, which, in combination with flammable fuel vapors, 
could result in a fuel tank explosion and consequent loss of the 
airplane. Incorporating AWL No. 28-AWL-22 into the AWLs section of the 
ICA in accordance with paragraph (g)(3) of AD 2008-10-11 would 
terminate the action in paragraph (h) of this proposed AD.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 757-28A0085, 
Revision 2, dated December 11, 2007. The service bulletin describes the 
following procedures:
     For certain airplanes: Measuring the electrical bonding 
resistance between the stiffeners located at inboard rear spar station 
(IRSS) 164.9 and IRSS 179.2 and the rear spar web, and doing any 
applicable repair; installing the support brackets of the hot short 
protector (HSP) and the new support clamps of the wire bundles; 
installing the equipment of the HSP; and modifying the existing wire 
bundle and installing a new wire bundle (includes re-routing).
     For certain other airplanes: Measuring the electrical 
bonding resistance between the stiffeners located at IRSS 164.9 and 
IRSS 179.2 and the rear spar web, measuring the electrical bonding 
resistance between the HSP and the rear spar web, and doing any 
applicable repair.
    We have also reviewed section 9, Revision November 2007, of the 
Boeing 757 Maintenance Planning Data (MPD) Document, D622N001-9 
(hereafter referred to as ``the MPD''). Subsection G ``AIRWORTHINESS 
LIMITATIONS--FUEL SYSTEM AWLs'' of the MPD describes AWLs for fuel tank 
systems and includes AWL No. 28-AWL-22, which is the critical design 
configuration control limitation to maintain the design features of the 
center fuel tank's HSP during its replacement.

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 information described previously.

Costs of Compliance

    We estimate that this proposed AD would affect 433 airplanes of 
U.S. registry. The following table provides the estimated costs for 
U.S. operators to comply with this proposed AD.

[[Page 45897]]



                                                                     Estimated Costs
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                                                    Average                                                          Number of
                                           Work      labor                                                             U.S.-
                Action                    hours     rate per           Parts 1               Cost per product 1     registered        Fleet cost 1
                                                      hour                                                           airplanes
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Groups 1-3; measurement,                        8        $80  Between $14,110 and        Between $14,750 and               433  Between $6,386,750 and
 installations, and modification.                              $14,215.                   $14,855.                               $6,432,215.
Group 4; measurements.................          2         80  None.....................  $160.....................         433  $69,280.
AWL Revision..........................          1         80  None.....................  $80......................         433  $34,640.
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\1\ Depending on airplane configuration.

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-2008-0846; Directorate Identifier 2008-NM-
045-AD.

Comments Due Date

    (a) We must receive comments by September 22, 2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 757-200, 757-200PF, and 757-
300 series airplanes, certificated in any category; as identified in 
Boeing Alert Service Bulletin 757-28A0085, Revision 2, dated 
December 11, 2007.

    Note 1:
    This AD requires revisions to certain operator maintenance 
documents to include new inspections. Compliance with these 
inspections is required by 14 CFR 91.403(c). For airplanes that have 
been previously modified, altered, or repaired in the areas 
addressed by these inspections, the operator may not be able to 
accomplish the inspections described in the revisions. In this 
situation, to comply with 14 CFR 91.403(c), the operator must 
request approval for an alternative method of compliance (AMOC) 
according to paragraph (l) of this AD. The request should include a 
description of changes to the required inspections that will ensure 
the continued operational safety of the airplane.

Unsafe Condition

    (d) This AD results from fuel system reviews conducted by the 
manufacturer. We are issuing this AD to prevent the center fuel tank 
densitometer from overheating and becoming a potential ignition 
source inside the fuel tank, which, in combination with flammable 
fuel vapors, could result in a center fuel tank explosion and 
consequent loss of the airplane.

Compliance

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

Measurement, Installation, Modifications, Replacement, and Repair

    (f) For Groups 1 through 3 airplanes, as identified in Boeing 
Alert Service Bulletin 757-28A0085, Revision 2, dated December 11, 
2007: Within 60 months after the effective date of this AD, do the 
measurement, installations, modifications, replacement, and 
applicable repair by accomplishing all the applicable actions 
specified in the Accomplishment Instructions of the service 
bulletin. Do the applicable repair before further flight.

Measure and Repair

    (g) For Group 4 airplanes, as identified in Boeing Alert Service 
Bulletin 757-28A0085, Revision 2, dated December 11, 2007: Within 60 
months after the effective date of this AD, do the measurements and 
applicable repair by accomplishing all the applicable actions 
specified in the Accomplishment Instructions of the service 
bulletin. Do the applicable repair before further flight.

Airworthiness Limitations (AWLs) Revision for AWL No. 28-AWL-22

    (h) Concurrently with accomplishing the actions required by 
paragraphs (f) and (g) of this AD, revise the AWLs section of the 
Instructions for Continued Airworthiness (ICA) by incorporating AWL 
No. 28-AWL-22 of Subsection G of section 9, Revision November 2007, 
Boeing 757 Maintenance Planning Data (MPD) Document, D622N001-9.

No Alternative Critical Design Configuration Control Limitations 
(CDCCLs)

    (i) After accomplishing the action specified in paragraph (h) of 
this AD, no alternative CDCCLs may be used unless the CDCCLs are 
approved as an AMOC in accordance with the procedures specified in 
paragraph (k) of this AD.

Credit for Actions Done According to Previous Issue of the Service 
Bulletin

    (j) Actions done before the effective date of this AD in 
accordance with Boeing Alert Service Bulletin 757-28A0085, Revision 
1, dated April 16, 2007, are acceptable for compliance with the 
requirements of paragraphs (f) and (g) of this AD.

[[Page 45898]]

Terminating Action for AWLs Revision

    (k) Incorporating AWL No. 28-AWL-22 into the AWLs section of the 
ICA in accordance with paragraph (g)(3) of AD 2008-10-11, amendment 
39-15517, terminates the action in paragraph (h) of this AD.

Alternative Methods of Compliance (AMOCs)

    (l)(1) The Manager, Seattle ACO, FAA, ATTN: Jen Pei, Aerospace 
Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle ACO, 
1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone 
(425) 917-6409; 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.

    Issued in Renton, Washington, on July 29, 2008.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-18222 Filed 8-6-08; 8:45 am]

BILLING CODE 4910-13-P
