
[Federal Register: January 31, 2008 (Volume 73, Number 21)]
[Proposed Rules]               
[Page 5773-5775]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr31ja08-21]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0090; Directorate Identifier 2007-NM-312-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 
certain Boeing Model 747 airplanes. This proposed AD would require 
measuring the electrical bond resistance between the motor operated 
valve (MOV) actuators and airplane structure for the main, center, 
auxiliary, and horizontal stabilizer fuel tanks as applicable, and 
corrective action if necessary. This proposed AD would also require a 
revision to the FAA-approved maintenance program to incorporate 
airworthiness limitation (AWL) No. 28-AWL-21 or AWL No. 28-AWL-27, as 
applicable. This proposed AD results from fuel system reviews conducted 
by the manufacturer. We are proposing this AD to prevent electrical 
current from flowing through a MOV actuator into a fuel tank, which 
could create a potential ignition source inside the fuel tank. This 
condition, in combination with flammable fuel vapors, could result in a 
fuel tank explosion and consequent loss of the airplane.

DATES: We must receive comments on this proposed AD by March 17, 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: Sulmo Mariano, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone 
(425) 917-6501; 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-2008-0090; 
Directorate Identifier 2007-NM-312-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

[[Page 5774]]

with flammable fuel vapors, could result in fuel tank explosions and 
consequent loss of the airplane.
    Boeing has found that, under specific conditions, it is possible 
for electrical current to flow through a motor operated valve (MOV) 
actuator into a fuel tank, which could create a potential ignition 
source inside the fuel tank. This condition, if not corrected, in 
combination with flammable fuel vapors could result in a fuel tank 
explosion and consequent loss of the airplane.

Relevant Service Information

    We have reviewed Boeing Alert Service Bulletin 747-28A2292, dated 
September 14, 2007, for 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. The service bulletin describes procedures 
for measuring the electrical bond resistance between the MOV actuators 
and airplane structure for the main, center, and auxiliary fuel tanks, 
and corrective action if necessary. The corrective action includes 
reworking the index plate and cleaning the surface of the adapter plate 
and airplane structure as necessary.
    We have also reviewed Boeing Alert Service Bulletin 747-28A2294, 
dated September 21, 2007, for Model 747-400 series airplanes equipped 
with an active horizontal stabilizer fuel tank. The service bulletin 
describes procedures for measuring the electrical bond resistance 
between the MOV actuators and airplane structure for the horizontal 
stabilizer fuel tank, and corrective action if necessary. The 
corrective action includes reworking the index plate and cleaning the 
surface of the adapter plate and airplane structure as necessary.
    We have also reviewed the Boeing 747-100/200/300/SP Airworthiness 
Limitations (AWLs) and Certification Maintenance Requirements (CMRs), 
D6-13747-CMR, Revision January 2007 (hereafter referred to as 
``Document D6-13747-CMR''). (For the purposes of Document D6-13747-CMR, 
the Model 747SR series airplane is basically a Model 747-100 series 
airplane with certain modifications to improve fatigue life.) Section D 
of Document D6-13747-CMR describes new AWLs for fuel tank systems. The 
AWLs include:
     AWL inspections, which are periodic inspections of certain 
features for latent failures that could contribute to an ignition 
source.
     Critical design configuration control limitations 
(CDCCLs), which are limitation requirements to preserve a critical 
ignition source prevention feature of the fuel tank system design that 
is necessary to prevent the occurrence of an unsafe condition. The 
purpose of a CDCCL is to provide instruction to retain the critical 
ignition source prevention feature during configuration change that may 
be caused by alterations, repairs, or maintenance actions. A CDCCL is 
not a periodic inspection.
    Section D of Document D6-13747-CMR adds new fuel system AWL No. 28-
AWL-21, which is a CDCCL to maintain the design features of the MOV 
actuator.
    We have also reviewed the Boeing 747-400 Maintenance Planning Data 
(MPD) Document, D621U400-9, Section 9, Revision December 2006 R1 
(hereafter referred to as the ``Boeing 747-400 MPD''). Subsection D of 
the Boeing 747-400 MPD adds new fuel system AWL No. 28-AWL-27, which is 
a CDCCL to maintain the design features of the MOV actuator.

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 the following actions:
     Measuring the electrical bond resistance between the MOV 
actuators and airplane structure for the main, center, auxiliary, and 
horizontal stabilizer fuel tanks as applicable, and corrective action 
if necessary.
     Revising the FAA-approved maintenance program to 
incorporate AWL No. 28-AWL-21, which would require maintaining the 
design features of the MOV actuator on Model 747-100, 747-100B, 747-
100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP 
series airplanes.
     Revising the FAA-approved maintenance program to 
incorporate AWL No. 28-AWL-27, which would require maintaining the 
design features of the MOV actuator on Model 747-400, 747-400D, and 
747-400F series airplanes.

Costs of Compliance

    We estimate that this proposed AD would affect 300 airplanes of 
U.S. registry. The following table provides the estimated costs, at an 
average labor rate of $80 per hour, for U.S. operators to comply with 
this proposed AD.

                                                                     Estimated Costs
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             Action                        Work hours                       Parts                   Cost per product                 Fleet cost
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Measurements....................  Up to 447...................  Up to $350..................  Up to $36,110...............  Up to $10,833,000.
Maintenance program revision....  1...........................  None........................  $80.........................  $24,000.
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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 
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,

[[Page 5775]]

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-2008-0090; Directorate Identifier 2007-NM-
312-AD.

Comments Due Date

    (a) We must receive comments by March 17, 2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to 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; 
as identified in Boeing Alert Service Bulletin 747-28A2292, dated 
September 14, 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 according 
to paragraph (j) 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 electrical current from 
flowing through a motor operated valve (MOV) actuator into a fuel tank, 
which could create a potential ignition source inside the fuel tank. 
This condition, in combination with flammable fuel vapors, could result 
in a fuel tank explosion and consequent loss of the airplane.

Compliance

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

Measurement and Corrective Action

    (f) For all airplanes: Within 60 months after the effective date of 
this AD, measure the electrical bond resistance between the MOV 
actuators and airplane structure for the main, center, and auxiliary 
fuel tanks as applicable, and do all the applicable corrective actions, 
by accomplishing all of the applicable actions specified in the 
Accomplishment Instructions of Boeing Alert Service Bulletin 747-
28A2292, dated September 14, 2007. The corrective actions must be 
accomplished before further flight.
    (g) For Model 747-400 series airplanes identified in paragraph 1.A 
of Boeing Alert Service Bulletin 747-28A2294, dated September 21, 2007: 
Within 60 months after the effective date of this AD, measure the 
electrical bond resistance between the MOV actuators and airplane 
structure for the horizontal stabilizer fuel tanks, and do all the 
applicable corrective actions, by accomplishing all of the applicable 
actions specified in the Accomplishment Instructions of the service 
bulletin. The corrective actions must be accomplished before further 
flight.

Maintenance Program Revision

    (h) For Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 
747-200F, 747-300, 747SR, and 747SP series airplanes: Concurrently with 
accomplishing the actions required by paragraph (f) of this AD, revise 
the FAA-approved maintenance program by incorporating AWL No. 28-AWL-21 
of Section D of the Boeing 747-100/200/300/SP Airworthiness Limitations 
(AWLs) and Certification Maintenance Requirements (CMRs), D6-13747-CMR, 
Revision January 2007. Accomplishing the revision in accordance with a 
later revision of Document D6-13747-CMR is an acceptable method of 
compliance if the revision is approved by the Manager, Seattle Aircraft 
Certification Office (ACO), FAA.
    (i) For Model 747-400, 747-400D, and 747-400F series airplanes: 
Concurrently with accomplishing the applicable actions required by 
paragraph (f) and (g) of this AD, revise the FAA-approved maintenance 
program by incorporating AWL No. 28-AWL-27 of Subsection D of the 
Boeing 747-400 Maintenance Planning Data (MPD) Document, D621U400-9, 
Section 9, Revision December 2006 R1. Accomplishing the revision in 
accordance with a later revision of the MPD is an acceptable method of 
compliance if the revision is approved by the Manager, Seattle ACO, 
FAA.

Alternative Methods of Compliance (AMOCs)

    (j)(1) The Manager, Seattle ACO, FAA, ATTN: Sulmo Mariano, 
Aerospace Engineer, Propulsion Branch, ANM-140S, 1601 Lind Avenue, SW., 
Renton, Washington 98057-3356; telephone (425) 917-6501; 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 January 14, 2008.
Stephen P. Boyd,
Assistant Manager, Transport Airplane Directorate, Aircraft 
Certification Service.
 [FR Doc. E8-1705 Filed 1-30-08; 8:45 am]

BILLING CODE 4910-13-P
