Document ID: FAA-2009-0521-0002
Agency: faa
Document Type: Rule
Title: Airworthiness Directives; Boeing Model 737-300, -400, and -500 Series Airplanes Equipped With a Digital Transient Suppression Device (DTSD) Installed in Accordance With Supplemental Type Certificate (STC) ST00127BO
Posted Date: 2009-06-09T04:00Z

[Federal Register: June 9, 2009 (Volume 74, Number 109)]
[Proposed Rules]
[Page 27254-27257]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr09jn09-7]

========================================================================
Proposed Rules
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains notices to the public of
the proposed issuance of rules and regulations. The purpose of these
notices is to give interested persons an opportunity to participate in
the rule making prior to the adoption of the final rules.

========================================================================

[[Page 27254]]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2009-0521; Directorate Identifier 2008-NM-187-AD]
RIN 2120-AA64

Airworthiness Directives; Boeing Model 737-300, -400, and -500
Series Airplanes Equipped With a Digital Transient Suppression Device
(DTSD) Installed in Accordance With Supplemental Type Certificate (STC)
ST00127BO

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: We propose to adopt a new airworthiness directive (AD) for
certain Boeing Model 737-300, -400, and -500 series airplanes. This
proposed AD would require revising the maintenance program to include
new fuel system limitations for airplanes modified in accordance with
STC ST00127BO. This AD also requires inspections and checks of the
DTSDs and corrective actions, if necessary. This proposed AD results
from fuel system reviews conducted by the manufacturer. We are
proposing this AD to prevent a potential of ignition sources inside
fuel tanks, which, in combination with flammable fuel vapors, could
result in a fuel tank fire or explosion and consequent loss of the
airplane.

DATES: We must receive comments on this proposed AD by July 24, 2009.

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 Goodrich
Corporation, Fuel and Utility Systems, 100 Panton Road, Vergennes,
Vermont 05491-1008; telephone 802-877-4476; e-mail
lgd.TechPubs.Oakville@goodrich.com; Internet http://www.goodrich.com/
TechPubs. You may review copies of the referenced service information
at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW.,
Renton, Washington. For information on the availability of this
material at the FAA, call 425-227-1221 or 425-227-1152.

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: Marc Ronell, Aerospace Engineer, ANE-
150, FAA, Boston Aircraft Certification Office, 12 New England
Executive Park, Burlington, Massachusetts 01803; telephone (781) 238-
7776; fax (781) 238-7170.

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-2009-0521;
Directorate Identifier 2008-NM-187-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 another latent

[[Page 27255]]

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 revising the maintenance program to include
new fuel system limitations for airplanes modified in accordance with
Supplemental Type Certificate (STC) ST00127BO 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.

Relevant Service Information

    We have reviewed Goodrich Instructions for Continued Airworthiness
(ICA) for Boeing Model 737-300/400/500 Airplanes, Document T2007-0010-
0101, Revision D, dated January 16, 2007. The ICA includes Section
2.2.3, ``Scheduled Inspections/Operational Checks,'' and Section 10.1,
``Fuel System Limitations'' (hereafter referred to as ``the
instructions''). These fuel system limitations are identified as
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 instructions to retain the critical ignition source
prevention feature during configuration changes that may be caused by
alterations, repairs, or maintenance actions. A CDCCL is not a periodic
inspection.
    The scheduled inspections/operational checks are periodic
inspections/checks of certain features for latent failures that could
contribute to an ignition source. The instructions describe the
following procedures to detect discrepancies of the following
components of the left wing, right wing, and center tanks:
     Digital transient suppression devices (DTSD): Initial
operational check.
     DTSD safe-side harnesses: Inspection for critical bond
damage, which includes measuring the bonding resistance across the
ground strap and verifying the resistance is less than 2.0 milliohms.
     DTSD safe-side harnesses: Inspection for physical
separation of the harness from other airplane wiring, hydraulic tubing,
structure, control cables, and bleed air ducts. Separation is required
to ensure that threat conditions do not develop that could compromise
the safety of the wiring entering the fuel tank.
    Accomplishing the actions specified in the service information is
intended to adequately address the unsafe condition.

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 revising the maintenance program to
include the scheduled inspections/operational checks specified in
Section 2.2.3 and the fuel system limitations specified in Section 10.1
of the Goodrich ICA for airplanes modified in accordance with STC
ST00127BO, and accomplishing the actions specified in the scheduled
inspections/operational checks and the CDCCLs described previously,
except as described below in ``Differences Between the Instructions and
This Proposed AD.''

Differences Between the Instructions and This Proposed AD

    The instructions do not specify an initial compliance time for
doing the scheduled inspections/operational checks. This proposed AD
would require an operational check of the DTSDs prior to the
accumulation of 39,000 flight hours after modification in accordance
with STC ST00127BO, or within 12 months, whichever occurs later. This
proposed AD would require a general visual inspection for critical bond
damage of the DTSD safe-side harnesses (critical bond damage includes
measuring the bonding resistance across the ground strap and verifying
the resistance is less than 2.0 milliohms) prior to the accumulation of
4,000 flight hours after modification in accordance with STC ST00127BO,
or within 6 months, whichever occurs later. This proposed AD would also
require a general visual inspection for physical separation of the DTSD
safe-side harnesses from other airplane wiring, hydraulic tubing,
structure, control cables, and bleed air ducts prior to the
accumulation of 24,000 flight hours after modification in accordance
with STC ST00127BO, or within 12 months, whichever occurs later.
    The instructions also do not specify corrective actions if any
discrepancy is found. This proposed AD would require that if any
discrepancy is found, applicable corrective actions must be done in
accordance with the applicable section of the Goodrich Aircraft
Maintenance Manual (AMM) Supplement with Wiring Diagrams for 737-300/-
400/-500 FQIS with Goodrich Digital Indicators and Transient
Suppression Device, STC Number: STC ST00127BO, Revision 5, dated
December 20, 2006, as specified in the instructions.

Costs of Compliance

    We estimate that this proposed AD would affect 12 airplanes of U.S.
registry. The following table provides the estimated costs for U.S.
operators to comply with this proposed AD. The average labor rate is
$80 per work hour.

                             Estimated Costs
------------------------------------------------------------------------
                                                  Cost per    Fleet cost
              Action                Work hours  product ($)      ($)
------------------------------------------------------------------------
Revision to maintenance program..            8          640        7,680
Operational check, per cycle.....            1           80          960
Bond damage inspection, per cycle            1           80          960
Separation inspection, per cycle.            1           80          960
------------------------------------------------------------------------

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 27256]]

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, Incorporation by
reference, 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-2009-0521; Directorate Identifier 2008-NM-
187-AD.

Comments Due Date

    (a) We must receive comments by July 24, 2009.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-300, -400, and -500
series airplanes, certificated in any category, equipped with a
digital transient suppression device (DTSD) installed in accordance
with Supplemental Type Certificate (STC) STC ST00127BO.

    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 (m) 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.

Subject

    (d) Air Transport Association (ATA) of America Code 28: Fuel.

Unsafe Condition

    (e) This AD results from fuel system reviews conducted by the
manufacturer. We are issuing this AD to prevent a potential of
ignition sources inside fuel tanks, which in combination with
flammable fuel vapors, could result in a fuel tank fire or explosion
and consequent loss of the airplane.

Compliance

    (f) You are responsible for having the actions required by this
AD performed within the compliance times specified, unless the
actions have already been done.

Revision to the Maintenance Program To Add CDCCLs

    (g) Within 30 days after the effective date of this AD, revise
the maintenance program to incorporate the fuel system limitations
specified in Section 10.1 of the Goodrich Instructions for Continued
Airworthiness (ICA) for Boeing Model 737-300/400/500 Airplanes,
Document T2007-0010-0101, Revision D, dated January 16, 2007.

Revision to the Maintenance Program To Add Scheduled Inspections/
Operational Checks

    (h) Within 30 days after the effective date of this AD: Revise
the maintenance program to incorporate the scheduled inspections/
operational checks specified in Section 2.2.3 of the Goodrich ICA
for Boeing Model 737-300/400/500 Airplanes, Document T2007-0010-
0101, Revision D, dated January 16, 2007; except that the initial
inspections/checks required by paragraphs (i), (j), and (k) of this
AD must be done at the compliance times specified in those
paragraphs. Repeat the inspections/checks thereafter at the
applicable compliance times in the column, ``Frequency,'' of the
table specified in Section 2.2.3 of the Goodrich ICA for Boeing
Model 737-300/400/500 Airplanes, Document T2007-0010-0101, Revision
D, dated January 16, 2007.

Initial Inspections and Repair if Necessary

    (i) Prior to the accumulation of 39,000 flight hours after
modification in accordance with STC ST00127BO, or within 12 months
after the effective date of this AD, whichever occurs later: Do an
operational check of the digital transient suppression devices
(DTSD) in accordance with Section 2.2.3., ``Scheduled Inspections/
Operational Checks,'' of the Goodrich ICA, for Boeing Model 737-300/
400/500 Airplanes, Document T2007-0010-0101, Revision D, dated
January 16, 2007. If the DTSD fails the operational check, repair
before further flight in accordance with the section of the Goodrich
Aircraft Maintenance Manual (AMM) Supplement with Wiring Diagrams
for 737-300/-400/-500 FQIS with Goodrich Digital Indicators and
Transient Suppression Device, STC Number: STC ST00127BO, Revision 5,
dated December 20, 2006, that corresponds to the operational check
specified in Goodrich ICA for Boeing Model 737-300/400/500
Airplanes, Document T2007-0010-0101, Revision D, dated January 16,
2007.
    (j) Prior to the accumulation of 4,000 flight hours after
modification in accordance with STC ST00127BO, or within 6 months
after the effective date of this AD, whichever occurs later: Do a
general visual inspection for critical bond damage of the DTSD safe-
side harnesses (critical bond damage includes measuring the bonding
resistance across the ground strap and verifying the resistance is
less than 2.0 milliohms), in accordance with Section 2.2.3.,
``Scheduled Inspections/Operational Checks,'' of Goodrich ICA for
Boeing Model 737-300/400/500 Airplanes, Document T2007-0010-0101,
Revision D, dated January 16, 2007, which includes Items 5, 6, 7,
and 8 of Table 6 in Section 10.1, ``Fuel System Limitations.'' If
any damage is found, repair before further flight in accordance with
the section of the Goodrich Aircraft Maintenance Manual Supplement
with Wiring Diagrams for 737-300/-400/-500 FQIS with Goodrich
Digital Indicators and Transient Suppression Device, STC Number: STC
ST00127BO, Revision 5, dated December 20, 2006, that corresponds to
the general visual inspection specified in Goodrich ICA for Boeing
Model 737-300/400/500 Airplanes, Document T2007-0010-0101, Revision
D, dated January 16, 2007.
    (k) Prior to the accumulation of 24,000 flight hours after
modification in accordance with STC ST00127BO, or within 12 months
after the effective date of this AD, whichever occurs later: Do a
general visual inspection for physical separation of the DTSD safe-
side harnesses from other airplane wiring, hydraulic tubing,
structure, control cables, and bleed air ducts, in accordance with
Section 2.2.3., ``Scheduled Inspections/Operational Checks,'' of the
Goodrich ICA for Boeing Model 737-300/400/500 Airplanes, Document
T2007-0010-0101, Revision D, dated January 16, 2007. If any damage
is found, repair before further flight in accordance with the
section of the Goodrich Aircraft Maintenance Manual Supplement with
Wiring Diagrams for 737-300/-400/ -500 FQIS with Goodrich Digital
Indicators and Transient Suppression Device, STC Number: STC
ST00127BO, Revision 5, dated

[[Page 27257]]

December 20, 2006, that corresponds to the general visual inspection
specified in Goodrich ICA for Boeing Model 737-300/400/500
Airplanes, Document T2007-0010-0101, Revision D, dated January 16,
2007.

No Alternative Inspections/Checks, Inspection/Check Intervals, or
CDCCLs

    (l) After accomplishing the actions specified in paragraphs (g)
and (h) of this AD, no alternative inspections/checks, inspection/
check intervals, or CDCCLs may be used unless the inspections/
checks, intervals, or CDCCLs are approved as an Alternative Method
of Compliance (AMOC) in accordance with the procedures specified in
paragraph (m) of this AD.

AMOCs

    (m)(1) The Manager, Boston Aircraft Certification Office (ACO),
FAA, has the authority to approve AMOCs for this AD, if requested
using the procedures found in 14 CFR 39.19. Send information to
ATTN: Marc Ronell, Aerospace Engineer, ANE-150, FAA, Boston Aircraft
Certification Office, 12 New England Executive Park, Burlington,
Massachusetts 01803; telephone (781) 238-7776; fax (781) 238-7170.
    (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 principal maintenance inspector (PMI) or
principal avionics inspector (PAI), as appropriate, or lacking a
principal inspector, your local Flight Standards District Office.
The AMOC approval letter must specifically reference this AD.

    Issued in Renton, Washington, on June 2, 2009.
Stephen P. Boyd,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. E9-13494 Filed 6-8-09; 8:45 am]

BILLING CODE 4910-13-P