Document ID: FAA-2010-0037-0001
Agency: faa
Document Type: Rule
Title: Airworthiness Directives: Boeing Company Model 737-700 (IGW) Series Airplanes Equipped with Auxiliary Fuel Tanks Installed, etc.
Posted Date: 2010-02-12T05:00Z

[Federal Register: February 12, 2010 (Volume 75, Number 29)]
[Proposed Rules]               
[Page 6865-6868]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr12fe10-12]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2010-0037; Directorate Identifier 2009-NM-240-AD]
RIN 2120-AA64

 
Airworthiness Directives; The Boeing Company Model 737-700 (IGW) 
Series Airplanes Equipped With Auxiliary Fuel Tanks Installed in 
Accordance With Configuration 3 of Supplemental Type Certificate 
ST00936NY

AGENCY: Federal Aviation Administration (FAA), DOT.

[[Page 6866]]

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to adopt a new airworthiness directive (AD) for 
certain Model 737-700 (IGW) series airplanes. This proposed AD would 
require deactivation or modification of PATS Aircraft, LLC, auxiliary 
fuel tanks. This proposed AD results from fuel system reviews conducted 
by the manufacturer. We are proposing this AD to prevent 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.

DATES: We must receive comments on this proposed AD by March 29, 2010.

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 proposed AD, contact 
Decrane Aerospace, PATS Aircraft Systems, 21652 Nanticoke Avenue, 
Georgetown, Delaware 19947; telephone 302-253-6157; fax 302-855-0153; 
e-mail giuseppecoppola@decraneaerospace.com; Internet http://
www.decraneaerospace.com. 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: Mazdak Hobbi, Aerospace Engineer, 
Propulsion and Services Branch, ANE-173, FAA, New York Aircraft 
Certification Office, 1600 Stewart Avenue, Suite 410, Westbury, New 
York 11590; telephone (516) 228-7330; fax (516) 794-5531.

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-2010-0037; 
Directorate Identifier 2009-NM-240-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.

Supplemental Type Certificates (STCs) for PATS Aircraft, LLC, Auxiliary 
Fuel Tanks

    The auxiliary fuel tank STC on affected airplanes is of two basic 
type designs: A box-and-bladder type, and a double-walled cylindrical 
type. The box-and-bladder tanks are emptied and vented into the 
airplane center wing tank using either pneumatic air pressure supplied 
from the airplane, or electrical power from the airplane to power fuel 
pumps installed in the tank external dry bay area. The double-walled 
cylindrical tanks use pneumatic air pressure to empty into the airplane 
center wing tank. All auxiliary tanks use some type of electrical fuel 
quantity indication system (FQIS), flight deck control and annunciation 
panels, float level switches, valves and venting systems, electrical 
wiring connections in the dry bay area, and electrical bonding methods.

FAA's Findings

    During the SFAR 88 safety assessment, it was determined that the 
PATS Aircraft, LLC, FQIS and float level switch did not meet 
intrinsically safe electrical energy levels as described in the 
guidelines of Advisory Circular (AC) 25.981-1C, ``Fuel Tank Ignition 
Source Prevention Guidelines.'' PATS Aircraft, LLC, the STC holder, 
identified potential ignition sources resulting from a combination of 
single and latent

[[Page 6867]]

failures for the PATS Aircraft, LLC, fuel tank subsystems. PATS 
Aircraft, LLC, has not complied with the requirements of SFAR 88, 
paragraph 2. To prevent high electrical energy levels from the FQIS and 
float level switch from entering the auxiliary fuel tank, we have 
determined that the appropriate solution for continued use is a 
combination of actions. Installing a transient suppression device (TSD) 
on FQIS and float level switches would be needed. In order to maximize 
wire separation, the TSD must be installed as close as possible to the 
points where the FQIS and float level switch wires exit the TSD and 
enter the auxiliary tank. Other actions might include replacing high-
energy FQISs, and float level switches that are impractical for TSD 
application, with intrinsically safe FQISs, providing wire separation, 
conducting a one-time inspection and/or replacing aging float level 
switch conduit assemblies, periodically inspecting the external dry bay 
system components and wires, and testing the integrity of bonding 
resistances.
    As an alternative to the modification described above, deactivation 
of the auxiliary fuel tanks would adequately address the unsafe 
condition. If operators do not wish to deactivate their auxiliary fuel 
tanks, we will consider requests for alternative methods of compliance 
(AMOCs). The most likely requests would be to allow continued use of 
the tanks by showing compliance with SFAR 88. This would involve 
obtaining STCs to modify the auxiliary fuel tank systems and developing 
maintenance procedures to address the safety issues identified above. 
PATS Aircraft, LLC, as the current STC holder, may be working on AMOCs. 
Operators may contact PATS or propose an AMOC on their own.
    Once an operator has deactivated a tank as proposed by this NPRM, 
the operator might wish to remove the tank. This would require a 
separate design approval, if an approved tank removal procedure does 
not exist.

Relevant Service Information

    We have reviewed Decrane Aerospace Service Bulletins ST00936NY-D-
28-SB-001--K, dated August 25, 2008; and ST00936NY-D-28-SB-021--K, 
dated January 8, 2009; which describe procedures for modifying the 
auxiliary fuel system (AFS). The modification of the auxiliary fuel 
cells of the AFS specified in Decrane Aerospace Service Bulletin 
ST00936NY-D-28-SB-001--K includes removing, repositioning, replacing or 
adding bonding jumpers and/or hardware. The modification of the AFS 
harnesses specified in Decrane Aerospace Service Bulletin ST00936NY-D-
28-SB-021--K includes removing and replacing the auxiliary fuel system 
critical harnesses.

FAA's Determination and Requirements of the Proposed AD

    We have evaluated all pertinent information and identified an 
unsafe condition that is likely to exist or develop on other products 
of this same type design. For this reason, we are proposing this AD, 
which would require deactivation to prevent usage of auxiliary fuel 
tanks, or modification of the auxiliary fuel system.

Costs of Compliance

    We estimate that this proposed AD would affect 11 airplanes of U.S. 
registry. We also estimate that it would take about 250 work-hours per 
product to comply with this proposed AD. The average labor rate is $85 
per work-hour. Required parts would cost about $10,000 per product. 
Based on these figures, we estimate the cost of this proposed AD to the 
U.S. operators to be $343,750, or $31,250 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, 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:

The Boeing Company: Docket No. FAA-2010-0037; Directorate Identifier 
2009-NM-240-AD.

Comments Due Date

    (a) We must receive comments by March 29, 2010.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to The Boeing Company Model 737-700 (IGW) 
series airplanes, certificated in any category; equipped with 
auxiliary fuel tanks installed in accordance with configuration 3 of 
Supplemental Type Certificate ST00936NY.

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. The Federal Aviation Administration is issuing this AD 
to prevent 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.

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.

[[Page 6868]]

Prevent Usage of Auxiliary Fuel Tanks or Modify Auxiliary Fuel System

    (g) Within 45 days after the effective date of this AD: 
Accomplish the requirements specified in paragraph (g)(1) or (g)(2) 
of this AD.
    (1) Deactivate the auxiliary fuel tanks, in accordance with a 
deactivation procedure approved by the Manager, New York Aircraft 
Certification Office (ACO). Any auxiliary tank component that 
remains on the airplane must be secured and must have no effect on 
the continued operational safety and airworthiness of the airplane. 
Deactivation must not result in the need for additional instructions 
for continued airworthiness.

    Note 1: Appendix A of this AD provides criteria that should be 
included in the deactivation procedures. The proposed deactivation 
procedures should be submitted to the Manager, New York ACO, as soon 
as possible to ensure timely review and approval.

    Note 2: For technical information, contact Mazdak Hobbi, 
Aerospace Engineer, Propulsion and Services Branch, ANE-173, FAA, 
New York Aircraft Certification Office (ACO), 1600 Stewart Avenue, 
Suite 410, Westbury, New York 11590; telephone 516-228-7330; fax 
516-794-5531.

    (2) Modify the auxiliary fuel system by doing all the applicable 
actions in accordance with the Accomplishment Instructions of 
Decrane Aerospace Service Bulletin ST00936NY-D-28-SB-001--K, dated 
August 25, 2008; and Decrane Aerospace Service Bulletin ST00936NY-D-
28-SB-021--K, dated January 8, 2009.

Reporting Requirement

    (h) Within 45 days after the effective date of this AD, submit a 
report to the Manager, New York ACO. The report must include the 
information listed in paragraphs (h)(1), (h)(2), and (h)(3) of this 
AD. Under the provisions of the Paperwork Reduction Act (44 U.S.C. 
3501 et seq.), the Office of Management and Budget (OMB) has 
approved the information collection requirements contained in this 
AD, and assigned OMB Control Number 2120-0056.
    (1) The airplane registration and operation status.
    (2) The usage frequency in terms of total number of flights per 
year and total number of flights per year for which the auxiliary 
tank is used.
    (3) Method of complying with paragraph (g)(1) of this AD.

Alternative Methods of Compliance (AMOCs)

    (i)(1) The Manager, New York ACO, ANE-170, 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: Program 
Manager, Continuing Operational Safety, FAA, New York ACO, 1600 
Stewart Avenue, Suite 410, Westbury, New York 11590; telephone 516-
228-7300; fax 516-794-5531. 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.
    (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.

Appendix A

Deactivation Criteria

    The auxiliary fuel tank deactivation procedures required by 
paragraph (g)(1) of this AD should address the following actions.
    (1) Permanently drain auxiliary fuel tanks, and clear them of 
fuel vapors to eliminate the possibility of out-gassing of fuel 
vapors from the emptied auxiliary tank.
    (2) Disconnect all electrical connections from the fuel quantity 
indication system (FQIS), fuel pumps if applicable, float switches, 
and all other electrical connections required for auxiliary tank 
operation, and stow them at the auxiliary tank interface.
    (3) Disconnect all pneumatic connections if applicable, cap them 
at the pneumatic source, and secure them.
    (4) Disconnect all fuel feed and fuel vent plumbing interfaces 
with airplane original equipment manufacturer (OEM) tanks, cap them 
at the airplane tank side, and secure them in accordance with a 
method approved by the FAA; one approved method is specified in AC 
25-8 Auxiliary Fuel System Installations. In order to eliminate the 
possibility of structural deformation during cabin decompression, 
leave open and secure the disconnected auxiliary fuel tank vent 
lines.
    (5) Pull and collar all circuit breakers used to operate the 
auxiliary tank.
    (6) Revise the weight and balance document, if required, and 
obtain FAA approval.
    (7) Amend the applicable sections of the applicable airplane 
flight manual (AFM) to indicate that the auxiliary fuel tank is 
deactivated. Remove auxiliary fuel tank operating procedures to 
ensure that only the OEM fuel system operational procedures are 
contained in the AFM. Amend the Limitations Section of the AFM to 
indicate that the AFM Supplement for the STC is not in effect. Place 
a placard in the flight deck indicating that the auxiliary tank is 
deactivated. The AFM revisions specified in this paragraph may be 
accomplished by inserting a copy of this AD into the AFM.
    (8) Amend the applicable sections of the applicable flight crew 
operating manual and airplane maintenance manual to remove auxiliary 
tank maintenance procedures.
    (9) After the auxiliary fuel tank is deactivated, accomplish 
procedures such as leak checks and pressure checks deemed necessary 
before returning the airplane to service. These procedures must 
include verification that the airplane FQIS and fuel distribution 
systems have not been adversely affected.
    (10) Revise the instructions for continued airworthiness, as 
required, after deactivation.
    (11) Include with the operator's proposed procedures any 
relevant information or additional steps that are deemed necessary 
by the operator to comply with the deactivation and return the 
airplane to service.

    Issued in Renton, Washington, on February 5, 2010.
Stephen P. Boyd,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.

[FR Doc. 2010-2994 Filed 2-11-10; 8:45 am]
BILLING CODE 4910-13-P