Airworthiness Directives; Boeing Model 707 Airplanes, and Model 720 and 720B Series Airplanes, 36370-36373 [E7-12818]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 72, Number 127 (Tuesday, July 3, 2007)]
[Proposed Rules]
[Pages 36370-36373]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E7-12818]


========================================================================
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.

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


Federal Register / Vol. 72, No. 127 / Tuesday, July 3, 2007 / 
Proposed Rules

[[Page 36370]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-28381; Directorate Identifier 2006-NM-164-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 707 Airplanes, and Model 
720 and 720B Series Airplanes

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

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for all Boeing Model 707 Airplanes, and Model 720 and 720B series 
airplanes. This proposed AD would require revising the FAA-approved 
maintenance program by incorporating new airworthiness limitations 
(AWLs) for fuel tank systems to satisfy Special Federal Aviation 
Regulation No. 88 requirements. This proposed AD would also require the 
initial performance of certain repetitive AWL inspections to phase in 
those inspection, and repair if necessary. This proposed AD results 
from a design review of the fuel tank systems. We are proposing this 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 fuel 
tank explosions and consequent loss of the airplane.

DATES: We must receive comments on this proposed AD by August 17, 2007.

ADDRESSES: Use one of the following addresses to submit comments on 
this proposed AD.
     DOT Docket Web site: Go to https://dms.dot.gov and follow 
the instructions for sending your comments electronically.
     Government-wide rulemaking Web site: Go to https://
www.regulations.gov and follow the instructions for sending your 
comments electronically.
     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.
     Fax: (202) 493-2251.
     Hand Delivery: Room W12-140 on the ground floor of the 
West Building, 1200 New Jersey Avenue SE., 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 the service information identified in this 
proposed AD.

FOR FURTHER INFORMATION CONTACT: Kathrine Rask, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue SW., Renton, Washington 98057-3356; telephone 
(425) 917-6505; 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 ``FAA-2007-
28381; Directorate Identifier 2006-NM-164-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 https://
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 DOT's complete Privacy Act Statement in the 
Federal Register published on April 11, 2000 (65 FR 19477-78), or you 
may visit https://dms.dot.gov.

Examining the Docket

    You may examine the AD docket on the Internet at https://
dms.dot.gov, or in person at the Docket Operations office between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays. The 
Docket Operations office (telephone (800) 647-5527) is located on the 
ground floor of the West 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

    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

[[Page 36371]]

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 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 fuel tank explosions and consequent loss of the airplane.

Relevant Service Information

    We have reviewed the following sections of Boeing 707/720 
Airworthiness Limitations (AWL) Document D6-7552-AWL, Original Release 
March 2006 (referred to hereafter as ``D6-7552-AWL March 2006'' or 
``document D6-7552-AWL,'' depending upon the associated text):
     Section B, ``FUEL SYSTEMS AIRWORTHINESS LIMITATIONS''
     Section C, ``SYSTEM AWL PAGE FORMAT''
     Section D, ``AIRWORTHINESS LIMITATIONS--FUEL SYSTEMS''
    Those sections of D6-7552-AWL March 2006 describe new airworthiness 
limitations (AWLs) for fuel tank systems. The new AWLs include:
     An AWL inspection, which is a periodic inspection of 
certain features for latent failures that could contribute to an 
ignition source; and
     Critical design configuration control limitations (CDCCL), 
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.
    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 exist or develop on other airplanes 
of this same type design. For this reason, we are proposing this AD, 
which would require revising the FAA-approved maintenance program by 
incorporating the information in the service information described 
previously. The proposed AD also would require initial accomplishment 
of the repetitive inspection specified in the AWLs to phase in that 
repetitive inspection, and repair if necessary.

Explanation of Compliance Time

    In most ADs, we adopt a compliance time allowing a specified amount 
of time after the AD's effective date. In this case, however, the FAA 
has already issued regulations that require operators to revise their 
maintenance/inspection programs to address fuel tank safety issues. The 
compliance date for these regulations is December 16, 2008. To provide 
for efficient and coordinated implementation of these regulations and 
this proposed AD, we are using this same compliance date in this 
proposed AD, instead of the 18-month compliance time recommended by 
Boeing.

Rework Required When Implementing AWLs Into an Existing Fleet

    The maintenance program revision for the fuel tank systems 
specified in paragraph (g) of this proposed AD, which involves 
incorporating the information specified in D6-7552-AWL March 2006, 
would affect how operators maintain their airplanes. After doing the 
maintenance program revision, operators would need to do any 
maintenance on the fuel tank system as specified in the CDCCLs. 
Maintenance done before doing the maintenance program revision 
specified in paragraph (g) would not need to be redone in order to 
comply with paragraph (g). For example, the AWL that requires fuel 
pumps to be repaired and overhauled per an FAA-approved component 
maintenance manual (CMM) applies to fuel pumps repaired after the AWLs 
are revised; spare or on-wing fuel pumps do not need to be reworked. 
For AWLs that require repetitive inspections, the initial inspection 
interval (threshold) starts from the date the maintenance program 
revision specified in paragraph (g) is done, except as provided by 
paragraph (h) of this proposed AD. This proposed AD would require only 
the maintenance program revision specified in paragraph (g), and 
initial inspection specified in paragraph (h). No other fleet-wide 
inspections need to be done.

Changes to Fuel Tank System AWLs

    Paragraph (g) of this proposed AD would require revising the 
maintenance program by incorporating certain information specified in 
D6-7552-AWL March 2006. Paragraph (g) also allows accomplishing the 
maintenance program revision in accordance with later revisions of D6-
7552-AWL March 2006 as an acceptable method of compliance if they are 
approved by the Manager, Seattle Aircraft Certification Office (ACO), 
FAA. In addition, D6-7552-AWL March 2006 specifies that any deviations 
from the published AWL instructions, including AWL intervals, in 
document D6-7552-AWL must be approved by the Manager, Seattle ACO. 
Therefore, after doing the maintenance program revision, any further 
revision to an AWL or AWL interval should be done as an AWL change, not 
as an alternative method of compliance (AMOC). For U.S.-registered 
airplanes, operators must make requests through an appropriate FAA 
Principal Maintenance Inspector (PMI) or Principal Avionics Inspector 
(PAI) for approval by the Manager, Seattle ACO. A non-U.S. operator 
should coordinate changes with its governing regulatory agency.

Exceptional Short-Term Extensions

    D6-7552-AWL March 2006 has provisions for an exceptional short-term 
extension of 30 days. An exceptional short-term extension is an 
increase in an AWL interval that may be needed to cover an 
uncontrollable or unexpected situation. For U.S.-registered airplanes, 
the FAA PMI or PAI must concur with any exceptional short-term 
extension before it is used, unless the operator has identified another 
appropriate procedure with the local regulatory authority. The FAA PMI 
or PAI may grant the exceptional short-term extensions described in D6-
7552-AWL March 2006. without consultation with the Manager, Seattle 
ACO. A non-U.S. operator should coordinate changes with its governing 
regulatory agency. As explained in D6-7552-AWL March 2006, exceptional 
short-term extensions must not be used for fleet AWL extensions. An 
exceptional short-term extension should not be confused with an 
operator's short-term escalation authorization approved in accordance 
with the Operations Specifications or the operator's reliability 
program.

[[Page 36372]]

Ensuring Compliance With Fuel Tank System AWLs

    Boeing has revised their applicable maintenance manuals and task 
cards to address AWLs and to include notes about CDCCLs. Operators that 
do not use Boeing's revision service should revise their maintenance 
manuals and task cards to highlight actions that are tied to CDCCLs to 
ensure that maintenance personnel are complying with the CDCCLs. 
Appendix A of D6-7552-AWL March 2006 contains a list of Air Transport 
Association (ATA) sections for the revised maintenance manuals. 
Operators may wish to use the appendix as an aid to implement the AWLs.

Recording Compliance With Fuel Tank System AWLs

    The applicable operating rules of the Federal Aviation Regulations 
(14 CFR parts 91, 121, 125, and 129) require operators to maintain 
records with the identification of the current inspection status of an 
airplane. One AWL cited in D6-7552-AWL March 2006 is an inspection for 
which the applicable sections of the operating rules apply. The other 
AWLs are CDCCLs, which are tied to on-condition maintenance actions. An 
entry into an operator's existing maintenance record system for 
corrective action is sufficient for recording compliance with CDCCLs, 
as long as the applicable maintenance manual and task cards identify 
actions that are CDCCLs.

Changes to CMMs Cited in Fuel Tank System AWLs

    Some of the AWLs in D6-7552-AWL March 2006 refer to specific 
revision levels of the CMMs as additional sources of service 
information for doing the AWLs. Boeing is referencing the CMMs by 
revision level in the applicable AWL for certain components rather than 
including information directly in document D6-7552-AWL because of the 
volume of that information. As a result, the Manager, Seattle ACO must 
approve the CMMs. Any later revision of those CMMs will be handled like 
a change to the AWL itself. Any use of parts (including the use of 
parts manufacturer approval (PMA) approved parts), methods, techniques, 
and practices not contained in the CMMs need to be approved by the 
Manager, Seattle ACO, or governing regulatory authority. For example, 
operators that have developed pump repair/overhaul manuals must get 
them approved by the Manager, Seattle ACO.

Changes to AMMs Referenced in Fuel Tank System AWLs

    In other AWLs in D6-7552-AWL March 2006, the AWLs contain all the 
necessary data. The applicable section of the maintenance manual is 
usually included in the AWLs. Boeing intended this information to 
assist operators in maintaining the maintenance manuals. A maintenance 
manual change to these tasks can be made without approval by the 
Manager, Seattle ACO, through an appropriate FAA PMI or PAI, by the 
governing regulatory authority, or by using the operator's standard 
process for revising maintenance manuals. An acceptable change would 
have to maintain the information specified in the AWL such as the pass/
fail criteria or special test equipment.

Costs of Compliance

    There are about 213 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 76 airplanes of 
U.S. registry. The proposed actions would take about 8 work hours per 
airplane, at an average labor rate of $80 per work hour. Based on these 
figures, the estimated cost of the proposed AD for U.S. operators is 
$48,640, or $640 per airplane.

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 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 
adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-28381; Directorate Identifier 2006-NM-
164-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by August 
17, 2007.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to all Boeing Model 707-100 long body, -200, 
-100B long body, and -100B short body series airplanes; Model 707-
300, -300B, -300C, and -400 series airplanes; and Model 720 and 720B 
series airplanes; certificated in any category.

    Note 1: This AD requires revisions to certain operator 
maintenance documents to include new inspections and maintenance 
actions. Compliance with these limitations is required by 14 CFR 
43.16 and 91.403(c). For airplanes that have been previously 
modified, altered, or repaired in the areas addressed by these 
limitations, the operator may not be able to accomplish the actions 
described in the revisions. In this situation, to comply with 14 CFR 
43.16 and 91.403(c), the operator must request approval for revision 
to the airworthiness limitations (AWLs) in the Boeing 707/720 
Airworthiness

[[Page 36373]]

Limitations (AWL) Document D6-7552-AWL, Original Release March 2006, 
as specified in paragraph (g) or (i) of this AD, as applicable.

Unsafe Condition

    (d) This AD results from a design review of the fuel tank 
systems. We are issuing this 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 fuel tank explosions and 
consequent loss of the airplane.

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.

Service Information

    (f) The term ``D6-7552-AWL March 2006,'' as used in this AD, 
means Boeing 707/720 Airworthiness Limitations Document D6-7552-AWL, 
Original Release March 2006.

Revision of AWLs Section

    (g) Before December 16, 2008, revise the FAA-approved 
maintenance program by incorporating the information in the sections 
specified in paragraphs (g)(1) through (g)(3) of this AD, except 
that the initial inspection specified in paragraph (h) of this AD 
must be done at the time specified in paragraph (h). Accomplishing 
the revision in accordance with a later revision of Boeing 707/720 
Airworthiness Limitations Document D6-7552-AWL is an acceptable 
method of compliance if the revision is approved by the Manager, 
Seattle Aircraft Certification Office (ACO), FAA.
    (1) Section B., ``FUEL SYSTEMS AIRWORTHINESS LIMITATIONS,'' of 
D6-7552-AWL March 2006.
    (2) Section C., ``SYSTEM AWL PAGE FORMAT,'' of D6-7552-AWL March 
2006.
    (3) Section D., ``AIRWORTHINESS LIMITATIONS--FUEL SYSTEMS,'' of 
D6-7552-AWL March 2006.

Initial Inspection and Repair if Necessary

    (h) At the later of the times specified in paragraphs (h)(1) and 
(h)(2) of this AD: Do a detailed inspection of external wires over 
the center fuel tank for damaged or loose clamps, wire chafing, and 
wire bundles in contact with the surface of the center fuel tank, in 
accordance with Section D, ``AIRWORTHINESS LIMITATIONS--FUEL 
SYSTEMS,'' AWL number 28-AWL-01, of D6-7552-AWL March 2006. If any 
discrepancy is found during this inspection, repair the discrepancy 
before further flight in accordance with D6-7552-AWL March 2006. 
Accomplishing the actions required by this paragraph in accordance 
with a later revision of D6-7552-AWL March 2006 is an acceptable 
method of compliance if the revision is approved by the Manager, 
Seattle ACO.
    (1) Before the accumulation of 36,000 total flight cycles, or 
within 120 months since the date of issuance of the original 
standard airworthiness certificate or the date of issuance of the 
original export certificate of airworthiness, whichever occurs 
first.
    (2) Within 72 months after the effective date of this AD.

    Note 2: 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.''

Alternative Methods of Compliance (AMOCs)

    (i)(1) The Manager, Seattle ACO, has the authority to approve 
AMOCs for this AD, if requested in accordance with 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 June 22, 2007.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
 [FR Doc. E7-12818 Filed 7-2-07; 8:45 am]
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