[Federal Register Volume 71, Number 113 (Tuesday, June 13, 2006)]
[Proposed Rules]
[Pages 34025-34026]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-9163]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2006-25001; Directorate Identifier 2006-NM-079-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800 
and -900 Series Airplanes

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

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for certain Boeing Model 737-600, -700, -700C, -800 and -900 series 
airplanes. This proposed AD would require replacing the aero/fire seals 
of the blocker doors on the thrust reverser torque boxes on the engines 
with new, improved aero/fire seals. This proposed AD results from a 
report that the top three inches of the aero/fire seals of the blocker 
doors on the thrust reverser torque boxes are not fireproof. We are 
proposing this AD to prevent a fire in the fan compartment (a fire 
zone) from migrating through the seal to a flammable fluid in the 
thrust reverser actuator compartment (a flammable leakage zone), which 
could result in an uncontrolled fire.

DATES: We must receive comments on this proposed AD by July 28, 2006.

ADDRESSES: Use one of the following addresses to submit comments on 
this proposed AD.
     DOT Docket Web site: Go to http://dms.dot.gov and follow 
the instructions for sending your comments electronically.
     Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your 
comments electronically.
     Mail: Docket Management Facility, U.S. Department of 
Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, 
Washington, DC 20590.
     Fax: (202) 493-2251.
     Hand Delivery: Room PL-401 on the plaza level of the 
Nassif Building, 400 Seventh Street, SW., 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: Doug Pegors, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone 
(425) 917-6504; 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-2006-
25001; Directorate Identifier 2006-NM-079-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 http://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 http://dms.dot.gov.

Examining the Docket

    You may examine the AD docket on the Internet at http://dms.dot.gov, or in person at the Docket Management Facility office 
between 9 a.m. and 5 p.m., Monday through Friday, except Federal 
holidays. The Docket Management Facility office (telephone (800) 647-
5227) is located on the plaza level of the Nassif 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

    We have received a report indicating that Boeing found that on a 
Model 737 airplane, the upper three inches of the aero/fire seal of the 
blocker doors on the thrust reverser torque box extended past the metal 
v-blade/groove designed to serve as a firewall for the seal. The seal 
itself serves as a firewall between a fire zone and a flammable leakage 
zone in the upper region of the thrust reverser torque box. The seal is 
not fireproof (unable to withstand 2,000 degrees Fahrenheit for 15 
minutes) and could allow a fire in the fan compartment, which is a fire 
zone, to migrate to a flammable fluid in the thrust reverser actuator 
compartment, which is a flammable leakage zone. This condition, if not 
corrected, could result in an uncontrolled fire.

Relevant Service Information

    We have reviewed Boeing Special Attention Service Bulletin 737-78-
1074, Revision 1, dated September 15, 2005. The service bulletin 
describes procedures for replacing the aero/fire seals of the blocker 
doors on the thrust reverser torque boxes on the engines with new, 
improved aero/fire seals. 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 accomplishing the actions specified in the service 
information described previously.

Costs of Compliance

    There are about 1,595 airplanes of the affected design in the 
worldwide fleet. This proposed AD would affect about 616 airplanes of 
U.S. registry. The proposed actions would take about 4 work hours per 
airplane, at an average labor rate of $80 per work hour. Required parts 
would cost about $3,910 per airplane. Based on these figures, the 
estimated cost of the proposed AD for

[[Page 34026]]

U.S. operators is $2,605,680, or $4,230 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-2006-25001; Directorate Identifier 2006-NM-
079-AD.

Comments Due Date

    (a) The FAA must receive comments on this AD action by July 28, 
2006.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Boeing Model 737-600, -700, -700C, -800 
and -900 series airplanes, certificated in any category; as 
identified in Boeing Special Attention Service Bulletin 737-78-1074, 
Revision 1, dated September 15, 2005.

Unsafe Condition

    (d) This AD results from a report that the top three inches of 
the aero/fire seals of the blocker doors on the thrust reverser 
torque boxes are not fireproof. We are issuing this AD to prevent a 
fire in the fan compartment (a fire zone) from migrating through the 
seal to a flammable fluid in the thrust reverser actuator 
compartment (a flammable leakage zone), which could result in an 
uncontrolled fire.

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.

Replace the Aero/Fire Seal

    (f) Within 60 months or 8,200 flight cycles after the effective 
date of this AD, whichever occurs first, replace the aero/fire seals 
of the blocker doors on the thrust reverser torque boxes on the 
engines with new, improved aero/fire seals in accordance with the 
Accomplishment Instructions of Boeing Special Attention Service 
Bulletin 737-78-1074, Revision 1, dated September 15, 2005.

Previously Accomplished Actions

    (g) Replacements done before the effective date of this AD in 
accordance with the Accomplishment Instructions of Boeing Special 
Attention Service Bulletin 737-78-1074, dated April 7, 2005, are 
acceptable for compliance with the requirements of paragraph (f) of 
this AD.

Alternative Methods of Compliance (AMOCs)

    (h)(1) The Manager, Seattle Aircraft Certification Office (ACO), 
FAA, has the authority to approve AMOCs for this AD, if requested in 
accordance with the procedures found in 14 CFR 39.19.
    (2) Before using any AMOC approved in accordance with Sec.  
39.19 on any airplane to which the AMOC applies, notify the 
appropriate principal inspector in the FAA Flight Standards 
Certificate Holding District Office.

    Issued in Renton, Washington, on June 5, 2006.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E6-9163 Filed 6-12-06; 8:45 am]
BILLING CODE 4910-13-P