Document ID: FAA-2006-25001-0017
Agency: faa
Document Type: Proposed Rule
Title: Airworthiness Directives: Boeing Co. Model 737-600, -700, -700C, -800, -900, and -900ER Series Airplanes
Posted Date: 2011-10-11T04:00Z

[Federal Register Volume 76, Number 196 (Tuesday, October 11, 2011)]
[Proposed Rules]
[Pages 62649-62653]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-26104]

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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; The Boeing Company Model 737-600, -700, 
-700C, -800, -900, and -900ER Series Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Supplemental notice of proposed rulemaking (NPRM); reopening of 
comment period.

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SUMMARY: We are revising an earlier proposed airworthiness directive 
(AD) for the products listed above. That second supplemental NPRM 
proposed a one-time inspection to determine the part numbers of the 
aero/fire seals of the blocker doors on the thrust reverser torque 
boxes on the engines, and replacing affected aero/fire seals with new, 
improved aero/fire seals. That second supplemental NPRM was prompted by 
a report that the top 3 inches of the aero/fire seals of the blocker 
doors on the thrust reverser torque boxes are not fireproof. This 
action revises the second supplemental NPRM by prohibiting installation 
of certain non-fireproof thrust reverser seals. We are proposing this 
third supplemental NPRM 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 fluid leakage zone), 
which could result in an uncontrolled fire. Since these actions impose 
an additional burden over that proposed in the second supplemental 
NPRM, we are reopening the comment period to allow the public the 
chance to comment on these proposed changes.

DATES: We must receive comments on this supplemental NPRM by November 
25, 2011.

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, Attention: Data & Services Management, P.O. Box 
3707, MC 2H-65, Seattle, Washington 98124-2207; telephone 206-544-5000, 
extension 1; fax 206-766-5680; e-mail me.boecom@boeing.com; Internet 
https://www.myboeingfleet.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.

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 (phone: 800-647-5527) is in the ADDRESSES 
section. Comments will be available in the AD docket shortly after 
receipt.

FOR FURTHER INFORMATION CONTACT: Chris Parker, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification 
Office, 1601 Lind Avenue SW., Renton, Washington 98057-3356; phone: 
425-917-6496; fax: 425-917-6590; e-mail: chris.r.parker@faa.gov.

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-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 this proposed AD. We 
will consider all comments received by the closing date and may amend 
this proposed AD because of those comments.

[[Page 62650]]

    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

    We issued a second supplemental NPRM to amend 14 CFR part 39 to 
include an airworthiness directive (AD) that would apply to all Model 
737-600, -700, -700C, -800, -900, and -900ER series airplanes. That 
second supplemental NPRM was published in the Federal Register on July 
16, 2009 (74 FR 34518). That second supplemental NPRM proposed to 
require a one-time inspection to determine the part numbers of the 
aero/fire seals of the blocker doors on the thrust reverser torque 
boxes on the engines, and replacing affected aero/fire seals with new, 
improved aero/fire seals. That second supplemental NPRM also proposed 
to reduce the compliance time for the replacement of the affected aero/
fire seals.

Actions Since Second Supplemental NPRM Was Issued

    Since we issued the second supplemental NPRM (74 FR 34518, July 16, 
2009), we have determined that it is necessary to propose to prohibit 
installation of certain non-fireproof thrust reverser seals in this 
third supplemental NPRM, because we have received information 
indicating that some thrust reversers with non-fireproof seals could be 
installed on certain airplanes.

Comments

    We gave the public the opportunity to comment on the second 
supplemental NPRM (74 FR 34518, July 16, 2009). The following presents 
the comments received on the second supplemental NPRM and the FAA's 
response to each comment.

Request To Include Parts Installation Paragraph

    Boeing requested that the second supplemental NPRM (74 FR 34518, 
July 16, 2009) be revised to address spare thrust reverser halves being 
installed on any Model 737 Next Generation airplane. Boeing explained 
that some spare thrust reverser halves could be equipped with non-
fireproof seals and that if these spare units are installed after the 
inspection, some airplanes will have non-fireproof seals.
    We partially agree. While we explained in the first supplemental 
NPRM (73 FR 51382, September 3, 2008) that we understood affected spare 
assemblies had been purged from the parts supply system, we have now 
received information that thrust reverser interchangeability 
instructions might allow older thrust reverser seals having part number 
(P/N) 315A2245-1 or 315A2245-2 to be installed on newly delivered 
airplanes. While we cannot apply the inspections proposed by this third 
supplemental NPRM to spare parts, we can require that parts being 
installed on the airplane be compliant with this third supplemental 
NPRM. We have added paragraph (i) to this third supplemental NPRM to 
prohibit installation of non-fireproof thrust reverser seals.

Requests To Extend Compliance Time for Replacement

    The Air Transport Association (ATA), on behalf of two member 
airlines (Air Tran Airways and American Airlines), and Boeing requested 
that we change the proposed compliance time for the replacement of the 
aero/fire seals specified in paragraph (h) of the second supplemental 
NPRM (74 FR 34518, July 16, 2009).
    Air Tran Airways (Air Tran) explained that the second supplemental 
NPRM (74 FR 34518, July 16, 2009) proposed to allow up to 60 months or 
8,200 flight cycles after the effective date of the AD to comply with 
the proposed inspection specified in paragraph (g) of the second 
supplemental NPRM. However, Air Tran pointed out that if a non-
fireproof aero/fire seal is found on a thrust reverser, the seal must 
be changed prior to further flight. Air Tran reasoned that the second 
supplemental NPRM should allow a more realistic time frame to have the 
seal replaced. Air Tran provided no technical justification for this 
request.
    Boeing explained that the compliance time from the original NPRM 
(71 FR 34025, June 13, 2006) should be used, regardless of when the 
inspection for aero/fire seals of the thrust reverser torque boxes on 
the engines was done. Boeing stated that the second supplemental NPRM 
(74 FR 34518, July 16, 2009) would likely ground airplanes because 
operators would only accomplish the inspections if they have 
replacement seals on hand; Boeing only carries limited quantities of 
the seals and the re-order lead time for these seals is approximately 
20 weeks.
    We agree to revise this third supplemental NPRM to change the 
proposed compliance time specified in paragraph (h) of this third 
supplemental NPRM. However, we are revising the compliance time in 
paragraph (h) of this third supplemental NPRM to specify that operators 
have within 6 months after doing the inspection in paragraph (g) of 
this third supplemental NPRM to replace a non-fireproof seal. Under the 
provisions of paragraph (k) of this third supplemental NPRM, we will 
consider requests for approval of an alternative method of compliance 
(AMOC) that provides an acceptable level of safety, if parts 
availability becomes a problem. We have determined that replacement of 
the non-fireproof seal within 6 months after doing the inspection in 
paragraph (g) of this third supplemental NPRM will not adversely affect 
safety. We have revised this third supplemental NPRM accordingly.

Request To Specify Terminating Action

    The ATA, on behalf of its member American Airlines, requested that 
the replacement of the non-fireproof seal be done in accordance with 
Boeing Special Attention Service Bulletin 737-78-1074, Revision 1, 
dated September 15, 2005, and that the proposed AD state that this 
replacement is terminating action.
    We agree that the replacement of the non-fireproof seals can be 
done in accordance with Boeing Special Attention Service Bulletin 737-
78-1074, Revision 1, dated September 15, 2005, and that the replacement 
of the non-fireproof seals is terminating action for the inspection 
required by paragraph (g) of this third supplemental NPRM. We have 
added this information to paragraph (h) of this AD.

Requests To Apply AD to Part Rather Than Airplane

    The ATA, on behalf of its member Air Tran, and Boeing requested 
that the second supplemental NPRM (74 FR 34518, July 16, 2009) apply 
only to thrust reverser assemblies having certain part numbers as 
opposed to applying to the airplane.
    Air Tran explained that thrust reversers are rotable, line 
replaceable unit assemblies, which may be uninstalled, stand-alone 
spares, and can be rotated among other airplanes. For this reason, Air 
Tran suggested that the applicability of the second supplemental NPRM 
(74 FR 34518, July 16, 2009) should be against thrust reverser assembly 
part numbers rather than the airplane.
    Boeing explained that the proposed applicability in the second 
supplemental NPRM (74 FR 34518, July 16, 2009) is open-ended and would 
apply to new Model 737 airplanes that are already compliant. Boeing 
explained further that thrust reversers having part number (P/Ns) 
315A2295-195 through

[[Page 62651]]

315A2295-500 were delivered with seals with a fireproof section, and 
that interchangeability definitions for thrust reversers having P/Ns 
315A2245-7 and 315A2245-8 (fireproof section) do not allow these seals 
to be replaced with seals having P/Ns 315A2245-1 and 315A2245-2 (non-
fireproof). Boeing recommended limiting the proposed applicability to 
thrust reversers having P/Ns 315A2295-3 through 315A2295-194, and P/Ns 
315A2295-503 through 315A2295-694.
    We disagree to change the applicability of this third supplemental 
NPRM to apply to thrust reversers having certain part numbers. The seal 
is not integral to the thrust reverser and is replaceable. Therefore, a 
non-fireproof seal could be used on any thrust reverser--even a thrust 
reverser originally built with a compliant fireproof seal. It is the 
operator's responsibility to maintain compliance once an AD has been 
accomplished. The operator must ensure that the thrust reversers on its 
airplanes have been inspected and are using a fireproof seal. If an 
operator replaces a thrust reverser, the thrust reverser must be 
inspected to ensure compliance with this third supplemental NPRM. We 
have not changed the applicability of this third supplemental NPRM in 
this regard.
    However, we have determined that the inspection required by 
paragraph (g) of this third supplemental NPRM is only necessary for 
certain airplanes. Therefore, we have revised paragraph (g) of this 
third supplemental NPRM to specify that only the following airplanes 
are subject to the requirements of that paragraph: ``For airplanes 
having an original airworthiness certificate issued before the 
effective date of this AD, and for airplanes on which the date of 
issuance of the original export certificate of airworthiness is before 
the effective date of this AD * * * .''

Request for Clarification of Use of Illustrated Parts Catalog (IPC) as 
Maintenance Record

    All Nippon Airways (ANA) requested that we clarify if their IPC can 
be used as a form of maintenance record to identify if the airplane has 
the fireproof seal installed. ANA explained that the seals are not 
controlled by any type of part-control system, and that operators 
visually verify the stamped part number instead. ANA stated that since 
the stamped part number is often unreadable, the operator would be 
forced to replace the seal in order to remain in compliance with the 
AD, regardless if the seal was already a fireproof seal. ANA asserted 
that replacing a possible fireproof seal (to remain in compliance with 
the proposed AD) simply because the part number is unreadable, is an 
unreasonable action.
    We disagree to allow use of the IPC as a maintenance record. If the 
required maintenance records, which do not include the IPC, are not 
available to show that the correct fireproof seal has been installed, 
and the part number is worn off the aero/fire seals, it is still 
possible to verify that the correct part is installed by visually 
inspecting the seal for color content, as specified in paragraph (g) of 
the second supplemental NPRM. We have not changed this third 
supplemental NPRM in this regard.

Request for Clarification of the Difference in the Applicability 
Between the Original NPRM and the Second Supplemental NPRM

    ANA also requested that we clarify the difference in the 
applicability between the original NPRM (71 FR 34025, June 13, 2006) 
and the second supplemental NPRM (74 FR 34518, July 16, 2009). ANA 
explained that the applicability in the original NPRM was for all Model 
737-600, -700,-700C, -800, and -900 series airplanes, which is what is 
listed in Boeing Special Attention Service Bulletin 737-78-1074, 
Revision 1, dated September 15, 2005 (referenced in the original NPRM 
as the source of service information for replacing aero/fire seals).
    We agree to clarify differences in the applicability of the various 
NPRMs. The applicability of the original NPRM (71 FR 34025, June 13, 
2006) referenced that service bulletin for affected airplanes. After we 
issued the original NPRM, we received information on the 
interchangeability of the affected aero/fire seals. The applicability 
of the first supplemental NPRM (73 FR 51382, September 3, 2008) was 
revised to specify ``all'' Model 737 airplanes (including Model 737-
900ER series airplanes, which had been added to the U.S. type 
certificate data sheet), since all of these airplanes could be affected 
by the interchangeability of the seals. No change to this third 
supplemental NPRM is necessary in this regard.

Explanation of Change Made to This Proposed AD

    We have revised this proposed AD to identify the legal name of the 
manufacturer as published in the most recent type certificate data 
sheet for the affected airplane models.

FAA's Determination

    We are proposing this third supplemental NPRM because we evaluated 
all the relevant information and determined the unsafe condition 
described previously is likely to exist or develop in other products of 
these same type designs. Certain changes described above expand the 
scope of the second supplemental NPRM (74 FR 34518, July 16, 2009). As 
a result, we have determined that it is necessary to reopen the comment 
period to provide additional opportunity for the public to comment on 
this third supplemental NPRM.

Explanation of Change to Costs of Compliance

    Since issuance of the original NPRM (71 FR 34025, June 13, 2006), 
we have increased the labor rate used in the Costs of Compliance from 
$80 per work-hour to $85 per work-hour. The Costs of Compliance 
information, below, reflects this increase in the specified labor rate.

Costs of Compliance

    We estimate that this proposed AD affects 803 airplanes of U.S. 
registry.
    We estimate the following costs to comply with this proposed AD:

                                                                     Estimated Costs
--------------------------------------------------------------------------------------------------------------------------------------------------------
              Action                        Labor cost              Parts cost         Cost per product                Cost on U.S. operators
--------------------------------------------------------------------------------------------------------------------------------------------------------
Inspection for part number........  1 work-hour x $85 per      None................  $85 per inspection    $68,255 per inspection cycle.
                                     hour = $85 per                                   cycle.
                                     inspection cycle.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    We estimate the following costs to do any necessary replacements 
that would be required based on the results of the proposed inspection. 
We have no way of determining the number of aircraft that might need 
this replacement:

[[Page 62652]]

                                               On-condition Costs
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                                                                                                       Cost per
                  Action                                    Labor cost                   Parts cost    product
----------------------------------------------------------------------------------------------------------------
Replacement..............................  5 work-hours x $85 per hour = $425.........       $4,770       $5,195
----------------------------------------------------------------------------------------------------------------

    According to the manufacturer, some of the costs of this proposed 
AD may be covered under warranty, thereby reducing the cost impact on 
affected individuals. We do not control warranty coverage for affected 
individuals. As a result, we have included all costs in our cost 
estimate.

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),
    (3) Will not affect intrastate aviation in Alaska, and
    (4) 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.

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 
airworthiness directive (AD):

    The Boeing Company: Docket No. FAA-2006-25001; Directorate 
Identifier 2006-NM-079-AD.

Comments Due Date

    (a) We must receive comments by November 25, 2011.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to all The Boeing Company Model 737-600, -
700, -700C, -800, -900, and -900ER series airplanes, certificated in 
any category.

Subject

    (d) Joint Aircraft System Component (JASC)/Air Transport 
Association (ATA) of America Code 78: Engine exhaust.

Unsafe Condition

    (e) This AD was prompted by a report that the top 3 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 fluid leakage zone), which could result in 
an uncontrolled fire.

Compliance

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

Inspection to Determine Type of Aero/Fire Seals

    (g) For airplanes having an original airworthiness certificate 
issued before the effective date of this AD, and for airplanes on 
which the date of issuance of the original export certificate of 
airworthiness is before the effective date of this AD: Within 60 
months or 8,200 flight cycles, whichever occurs first, after the 
effective date of this AD, perform a one-time detailed inspection to 
determine the color of the aero/fire seals of the blocker doors on 
the thrust reverser torque boxes on the engines. For any aero/fire 
seal having a completely grey color (which is the color of seals 
with part number (P/N) 315A2245-1 or 315A2245-2), with no red at the 
upper end of the seal, do the actions specified in paragraph (h) of 
this AD. For any aero/fire seal having a red color at the upper end 
of the seal (which indicates installation of seals with P/N 
315A2245-7 or 315A2245-8), no further action is required by this AD. 
A review of airplane maintenance records is acceptable in lieu of 
this inspection if from that review the part number of the correct 
aero/fire seals (P/N 315A2245-7 or -8) can be conclusively 
determined to be installed.

    Note 1: 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 
mirrors, magnifying lenses, etc., may be necessary. Surface cleaning 
and elaborate procedures may be required.''

Replacement of the Aero/Fire Seals

    (h) For any aero/fire seal identified during the inspection/
records check required by paragraph (g) of this AD to have a non-
fireproof seal: Within six months after doing the actions required 
by paragraph (g) of this AD, 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. 
Replacing 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, is terminating action for the inspection 
required by paragraph (g) of this AD.

Parts Installation

    (i) As of the effective date of this AD, no person may install a 
non-fireproof thrust reverser seal having P/N 315A2245-1 or P/N 
315A2245-2 on any airplane.

[[Page 62653]]

Credit for Actions Accomplished in Accordance with Previous Service 
Information

    (j) 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 (h) of 
this AD.

Alternative Methods of Compliance (AMOCs)

    (k)(1) The Manager, Seattle 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. In accordance with 14 
CFR 39.19, send your request to your principal inspector or local 
Flight Standards District Office, as appropriate. If sending 
information directly to the manager of the ACO, send it to the 
attention of the person identified in the Related Information 
section of this AD. Information may be e-mailed to: 9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.

Related Information

    (l) For more information about this AD, contact Chris Parker, 
Aerospace Engineer, Propulsion Branch, ANM-140S, 1601 Lind Avenue, 
SW., Renton, Washington 98057-3356; phone: 425-917-6496; fax: 425-
917-6590; e-mail: chris.r.parker@faa.gov.
    (m) For service information identified in this AD, contact 
Boeing Commercial Airplanes, Attention: Data & Services Management, 
P. O. Box 3707, MC 2H-65, Seattle, Washington 98124-2207; telephone 
206-544-5000, extension 1; fax 206-766-5680; e-mail 
me.boecom@boeing.com; Internet https://www.myboeingfleet.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.

    Issued in Renton, Washington, on September 30, 2011.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2011-26104 Filed 10-7-11; 8:45 am]
BILLING CODE 4910-13-P