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

Summary:

The FAA is revising an earlier proposed airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. The original NPRM would have required replacing the aero/fire seals of the blocker doors on the thrust reverser torque boxes on the engines with new, improved aero/fire seals. The original NPRM resulted 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. This action revises the original NPRM by adding airplanes to the applicability statement and requiring a one-time inspection to determine the part numbers of the aero/fire seals. We are proposing this 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.

Table of Contents

Table of Figures

Dates:

We must receive comments on this supplemental NPRM by September 29, 2008.

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 Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

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:

Samuel Spitzer, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue SW., Renton, Washington 98057-3356; telephone (425) 917-6510; 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 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.

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 notice of proposed rulemaking (NPRM) (the “original NPRM”) to amend 14 CFR part 39 to include an airworthiness directive (AD) that would apply to certain Boeing Model 737-600, -700, -700C, -800 and -900 series airplanes. The original NPRM was published in the Federal Register on June 13, 2006 (71 FR 34025). The original NPRM proposed to 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.

Actions Since Original NPRM Was Issued

Since we issued the original NPRM, we have received information on the rotability of the affected aero/fire seals. Also, Model 737-900ER series airplanes have been added to the U.S. type certificate data sheet and could be affected by the rotability of the seals.

Comments

We have considered the following comments on the original NPRM.

Support for the Original NPRM

Boeing concurs with the contents of the original NPRM.

Request To Revise the Applicability Statement To Address Rotable Parts

AirTran Airways requests that we revise the applicability statement of the original NPRM to apply to the part number/serial number of the affected thrust reverser assembly instead of the serial number of airplanes. AirTran is concerned that the proposed applicability does not address the possibility that an affected thrust reverser assembly might be installed on an airplane not addressed in that applicability statement. AirTran states that the thrust reverser assembly is a rotable component, which can be removed from an airplane affected by this proposed AD and installed on an airplane not affected by this proposed AD. AirTran also notes that the thrust reverser assemblies have serialized numbers and are tracked by most airlines.

We agree that it is possible to rotate the affected component onto another Model 737-600, -700, -700C, -800, -900, or -900ER series airplane that is not affected by the applicability proposed in the original NPRM. We have revised the applicability statement in this supplemental NPRM to apply to all Model 737-600, -700, -700C, -800, -900 and -900ER series airplanes. We have also added a new paragraph (f) to this supplemental NPRM to require a record check or inspection to determine the part number of the installed assembly. If an affected part number is installed, or the part number cannot be confirmed, then operators would be required to replace the assemblies. We have coordinated this issue with Boeing.

Request To Address Spare Parts

AirTran notes that the original NPRM does not address thrust reverser assemblies that were purchased as spare parts. AirTran states that the original NPRM does not require any modifications to any thrust reverserassembly not currently installed on an airplane.

We infer that AirTran is concerned about the possibility that an affected and unmodified spare thrust reverser assembly may be installed on an airplane.We do not agree that revising the supplemental NPRM to address spare parts is necessary. We have confirmation from Boeing that all affected spare assemblies have been purged from the parts supply system. In addition, no affected/unsafe part is allowed to be installed on an airplane after the compliance time of an AD has passed. We have revised this supplemental NPRM to address the rotability concern expressed in the previous comment. For these reasons, we consider revising the AD to address spare parts unnecessary. We have not changed the supplemental NPRM in this regard.

Request To Incorporate by Reference During NPRM Process

The Modification and Replacement Parts Association (MARPA) requests that the applicable service information be incorporated by reference in the NPRM phase of rulemaking and posted on the Federal Docket Management System (FDMS) for public access. MARPA states that since the service information has additional information that is not public, the proposed rule is not enforceable.

We do not agree that documents should be incorporated by reference during the NPRM phase of rulemaking. The Office of the Federal Register requires that documents that are necessary to accomplish the requirements of the AD be incorporated by reference during the final rule phase of rulemaking. This supplementary NPRM is not a final rule and does not incorporate the relevant service information by reference. Further, we point out that while documents that are incorporated by reference do become public information, they do not lose their copyright protection. For that reason, we advise the public to contact the manufacturer to obtain copies of the referenced service information.

In regard to the commenter's request to post service bulletins on the Department of Transportation's FDMS, we are currently in the process of reviewing issues surrounding the posting of service information on-line as part of an AD docket. Once we have thoroughly examined all aspects of this issue and have made a final determination, we will consider whether our current practice needs to be revised. No change to the supplemental NPRM is necessary in this regard.

Request To Address Defective Parts Manufacturer Approval (PMA) Parts

The same commenter also requests that the Transport Airplane Directorate (TAD) develop a policy to address possible defective or replacement PMA alternative parts, regardless of the manufacturing source (original equipment manufacturer (OEM), PMA, or repair station), so that all defective PMA parts are also subject to the proposed AD and are removed from the parts stream.

The FAA recognizes the need for standardization of this issue and is currently in the process of reviewing issues that address the use of PMAs in ADs at the national level. However, the Transport Airplane Directorate considers that to delay this particular AD action would be inappropriate, since we have determined that an unsafe condition exists and that replacement of certain parts must be accomplished to ensure continued safety. Therefore, no change has been made to the supplemental NPRM in this regard.

FAA's Determination and Proposed Requirements of the Supplemental NPRM

We are proposing this supplemental NPRM because we evaluated all pertinent information and determined an unsafe condition exists and is likely to exist or develop on other products of the same type design. Certain changes described above expand the scope of the original NPRM. 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 supplemental NPRM.

Costs of Compliance

There are about 2,442 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.

Estimated Costs
ActionWork hoursAverage labor rate per hourPartsCost perairplane Number of U.S.-registered airplanesFleet cost
Inspection to determine part number (new proposed action) 1 $80 $0 $80 803 $64,240

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 supplemental NPRM 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.

§ 39.13

2. The Federal Aviation Administration (FAA) amends § 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 September 29, 2008.

Affected ADs

(b) None.

Applicability

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

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 fluid 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.

Inspection To Determine Part Number (P/N)

(f) Within 60 months or 8,200 flight cycles after the effective date of this AD, whichever occurs first: 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 gray color (which is the color of seals with P/N 315A2245-1 or 315A2245-2), with no red at the upper end of the seal, do the actions specified in paragraph (g) of this AD. For any aero/fire seal having a red color at the upper end of the seal (which indicates a different part number), no further action is required by this AD. A review of airplane maintenance records is acceptable in lieu of this inspection if the part number of the correct aero/fire seals (P/Ns 315A2245-7 or -8) can be conclusively determined to be installed from that review.

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 mirror, magnifying lenses, etc., may be necessary. Surface cleaning and elaborate procedures may be required.”

Replace the Aero/Fire Seals

(g) For any aero/fire seal identified during the inspection/records check in paragraph (f) of this AD as having an affected P/N: 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.

Credit for Actions Done Using Previous Service Information

(h) 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 (g) of this AD.

Alternative Methods of Compliance (AMOCs)

(i)(1) The Manager, Seattle Aircraft Certification Office, FAA, ATTN: Samuel Spitzer, Aerospace Engineer, Propulsion Branch, ANM-140S, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6510; fax (425) 917-6590; has the authority to approve AMOCs for this AD, if requested using 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 August 25, 2008. Dionne Palermo,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

References

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