E8-23573. Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800, and -900 Series Airplanes Equipped With CFM56-7 Engines

AGENCY:

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

ACTION:

Final rule.

SUMMARY:

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Boeing Model 737-600, -700, and -800 series airplanes. That AD currently requires repetitive inspections to detect damage of the aft strut insulation blanket, and eventual replacement of the insulation blankets with new, improved blankets. This new AD adds airplanes to the applicability and requires installation of a new heat insulation blanket and new cover plate on the left and right side engine struts. This new AD does not retain the requirements of the existing AD but does terminate the requirements of the existing AD. This AD results from reports of damaged heat insulation blankets on the engine struts. We are issuing this AD to prevent exposure of the lower surface of the strut to extreme high temperatures, consequent creation of a source of fuel ignition, and increased risk of an uncontrollable fire and possible fuel tank explosion.

DATES:

This AD becomes effective November 13, 2008.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in the AD as of November 13, 2008.

ADDRESSES:

For service information identified in this 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 AD, the regulatory evaluation, any comments received, and other information. The address for the Docket Office (telephone [phone]) is the Document Management Facility, U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.

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 [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Discussion

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that supersedes AD 99-04-11, amendment 39-11035 (64 FR 6791, February 11, 1999). The existing AD applies to certain Boeing Model 737-600, -700, and -800 series airplanes. That NPRM was published in the Federal Register on February 8, 2008 (73 FR 7484). That NPRM proposed to add airplanes to the applicability of the existing AD and require installation of a new heat insulation blanket and new cover plate on the left and right side engine struts, which would terminate the requirements of the existing AD.

Comments

We provided the public the opportunity to participate in the development of this AD. We have considered the comments that have been received on the NPRM.

Support for the NPRM

Boeing concurs with the contents of the NPRM. AirTran Airways (AirTran) and Continental Airlines (CAL) agree with the rule.

Request To Delay AD Until Service Bulletin Is Revised

CAL notes that Boeing has released Information Notice (IN) 737-54-1045 IN 01, dated December 4, 2007. CAL notes that this IN states that Figures 2 and 4 of Boeing Special Attention Service Bulletin 737-54-1045, dated July 25, 2007, do not correctly illustrate the proper configuration of the insulation blanket. (We cited Boeing Special Attention Service Bulletin 737-54-1045 in the NPRM as the appropriate source of service information.) Therefore, CAL requests that Boeing revise the service bulletin before we enact the AD.

We disagree with waiting until Boeing revises its service bulletin before we issue the AD. We have determined that an unsafe condition exists and that the actions in this AD must be done to ensure continued safety. We do not consider that delaying this action until after the release of the manufacturer's planned service bulletin is warranted since sufficient instructions currently exist to do the required replacement within the compliance time. Paragraph (h) of this AD provides operators the opportunity to request an extension of the compliance time if data are presented to justify the extension. However, we agree that the information in IN 737-54-1045 IN 01, which relates to the configuration of the insulation blanket, is important. Therefore, we have revised paragraph (f) of this AD to include the relevant information from the IN.

Request To Identify Supplier Part Numbers (P/Ns)

AirTran points out that P/N S315A213-57, as specified in paragraph (f) of the NPRM, is a specification number and that P/N 99A9257M is the supplier part number for the insulation blanket that is listed in the Boeing Model 737-700 Illustrated Parts Catalog. AirTran also points out a similar supplier part number exists for the insulation blankets that are prohibited from installation as specified in paragraph (g) of the NPRM. Therefore, AirTran requests that we identify both the Boeing specification number and the supplier part number in the AD.

We disagree with the request to include supplier part numbers. The Boeing specification number (P/N) S315A213-57 is the high-level identifier for the part. This specification number is printed on each authorized vendor part that is made to Boeing specifications in accordance with the Boeing specification control document. Each authorized vendor can have a different part number. Therefore, using the specification P/N S315A213-57 should prevent any confusion. We have not changed the AD in this regard.

Request To Extend Compliance Time

Air Transport Association (ATA), on behalf of its member American Airlines (AA), is concerned with the proposed 60-month compliance period. The commenters note that the industry standard maintenance interval for the affected Boeing Model 737 airplanes is 72 months. Therefore, a 60-month compliance period would unnecessarily increase out-of-service time and related costs. The commenters propose a 72-month compliance time, which would align more economically with industry standard maintenance review board (MRB) task intervals.

We do not agree with the request to extend the compliance time. In developing an appropriate compliance time for this action, we considered the urgency associated with the subject unsafe condition, the availability of required parts, and the fact that the modification takes 4 work hours. According to the manufacturer, an ample number of required parts will be available to do the installation on the U.S. fleet within the proposed compliance time. In consideration of these items, we have determined that a 60-month compliance time will ensure an acceptable level of safety. However, according to the provisions of paragraph (h) of this AD, we may approve requests to adjust the compliance time if the request includes data that prove that the new compliance time would provide an acceptable level of safety. We have not changed the AD in this regard.

Request To Allow Additional Time for Parts Installation

CAL notes that paragraph (g) of the NPRM states that operators may not install a heat insulation blanket, P/N S315A213-42 or -47, on any airplane after the effective date of the AD. CAL requests that operators be given an additional 60 days after the effective date of the AD to ensure “illegal” parts are purged from the inventory and Boeing is able to supply spare parts.

We contacted CAL to obtain additional technical information in respect to this comment. CAL indicated that they initially had concerns over parts availability and long lead times to obtain P/N S315A213-57 heat insulation blankets. CAL stated that after checking with Boeing, parts availability and lead times are adequate and their comment is no longer relevant. We have not changed the AD in this regard.

Conclusion

We have carefully reviewed the available data, including the comments that have been received, and determined that air safety and the public interest require adopting the AD with the change described previously. We have determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.

Costs of Compliance

There are about 2,148 airplanes of the affected design in the worldwide fleet. This AD affects about 740 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this AD. The average labor rate is $80 per work hour.

Estimated Costs

Action	Work hours	Parts	Cost per airplane	Fleet cost
Installation (new action)	4	$4,730	$5,050	$3,737,000

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 AD will not have federalism implications under Executive Order 13132. This AD will 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 this AD:

(1) Is not a “significant regulatory action” under Executive Order 12866;

(2) Is not a “significant rule” under 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 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
• Incorporation by reference
• Safety

Adoption of the Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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

[Amended]

2. The Federal Aviation Administration (FAA) amends § 39.13 by removing amendment 39-11035 ( 64 FR 6791, February 11, 1999) and by adding the following new airworthiness directive (AD):

2008-21-02 Boeing: Amendment 39-15686. Docket No. FAA-2008-0147; Directorate Identifier 2007-NM-294-AD.

Effective Date

(a) This AD becomes effective November 13, 2008.

Affected ADs

(b) This AD supersedes AD 99-04-11.

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 737-54-1045, dated July 25, 2007.

Unsafe Condition

(d) This AD results from reports of damaged heat insulation blankets on the engine struts. We are issuing this AD to prevent exposure of the lower surface of the strut to extreme high temperatures, consequent creation of a source of fuel ignition, and increased risk of uncontrollable fire and possible fuel tank explosion.

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.

Installation

(f) Within 60 months after the effective date of this AD, install a new heat insulation blanket, part number (P/N) S315A213-57, and a new cover plate on the left and right side engine struts in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1045, dated July 25, 2007, except Figure 2 and Figure 4 of the service bulletin should show four holes on the aft edge of the heat insulation blanket instead of two. Operators should also note that on installation of the heat insulation blanket, the two inner holes on the aft edge of the heat insulation blanket are not used or filled.

Parts Installation

(g) As of the effective date of this AD, no person may install a heat insulation blanket, P/N S315A213-42 or -47, on any airplane.

Alternative Methods of Compliance (AMOCs)

(h)(1) The Manager, Seattle Aircraft Certification Office (ACO), FAA, ATTN: Samuel Spitzer, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle ACO, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone]; 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.

Material Incorporated by Reference

(i) You must use Boeing Special Attention Service Bulletin 737-54-1045, dated July 25, 2007, to perform the actions that are required by this AD, unless the AD specifies otherwise. The Director of the Federal Register approved the incorporation by reference of this document in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207, for a copy of this service information. You may review copies at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/​federal-register/​cfr/​ibr-locations.html.

Issued in Renton, Washington, on September 29, 2008.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.