E7-24329. Airworthiness Directives; Boeing Model 757 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 757 airplanes. This proposed AD would require repetitive inspections of the anchor tab of the bulkhead seal assemblies of the wing thermal anti-ice (TAI) system for cracks at certain outboard stations of the left and right wings, and corrective action if necessary. This proposed AD also provides optional terminating action for the repetitive inspections. This proposed AD results from reports of cracks found at the anchor tab of the bulkhead seal assemblies of the wing TAI system. In one incident the anchor tab and bulkhead seal assembly had separated because of the cracks. We are proposing this AD to prevent failure of the anchor tab of the bulkhead seal assembly, which in icing conditions could result in insufficient airflow to the wing TAI system, subsequent ice on the wings, and consequent reduced controllability of the airplane.

DATES:

We must receive comments on this proposed AD by January 31, 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: [phone].
• 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, 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 [phone]) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT:

Barbara Mudrovich, Aerospace Engineer, Cabin Safety and Environmental Systems Branch, ANM-150S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone [phone]; fax [phone].

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-2007-0339; Directorate Identifier 2007-NM-182-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 have received reports of cracks found at the anchor tab of the bulkhead seal assemblies of the wing thermal anti-ice (TAI) system on Boeing Model 757 airplanes. In one incident the anchor tab and bulkhead seal assembly had separated because of the cracks. The anchor tab of the bulkhead seal assembly was held in position with a bolt. If the anchor tab fails, the TAI spray tube disconnects from the TAI duct, and it could not supply sufficient airflow for the wing TAI system. If the flight is in icing conditions and there is insufficient airflow, it could cause ice to form on the wings. These conditions, if not corrected, could result in reduced controllability of the airplane.

Relevant Service Information

We have reviewed Boeing Special Attention Service Bulletins 757-30-0021 and 757-30-0022, both Revision 1, both dated June 13, 2007. The service bulletins describe procedures for repetitive detailed inspections for cracks of the anchor tab of the bulkhead seal assemblies of the wing TAI system at certain outboard stations of the left and right wings, and corrective action before further flight if necessary. The compliance time specified in the service bulletin for the initial inspection is before the accumulation of 20,000 total flight hours or within 36 months from the effective date on the service bulletin, whichever occurs later.

The corrective action includes replacing the bulkhead seal assembly or installing new duct anchor support brackets if cracks are found. If the bulkhead seal assembly is replaced, but new support brackets are not installed, the inspections must be repeated until the existing brackets are replaced. Replacing the support brackets eliminates the need for the repetitive inspections. The compliance time for the repetitive inspections is at intervals not to exceed 6,000 flight hours; for airplanes on which the bulkhead seal assemblies are replaced, the inspection is repeated within 20,000 flight hours after the replacement, and thereafter at intervals not to exceed 6,000 flight hours.

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 929 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 530 airplanes of U.S. registry. The proposed inspection would take about 2 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 $84,800, or $160 per airplane, per inspection cycle.

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.

§ 39.13

[Amended]

2. The Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2007-0339; Directorate Identifier 2007-NM-182-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by January 31, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to all Boeing Model 757-200, -200PF, -200CB, and -300 series airplanes, certificated in any category.

Unsafe Condition

(d) This AD results from reports of cracks found at the anchor tab of the bulkhead seal assemblies of the wing thermal anti-ice (TAI) system. In one incident the anchor tab and bulkhead seal assembly had separated because of the cracks. We are issuing this AD to prevent failure of the anchor tab of the bulkhead seal assembly, which in icing conditions could result in insufficient airflow to the wing TAI system, subsequent ice on the wings, and consequent reduced controllability 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.

Repetitive Inspections/Corrective Action

(f) At the applicable times specified in paragraph 1.E., “Compliance,” of Boeing Special Attention Service Bulletin 757-30-0021 or 757-30-0022, both Revision 1, both dated June 13, 2007, as applicable; except where the service bulletins specify starting the compliance time “* * * from the date on this service bulletin,” this AD requires starting the compliance time from the effective date of this AD: Perform detailed inspections for cracks of the anchor tab of the bulkhead seal assemblies of the wing TAI system at certain outboard stations of the left and right wings by doing all the actions, including all applicable corrective actions, in accordance with the Accomplishment Instructions of the applicable service bulletin. Do all applicable corrective actions before further flight.

Optional Terminating Action

(g) Installing a new duct anchor support bracket adjacent to the bulkhead seal assemblies in accordance with Part 2 of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 757-30-0021 or 757-30-0022, both Revision 1, both dated June 13, 2007, as applicable, ends the repetitive inspections required by paragraph (f) of this AD.

Credit for Actions Done According to Previous Issues of Service Information

(h) Actions accomplished before the effective date of this AD in accordance with Boeing Special Attention Service Bulletins 757-30-0021 and 757-30-0022, both dated August 15, 2006, are considered acceptable for compliance with the corresponding actions specified in this AD.

Alternative Methods of Compliance (AMOCs)

(i)(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) 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 December 10, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.