E7-23460. Airworthiness Directives; Boeing Model 747-400 and 747-400D Series 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 certain Boeing Model 747-400 and 747-400D series airplanes. This proposed AD would require a general visual inspection of the power feeder wire bundle of the auxiliary power unit (APU) where it crosses the hydraulic system 4 return tube to determine if parts are installed to provide separation between the wire bundle and hydraulic tube. This proposed AD would also require related investigative and corrective actions if necessary. This proposed AD results from a report that the power feeder wire bundle of the APU was found touching the hydraulic system return tube during inspection of an airplane. We are proposing this AD to prevent insufficient clearance between the wire bundle and hydraulic tube that could lead to chafing of the wire bundle, which could cause arcing and a consequent hydraulic fluid fire in an area outside of the smoke detection and fire extinguishing zone; this condition could result in an uncontrolled fire on the airplane.

DATES:

We must receive comments on this proposed AD by January 18, 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:

Georgios Roussos, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, 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-2007-0267; Directorate Identifier 2007-NM-245-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 a report indicating that the power feeder wire bundle of the auxiliary power unit (APU) was found touching the hydraulic system return tube during inspection of an in-production Boeing Model 747-400 series airplane. Boeing subsequently surveyed several in-service airplanes and found that most of the airplanes had less than the allowable minimum clearance between the wire bundle and hydraulic tube. The wire bundle and hydraulic tube are installed in the aft bulk cargo compartment above the ceiling lining, in an area outside of the smoke detection and fire extinguishing zone. Insufficient clearance between the wire bundle and hydraulic tube could lead to chafing of the wire bundle, which could cause arcing and a consequent hydraulic fluid fire. This condition, if not corrected, could result in an uncontrolled fire on the airplane.

Relevant Service Information

We have reviewed Boeing Special Attention Service Bulletin 747-24-2257, Revision 1, dated August 2, 2007. The service bulletin describes procedures for doing a general visual inspection of the power feeder wire bundle of the APU where it crosses the hydraulic system 4 return tube to determine if parts are installed to provide separation between the wire bundle and hydraulic tube. The service bulletin also describes procedures for doing related investigative actions and corrective actions if necessary. The related investigative actions include the following actions:

• Measuring the clearance between the wire bundle and hydraulic tube to ensure that the clearance is a minimum of 0.5 inch, if the wire bundle is clamped directly above the hydraulic tube.
• Doing a general visual inspection for damage to the wire bundle where it crosses the hydraulic tube, if two loop clamps and a spacer are installed to provide separation, if a plastic tie strap and mount and loop clamp are installed to provide separation, or if no parts are installed to provide separation.
• Doing a general visual inspection for damage to the hydraulic tube where the wire bundle crosses the hydraulic tube, if the wire bundle is found damaged. The corrective actions include the following actions:
• Adjusting the position of the wire bundle to maximize its separation from the hydraulic tube, if the clearance is less than 0.5 inch.
• Removing any parts installed to provide separation between the wire bundle and hydraulic tube.
• Repairing the damaged wire bundle.
• Repairing the damaged hydraulic tube or replacing it with a new hydraulic tube.
• Installing a tetrafluoroethylene sleeve on the wire bundle and attaching the wire bundle and hydraulic tube with two loop clamps and a spacer.

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 462 airplanes of the affected design in the worldwide fleet. This proposed AD would affect about 61 airplanes of U.S. registry. The proposed inspection would take about 1 work hour 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 $4,880, or $80 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.

§ 39.13

[Amended]

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

Boeing: Docket No. FAA-2007-0267; Directorate Identifier 2007-NM-245-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by January 18, 2008.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 747-400 and 747-400D series airplanes, certificated in any category; as identified in Boeing Special Attention Service Bulletin 747-24-2257, Revision 1, dated August 2, 2007.

Unsafe Condition

(d) This AD results from a report that the power feeder wire bundle of the auxiliary power unit (APU) was found touching the hydraulic system return tube during inspection of an airplane. We are issuing this AD to prevent insufficient clearance between the wire bundle and hydraulic tube that could lead to chafing of the wire bundle, which could cause arcing and a consequent hydraulic fluid fire in an area outside of the smoke detection and fire extinguishing zone; this condition could result in an uncontrolled fire on 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.

Inspection and Related Investigative and Corrective Actions

(f) Within 24 months after the effective date of this AD, do a general visual inspection of the power feeder wire bundle of the APU where it crosses the hydraulic system 4 return tube to determine if parts are installed to provide separation between the wire bundle and hydraulic tube, and do all the related investigative and corrective actions as applicable, by accomplishing all of the actions specified in the Accomplishment Instructions of Boeing Special Attention Service Bulletin 747-24-2257, Revision 1, dated August 2, 2007. The related investigative and corrective actions must be accomplished before further flight after the inspection.

Credit for Actions Done According to Previous Issue of Service Bulletin

(g) Actions done before the effective date of this AD in accordance with Boeing Special Attention Service Bulletin 747-24-2257, dated May 18, 2006, are acceptable for compliance with the corresponding requirements of paragraph (f) of this AD.

Alternative Methods of Compliance (AMOCs)

(h)(1) The Manager, Seattle Aircraft Certification Office, 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 November 23, 2007.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.