04-28667. Airworthiness Directives; Boeing Model 747-200B, 747-200C, 747-200F, 747-300, and 747SR Series Airplanes Equipped with General Electric (GE) CF6-45 or -50 Series Engines

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 747-200B, 747-200C, 747-200F, 747-300, and 747SR series airplanes, equipped with GE CF6-45 or -50 series engines. This proposed AD would require modifying the side cowl assemblies on the engines by replacing existing wear plates with new extended wear plates and installing new stop fittings. This proposed AD is prompted by reports of a gap at the interface of the lower portion of the side cowl and the aft flange of the thrust reverser. We are proposing this AD to prevent an excessive quantity of air from entering the fire zone that surrounds the engine, which in the event of an engine fire, could result in an inability to control or extinguish the fire.

DATES:

We must receive comments on this proposed AD by February 17, 2005.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD.

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., Nassif Building, room PL-401, Washington, DC 20590.
• By fax: [phone].
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street SW., Washington, DC, 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.

You can examine the contents of this AD docket on the Internet at http://dms.dot.gov,, or in person at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., room PL-401, on the plaza level of the Nassif Building, Washington, DC. This docket number is FAA-2004-19945; the directorate identifier for this docket is 2004-NM-22-AD.

FOR FURTHER INFORMATION CONTACT:

Dan Kinney, Aerospace Engineer, Propulsion Branch, ANM-140S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to submit any written relevant data, views, or arguments regarding this proposed AD. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2004-19945; Directorate Identifier 2004-NM-22-AD” in the subject line of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments submitted by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov,, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of that website, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You can review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you can visit http://dms.dot.gov.

Examining the Docket

You can examine the AD docket on the Internet at http://dms.dot.gov,, or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone [phone]) is on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the DMS receives them.

Discussion

We have received reports indicating that a gap may form at the interface of the lower portion of the side cowl and the aft flange of the thrust reverser on certain Boeing Model 747-200B, 747-200C, 747-200F, 747-300, and 747SR series airplanes, equipped with General Electric CF6-45 or -50 series engines. The gap forms when high engine thrust is applied, but may not always close when thrust is reduced. The gap is attributed to axial deflection of the engine case combined with the difference in the rate of expansion due to heat between the aluminum frame of the thrust reverser and the titanium frame of the engine. The gap may allow an excessive quantity of air into the nacelle surrounding the engine, which is a fire zone that is equipped with fire detection, containment, and extinguishing provisions. However, excess air in the area could defeat some or all of the fire protection provisions. This condition, if not corrected, could result in an inability to control or extinguish an engine fire.

Relevant Service Information

We have reviewed Boeing Service Bulletin 747-71-2300, Revision 1, dated October 30, 2003. The service bulletin describes procedures for modifying the side cowl assemblies on the engines by replacing existing wear plates with new extended wear plates and installing new stop fittings. The procedures for replacing the existing wear plates include performing open-hole high frequency eddy current (HFEC) inspections for cracking of existing fastener holes, and creating new fastener holes and plugging existing holes if necessary. The procedures for installing the new stop fittings involves installing brackets, channels, and wear pads; replacing existing fasteners with new fasteners if necessary; performing open-hole HFEC inspections for cracking of fastener holes; and oversizing fastener holes and installing different-sized fasteners if necessary. Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

Boeing Service Bulletin 747-71-2300, Revision 1, refers to Boeing Service Letter 747-SL-71-045-C, dated April 10, 2003, as the applicable source of service information for doing certain recommended actions. Among other actions, Boeing Service Letter 747-SL-71-045-C describes procedures for improving the aerodynamic smoothness of the side cowl assemblies by removing bulb seals that may have been installed on the trailing edge of the fan thrust reverser in accordance with a previous issue of Boeing Service Letter 747-SL-71-045. The procedures for removing the bulb seals include plugging open holes on the trailing edge of the fan thrust reverser, and adjusting the cowl latches if necessary.

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. Therefore, we are proposing this AD, which would require modifying the side cowl assemblies on the engines by replacing existing wear plates with new extended wear plates, and installing new stop fittings. The proposed AD would require you to use the service information described previously to perform these actions, except as discussed under “Differences Between the Proposed AD and Service Information.”

Differences Between the Proposed AD and Service Information

Section 1.B., “Concurrent Requirements,” of Boeing Service Bulletin 747-71-2300, Revision 1, states that the service bulletin “assumes that the cowls have had wear plates installed per Service Bulletin 747-54-2093.” We have determined that Boeing Service Bulletin 747-71-2300, Revision 1, refers to Boeing Service Bulletin 747-54-2093 only because Boeing Service Bulletin 747-71-2300, Revision 1, removes certain parts that may have been installed according to Boeing Service Bulletin 747-54-2093. We have discussed this matter with Boeing and have determined that the Accomplishment Instructions in Boeing Service Bulletin 747-71-2300, Revision 1, are effective regardless of whether Boeing Service Bulletin 747-54-2093 has been done. In light of this information, this proposed AD would not require the actions in Boeing Service Bulletin 747-54-2093.

Boeing Service Bulletin 747-71-2300, Revision 1, also “assumes” that one certain airplane has been modified to have a narrower trailing edge strip. We have determined that the subject airplane has been modified; thus, this proposed AD would not require this modification.

As described previously, Boeing Service Bulletin 747-71-2300, Revision 1, recommends that bulb seals installed previously in accordance with a previous issue of Boeing Service Letter 747-SL-71-045 be removed in accordance with Boeing Service Letter 747-SL-71-045-C, dated April 10, 2003. If the bulb seals were previously installed, paragraph (g) of this proposed AD would require you to remove them concurrent with or before further flight after accomplishing the actions in Boeing Service Bulletin 747-71-2300, Revision 1.

Costs of Compliance

This proposed AD would affect about 38 airplanes of U.S. registry and 140 airplanes worldwide. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.

Estimated Costs

Action	Work hours	Average labor rate per hour	Parts	Cost per airplane	Fleet cost
Modification per Boeing Service Bulletin 747-71-2300, Revision 1	72	$65	$25,736	$30,416	$1,155,808

Authority for This Rulemaking

The FAA's authority to issue rules regarding aviation safety is found in Title 49 of the United States Code. 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.

This rulemaking is promulgated under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, the FAA is charged 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 proposed AD.

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. 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 FAA amends § 39.13 by adding the following new airworthiness directive (AD):

Boeing: Docket No. FAA-2004-19945; Directorate Identifier 2004-NM-22-AD. Comments Due Date.

(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by February 17, 2005.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 747-200B, 747-200C, 747-200F, 747-300, and 747SR series airplanes; certificated in any category; equipped with General Electric CF6-45 or -50 series engines.

Unsafe Condition

(d) This AD was prompted by reports of a gap at the interface of the lower portion of the side cowl and the aft flange of the thrust reverser. We are issuing this AD to prevent an excessive quantity of air from entering the fire zone that surrounds the engine, which, in the event of an engine fire, could result in an inability to control or extinguish the 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.

Modification

(f) Within 24 months after the effective date of this AD: Modify the side cowl assemblies on the engines by replacing existing wear plates with new extended wear plates and installing new stop fittings, by doing all actions according to the Accomplishment Instructions of Boeing Service Bulletin 747-71-2300, Revision 1, dated October 30, 2003. Any applicable corrective actions must be done before further flight.

On Condition: Removal of Bulb Seals and Other Specified Actions

(g) If bulb seals were installed on the trailing edge of the fan thrust reverser in accordance with Boeing Service Letter 747-SL-71-045: Concurrent with or before further flight after accomplishing paragraph (f) of this AD, remove the bulb seals, plug the open holes in the trailing edge of the fan thrust reverser, and adjust the cowl latches as applicable, in accordance with Boeing Service Letter 747-SL-71-045-C, dated April 10, 2003.

Alternative Methods of Compliance (AMOCs)

(h) 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.

Issued in Renton, Washington, on December 20, 2004.

Kevin M. Mullin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.