04-18745. Airworthiness Directives; Boeing Model 757-200 and -200PF Series Airplanes

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 757-200 and -200PF series airplanes. This proposed AD would require repetitive inspections and audible tap tests of the upper and lower skins of the trailing edge wedges on certain slats, and related investigative and corrective actions if necessary. This proposed AD also provides an optional terminating action for the repetitive inspections and audible tap tests. This proposed AD is prompted by a report of damage to the No. 4 leading edge slat. We are proposing this AD to prevent delamination of the leading edge slats, possible loss of pieces of the trailing edge wedge assembly during flight, reduction of the reduced maneuver and stall margins, and consequent reduced controllability of the airplane.

DATES:

We must receive comments on this proposed AD by October 1, 2004.

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 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.

FOR FURTHER INFORMATION CONTACT:

Dennis Stremick, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Docket Management System (DMS)

The FAA has implemented new procedures for maintaining AD dockets electronically. As of May 17, 2004, new AD actions are posted on DMS and assigned a docket number. We track each action and assign a corresponding directorate identifier. The DMS AD docket number is in the form “Docket No. FAA-2004-99999.” The Transport Airplane Directorate identifier is in the form “Directorate Identifier 2004-NM-999-AD.” Each DMS AD docket also lists the directorate identifier (“Old Docket Number”) as a cross-reference for searching purposes.

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-2004-18876; Directorate Identifier 2003-NM-254-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.

We are reviewing the writing style we currently use in regulatory documents. We are interested in your comments on whether the style of this document is clear, and your suggestions to improve the clarity of our communications that affect you. You can get more information about plain language at http://www.faa.gov/​language and http://www.plainlanguage.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 located 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 a report of damage to the No. 4 leading edge slat on a Boeing Model 757-200 series airplane. The affected airplane had 54,000 total flight hours and 24,000 total flight cycles. Investigation revealed that a large piece of the trailing edge wedge broke away from the slat during flight. The crew was not aware that the piece had broken away until a post-flight walk around inspection. Further investigation revealed that during the assembly of the affected trailing edge wedge, BMS 5-104 adhesive was used to bond the skins to the honeycomb core material. Analysis showed that moisture entered the internal structure of the wedge assembly, resulting in a decrease in the strength of the trailing edge wedge skin-to-core bond and corrosion of the aluminum honeycomb core. This condition eventually caused an area of the skin to delaminate from the honeycomb core material. The intensity of the flight loads on the affected airplane was sufficient to cause pieces of the skin to break away during flight. This condition, if not corrected, could result in reduced maneuver and stall margins, and consequent reduced controllability of the airplane.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin 757-57A0063, dated June 26, 2003. The alert service bulletin describes procedures for a detailed inspection and an audible tap test of the upper and lower skins of the trailing edge wedge on slats No. 2 through No. 4 inclusive and No. 7 through No. 9 inclusive, for evidence of damage and cracking on the trailing edge wedge assembly, and related investigative and corrective actions. Evidence of damage to the wedge assembly skin includes cracking in the skin; delamination of the skin and the chord, the doublers, and the honeycomb core; separation between those components; or bulges in the skin or areas where the skin has broken off from the wedge. Evidence of damage to the inboard and outboard ends of the wedge assembly includes cracking in the sealant and end potting, and pieces of end potting that have broken off from the wedge.

If there is an indication of delamination during the audible tap test, the related investigative action is doing the “Bondline Delamination Inspection in Honeycomb Structure” described in the Boeing 757 Nondestructive Test Manual.

The corrective actions include repairing affected trailing edge wedge assemblies, or replacing the trailing edge wedge assemblies with new, improved wedge assemblies. The service bulletin states that replacement of trailing edge wedge assemblies with new, improved trailing edge wedge assemblies eliminates the need for the repetitive detailed inspection and audible tap test.

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. Therefore, we are proposing this AD, which would require repetitive inspections and audible tap tests of the upper and lower skins of the trailing edge wedges on certain slats, and related investigative and corrective actions if necessary. The proposed AD would require you to use the service information described previously to perform these actions. The proposed AD provides an optional terminating action for the repetitive inspections and audible tap tests.

Costs of Compliance

This proposed AD would affect about 139 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	Number of U.S.-registered airplanes	Fleet cost
Inspection/ test, per inspection cycle	1 6	$65	None	2 $390	97	2 $37,830
1 One work hour per slat, six slats per airplane.
2 Per inspection/test cycle.

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-2004-18876; Directorate Identifier 2003-NM-254-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this AD action by October 1, 2004.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Boeing Model 737-200 and -200PF series airplanes listed in Boeing Alert Service Bulletin 757-57A0063, dated June 26, 2003; certificated in any category.

Unsafe Condition

(d) This AD was prompted by a report of damage to the No. 4 leading edge slat. We are issuing this AD to prevent delamination of the leading edge slats, possible loss of pieces of the trailing edge wedge assembly during flight, reduction of the reduced maneuver and stall margins, 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 and Tests

(f) Within 18 months after the effective date of this AD: Do a detailed inspection and an audible tap test of the upper and lower skins of the trailing edge wedges on slats No. 2 through No. 4 inclusive and No. 7 through No. 9 inclusive, for evidence of damage or cracking, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 757-57A0063, dated June 26, 2003. Repeat the detailed inspection and audible tap test thereafter at intervals not to exceed 18 months.

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.”

Related Investigative and Corrective Actions

(g) If any damage or cracking is found during any inspection or audible tap test required by paragraph (a) of this AD: Before further flight, do the related investigative action, if applicable, and replace the affected part with a new trailing edge wedge assembly or repair the affected part, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 757-57A0063, dated June 26, 2003. Accomplishing the replacement terminates the repetitive inspections and audible tap tests required by paragraph (f) of this AD for that wedge assembly only.

Parts Installation

(h) As of the effective date of this AD, no trailing edge wedge assembly having a part number listed in the “Existing Part Number” column of the table in paragraph 2.C.3. of Boeing Alert Service Bulletin 757-57A0063, dated June 26, 2003, can be installed on any airplane unless it has been inspected, tested, and any necessary corrective actions accomplished in accordance with this AD.

Optional Terminating Action

(i) Replacing all trailing edge wedge assemblies with new, improved wedge assemblies in accordance with Part III of the Accomplishment Instructions of Boeing Alert Service Bulletin 757-57A0063, dated June 26, 2003, terminates the requirements of this AD.

Alternative Methods of Compliance (AMOCs)

(j)(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) An AMOC that provides an acceptable level of safety may be used for any repair required by this AD, if it is approved by a Boeing Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make those findings. For a repair method to be approved, the approval must specifically refer to this AD.

Issued in Renton, Washington, on August 9, 2004.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.