Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800, and -900 Series Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to supersede an existing airworthiness directive (AD) that applies to all Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. That AD currently requires either determining exposure to runway deicing fluids containing potassium formate, or performing repetitive inspections of certain electrical connectors in the wheel well of the main landing gear (MLG) for corrosion, and follow-on actions. This proposed AD would add a new inspection requirement and related corrective actions. This proposed AD is prompted by additional reports indicating that significant corrosion of the electrical connectors in the wheel well of the MLG has also been found on airplanes that land on runways treated with deicing fluids containing potassium acetate. We are proposing this AD to prevent corrosion and subsequent moisture ingress into the electrical connectors, which could result in an electrical short and consequent incorrect functioning of critical airplane systems essential to safe flight and landing of the airplane, including fire warning systems.

DATES:

We must receive comments on this proposed AD by January 18, 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.
• Fax: (202) 493-2251.
• 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 the service information identified in this proposed AD contact Boeing Commercial Airplane Group, 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:

Technical Information: Binh Tran, Aerospace Engineer, Systems and Equipment Branch, ANM-130S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 917-6485; fax (425) 917-6590.

Plain language information: Marcia Walters, marcia.walters@faa.gov.

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-2004-19750; Directorate Identifier 2003-NM-192-AD” at the beginning 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 received 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 our docket Web site, 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 the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may 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 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 (800) 647-5227) 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

On July 29, 2002, we issued AD 2002-16-03, amendment 39-12842 (67 FR 52396, August 12, 2002), for all Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. That AD requires either determining exposure to runway deicing fluids containing potassium formate or performing repetitive inspections of certain electrical connectors in the wheel well of the main landing gear (MLG) for corrosion, and follow-on actions. That AD was prompted by reports of significant corrosion of the electrical connectors in the main wheel well. We issued that AD to prevent such corrosion, which could result in incorrect functioning of critical airplane systems essential to safe flight and landing of the airplane, including fire warning systems.

Actions Since Existing AD was Issued

Since we issued AD 2002-16-03, we have received reports of significant corrosion of the electrical connectors located in the wheel well of the MLG on Model 737 series airplanes that land on runways treated with deicing fluids containing potassium acetate. Investigation revealed that the corrosive effects of potassium acetate on the electrical connectors are similar to those of potassium formate, and the requirements in the existing AD do not account for exposure to deicing fluids containing potassium acetate. Significant corrosion can lead to loss of the cadmium plating of the electrical connectors and subsequent moisture ingress into the connectors, which could result in an electrical short and consequent incorrect functioning of critical airplane systems essential to safe flight and landing of the airplane, including fire warning systems.

Revised Service Information

We have reviewed Boeing Alert Service Bulletin 737-24A1148, Revision 1, dated July 10, 2003 (the original issue was referenced in the existing AD as the appropriate source of service information for accomplishment of the actions). The service bulletin describes procedures for inspecting electrical connectors (including the contacts and backshells) of the line replaceable unit (LRU) in the wheel well of the MLG for corrosion, and related corrective actions if necessary. Signs of corrosion are the presence of moisture, corrosion pits, or white-colored material buildup on the connectors; black or reddish discoloration on the contacts; or loss of the olive-drab conversion coating on the backshells. The related corrective actions include cleaning the LRU connectors and applying corrosion inhibiting compound (CIC) if no corrosion is found, and replacing the LRU with a new LRU and applying CIC if corrosion is found. The service bulletin also recommends an operational test of the affected systems after doing the applicable actions. Accomplishing the actions specified in the revised 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 products of this same type design. Therefore, we are proposing this AD, which would supersede AD 2002-16-03. This proposed AD would require either determining exposure to runway deicing fluids containing potassium formate and/or potassium acetate, or performing repetitive inspections of certain electrical connectors in the wheel well of the main landing gear for corrosion, and significant/corrective actions if necessary. This proposed AD would require you to use the service information described previously to perform these actions, except as discussed under “Difference Between the Proposed AD and Service Information.”

Difference Between the Proposed AD and Service Information

The service bulletin specifies an “examination” for corrosion of the electrical connectors in the MLG wheel well. For the purposes of this AD, we have determined that the procedures in the service bulletin constitute a “detailed inspection.” Note 1 of this proposed AD defines that inspection.

Work Hour Rate Increase

We have reviewed the figures we have used over the past several years to calculate AD costs to operators. To account for various inflationary costs in the airline industry, we find it necessary to increase the labor rate used in these calculations from $60 per work hour to $65 per work hour. The cost impact information, below, reflects this increase in the specified hourly labor rate.

Costs of Compliance

This proposed AD would affect about 587 airplanes of U.S. registry. The new determination of airplane exposure would take about 1 work hour per airplane, at an average labor rate of $65 per work hour. Based on these figures, the estimated cost of the actions specified in this proposed AD for U.S. operators is $38,155, or $65 per airplane, per 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.