AD 2000-15-12

Effective August 23, 2000.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of August 23, 2000.

Comments for inclusion in the Rules Docket must be received on or before October 10, 2000.

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-183-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-iarcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 2000-NM-183-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text.

The service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Nenita Odesa, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2557; fax (425) 227-1181.

The FAA has received reports indicating that, during regular maintenance, operators found stress corrosion cracks in the front spar of the center section of the horizontal stabilizer on two Boeing Model 737-100 and -200 series airplanes. The subject airplanes had 42,700 and 67,100 flight cycles. The front spar is made from 7079-T6 aluminum, a material that was used for this component until the manufacturer determined that the material is susceptible to stress corrosion cracking. Cracks in the front spar will decrease the structural strength of the center section of the horizontal stabilizer. This condition, if not corrected, could result in structural failure of the horizontal stabilizer and loss of control of the airplane.

The FAA has reviewed and approved Boeing Alert Service Bulletin 737-55A1071, dated February 24, 2000, which describes procedures for repetitive detailed visual inspections to detect cracking in the front spar of the center section of the horizontal stabilizer, and corrective actions, if necessary. If cracking is within certain limits, corrective actions involve rework of the front spar fitting that includes removing damaged material, performing a high frequency eddy current inspection to detect cracking, and shot peening the damaged area. If cracking is outside the limits, the alert service bulletin specifies to contact the manufacturer for repair instructions. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design, this AD is being issued to detect and correct stress corrosion cracking in the front spar of the center section of the horizontal stabilizer, which could result in structural failure of the horizontal stabilizer and loss of control of the airplane. This AD requires accomplishment of the actions specified in the alert service bulletin described previously, except as discussed below.

Operators should note that, although the alert service bulletin specifies that the manufacturer may be contacted for disposition of certain repair conditions, this AD requires the repair of those conditions to be accomplished in accordance with a method approved by the FAA, or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings.

The service bulletin also provides for a terminating action by replacing the front spar with a spar made from a 7050 or 7075 aluminum forging. However, this AD does not authorize the terminating action proposed in the service bulletin.

Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.

Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption ADDRESSES. All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Submit comments using the following format:

• Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.

• For each issue, state what specific change to the AD is being requested.

• Include justification (e.g., reasons or data) for each request.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2000-NM-183-AD.” The postcard will be date stamped and returned to the commenter.

The regulations adopted herein will 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. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a “significant regulatory action” under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

1. The authority citation for part 39 continues to read as follows:

2. Section 39.13 is amended by adding the following new airworthiness directive: