AD 94-02-08

Recently, one operator of McDonnell Douglas Model MD-11 series airplanes reported one instance of the auto ground spoiler failing to arm on one airplane. Investigation revealed two wires that had burnt in half and several charred wires on shelf 3 of the aft section of the main avionics rack. These wires apparently had chafed and shorted on the screws that attach the wire bundle trough assembly to the rack. Additionally, the protective tape was worn from the attach screw heads. The operator then conducted a fleet inspection and found additional wire chafing at the same location on another airplane. The operator also found worn protective tape (exposed screw heads) at various locations on the avionics racks on other airplanes. Chafing of the wiring in the main avionics rack, if not detected and corrected in a timely manner, could result in arcing and a fire in the wire bundle; this could lead to damage to aircraft systems and the loss of associated aircraft functions.

The FAA has reviewed and approved McDonnell Douglas MD-11 Alert Service Bulletin A24-75, dated December 22, 1993, that describes procedures for performing a visual inspection to detect chafing damage to the wire harness located on the aft side of the main avionics rack on shelves 1 through 4. It also describes procedures for repairing or replacing damaged wiring, and modifying the wiring installation by bonding nylon sheets between the wire harnesses and the protective tape on the screw heads.

Since an unsafe condition has been identified that is likely to exist or develop on other Model MD-11 series airplanes of the same type design, this AD is being issued to prevent chafing of the main avionics rack wiring, which could result in arcing and fire in the wire bundle, and lead to damage to aircraft systems and the subsequent loss of associated aircraft functions. This AD requires a detailed visual inspection to detect chafing damage to the wire harnesses locatedon the aft side of the main avionics rack on shelves 1 through 4. Any damaged wiring must be replaced or repaired prior to further flight. Additionally, operators are required to modify the wiring installation by bonding nylon sheets between the wire harnesses and the protective tape on the screw heads. The actions are required to be accomplished in accordance with the service bulletin described previously.

This is considered interim action until final action is identified, at which time the FAA may consider additional rulemaking.

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.

Comments Invited

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.

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 notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 93-NM-231-AD." The postcard will be date stamped and returned to the commenter.

The regulations adopted herein will not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and 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."

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment

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

PART 39 - AIRWORTHINESS DIRECTIVES

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

Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

§ 39.13 - (Amended)

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