AD 96-14-07

Effective July 24, 1996.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of July 24, 1996.

Comments for inclusion in the Rules Docket must be received on or before September 9, 1996.

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 96-NM-133-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

The service information referenced in this AD may be obtained from McDonnell Douglas Corporation, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Technical Publications Business Administration, Department C1-L51 (2-60). This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Los Angeles Aircraft Certification Office, Transport Airplane Directorate, 3960 Paramount Boulevard, Lakewood, California; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Raymond Vakili, Aerospace Engineer, Propulsion Branch, ANM-140L, FAA, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California 90712; telephone (310) 627-5262; fax (310) 627-5210.

On November 4, 1991, the FAA issued AD 91-24-09, amendment 39-8095 (56 FR 61364, December 3, 1991), applicable to certain McDonnell Douglas Model MD-11 and MD-11F series airplanes. That AD requires repetitive visual inspections of the tail tank fuel pipe assembly and the associated mounting brackets located in the aft fuselage compartment to verify the correct position of the pipe flange and to detect damaged brackets. It also requires various follow-on actions, if any discrepancy is detected. That AD also provides for an optional terminating modification for the repetitive inspections. That action was prompted by a report of an uncontained fuel leak in the aft fuselage compartment on an in-service airplane, which was the result of migration of the tail tank fuel pipe assembly, and consequent exposure of the O-ring that provides the seal between the pipe assembly and the coupling shroud assembly. The actions required by that AD are intended to prevent a fuel leak in the aft fuselage compartment area, and the possibility of an in-flight or ground fire.

Since the issuance of that AD, the FAA has received several reports of cracking or bending of the fuel pipe mounting support and/or attaching bracket at station Y=2033.750 in the aft fuselage compartment on McDonnell Douglas Model MD-11 series airplanes. A section of the fuel pipe assembly and support bracket of some of these airplanes had been replaced in accordance with the optional terminating modification specified in AD 91-24-09. Additionally, this replacement had been accomplished during production on certain other airplanes on which these incidents occurred.

Investigation revealed that a fuel pressure surge during transfer of the tail tank fuel caused repetitive loading of the fuel pipe mounting support and/or attaching bracket, which resulted in the subject cracking/bending. Although none of the reported events have resulted in a fuel leak in the aft fuselage compartment, the FAA has determined that severe deformation of the bracket could allow the pipe to migrate, which could also expose the O-ring that provides the seal between the fuel pipe and coupling. If the O-ring is exposed, it could lose its sealing effect, and allow a fuel leak in the aft fuselage compartment, which could result in a possible in-flight or ground fire.

In light of these recent incidents, which are similar to the incident that prompted the issuance of AD 91-24-09, the FAA finds that the optional and on-condition terminating modifications (i.e., replacement of a section of the fuel pipe assembly and support bracket, an FAA-approved repair procedure, and replacement of the shroud assembly) specified in AD 91-24-09 do not adequately preclude the addressed unsafe condition identified as in-flight or ground fire. Therefore, the FAA finds that repetitive visual inspections to detect discrepancies (i.e., cracks, or deformation) of the fuel pipe of the fuel transfer system of the tail tank and associated mounting bracket located in the aft fuselage compartment, and to verify the correct position of the fuel pipe flange are necessary. These actions will ensure that the unsafe condition presented by fuel surge during transfer of tail tank fuel is corrected, and provide an acceptable level of safety.

The FAA has reviewed and approved McDonnell Douglas Alert Service Bulletin MD11-28A082, dated May 14, 1996. The alert service bulletin describes procedures for repetitive visual inspections to detect discrepancies (i.e., cracks, or deformation) of the fuel pipe of the fuel transfer system of the tail tank and associated mounting bracket located in the aft fuselage compartment; and to verify the correct position of the fuel pipe flange, and various follow-on actions. These follow-on actions include replacing the O-ring, repositioning the tail tank fuel pipe, and installing a temporary phenolic support block assembly. Installation of a phenolic support block assembly between the tail tank fuel pipe and adjoining structure as a temporary restraint will minimize the possibility of migration of the tail tank fuel pipe.

In addition, the visual inspections and certain of the follow-on actions of Alert Service Bulletin MD11-28A082 are essentially identical to those described in McDonnell Douglas MD-11 Alert Service Bulletin A28-22, Revision 4, dated September 16, 1991 (which was referenced in AD 91-24-09). However, the effectivity listing of Alert Service Bulletin MD11-28A082 includes additional airplanes that were not included in the effectivity listing of Alert Service Bulletin A28-22. These additional airplanes have been found to be subject to the addressed unsafe condition.

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of this same type design, this AD supersedes AD 91-24-09 to require repetitive visual inspections to detect discrepancies (i.e., cracks or deformation) of the fuel pipe of the fuel transfer system of the tail tank and associated mounting bracket located in the aft fuselage compartment and to verify the correct position of the fuel pipe flange, and various follow-on actions. This AD also expands the applicability of the existing AD to include additional airplanes.

This is considered to be interim action. The manufacturer has advised that it currently is developing a modification that will positively address the unsafe condition addressed by this AD. Once this modification is developed, approved, and available, 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.

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 rule must submit a self-addressed, stamped postcard on which the following statement is made: ``Comments to Docket Number 96-NM-133-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 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.

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

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:

Authority: 49 U.S.C. 106(g), 40113, 44701.