The FAA has received reports indicating that cracking was found in the rear bulkhead of the center section pressure deck at fuselage station (FS) 1363 on a Lockheed Model L-1011-385 series airplane. The cracking extended approximately 30 inches downward along butt line (BL) 42.5 and through the frame at the lower edge of the bulkhead. At that point, the cracking extended aft an additional 26 inches through a skin panel on the lower fuselage. The cause of this cracking appears to be fatigue. Such fatigue cracking, if not detected and corrected in a timely manner, could result in reduced structural integrity of the fuselage.
Lockheed has issued L-1011 Service Bulletin 093-53-268, dated April 15, 1993, which describes procedures for certain inspections to detect cracking of the bulkhead at FS 1363 in the area of the stiffeners at left and right BL 42.5, and repair, if necessary. The repair involves installing web doublers and a splice.
The Lockheedservice bulletin specifies that repair of cracking may be delayed if the cracking falls within certain parameters described in the service bulletin. For these cases, the service bulletin specifies procedures for accomplishing repetitive visual and eddy current inspections until the repair is accomplished. The FAA has reviewed and approved the procedures specified in this Lockheed service bulletin.
The FAA also has reviewed and approved a second document issued by Lockheed: LCC-7622-373, dated May 9, 1995. This document describes procedures for additional inspections to detect cracking of the frame cap for airplanes on which cracking of the bulkhead is found below waterline (WL) 117. Those inspections include the following:
- A bolt hole eddy current inspection to detect cracking of the eight fastener holes at the intersection of the vertical stiffener at BL 42.5 and the frame cap vertical flange;
- A bolt hole eddy current inspection to detect cracking at eight fastener locations in the frame cap lower flange that connect the lower fuselage skin panel to the frame at the BL 42.5 vertical stiffener; and
- A visual inspection to detect stress corrosion cracking of the accessible portions of the fillet radius of the frame cap.
A third document issued by Lockheed, LCC-7622-374, dated May 9, 1995, is referenced in LCC-7622-373. LCC-7622-374 describes procedures for repair of any cracking of the frame cap that is found during the inspections described previously. The repair involves a bolt hole eddy current inspection to detect cracking of the fastener holes (where the fastener holes are removed to perform the repair), and removal of cracks. The FAA has reviewed and approved Lockheed documents LCC-7622-373 and LCC-7622-374.
Since an unsafe condition has been identified that is likely to exist or develop on other Lockheed Model L-1011-385 series airplanes of the same type design, this AD is being issued to prevent reduced structural integrity of the fuselage due to fatigue cracking of the pressure bulkhead. This AD requires a visual inspection to detect cracking of the bulkhead at FS 1363 in the area of the stiffeners at left and right BL 42.5, and repair, if necessary. For airplanes on which cracking of the bulkhead is found below WL 117, this AD requires additional inspections to detect cracking at certain fastener locations and fastener holes and to detect stress corrosion of the frame cap, and repair, if necessary. The actions are required to be accomplished in accordance with the procedures specified in the service bulletin and in the Lockheed documents described previously.
This AD contains provisions specifying that flight with cracking in the bulkhead, within certain parameters, is allowed provided that repetitive visual and eddy current inspections are performed until a repair is accomplished.
This is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking.
As a result of recent communications with the Air Transport Association (ATA) of America, the FAA has learned that, in general, some operators may misunderstand the legal effect of AD's on airplanes that are identified in the applicability provision of the AD, but that have been altered or repaired in the area addressed by the AD. The FAA points out that all airplanes identified in the applicability provision of an AD are legally subject to the AD. If an airplane has been altered or repaired in the affected area in such a way as to affect compliance with the AD, the owner or operator is required to obtain FAA approval for an alternative method of compliance with the AD, in accordance with the paragraph of each AD that provides for such approvals. A note has been included in this rule to clarify this long-standing requirement.
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 rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 95-NM-103-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."
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 part 39 of the Federal Aviation Regulations (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. 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: