Airworthiness Directives; Lockheed Model L-1011-385 Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Lockheed Model L-1011-385 series airplanes. This proposal would require repetitive inspections to detect cracking of the fuselage skin in the areas of the left- and right-hand stringerless sidewall window belts, and repair, if necessary. This proposal is prompted by reports of fatigue cracks found in the fuselage skin where the skin thickness steps from 0.40 to 0.23 inch. The actions specified by the proposed AD are intended to detect and correct cracking of the fuselage skin, which could result in reduced structural integrity of the airplane.

DATES:

Comments must be received by April 3, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-311-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal holidays.

The service information referenced in the proposed rule may be obtained from Lockheed Martin Aircraft & Logistics Center, 120 Orion Street, Greenville, South Carolina 29605. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Small Airplane Directorate, Atlanta Aircraft Certification Office, One Crown Center, 1895 Phoenix Boulevard, suite 450, Atlanta, Georgia.

FOR FURTHER INFORMATION CONTACT:

Thomas Peters, Aerospace Engineer, Systems and Flight Test Branch, ACE-116A, FAA, Small Airplane Directorate, Atlanta Aircraft Certification Office, One Crown Center, 1895 Phoenix Boulevard, suite 450, Atlanta, Georgia 30349; telephone (770) 703-6063; fax (770) 703-6097.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this notice may be changed in light of the comments received.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal 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 98-NM-311-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 98-NM-311-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received a report indicating that an 8-inch crack in the fuselage skin was found on a Model L-1011 series airplane in the stringerless sidewall window belt at fuselage station (FS) 1283 on the left-hand side. The fatigue crack occurred along a machined radius in the area where the sidewall skin thickness decreases from 0.40 inch to 0.23 inch. This condition, if not corrected, could result in cracking of the fuselage skin, which could result in reduced structural integrity of the airplane.

Explanation of Relevant Service Information

The FAA has reviewed and approved Lockheed Service Bulletin 093-53-279, dated May 6, 1998, which describes procedures for repetitive ultrasonic and low frequency eddy current inspections to detect cracking of the fuselage skin in the areas of the left-hand and right-hand stringerless sidewall window belts. Repair for cracking consists of installing external skin doublers (on the fuselage outer skin) and internal straps and angle fittings. The service bulletin describes 6 inspection zones, which are located at FS 1243, 1263, and 1283, and between waterlines 224.5 and 253, on the left-hand and right-hand sides of the fuselage. The specific areas of inspection are the radii on both the forward and aft sides of the machined cutout where the fuselage skin steps from 0.40 to 0.23 inch. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require accomplishment of the actions specified in the service bulletin described previously.

This AD specifies that flight with a crack is allowed, provided that cracking is within prescribed limits. The FAA has determined that this allowance provides an acceptable level of safety because (1) the crack growth is easily detectable, and (2) the established repetitive inspection procedures would detect cracked structure at an interval that would permit repairs to be accomplished before the structure's strength falls below ultimate load carrying capability.

Differences Between the Proposed AD and the Service Bulletin

Operators should note that, although the service bulletin recommends that operators contact Lockheed Martin Engineering for assistance in the event that crack repair is required in two adjacent frames, this proposal would require the repair of those conditions to be accomplished in accordance with a method approved by the FAA. The generic repairs specified by the service bulletin may not be adequate if they are installed in two adjacent locations. Therefore, the FAA has determined that a unique repair would be necessary under these circumstances.

Further, unlike the procedures described in the service bulletin, this proposed AD would provide for terminating action for the repetitive inspections for repaired inspection zones.

Cost Impact

There are approximately 235 airplanes of the affected design in the worldwide fleet. The FAA estimates that 117 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 48 work hours per airplane to accomplish the proposed inspection, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $336,960, or $2,880 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

Regulatory Impact

The regulations proposed herein 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. Therefore, it is determined that this proposal would not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this 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) if promulgated, 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. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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. 106(g), 40113, 44701.