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Proposed Rule

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

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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.

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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.

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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. Start Printed Page 7802

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.

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List of Subjects in 14 CFR Part 39

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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:

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PART 39—AIRWORTHINESS DIRECTIVES

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

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

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[Amended]

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

Lockheed: Docket 98-NM-311-AD.

Applicability: Model L-1011-385 series airplanes, as listed in Lockheed Service Bulletin 093-53-279, dated May 6, 1998; certificated in any category.

Note 1:

This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (f) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously.

To detect and correct cracking of the fuselage skin, which could result in reduced structural integrity of the airplane, accomplish the following:

(a) Perform an ultrasonic inspection on the fuselage skin in the area of the stringerless sidewall window belts, at 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, to detect cracking in the base of the radii. Accomplish the inspection in accordance with Lockheed Service Bulletin 093-53-279, dated May 6, 1998, at each of the 6 specific inspection zones identified in the service bulletin at the later of the times specified in paragraphs (a)(1) and (a)(2) of this AD.

(1) Prior to the accumulation of 20,000 total flight cycles; or

(2) Within 600 flight cycles or 6 months after the effective date of this AD, whichever occurs first.

(b) For readings of less than 20 percent obtained at all 6 inspection zones during the ultrasonic inspection required by paragraph (a) of this AD: Repeat the ultrasonic inspection thereafter at intervals not to exceed 1,500 flight cycles.

(c) Except as provided by paragraph (e) of this AD: For any reading of 20 percent or greater and less than or equal to 50 percent obtained at any inspection zone during the ultrasonic inspection required by paragraph (a) of this AD, prior to further flight, perform a low frequency eddy current (LFEC) inspection to measure the depth of the cracking, in accordance with Lockheed Service Bulletin 093-53-279, dated May 6, 1998.

(1) If the results of the LFEC inspection are outside the reject zone, as defined in the service bulletin: Within 1,500 flight cycles, repeat both the ultrasonic and LFEC inspections specified by paragraphs (a) and (c), respectively, of this AD.

(i) If the results of the LFEC inspection specified by paragraph (c)(1) of this AD are outside the reject zone: Within 1,800 flight cycles after the initial crack finding, as detected during the ultrasonic inspection specified in paragraph (a) of this AD, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only.

(ii) If the results of the LFEC inspection specified by paragraph (c)(1) of this AD are within the reject zone: Prior to further flight, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only.

(2) If the results of the LFEC inspection are within the reject zone, as defined in the service bulletin: Prior to further flight, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only.

(d) Except as provided by paragraph (e) of this AD: For any reading of 50 percent or greater obtained at any inspection zone during the ultrasonic inspection required by paragraph (a) of this AD, prior to further flight, perform a LFEC inspection to measure the depth of the cracking, in accordance with Lockheed Service Bulletin 093-53-279, dated May 6, 1998.

(1) If the results of the LFEC inspection are outside the reject zone, as defined in the service bulletin: Within 300 flight cycles, repeat both the ultrasonic and LFEC inspections specified in paragraphs (a) and (c), respectively, of this AD.

(i) If the results of the LFEC inspection specified by paragraph (d)(1) of this AD are outside the reject zone: Within 600 flight cycles after the initial crack finding, as detected during the ultrasonic inspection specified in paragraph (a) of this AD, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only.

(ii) If the results of the LFEC inspection specified by paragraph (d)(1) of this AD are within the reject zone: Prior to further flight, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only.

(2) If the results from the LFEC inspection are within the reject zone, as defined in the service bulletin: Prior to further flight, repair any affected inspection zone in accordance with Part II of the Accomplishment Instructions of the service bulletin. Such repair constitutes terminating action for the repetitive inspection requirements of this AD for the repaired inspection zone only. Start Printed Page 7803

(e) For any inspection results that require repair in two adjacent zones: Prior to further flight, repair in accordance with a method approved by the Manager, Atlanta Aircraft Certification Office (ACO), FAA, Small Airplane Directorate.

Alternative Methods of Compliance

(f) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Atlanta ACO. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Atlanta ACO.

Note 2:

Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Atlanta ACO.

Special Flight Permits

(g) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished.

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Issued in Renton, Washington, on February 10, 2000.

Donald L. Riggin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 00-3689 Filed 2-15-00; 8:45 am]

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