AD 96-15955

[Federal Register Volume 61, Number 122 (Monday, June 24, 1996)] [Proposed Rules] [Pages 32369-32371] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 96-15955]

======================================================================== Proposed Rules Federal Register ________________________________________________________________________ This section of the FEDERAL REGISTER contains notices to the public of the proposed issuance of rules and regulations. The purpose of these notices is to give interested persons an opportunity to participate in the rule making prior to the adoption of the final rules. ========================================================================

Federal Register / Vol. 61, No. 122 / Monday, June 24, 1996 / Proposed Rules

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-202-AD] RIN 2120-AA64

Airworthiness Directives; Gulfstream Model G-1159 (G-II), G-1159A (G-III), and G-1159B (G-IIB) Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Gulfstream Model G-II, G-III, and G-IIB series airplanes. This proposal would require a one-time inspection to detect corrosion of the material layers of the lower aft fuselage skin in Fuselage Station (FS) 580 bulkhead assembly, and repair, if necessary. The proposal also would require modification of the aft fuselage area and various follow-on actions. This proposal is prompted by reports of varying levels of corrosion in the structure at FS 580. The actions specified by the proposed AD are intended to prevent the retention of moisture in the fuselage structure, and subsequent corrosion in FS 580 bulkhead assembly, which could result in reduced structural capability of the skin joint and resultant depressurization of the airplane.

DATES: Comments must be received by August 2, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-103, Attention: Rules Docket No. 95-NM-202-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 Gulfstream Aerospace Corporation, P.O. Box 2206, M/S D- 10, Savannah, Georgia 31402-2206. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: Steve Flanagan, Aerospace Engineer, Airframe Branch, ACE-117A, FAA, Atlanta Aircraft Certification Office, Small Airplane Directorate, Campus Building, 1701 Columbia Avenue, Suite 2-160, College Park, Georgia; telephone (404) 305-7363; fax (404) 305-7348.

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 95-NM-202-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-103, Attention: Rules Docket No. 95-NM-202-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The FAA has received reports of varying levels of pitting and exfoliation corrosion found in the material layers of the lower aft fuselage skin of Fuselage Station (FS) 580 on Gulfstream Model G-II series airplanes. This corrosion was detected by operators while performing visual inspections of the bulkhead area during routine maintenance checks. FS 580 is the location where the aft pressure dome ties into the fuselage. This FS consists of ``multiple stackup material,'' such as: a splice strap, fail-safe strap, skin, frame, stringers, longeron, and the pressure dome. Corrosion in this area is apparently caused by the accumulation of moisture, due to condensation in the unpressurized aft fuselage. This condition, if not corrected, could result in reduced structural capability of the skin joint and resultant depressurization of the airplane. Since the aft pressure bulkhead area on the Model G-II series airplanes is similar to that on Model G-III and Model and G-IIB series airplanes, all of these models may be subject to this same unsafe condition.

Explanation of Relevant Service Information

The FAA has reviewed and approved Gulfstream Customer Bulletin No. 411 (for Model G-II and G-IIB series airplanes) and No. 125 (for Model G-III series airplanes), both dated January 28, 1994. These customer bulletins describe procedures for a one-time visual inspection or an inspection using backscattered radiation detection technique (ComScan) to detect corrosion in the FS 580 bulkhead assembly. In addition, the FAA has reviewed and approved Gulfstream Aircraft Service Change No. 463 (for Model G-II and GIIB series airplanes) and No. 267 (for Model G-III series airplanes), both dated July 21, 1995. These aircraft service changes describe procedures to: 1. add pressure sealing drain holes in the aft fuselage area, which will provide drain paths for condensed water that has accumulated; 2. remove aluminum-backed foam from the bays below the floor; 3. modify the fuselage structure; 4. modify the intercoastals; 5. drill drain holes in the area of Longeron #24L and Stringer #23L, and Longeron #24R and Stringer #23R; and

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6. treat the structural surfaces with corrosion inhibitors.

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 a one-time inspection to detect corrosion of FS 580, and repair, if necessary. This inspection could be accomplished using either detailed visual inspection techniques or ComScan techniques. This proposed AD also would require that operators submit a report to the FAA of the findings of this inspection. The information obtained from these reports will enable the FAA to determine how widespread the problem is in the fleet and if additional action is warranted. In addition, the proposed AD would require: 1. adding pressure sealing drain holes in the aft fuselage area; 2. removing aluminum-backed foam; 3. modifying the fuselage structure; 4. modify the intercostals; 5. drill drain holes in the area of Longeron #24L and Stringer #23L, and Longeron #24R and Stringer #23R; and 6. treat the structural surfaces with corrosion inhibitors. Repair of corrosion would be required to be accomplished in accordance with a method approved by the FAA. Other actions would be required to be accomplished in accordance with the Gulfstream customer bulletins and aircraft service changes described previously. This is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking.

Differences Between the Proposed Rule and Relevant Service Information

Operators should note that, in the relevant service documents, the manufacturer recommends that the one-time inspection be accomplished within 18 months for Model G-II and G-IIB series airplanes, and within 36 months for Model G-III series airplanes. In developing an appropriate compliance time for this proposed rule, the FAA took into consideration not only those recommended compliance times, but the safety implications, normal maintenance schedules for timely accomplishment of the inspection, and the number of days usually required for the rulemaking process. In consideration of all of these factors, the FAA finds that the compliance times for the one-time inspection as proposed in this action (6 months for Model G-11 and G- IIB series airplanes, and 12 months for Model G-III series airplanes) will fall approximately at the same time of compliance as recommended by the manufacturer.

Cost Impact

There are approximately 425 Gulfstream Model G-II, G-IIB, and G-III series airplanes of the affected design in the worldwide fleet. The FAA estimates that 345 airplanes of U.S. registry would be affected by this proposed AD. To accomplish the one-time inspection using detailed visual inspection techniques (which requires some disassembly) would take approximately 1,500 work hours per airplane. To accomplish the one-time visual inspection using ComScan techniques would take approximately 16 work hours per airplane. The average labor rate is $60 per work hour. Based on these figures, the cost impact of the proposed one-time inspection on U.S. operators is estimated to be between $960 and $90,000 per airplane, depending upon the type of inspection performed. To accomplish the proposed modification would take approximately 80 work hours per airplane, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed modification on U.S. operators is estimated to $1,656,000, or $4,800 per airplane. The cost impact figures discussed above are 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 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 proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. 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.

Sec. 39.13 [Amended]

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

Gulfstream: Docket 95-NM-202-AD.

Applicability: All Model G-1159 (G-II), G-1159A (G-III), and G- 1159B (G-IIB) series airplanes; certificated in any category.

Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 (e) 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 prevent reduced structural capability of the skin joint and resultant depressurization of the airplane, as a result of the problems associated with corrosion of the structure surfaces aft of fuselage station (FS) 580, accomplish the following: (a) For Model G-II and G-IIB series airplanes: Within 6 months after the effective date of this AD, perform a detailed visual inspection, or perform an inspection using a backscattered radiation detection technique (ComScan), to detect corrosion of the FS

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580 bulkhead, in accordance with Gulfstream Customer Bulletin No. 411, dated January 28, 1994. If any corrosion is found, prior to further flight, repair in accordance with a method approved by the Manager, Atlanta Aircraft Certification Office (ACO), FAA, Small Airplane Directorate. (b) For Model G-III series airplanes: Within 12 months after the effective date of this AD, perform a one-time detailed visual inspection, or perform an inspection using a backscattered radiation detection technique (ComScan), to detect corrosion of the FS 580 bulkhead, in accordance with Gulfstream Customer Bulletin No. 125, dated January 28, 1994. If any corrosion is found, prior to further flight, repair in accordance with a method approved by the Manager, Atlanta ACO. (c) For all airplanes: Within 10 days after accomplishing the inspection required by paragraph (a) or (b) of this AD, submit a report of the inspection results (both positive and negative findings) to the FAA, Manager, Atlanta Aircraft Certification Office, Campus Building, 1701 Columbia Avenue, Suite 2-160, College Park, Georgia 30338-2748; fax (404) 305-7333. The report must include the information specified in paragraphs (d)(1), (d)(2), (d)(3), and (d)(4) of this AD. Information collection requirements contained in this regulation have been approved by the Office of Management and Budget (OMB) under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have been assigned OMB Control Number 2120-0056. (1) Airplane model, serial number, date of manufacture, and total number of hours time-in-service. (2) Date of inspection, and method of inspection. (3) Summary of inspection results, including extent and location of corrosion. (4) List of parts replaced, if applicable. (d) For all airplanes: Within 12 months after the effective date of this AD, add pressure sealing drain holes in the aft fuselage area; remove all the aluminum-backed foam insulation from the skins in the bays between Longerons #24 left and #24 right from FS 539 through FS 580 inclusive; modify the fuselage structure; modify the intercostals; drill drain holes in the area of Longeron #24L and Stringer #23L, and Longeron #24R and Stringer #23R; and treat the structural surfaces with corrosion inhibitor; in accordance with either paragraph (c)(1) or (c)(2) of this AD, as applicable. (1) For Model G-II and G-IIB series airplanes: Perform the actions in accordance with Gulfstream Aircraft Service Change No. 463, dated July 21, 1995. (2) For Model G-III series airplanes: Perform the actions in accordance with Gulfstream Aircraft Service Change No. 267, dated July 21, 1995. (e) 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.

(f) 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.

Issued in Renton, Washington, on June 17, 1996. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 96-15955 Filed 6-21-96; 8:45 am] BILLING CODE 4910-13-U