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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 96-NM-143-AD] 
          - RIN 2120-AA64 

# 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 Gulfstream Aerospace Corporation Model G-159 airplanes. This proposal would require repetitive non-destructive testing inspections to detect corrosion of the skin of certain structural assemblies, and corrective action, if necessary. This                               ( print page 30344)                            proposal also would require x-ray and ultrasonic inspections to detect corrosion and cracking of the splicing of certain structural assemblies, and repair, if necessary. This action is necessary to detect and correct corrosion of the skin of certain structural assemblies, which could cause local instability failures of the wing under certain load conditions and result in degradation of wing capability. This action is intended to address the identified unsafe condition.                     

# DATES:

Comments must be received by July 23, 2001. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 96-NM-143-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. Comments may be submitted via fax to (425) 227-1232. Comments may also be sent via the Internet using the following address: 9-anm-nprmcomment@faa.gov. Comments sent via fax or the Internet must contain “Docket No. 96-NM-143-AD” in the subject line and need not be submitted in triplicate. Comments sent via the Internet as attached electronic files must be formatted in Microsoft Word 97 for Windows or ASCII text. 

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 31402-9980. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the FAA, Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas. 

# FOR FURTHER INFORMATION CONTACT:

Neil Berryman, Aerospace Engineer, Airframe and Propulsion Branch, ACE-117A, FAA, Atlanta Aircraft Certification Office, One Crown Center, 1895 Phoenix Boulevard, suite 450, Atlanta, Georgia 30337-2748; telephone (770) 703-6087; 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 action may be changed in light of the comments received. 

Submit comments using the following format: 
    - Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
    - For each issue, state what specific change to the proposed AD is being requested.
    - Include justification (e.g., reasons or data) for each request.

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 action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 96-NM-143-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. 96-NM-143-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. 

## Discussion 

The method of fabrication on Gulfstream Aerospace Corporation Model G-159 airplanes of spotwelding to join two layers of material precludes the use of any corrosion inhibitor on the faying surfaces. Therefore, corrosion can form by the entrance and entrapment of moisture or other corrosive agents between layers of the metal. The FAA has received reports that exfoliation corrosion has been found in the lower layer of the lower wing plank splices. This corrosion typically follows the grain boundaries into the ramp-up area. As a consequence of such corrosion, cracking may occur in the risers adjacent to the splices of the lower wing planks. This action is necessary to detect and correct corrosion of the skin of certain structural assemblies, which could cause local instability failures of the wing under certain load conditions and result in degradation of wing capability. 

## Explanation of Relevant Service Information 

The FAA has reviewed and approved Gulfstream Customer Bulletin (CB) No. 337, dated December 10, 1993, which describes procedures for certain repetitive non-destructive testing (NDT) inspections to detect corrosion on certain areas (ailerons, elevators, rudder, flaps, horizontal stabilizer, vertical stabilizer, and aft fuselage skins, as well as lower wing plank splices). The CB also describes procedures for replacing components, if necessary. Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition. 

Gulfstream has also issued Gulfstream Tool No. ST905-377, an x-ray negative that is a comparison chart, which describes specific levels of corrosion, and describes criteria for determining those levels of corrosion (“light,” “moderate,” and “severe”). 

## 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, except as discussed below. 

## Differences Between the CB and the Proposed Rule 

Operators should note that the Gulfstream CB recommends that the compliance time for the initital NDT inspections should be 18 months from the release of the CB (December 10, 1993). However, this proposed AD would require the initial inspection within 9 months after the effective date of the AD. Operators also should note that, although the Gulfstream CB does not specify certain corrective actions for levels of corrosion, this proposed AD would require shortened repetitive intervals for the NDT inspections based on certain levels of corrosion, or replacement of the corroded component with a serviceable component. 

## Cost Impact 

                    There are approximately 144 Gulfstream Model G-159 airplanes of the affected design in the worldwide fleet. The FAA estimates that 71 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 80 work hours per airplane to accomplish the                           ( print page 30345)                        proposed actions, 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 $340,800, or $4,800 per airplane, per inspection cycle.                 

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 proposed AD were not adopted. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. 

## 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. 

§ 39.13 

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

**Gulfstream Aerospace Corporation:**                                 Docket 96-NM-143-AD.                            

*Applicability:*                                 All Model G-159 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 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 (d) 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 corrosion of the skin of certain structural assemblies, which could cause local instability failures of the wing under certain load conditions and result in degradation of wing capability; accomplish the following: 

(a) Within 9 months after the effective date of this AD, perform a non-destructive test (NDT) to detect corrosion of the skins of the aileron rudder, rudder trim tab, flap, evaluator, fuselage, vertical stabilizer, and horizontal stabilizer; in accordance with Gulfstream Aerospace GI Customer Bulletin No. 337, dated December 10, 1993. 

(1) If no corrosion is detected, repeat the NDT inspections thereafter at intervals not to exceed 18 months. 

(2) If any corrosion is detected that meets the criteria of “light” corrosion, as defined by Gulfstream Tool No. ST905-377, repeat the NDT inspections of that component thereafter at intervals not to exceed 12 months. 

(3) If any corrosion is detected that meets the criteria of “moderate” corrosion, as defined by Gulfstream Tool No. ST905-377, repeat the NDT inspection of that component thereafter at intervals not to exceed 9 months. 

(4) If any corrosion is detected that meets the criteria of “severe” corrosion, as defined by Gulfstream Tool No. ST905-377, prior to further flight, replace the component with a serviceable component, in accordance with the Gulfstream I Maintenance Manual. 

(b) Within 9 months after the effective date of this AD, perform a non-destructive test (NDT) to detect corrosion of the lower wing plank splices, in accordance with Gulfstream Aerospace GI Customer Bulletin No. 337, dated December 10, 1993. 

(1) If no corrosion is detected, repeat the NDT inspection at intervals not to exceed 18 months. 

(2) If any corrosion is detected, prior to further flight, repair in accordance with the customer bulletin. 

## Reporting Requirement 

                                (c) Within 10 days of performing the inspections required by paragraph (a) of this AD: Submit a report of inspection findings (both positive and negative) to Gulfstream Aerospace Corporation; Attention: Technical Operations—Mail Station D-10; P.O. Box 2206; Savannah, Georgia 31402-0080. 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.                             

## Alternative Methods of Compliance 

(d) 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, Wichita Aircraft Certification Office (ACO), FAA. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Wichita ACO. 

# Note 2:

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

## Special Flight Permits 

(e) 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 May 29, 2001. 

Vi L. Lipski, 

Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 01-14145 Filed 6-5-01; 8:45 am] 

BILLING CODE 4910-13-U