04-6680. Airworthiness Directives; Short Brothers Model SD3-60 SHERPA 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 Short Brothers Model SD3-60 SHERPA series airplanes. This proposal would require repetitive inspections and torque tests for discrepancies of certain bolts and rivets; and related investigative and corrective actions. This action is necessary to detect and correct loose bolts that attach the vertical stabilizer to the horizontal stabilizer, and pulled or loose rivets in the upper shear angles, which could result in reduced structural integrity of the vertical stabilizer. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by April 26, 2004.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2003-NM-200-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056. Comments may be inspected at this location between 9 a.m. and 3 p.m., Monday through Friday, except Federal holidays. Comments may be submitted via fax to [phone]. Comments may also be sent via the Internet using the following address: [e-mail]. Comments sent via fax or the Internet must contain “Docket No. 2003-NM-200-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 or 2000 or ASCII text.

The service information referenced in the proposed rule may be obtained from Short Brothers, Airworthiness & Engineering Quality, P.O. Box 241, Airport Road, Belfast BT3 9DZ, Northern Ireland. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Todd Thompson, Aerospace Engineer, International Branch, ANM-116, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone [phone]; fax [phone].

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 2003-NM-200-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. 2003-NM-200-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The Civil Aviation Authority (CAA), which is the airworthiness authority for the United Kingdom, notified the FAA that an unsafe condition may exist on all Short Brothers Model SD3-60 SHERPA series airplanes. The CAA advises that during an unscheduled inspection of an SD3-60 SHERPA airplane, some of the bolts that attach the vertical stabilizer to the horizontal stabilizer were found to be loose. This condition, if not corrected, could result in reduced structural integrity of the vertical stabilizer.

Explanation of Relevant Service Information

Short Brothers has issued Service Bulletin SD3-60 Sherpa-55-1, dated June 6, 2003, which describes procedures for inspecting and performing torque tests to detect the following discrepancies: Loose bolts that attach the vertical stabilizer to the horizontal stabilizer; and loose or pulled rivets in the upper shear angles. The service bulletin recommends repeating these inspections and torque tests every 1,500 flight hours, and reporting all findings to the manufacturer.

If any discrepancy is found during any inspection, the service bulletin describes the procedures for related investigative and corrective actions. The related investigative action is a further inspection to detect worn or distorted bolts, and worn or elongated bolt holes. The related corrective actions are:

• Fitting a new bolt with a new stiffnut and sufficient washers to ensure that the nut does not neck at full torque. This includes opening up a worn or elongated hole to oversize diameter, if necessary; and reporting any elongated holes that cannot be removed by oversizing to Short Brothers PLC.
• Replacing any discrepant shear angle using oversize rivets.

Accomplishment of the actions specified in the service bulletin is intended to adequately address the identified unsafe condition. The CAA classified this service bulletin as mandatory and issued British airworthiness directive 001-06-2003 to ensure the continued airworthiness of these airplanes in the United Kingdom.

FAA's Conclusions

This airplane model is manufactured in the United Kingdom and is type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the CAA has kept the FAA informed of the situation described above. The FAA has examined the findings of the CAA, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.

Explanation of Requirements of Proposed AD

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, the proposed AD would require accomplishment of the actions specified in the service bulletin described previously, except as discussed below.

Differences Between the Proposed AD and the Service Bulletin

Although the service bulletin specifies that operators may contact the manufacturer for disposition of certain repair conditions, this proposal would require operators to repair those conditions per a method approved by either the FAA or the CAA (or its delegated agent). In light of the type of repair that would be required to address the unsafe condition, and consistent with existing bilateral airworthiness agreements, we have determined that, for this proposed AD, a repair approved by either the FAA or the CAA would be acceptable for compliance with this proposed AD.

Operators should note that, although the Accomplishment Instructions of the referenced service bulletin describe procedures for submitting findings to the manufacturer, this proposed AD would not require those actions.

Clarification Between the Proposed AD and the Service Bulletin

Although the service bulletin does not specify the type of inspection, this proposed AD would require a “detailed inspection.” We have included a note in the proposed AD to clarify the definition of a detailed inspection.

Cost Impact

The FAA estimates that 27 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 5 work hours per airplane to accomplish the proposed inspections and torque tests, and that the average labor rate is $65 per work hour. Based on these figures, the cost impact of the proposed AD on U.S. operators is estimated to be $8,775, or $325 per airplane, per inspection/test 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 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

[Amended]

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

Short Brothers PLC: Docket 2003-NM-200-AD.

Applicability: All Short Brothers Model SD3-60 SHERPA series airplanes, certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To detect and correct loose bolts that attach the vertical stabilizer to the horizontal stabilizer, and pulled or loose rivets in the upper shear angles, which could result in reduced structural integrity of the vertical stabilizer, accomplish the following:

Repetitive Inspections and Torque Tests and Related Investigative Action

(a) Prior to the accumulation of 1,500 total flight hours, or within 2 months after the effective date of this AD, whichever occurs later: Perform a detailed inspection, including a torque test, to detect discrepancies in the bolts or bolt holes that attach the vertical stabilizer to the horizontal stabilizer; and to detect loose or pulled rivets in the upper shear angles. Repeat the detailed inspection and torque test at intervals not to exceed 1,500 flight hours. If any discrepancy is found in the bolts or bolt holes, do the related investigative action before further flight. Accomplish all actions in accordance with the Accomplishment Instructions of Short Brothers Service Bulletin SD3-60 Sherpa-55-1, dated June 6, 2003.

Note 1:

For the purposes of this AD, a detailed inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required.”

Related Corrective Actions

(b) If any discrepancy is found during any inspection or torque test required by paragraph (a) of this AD: Before further flight, repair in accordance with the Accomplishment Instructions of Short Brothers Service Bulletin SD3-60 Sherpa-55-1, dated June 6, 2003. Where the service bulletin specifies to contact the manufacturer for disposition of certain repair conditions: Before further flight, repair per a method approved by either the Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate; or the Civil Aviation Authority or its delegated agent.

No Reporting Requirement

(c) Although the service bulletin referenced in this AD specifies to submit certain information to the manufacturer, this AD does not include such a requirement.

Alternative Methods of Compliance

(d) In accordance with 14 CFR 39.19, the Manager, International Branch, ANM-116, is authorized to approve alternative methods of compliance for this AD.

Note 2:

The subject of this AD is addressed in British airworthiness directive 001-06-2003.

Issued in Renton, Washington, on March 19, 2004.

Kevin M. Mullin,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.