Airworthiness Directives; Short Brothers Model SD3-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 certain Short Brothers Model SD3-SHERPA series airplanes. This proposal would require a repetitive detailed inspection of the stub wing shear decks for corrosion and abnormal wear on and around the retaining pin in the main landing gear (MLG) forward pintle pin; and corrective action, if necessary. This proposed AD also provides an optional terminating action. These actions are necessary to detect and correct corrosion and abnormal wear to the top and bottom shear decks, which could result in damage to the MLG and consequent reduced controllability of the airplane on landing. This action is intended to address the identified unsafe condition.

DATES:

Comments must be received by May 17, 2004.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2003-NM-235-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 (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. 2003-NM-235-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 (425) 227-1175; fax (425) 227-1149.

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-235-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-235-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 certain Short Brothers Model SD3-SHERPA series airplanes. The CAA advises that a report has been received stating that corrosion and abnormal wear to the top and bottom shear decks was found on and around the retaining pin in the main landing gear (MLG) forward pintle pin, due to loss of the retaining pin circlip, which allowed migration of the retaining pin. This condition, if not corrected, could result in damage to the MLG and consequent reduced controllability of the airplane on landing.

Explanation of Relevant Service Information

Short Brothers has issued Short Brothers Service Bulletin SD3 SHERPA-53-6, dated May 2003, which describes procedures for repetitive detailed inspections of the stub wing shear decks for corrosion and abnormal wear on and around the retaining pin in the MLG forward pintle pin; and corrective action, if necessary. The corrective action involves blending out corrosion, installing bushings in the affected shear deck, performing a visual inspection of the MLG pintle pin and sleeve for defects, and repairing any defects, as applicable. 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 airworthiness directive 004-05-2003, dated August 2003, to ensure the continued airworthiness of these airplanes in the United Kingdom.

Short Brothers has also issued Service Bulletin SD3 SHERPA-32-4, dated July 2003. That service bulletin describes procedures for replacement of the retaining pin and circlip with a new retaining pin, washer, castellated nut, and cotter pin, which would eliminate the need for repetitive detailed inspections of that retaining pin.

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 Rule

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 Short Brothers Service Bulletin SD3 SHERPA-53-6 described previously, except as discussed below.

Differences Among Proposed Rule, British Airworthiness Directive, and Referenced Service Bulletin

Although Service Bulletin SD3 SHERPA-53-6 specifies that operators may contact the manufacturer for disposition of certain corrective actions, this proposal would require operators to perform those actions 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 (or its delegated agent) would be acceptable for compliance with this proposed AD.

Operators should note that, although the referenced service bulletin describes procedures for reporting inspection results to the manufacturer, this proposed AD would not require that action. The FAA does not need this information from operators.

Operators should note that the British airworthiness directive specifies that initial inspection of the stub wing shear decks for corrosion and abnormal wear on and around the retaining pin in the MLG forward pintle pin should be accomplished no later than October 31, 2003 (which equates to a compliance time of 3 months after the effective date of the British airworthiness directive). In developing an appropriate compliance time for this proposed AD, the FAA considered not only the safety implications and the CAA's recommendations, but also the manufacturer's recommendations. In light of all of these factors, the FAA finds that the initial inspection must be accomplished within 6 months after the effective date of this AD, which represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.

Cost Impact

The FAA estimates that 16 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 13 work hours per airplane per inspection to accomplish the proposed repetitive inspections, 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 $13,520, or $845 per airplane, per inspection.

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.

If an operator chooses to accomplish the optional terminating action rather than continue the repetitive detailed inspections, it would take about 12 work hours per stub wing (2 stub wings per airplane) to accomplish the replacement of the retaining pin and circlip with a new retaining pin with castellated nut and cotter pin; at an average labor rate of $65 per work hour. Required parts would cost about $2,400 per stub wing. Based on these figures, we estimate the cost of this optional terminating action to be $6,360 per airplane.

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.