Airworthiness Directives; Saab Model SAAB 2000 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 Saab Model SAAB 2000 series airplanes. This proposal would require repetitive detailed visual and dye penetrant inspections of the backup struts in the left and right nacelles to detect discrepancies; and corrective actions, if necessary. This proposal is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by the proposed AD are intended to prevent failure of the backup struts in the left and right nacelles due to fatigue cracking, which could result in loss of fail-safe redundancy in the design of the nacelle in terms of load capability.

DATES:

Comments must be received by June 9, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 99-NM-368-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.

The service information referenced in the proposed rule may be obtained from Saab Aircraft AB, SAAB Aircraft Product Support, S-581.88, Linköping, Sweden. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Norman B. Martenson, Manager, International Branch, ANM-116, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-2110; 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 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 99-NM-368-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. 99-NM-368-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

The Luftfartsverket (LFV), which is the airworthiness authority for Sweden, recently notified the FAA that an unsafe condition may exist on certain Saab Model SAAB 2000 series airplanes. The LFV advises that field experience has revealed fatigue cracking in the internal backup struts in the forward part of the nacelle structure. Such cracking was found in the area of the welded splices for the upper and lower attachment fittings. In the lower end of the attachment fittings, cracks were found near the local cut-out in the tube or areas adjacent to the welding, and in the upper area in the radius of the attachment fittings. On one occasion, fatigue cracks resulted in complete failure of the backup strut. Such fatigue cracking, if not corrected, could result in failure of the backup struts in the left and right nacelles, which could result in loss of fail-safe redundancy in the design of the nacelle in terms of load capability.

Explanation of Relevant Service Information

The manufacturer has issued Saab Service Bulletin 2000-54-023, Revision 01, dated January 28, 2000, which describes procedures for repetitive detailed visual and dye penetrant inspections of the backup struts in the left and right nacelles to detect discrepancies; and corrective actions, if necessary. Descriptions of the two types of inspections are as follows:

• The initial detailed visual inspection includes the upper areas of the backup strut around the welding in the pipe and in the attachment fittings.
• The initial dye penetrant inspection, using a Penetrant Type 1 (fluorescent dye) sensitivity level 2, includes the lower areas of the backup strut around the welding in the pipe and in the attachment fittings, and specifies taking special care to check the inside edge of the cutouts.

If any inspection reveals a failed backup strut, procedures include the following additional inspections of the engine mount surrounding structure:

• Detailed visual inspections of each engine mount strut and mounting fittings, forward semi-circular collar/frame and aft beam, nacelle backup strut opposite side to the failed backup strut and attachment fittings at station 176/199, inboard and outboard upper and lower longerons of the nacelle, and upper and lower longerons at the attachment to the inboard and outboard upper and lower fittings of the nacelle.
• General visual inspections of the inner and outer side walls and side of the skin panels.

Discrepancies include fatigue cracking, a failed backup strut, and damage to the surrounding structure of the engine mount. Corrective actions include replacing any failed backup strut located in the hydraulic bay or electrical bay areas with a new backup strut, and performing additional inspections of the surrounding structure of the engine mount.

The LFV classified this service bulletin as mandatory and issued Swedish airworthiness directive No. 1-150R1, dated January 31, 2000, in order to assure the continued airworthiness of these airplanes in Sweden.

FAA's Conclusions

This airplane model is manufactured in Sweden 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 LFV has kept the FAA informed of the situation described above. The FAA has examined the findings of the LFV, 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 the service bulletin described previously, except as described below.

Differences Between Proposed AD and Service Bulletin

Operators should note that, although the service bulletin specifies that the manufacturer may be contacted for repair instructions for certain damage conditions, this proposed AD would require the repair of those conditions to be accomplished in accordance with a method approved by either the FAA or the LFV (or its delegated agent). In light of the type of repair that would be required to address the identified unsafe condition, and in consonance with existing bilateral airworthiness agreements, the FAA has determined that a repair approved by either the FAA or the LFV would be acceptable for compliance with this proposed AD.

Interim Action

This is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking.

Cost Impact

The FAA estimates that 3 airplanes of U.S. registry would be affected by this proposed AD, that it would take approximately 8 work hours per airplane to accomplish the proposed inspections, 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 $1,440, or $480 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 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.

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.