Airworthiness Directives; Saab Model SAAB SF340A and SAAB 340B Series Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to certain Saab Model SAAB SF340A and SAAB 340B series airplanes, that currently requires inspections to detect damage or cracking of the forward and aft attachment lugs of the flap fittings at wing station (WS) 123.38; an inspection to verify that the sizes of the holes of the flap fittings are within specified limits and to ensure that the swaged bushings are not loose; and modification of the flap fittings. This action would require repetitive accomplishment of the inspections using improved inspection methods; a one-time visual and repetitive general visual and detailed visual inspections; new repetitive non-destructive test (NDT) inspections; and corrective and follow-on actions, as necessary. This action also would provide for terminating action for all repetitive inspections and would revise the applicability of the existing AD. The actions specified by the proposed AD are intended to prevent high bearing stress on the bushings of the flap fittings, which could result in wear on the bushings, cracking of the flap fittings, and breakage of the lugs; these conditions could result in jamming of the flaps and consequent reduced controllability of the airplane.

DATES:

Comments must be received by August 30, 2000.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), Transport Airplane Directorate, ANM-114, Attention: Rules Docket No. 2000-NM-76-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. 2000-NM-76-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 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, 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 2000-NM-76-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. 2000-NM-76-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.

Discussion

On January 14, 1997, the FAA issued AD 96-25-06 R1, amendment 39-9891 (62 FR 3209, January 22, 1997), applicable to certain Saab Model SAAB SF340A and SAAB 340B series airplanes, to require inspections to detect damage or cracking of the forward and aft attachment lugs of the flap fittings at wing station (WS) 123.38; an inspection to verify that the sizes of the holes of the flap fittings are within specified limits and to ensure that the swaged bushings are not loose; and modification of the flap fittings. That action was prompted by a report of jamming of a flap due to incorrect tolerances of the flap-hinge installation, which caused high bearing stress on the bushings in the flap fitting. The requirements of that AD are intended to prevent high bearing stress, which could result in wear on the bushings, cracking of the flap fittings, and breakage of the lugs; these conditions could result in jamming of the flaps and consequent reduced controllability of the airplane.

Actions Since Issuance of Previous Rule

Since the issuance of that AD, the Luftfartsverket (LFV), which is the airworthiness authority for Sweden, has advised the FAA that the L-shaped flap fittings at WS 123.38, where the triangular flap fitting is installed, have failed in some cases due to fatigue. Investigation revealed that the initial failure occurred in the aft attachment lug where the swaged bushing is installed, which led to a failure in the bottom radius of the adjacent L-shaped fitting. The LFV further advises that the inspection methods specified by Saab Service Bulletin 340-57-027, Revision 01, dated June 30, 1995, and required in AD 96-25-06 R1, are inadequate to detect cracking of the forward and aft attachment lugs at WS 123.38. In that inspection, it is possible for small cracks to pass by undetected. Over time, these small cracks could cause failure of certain components of the flap fittings at WS 123.38.

The LFV also advises that, bushings with incorrect length may have been installed at the forward attachment point to the triangular fitting. Bolts and bushings with incorrect lengths also may have been installed at the aft attachment point. Consequently, high bearing stress can occur to the bushings and on the L-fittings due to short bushings and bolts.

In light of the recent events, the manufacturer has released new service information, and the FAA has determined that it is necessary to perform a new, one-time visual inspection, repetitive general and detailed visual inspections, and repetitive non-destructive test (NDT) inspections to enable early detection of discrepancies of the affected area.

Explanation of Relevant Service Information

The manufacturer has issued SAAB Service Bulletins 340-57-035, 340-57-037, and 340-57-038, each dated January 18, 2000, which describe procedures for the following:

• Saab Service Bulletin 340-57-035: One-time visual inspection of the flap assemblies to determine the serial numbers. If certain flap assemblies (as listed in the service bulletin) are installed, the follow-on actions include repetitive visual inspections of the affected flap assemblies (forward and aft attachment lugs) of the flap fittings at WS 123.38 to detect cracking or damage. The service bulletin also references Saab Service Bulletin 340-57-037 for performing NDT inspection of the aft attachment lugs of the flap fittings at WS 123.38 to detect cracking; and detailed visual inspections of the flap fittings to determine the size of the inboard and outboard holes (swaged bushings) and to detect loose swaged bushings. If no discrepancies (incorrectly sized hole, loose swaged bushings, or cracking) are detected, the service bulletin describes procedures for installing new fasteners (nuts, bolts, bushings, and washers) that attach to the flap hinges. If any discrepancy (as described previously) is detected during the visual or NDT inspection, the service bulletin refers to Saab Service Bulletin 340-57-038 for replacement of all flap fittings.
• Saab Service Bulletin 340-57-037: One-time visual inspection of the aft attachment lugs (flap assemblies) of the flap fittings at WS 123.38 to determine the flap assembly modification status. If any flap assembly is installed that has a thinner lug, the follow-on actions include repetitive visual inspections of the aft attachment lugs of the flap fittings at WS 123.38 to detect cracking or damage. If any cracking or damage is detected, the service bulletin refers to Saab Service Bulletin 340-57-038 for replacement of all flap fittings. The service bulletin also describes procedures for repetitive NDT inspections of the aft attachment lugs of the flap fittings at WS 123.38 to detect cracking. If any cracking is detected, the service bulletin refers to Saab Service Bulletin 340-57-038 for replacement of the flap fittings.
• Saab Service Bulletin 340-57-038: Replacement of the flap fittings at WS 123.38, with new, improved flap fittings. Accomplishment of the replacement of all flap fittings would eliminate the need for all inspections specified by Service Bulletins 340-57-035 and 340-57-037, as described previously.

The LFV classified Saab Service Bulletins 340-57-035 and 340-57-037 as mandatory and issued Swedish airworthiness directives No. 1-152 and No. 1-153, each dated January 19, 2000, to assure the continued airworthiness of these airplanes in Sweden.

FAA's Conclusions

These airplane models are manufactured in Sweden and are 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 is likely to exist or develop on other airplanes of the same type design registered in the United States, the proposed AD would supersede all requirements of AD 96-25-06 R1. This proposed AD would require a new, one-time visual inspection; new repetitive general visual and detailed visual inspections; and a new repetitive NDT inspection; and corrective and follow-on actions, as necessary. The proposed AD also would provide for terminating action for the repetitive inspections, would revise the applicability of the existing AD to apply only to airplanes on which a certain flap assembly is installed, and would add airplanes that may be subject to the unsafe condition. The actions would be required to be accomplished in accordance with the Saab service bulletins described previously.

Cost Impact

The FAA estimates that 303 airplanes of U.S. registry would be affected by this proposed AD.

It would take approximately 1 work hour per airplane to accomplish the proposed repetitive general visual inspections, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed general visual inspections on U.S. operators is estimated to be $18,180, or $60 per airplane, per inspection cycle.

It would take approximately 1 work hour per airplane to accomplish the proposed one-time general visual inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed general visual inspection on U.S. operators is estimated to be $18,180, or $60 per airplane.

It would take approximately 1 work hour per airplane to accomplish the proposed repetitive detailed visual inspections, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed detailed visual inspections on U.S. operators is estimated to be $18,180, or $60 per airplane, per inspection cycle.

It would take approximately 2 work hours per airplane to accomplish the proposed repetitive NDT inspections, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the proposed NDT inspections on U.S. operators is estimated to be $36,360, or $120 per airplane, per inspection cycle.

The cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the current or proposed requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

Should an operator be required or elect to accomplish the terminating modification, it would take approximately 92 work hours per airplane (46 work hours per flap), at an average labor rate of $60 per hour. Required parts would cost $7,362 per airplane ($3,681 per flap). Based on these figures, the cost impact of the terminating modification on U.S. operators is estimated to be $12,882 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.