AD 2000-12-07

This amendment adopts a new airworthiness directive (AD), applicable to certain Saab Model SAAB SF340A and SAAB 340B series airplanes, that requires a one-time inspection to detect corrosion and scratches on the bearing housing surfaces of the support assembly on the main landing gear (MLG), and corrective actions, if necessary. This amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this AD are intended to prevent corrosion in the inboard and outboard bearing housings of the MLG support assembly, which could result in fatigue cracks in the support assembly and lead to failure of the MLG.

Final rule.

2000-12-07 SAAB AIRCRAFT AB: Amendment 39-11785. Docket 99-NM-51-AD.

Applicability: Model SAAB SF340A, serial numbers -004 through -159 inclusive; and SAAB 340B series airplanes, serial numbers -160 through -444 inclusive; 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 prevent corrosion in the inboard and outboard bearing housings of the support assembly of the main landing gear (MLG), which could result in fatigue cracks in the support assembly and lead to failure of the MLG, accomplish the following:

Initial Inspection
(a) At the applicable time specified in paragraph (a)(1), (a)(2), (a)(3), or (a)(4) of this AD: Perform a one-time general visual inspection of the eight bearing housing surfaces of the MLG to detect corrosion or scratches, in accordance with Saab Service Bulletin 340-57-036, dated October 20, 1999.

(1) For airplanes with 32,000 or more total flight cycles as of the effective date of this AD, the inspection is to be performed within 4,000 flight cycles after the effective date of this AD.

(2) For airplanes with 24,000 or more and fewer than 32,000 total flight cycles as of the effective date of this AD, the inspection is to be performed within 6,000 flight cycles after the effective date of this AD.

(3) For airplanes with 12,000 or more and fewer than 24,000 total flight cycles as of the effective date of this AD, the inspection is to be performed prior to the accumulation of 24,000 total flight cycles, or within 6,000 flight cycles after the effective date of this AD, whichever occurs later.

(4) For airplanes with fewer than 12,000 total flight cycles as of the effective date of this AD, the inspection is to be performed prior to the accumulation of 12,000 total flight cycles, or within 6,000 flight cycles after the effective date of this AD, whichever occurs later.

NOTE 2: For the purposes of this AD, a general visual inspection is defined as: "A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure, or irregularity. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight, or drop-light, and may require removal or opening of access panels or doors. Stands, ladders, or platforms may be required to gain proximity to the area being checked."

Corrective Actions
(b) Except as provided by paragraph (c) of this AD: If, during the inspection required by paragraph (a) of this AD, any corrosion or scratch is detected that is within the limits specified in Saab Service Bulletin 340-57-036, dated October 20, 1999, prior to further flight, perform corrective actions (including rework, an eddy current inspection, and repair) in accordance with Steps 2.B. and 2.C. of the Accomplishment Instructions of the service bulletin.

(1) If, after rework, the depth of the damage is less than or equal to 0.15 mm (0.006 inches) AND the damage does not exceed 15 percent of the area, no further action is required by this AD.

(2) If, after rework, the depth of the damage exceeds 0.15 mm (0.006 inches) but is less than or equal to 1.1 mm (0.043 inches), AND the damage does not exceed 30 percent of the area: Within 4,000 flight cycles after accomplishment of the inspection required by paragraph (a), repair the MLG support assembly in accordance with the service bulletin. Following the repair, no further action is required by this AD.

(c) If, during any inspection required by this AD, a discrepancy is detected for which the service bulletin specifies to contact Saab for appropriate action [including any crack or any corrosion or scratch that exceeds 1.1 mm (0.043 in) after applicable rework has been performed as required by paragraph (b) of this AD]: Prior to further flight, repair in accordance with a method approved by the Manager, International Branch, ANM-116, Transport Airplane Directorate; or the Luftfartsverket (LFV) (or its delegated agent). For a repair method to be approved by the Manager, International Branch, ANM-116, as required by this paragraph, the Manager's approval letter must specifically reference this AD.

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, International Branch, ANM-116, FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, International Branch, ANM-116.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the International Branch, ANM-116.

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.

Incorporation by Reference
(f) Except as specified by paragraph (c) of this AD, the inspections and corrective actions shall be done in accordance with Saab Service Bulletin 340-57-036, dated October 20, 1999. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Saab Aircraft AB, SAAB Aircraft Product Support, S-581.88, Link ping, Sweden. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

NOTE 4: The subject of this AD is addressed in Swedish airworthiness directive 1-146, dated October 20, 1999.

(g) This amendment becomes effective on July 20, 2000.

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.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Saab Model SAAB SF340A and SAAB 340B series airplanes was published in the Federal Register on January 5, 2000 (65 FR 395). That action proposed to require a one-time inspection to detect corrosion and scratches on the bearing housing surfaces of the support assembly on the main landing gear, and corrective actions, if necessary.

Consideration of Comments Received
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the two comments received.

Request to Include Optional Repair Procedure to This AD
One commenter, an operator, requests that the optional repair procedure, included in a note in step 2.C.(1)(b)10 of the Accomplishment Instructions of Saab Service Bulletin 340-57-036, dated October 20, 1999, be added to the proposed AD. That procedure specifies certain options for follow-on repair based on the depth and extent of damage after rework. One option would require repair of the main landing gear (MLG) support assembly within 4,000 flight cycles after the inspection. Another option would require reinstalling the bearings for the MLG assembly and continuing to operate the airplane an additional 4,000 flight cycles before the final repair is accomplished. The commenter adds that [without having these options] "we foresee a serious maintenance-scheduling issue" due to the large number of Saab Model SAAB 340 series airplanes in its fleet (presently 115).

The FAA concurs with the commenter's request to include in this AD the two options specified in the service bulletin. Although those options were inadvertently omitted in the proposed AD, both options are included in this AD. The FAA has determined that, for damage within certain limits after rework, deferral of the final repairof the MLG support assembly for 4,000 flight cycles will adequately address the identified unsafe condition and is acceptable for the requirements of this AD.

Request to Revise Cost Estimate
One commenter states that "unless there is a policy to address inspections only and not include preparation, corrective action, and close up costs, the costs are underestimated in the NPRM." The service bulletin includes detailed costs for the actions specified, which include access, inspection, corrective actions, close up, and test. The commenter adds that, if operators accomplish those actions when the MLG's are removed for overhaul or repair, no extra costs are necessary for the removal/reinstallation of shock struts and drag braces. However, if such actions are not accomplished during overhaul or repair of the MLG's, removal/installation will require an additional 8 hours. In addition, the costs will vary according to the damage found.

The FAA does not concur with the commenter's request to revise the cost impact information presented in the proposed AD, which describes only the "direct" costs of the specific actions required by this AD. The number of work hours necessary to accomplish the required actions, specified as 2 work hours in the cost impact information, below, was provided to the FAA by the manufacturer based on the best data available to date. That number represents the time necessary to perform only the actions actually required by this AD. The FAA recognizes that, in accomplishing the requirements of any AD, operators may incur "incidental" costs in addition to the "direct" costs. However, the cost analysis in AD rulemaking actions typically does not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. The FAA points out that because incidental costs may vary significantly from operator to operator, they are almost impossible to calculate. For these reasons, no change to the final rule is necessary in this regard.

Explanation of Changes Made to This Final Rule
The FAA has made the following changes:
- Revised paragraph (b) and added paragraphs (b)(1) and (b)(2) in the final rule.
- Added a reference to "paragraph (b)" in paragraph (c) of the final rule.

Conclusion
After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact
The FAA estimates that 291 Model SAAB SF340A and SAAB 340B series airplanes of U.S. registry will be affected by this AD, that it will take approximately 2 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $34,920, or $120 per airplane.

The cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the 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 adopted herein will 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 final rule does not have federalism implications under Executive Order 13132.

For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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: