AD 96-21-07

This amendment adopts a new airworthiness directive (AD), applicable to all Shorts Model SD3-30, -60, and -SHERPA series airplanes, that requires a visual inspection to detect signs of exfoliation corrosion on the brackets of the flap hydraulic units, and rework or replacement of corroded brackets. This amendment is prompted by a report that exfoliation corrosion was found on the brackets of the flap hydraulic units. The actions specified by this AD are intended to prevent such corrosion, and consequent reduced structural integrity of the brackets of the flap hydraulic units, which could result in the loss of the flap control and consequent reduced controllability of the airplane.

Final rule

96-21-07 SHORT BROTHERS, PLC: Amendment 39-9784. Docket 96-NM-08-AD.
Applicability: All Model SD3-30, -60, and -SHERPA series airplanes, 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 (b) 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 on the brackets of the flap hydraulic units, and consequent reduced structural integrity of those brackets, which could result in the loss of the flap control and consequent reduced controllability of the airplane, accomplish the following:

(a) Within 90 days after the effective date of this AD, perform a visual inspection to detect signs of exfoliation corrosion on the brackets of the flap hydraulic units, in accordance with Shorts Service Bulletin SD330-27-34 (for Model SD3-30 series airplanes); Shorts Service Bulletin SD360-27-24 (for Model SD3-60 series airplanes); or Short Service Bulletin SD3 SHERPA-27-1 (for Model SD3-SHERPA series airplanes); all dated September 12, 1995; as applicable.

(1) If no corrosion is detected, accomplish paragraph (a)(1)(i) or (a)(1)(ii) of this AD, as applicable.

(i) For Model SD3-30 and -60 series airplanes: Repeat the visual inspection thereafter at intervals not to exceed 2,400 hours or 12 months, whichever occurs first.

(ii) For Model SD3-SHERPA series airplanes: Repeat the visual inspection thereafter at intervals not to exceed 12 months.

(2) If any corrosion is detected and it is within the limits specified in the applicable service bulletin, prior to further flight, rework the subject area in accordance with the applicable service bulletin. After accomplishment of the rework, accomplish paragraph (a)(2)(i) or (a)(2)(ii) of this AD, as applicable.

(i) For Model SD3-30 and -60 series airplanes: Repeat the visual inspection thereafter at intervals not to exceed 600 hours or 6 months, whichever occurs first.

(ii) For Model SD3-SHERPA series airplanes: Repeat the visual inspection thereafter at intervals not to exceed 6 months.

(3) If any corrosion is detected and it is outside the limits specified in the applicable service bulletin, prior to further flight, replace the bracket with a new bracket in accordance with the applicable service bulletin.

(b) 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, Standardization Branch, ANM-113, 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, Standardization Branch, ANM-113.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113.

(c) 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.

(d) The actions shall be done in accordance with Shorts Service Bulletin SD330-27-34, dated September 12, 1995; Shorts Service Bulletin SD360-27-24, dated September 12, 1995; or Shorts Service Bulletin SD3 SHERPA-27-1; dated September 12, 1995; as applicable. 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 Short Brothers PLC, 2011 Crystal Drive, Suite 713, Arlington, Virginia 22202-3719. 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.

(e) This amendment becomes effective on November 29, 1996.

FOR FURTHER INFORMATION CONTACT: Greg Dunn, Aerospace Engineer, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2799; fax (206) 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 all Shorts Model SD3-30, -60, and -SHERPA series airplanes was published in the Federal Register on July 12, 1996 (61 FR 36669). That action proposed to require a visual inspection to detect signs of exfoliation corrosion on the brackets of the flap hydraulic units, and rework or replacement of corroded brackets.

Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were submitted in response to the proposal or the FAA's determination of the cost to the public.

Conclusion
The FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

Cost Impact
The FAA estimates that 138 airplanes (50 Model SD3-30 series airplanes, 72 Model SD3-60 series airplanes, and 16 Model SD3-SHERPA series airplanes)of U.S. registry will be affected by this AD. It will take approximately 5 work hours per airplane to accomplish the required actions, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $41,400, or $300 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 substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

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: