AD 96-22-09

This amendment adopts a new airworthiness directive (AD), applicable to certain Shorts Model SD3-60 and SD3-SHERPA series airplanes, that requires a one-time inspection to detect cracks and/or corrosion of the gland nut on the shock absorber of the main landing gear (MLG), and follow-on actions. This amendment also requires repair or replacement of any cracked/corroded gland nut with a new nut. This amendment is prompted by a report indicating that, due to stress corrosion and cracking of the gland nut on the shock absorber, the MLG collapsed on an in-service airplane. The actions specified by this AD are intended to detect and correct such stress corrosion or cracking in a timely manner and consequent reduced structural integrity of the gland nut, which could result in separation of the shock absorber cylinder from the MLG shock absorber body and, consequently, lead to the collapse of the MLG during landing.

Final rule

96-22-09 SHORT BROTHERS, PLC: Amendment 39-9797. Docket 96-NM-09-AD.
Applicability: Model SD3-60 and Model SD3-SHERPA series airplanes, as listed in Shorts Service Bulletin SD360-32-34 (for Model SD3-60 series airplanes), and Shorts Service Bulletin SD3 SHERPA-32-2 (for Model SD3-SHERPA series airplanes), both dated September 22, 1995; 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 (c) 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 detect and correct stress corrosion or cracking of the gland nut on the shock absorber of the main landing gear (MLG) in a timely manner and consequent reduced structural integrity of the nut, which could result in separation of the shock absorber cylinder from the MLG shock absorber body and, consequently, lead to the collapse of the MLG during landing; accomplish the following:

(a) Within 90 days after the effective date of this AD, perform a one-time visual and fluorescent dye penetrant inspection to detect cracks and/or corrosion of the gland nut on the shock absorber of the MLG, in accordance with Shorts Service Bulletin SD360-32-34 (for Model SD3-60 series airplanes), and Shorts Service Bulletin SD3 SHERPA-32-2 (for Model SD3-SHERPA series airplanes), both dated September 22, 1995,as applicable.

NOTE 2: Shorts Service Bulletins SD360-32-34 and SD3 SHERPA-32-2 reference Messier- Dowty Service Bulletin 32-78SD, dated July 19, 1995, as an additional source of service information.

(1) If no crack and/or corrosion is detected, no further action is required by paragraph (a) of this AD.

(2) If no crack is detected, but corrosion is detected that is within the limits specified in the service bulletin, prior to further flight, repair the gland nut in accordance with the applicable service bulletin.

(3) If any crack is detected, or if any corrosion is detected that is outside the limits specified in the service bulletin, prior to further flight, replace the gland nut with a new gland nut, in accordance with the applicable service bulletin.

(b) Following accomplishment of paragraph (a) of this AD, prior to further flight, apply grease to the threads of the cylinder, and apply sealant to the inner radius of the gland nut, in accordance with Shorts Service Bulletin SD360-32-34 (for Model SD3-60 series airplanes), and Shorts Service Bulletin SD3 SHERPA-32-2 (for Model SD3-SHERPA series airplanes), both dated September 22, 1995, as applicable.

(c) 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 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113.

(d) 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.

(e) The actions shall be done in accordance with Shorts Service Bulletin SD360-32-34, dated September 22, 1995, and Shorts Service Bulletin SD3 SHERPA-32-2, dated September 22, 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.

(f) This amendment becomes effective on December 11, 1996.

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 Shorts Model SD3-60 and SD3-SHERPA series airplanes was published in the Federal Register on July 29, 1996 (61 FR 39364). That action proposed to require a one-time visual and fluorescent dye penetrant inspection to detect cracks and/or corrosion of the gland nut on the shock absorber of the main landing gear (MLG), and repair or replacement of the gland nut with a new nut, if necessary. That action also proposed to require, after the inspection is completed, the application of grease to the threads of the cylinder and the application of sealant to the inner radius of the gland nut.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the single comment received.

The commenter supports the proposed rule.

Conclusion
After careful review of the available data, including the comment noted above, 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 88 airplanes (72 Model SD3-60 series airplanes and 16 Model SD3- SHERPA series airplanes) of U.S. registry will be affected by this AD, that it will take approximately 5 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 $26,400, 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 Subjectsin 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: