# AGENCY:

 Federal Aviation Administration, DOT. 

# ACTION:

 Final rule. 

# SUMMARY:

 This amendment adopts a new airworthiness directive (AD), applicable to all Short Brothers Model SD3-60 SHERPA and SD3-SHERPA series airplanes, and certain Model SD3-30 series airplanes, that requires replacement of existing oxygen system “O” rings with improved wear-resistant “O” rings. 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 the loss of oxygen from the aircraft oxygen system, which could result in an insufficient supply of oxygen being provided to the airplane flight crew and passengers in the event of an emergency. 

# DATES:

 Effective February 29, 2000.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of February 29, 2000. 

# ADDRESSES:

 The service information referenced in this AD may be obtained from Short Brothers, Airworthiness & Engineering Quality, P.O. Box 241, Airport Road, Belfast BT3 9DZ, Northern Ireland. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. 

# 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:

                     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 Short Brothers Model SD3-60 SHERPA, SD3-SHERPA, and SD3-30 series airplanes was published in the                     **Federal Register**                     on October 6, 1999 (64 FR 54237). That action proposed to require replacement of existing oxygen system “O” rings with improved wear-resistant “O” rings.                 

## Comment Received 

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

One commenter requests that the applicability of the proposed AD be revised to include only those Model SD3-30 series airplanes on which an oxygen system is installed. The commenter states that only one variant of these airplanes was delivered in this configuration, and provides a list of the applicable serial numbers. The commenter notes that these serial numbers are also listed in Shorts Service Bulletin SD330-35-1, dated February 25, 1999, which is referenced as the appropriate source of service information in the proposed AD. 

The FAA concurs that the requirements of the AD are applicable only to those airplanes on which an oxygen system is installed. The FAA has limited the applicability for Model SD3-30 series airplanes to those listed in Shorts Service Bulletin SD330-35-1, dated February 25, 1999, and has revised the Summary section of the AD to refer to “certain,” rather than “all,” Model SD3-30 series airplanes. 

## 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 with the change described previously. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD. 

## Cost Impact 

The FAA estimates that 62 airplanes of U.S. registry will be affected by this AD, that it will take approximately 50 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts will be provided by the manufacturer at no cost to operators. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $186,000, or $3,000 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 

2. Section 39.13 is amended by adding the following new airworthiness directive: 

**2000-02-02 Short Brothers PLC:**                        Amendment 39-11520. Docket 99-NM-223-AD.                     

*Applicability:*                        All Model SD3-60 SHERPA and SD3-SHERPA series airplanes; and Model SD3-30 series airplanes as listed in Shorts Service Bulletin SD330-35-1, dated February 25, 1999; 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 prevent the loss of oxygen from the aircraft oxygen system, accomplish the following: 

## Replacement 

(a) Within 24 months after the effective date of this AD, replace oxygen system “O” rings, part number (P/N) MS28778, with improved wear-resistant “O” rings, P/N MS9068, in accordance with Shorts Service Bulletins SD360 Sherpa-35-2, dated February 25, 1999 (for Model SD3-60 Sherpa series airplanes); SD3 Sherpa-35-3, Revision 1, dated May 5, 1999 (for Model SD3 Sherpa series airplanes); and SD330-35-1, dated February 25, 1999 (for Model SD3-30 series airplanes); as applicable. 

## Spares 

(b) As of the effective date of this AD, no person shall install an oxygen system “O” ring, P/N MS28778, on any airplane. 

## Alternative Methods of Compliance 

(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, 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 2:

 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 

(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. 

## Incorporation by Reference 

(e) The actions shall be done in accordance with Shorts Service Bulletin SD3-60 Sherpa-35-2, dated February 25, 1999; Shorts Service Bulletin SD3 Sherpa-35-3, Revision 1, dated May 5, 1999; or Shorts Service Bulletin SD330-35-1, dated February 25, 1999; as applicable. Shorts Service Bulletin SD3 Sherpa-35-3, Revision 1, dated May 5, 1999, contains the following list of effective pages: 

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, Airworthiness & Engineering Quality, P.O. Box 241, Airport Road, Belfast BT3 9DZ, Northern Ireland. 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 3:

 The subject of this AD is addressed in British airworthiness directives 007-02-99 (for Model SD3-60 Sherpa series airplanes), 006-02-99 (for Model SD3 Sherpa series airplanes), and 008-02-99 (for Model SD3-30 series airplanes). 

(f) This amendment becomes effective on February 29, 2000.

Issued in Renton, Washington, on January 14, 2000. 

Donald L. Riggin, 

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. 

[FR Doc. 00-1502 Filed 1-24-00; 8:45 am] 

BILLING CODE 4910-13-U