AD 94-25-04

This amendment adopts a new airworthiness directive (AD), applicable to certain Precision Airmotive Corporation (formerly Facet Aerospace Products and Marvel-Schebler) Model HA-6 series carburetors, that requires a modification in those carburetors not equipped with a mixture control retainer clip. This amendment is prompted by eight reports of excessive retention screw wear causing rough engine operation or engine power loss on engines equipped with a Model HA-6 series carburetor between January 1986 and August 1992. The actions specified by this AD are intended to prevent the interruption of fuel flow to the engine caused by the mixture control shaft moving out of position because of excessive wear of the mixture control shaft retention screw.

Final rule.

94-25-04 Precision Airmotive Corporation (formerly Facet Aerospace Products and Marvel-Schebler): Amendment 39-9088. Docket 93-ANE-29.

Applicability: Precision Airmotive Corporation (formerly Facet Aerospace Products and Marvel-Schebler) Model HA-6 series carburetors with part numbers 10-5092, 10-5180, 10-5189, 10-5200, 10-5200-1, 10-5201-11, 10-5206, 10-5206-1, 10-5210, 10-5211, 10-5211-1, 10-5214, 10-5215, 10-5221, 10-5227. These carburetors are installed on but not limited to reciprocating engine powered aircraft manufactured by Beech, Cessna, Piper, and Mooney.

Compliance: Required as indicated, unless accomplished previously.

To prevent the interruption of fuel flow to the engine caused by the mixture control shaft moving out of position because of excessive wear of the mixture control shaft retention screw, accomplish the following:

(a) For affected carburetors not equipped with a mixture control shaft retainer clip (P/N 55-A239), screw (P/N 15-B395),and washer (P/N 78-A292), install these items within 12 months after the effective date of this airworthiness directive (AD) in accordance with Marvel-Schebler/Tillotson Service Bulletin (SB) No. A1-78, dated September 1978, or Precision Airmotive Corporation SB No. MSA-6, dated April 6, 1994.

(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, Seattle Aircraft Certification Office. The request should be forwarded through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle Aircraft Certification Office. NOTE: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Seattle Aircraft Certification Office.

(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 aircraft to a location where the requirements of this AD can be accomplished.

(d) The installation shall be done in accordance with the following service bulletins:

Document No.
Pages
Date

Marvel Schebler/
Tillotson SB No. A1-78
1-2
September 1978

Total Pages: 2.

Precision Airmotive
Corporation SB No. MSA-6
1-3
April 6, 1994

Total Pages: 3.

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 Precision Airmotive Corporation, 3220 - 100th Street Southwest, Suite E, Everett, WA 98204; telephone (206) 353-8181, fax (206) 348-3545. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street NW., suite 700, Washington, DC.

(e) This amendment becomes effective on February 13, 1995.

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 Precision Airmotive Corporation (formerly Facet Aerospace Products and Marvel-Schebler) Model HA-6 series carburetors was published in the Federal Register on December 21, 1993 (58 FR 67381). That action proposed to require installation of a retainer clip, replacement screw, and washer to prevent movement of the existing mixture control shaft in the event of excessive wear of the mixture control shaft retainer screw, in accordance with Marvel-Schebler/Tillotson Service Bulletin (SB) No. A1-78, dated September 1978.

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

The commenter (the manufacturer) states that only certain part numbers of HA-6 series carburetors should be affected by the AD. The affected carburetors were manufactured prior to 1979, after which a modification to address mixture control shaft retention problems was introduced and the part numbers were changed. The Federal Aviation Administration (FAA) concurs. The applicability of this final rule has been revised to include only carburetors identified by certain part numbers. In addition, the manufacturer has issued Precision Airworthiness Corporation Mandatory SB No. MSA-6, dated April 6, 1994, that includes the revised effectivity limited by part numbers. This final rule adds this SB as an additional means of compliance to the original Marvel-Schebler/Tillotson SB. Finally, the economic analysis has been revised to show the lower number of affected carburetors.

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.

There are approximately 5,000 carburetors of the affected design in the worldwide fleet, but the number of carburetors installed on aircraft of U.S. registry that will be affected by this AD is unknown. The FAA estimates that it will take approximately 1 work hour per carburetor to accomplish the required actions, and that the average labor rate is $55 per work hour. Required parts will cost approximately $34 per carburetor. Based on these figures, the total cost impact of the AD on worldwide operators is estimated to be $445,000.

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. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

39.13 - [AMENDED]
2. Section 39.13 is amended by adding the following new airworthiness directive: