AD 98-12-01

This amendment adopts a new airworthiness directive (AD) that applies to certain Pilatus Aircraft Ltd. (Pilatus) Models PC-6, PC-6/A, PC-6/B, and PC-6/C series airplanes equipped with turbo-prop engines. This AD requires modifying the fuel system to improve the venting between the collector tank, the main wing tanks, and the engine. This AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Switzerland. The actions specified by this AD are intended to prevent engine fuel starvation during maximum climb and descent caused by poor fuel tank venting with low fuel levels, which could result in a loss of engine power during critical phases of flight.

Final rule.

98-12-01 PILATUS AIRCRAFT LTD: Amendment 39-10558; Docket No. 97-CE-09-AD.

Applicability: Models PC-6, PC-6-H1, PC-6-H2, PC-6/350, PC-6/350-H1, PC-6/350-H2, PC-6/A, PC-6/A-H1, PC-6/A-H2, PC-6/B-H2, PC-6/B1-H2, PC-6/B2-H2, PC-6/B2-H4, PC-6/C-H2, and PC-6/C1-H2 airplanes, serial numbers 001 through 915, certificated in any category, that are equipped with turbo-prop engines.

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 within the next 3 calendar months after the effective date of this AD, unless already accomplished.

To prevent engine fuel starvation during maximum climb and descent caused by poor fuel tank venting with low fuel levels, which could result in a loss of engine power during critical phases of flight, accomplish the following:

(a) Modify the fuel venting system in accordance with the Accomplishment Instructions section in Pilatus PC-6 Service Bulletin No. PC-6-SB-171, dated October 18, 1995.

(b) 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.

(c) An alternative method of compliance or adjustment of the compliance time that providesan equivalent level of safety may be approved by the Manager, Small Airplane Directorate, 1201 Walnut, suite 900, Kansas City, Missouri 64106. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Small Airplane Directorate.

NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Small Airplane Directorate.

(d) Questions or technical information related to Pilatus Service Bulletin No. PC-6-SB-171, dated October 18, 1995, should be directed to Pilatus Aircraft Ltd., Customer Liaison Manager, CH-6370 Stans, Switzerland; telephone: +41 41-6196 233; facsimile: +41 41-6103 351. This service information may be examined at the FAA, Central Region, Office of the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106.

(e) The modification required by this AD shall be done in accordance with Pilatus Service Bulletin No. PC-6-SB-171, dated October 18, 1995. 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 Pilatus Aircraft Ltd., Customer Liaison Manager, CH-6370 Stans, Switzerland. Copies may be inspected at the FAA, Central Region, Office of the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, 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 Swiss AD HB 95-451, dated November 1, 1995.

(f) This amendment becomes effective on July 13, 1998.

Events Leading to the Issuance of This AD
A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to certain Pilatus PC-6, PC-6/A, PC-6/B, and PC-6/C series airplanes was published in the Federal Register as a notice of proposed rulemaking (NPRM) on March 25, 1998 (63 FR 14385). The NPRM proposed to require modifying the airplane's fuel venting system. Accomplishment of the proposed action as specified in the NPRM would be in accordance with Pilatus PC-6 Service Bulletin No. PC-6-SB-171, dated October 18, 1995.

The NPRM was the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Switzerland.

Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were received on the proposed rule or the FAA's determination of the cost to the public.

The FAA's Determination
After careful review of all available information related to the subject presented above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed except for minor editorial corrections. The FAA has determined that these minor corrections will not change the meaning of the AD and will not add any additional burden upon the public than was already proposed.

Differences Between the Service Information, the Federal Office for Civil Aviation (FOCA) AD, and This AD Action
The manufacturer recommends the modification of the fuel venting system and the insertion of a temporary revision to the AFM, and FOCA of Switzerland requires the temporary AFM insertion and the modification of the fuel venting system for airplanes operated in Switzerland. The FOCA of Switzerland requires the AFM revision be accomplished prior to further flight and requires the revision to remain in the AFM until the venting modification is accomplished. The FOCA of Switzerland additionally requires that the modification be accomplished within 90 days from receipt of the service bulletin.

The FAA will not require insertion of the temporary AFM revision; however, the FAA will require the modification of the fuel venting system at the calendar compliance time that is required by the FOCA of Switzerland.

Cost Impact
The FAA estimates that 29 airplanes in the U.S. registry will be affected by this AD, that it will take approximately 10 workhours per airplane to accomplish this action, and that the average labor rate is approximately $60 an hour. Parts cost approximately $614 per airplane. Based on these figures, the total cost impact of this AD on U.S. operators is estimated to be $35,206, or $1,214 per airplane.

Compliance Time of This AD
Since the airplane's poor fuel tank venting causes engine fuel starvation during flights at maximum climb and decent, this unsafe condition is not a result of the number of times the airplane is operated. The chance of this situation occurring is the same for an airplane with 10 hours time-in-service (TIS) as it would be for an airplane with 500 hours TIS. For this reason, the FAA has determined that a compliance based on calendar time should be utilized in this AD in order to assure that the unsafe condition is addressed on all airplanes in a reasonable time period.

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 copy of the final evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting 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 a new airworthiness directive (AD) to read as follows: