AD 99-17-01

This amendment adopts a new airworthiness directive (AD) that applies to certain Pilatus Aircraft Ltd. (Pilatus) Models PC-12 and PC-12/45 airplanes. This AD requires replacing all flap drive shafts with flap drive shafts of improved design, installing additional gaskets on the power drive unit, and modifying the attachment and supporting hardware. 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 the flap drive shafts from corroding to the point where the flexible shafts in the flap drive system rupture, which could result in the inability to utilize the flap system with reduced airplane control.

Final rule.

99-17-01 PILATUS AIRCRAFT LTD.: Amendment 39-11250; Docket No. 99-CE-20-AD.

Applicability: Models PC-12 and PC-12/45 airplanes, manufacturer serial number (MSN) 101 through 239, 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 (d) 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 inthe body of this AD, unless already accomplished.

To prevent the flap drive shafts from corroding to the point where the flexible shafts in the flap drive system rupture, which could result in the inability to utilize the flap system with reduced airplane control, accomplish the following:

(a) Within the next 4 calendar months after the effective date of this AD, accomplish the following in accordance with the Accomplishment Instructions section of Pilatus Service Bulletin No. 27-003, dated March 8, 1999:

(1) Replace all flap drive shafts with flap drive shafts of improved design (part numbers as specified in paragraphs (b)(1) and (b)(2) of this AD);

(2) Install additional gaskets on the power drive unit; and

(3) Modify the attachment and supporting hardware.

(b) As of the effective date of this AD, no person may install, on any affected airplane, a flap drive shaft assembly that is not of the following part numbers (or FAA-approved equivalent part numbers):

(1) Part number 945.02.02.201: Flap Drive Shaft 953D100-5 (Inboard); and

(2) Part-number 945.02.02.202: Flap Drive Shaft 953D100-7 (Outboard).

NOTE 2: The FAA recommends that the owner/operator of the affected airplanes insert Pilatus Temporary Revision No. 27-07, dated January 8, 1999, into the PC12 Maintenance Manual at the same time this AD is accomplished to assure that the maintenance procedures for the improved design parts are current.

(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) An alternative method of compliance or adjustment of the compliance time that provides an 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 throughan appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Small Airplane Directorate.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Small Airplane Directorate.

(e) Questions or technical information related to Pilatus Service Bulletin No: 27-003, dated March 8, 1999, should be directed to Pilatus Aircraft Ltd., Customer Liaison Manager, CH-6371 Stans, Switzerland; telephone: +41 41 619 63 19; facsimile: +41 41 610 33 51. 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.

(f) The replacements, installations, and modification required by this AD shall be done in accordance with Pilatus Service Bulletin No: 27-003, dated March 8, 1999. 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-6371 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 4: The subject of this AD is addressed in Swiss AD HB 99-241, dated May 8, 1999.

(g) This amendment becomes effective on October 1, 1999.

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 Models PC-12 and PC-12/45 airplanes was published in the Federal Register as a notice of proposed rulemaking (NPRM) on June 14, 1999 (64 FR 31756). The NPRM proposed to require replacing all flap drive shafts with flap drive shafts of improved design, installing additional gaskets on the power drive unit, and modifying the attachment and supporting hardware. Accomplishment of the proposed action as specified in the NPRM would be required in accordance with Pilatus Service Bulletin No. 27-003, dated March 8, 1999.

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.

Compliance Time of This AD
The unsafe condition specified by this AD is caused by corrosion. Corrosion can occur regardless of whether the aircraft is being operated. For example, corrosion could develop on one of the affected airplanes at a certain time; then, if allowed to go undetected, the corrosion could develop into a more serious problem even if the airplane is in storage. Therefore, to assure that the unsafe condition specified in this AD does not go undetected for a long period of time, the compliance is presented in calendar time instead of hours time-in-service (TIS).

Cost Impact
The FAA estimates that 69 airplanes in the U.S. registry will be affected by this AD, that it will take approximately 19 workhours per airplane to accomplish this action, and that the average labor rate is approximately $60 an hour. Parts will be provided by the manufacturer to the owners/operators of the affected aircraft free-of-charge. Based on these figures, the total cost impact of this AD on U.S. operators is estimated to be $78,660, or $1,140 per airplane.

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 federalismimplications 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: