SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under ADDRESSES . Include “Docket No. FAA-2021-0573; Project Identifier 2018-CE-046-AD” at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend this proposal because of those comments.

Except for Confidential Business Information (CBI) as described in the following paragraph, and other information as described in 14 CFR 11.35, the FAA will post all comments received, without change, to https://www.regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM.

Confidential Business Information

CBI is commercial or financial information that is both customarily and actually treated as private by its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments responsive to this NPRM contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this NPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI as “PROPIN.” The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this NPRM. Submissions containing CBI should be sent to Richard R. Thomas, Aviation Safety Engineer, Denver ACO Branch, FAA, 26805 E 68th Avenue, Denver, CO 80249. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking.

Background

The FAA received a report that an operator found that one of the fuselage strakes was “loose having excess play” on two different Pilatus Model PC-12/47E airplanes. Further inspection found the fuselage main frame at frame station 40 and the strake attachment brackets had cracks extending from the attachment bolt hole at the upper most attachment location. Both airplanes had a SPECTRE Lift Platform System, STC SA00634DE, installed. The deployment of the lift platform causes buffeting of the strakes. This condition, if not addressed, could result in airplane flutter and reduced lateral stability, which may lead to loss of control of the airplane.

FAA's Determination

The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Pilatus Service Bulletin PC-12 Series, Report Number 12-1700-64-0000, Revision B, dated August 10, 2018 (Pilatus Report 12-1700-64-0000B), which contains procedures for inspection of all fuselage strake attachment bolts and the surrounding structure. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in ADDRESSES .

Proposed AD Requirements in This NPRM

This proposed AD would require inspecting the strake, attachment brackets, and bolts for movement and damage, both internal and external, and replacing or repairing any damaged parts.

Differences Between This Proposed AD and the Service Information

Pilatus Report 12-1700-64-0000B specifies a one-time inspection within 10 flight hours of issuance of the SB and recommends repeat inspections without specifying an inspection interval. This ( printed page 38614) proposed AD would require repeating the inspection every 150 flight hours. Pilatus Report 12-1700-64-0000B specifies contacting Pilatus for further instructions. This proposed AD would require using an FAA-approved repair method. Pilatus Report 12-1700-64-0000B applies to Pilatus PC-12 aircraft serial numbers 190 to 1575. This proposed AD would apply to all Pilatus Aircraft Ltd. Models PC-12/45, PC-12/47, and PC-12/47E airplanes, regardless of serial number, if STC SA00634DE is installed.

Interim Action

The FAA considers this AD an interim action. Pilatus is working on a modification with the intent of minimizing, if not eliminating, the buffeting of the strakes. Once this action is developed, approved, and available, the FAA may consider additional rulemaking.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 30 airplanes of U.S. registry.

The FAA estimates the following costs to comply with this proposed AD:

The extent of damage found during the proposed inspections may vary considerably from airplane to airplane. The FAA has no way of knowing how many airplanes may have damage or the extent of damage each airplane may have.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority.

The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: General requirements. Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would 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.

For the reasons discussed above, I certify this proposed regulation:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Would not affect intrastate aviation in Alaska, and

(3) Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

2. The FAA amends § 39.13 by adding the following new airworthiness directive:

Pilatus Aircraft Ltd.: Docket No. FAA-2021-0573; Project Identifier 2018-CE-046-AD.

(a) Comments Due Date

The FAA must receive comments on this airworthiness directive (AD) by September 7, 2021.

(b) Affected ADs

None.

(c) Applicability

This AD applies to Pilatus Aircraft Ltd. (Pilatus) Models PC-12/45, PC-12/47, and PC-12/47E airplanes, all serial numbers, certificated in any category, with a Spectre Lift Platform System installed in accordance with Supplemental Type Certificate No. SA00634DE.

(d) Subject

Joint Aircraft System Component (JASC) Code 5350, Aerodynamic Faring.

(e) Unsafe Condition

This AD was prompted by a report of the strake attachment brackets and surrounding structure failing at the upper most bracket bolt hole. The FAA is issuing this AD to detect and address any looseness or damage to the strake, attachment brackets or surrounding structure, and missing fasteners or loose bolts, which could result in airplane flutter and reduced lateral stability, which may lead to loss of control of the airplane.

(f) Compliance

Comply with this AD within the compliance times specified, unless already done.

(g) Inspection and Corrective Actions

Within 10 hours time-in-service (TIS) after the effective date of this AD and thereafter at intervals not to exceed 150 hours TIS, inspect the outside and inside fuselage strakes for movement, the strakes and their attachment brackets for loose and missing bolts and screws, and the strake attachment brackets and surrounding structure for discoloration, deformation, cracks, and other structural damage by following the Accomplishment Instructions—Aircraft, steps A through B.(3) and C.(1) through C.(5), in Pilatus Service Bulletin PC-12 Series, Report Number 12-1700-64-0000, Revision B, dated August 10, 2018.

(1) You must accomplish the inside fuselage inspection regardless of the results of the outside fuselage inspection.

(2) If any movement of the strakes, a loose or missing bolt or screw, discoloration, deformation, a crack, or other structural damage is found during any of the inspections, before further flight, repair using FAA-approved procedures.

(h) Special Flight Permit

A special flight permit may be issued to allow flying the airplane to a maintenance facility where repair of the strake assembly will be performed with the following operating limitations: ( printed page 38615)

(1) Flight must be conducted under visual flight rules, daytime only; and

(2) The Spectre Lift Platform System, STC SA00634DE, must be retracted (not deployed) during the flight.

(i) Alternative Methods of Compliance (AMOCs)

(1) The Manager, Denver ACO Branch, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the manager of the certification office, send it to the attention of the person identified in Related Information.

(2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office.

(j) Related Information

(1) For more information about this AD, contact Richard R. Thomas, Aviation Safety Engineer, Denver ACO Branch, FAA, 26805 E 68th Avenue, Denver, CO 80249; phone: (303) 342-1080; fax: (303) 342-1088; email: 9-Denver-Aircraft-Cert@faa.gov.

(2) For service information identified in this AD, contact Pilatus Business Aircraft Ltd., Customer Support Department, 12300 Pilatus Way, Broomfield, CO 80021; phone: (866) 721-2435; fax: (303) 465-9099; email: productsupport@pilbal.com. You may view this referenced service information at the FAA, Airworthiness Products Section, Operational Safety Branch, 901 Locust, Kansas City, MO 64106. For information on the availability of this material at the FAA, call (816) 329-4148.