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PROPOSED AD 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:

(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 Busin-
    ess 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.

Issued on  July 14, 2021. Lance T. Gant,  Director, Compliance & Airworth-
iness Division, Aircraft Certification Service.

DATES: The FAA must receive comments on this proposed AD by September
7, 2021.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration


14 CFR Part 39

[Docket No. FAA-2021-0573; Project Identifier 2018-CE-046-AD]
RIN 2120-AA64

Airworthiness Directives; Pilatus Aircraft Ltd. Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for Pilatus Aircraft Ltd. (Pilatus) Models PC-12/45, PC-12/47, and PC-
12/47E airplanes with Supplemental Type Certificate (STC) SA00634DE
installed. This proposed AD was prompted by a report of strake
attachment brackets and the fuselage frame failing at the upper most
bracket attachment location. This proposed AD would require inspecting
the strake, attachment brackets, surrounding structure, and bolts and
replacing components and repairing damage if necessary. The FAA is
proposing this AD to address the unsafe condition on these products.

DATES: The FAA must receive comments on this proposed AD by September
7, 2021.

ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:

Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow
the instructions for submitting comments.

Fax: (202) 493-2251.

Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.

Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this NPRM, 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 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.

Examining the AD Docket


You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0573; or in person at
Docket Operations between 9 a.m. and 5 p.m., Monday through Friday,
except Federal holidays. The AD docket contains this NPRM, any comments
received, and other information. The street address for Docket
Operations is listed above.

FOR FURTHER INFORMATION 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.

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
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:

Estimated Costs

ACTION
LABOR COST
PARTS COST
COST PER PRODUCT
COST ON U.S. OPERATORS
Inspection of the strake assemblies. 1 work-hour x $85 per hour = $85 per inspection cycle. Not applicable. $85 per inspection cycle. $2,550 per inspection cycle.

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.

List of Subjects in 14 CFR Part 39


Air transportation, Aircraft, Aviation safety, Incorporation by
reference, Safety.

The Proposed Amendment


Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 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.

Sec. 39.13 [Amended]


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