DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0857; Project Identifier MCAI-2020-00707-A]
RIN 2120-AA64

Airworthiness Directives; Pilatus Aircraft Ltd. Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Supplemental notice of proposed rulemaking (SNPRM).

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SUMMARY: The FAA is revising a notice of proposed rulemaking (NPRM) to
supersede Airworthiness Directive (AD) 2014-25-04, which applies to all
Pilatus Aircraft Ltd. (Pilatus) Model 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.
This action revises the NPRM by adding an eddy current inspection of
each fuselage wing fitting if an earlier version of the service
information was accomplished. The FAA is proposing this AD to address
the unsafe condition on these products. Since these actions would
impose an additional burden over those in the NPRM, the FAA is
requesting comments on this SNPRM.

DATES: The FAA must receive comments on this SNPRM by April 22, 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: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday
through Friday, except Federal holidays.

For service information identified in this SNPRM, contact Pilatus
Aircraft Ltd., Customer Support General Aviation, CH-6371 Stans,
Switzerland; phone: +41 848 24 7 365; email: Techsupport@pilatus-aircraft.
com; website: https://www.pilatus-aircraft.com/en. 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 on the internet at https://www.regulations.
gov by searching for and locating Docket No. FAA-2020-0857;
or in person at Docket Operations between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays. The AD docket contains
the NPRM, this SNPRM, any comments received, and other information. The
street address for Docket Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Doug Rudolph, Aviation Safety
Engineer, FAA, General Aviation & Rotorcraft Section, International
Validation Branch, 901 Locust, Room 301, Kansas City, MO 64106; phone:
(816) 329-4059; fax: (816) 329-4090; email: doug.rudolph@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-2020-0857; Project Identifier
MCAI-2020-00707-A" 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
the 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 proposed AD.

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 SNPRM 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 SNPRM, 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 SNPRM. Submissions containing CBI should
be sent to Doug Rudolph, Aviation Safety Engineer, FAA, General
Aviation & Rotorcraft Section, International Validation Branch, 901
Locust, Room 301, Kansas City, MO 64106. 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 issued an NPRM to amend 14 CFR part 39 to supersede AD
2014-25-04, Amendment 39-18045 (79 FR 73803, December 12, 2014) (AD
2014-25-04). AD 2014-25-04 applies to all Pilatus Model 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 and resulted from mandatory continuing airworthiness
information (MCAI) issued by an aviation authority of another country
to identify and correct an unsafe condition on an aviation product. AD
2014-25-04 requires incorporating revised airworthiness limitations
into the aircraft maintenance manual (AMM) for your FAA-approved
maintenance program.

The NPRM published in the Federal Register on October 2, 2020 (85
FR 62266). The NPRM was prompted by
MCAI issued by the European Union Aviation Safety Agency (EASA), which
is the Technical Agent for the Member States of the European Union.
EASA superseded its previous MCAIs on this unsafe condition with EASA
AD No. 2020-0120, dated May 27, 2020 (EASA AD 2020-0120). EASA AD 2020-
0120 states that revised airworthiness limitations for the subject
airplanes introduce new data modules that require non-destructive
visual and eddy current inspections instead of a previous requirement
for the fluorescent dye-penetrant method. In the NPRM, the FAA proposed
to require incorporating the new airworthiness limitations (revision
29) and performing an eddy current inspection of the fuselage wing
fittings and wing-to-fuselage fittings.

Actions Since the NPRM Was Issued

Since the FAA issued the NPRM, EASA superseded EASA AD 2020-0120
and issued EASA AD No. 2020-0278, dated December 14, 2020 (EASA AD
2020-0278) (also referred to after this as "the MCAI"). According to
EASA AD 2020-0278, an installation procedure specified in the service
information identified in the NPRM contained an error and, therefore,
did not adequately address the identified unsafe condition. Pilatus has
revised the airworthiness limitations (revision 30) and issued
corrected service information, which includes installing certain bushes
using grease instead of a bonding agent and an additional one-time eddy
current inspection of the fuselage wing fittings and wing-to-fuselage
fittings if the last inspection was performed using an earlier version
of the service information. You may examine the MCAI in the AD docket
on the internet at https://www.regulations.gov by searching for and
locating Docket No. FAA-2020-0857.

This SNPRM was prompted by the FAA's determination that the revised
airworthiness limitations and new inspection procedures are necessary,
in addition to the new life limits proposed in the NPRM. The FAA is
proposing this AD to address reduced airplane controllability due to
possible loss of structural integrity of certain parts.

Comments

The FAA received a comment from Pilatus. The following presents the
comment received on the NPRM and the FAA's response to that comment.

Request to Reference Latest Service Information

Pilatus requested that FAA revise the NPRM to require using Pilatus
PC-6 Aircraft Maintenance Manual Document Number 01975, Revision 30,
dated October 30, 2020; and Pilatus PC-6 Airworthiness Limitations
Document Number 02334, Revision 10, dated October 30, 2020. In support
of its request, Pilatus stated the installation procedure in the
service information specified in the NPRM is incorrect. Pilatus also
stated that it has added a note to the airworthiness limitations
section indicating the data module procedure has been corrected and
specifying a repeat of the action if it was last done in accordance
with the prior service information.

The FAA agrees. After Pilatus submitted its comment, EASA issued
the MCAI to require the revised service information, as described
previously. In this SNPRM, the FAA proposes to require the latest
service information.

Related Service Information Under 1 CFR Part 51

Pilatus issued PC-6 Airworthiness Limitations Document No. 02334,
Revision 10, dated October 30, 2020; and Section 04-00-00,
Airworthiness Limitations of Chapter 04, Airworthiness Limitations, of
the Pilatus PC-6 Aircraft Maintenance Manual Document No. 01975,
Revision 30, dated October 30, 2020. This service information contains
airworthiness limitations for the stabilizer trim actuator, fuselage
wing fittings, and wing-to-fuselage fittings. These documents are
distinct since they apply to different airplane models.

Pilatus also issued Section 53-00-01, Fuselage Wing Fittings--
Inspection/Check, of the Pilatus PC-6 Aircraft Maintenance Manual
Document No. 01975, Revision 30, dated October 30, 2020; Section 57-00-
03, Wing to Fuselage Fittings--Inspection/Check, of the PC-6 Aircraft
Maintenance Manual Document No. 01975, Revision 29, dated February 28,
2020; Appendix K, Fuselage Wing Fittings--Inspection/Check, of the PC-6
Airworthiness Limitations Document No. 02334, Revision 10, dated
October 30, 2020; and Appendix L, Wing to Fuselage Fittings--
Inspection/Check, of the PC-6 Airworthiness Limitations Document No.
02334, Revision 9, dated March 6, 2020. This service information
specifies procedures for repetitive eddy current inspections of the
fuselage wing fittings and wing-to-fuselage fittings and, if necessary,
installing the bush on the fuselage wing fittings using grease.

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 the ADDRESSES section.

FAA's Determination

This product has been approved by the aviation authority of another
country, and is approved for operation in the United States. Pursuant
to the FAA's bilateral agreement with the State of Design Authority,
the FAA has been notified of the unsafe condition described in the MCAI
and service information referenced above. The FAA is proposing this AD
because the FAA evaluated all pertinent information and determined an
unsafe condition exists and is likely to exist or develop on other
products of the same type design.

Certain changes described above expand the scope of the NPRM. As a
result, it is necessary to reopen the comment period to provide
additional opportunity for the public to comment on this SNPRM.

Proposed Requirements of This SNPRM

This proposed AD would retain none of the requirements of AD 2014-
25-04. This proposed AD would require revising the airworthiness
limitation section of the existing AMM or instructions for continued
airworthiness to incorporate new airworthiness limitations. The revised
limitations include an eddy current inspection of the fuselage wing
fittings and wing-to-fuselage fittings. This proposed AD would also
require, within 50 hours time-in-service (TIS) for certain bushes,
performing an eddy current inspection of the fuselage wing fittings and
wing-to-fuselage fittings and replacing the bush on the fuselage wing
fittings using grease. Lastly, this proposed AD would require
performing the eddy current inspection of the fuselage wing fittings
and wing-to-fuselage fittings first within 1,100 hours TIS or 12 months
(whichever occurs first), and thereafter at the intervals specified in
the revised limitations.

This proposed AD would require revisions to the airworthiness
limitations section (ALS) of an operator's maintenance documents to
include new inspections. Compliance with the airworthiness limitations
section is required by 14 CFR 91.403(c).

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

The FAA estimates the following costs to do the inspections and
installation that would be required if an earlier version of the
service information has been accomplished. The agency has no way of
determining the number of aircraft that might need these inspections
and installation:

On-Condition Costs

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) Will not affect intrastate aviation in Alaska, 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.

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:

a. Removing Airworthiness Directive (AD) 2014-25-04, Amendment 39-18045
(79 FR 73803, December 12, 2014); and

b. Adding the following new AD: