DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0786; Project Identifier MCAI-2021-00429-A]
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 supersede Airworthiness Directive (AD)
2012-06-16, which applies to all Pilatus Aircraft Ltd. (Pilatus) 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. AD 2012-06-16 requires installing a new
rudder and elevator locking screw and modifying the installation of the
rudder and elevator hinge bolt. Since the FAA issued AD 2012-06-16, the
European Union Aviation Safety Agency (EASA) superseded its mandatory
continuing airworthiness information (MCAI) to correct an unsafe
condition on these products. This proposed AD would not retain any
actions required by AD 2012-06-16 and would require inspecting and
modifying the rudder, elevator, and right-hand (RH) aileron hinge bolt
installations. 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 November 1,
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
Aircraft Ltd., Customer Support General Aviation, CH-6371 Stans,
Switzerland; phone: +41 848 24 7 365; email: techsupport.ch@pilatus-
aircraft.com; website: https://www.pilatus-aircraft.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-2021-0786; 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, the MCAI,
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 proposed AD. Send your comments to an address
listed under the ADDRESSES section. Include "Docket No. FAA-2021-0786;
Project Identifier MCAI-2021-00429-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 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 AD. 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 AD 2012-06-16, Amendment 39-16997 (77 FR 19061,
March 30, 2012) (AD 2012-06-16) for Pilatus 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. AD 2012-06-16 was prompted by MCAI originated by EASA,
which is the Technical Agent for the Member States of the European
Union. EASA issued EASA AD 2011-0230, dated December 9, 2011, to
identify and correct an unsafe condition identified as loose elevator
and rudder hinge bolts caused by incorrect torqueing and locking of the
bolts.

AD 2012-06-16 requires installing a new elevator and rudder locking
screw and modifying the installation of the elevator and rudder hinge
bolt. The FAA issued AD 2012-06-16 to prevent in-flight failure of the
elevator or rudder attachment, which could result in loss of control of
the airplane.

Actions Since AD 2012-06-16 Was Issued

Since the FAA issued AD 2012-06-16, EASA superseded EASA AD 2011-
0230, dated December 9, 2011, and issued EASA AD 2021-0098, dated April
9, 2021 (referred to after this as "the MCAI"). The MCAI states:

Occurrences were reported where, on certain PC-6 aeroplanes, the
elevator or the rudders was lost or partially detached during
flight. All the occurrences happened on PC-6 aeroplanes in CONFIG 1.

This condition, if not corrected, could lead to in-flight
failure of the elevator or rudder attachment, possibly resulting in
reduced control of the aeroplane.

To address this potential unsafe condition, Pilatus issued SB
55-001 (original issue and Revision 1) to provide rework
instructions for the elevator and rudder hinge bolt locking.
Consequently, EASA published AD 2011-0230 to require this rework.
Subsequently, Pilatus issued recommended SB 55-003 (later revised)
to provide instructions to modify the hinge bolt installation of the
elevator and rudder. This [service bulletin] SB, being recommended
only, had no impact on the existing EASA AD.

Since that [EASA] AD and the recommended Pilatus SB 55-003 were
published, the latest risk assessment determined that the
modification of the hinge bolt installation of the elevator, rudder
and right-hand (RH) aileron installation must be required to reach
an acceptable level of safety for the affected aeroplanes.
Consequently, Pilatus issued the SB, as defined in this [EASA] AD,
to provide instructions to modify the affected aeroplanes into
CONFIG 2 standard.

For the reasons described above, this [EASA] AD supersedes EASA
AD 2011-0230 and requires, for certain aeroplanes, a one-time
inspection of the elevator and rudder installation, followed by
repetitive inspections of the elevator and rudder, and, depending on
findings, accomplishment of applicable corrective action(s). This
[EASA] AD also requires modification of the elevator, rudder and RH
aileron hinge bolt installations into CONFIG 2, which is the
terminating action for the repetitive inspections required by this
[EASA] AD. Finally, this [EASA] AD prohibits (re)installation of
affected parts.

You may examine the MCAI in the AD docket at https://www.regulations.gov
by searching for and locating Docket No. FAA-2021-0786.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Pilatus PC-6 Service Bulletin (SB) No. 55-005,
dated February 25, 2021 (Pilatus SB 55-005). The service information
specifies procedures for repetitively inspecting the hinge bolt
installations and taking any necessary corrective actions until the
hinge bolt is modified. Modifying the hinge bolt installation in
accordance with Pilatus SB 55-005 makes the airplane a CONFIG 2 design.
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.

Other Related Service Information

Pilatus also issued Pilatus PC-6 SB No. 55-003, dated November 29,
2013; Pilatus PC-6 SB No. 55-003, Revision 1, dated December 9, 2014;
Pilatus PC-6 SB No. 55-003, Revision 2, dated January 19, 2017; and
Pilatus PC-6 SB No. 55-003, Revision 3, dated November 6, 2017. This
service information specifies procedures for modifying the hinge bolt
installations, which makes the airplane a CONFIG 2 design. This service
information was superseded by Pilatus SB 55-005.

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 this State of Design Authority,
it has notified the FAA of the unsafe condition described in the MCAI
and service information referenced above. 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.

Proposed AD Requirements in This NPRM

This proposed AD would require accomplishing the actions specified
in the service information described previously. This proposed AD would
not retain any actions of AD 2012-06-06.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 50 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 any necessary
corrective actions that would be required based on the results of the
proposed inspection. The FAA has no way of determining the number of
airplanes that might need these actions:

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 has 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 that the 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:

a. Removing Airworthiness Directive 2012-06-16, Amendment 39-16997 (77
FR 19061, March 30, 2012); and

b. Adding the following new airworthiness directive: