DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-1990; Project Identifier AD-2023-00734-A]
RIN 2120-AA64

Airworthiness Directives; Various 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)
that applied to various airplanes modified with a certain configuration
of the Garmin GFC 500 Autopilot System installed per Supplemental Type
Certificate (STC) No. SA01866WI. This action revises the NPRM by
removing airplane models from and adding airplane models to the
applicability. The FAA is proposing this airworthiness directive to
address the unsafe condition on these products. Since this action would
expand the applicability for the required action as proposed in the
NPRM, the agency is requesting comments on this SNPRM.

DATES: The FAA must receive comments on this SNPRM by June 3, 2024.

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 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.
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2023-1990; 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 SNPRM, any comments received, and other
information. The street address for Docket Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Christopher Withers, Aviation Safety
Engineer, FAA, 1801 S Airport Road, Wichita, KS 67209; phone: (316)
946-4190; email: christopher.d.withers@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 the ADDRESSES section. Include ``Docket No. FAA-2023-1990;
Project Identifier AD-2023-00734-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 again revise 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
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 Christopher Withers, Aviation Safety Engineer, FAA, 1801 S
Airport Road, Wichita, KS 67209. 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 by adding an AD that
would apply to various airplanes modified with a certain configuration
of the Garmin GFC 500 Autopilot System installed per STC No. SA01866WI.
The NPRM published in the Federal Register on October 10, 2023 (88 FR
69891). The NPRM was prompted by a report of an un-commanded automatic
pitch trim runaway when the autopilot was first engaged. In the NPRM,
the FAA proposed to require updating the applicable Garmin GFC 500
Autopilot System software for your airplane and prohibit installing
earlier versions of that software.

Actions Since the NPRM Was Issued

Based on the comments the FAA received on the NPRM, the FAA is
proposing revising the applicability by removing and adding airplane
models, revising paragraph (e) of the proposed AD to clarify that
certain hardware failures affected the primary pitch servo, and adding
Note 1 to paragraph (g) of the proposed AD.

Comments

The FAA received comments from several individuals and the National
Transportation Safety Board (NTSB), who supported the NPRM without
change.
The FAA also received three comments from Garmin. The following
presents the comments received on the NPRM and the FAA's response to
each comment.

Request To Correct Language in Paragraph (e) of the Proposed AD

Garmin stated that paragraph (e) of the proposed AD incorrectly
states that hardware faults can occur in the pitch trim servo. Garmin
explained that hardware faults occur in the pitch servo,
not the pitch trim servo. Garmin requested a correction to state that
hardware faults occur in the pitch servo.
The FAA agrees with the commenter. The FAA has corrected paragraph
(e) of the proposed AD to change the wording from ``pitch trim servo''
to ``primary pitch servo.''

Request To Reference Service Information

Garmin also stated that paragraph (g) of the proposed AD should
reference Garmin Mandatory STC Service Bulletin (SB) 22123, Rev A,
dated January 3, 2023, or later revision, because it would help
operators find the easiest path to compliance.
The FAA partially agrees. The FAA agrees that referencing the SB
will help operators find a path to compliance but disagrees that
operators should be required to use the SB to update the software. The
SB requires performing multiple actions, whereas the specified action
in this proposed AD is to only update the software version. The FAA has
added Note 1 to paragraph (g) of this proposed AD to inform operators
that the software update can be done using Garmin Mandatory STC Service
Bulletin 22123, Rev A, dated January 3, 2023.

Request To Add Additional Airplane Models

Garmin further stated that the proposed AD would affect more
airplane models than what are included in paragraph (c) of the proposed
AD. The FAA infers that Garmin requested the applicability of the NPRM
be revised to include additional airplane models.
The FAA agrees and has updated paragraph (c) of this proposed AD to
include additional affected airplane models.

Additional Change Made to the Applicability

Since the NPRM published, the FAA determined the need to remove
Commander Aircraft Corporation Model 112 airplanes and Textron Aviation
Inc. Model 177 airplanes from paragraph (c), Applicability, of this
proposed AD. Paragraph (c) of the proposed AD specifies that the
affected airplanes are those having a Garmin GFC 500 Autopilot System
that includes an optional GSA 28 pitch trim servo installed per STC No.
SA01866WI using Master Drawing List (MDL) 005-01264-00, Revisions 1
through 76. The software change to eliminate the unsafe condition
identified in this proposed AD was included in MDL revision 77 so
airplanes incorporating this STC using MDL revision 77 and higher do
not have the software that exhibits the unsafe condition. When
installing STC No. SA01866WI, operators of Model 112 airplanes are
using MDL revision 78 and operators of Model 177 airplanes are using
MDL revision 83, therefore they should not be included in the
applicability.
The FAA also determind the need to remove Textron Aviation Inc.
Model 182 airplanes from paragraph (c) of this proposed AD. Although
Model 182 airplanes are using MDL revision 61, they are not affected by
the identified unsafe condition because the mechanical characteristics
prohibit the installation of a pitch trim servo.
The FAA further determined the need to remove Mooney International
Corporation Model M20 airplanes and Textron Aviation Inc. Model 172,
206, and 210 airplanes from paragraph (c) of this proposed AD. These
airplane models are not listed in the FAA Approved Model List (AML),
amended September 8, 2023, for STC No. SA01866WI.

FAA's Determination

The FAA is proposing this AD after determining the unsafe condition
described previously is likely to exist or develop in 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 AD Requirements in This SNPRM

This proposed AD would require updating the applicable Garmin GFC
500 Autopilot System software for your airplane and would prohibit
installing earlier versions of that software.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 5,900 airplanes of U.S. registry.
The FAA estimates the following costs to comply with this proposed
AD:

Estimated 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) 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: