DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-0470; Project Identifier AD-2023-00694-A;
Amendment 39-22800; AD 2024-15-09]
RIN 2120-AA64

Airworthiness Directives; Textron Aviation Inc. (Type Certificate
Previously Held by Cessna Aircraft Company) Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
Textron Aviation Inc. (Textron) (type certificate previously held by
Cessna Aircraft Company) Model 525, 525A, and 525B airplanes with
Tamarack active technology load alleviation system (ATLAS) winglets
installed per Supplemental Type Certificate (STC) No. SA03842NY. This
AD was prompted by a report of the potential for a failure of the ATLAS
system in which a loss of load alleviation would be un-annunciated.
This AD requires installing placards on the left-hand inboard edge of
the Tamarack active camber surface (TACS) and revising the existing
airplane flight manual (AFM) for your airplane. The FAA is issuing this
AD to address the unsafe condition on these products.

DATES: This AD is effective October 22, 2024.

The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of October 22, 2024.

ADDRESSES: AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2024-0470; 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 final rule, any comments received, and other
information. The address for Docket Operations is U.S. Department of
Transportation, Docket Operations, M-30, West Building Ground Floor,
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.

Material Incorporated by Reference:

For Tamarack material identified in this AD, contact
Tamarack Aerospace Group, Inc., 2021 Industrial Drive, Sandpoint, ID
83864; phone: (208) 597-4568; website: tamarackaero.com/customer-support.

You may view this material 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 (817) 222-5110. It is also available at regulations.gov under
Docket No. FAA-2024-0470.

FOR FURTHER INFORMATION CONTACT: Anthony Caldejon, Aviation Safety
Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone:
(206) 231-3534; email: anthony.v.caldejon@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to Textron (type
certificate previously held by Cessna Aircraft Company) Model 525,
525A, and 525B airplanes with Tamarack ATLAS winglets installed per STC
No. SA03842NY. The NPRM published in the Federal Register on March 22,
2024 (89 FR 20354). The NPRM was prompted by a report that while
accomplishing a reliability improvement program, Tamarack discovered
the potential for a failure of the ATLAS system in which a loss of load
alleviation would be un-annunciated. The manufacturer's investigation
revealed that failure of either of one of a pair of opto-isolators
within the ATLAS Control Unit (ACU) can prevent an enable signal from
being sent to the TACS Control Units (TCUs).

The ATLAS system is installed on Textron Model 525, 525A, and 525B
airplanes under STC No. SA03842NY and lessens the increased wing loads
associated with the installation of winglets. The ATLAS is designed to
detect flight conditions and modify airflow at the wing tip
accordingly. The ATLAS will draw power constantly to operate the logic
circuit and provide power to the actuators to maintain TACS position.

The TCUs include the linear electric actuators and motor
controllers that move the TACS. Since the enable signals are not
monitored after the opto-isolators, the ACU cannot detect whether the
generated signal is reaching the TCUs. The TCUs rely on the enable
signal to determine whether to respond to commands from the ACU. If one
of the opto-isolators fails, the ACU would not be able to detect that
the TCUs were not enabled and the TCUs would not respond to commands
from the ACU. Thus, the system would be operating in a mode of un-
annunciated loss of load alleviation. The flight crew would be unaware
of a malfunction of the load alleviation function of ATLAS and could
fly the airplane into conditions that exceed the limit load. In
addition, fatigue concerns could result in cracking of the airplane's
primary structure. If not addressed, this condition could result in
loss of continued safe flight and landing of the airplane.

In the NPRM, the FAA proposed to require installing placards on the
left-hand inboard edge of the TACS to enhance visibility of TACS
movement during night operations and revising the existing AFM for your
airplane to include instructions for pre-flight checks of the ATLAS
system before taxi. The FAA is issuing this AD to address the unsafe
condition on these products.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from three commenters. Two of the
commenters were individuals who supported the NPRM. The third commenter
was Tamarack. The following presents the comments received on the NPRM
from Tamarack and the FAA's response to each comment.

Request To Clarify What Prompted the NPRM

Tamarack requested that the FAA correct the SUMMARY and paragraph
(e), "Unsafe Condition," which state that the NPRM was prompted by a
report of an un-annunciated failure of the ATLAS system. Tamarack
commented that this statement is not accurate because even though
Tamarack reported the design deficiency to the FAA under 14 CFR 21.3,
"Reporting of failures, malfunctions, and defects," there had not
been any actual failures of the ATLAS system in the fleet. Tamarack
stated that the "Background" section of the NPRM more accurately
explains that, while accomplishing a reliability improvement program,
Tamarack discovered the potential for a failure of the ATLAS system in
which a loss of load alleviation would be un-annunciated.

The FAA agrees to correct the language identified by the commenter
and has revised the SUMMARY and paragraph (e) of this AD accordingly.

Request To Revise "Proposed AD Requirements in This NPRM" Section

Tamarack requested that the FAA revise the "Proposed AD
Requirements in This NPRM" section of the NPRM to specify who can
accomplish the required actions. Tamarack stated that it is unclear
whether a pilot can install the placards on the left-hand inboard edge of the TACS or whether the
placards must be installed by a certificated airframe and powerplant
(A&P) mechanic.

Paragraph (g) of this AD only allows a pilot to do the revision to
the AFM required by paragraph (g)(2) of this AD and does not allow a
pilot to do the installation of placards required by paragraph (g)(1)
of this AD. An FAA-certificated A&P mechanic or repair station must
install the placards on the left-hand inboard edge of the TACS. The FAA
has not revised the "Proposed AD Requirements in This NPRM" section
as requested by the commenter because that section of the NPRM is not
carried over into this final rule.

Request To Revise "FAA's Determination" Section of the NPRM

Tamarack requested that the FAA revise the "FAA's Determination"
section of the NPRM, which states that the FAA has determined that the
unsafe condition is likely to exist or develop on other products of the
same type design. Tamarack stated that the probability of the unsafe
condition is "remote" and not "likely" and therefore using
"likely" misrepresents the probability of the identified unsafe
condition occurring in the fleet.

The FAA disagrees. The "FAA's Determination" section of the NPRM
correlates to the FAA's finding under 14 CFR 39.5, which states the
conditions that must be present when the FAA issues an AD. If an unsafe
condition only exists on one product and is not likely to exist or
develop on other products of the same type design, or if there are no
other existing products of the same type design, the FAA will
accomplish corrective action through means other than an AD. The FAA's
finding under 14 CFR 39.5 is unrelated to the probability of the
failure condition described by the commenter. The FAA did not revise
this final rule regarding this issue.

Conclusion

The FAA reviewed the relevant data, considered any comments
received, and determined that air safety requires adopting this AD as
proposed. Accordingly, the FAA is issuing this AD to address the unsafe
condition on these products. Except for the change described
previously, this AD is adopted as proposed in the NPRM.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed Tamarack Aerospace Atlas Service Bulletin SBATLAS-
57-06, Issue A, dated April 19, 2023. This material specifies
procedures for installing placards on the left-hand inboard edge of the
TACS to enhance visibility of TACS movement during night operations.

The FAA also reviewed the following AFM supplements, which contain,
among other items, instructions for pre-flight checks of the ATLAS
system before taxi. These documents are distinct because they apply to
different airplane models.

Tamarack Aerospace Cessna Citation Model 525, 525-0001
thru -0359, AFM Supplement TAG-1101-0099 CA/DD/M023, Tamarack Active
Technology Load Alleviation System (Atlas) Winglets, Issue D, dated
September 20, 2023.

Tamarack Aerospace Cessna Citation Model 525, 525-0360
through -0599, AFM Supplement TAG-1101-1099 CA/DD/M037, Tamarack Active
Technology Load Alleviation System (Atlas) Winglets, Issue D, dated
September 20, 2023.

Tamarack Aerospace Cessna Citation Model 525, 525-0600
through -0684 and -0686 through -0701, AFM Supplement TAG-1101-P099 CA/
DD/M038, Tamarack Active Technology Load Alleviation System (Atlas)
Winglets, Issue D, dated September 20, 2023.

Tamarack Aerospace Cessna Citation Model 525, 525-0685 and
-0800 and on, AFM Supplement TAG-1101-M099 CA/DD/M088, Tamarack Active
Technology Load Alleviation System (Atlas) Winglets, Issue D, September
20, 2023.

Tamarack Aerospace Cessna Citation Model 525A, 525A-0001
thru -0299, AFM Supplement TAG-1102-0099 CAS/AFM0003, Tamarack Active
Technology Load Alleviation System (Atlas) Winglets, Issue C, September
20, 2023.

Tamarack Aerospace Cessna Citation Model 525A, 525A-0300
and on, AFM Supplement TAG-1102-P099 CAS/AFM0004, Tamarack Active
Technology Load Alleviation System (Atlas) Winglets, Issue C, September
20, 2023.

Tamarack Aerospace Cessna Citation Jet Model 525B, 525B-
0001 thru 525B-0056 and 525B-0058 thru 525B-0450, AFM Supplement TAG-
1103-0099 CAS/AFM0001, Tamarack Active Technology Load Alleviation
System (Atlas) Winglets, Issue C, September 20, 2023.

Tamarack Aerospace Cessna Citation Jet Model 525B, 525B-
0057 and 525B-0451 and ON, AFM Supplement TAG-1103-P099 CAS/AFM0002,
Tamarack Active Technology Load Alleviation System (Atlas) Winglets,
Issue D, September 20, 2023.

This material 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.

Costs of Compliance

The FAA estimates that this AD affects 148 airplanes of U.S. registry.

The FAA estimates the following costs to comply with this 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

This AD will not have federalism implications under Executive Order
13132. This AD will 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 this AD:

(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 Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 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: