[Federal Register Volume 89, Number 159 (Friday, August 16, 2024)]
[Rules and Regulations]
[Pages 66543-66545]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-18425]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2024-1626; Special Conditions No. 25-867-SC]
Special Conditions: Textron Aviation Inc. (Textron) Model 560XL
Airplane; Hydrophobic Windshield Coatings
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions; request for comments.
-----------------------------------------------------------------------
SUMMARY: These special conditions are issued for the Textron Model
560XL airplane. This airplane will have a novel or unusual design
feature when compared to the state of technology envisioned in the
airworthiness standards for transport-category airplanes. This design
feature is hydrophobic windshield coatings to maintain a clear view.
The applicable airworthiness regulations do not contain adequate or
appropriate safety standards for this design feature. These special
conditions contain the additional safety standards that the
Administrator considers necessary to establish a level of safety
equivalent to that established by the existing airworthiness standards.
DATES: This action is effective on Textron on August 16, 2024. Send
comments on or before September 30, 2024.
ADDRESSES: Send comments identified by Docket No. FAA-2024-1626 using
any of the following methods:
Federal eRegulations Portal: Go to www.regulations.gov and
follow the online instructions for sending your comments
electronically.
Mail: Send comments to Docket Operations, M-30, U.S.
Department of Transportation (DOT), 1200 New Jersey Avenue SE, Room
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
Hand Delivery or Courier: Take comments to Docket
Operations in Room W12-140 of the West Building Ground Floor at 1200
New Jersey Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday
through Friday, except Federal holidays.
Fax: Fax comments to Docket Operations at 202-493-2251.
Docket: Background documents or comments received may be read at
www.regulations.gov at any time. Follow the online instructions for
accessing the docket or go to Docket Operations in Room W12-140 of the
West Building Ground Floor at 1200 New Jersey Avenue SE, Washington,
DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal
holidays.
FOR FURTHER INFORMATION CONTACT: Eric Brown, Flight Test and Human
Factors, AIR-621A, Technical Policy Branch, Policy and Standards
Division, Aircraft Certification Service, Federal Aviation
Administration, 2200 S 216th Street, Des Moines, Washington 98198,
telephone and (206) 231-3563; email [email protected].
SUPPLEMENTARY INFORMATION: The substance of these special conditions
has been published in the Federal Register for public comment in
several prior instances with no substantive comments received.
Therefore, the FAA finds, pursuant to 14 CFR 11.38(b), that new
comments are unlikely, and notice and comment prior to this publication
are unnecessary.
Privacy
Except for Confidential Business Information (CBI) as described in
the following paragraph, and other information as described in title
14, Code of Federal Regulations (14 CFR) 11.35, the FAA will post all
comments received without change to www.regulations.gov, including any
personal information you provide. The
[[Page 66544]]
FAA will also post a report summarizing each substantive verbal contact
received about these special conditions.
Confidential Business Information
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
these special conditions contain commercial or financial information
that is customarily treated as private, that you actually treat as
private, and that is relevant or responsive to these special
conditions, 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 the indicated comments will not be
placed in the public docket of these proposed special conditions. Send
submissions containing CBI to the individual listed in the For Further
Information Contact section above. Comments the FAA receives, which are
not specifically designated as CBI, will be placed in the public docket
for these proposed special conditions.
Comments Invited
The FAA invites interested people to take part in this rulemaking
by sending written comments, data, or views. The most helpful comments
reference a specific portion of the special conditions, explain the
reason for any recommended change, and include supporting data.
The FAA will consider all comments received by the closing date for
comments. The FAA may change these special conditions based on the
comments received.
Background
On June 30, 2021, Textron applied for a change to Type Certificate
No. A22CE for hydrophobic coatings in lieu of windshield wipers on the
Model 560XL. The Textron Model 560XL airplane is a derivative of the
Model 560XLS+ and is currently approved under Type Certificate No.
A22CE. The Model 560XL is a twin-engine business jet, with a maximum
seating capacity for 12 passengers, and a maximum take-off weight of
20,330 pounds.
Type Certification Basis
Under the provisions of title 14, Code of Federal Regulations (14
CFR) 21.101, Textron must show that the Textron Aviation Inc. Model
560XL airplane, as changed, continues to meet the applicable provisions
of the regulations listed in Type Certificate No. A22CE or the
applicable regulations in effect on the date of application for the
change, except for earlier amendments as agreed upon by the FAA.
If the Administrator finds that the applicable airworthiness
regulations (e.g., 14 CFR part 25) do not contain adequate or
appropriate safety standards for the Textron Model 560XL airplane
because of a novel or unusual design feature, special conditions are
prescribed under the provisions of Sec. 21.16.
Special conditions are initially applicable to the model for which
they are issued. Should the type certificate for that model be amended
later to include any other model that incorporates the same novel or
unusual design feature, or should any other model already included on
the same type certificate be modified to incorporate the same novel or
unusual design feature, these special conditions would also apply to
the other model under Sec. 21.101.
In addition to the applicable airworthiness regulations and special
conditions, the Textron Model 560XL airplane must comply with the
exhaust-emission requirements of 14 CFR part 34, and the noise-
certification requirements of 14 CFR part 36.
The FAA issues special conditions, as defined in 14 CFR 11.19, in
accordance with Sec. 11.38, and they become part of the type
certification basis under Sec. 21.101.
Novel or Unusual Design Features
The modified Textron Model 560XL series airplane will incorporate
the following novel or unusual design feature:
Hydrophobic windshield coatings to maintain a clear view. The
airplane flightdeck design incorporates hydrophobic windshield coating
that, during precipitation, provides an adequate outside view from the
pilot compartment. Sole reliance on such coating, without windshield
wipers, constitutes a novel or unusual design feature for which the
applicable airworthiness regulations do not contain adequate or
appropriate safety standards. Therefore, special conditions are
required to provide a level of safety equivalent to that established by
the regulations.
Discussion
Title 14 CFR 25.773(b)(1) requires a means to maintain a clear
portion of the windshield for both pilots to have a sufficiently
extensive view along the flight path during precipitation conditions.
The regulations require this means to maintain such an area during
precipitation in heavy rain at speeds up to 1.5 VSR1.
Effective December 26, 2002, amendment 25-108 changed the speed for
effectiveness of the means to maintain an area of clear vision from up
to 1.6 VS1 to 1.5 VSR1 to accommodate the
redefinition of the reference stall speed from the minimum speed in the
stall, VS1, to greater than or equal to the 1g stall speed,
VSR1. As noted in the preamble to the final rule for that
amendment, the reduced factor of 1.5 on VSR1 is to maintain
approximately the same speed as the 1.6 factor on VS1.
Textron was granted an Equivalent Level of Safety (ELOS) to Sec.
25.773(b)(1)(i) amendment 25-136 to use 1.6 Vs1 instead of
1.5 VSR1 as documented in ELOS Memorandum No. TXTAV-18571-
SM-03, dated December 6, 2023.
The requirement that the means to maintain a clear area of forward
vision must function at high speeds and high precipitation rates is
based on the use of windshield wipers as the means to maintain an
adequate area of clear vision in precipitation conditions. The
effectiveness of windshield wipers to maintain an area of clear vision
normally degrades as airspeed and precipitation rates increase. It is
assumed that because high speeds and high precipitation rates represent
limiting conditions for windshield wipers, they will also be effective
at lower speeds and precipitation levels. Accordingly, Sec.
25.773(b)(1)(i) does not require maintenance of a clear area of forward
vision at lower speeds or lower precipitation rates.
A forced airflow blown directly over the windshield has also been
used to maintain an area of clear vision in precipitation. The limiting
conditions for this technology are comparable to those for windshield
wipers. Accordingly, introduction of this technology did not present a
need for special conditions to maintain the level of safety embodied in
the existing regulations.
Hydrophobic windshield coatings may depend to some degree on
airflow to maintain a clear vision area. The heavy rain and high-speed
conditions specified in the current rule do not necessarily represent
the limiting condition for this new technology. For example, airflow
over the windshield, which may be necessary to remove moisture from the
windshield, may not be adequate to maintain a sufficiently clear area
of the windshield in low-
[[Page 66545]]
speed flight or during surface operations. Alternatively, airflow over
the windshield may be disturbed during such critical times as the
approach to land, where the airplane is at a higher-than-normal pitch
attitude. In these cases, areas of airflow disturbance or separation on
the windshield could cause failure to maintain a clear vision area on
the windshield.
In addition to potentially depending on airflow to function
effectively, hydrophobic coatings may also be dependent on water-
droplet size for effective precipitation removal. For example,
precipitation in the form of a light mist may not be sufficient for the
coating's properties to result in maintaining a clear area of vision.
The current regulations identify speed and precipitation rate
requirements that represent limiting conditions for windshield wipers
and blowers, but not for hydrophobic coatings. Likewise, it is
necessary to issue special conditions to maintain the level of safety
represented by the current regulations.
These special conditions provide an appropriate safety standard for
the hydrophobic-coating technology as the means to maintain a clear
area of vision by requiring coating to be effective at low speeds and
low precipitation rates, as well as at the higher speeds and
precipitation rates identified in the current regulation.
These special conditions contain the additional safety standards
that the Administrator considers necessary to establish a level of
safety equivalent to that established by the existing airworthiness
standards.
Applicability
As discussed above, these special conditions are applicable to the
Textron Model 560XL airplane. Should Textron apply at a later date for
a change to the type certificate to include another model incorporating
the same novel or unusual design feature, these special conditions
would apply to that model as well.
Conclusion
This action affects only a certain novel or unusual design feature
on the Textron Model 560XL airplane. It is not a rule of general
applicability.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
Authority Citation
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701, 44702, and
44704.
The Special Conditions
Accordingly, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued as part of
the type certification basis for Textron Model 560XL.
The airplane must have a means to maintain a clear portion of the
windshield, during precipitation conditions, enough for both pilots to
have a sufficiently extensive view along the ground or flight path in
normal taxi and flight altitudes of the airplane. This means must be
designed to function, without continuous attention on the part of the
crew, in conditions from light misting precipitation to heavy rain, at
speeds from fully stopped in still air, to 1.6 VS with lift
and drag devices retracted.
Issued in Kansas City, Missouri, on August 8, 2024.
Patrick R. Mullen,
Manager, Technical Policy Branch, Policy and Standards Division,
Aircraft Certification Service.
[FR Doc. 2024-18425 Filed 8-15-24; 8:45 am]
BILLING CODE 4910-13-P