[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]


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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.

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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