[Federal Register Volume 87, Number 6 (Monday, January 10, 2022)]
[Rules and Regulations]
[Pages 1066-1068]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-00129]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2014-1075; Special Conditions No. 25-599A-SC]


Special Conditions: Dassault Aviation Model Falcon 6X Airplane; 
Hydrophobic Windshield Coatings in Lieu of Windshield Wipers

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions, amendment.

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SUMMARY: These amended special conditions are issued for the Dassault 
Model Falcon 6X 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 in lieu of windshield 
wipers. 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 Dassault on January 10, 2022.

FOR FURTHER INFORMATION CONTACT: Paul Pellicano, AIR-625, Performance 
and Environment Section, Technical Innovation Policy Branch, Policy and 
Innovation Division, Federal Aviation Administration, 1701 Columbia 
Avenue, College Park, GA 30337; telephone and fax 404-474-5558, email 
[email protected].

SUPPLEMENTARY INFORMATION:

Background

    On July 1, 2012, Dassault Aviation applied for a type certificate 
for their new Model Falcon 5X airplane. Special conditions were issued 
for that design on September 15, 2015 (80 FR 55226). However, Dassault 
has decided not to release an airplane under the model designation 
Falcon 5X, instead choosing to change that model designation to Falcon 
6X.
    In February of 2018, due to engine supplier issues, Dassault 
extended the type certificate application date for their Model Falcon 
5X airplane under new Model Falcon 6X. This amendment to the original 
special conditions reflects the model-name change. This airplane is a 
twin-engine business jet with seating for 19 passengers and a maximum 
takeoff weight of 77,460 pounds. The Dassault Model Falcon 6X airplane 
design remains unchanged from the Model Falcon 5X in all material 
respects other than different engines.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulations (14 
CFR) 21.17, Dassault Aviation must show that the Model Falcon 6X 
airplane meets the applicable provisions of part 25, as amended by 
Amendments 25-1 through 25-146.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Dassault Model Falcon 6X 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

[[Page 1067]]

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, 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 Model Falcon 6X airplane must comply with the fuel-vent 
and 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.  21.17(a)(2).

Novel or Unusual Design Features

    The Dassault Model Falcon 6X airplane flight deck design 
incorporates a hydrophobic coating as a primary means to provide 
adequate windshield view in the presence of atmospheric precipitation. 
Reliance on such a coating, in lieu of wipers, constitutes a novel or 
unusual design feature for which the applicable airworthiness 
regulations do not contain adequate or appropriate safety standards.

Discussion

    Section 25.773(b)(1) requires a means to maintain a clear portion 
of the windshield for both pilots operating a transport-category 
airplane to have a sufficiently extensive view along the flight path 
during precipitation conditions. The regulations require this means to 
maintain such an area of clear vision during heavy-rain precipitation 
at airplane speeds up to 1.5 VSR1.
    This requirement has existed in principle since 1953 in part 4b of 
the ``Civil Air Regulations'' (CAR). Section 4b.351(b)(1) required that 
``Means shall be provided for maintaining a sufficient portion of the 
windshield clear so that both pilots are afforded a sufficiently 
extensive view along the flight path in all normal flight attitudes of 
the airplane. Such means shall be designed to function under the 
following conditions without continuous attention on the part of the 
crew: (i) In heavy rain at speeds up to 1.6 VS1, flaps 
retracted.''
    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.
    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 
requirement in 14 CFR 121.313(b) and 125.213(b) to provide ``. . . a 
windshield wiper or equivalent for each pilot station . . .'' has 
remained unchanged since at least 1953.
    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-vision 
area of the windshield in low-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 the 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.

Discussion of Comments

    The FAA issued Final special conditions, request for comment 
Special Conditions No. 25-599-SC for the Dassault Model Falcon 5X 
airplane, which was published in the Federal Register on September 15, 
2015 (80 FR 55226). No comments were received, and the special 
conditions are adopted as proposed, with amendments.

Applicability

    As discussed above, these special conditions are applicable to the 
Dassault Model Falcon 6X airplane. Should Dassault apply at a later 
date for a change to the type certificate to include another model 
incorporating the same novel or unusual design feature, the special 
conditions would apply to that model as well.

Conclusion

    This action affects only certain novel or unusual design features 
on the Dassault Model Falcon 6X airplane. It is not a rule of general 
applicability.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701, 44702, 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 Dassault Model Falcon 6X airplanes.

[[Page 1068]]

    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 attitudes of the airplane. This means must be 
designed to function, without continuous attention on the part of the 
flightcrew, in conditions from light misting precipitation to heavy 
rain, at speeds from fully stopped in still air, to 1.5 VSR1 
with lift and drag devices retracted.

    Issued in Kansas City, Missouri, on January 4, 2022.
Patrick R. Mullen,
Manager, Technical Innovation Policy Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2022-00129 Filed 1-7-22; 8:45 am]
BILLING CODE 4910-13-P


