[Federal Register Volume 70, Number 200 (Tuesday, October 18, 2005)]
[Rules and Regulations]
[Pages 60422-60424]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-20864]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM310; Special Conditions No. 25-306-SC]


Special Conditions: Gulfstream Aerospace Limited Partnership 
(GALP) Model G150 Airplane; Windshield Coating in Lieu of Wipers

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Gulfstream 
Aerospace Limited Partnership (GALP) Model G150 airplane. This airplane 
will have a novel or unusual design feature associated with use of a 
hydrophobic coating, rather than windshield wipers, as the means to 
maintain a clear portion of the windshield during precipitation 
conditions, as required by the airworthiness standards for transport 
category airplanes. 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.

EFFECTIVE DATE: November 17, 2005.

FOR FURTHER INFORMATION CONTACT: John McConnell, Airplane and Flight 
Crew Interface Branch, ANM-111, Transport Airplane Directorate, 
Aircraft Certification Service, 1601 Lind Avenue SW., Renton, 
Washington, 98055-4056; telephone (425) 227-1365; facsimile (425) 227-
1320, e-mail [email protected].

SUPPLEMENTARY INFORMATION:

Background

    On September 22, 2002, GALP applied for an amendment to Type 
Certificate Number A16NM to include the new GALP Model G150 airplane. 
The GALP Model G150, which is a derivative of the GALP Model G100 
currently approved under Type Certificate Number A16NM, is intended to 
be a nine passenger executive airplane with a maximum takeoff weight of 
26,000 pounds and a maximum operating altitude of 45,000 feet.
    The GALP Model G150 flightdeck design incorporates a hydrophobic 
coating to provide adequate pilot compartment view in the presence of 
precipitation. Sole reliance on such a 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 that provide the level of safety equivalent to that 
established by the regulations.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, GALP must show that the 
Model G150 meets the applicable provisions of the regulations 
incorporated by reference in Type Certificate Number A16NM or the 
applicable regulations in effect on the date of application for the 
change to the type certificate. The regulations incorporated by 
reference in the type certificate are commonly referred to as the 
``original type certification basis.'' The regulations incorporated by 
reference in Type Certificate Number A16NM are 14 CFR part 25, 
effective February 1, 1965, including Amendment 25-1 through Amendment 
25-107.
    In addition, if the regulations incorporated by reference do not 
provide adequate standards with respect to the change, the applicant 
must comply with certain regulations in effect on the date of 
application for the

[[Page 60423]]

change. GALP has elected to voluntarily comply with Amendment 25-108 
for the G150 type certification program.
    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 Model G150 because of a novel or 
unusual design feature, special conditions are prescribed under the 
provisions of Sec.  21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model G150 must comply with (1) either the ``No 
Acoustical Change'' provisions of Sec.  21.93(b) or 14 CFR part 36, as 
amended by Amendments 36-1 through 36-24, and (2) either the ``No 
Emission Change'' provisions of Sec.  21.93(c) or 14 CFR part 34, as 
amended by Amendment 34-1 through Amendment 34-3.
    Special conditions, as defined in 14 CFR 11.19, are issued in 
accordance with Sec.  11.38 and become part of the type certification 
basis in accordance with Sec.  21.101.
    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 or similar 
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, the special conditions would also 
apply to the other model under the provisions of Sec.  21.101.

Novel or Unusual Design Features

    The GALP Model G150 will incorporate the following novel or unusual 
design feature: Hydrophobic windshield coating as the sole means to 
maintain a clear portion of the windshield, during precipitation 
conditions, sufficient for both pilots to have a sufficiently extensive 
view along the flight path.

Discussion

    Section 25.773(b)(1) requires that both pilots of a transport 
category airplane be provided a means to maintain a sufficiently clear 
portion of the windshield during precipitation conditions, and that 
this clear portion of the windshield must have a sufficiently extensive 
view along the flight path. The regulations require this means to 
maintain such an area during precipitation in heavy rain at 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) of CAR 4b 
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 1-g 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 in 14 CFR 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 directly over the windshield to maintain a clear vision area. 
The heavy rain and high-speed conditions specified in the current rule 
do not necessarily represent the limiting conditions 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 speed 
flight or during ground 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.
    In summary, the current regulations identify speed and 
precipitation rate requirements that represent limiting conditions for 
windshield wipers and blowers, but not for hydrophobic coatings, so 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 it to be effective at low speeds and 
precipitation rates as well as the higher speeds and precipitation 
rates identified in the current regulation. These are the only new or 
changed requirements relative to those in Sec.  25.773(b)(1) at 
Amendment 25-108.

Discussion of Comments

    Notice of proposed special conditions No. 25-05-07 for the 
Gulfstream Aerospace Limited Partnership Model G150 airplane was 
published in the Federal Register on June 30, 2005 (70 FR 37715). Only 
one commenter responded to the notice.

Using Hydrophobic Coating Is Not Novel and Unusual

    The commenter, Gulfstream, states that the FAA defines hydrophobic 
coating as ``a novel and unusual design feature on one model of 
airplane.'' The commenter notes that the hydrophobic coating proposed 
for the Model G150 has actually accumulated a significant service 
history and has been certified on numerous transport airplanes.
    We infer that the commenter does not agree that the use of 
hydrophobic coating should be identified as ``a novel and unusual 
design feature.'' We do not

[[Page 60424]]

agree. We believe that the previous approvals for using hydrophobic 
coating should have included special conditions in the type 
certification basis. As is the case for the Model G150, the use of 
hydrophobic coatings in lieu of windshield wipers represents a novel 
design feature relative to the certification basis of each of those 
airplane types. While the satisfactory service history indicates that 
these particular designs would likely have met the requirements of the 
special conditions, the existing regulatory requirements would not by 
themselves have necessarily assured the intended level of safety for 
the use of hydrophobic coating for precipitation removal for these 
designs, or for other designs. Special conditions are necessary to 
address the use of hydrophobic coating instead of windshield wipers. No 
changes were made as a result of this comment.

Sufficient View

    The commenter recommends that the term ``sufficient view'' be 
changed to ``sufficient view depending on aircraft speed.'' The 
commenter states that the visibility requirements for taxi are 
different than the requirements for flight.
    We do not agree with the commenter's recommendation. The existing 
regulatory requirements in 14 CFR 25.773(b)(1), at Amendment 25-108, do 
not explicitly include this qualification. As with the existing 
requirements, the interpretation of ``sufficient view'' in these 
special conditions may be dependent on several factors other than 
airplane speed, such as phase of flight or ground operations. No 
changes were made as a result of this comment.

Changes to the Proposed Special Conditions

    The reference to ``the flight path in normal flight attitudes of 
the airplane'' has been changed to ``the ground or flight path in 
normal taxi and flight attitudes of the airplane.'' This change 
clarifies a possible ambiguity regarding the path of the airplane 
relative to the speeds necessary to maintain the clear vision area. 
While this additional language is absent from the requirement of Sec.  
25.773(b)(1), it is consistent with the intended level of safety. As 
noted in the Discussion section of the Notice of Proposed Special 
Conditions, the existing requirements are premised on the use of 
windshield wipers or other means for which slow speeds and minimal 
airflow are not limiting conditions for maintaining an area of clear 
vision. Hydrophobic coatings, however, are least effective at slow 
speeds and low airflow rates. To maintain the same level of safety as 
the existing regulations, the certification basis must address both 
ground and flight operations, as reflected by the speed and airflow 
range included in the proposed special conditions.
    We also changed the Discussion section to correct the effective 
date of Amendment 25-108 from December 26, 1990, to December 26, 2002. 
In addition, we made editorial changes to the Discussion section to 
clarify certain information regarding airspeed. Except as discussed 
above, the special conditions are adopted as proposed.

Applicability

    As discussed above, these special conditions are applicable to the 
Model G150. Should GALP apply at a later date for a change to the type 
certificate to include other type designs incorporating the same novel 
or unusual design feature, the special conditions would apply to those 
models as well under the provisions of Sec.  21.101.

Conclusion

    This action affects only certain novel or unusual design features 
on one model of 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(g), 40113, 44701, 44702, 44704.

The Special Conditions

0
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 Gulfstream Aerospace Limited 
Partnership (GALP) Model G150 airplanes.

Pilot Compartment View--Hydrophobic Coatings in Lieu of Windshield 
Wipers

    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 
crew, 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 Renton, Washington, on October 7, 2005.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 05-20864 Filed 10-17-05; 8:45 am]
BILLING CODE 4910-13-P