[Federal Register: October 18, 2005 (Volume 70, Number 200)]
[Rules and Regulations]
[Page 60422-60424]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr18oc05-5]
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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 john.mcconnell@faa.gov.
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