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Proposed Rule

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

Document Details

Information about this document as published in the Federal Register.

Published Document

This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

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AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed special conditions.

SUMMARY:

This notice proposes special conditions 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 proposed 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:

Comments must be received on or before August 15, 2005.

ADDRESSES:

Comments on this proposal may be mailed in duplicate to: Federal Aviation Administration, Transport Airplane Directorate, Attn: Rules Docket (ANM-113), Docket No. NM310, 1601 Lind Avenue SW., Renton, Washington 98055-4056; or delivered in duplicate to the Transport Airplane Directorate at the above address. Comments must be marked: Docket No. NM310. Comments may be inspected in the Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.

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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.

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SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites interested persons to participate in this rulemaking by submitting 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. We ask that you send us two copies of written comments.

We will file in the docket all comments we receive, as well as a report summarizing each substantive public contact with FAA personnel concerning these special conditions. The docket is available for public inspection before and after the comment closing date. If you wish to review the docket in person, go to the address in the ADDRESSES section of this preamble between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

We will consider all comments we receive on or before the closing date for comments. We will consider comments filed late if it is possible to do so without incurring expense or delay. We may change these special conditions in light of the comments we receive.

If you want the FAA to acknowledge receipt of your comments on this proposal, include with your comments a pre-addressed, stamped postcard on which the docket number appears. We will stamp the date on the postcard and mail it back to you.

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 Start Printed Page 37716compartment 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 provides 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 Amendments 25-1 through 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 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 § 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 § 21.93(b) or 14 CFR part 36, as amended by Amendments 36-1 thru 36-24, and (2) either the “No Emission Change” provisions of § 21.93(c) or 14 CFR part 34, as amended by Amendments 34-1 through 34-3.

Special conditions, as defined in 14 CFR 11.19, are issued in accordance with § 11.38 and become part of the type certification basis in accordance with § 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 § 21.101.

Novel or Unusual Design Features

The GALP Mode 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 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 the crew: (i) In heavy rain at speeds up to 1.6 VS1, flaps retracted.” Effective December 26, 1990, Amendment 25-108 changed the criterion for effectiveness of the means to maintain an area of clear vision from 1.6 VS1 to 1.5 VSR1 to accommodate the redefinition of the reference stall speed as the 1-g stall speed. As noted in the preamble to the final rule for that amendment, the 7 percent decrease in the speed value offsets a corresponding increase in the reference stall speed associated with the use of VSR1 rather than 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 airflow 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, § 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 air stream blown 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 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 surface operations. Alternately, 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 Start Printed Page 37717means 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 § 25.773(b)(1) at Amendment 25-108.

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 that model as well.

Conclusion

This action affects only certain novel or unusual design features on one model of airplanes. It is not a rule of general applicability.

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List of Subjects in 14 CFR Part 25

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The authority citation for these special conditions is as follows:

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Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

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The Proposed Special Conditions

Accordingly, the Federal Aviation Administration (FAA) proposes the following special conditions as part of the type certification basis for Gulfstream Aerospace Limited Partnership (GALP) Model G150 airplane.

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 flight path in normal 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.

Start Signature

Issued in Renton, Washington, on June 21, 2005.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 05-12883 Filed 6-29-05; 8:45 am]

BILLING CODE 4910-13-M