E7-200. Special Conditions: Dassault Aviation Model Falcon 7X Airplane, Windshield Coating in Lieu of Wipers

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final special conditions.

SUMMARY:

This special condition is issued for the Dassault Aviation Model Falcon 7X airplane. This airplane will have a novel or unusual design feature associated with use of a hydrophobic windshield 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. This special condition contains 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:

Effective Date: December 29, 2006.

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 98057-3356; telephone [phone]; facsimile [phone]; e-mail [e-mail].

SUPPLEMENTARY INFORMATION:

Background

On June 4, 2002, Dassault Aviation, 9 rond Point des Champs Elysées, 75008, Paris, France, applied for a type certificate for its new Model Falcon 7X airplane. The Model Falcon 7X is a 19 passenger transport category airplane, powered by three aft mounted Pratt & Whitney PW307A high bypass ratio turbofan engines. Operation of the airplane is accomplished using a fly-by-wire (FBW) primary flight control system. This will be the first application of a FBW primary flight control system in a private/corporate use airplane.

The Dassault Aviation Model Falcon 7X flightdeck design incorporates a hydrophobic windshield coating to provide adequate pilot compartment view in the presence of precipitation. Primary 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, a special condition is required that provides the level of safety equivalent to that established by the regulations.

Type Certification Basis

Under the provisions of 14 CFR 21.17, Dassault Aviation must show that the Model Falcon 7X airplane meets the applicable provisions of part 25, as amended by Amendment 25-1 through Amendment 25-108.

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 Falcon 7X 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 Falcon 7X 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 must also issue a finding of regulatory adequacy under § 611 of Public Law 92-574, the “Noise Control Act of 1972.”

The FAA issues special conditions, as defined in § 11.19, under § 11.38, and they become part of the type certification basis under § 21.17(a)(2).

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, the special conditions would also apply to the other model under § 21.101.

Novel or Unusual Design Features

The Model Falcon 7X will incorporate the following novel or unusual design feature: Hydrophobic windshield coating to provide adequate pilot compartment view in the presence of precipitation. Sole reliance on such a coating, without windshield wipers or a windshield blower, 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 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 V_SR1.

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 V_S1, 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 V_S1 to 1.5 V_SR1 to accommodate the redefinition of the reference stall speed from the minimum speed in the stall, V_S1, to greater than or equal to the 1-g stall speed. As noted in the preamble to the final rule for that amendment, the reduced factor of 1.5 on V_SR1 is to maintain approximately the same speed as the 1.6 factor on V_S1.

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, § 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 § 25.773(b)(1) at Amendment 25-108.

Discussion of Comments

Notice of proposed special condition No. 25-06-07 for the Dassault Aviation Model Falcon 7X airplane was published in the Federal Register on July 12, 2006 (71 FR 39235). No comments were received and this special condition is adopted as proposed.

Applicability

As discussed above, this special condition is applicable to the Model Falcon 7X. Should Dassault Aviation apply at a later date for a change to the type certificate to include another model on the same type certificate incorporating the same novel or unusual design feature, the special condition would apply to that model as well.

Effective Upon Issuance

Under standard practice, the effective date of final special conditions would be 30 days after the date of publication in the Federal Register; however, as the certification date for the Dassault Model Falcon 7X is imminent, the FAA finds that good cause exists to make this special condition effective upon issuance.

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 this special condition is as follows:

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

The Special Condition

Accordingly, pursuant to the authority delegated to me by the Administrator, the following special condition is issued as part of the type certification basis for Dassault Aviation Model Falcon 7X 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 V_SR1 with lift and drag devices retracted.

Issued in Renton, Washington, on December 29, 2006.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.