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###### Department of Transportation

# AGENCY:

Federal Aviation Administration, DOT.

# ACTION:

Notice of request for comments on nonmetallic transport category airplanes.

# SUMMARY:

This notice solicits public comment on the need for, and the possible scope of, rulemaking to address extensive use of nonmetallic materials in the construction of transport category airplanes.

# DATES:

We must receive comments on this notice by September 2, 2009.

# ADDRESSES:

You may mail comments to: Federal Aviation Administration (FAA), Transport Airplane Directorate, Aircraft Certification Service, ANM-100 (Attn: Jeff Gardlin, ANM-115), 1601 Lind Avenue, SW., Renton, Washington 98057-3359.

# FOR FURTHER INFORMATION CONTACT:

                        Jeff Gardlin, FAA, Airframe and Cabin Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue, SW., Renton, Washington 98057-3359; telephone (206) 227-2136.                              ( print page 26920)    

# SUPPLEMENTARY INFORMATION:

## Comments Invited

Interested persons are invited to participate in identifying the need for, and defining the scope of, rulemaking and advisory materials to address the extensive use of nonmetallic materials in the construction of transport category airplanes by submitting written data, views, or arguments as they may desire. Comments relating to the environmental, energy, or economic impact that might result from adopting the recommendations contained in this notice are invited. Substantive comments should be accompanied by estimates of their economic impact if possible. All comments received on or before the closing date for comments will be considered by the FAA before deciding whether to pursue rulemaking.

## Background

                    The certification standards for transport category airplanes are contained in Title 14, Code of Federal Regulations (14 CFR) part 25. These standards have evolved over the years and take into account the practicalities of how airplanes are designed and constructed. While it is in theory possible to develop standards that make no assumptions about the airplane design or materials,                     *i.e.,*                     pure performance standards, this is often extremely difficult. The standards themselves would have to anticipate virtually any design innovations, which would tend to make the standards very complex and lengthy or, conversely, so high level as to make it difficult to develop methods for demonstrating compliance. One area where the airworthiness standards of part 25 are based on an assumption is the principal materials of construction. For the most part, the regulations assume that the airplane fuselage, including wings and empennage—the airframe—will be constructed from metallic materials. Despite this assumption, nonmetallic materials have been used over the years for specific components on various airplane types. In those cases, the FAA has evaluated the safety effects of these specific designs, and in some cases has issued special conditions to identify appropriate certification criteria. However, the current regulatory standards do not account for an airframe that is constructed predominantly from nonmetallic materials. While special conditions are a tool to address individual certification projects, they are not a long-term solution to a shift in design philosophy. Airworthiness standards might need to evolve with evolving designs. Therefore, the FAA is considering whether a more comprehensive change to part 25 is appropriate.                

There is an obvious trend toward the increased use of composites in the construction of airplanes. Both Boeing and Airbus are in the process of developing large transport category airplanes using composite materials as the primary material in construction of the airframe. The FAA has written, or is in the process of writing, special conditions to incorporate adequate safety standards for these airplanes. Some of the special conditions supplement or replace requirements that either do not address all aspects of composites, or have criteria that are based on experience with metallic structure that is not applicable to composites. In either situation, the use of nonmetallic materials requires additional or modified standards to maintain the level of safety currently required for metallic materials. In other cases, the regulatory language may be sufficiently broad to address nonmetallic materials, but the advisory material may require updating.

The objective of this notice is to solicit public comments on the topics that should be addressed, if the FAA proceeds to rulemaking, and suggestions on the best way to amend part 25 to address the use of nonmetallic materials as the principal materials of construction.

As noted above, certification standards ideally would not assume the use of any particular materials, and would contain the standards necessary to assure the level of safety intended by the regulations regardless of the materials used. While that is a goal, it may not be completely achievable, and it is likely that certain assumptions regarding materials will be necessary for a manageable standard. Still, the FAA is approaching this effort with the objective of eliminating assumptions regarding materials as much as is feasible.

Based on our review of current programs, we believe the following areas would have to be addressed to account for the extensive use of nonmetallic materials in airframe construction:
    - Airframe crashworthiness
    - Fuel Tank crashworthiness
    - Post crash fire safety

 • Fuselage protection

 • Fuel tank protection
    - In-flight fire safety

 • Fuselage protection

 • Fuel tank protection
    - Lightning protection
    - Damage tolerance

The FAA seeks public input to further refine the areas of interest identified above, as well as identify any other relevant areas, in order to establish the scope of any regulatory efforts and advisory materials. Based on this input, the FAA may then proceed to rulemaking activity, or may elect to task the Aviation Rulemaking Advisory Committee with recommending specific changes to the regulations and applicable advisory materials.

Issued in Renton, Washington, on April 30, 2009.

Stephen P. Boyd,

Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.

[FR Doc. E9-12987 Filed 6-3-09; 8:45 am]

BILLING CODE 4910-13-P