Airworthiness standards: Special conditions Boeing Model 757 series airplanes,
[Federal Register: November 27, 2007 (Volume 72, Number 227)]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
Proposed Rules Federal Register
This section of the FEDERAL REGISTER contains notices to the public of the proposed issuance of rules and regulations. The purpose of these notices is to give interested persons an opportunity to participate in the rule making prior to the adoption of the final rules.
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM385; Notice No. 25-07-17-SC]
Special Conditions: Boeing Model 757 Series Airplanes; Seats With Non-Traditional, Large, Non-Metallic Panels
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed special conditions.
SUMMARY: This action proposes special conditions for Boeing Model 757 series airplanes. These airplanes, as modified by Triad International Maintenance Company (TIMCO), will have a novel or unusual design feature(s) associated with seats that include non-traditional, large, non-metallic panels that would affect survivability during a post-crash fire event. 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: We must receive your comments by December 12, 2007.
ADDRESSES: You must mail two copies of your comments to: Federal Aviation Administration, Transport Airplane Directorate, Attn: Rules Docket (ANM-113), Docket No. NM385, 1601 Lind Avenue, SW., Renton, Washington 98057-3356. You may deliver two copies to the Transport Airplane Directorate at the above address. You must mark your comments: Docket No. NM385. You can inspect comments in the Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.
FOR FURTHER INFORMATION CONTACT: Dan Jacquet, FAA, Airframe/Cabin Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue, SW., Renton, Washington 98057- 3356; telephone (425) 227-2676; facsimile (425) 227-1232; electronic mail firstname.lastname@example.org.
We invite interested people to take part in this rulemaking by sending 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. You can inspect the docket 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 based on 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.
On July 31, 2007, Triad International Maintenance Company (TIMCO), 623 Radar Road, Greensboro, North Carolina 27410, applied for a supplemental type certificate for installing seats that include non- traditional, large, non-metallic panels in a Boeing Model 757 series airplane. The Boeing Model 757 series airplanes, currently approved under Type Certificate No. A2NM, are swept-wing, conventional tail, twin-engine, turbofan-powered, single aisle, medium-sized transport category airplanes.
The applicable regulations to airplanes currently approved under Type Certificate No. A2NM do not require seats to meet the more stringent flammability standards required of large, non-metallic panels in the cabin interior. At the time the applicable rules were written, seats were designed with a metal frame covered by fabric, not with large, non-metallic panels. Seats also met the then recently adopted standards for flammability of seat cushions. With the seat design being mostly fabric and metal, the contribution to a fire in the cabin had been minimized and was not considered a threat. For these reasons, seats did not need to be tested to heat release and smoke emission requirements.
Seat designs have now evolved to occasionally include non- traditional, large, non-metallic panels. Taken in total, the surface area of these panels is on the same order as the sidewall and overhead stowage bin interior panels. To provide the level of passenger protection intended by the airworthiness standards, these non- traditional, large, non-metallic panels in the cabin must meet the standards of Title 14 Code of Federal Regulations (CFR), part 25, Appendix F, parts IV and V, heat release and smoke emission requirements.
Type Certification Basis
Under the provisions of 14 CFR 21.101, TIMCO must show that the Boeing Model 757 series airplanes, as changed, continue to meet the applicable provisions of the regulations incorporated by reference in Type Certificate No. A2NM, or the applicable regulations in effect on the date of application for the change. 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 No. A2NM are as follows:
For Model 757-200 airplanes--part 25, as amended by Amendment 25-1 through Amendment 25-45. In addition, an equivalent safety finding exists with respect to Sec. 25.853(c), Compartment interiors.
For Model 757-300 airplanes--part 25, as amended by Amendment 25-1 through Amendment 25-85 with the exception listed: Section 25.853(d)(3), Compartment interiors, at Amendment 25-72.
In addition, the certification basis includes certain special conditions,
exemptions, or later amended sections of the applicable part that are not relevant to these proposed special conditions.
If the Administrator finds that the applicable airworthiness regulations (i.e., part 25) do not contain adequate or appropriate safety standards for the Boeing Model 757 series airplanes 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 Boeing Model 757 series airplanes 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 issues special conditions, as defined in Sec. 11.19, under Sec. 11.38 and they become part of the type certification basis under Sec. 21.101.
Special conditions are initially applicable to the model for which they are issued. Should the applicant apply for a supplemental type certificate to modify any other model included on the same type certificate to incorporate the same or similar novel or unusual design feature, the special conditions would also apply to the other model under Sec. 21.101.
Novel or Unusual Design Features
The Boeing Model 757 series airplanes will incorporate the following novel or unusual design features: These models offer interior arrangements that include passenger seats that incorporate non- traditional, large, non-metallic panels in lieu of the traditional metal frame covered by fabric. The flammability properties of these panels have been shown to significantly affect the survivability of the cabin in the case of fire. These seats are considered a novel design for transport category airplanes that include Amendment 25-61 and Amendment 25-66 in the certification basis, and were not considered when those airworthiness standards were established.
The existing regulations do not provide adequate or appropriate safety standards for seat designs that incorporate non-traditional, large, non-metallic panels in their designs. In order to provide a level of safety that is equivalent to that afforded to the balance of the cabin, additional airworthiness standards, in the form of special conditions, are necessary. These special conditions supplement Sec. 25.853. The requirements contained in these special conditions consist of applying the identical test conditions required of all other large panels in the cabin, to seats with non-traditional, large, non-metallic panels.
Definition of ``Non-Traditional, Large, Non-Metallic Panel''
A non-traditional, large, non-metallic panel, in this case, is defined as a panel with exposed-surface areas greater than 1.5 square feet installed per seat place. The panel may consist of either a single component or multiple components in a concentrated area. Examples of parts of the seat where these non-traditional panels are installed include, but are not limited to: Seat backs, bottoms and leg/foot rests, kick panels, back shells, credenzas and associated furniture. Examples of traditional exempted parts of the seat include: Arm caps, armrest close-outs such as end bays and armrest-styled center consoles, food trays, video monitors, and shrouds.
Clarification of ``Exposed''
``Exposed'' is considered to include panels that are directly exposed to the passenger cabin in the traditional sense, and panels that are enveloped, such as by a dress cover. Traditional fabrics or leathers currently used on seats are excluded from these special conditions. These materials must still comply with Sec. 25.853(a) and Sec. 25.853(c) if used as a covering for a seat cushion, or Sec. 25.853(a) if installed elsewhere on the seat. Non-traditional, large, non-metallic panels covered with traditional fabrics or leathers will be tested without their coverings or covering attachments.
In the early 1980s the FAA conducted extensive research on the effects of post-crash flammability in the passenger cabin. As a result of this research and service experience, we adopted new standards for interior surfaces associated with large surface area parts. Specifically, the rules require measurement of heat release and smoke emission (part 25, Appendix F, parts IV and V) for the affected parts. Heat release has been shown to have a direct correlation with post- crash fire survival time. Materials that comply with the standards (i.e., Sec. 25.853 entitled ``Compartment interiors'' as amended by Amendment 25-61 and Amendment 25-66) extend survival time by approximately 2 minutes over materials that do not comply.
At the time these standards were written the potential application of the requirements of heat release and smoke emission to seats was explored. The seat frame itself was not a concern because it was primarily made of aluminum and there were only small amounts of non- metallic materials. It was determined that the overall effect on survivability was negligible, whether or not the food trays met the heat release and smoke requirements. The requirements therefore did not address seats. The preambles to both the Notice of Proposed Rule Making (NPRM), Notice No. 85-10 (50 FR 15038, April 16, 1985) and the Final Rule at Amendment 25-61 (51 FR 26206, July 21, 1986), specifically note that seats were excluded ``because the recently-adopted standards for flammability of seat cushions will greatly inhibit involvement of the seats.''
Subsequently, the Final Rule at Amendment 25-83 (60 FR 6615, March 6, 1995) clarified the definition of minimum panel size: ``It is not possible to cite a specific size that will apply in all installations; however, as a general rule, components with exposed-surface areas of one square foot or less may be considered small enough that they do not have to meet the new standards. Components with exposed-surface areas greater than two square feet may be considered large enough that they do have to meet the new standards. Those with exposed-surface areas greater than one square foot, but less than two square feet, must be considered in conjunction with the areas of the cabin in which they are installed before a determination could be made.''
In the late 1990s, the FAA issued Policy Memorandum 97-112-39, Guidance for Flammability Testing of Seat/Console Installations, October 17, 1997 (http://rgl.faa.gov). That memo was issued when it
became clear that seat designs were evolving to include large, non- metallic panels with surface areas that would impact survivability during a cabin fire event, comparable to partitions or galleys. The memo noted that large surface area panels must comply with heat release and smoke emission requirements, even if they were attached to a seat. If the FAA had not issued such policy, seat designs could have been viewed as a loophole to the airworthiness standards that would result in an unacceptable decrease in survivability during a cabin fire event.
In October of 2004, an issue was raised regarding the appropriate flammability standards for passenger seats that incorporated non- traditional, large, non-metallic panels in lieu of the traditional metal covered by fabric. The Seattle Aircraft Certification Office and Transport Standards Staff reviewed this design and determined that it represented the kind and quantity of material that should be required to pass the heat release and smoke emissions
requirements. We have determined that special conditions would be promulgated to apply the standards defined in Sec. 25.853(d) to seats with large, non-metallic panels in their design.
As discussed above, these special conditions are applicable to Boeing Model 757 series airplanes. It is not our intent, however, to require seats with large, non-metallic panels to meet Sec. 25.853, Appendix F, parts IV and V, if they are installed in cabins of airplanes that otherwise are not required to meet these standards. Because the heat release and smoke testing requirements of Sec. 25.853 per Appendix F, parts IV and V, are not part of the type certification basis of the Model 757, these special conditions are only applicable if the Model 757 series airplanes are in 14 CFR part 121 operations. Section 121.312 requires compliance with the heat release and smoke testing requirements of Sec. 25.853, for certain airplanes, irrespective of the type certification bases of those airplanes. For Model 757 series airplanes, these are the airplanes that would be affected by these special conditions. Should TIMCO apply at a later date for a supplemental type certificate to modify any other model included on Type Certificate No. A2NM to incorporate the same novel or unusual design feature, the special conditions would apply to that model as well.
This action affects only certain novel or unusual design features on one model series of airplanes. It is not a rule of general applicability and it affects only the applicant who applied to the FAA for approval of these features on the airplane.
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 Proposed Special Conditions
Accordingly, the Federal Aviation Administration (FAA) proposes the following special conditions as part of the type certification basis for Boeing Model 757 series airplanes modified by TIMCO.
Except as provided in paragraph 3 of these special conditions, compliance with Title 14 CFR part 25, Appendix F, parts IV and V, heat release and smoke emission, is required for seats that incorporate non- traditional, large, non-metallic panels that may either be a single component or multiple components in a concentrated area in their design.
The applicant may designate up to and including 1.5 square feet of non-traditional, non-metallic panel material per seat place that does not have to comply with special condition Number 1, above. A triple seat assembly may have a total of 4.5 square feet excluded on any portion of the assembly (e.g., outboard seat place 1 square foot, middle 1 square foot, and inboard 2.5 square feet).
Seats do not have to meet the test requirements of Title 14 CFR part 25, Appendix F, parts IV and V, when installed in compartments that are not otherwise required to meet these requirements. Examples include:
Airplanes with passenger capacities of 19 or less,
Airplanes that do not have Sec. 25.853, Amendment 25-61 or later, in their certification basis and do not need to comply with the requirements of 14 CFR Sec. 121.312, and
Airplanes exempted from Sec. 25.853, Amendment 25-61 or later.
Issued in Renton, Washington, on November 19, 2007. Ali Bahrami, Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. E7-23079 Filed 11-26-07; 8:45 am]
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