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May 06, 2013

Ron McCormick 5421 Horse Ridge Wa y Bonita, CA 91902 ram.ou812@gmail.com / (619) 434

- 1905

**§ 11.71 What information must I include in my petition for rulemaking?**  **(a) You must include the following information in y our petition for**  **rulemaking: (2)**  **An explanation of y** **our proposed action and its purpose.** This proposed action is to replace the elastomeric seals now used for fire barrier sealing of the inner fixed structure (IFS) portion of aircraft nacelles, with a metallic seal system, specifically in high operating temperature (<500°F) areas. Some regions of the engine compartment of turbine engine aircraft measure temperatures in the range of 625°F and above. Elastomeric seals

– after exposure to operating cycles (time and temperature )

– can only withstand temperatures below 500°F. **(3) The language y** **ou propose for a new or amended rule, or the language y ou**  **would remove from a current rule.** Replace the currently utilized elastomeric seals with a metallic seal system for sealing the IFS portion of typical clamshell nacelles of commercial turbine engine aircraft, specifically where operating temperatures reach above 500°F. **(4) An**  **explanation of w hy**  **your proposed action w ould be in the public**  **interest.** The current seal fire tests are perfor med using ’virgin’ seals that have not been exposed to a true operating life cycle (time and temperature). Seal life is determined by exposure to both high and low temperatures for a selected period of time. Elastomeric seals can only withstand approximate ly 480°F before degradation and permanent damage occurs. There is a known risk of using elastomeric seals, regardless of their material composition, when operating temperatures reach above 500°F. The properties of the elastomers degrade and can reach a poi nt where they fail as a seal and fire barrier. This failure can lead to pressure loss, leakage and other conditions that may compromise the performance and safety of the aircraft. Replacing these elastomeric seals with a metallic seal system that can withs tand high operating temperatures

- with no degradation of any kind, and maintaining full functionality

- will remedy the risks the elastomeric seals pose.2

**(5) Information and arguments that support your proposed action, including**  **relevant technical and sci entific data available to y**  **ou.** A metallic seal system has been designed and proven to function as well as elastomeric seals, without the risk of degradation and/or damage due high operating temperatures. Metallic seals, known as spring or turkey

- feather se als, have been used as fire barriers on aircraft nacelles, exhausts and other areas for several years. The material properties of alloys such as INCONEL have proven to be most effective in these applications. These alloys are able to withstand temperatures well above 500° F. In fact, AC20

- 135 6.d. (6) considers the use of these alloys as acceptable to use without additional fire tests required. Conversely, as a matter of fact, elastomeric seals cannot withstand operating temperatures above 500°F. Seal manufacturers state that at sustained temperatures above 500°F, the material properties of these seals

– even with added flame resistant fiber such as Nomex

– degrade and irreversibly break down, rendering the seal useless. Also, during required seal fire testi ng, elastomeric seals potentially produce outgasses and cause backside ignition

– which constitutes test failure. **(6) An**  **y specific facts or circumstances that support or demonstrate the need for the action y** **ou propose.** The current seal fire tests are perfo rmed using ’virgin’ seals that have not been exposed to a true operating life cycle (time and temperature). To date, fire seal testing of elastomeric seals has resulted in high failure rates, due to the composition of the seals. Wh en silicone is burned in air or oxygen, it forms solid silica (silicon dioxide) as a white powder, char, and various gases. The readily dispersed powder is sometimes called silica fume. This process does not lend itself well in a potential fire environment on an aircraft.
The vari ous manufacturers of elastomeric seals admit that

– to date

– elastomeric seals are NOT recommended when temperatures reach 500°F or above. In fact, a VP of one major elastomeric seal manufacturer states that these high temperatures require metallic seals. **(b) In the process of considering y our petition, we may**  **ask that y ou provide**  **information or data available to you about the following: (1) The costs and benefits of y**  **our proposed action to society in general, and**  **identifiable groups within society in part**  **icular.** The cost of the proposed metallic seal system to replace elastomeric seals is much less. Simple manufacturing and tooling requirement, as opposed to the complex manufacturing and costly tooling of the elastomeric seals, greatly reduces the overall cost. Although the elastomeric seals are expected to last the life of the aircraft, many issues that may occur negate this expectation. Due to the composition of the elastomeric seals3

and installation processes, the seals may get damaged and need replacem ent. Also, if the seals are exposed to temperatures over 500 degrees F for a prolonged length of time, the seals will need replacement. The reduced costs of the metallic seal system can very easily convert to lower airline costs and reduction of safety concerns to the consumer. **(2) The regulatory**

**burden of y our proposed action on small businesses, small**  **organizations, small governmental j urisdictions, and Indian tribes.**  n/a **(3) The recordkeeping and reporting burdens of y our proposed action and w**  **hom the burdens would affect.**  n/a **(4) The effect of y our proposed action on the quality**  **of the natural and social environments.**  Elastomeric seal m anufacturing, as well as the required testing constitutes a much larger carbon footprint than the proposed metallic seal system.