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May 06, 2013

Ron McCormick

5421 Horse Ridge Way

Bonita, CA 91902

r am .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 your petition for rulemaking:

(2) An explanation of your 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) p ortion 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 you propose for a new or amended rule, or the language you
would remove from a current rule.

Replace the currently utilized elastomer ic 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 why your proposed action would be in th e public
interest.

The current seal fire tests are per formed 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 perio d of time. Elastomeric seals can only withstand approximately 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. T he properties of the elastomers degrade and can reach a point 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 e lastomeric seals with a metallic seal system that can withstand 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 scientific data available to you.

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 tempera tures.

Metallic seals, known as spring or turkey

- feather seals, 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 ap plications. 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 cann ot 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, render ing the seal useless. Also, during required seal fire testing, elastomeric seals potentially produce outgasses and cause backside ignition

– which constitutes test failure.

(6) Any specific facts or circumstances that support or demonstrate the need
for th e action you propose.

The current seal fire tests are performed 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. When silicone is burned in air or oxygen, it forms solid silica (silicon dioxide) as a white powder, char, and va rious 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 various manufacturers of elastomeric seals admit that

– to date

– elastomeric seals
are NO T 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 your petition, we may ask that you provide
informat ion or data available to you about the following:

(1) The costs and benefits of your proposed action to society in general, and identifiable groups within society in particular.

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, m any 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 replacement. 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 your proposed action on small bus inesses, small organizations, small governmental jurisdictions, and Indian tribes.

n/a

(3) The recordkeeping and reporting burdens of your proposed action and whom
the burdens would affect.

n/a

(4) The effect of your proposed action on the quality of the n atural and social
environments.

Elastomeric seal manufacturing, as well as the required testing constitutes a much larger carbon footprint than the proposed metallic seal system.