1170 Peachtree Street

Suite 1200
Atlanta GA 30309

Phone: 404

- 346

- 7175 www.jetairegroup.com



### August 9, 2010

Ref. 9027

- 100

- 005

Mr. Ali Bahrami Manager, Transport Airplane Directorate

Federal Aviation Administration

Aircraft Certification Service Seattle ACO 1601 Lind Avenue, SW Renton, WA 98055

- 4056

Mr. Bahrami:

Petitioner Jetaire Aerospace & Technology, Inc. (hereinafter "Jetaire" or "Petitioner") hereby requests an exemption from certain requirements of Title 14, Code of Federal Regulations (CFR) 25.981(a)(3), as amended by Amendments 25

- 102 and 25

- 125, for its innovative use of reticulated polyurethane foam technology as a fire and ignition source suppressant in certain transport category aircraft fuel tanks. The proposed exemption, if granted, would allow Petitioner to enhance the safety of aircraft su bject to the requirements of 14 C.F.R. 25.981 ("Rule 25.981") to a much greater degree than currently approved methods of compliance utilizing a combined use of transient suppression devices ("TSDs") and "gas inerting" techniques. In particular, granting of this Petition will allow Jetaire to certify and complete modification of auxiliary fuel tanks of models B727, B737 and DC

- 9 aircraft with auxiliary fuel tanks installed per various Supplemental Type Certificates. Granting of the partial exemption would permit complete compliance with Rule 25.981 by utilizing reticulated foam technology as a means of compliance to 25.981.

Jetaire Aerospace & Technology, Inc. has at least three (3) clients/aircraft owners whose current projects have are at various stages of completion and are awaiting approval and certification of the RPF method to return their aircraft to airworthiness. Until such time as this exemption is granted, these owners and similar aircraft owners that have gained extensions of time for compliance with Rule 25.981, are unable to fly their aircraft. Obviously, extended downtime in which these aircraft cannot be used is endured at great and unnecessary expense.

### Mr. Ali Bahrami

Manager, Transport Airplane Directorate

Federal Aviation Administration Page 2

Therefore, Jetaire requests the FAA to exempt Petitioner from full compliance with 14 CFR 25.981(a)(3) requiring the demonstration of a complete elimination of the possibility of an ignition source in the fuel tank or fuel tank system as it pertains to auxiliary fuel tanks.

If there are any questions concerning this matter I can be reached vi a e

- mail at mwilliams@jetairegroup.com or by cellular at 770

- 356

- 6562.

Sincerely,

Michael D. Williams

President

Enclosures

C c: Melvin Taylor

- Atlanta ACO

### 1 August 9, 2010

Mr. Ali Bahrami Manager, Transport Airplane Directorate

Aircraft Certification Service Seattle ACO 1601 Lind Avenue, SW Renton, WA 98055

- 4056

RE: Petition for Partial Permanent Exemption from 14 C.F.R. 25.981 regarding auxiliary fuel tan ks for aircraft models B727, B737 and DC

- 9.

PETITION FOR PARTIAL PERMANENT

EXEMPTION PERTAINING TO 14 C.F.R. 25.981

Petitioner Jetaire Aerospace & Technology, Inc. (hereinafter "Jetaire" or "Petitioner") hereby requests an exemption from certain require ments of Title 14, Code of Federal Regulations (CFR) 25.981(a)(3), as amended by Amendments 25

- 102 and 25

- 125, for its innovative use of reticulated polyurethane foam technology as a fire and ignition source suppressant in certain transport category

aircra ft fuel tanks. The proposed exemption, if granted, would allow Petitioner to enhance the safety of aircraft subject to the requirements of 14 C.F.R. 25.981 ("Rule 25.981") to a much greater degree than currently approved methods of compliance utilizing a c ombined use of transient suppression devices ("TSDs") and "gas inerting" techniques. In particular, granting of this Petition will allow Jetaire to certify and complete modification of auxiliary fuel tanks of models B727, B737 and DC

- 9 aircraft with auxil iary fuel tanks installed per various Supplemental Type Certificates. Granting of the partial exemption would permit complete compliance with Rule 25.981 by utilizing reticulated foam technology.

Petitioner requests relief from the following regulation:

14 C.F.R. 25.981(a)(3), Fuel tank ignition prevention, as amended by Amendments 25

- 102 and 25

- 125:

"(a) No ignition source may be present at each point in the fuel tank or fuel tank system where catastrophic failure could occur due to ignition of fuel or vapors. This must be shown by:

(3) Demonstrating that an ignition source could not result from each single failure, from each single failure in combination with each latent failure condition not shown to be extremely remote, and from all combinations or failures not shown to be extremely improbable. The effects of manufacturing variability, aging, wear, corrosion, and likely damage must be considered."

Rule 25.981 has two (2) relevant amendments that are applicable to Jetaire's demonstration of an

"acce ptable level of safety" within its ELOS document; Amendment 25

- 102 and Amendment 25

- 125. Admittedly, 25

- 102 was replaced by 25

- 125; however, 25

- 125 primarily effects amendments to Rule 25.981(b) and retains the language of Amendment 25

- 102 to Rule 25.981( c). The amended language of Rule 25.981(c) states as follows:

"(c) Paragraph (b) of this section does not apply to a fuel tank if means are provided to mitigate the effects of an ignition of fuel vapors within that fuel tank such that no damage caused by an ignition will prevent continued safe flight and landing (emphasis added)."

### 2

The petitioner supports its request with the following information:

I. Background

The use of reticulated polyurethane foam ("RPF") to prevent ignition and explosion within

ai rcraft fuel tanks has been in use for more than thirty

- five (35) years. As a result of its long history of use in military applications, there is substantial quantitative and qualitative data that supports its explosion mitigation effect under conditions t hat are more stringent and hazardous than ordinary commercial flight operations. Further, Chapter 12 of Advisory Circular 25.981

- 2A states:

"a. [O]ne means to meet §25.981 is to protect a tank from structural and systems damage that could prevent contin ued safe flight and landing of the airplane. This alternative recognizes that an applicant may choose to accept a high flammability exposure in a given tank and to provide additional protection to extinguish or suppress an explosion in a tank if an igniti on occurs.

b. The use of appropriate foams to fill the fuel tank and thereby control the pressure rise following an ignition of the fuel vapor/air mixture has been demonstrated to be effective by the United States Air Force and other military forces. Fo ams are in use on several civilian transport category airplane types. Detailed design information regarding use of reticulated polyurethane safety foam for explosion suppression is provided in the report referenced in paragraph 4d(1) of this AC. The appl icant may use such a foam installation to satisfy the requirement of §25.981 ( emphasis added ). The foam type should be demonstrated to be effective in suppressing explosions to a level where structural and system damage is prevented. The applicant shoul d:

(1) Provide data on the foam, including material, pore size, and intended method for installing the foam in the tank.

(2) Address the potential for, and the effects of, degradation of the foam, from any environmental effects and long term aging, on both the airplane and engine fuel systems. If the foam has a limited useful life, particular installation requirements, or other features that are essential for the IMM to perform its intended function, they should

be identified as CDCCLs. (3) Address t he effects of the foam installation on fuel system performance, including engine feed, venting, unusable fuel, sump capacity, expansion space capacity, fueling, and defueling, including the effect of the foam on electrostatic buildup in the

tank.

(4) Add ress the effect of the foam installation on the airplane fuel system, as well as the auxiliary power unit (APU) and engine fuel systems, and develop maintenance procedures to ensure the foam is correctly installed, both initially and when reinstalled, if r emoved for access to the tank."

Advisory Circular 25.981

- 2A clearly states in paragraph b. that a foam installation may be used to satisfy the requirements of §25.981 without reference to an isolated subparagraph of the Rule. In other words, a

foam ins tallation may satisfy the complete requirements of Rule 25.981 if the four (4) enumerated conditions are meet by an applicant. Jetaire has demonstrated that the foam application utilized in auxiliary tanks in B727, B737 and DC

- 9 model aircraft is effectiv e in suppressing explosions to a level

### 3

where structural and system damage is prevented and all four of the conditions stated in the AC are

addressed.

When measuring the acceptable level of safety offered by RPF in satisfying the purpose of Rule

25.98 1, particularly revealing and helpful studies involve the examination of RPF removed from aircraft fuel tanks after years of use. One such study, dated July 17, 1998, entitled Foam , compiled by the Fuel Tank Foam and Expanded Metal Products Task Group, Ta sk Group 4 for the Aviation Rulemaking Advisory Committee demonstrated that multiple "sparks" had occurred within the aircraft fuel tanks and had recorded burns on the surface of RPF present in the tanks. This evidence revealed that although ignition spar

ks had occurred within the tanks , there was no recorded incidence of a catastrophic explosion. In other words, ignition sparks entering the tanks were prevented from escalation to an expanded flammability and explosion by the presence of the RPF foam. N o catastrophic failures resulting in a fuel tank explosion had occurred

.

II. Public Interest

Full compliance to 25.981(a)(3) with respect to the demonstration of a complete elimination of the possibility of an "ignition source that could result from eac h single failure, from each single failure in combination" in auxiliary fuel tanks for the B727, B737 and DC

- 9 models will require significant redesign and modifications to the fuel tank, electrical systems and structure with no measurable improvements to aircraft safety. In addition to introducing additional complexity in the manufacturing, quality and maintenance procedures, a redesign of the proven technologies described above will add significant cost and schedule impact to the Model B727, B737 and DC

- 9 owners.

When measuring 14 CFR Part 25 contains the minimum design standards for type certification of transport category airplanes. The primary intent of these regulations is to ensure that airplane manufacturers provide the appropriate design features to meet the standards necessary to protect the traveling public. Clearly, there is a requirement "in the public interest" and in the interest of safety to provide Regulatory guidelines for certification. However, it is also very clear that these regulatio ns are intended to regulate the certification of "commercial" airplanes which are "for hire" to the general public.

While the majority of these regulations are applicable to any aircraft regardless of its intended use, a few are obviously intended to regu late situations that are specific to a commercial airline or "for hire" operation. When a transport category airplane is operated under 14 CFR Part 91 or Part 125 as "private

use, not

- for hire", some of the Part 25 regulations contain design criteria that are inappropriate, or are not compatible with the type of operation and the intended use of this airplane.

FAA requirements against the Petitioner's use of reticulated polyurethane foam in auxiliary tanks for compliance with this rule will prevent Jetair e and its customers/aircraft owners from certifying the aircraft on a timely and competitive schedule. This puts Jetaire at an unfair disadvantage with its competitors. Moreover, the use of reticulated polyurethane foam has been shown to increase the lev el of safety intended by Rule 25.981 to a degree substantially greater than that achieved by the use of TSDs and the combined use of TSDs and gas inerting techniques in combination. Particularly, the probability of failure of a static system, such as foam , is far less than the use of electronics and dependent systems such as transient suppression. Many private owners of B727, B737 and DC

- 9 aircraft around the US and the world that use their aircraft for business needs are anticipating the certification of their aircraft with the safer RPF alternative. Failing certification, these owners would be forced to find more costly and less

safe alternatives.

### 4

III. Effect on Safety

The use of reticulated polyurethane foam installed in aircraft auxiliary fuel tank s ystems is intended to fully comply with 14 CFR 25.981, as amended per amendment 102, and meet flammability and ignition source requirements. The Air Force has successfully been using the conductive type

reticulated foam since the 1980’s and has not had one ignition source incident other than when the RPF was inadvertently left out of a fuel nacelle.

Reticulated polyurethane foam is a FAA approved Ignition Mitigation Means (Chapter 12 of AC

25.981

- 2A) to meet § 25.981 by protecting the auxiliary tanks from structural and systems damage that could prevent continued safe flight and landing of the airplane. This alternative recognizes acceptance of a higher flammability exposure in a given tank and provides additional protection to extinguish or

suppress an ex plosion in a tank if an ignition occurs. The tanks as currently installed in the pressurized Class D Baggage compartments of the DC

- 9 have been analyzed utilizing the Fuel Tank Flammability Assessment program that applies Monte Carlo simulations to determi ne Flammability exposure. The analysis showed that the unmodified tanks had an exposure of less than 3%. With the addition of the RPF the flammability exposure was determined to be insignificant.

In order to suppress an ignition source, the use of appro priate foams to fill the fuel tank and thereby control the pressure rise following an ignition of the fuel vapor/air mixture has been demonstrated to be effective by the United States Air Force (USAF) and other military forces. Foams are in use on

several civilian transport category airplane types. Detailed design information regarding the use of reticulated polyurethane safety foam for explosion suppression is provided in Report MIL

- B

- 83054, Baffle and Inerting Material, Aircraft Fuel Tank (March 1984). Th e report demonstrates that proper application of a foam installation satisfies the requirements of § 25.981. RPF installed in aircraft auxiliary tanks has demonstrated, in accordance with MIL

- F

- 87260

- A, to be effective in suppressing explosions to

a level where structural and system damage is prevented. This conclusion was substantiated by:

(1) Providing data on the foam, including material, pore size, and intended method for installing the foam in the tank;

(2) Addressing the potential for, and the effects of, degradation of the foam, from any environmental effects and long term aging, on both the airplane and engine fuel systems. Defining in the CDCCL the foams limited useful life, particular installation requirements,

and other features that are essential for the IMM to perform its intended function; and

(3) Addressing through test and analysis the effects of the foam installation on fuel system performance, including engine feed, venting, unusable fuel, sump capacity, expansion space capacity, fueling, and defueling, including the effect of the foam on electrostatic buildup in the tank.

The fuel tanks with the RPF installed endured a rigorous System Safety Analysis that showed that, with the addition of the RPF and the application of specific ignition source prevention techniques outlined in

AC 25.981

- 1C paragraphs 9 & 10 the auxiliary tanks will:

(1) Not cause an ignition source for each single failure, regardless of the probability of

occurrence;

(2) Ensure that each single failure, regard less of the probability of occurrence, in combination with any latent failure condition not shown to be at least extremely remote

### 5 (i.e., not shown to be extremely remote or extremely improbable), will not cause an ignition source; and

(3) Ensure that all combinations of failures not shown to be extremely improbable will not cause an ignition source.

Furthermore, the RPF has demonstrated that the material can provide a number of added benefits beyond that of internal ignition source and flammability protec tion. Such added benefits include reduction in slosh and vibration effects and the entrapment of foreign objects and lose debris.

Consequently, taking into account all aspects of fuel tank flammability reduction and ignition suppression for which the aux iliary fuel tanks are compliant, and regarding the low flammability exposure as a mitigation factor for the absence of a third protection against an ignition source, Jetaire believes granting this exemption has no impact on safety.

IV. Timing aspects of r equest

Jetaire Aerospace & Technology, Inc. has at least three (3) clients/aircraft owners whose current projects have been substantially completed and are awaiting only approval and certification of the RPF

method to return their aircraft to airworthines s. Until such time as this exemption is granted, these owners and similar aircraft owners that have gained extensions of time for compliance with Rule 25.981, are unable to fly their aircraft. Obviously, extended downtime in which these aircraft cannot be used is endured at great and unnecessary expense.

Jetaire has previously demonstrated that full compliance with Rule 25.981 has been satisfied by the use of reticulated polyurethane foam in auxiliary fuel tanks, in that, the use of foam eliminates the

pos sibility of catastrophic failure resulting from an ignition in the fuel tanks or fuel tank systems to a greater degree than that of an extreme improbability without the use of TSDs.

Therefore, Jetaire requests the FAA to exempt Petitioner from full compli ance with 14 CFR 25.981(a)(3) requiring the demonstration of a complete elimination of the possibility of an ignition source in the fuel tank or fuel tank system as it pertains to auxiliary fuel tanks.

V. International Operations

Owners of the subjec t aircraft frequently use the aircraft in international travel; therefore, Jetaire requests the FAA to include use outside of the United States. Due to the small number of aircraft and the fact that they are operated under 14 CFR Part 91 or Part 125 as " private use, not

- for hire", the approval of the exemption for international use has an insignificant impact on the flying public.

Before Jetaire extends the requested exemption for use outside the United States, it will verify

that the exemption would be in compliance with the Standards of the International Civil Aviation Organization (ICAO). If it would not, but we still believe it would be in the public interest to allow you to do so, we will file a difference with ICAO. However, a foreign country still may not allow an aircraft to operate in that country without meeting the ICAO standard.

### 6

VI. Conclusion

Jetaire requests that its innovative use of reticulated polyurethane foam to mitigate ignition within auxiliary fuel tanks and fuel systems of B727, B737, and DC

- 9 aircraft be exempted from compliance with Rule 25.981(a)(3) as described above. The granting of Jetaire's request will enhance the safety of aircraft subject to compliance with 14 C.F.R. 25.981 in excess of the level of safety achieved by t he use of transient suppression devices and the combined use of transient suppression devices and gas inerting procedures. Requiring the addition of transient suppression devices to Jetaire's proposed use of reticulated polyurethane foam would not further increase or enhance the level of safety in the fuel tanks or fuel systems to achieve the safety levels intended or dictated by Rule 25.981. The requirement of transient suppression devices in addition to the use of reticulated polyurethane foam is, there fore, an ineffective and unnecessary expense to the public that does not significantly impact or increase the level of safety achieved by the use of reticulated polyurethane foam.