December 2 0 th , 2013.

GCF- 1 958/2013

– 1 /5 GNS/ra **EMBRAER S.A.**  Av. Brigadeiro Faria Lima, 2.170 12227 -901 - S.J. dos Campos - SP Brasil Fone: (12) 3927 -0544 Fax: (12) 3927 - 1184 PC: 179 US Department of Transportation 1200 New Jersey Avenue, SE West Building Ground Floor Room W1 2- 140 Washington, DC 20590 Subject: EMB-550 - FAA Type Validation

Petition to the Exemption from 14 CFR 25.981(a)(3)

EMBRAER respectfully submits the e nclosed Petition for a exemption for the EMB -550 from the requirement of 14 CFR Part 25.981(a)(3) as it relates to fuel tank water drain valve lightning protection.

Best Regards,

Sérgio Augusto Viana de Carvalho Airworthiness Director c .c.: ANAC - GPC EMB -550GCF- 1 958/2013

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**14 CFR 11.81 (a) -**  **Contact Information**  **:** Sérgio Augusto Viana de Carvalho Embraer Airworthiness Director Av. Brigadeiro Faria Lima, 2170

– PC 179 12227-901 São Jose dos Campos, SP - Brazil Phone: 55- 12 -3927-3543 Fax: 55- 12 -3927- 11 84 **14 CFR 11.81 (b) Specific Section from Which Exemption is required** § 25.981(a)(3) Fuel tank ignition prevention. (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 of failures not shown to be extremely improbable. The effects of manufacturing variability, aging, wear, corrosion, and likely damage must be considered. **14 CFR 11.81 (c) Extent of Relief and Reason for Seeking Relief** EMBRAER has to comply to 14 CFR Part 25.981(a)(3) for fuel tank systems lightning protection that requires three independent layers of protection. There is no viable means of lightning protection are envisioned in present construction technology that could address the three layers of protection for certain areas, or devices installed on the fuel tank system, such as the fuel tanks water drain valve. A detailed safety analysis was developed by both EMBRAER and its supplier, to identify all failure modes associated with the EMB -550 water drain valve and its installation. All single failure modes were tested and complied with the above mentioned requirement. Also, among all the possible dual failure combinations evaluated and tested, there is only one combination, associated with a dual poppet o’ring failure, that could allow a lightning strike to produce an incendiary spark inside the fuel tank. Although the EMB -550 water drain valve is installed on a lightning strike zone 2A, this component is made of Polyeterimide (Ultem), wh ich is a non -conductive material, making it an unlikely path for a lightning strike attachment. Additionally, all water drain valves will only be uncovered if the fuel levels are below the NBAA reserves, thus it can be concluded that no fuel vapors will be above the valve under normal operation.GCF- 1 958/2013

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Furthermore, a simple periodic inspection could remove the latency of an eventual failure of either one of the two o’rings. A review of the water drain valve design wa s performed, leading to the conclusion that an additional change on this component would be impracticable, once installing an additional o’ring was not considered reasonable, in view of its safety benefit and impact on the design change. Therefore, an exemption is being petitioned, following the reco mmendations in the FAA draft policy memo ANM -25.981 -02, since the component complies with all the conditions required to be included in the scope of the referred policy. **14 CFR 11.81 (d) Reason Why Granting Relief**  **would be**  **i n Public Interest**  **Public Inte rest:**  EMBRAER has used state-of-art design practices and techniques to provide an adequate level of safety, and all practical measures have been implemented in the design. In search of compliance with the requirement, additional features to comply with the third layer of protection have been considered, but were concluded to be impractical. Adoption of the third layer would lead to significant impacts in weight, cost, manufacturing and maintenance, with no correspondent increase in safety levels. Additional protection features could make more difficult to perform fuel tank inspections. Increased frequency of inspection could lead to damage to internal tank components and structure, as well as to the lightning protection features. Requiring the EMB -550 to attempt to directly comply with this rule would prevent EMBRAER to complete the design and certify the aircraft on a competitive schedule. It would also render the EMB -550 to be of lesser value to the public interest with no commensurate increase in safety. EMB -550 has state-of -the-art design solutions implemented on the fuel tanks which comply with 14 CFR Part 25.954 and SFAR 88 requirements. EMBRAER considers that the solutions implemented on EMB -550 have an adequate level of safety and considers a grant of exemption applicable for this aircraft. Therefore, EMBRAER believes that it is in the public interest for the FAA to grant this exemption. **14 CFR 11.81 (e) Reasons Why Exemption w** **ould Not A dv** **ersely A ffect Safety**  With current design practices for lig htning protection, including the present design installation of the water drain valve, EMBRAER aircraft designs have accumulated in excess of 24 million revenue service flight hours with no lightning related events. The accident free fl eet history shows cu rrent EMBRAER wing designs have sufficient protection against lightning induced fuel tank ignition events.GCF- 1 958/2013

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This safety record for the fuel system designs upon which the EMB -550 design is based, indicates that the proposed fuel tank lightning protection design of the water drain valve of model EMB -550 will be safe. EMBRAER will submit detailed Proprietary information to the FAA about the measures taken in the EMB -550 design to provide practical improvements in the water drain valve design lightning protection. In general, the EMB -550 lightning protection features are based on state of the art industry design practices for aluminum wing structure including inherently conductive low resistance current paths. These protection features of the water drain valve have been demonstrated to be fault tolerant. EMB -550 is being designed considering the following mitigation means:

- reduction of likelihood of flammable vapors, and

- prevention of ignition sources. Reduction of likelihood of flammable vapors will be complied with considering flammability standards of fuel tank Fleet Average Flammability Exposure on an airplane not exceeding three percent of the Flammability Exposure Evaluation Time (FEET) as defined in Appendix N of 14 CFR Part 25, or that of a conven tional unheated aluminum win g fuel tank in the airplane model being evaluated, whichever is greater. The fuel tanks are designed to have continuous ventilation during flight and to be far from aircraft heat sources. Ignition prevention due to lightning strikes is analyzed according to the guidelines established by FAA proposed policy memo ANM 25.981 -02. EMBRAER will verify that manufacturing quality and control is adequately performed and maintenance procedures consider CDCCL for fuel -system and fuel -tan k structure. Additionally, EMBRAER will utilize production procedures in order to minimize the risk of mis- installed protective measures, and to identify and repair errors in such a way that the lightning protection features will be maintained. The instructions for continued airworthiness and repair procedures will also be provided to ensure the protection features are maintained throughout the life of the airplane. Verification of the low level of flammability exposure, and the analysis and tests to be performed for the protection features failure modes identified on the fuel tank structure will show that the EMB -550 has an adequate level of safety, even with the absence of the third independent layer of protection. **14 CFR 11.81 (f) Summary for Publica** **tion i n Federal Register**  EMBRAER requests to the exemption from 14 CFR Part 25.981(a)(3) Amdt. 25- 127 to allow certification schedule adherence.GCF- 1 958/2013

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**14 CFR 11.81 (g) A dditional Information to Support Request**  **Operation Outside of the United States** In accordance with 14 CFR Part 11.81(h), Embraer requests that the privilege of exercising this exemption for operation outside of the United States be approved. EMB 550 are expected to be registered and operated in various countries throughout the world. 

### Concl **usions:** EMBRAER is petitioning for an exemption for 14 CFR Part 25.981(a)(3) for fuel tank water drain valve lightning protection. Granting this exemption will allow EMBRAER to complete its design and certify the EMB -550 for delivery. The proposed desi gn for the EMB -550 will provide an appropriate level of safety against lightning induced fuel tank ignition, and will be shown to comply with the alternative requirements established in the FAA proposed policy memo ANM -25.981 -02

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