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14 CFR 11.81 (a) - Contact Information:

Sérgio Augusto Viana de Carvalho Embraer Airworthiness Manager Av. Brigadeiro Faria Lima, 2170 – PC 179 12227-901 São Jose dos Campos, SP - Brazil

Phone: 55-12-3927-3543

Fax: 55-12-3927-1184

14 CFR 11.81 (b) Specific Section from Which Exempt ion is required

14CFR 25.981 (a)(3), amendment 25-102.

(a) No ignition source may be present at each point in the fuel tank or fuel tank system where catastrophic failure could occur due t o 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 combina tion with each latent failure condition not shown to be extremely remote, and from

all combinations of failures not shown to be extrem ely improbable. The effects of manufacturing variability, aging, we ar, corrosion, and likely damage must be considered.

14 CFR 11.81 (c) Extent of Relief and Reason for Se eking Relief

Petition and General Information

Embraer has concluded that compliance to 14 CFR 25. 981(a)(3) for fuel tank structural lightning protection would require three independen t layers of protection.

No viable means of lightning protection are envisio ned in present construction technology that could address the three layers of p rotection for certain areas of the fuel tank structure. Particularly, fatigue cracking in s tructural elements of the fuel tank, and failure of highly loaded fuel tank fasteners leadin g to a separation from the hole or consequent failure of cap seal, present most diffic ulties in terms of means of compliance. Periodic inspection to monitor the cond ition of each fuel tank fastener is considered impractical due to the number (thousands ) and location (difficult access). Frequently accessing the fuel tanks for inspection also increases the risk of causingGCF

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damage to components inside the tanks or to lightni ng protective features, which is detrimental to the safety objectives.

Therefore, an exemption is being petitioned followi ng the recommendations in the FAA policy memo ANM-112-08-002.

The ANM-112-08-002 FAA policy memo provides the fol lowing alternate requirements:

1. Instead of compliance with the requirements of § 25.981(a)(3), the applicant must show that the design includes at least two independent, effective, and reliable lightning protection features (or sets of features) such that fault tolerance to prevent lightning-related ignition sources is pr ovided for each area of the structural design area proposed to be exempt from t he requirements of that regulation. Fault tolerance is not required for any specific design feature if: a) providing fault tolerance is shown to be impract ical for that feature, and b) fuel tank vapor ignition because of that feature and all other non-faulttolerant features, when their fuel tank vapor ignit ion event probabilities are summed, is shown to be extremely improbable.

2. The applicant must perform an analysis to show t hat the design, manufacturing processes, and airworthiness limitations section of the instructions for continued airworthiness include all practical measures to pre vent, and detect and correct, failures of structural lightning protection feature s because of manufacturing variability, aging, wear, corrosion, and likely dam age.

14 CFR 11.81 (d) Reason Why Granting Relief Would b e In Public Interest

Public Interest

Embraer has used state-of-art design practices and techniques to provide an adequate level of safety, and all practical measures have be en implemented in the design. In search of compliance with the requirement, addition al 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 significa nt impacts in weight, cost, manufacturing and maintenance, with no corresponden t increase in safety levels. Additional protection features could make more diff icult to perform fuel tank inspections. Increased frequency of inspection could lead to dam age to internal tank components and structure, as well as to the lightning protecti on features. Requiring the EMB-550 to attempt to directly comply with this rule would prevent Embraer to complete the design and certify the airc raft 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.GCF

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EMB-550 has state-of-the-art design solutions imple mented on the fuel tanks which comply with § 25.954 and SFAR 88 requirements. Embr aer considers that the solutions implemented on EMB-550 have an adequate level of sa fety and considers a grant of exemption applicable for this aircraft. Therefore, Embraer believes that it is in the publi c interest for the FAA to grant this exemption.

14 CFR 11.81 (e) Reasons Why Exemption would Not Ad versely Affect Safety

Justification:

Effect of Exemption on Safety

With current design practices for lightning protect ion, Embraer aircraft designs have

accumulated in excess of 24 million revenue service flight hours with no lightning related events. The accident free fleet history sho ws current Embraer wing designs have sufficient protection against lightning induce d fuel tank ignition events. This safety record for the fuel system designs upon which the EMB-550 design is based, indicates that the proposed fuel tank lightn ing protection design of the model

EMB-550 will be safe.

Proposed Risk Mitigation

Embraer will submit detailed Proprietary informatio n to the FAA about the measures taken in the EMB-550 design to provide practical st ructural lightning protection. In general, the EMB-550 lightning protection features are based on state of the art industry design practices for aluminum wing structure includ ing inherently conductive low resistance current paths. These protection features have been used in existing inservice designs.

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 F lammability Exposure on an airplane not exceeding three percent of the Flammability Exp osure Evaluation Time (FEET) as defined in Appendix N of part 25, or that of a conv entional unheated aluminum wing fuel tank in the airplane model being evaluated, whichev er is greater.GCF

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The fuel tanks are designed to have continuous vent ilation during flight and to be far

from aircraft heat sources.

Ignition prevention due to lightning strikes is ana lyzed according to the guidelines established by FAA policy memo ANM 112-08-002.

Embraer proposes to enhance the lightning protectio n by incorporating additional faulttolerant protection for fasteners in areas of poten tial swept lightning attachment (referred to as Zone 2) by sealing the fasteners to contain the products of a possible spark in the event that the primary protective feat ures fail, thereby increasing the level of fuel tank safety.

Embraer will show that the structural fastener desi gn of the EMB-550 wing will have two reliable and effective features for lightning prote ction. Testing will show that the fastener installation will be safe for applicable lightning zone requirements and will not produce any sparks inside the fuel tanks. Additionally, Emb raer will use the application of sealant, as a second layer of protection, to contai n a spark should one occur from a

failed fastener. For the limited areas in which a s ingle failure of a fastener could result in loss of both protection features, or any other area where a single layer of protection is all that can practically be provided, a safety asse ssment will be performed to show that the probability of a lightning related fuel tank ig nition event is extremely improbable. The systems supporting structure will also be analyzed as part of the fault tree assessment to ensure that they meet the requirements in the po licy memo. For fault-tolerant joint types, it will be demonstrated the independence of the two protective features already considered in the design of EMB-550 fuel tanks. For Non-Fault-Tolerant joint types, numerical probability assessment is performed to ve rify probability of fuel-vapor ignition and demonstrate that it is extremely improbable.

Embraer will verify that manufacturing quality and control is adequately performed and maintenance procedures consider CDCCL for fuel-syst em and fuel-tank structure.

Additionally, Embraer will utilize production proce dures 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 maintaine d. The instructions for continued airworthiness and repair procedures will also be pr ovided to ensure the protection features are maintained throughout the life of the airplane.

Verification of the low level of flammability expos ure, 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.GCF

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14 CFR 11.81 (f) Summary For Publication In Federal Register

Embraer requests an Exemption from 14 CFR 25.981(a) (3) Amdt. 25-102 for fuel tank structural lightning protection in the EMB-550 airc raft.

14 CFR 11.81 (g) Additional Information to Support Request

Exemption No 10.138 (Regulatory Docket No FAA-2009- 1206). This exemption is provided as evidence that the FAA has previously gr anted exemption from the same regulation for another Embraer aircraft, on the mat ter of fuel tank structure lightning protection.

Conclusions

Embraer is petitioning for an exemption for 14 CFR 25.981(a)(3) at amendment 102 for fuel tank structural lightning protection. Granting this exemption will allow Embraer to compl ete its design and certify the EMB550 for delivery. The proposed design for the EMB-550 will provide an appropriate level of safety against lightning induced fuel tank ignition, and will be s hown to comply with the alternative requirements established in the FAA policy memo ANM -112-08-002.