December 20

th, 2013.

GCF-1958/2013 – 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 W12-140

Washington, DC 20590

Subject: EMB-550 - FAA Type Validation

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

EMBRAER respectfully submits the enclosed 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-550
GCF-1958/2013 – 2/5

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: 55-12-3927-1184

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), which 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-1958/2013 – 3/5

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 was 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 recommendations 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 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 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 would Not Adversely Affect Safety

With current design practices for lightning 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 fleet history shows current EMBRAER wing designs have sufficient 

protection against lightning induced fuel tank ignition events.
GCF-1958/2013 – 4/5

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 conventional unheated aluminum 

wing 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-tank 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 Publication in Federal Register

EMBRAER requests to the exemption from 14 CFR Part 25.981(a)(3) Amdt. 25-127 to 

allow certification schedule adherence.
GCF-1958/2013 – 5/5

14 CFR 11.81 (g) Additional 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. EMB550 are expected to be registered and operated in various countries throughout the 

world.

Conclusions:

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 design 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.