May 31, 2010.

GCF-0583/2010 – 1/16

NKK
Embraer Empresa Brasileira de Aeronáutica S.A.

Av. Brigadeiro Faria Lima, 2.170 12227-901 - S.J. dos Campos - SP Brazil

Phone: (55 12) 3927-2565 Fax: (55 12) 3927-1184 PC: 179 Mr.
Robert Jones Acting Manager, Propulsion/Mechanical Systems, ANM- 112 Transport Standards Staff / Transport Airplane Dire ctorate / Aircraft Certification Service
Federal Aviation Administration Northwest Mountain Region
1601 Lind Avenue S.W. Renton, Washington 98057-3356

Subject: EMB-135 BJ with DCA 0145-000-00020-2008/FA A (Legacy 650)

Petition for Exemption §25.981(a)(3)
Reference: 1. Embraer letter No GCF-1957/2009 for relief of §2 5.981(a)(3),

reference FAA Docket No 2009-1206 2. FAA letter issued on April 14, 2010 in reply to Embraer letter (GCF1957/2009) for relief of §25.981(a)(3)

Dear Mr. Robert Jones:

As required by FAA letter issued on April 14 for re lief of §25.981(a)(3), Embraer submits the requested information of the fault tolerance an alysis performed for EMB-135 BJ model with enhanced performance, which included Amd t 25-102 in its certification basis as explained in Embraer letter No GCF-1957/2009.

Embraer performed lightning tests of fuel tanks rep resentative structural joints located in lightning zones 2A and 3. These determined which ar e the Fault Tolerant and Non Fault
Tolerant Features.

Therefore, Non Fault tolerant features were analyze d by a Numerical Probability Assessment in order to verify if fuel vapor ignitio n due to these features is extremely improbable to occur.

Manufacturing Process was analyzed considering typi cal failure modes during the whole process of the fuel tanks production.

Maintenance was reviewed considering specific tasks to check typical failure modes during repair or maintenance of the fuel tanks thro ugh CDCCL instructions. Non fault
tolerant features are considered too.

Information above are detailed below and organized by the items described in FAA
letter.GCF

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Question 1:

“1 The petitioner should show that all practical me asures have been taken to meet the requirements of § 25.981(a)(3) for the fue l-tank structure. For the design features for which an exemption is sought, t he petitioner should show what potentially compliant design changes were exam ined, and what design changes were ruled out based on impracticality.”

IMPRACTICALITY OF 25.981(a)(3) STRUCTURAL THIRD PRO TECTIVE FEATURE

EMB-135BJ Enhanced model has included FAA Amendment 25-102 to its certification basis as a result of a major change, where an exter nal ventral fuel tank was added to
the aircraft.

Requirement §25.981(a)(3) for structural lightning protection leads to the use of three highly reliable, independent and redundant protecti ve features to prevent ignition sources. For EMB-135BJ Enhanced, modifications prop osed for the fuel tanks structure followed the same design criteria required prior to Amendment 25-102. However, they are not sufficient to comply with all scenarios of §25.981(a)(3).

During design review process, fuel tank structure h as been analyzed in order to determine if it would be possible to include one mo re protective feature, besides the
other existent ones. Below is the list of alternati ves searched for the third protective
feature:

• Anti static fuel bladder;

• Machined structural element with insert;

• Protective cover for the structural joint (besides sealant);

• One more skin layer (metal or composites);

• Sealant application over the skin surface; and

• Adhesive bonded structural elements.

Incorporation of alternatives above would involve c onsiderable design changes on the
whole structure of the fuel tanks. This would affec t considerably:

• Fuel volume: lower capacity due to accommodation o f the third protective feature;

• Maintenance: increased workload due to more parts (bladder, bonded parts, another skin layer) added inside fuel tanks;

• Repair: in the case of fuel bladder, removal and i nstallation of a new bladder would be required prior to dispatch of the aircraft ; and

• Structural Analysis: novel design.GCF

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Therefore, addition of a third protective feature t o comply with §25.981(a)(3) is impractical since it would demand a new design of t he fuel tanks with aircraft lower flight performance and greater maintenance and repair work load from the design envisioned for EMB-135BJ Enhanced model, what would make the d evelopment of this aircraft unviable, provided it would not be competitive when compared to the existent aircraft in
the market.

For EMB-135BJ Enhanced, compliance demonstration wi ll be based on the following
conditions:

- FAA/ANAC/EASA §25.581, §25.899, and §25.954 are a lready complied through
EMB-135BJ certification basis.
- FAA/ANAC §25.981(a)(3) for structural lightning p rotection: petition for exemption with execution of DEL tests and analysis according to ANM-112-08-002.

Policy Guidance developed by SAE AE-2 and EUROCAE W G-31 lightning committees regarding to FAA Policy Memo ANM 112-08-002 was use d as reference for definition of DEL tests and fault tolerance analysis for complian ce of structural lightning protection according to §25.981(a)(3).

In the next section, it will be described the proce ss for determination of structural joints to be tested and analyzed for fault tolerance. Ligh tning tests and analysis results are presented subsequently.

FAILURE CONDITIONS ASSESSMENT

For clarification purposes, all external fuel tanks are made of aluminum.

A list of all structural joints in fuel tanks was g enerated after design review analysis, covering any type of structural present in the fuel tanks.

All parts existent in each structural joint were an alyzed and they were reviewed according to their lightning zone (2A or 3).

Sealing was analyzed in the structural joints, espe cially on the fasteners heads, in each
fuel tank.GCF

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Based on the assumptions above, structural joints w ere represented in specimens for lightning tests. Typical failure modes were added t o the specimens. In order to check if the lightning protective features are independent, reliable and effective, they were adequately disabled in the specimens and tested for lightning.

TEST RESULTS

Fault Tolerant Features

Lightning tests were performed and it was verified that access door required to be modified in order to have two lightning fault toler ant features. Additional tests were performed and the access door passed with modificat ion to a bonded dome nut. There were two configurations of bonded dome nut that pas sed the test.

The new dome nuts will be incorporated to the produ ction line of EMB-135BJ Enhanced for compliance of this exemption which requires two fault tolerant features.

Non Fault Tolerant Features

In this case, analysis was performed, as described in the next question.GCF

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Question 2:

“2 Instead of compliance with the requirements of § 25.981(a)(3), the applicant must show that the design includes at lea st two independent, effective, and reliable lightning-protection featur es (or sets of features) such that fault tolerance to prevent lightning-rela ted ignition sources is provided for each area of the structural design pro posed to be exempt from the requirements of that regulation. Fault tol erance 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 featureand all other nonfault tolerant features, when their fuel-tank vapor ignition event probabilities are summed, is shown to be extremely improbable.”

NUMERICAL PROBABILITY ASSESSMENT

It was verified, through lightning tests and analys is presented above that there are two non fault tolerant features, as described below:

1. Structural element fatigue cracking 2. Fastener fatigue cracking

In this case, it is impractical to provide fault to lerance of the structural element itself, since fatigue cracking will disable any type of add itional protection feature implemented
for the structural element.

Following Policy Memo ANM 112-08-002 recommendation s, a probability analysis was performed, as illustrated by the flow chart in figu re 1, which is in accordance to Policy Guidance developed by the lightning committees SAE AE-2 and EUROCAE WG-31.

The calculation method is based on three main proba bility parameters, as described
below:

1. R L-CRITICAL : Rate of critical lightning attachment. This proba bility is related to the following parameters:
a. R LIGHTNING : Lightning strike rate
b. F ATTACH : General attachment area factor
c. F SPARK : Spark threshold factor

2. P STRUCT-n : Probability of structural failure
3. P FLAM : Fleet flammability exposureGCF

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By multiplying the main three parameters, the ignit ion rate for one failure is obtained. Total Fuel tank ignition rate is the sum of all sin gle failures.

FIGURE 1: FLOW CHART FOR PROBABILITY ANALYSIS

Analysis was performed and below are the results fo und for each fuel tank:

Wing Tank Ignition Rate: 8,54 x 10 -11
Underbelly Tank Ignition Rate: 9,79 x 10 -10
Ventral Tank Ignition Rate: 1,55 x 10 -10

The Wing and Ventral fuel tanks provided probabilit y failures lower than 1x10 -9 , which indicates that fuel vapor ignition would be extreme ly improbable to occur.

In the case of Underbelly fuel tank, it was provide d a probability failure of 0,98 x 10 -09

, being a marginal value next to the scale of 1x10 -09

.

This value is linked to the low quantity of FH accu mulated for this fuel tank compared to
the other ones.GCF

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On the other hand, it shall be noted that all exter nal fuel tanks have adopted the same structural design philosophies. Similarly, lightnin g protection of the fuel tanks have the same approach, by providing the same type of fault tolerant protection features on
them.

Therefore, the probability failure obtained for the underbelly fuel tank is acceptable, based on the analysis detailed above, and can be co nsidered as extremely improbable,

too.GCF

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Question 3:

“3 The applicant must perform an analysis to show t hat the design, manufacturing processes, and airworthiness limitati ons section of the
instructions for continued airworthiness include al l practical measures to prevent, and detect and correct, failures of struct ural lightning protection features because of manufacturing variability, agin g, wear, corrosion, and likely damage.”

“With regard to item 3, above, your petition discus ses manufacturing controls but it does not specifically address inspection of non-fault-tolerant design features. We request confirmation that any non-faul t-tolerant design features will receive 100 percent inspection to val idate that the features are present at the time of manufacture. We also req uest confirmation that the Critical Design Configuration Control Limitatio ns (CDCCLs) discussed in your petition will include periodic, i n-service inspection of all ignition-prevention features, as well as non-fault- tolerant features.”

MANUFACTURING PROCESS

Fuel tank structure assembly is manufactured based on the following SAE standards: 1. AS9100C “Quality Management Systems – Requiremen ts for Aviation, Space and Defense Organizations” 2. AS9003 “Inspection and Test Quality System” 3. AS9102A “Aerospace First Article Inspection”

It will be presented the whole production process o f the fuel tanks, in order to comprehend the existent control for mitigation of t ypical failures modes which would produce quality escapes. Every Fault Tolerant and N on Fault Tolerant Feature drilling, assembly and sealing is inspected as will be descri bed below.

Quality Management System

Quality Management System covers all stages of deve lopment and production, to achieve quality specifications and product safety, as illustrated in figure 2. The needs and opportunities for improvement and correction ar e flagged by the feedback and independent assessment of compliance with the proce dures and results are verified and guaranteed by the Quality Audit.

All actions occur in an environment created by the quality system and processes related to this system.GCF

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Integrated Development

Process

Audit Qualification people

Non Conformity Management

Corrective

and Preventive Action Quality

Product

Records

Quality

Product

Indicators Verification

Manufacturing operations, assembly and inspection Supplier

Supplier First Article Inspection

Conformity

Elaboration of the roadmap Operations

Production and Inspection

Integrated Development

Process

Audit Qualification people

Non Conformity Management

Corrective

and Preventive Action Quality

Product

Records

Quality

Product

Indicators Quality

Product

Records

Quality

Product

Indicators Verification

Manufacturing operations, assembly and inspection Supplier

Supplier First Article Inspection

Conformity

Elaboration of the roadmap Operations

Production and Inspection

FIGURE 2: QUALITY MANAGEMENT SYSTEM

Management qualification system keeps the records i n the system of the company following process steps, as: establish processes, d efine the requirements, train those
involved.

Requirements for Qualification: to be qualified in a given process, employee must meet the requirements for OJT (On the job training) and theoretical requirements.

Requirements of Theoretical Knowledge: carry theoretical training defined for a process.

Requirements for Practical Knowledge (OJT) :

The coach must record the attendance requirements f or OJT for the operators under their responsibility.

The supervisor must verify and record the attendanc e requirements for qualification of personnel under their responsibility

In the case of special procedures, the personnel mu st be checked and certified by Quality Leadership in the area. At their discretion , the Quality Leadership can applyGCF

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theoretical examinations, practical examinations or other form of verification before certifying an employee.

Employees certified in special processes, or critic al processes will receive individualized stamps from quality department.

Human resources training can be divided in parts as illustrated in figure 3. Each part is associated to a specific type of work and a set of training courses which will guarantee adequate assembly of the fuel tanks.

FIGURE 3: HUMAN RESOURCES TRAINING REQUIREMENTS

Control of Records

The following records and evidence of qualification shall be kept for each qualified employee:

- Name plate and the employee; - Identification of the process in which the employ ee is qualified; - Identification of the specific procedure; - Number stamp, if applicable; - Date of qualification and validity; - Date of commencement and completion of OJT; Drilling Countersinking Riveting

Sealing Special Sealing Structural Assembly

–

OJT Torque, Locking and Seal

SPC for assembler Drawing Reading & Interpretation

Blind Fasteners installation

120o Solid Rivet Installation

Solid Rivet Installation

Threaded Pin Installation

Basic Measurement Instruments

Reamers Edge and Pitch Distance Production / Inspection Documentation

FOE / FOD

Pneumatic Jackhammer and Drill Pistol Quality Commitment Drilling Manual Interface Sealing Sealing

– Wet / Pressurized Regions Sealing – Subassembly Test – Leakage Sealing / Bonding – AerodynamicGCF

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- Employee experience in the process on the date of qualification, including the period of OJT (years and months); - Identification of the coach responsible for OJT; - Identification of the immediate superior; - Identification of quality leadership in the area (only for special cases); - Records and other evidence required by the specia l procedure. - The records and evidence should be kept in the co mpany system.

Records are kept to demonstrate compliance with spe cific requirements and effective operation of the management system applied in the o perational units of the
manufacturer.

Sheet Compliance – FIC

It is a printed document, which allows recording of values, signatures and seal impressions, for evidence of production process ope rations. When all related documentation is closed, it is filed to preserve da ta traceability.

Rework Order

Conformity end of the document is executed by membe rs of the Product Quality.

Production Process Verification

SAE AS9102A is the reference document for initial p roduction of any new product or modification proposed for EMB-135BJ Enhanced.

FAI - First Article Inspection

Inspection process complete physical and functional , independent and documented to verify that prescribed production methods produce a n acceptable item, as specified by engineering drawings, planning, purchase order, eng ineering specifications and / or
other relevant documents.

FAI is a process that composes actions regarding "A pproval of Initial Production Process", in order to confirm the adequacy of the p rocess to produce conforming items
or detect deficiencies to be remedied before the st art of serial production.

Application to items manufactured at EMBRAER

FAI should be applied in 100% of standard items man ufactured and assembled internally.GCF

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Reapplication of the FAI for validation of design, process and tooling changes

Reapplication of the FAI should be analyzed under t he following conditions:

1. Modification of the sources of manufacturing pro cesses, inspection methods, location of manufacturing, tooling or material with the potential to affect assembly, form, function and producibility. 2. Changes in the numerical control program or tran sition to other media with the potential to affect assembly, form or function. 3. Natural occurrence or event caused by human inte rference that may adversely affect the manufacturing process. 4. Stop production for two years or as specified by the customer.

Control of Production

Preparation for drilling (SETUP)

Measurement values of the holes are recorded in a s pecimen, before the start of drilling,
for verification and validation of the tool.

Items to check in the production instructions

1. Deburr holes after final drilling. 2. Holes for pins, as specific diameter (checked at determined intervals during drilling execution), roughness, and step away from the edge. 3. Installation of the pins, as: correct grasp, set tling of the head (head, collar, washer and nut) and protection of the collar. 4. Verify countersink for conventional rivets and p ins, as the diameter of the countersunk, depth, radius of agreement (settlement ) and finishing. 5. Holes for rivets as to: specific diameter, edge distance, distance between holes and finishing. 6. Rivets, as to: snap rivet head, conformation of the head (height x diameter),
cracks and marks

To avoid misalignment of the holes, during drilling process a device is used to keep the tool at 90 degrees.

Sealing

Before sealing, employee makes a visual inspection so that installation is clean and there are no foreign objects in the region. Then, s ealing process is initiated and performed by another employee (sealant specialist). This specialist will perform another visual inspection to ensure that no particle or for eign object remained in the area.GCF

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Sealant application is verified for:

• Uniformity of the layer (interface)

• Heals

• Bubbles

• Retraction

Special qualification is required for sealing.

As detailed above in this section, typical modes of failures that could become quality escapes are adequately mitigated. When this type of non conformity is found, corrective actions are generated, as detailed in the next sect ion, which eliminates the possibility to
have latent failures in the fuel tank.

Corrective and Preventive Actions

There is a system which implements corrective and p reventive actions, with emphasis on the production process, including at the stage o f development in order to eliminate
the root causes of nonconformities identified on th e product or process, and preventing its recurrence (or occurrence).

CAT (Corrective Action Team)

Team of corrective and preventive action, under the coordination of quality, composed of representatives of different areas of the compan y, responsible for root cause analysis and definition of plans for corrective and preventi ve actions relating to the production

process.

Stages of Process of Preventive and Corrective Acti ons

Definition Describe the nonconformance, providing in detail th e necessary information for the characterization of the problem.

Analysis Record and analysis of the data for identifying the root cause of the problem (Ishikawa, correlation analysis, hypothesis testing, Kepner Tr egoe, etc). Highlight the root cause.

Containment and Action Plan:GCF

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Containment: blocking action of non-compliance to a void or minimize the impact of a new occurrence and facilitate the continuity of the production process until the completion of corrective action.

Research: actions that will assist in the identific ation or confirmation of the root cause of the problem.

Plan of Action: actions set for elimination of the root cause of the problem.

Similarity Analysis: to verify if non-conformity af fects pieces or similar processes.

Verification of effectiveness: actions of verificat ion of effectiveness of problem elimination, or improve of process; with their evid ences.

In order to guarantee that correction was performed , representative information can be used as evidence, for example: aircraft or sequence of operations observed during a representative period of time.

Supplier

Supplier Development

The management strategy for the development of mate rial and supplier based on the application of different management actions, in typ e, intensity and frequency, depending on the classification of material and supplier that is established from the criticality of the product versus risk of the supplier.

Performance Management and Corrective Action / Prev entive of Suppliers

There is a documentation which formalizes and sends corrective or preventive action to non-conformities detected in all phases of the prod uct manufacturing.

Corrective Action: Action to eliminate the cause of non-compliance identified.
Preventive action: Action to eliminate the cause of a potential non-conformity.

Audit

Internal AuditGCF

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Audit quality is carried out by the Corporate Quali ty (Auditing of Quality Management System) and the Product Quality Audit (Quality Audi ting Product) as applicable to each Operating Unit and strategically defined by EMBRAER

.

The audits of the various methods are conducted as appropriate, depending on definitions of strategic implementation of manageme nt systems in Operational Units.

The audits may be planned and implemented in an int egrated manner, considering all Management Systems applicable to Operational Units.

Audit of Quality System in Supplier

There is a systematic, independent and documented a udit process to obtain objective evaluation of the evidence of the Quality System im plemented by the suppliers in relation to the requirements specified in the proce dures.

MAINTENANCE

Embraer ensures that all practical measures to prev ent, detect and correct failures of structural lightning protection features due to man ufacturing variability, aging, wear, corrosion and possible damage are adopted based on the Structural Inspection Requirements (Section 4) , Corrosion and Prevention Control Program – CPCP (Section 5) and Zonal Inspection Requirements (Section 6) of the MPG-1483/SMRD-1533, developed under Air Transportation Association’s Ma intenance Program Development Document MSG-3 Rev. 2002.1. This process assures 10 0% accountability for all Structural Significant Items (SSIs). The aircraft m aintenance manual presents internal general visual inspections for wing tanks, forward tanks, and ventral tank to comply with the aforementioned MPG-1483/SMRD-1533 requirements.

Embraer also ensures that all the CDCCLs generated during this analysis will be included in the second Appendix of MPG-1483/SMRD-15 33 as an airworthiness limitation as well as in all the procedures related to any appropriate inspection to assure the reliability of the applicable lightning protect ion features, checking any fault tolerant and non fault tolerant features. Additionally, a ne w procedure in the AMM (AMM 51-12- 00/601) requiring the inspection of structural elem ents (for loose or missing structural items, nicks, cracks, dents, erosion, corrosion, de formation, deteriorated protective treatment, foreign object, and integrity of the sea lant) has been developed and will be referred to in the procedures for integral fuel tan k access panel removal/installation to be carried out whenever an integral fuel tank acces s panel is open. This Structural Lightning Protection inspection must be done in the associated integral fuel tank access panel removed from the internal area.