43318 Federal Register / Vol. 79, No. 143 / Friday, July 25, 2014 / Proposed Rules 

§ 615.5180 [Amended] 

■ 12. Section 615.5180 paragraph (c)(3) 

is amended by removing the reference 

‘‘§ 615.5133(f)(4)’’ and adding in its 

place, the reference ‘‘§ 615.5133(h)(4)’’. 

Dated: July 21, 2014. 

Dale L. Aultman, 

Secretary, Farm Credit Administration Board. 

[FR Doc. 2014–17493 Filed 7–24–14; 8:45 am] 

BILLING CODE 6705–01–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No. FAA–2014–0383; Notice No. 25– 

14–05–SC] 

Special Conditions: Bombardier 

Aerospace, Models BD–500–1A10 and 

BD–500–1A11 Series Airplanes; 

Alternate Fuel Tank Structural 

Lightning Protection Requirements 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed special 

conditions. 

SUMMARY: This action proposes special 

conditions for the Bombardier 

Aerospace Models BD–500–1A10 and 

BD–500–1A11 series airplanes. These 

airplanes will have a novel or unusual 

design feature that will incorporate a 

nitrogen generation system (NGS) for all 

fuel tanks that actively reduce 

flammability exposure within the fuel 

tanks significantly below that required 

by the fuel tank flammability 

regulations. Among other benefits, the 

NGS significantly reduces the potential 

for fuel vapor ignition caused by 

lightning strikes. The applicable 

airworthiness regulations do not contain 

adequate or appropriate safety standards 

for this design feature. These proposed 

special conditions contain the 

additional safety standards that the 

Administrator considers necessary to 

establish a level of safety equivalent to 

that established by the existing 

airworthiness standards. 

DATES: Send your comments on or 

before September 8, 2014. 

ADDRESSES: Send comments identified 

by docket number FAA–2014–0383 

using any of the following methods: 

• Federal eRegulations Portal: Go to 

http://www.regulations.gov/ and follow 

the online instructions for sending your 

comments electronically. 

• Mail: Send comments to Docket 

Operations, M–30, U.S. Department of 

Transportation (DOT), 1200 New Jersey 

Avenue SE., Room W12–140, West 

Building Ground Floor, Washington, 

DC, 20590–0001. 

• Hand Delivery or Courier: Take 

comments to Docket Operations in 

Room W12–140 of the West Building 

Ground Floor at 1200 New Jersey 

Avenue SE., Washington, DC, between 9 

a.m. and 5 p.m., Monday through 

Friday, except federal holidays. 

• Fax: Fax comments to Docket 

Operations at 202–493–2251. 

Privacy: The FAA will post all 

comments it receives, without change, 

to http://www.regulations.gov/, 

including any personal information the 

commenter provides. Using the search 

function of the docket Web site, anyone 

can find and read the electronic form of 

all comments received into any FAA 

docket, including the name of the 

individual sending the comment (or 

signing the comment for an association, 

business, labor union, etc.). DOT’s 

complete Privacy Act Statement can be 

found in the Federal Register published 

on April 11, 2000 (65 FR 19477–19478), 

as well as at http://DocketsInfo 

.dot.gov/. 

Docket: Background documents or 

comments received may be read at 

http://www.regulations.gov/ at any time. 

Follow the online instructions for 

accessing the docket or go to the Docket 

Operations in Room W12–140 of the 

West Building Ground Floor at 1200 

New Jersey Avenue SE., Washington, 

DC, between 9 a.m. and 5 p.m., Monday 

through Friday, except federal holidays. 

FOR FURTHER INFORMATION CONTACT: 

Margaret Langsted, FAA, Propulsion 

and Mechanical Systems Branch, ANM– 

112, Transport Airplane Directorate, 

Aircraft Certification Service, 1601 Lind 

Avenue SW., Renton, Washington, 

98057–3356; telephone 425–227–2677; 

facsimile 425–227–1149. 

SUPPLEMENTARY INFORMATION: 

Comments Invited 

We invite interested people to take 

part in this rulemaking by sending 

written comments, data, or views. The 

most helpful comments reference a 

specific portion of the special 

conditions, explain the reason for any 

recommended change, and include 

supporting data. 

We will consider all comments we 

receive on or before the closing date for 

comments. We may change these special 

conditions based on the comments we 

receive. 

Background 

On December 10, 2009, Bombardier 

Aerospace applied for a type certificate 

for their new Models BD–500–1A10 and 

BD–500–1A11 series airplanes (hereafter 

collectively referred to as ‘‘CSeries’’). 

The CSeries airplanes are swept-wing 

monoplanes with a composite wing fuel 

tank structure and an aluminum alloy 

fuselage sized for 5-abreast seating. 

Passenger capacity is designated as 110 

for the Model BD–500–1A10 and 125 for 

the Model BD–500–1A11. Maximum 

takeoff weight is 131,000 pounds for the 

Model BD–500–1A10 and 144,000 

pounds for the Model BD–500–1A11. 

Type Certification Basis 

Under the provisions of Title 14, Code 

of Federal Regulations (14 CFR) 21.17, 

Bombardier Aerospace must show that 

the CSeries airplanes meet the 

applicable provisions of part 25 as 

amended by Amendments 25–1 through 

25–129. 

If the Administrator finds that the 

applicable airworthiness regulations 

(i.e., 14 CFR part 25) do not contain 

adequate or appropriate safety standards 

for the CSeries airplanes because of a 

novel or unusual design feature, special 

conditions are prescribed under the 

provisions of § 21.16. 

Special conditions are initially 

applicable to the model for which they 

are issued. Should the type certificate 

for that model be amended later to 

include any other model that 

incorporates the same or similar novel 

or unusual design feature, the special 

conditions would also apply to the other 

model under § 21.101. 

In addition to the applicable 

airworthiness regulations and special 

conditions, the CSeries airplanes must 

comply with the fuel vent and exhaust 

emission requirements of 14 CFR part 

34 and the noise certification 

requirements of 14 CFR part 36, and the 

FAA must issue a finding of regulatory 

adequacy under section 611 of Public 

Law 92–574, the ‘‘Noise Control Act of 

1972.’’ 

The FAA issues special conditions, as 

defined in 14 CFR 11.19, in accordance 

with § 11.38, and they become part of 

the type certification basis under 

§ 21.17. 

Novel or Unusual Design Features 

The CSeries airplanes will incorporate 

the following novel or unusual design 

features: A fuel tank nitrogen generation 

system (NGS) that is intended to control 

fuel tank flammability for all fuel tanks. 

This NGS is designed to provide a level 

of performance that applies the more 

stringent standard for warm day 

flammability performance applicable to 

normally emptied tanks within the 

fuselage contour from § 25.981(b) and 

appendix M to part 25 to all fuel tanks 

of the CSeries airplanes. This high level 

of NGS performance for all fuel tanks is 


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a novel or unusual design feature 

compared to the state of technology 

envisioned in the airworthiness 

standards for transport category 

airplanes. 

Discussion 

The certification basis of the CSeries 

airplanes includes § 25.981, as amended 

by Amendment 25–125, as required by 

14 CFR 26.37. This amendment includes 

the ignition prevention requirements in 

§ 25.981(a), as amended by Amendment 

25–102, and it includes revised 

flammability limits for all fuel tanks and 

new specific limitations on flammability 

for all fuel tanks as defined in 

§ 25.981(b), as amended by Amendment 

25–125. 

Ignition Source Prevention 

Section 25.981(a)(3) requires 

applicants to show that an ignition 

source in the fuel tank system could not 

result from any single failure, from any 

single failure in combination with any 

latent failure condition not shown to be 

extremely remote, or from any 

combination of failures not shown to be 

extremely improbable. This requirement 

was originally adopted in Amendment 

25–102, and it requires the assumption 

that the fuel tanks are always flammable 

when showing that the probability of an 

ignition source being present is 

extremely remote. (Amendment 25–102 

included § 25.981(c) that required 

minimizing fuel tank flammability, and 

this was defined in the preamble as 

being equivalent to unheated aluminum 

fuel tanks located in the wing.) This 

requirement defines three types of 

scenarios that must be addressed in 

order to show compliance with 

§ 25.981(a)(3). The first scenario is that 

any single failure, regardless of the 

probability of occurrence of the failure, 

must not cause an ignition source. The 

second scenario is that any single 

failure, regardless of the probability of 

occurrence, in combination with any 

latent failure condition not shown to be 

at least extremely remote, must not 

cause an ignition source. The third 

scenario is that any combination of 

failures not shown to be extremely 

improbable must not cause an ignition 

source. Demonstration of compliance 

with this requirement would typically 

require a structured, quantitative safety 

analysis. Design areas that have latent 

failure conditions typically would be 

driven by these requirements to have 

multiple fault tolerance, or ‘‘triple 

redundancy.’’ This means that ignition 

sources are still prevented even after 

two independent failures. 

Flammability Limits 

Section 25.981(b) states that no fuel 

tank fleet average flammability exposure 

may exceed 3 percent of the 

flammability exposure evaluation time 

calculated using the method in part 25, 

Appendix N, or the fleet average 

flammability of a fuel tank within the 

wing of the airplane being evaluated, 

whichever is greater. If the wing is not 

a conventional unheated aluminum 

wing, the analysis must be based on an 

assumed equivalent conventional 

construction unheated aluminum wing. 

In addition, for fuel tanks that are 

normally emptied during operation and 

that have any part of the tank located 

within the fuselage contour, the fleet 

average flammability for warm days 

(above 80 °F) must be limited to 3 

percent as calculated using the method 

in part 25, Appendix M. 

Application of Existing Regulations 

Inappropriate Due to Impracticality 

Since the issuance of § 25.981(a)(3), as 

amended by Amendment 25–102, the 

FAA has conducted certification 

projects in which applicants found it 

impractical to meet the requirements of 

that regulation for some areas of 

lightning protection for fuel tank 

structure. Partial exemptions were 

issued for these projects. These same 

difficulties exist for the CSeries project. 

The difficulty of designing multiplefault-tolerant structure, and the 

difficulty of detecting failures of hidden 

structural design features in general, 

makes compliance with § 25.981(a)(3) 

uniquely challenging and impractical 

for certain aspects of the electrical 

bonding of structural elements. Such 

bonding is needed to prevent 

occurrence of fuel tank ignition sources 

from lightning strikes. The effectiveness 

and fault tolerance of electrical bonding 

features for structural joints and 

fasteners is partially dependent on 

design features that cannot be 

effectively inspected or tested after 

assembly without damaging the 

structure, joint, or fastener. Examples of 

such features include a required 

interference fit between the shank of a 

fastener and the hole in which the 

fastener is installed, metal foil or mesh 

imbedded in composite material, a 

required clamping force provided by a 

fastener to pull two structural parts 

together, and a required faying surface 

bond between the flush surfaces of 

adjacent pieces of structural material 

such as in a wing skin joint or a 

mounting bracket installation. In 

addition, other features that can be 

physically inspected or tested may be 

located within the fuel tanks; therefore, 

it is not practical to inspect for failures 

of those features at short intervals. 

Examples of such failures include 

separation or loosening of cap seals over 

fastener ends and actual structural 

failures of internal fasteners. This 

inability to practically detect 

manufacturing errors and failures of 

structural design features critical to 

lightning protection results in degraded 

conditions that occur and remain in 

place for a very long time, possibly for 

the remaining life of the airplane. 

Accounting for such long failure 

latency periods in the system safety 

analysis required by § 25.981(a)(3) 

would require multiple fault tolerance 

in the structural lightning protection 

design. As part of the design 

development activity for the CSeries, 

Bombardier has examined possible 

design provisions to provide multiple 

fault tolerance in the structural design 

to prevent ignition sources from 

occurring in the event of lightning 

attachment to the airplane in critical 

locations. Bombardier has concluded 

from this examination that providing 

multiple fault tolerance for some 

structural elements is not practical. 

Bombardier has also identified some 

areas of the CSeries design where it is 

impractical to provide even single fault 

tolerance in the structural design to 

prevent ignition sources from occurring 

in the event of lightning attachment 

after a single failure. The FAA has 

reviewed this examination with 

Bombardier in detail and has agreed that 

providing fault tolerance beyond that in 

the proposed CSeries design for these 

areas would be impractical. 

As a result of the CSeries and other 

certifications projects, the FAA has now 

determined that compliance with 

§ 25.981(a)(3) is impractical for some 

areas of lightning protection for fuel 

tank structure, and that application of 

§ 25.981(a)(3) to those design areas is 

therefore inappropriate. The FAA plans 

further rulemaking to revise 

§ 25.981(a)(3). As appropriate, the FAA 

plans to issue special conditions or 

exemptions, for certification projects 

progressing before the revision is 

complete. This is discussed in FAA 

Memorandum ANM–112–08–002, 

Policy on Issuance of Special Conditions 

and Exemptions Related to Lightning 

Protection of Fuel Tank Structure, dated 

May 26, 2009. 

Application of Existing Regulations 

Inappropriate Due to Compensating 

Feature That Provides Equivalent Level 

of Safety 

Section 25.981(b) sets specific 

standards for fuel tank flammability as 

discussed above under ‘‘Flammability 


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Limits.’’ Under that regulation, the fleet 

average flammability exposure of all 

fuel tanks on the CSeries airplanes may 

not exceed 3 percent of the flammability 

exposure evaluation time calculated 

using the method in part 25, Appendix 

N, or the fleet average flammability of a 

wing main tank within an equivalent 

construction conventional unheated 

aluminum wing fuel tank, whichever is 

greater. The typical fleet average fuel 

tank flammability of fuel tanks located 

in the wing ranges between 1 and 5 

percent. If it is assumed that a CSeries 

equivalent conventional unheated 

aluminum wing fuel tank would not 

exceed a fleet average flammability time 

of 3 percent, the actual composite 

airplane wing fuel tank design would be 

required to comply with the 3 percent 

fleet average flammability standard, and 

therefore a means to reduce the 

flammability to 3 percent would be 

required. However, the proposed 

CSeries design includes NGS for all fuel 

tanks that will also be shown to meet 

the additional, more stringent warm day 

average flammability standard in part 

25, Appendix M, which is only required 

for normally emptied fuel tanks with 

some part of the tank within the 

fuselage contour. Fuel tanks that meet 

this requirement typically have average 

fuel tank flammability levels well below 

the required 3 percent. 

Since the proposed NGS for all fuel 

tanks on the CSeries provides 

performance that meets part 25, 

Appendix M, the FAA has determined 

that the risk reduction provided by this 

additional performance will provide 

compensation for some relief from the 

ignition prevention requirements of 

§ 25.981(a)(3) while still establishing a 

level of safety equivalent to that 

established in the regulations. 

In determining the appropriate 

amount of relief from the ignition 

prevention requirements of § 25.981(a), 

the FAA considered the original overall 

intent of Amendment 25–102, which 

was to ensure the prevention of 

catastrophic events due to fuel tank 

vapor explosion. These proposed 

special conditions are intended to 

achieve that objective through a 

prescriptive requirement that fault 

tolerance (with respect to the creation of 

an ignition source) be provided for all 

structural lightning protection design 

features where providing such fault 

tolerance is practical, and through a 

performance-based standard for the risk 

due to any single failure vulnerability 

that exists in the design. In addition, for 

any structural lightning protection 

design features for which Bombardier 

shows that providing fault tolerance is 

impractical, these proposed special 

conditions would require Bombardier to 

show that a fuel tank vapor ignition 

event due to the summed risk of all nonfault-tolerant design features is 

extremely improbable. Bombardier 

would be required to show that this 

safety objective is met by the proposed 

design using a structured system safety 

assessment similar to that currently 

used for demonstrating compliance with 

§§ 25.901 and 25.1309. 

Given these novel or unusual design 

features, and the compliance challenges 

noted earlier in this document, the FAA 

has determined that application of 

§ 25.981(a)(3) is inappropriate in that it 

is neither practical nor necessary to 

apply the ignition source prevention 

provisions of § 25.981(a)(3) to the 

specific fuel tank structural lightning 

protection features of the Bombardier 

CSeries airplanes. However, without the 

§ 25.981(a)(3) provisions, the remaining 

applicable regulations in the CSeries 

certification basis would be inadequate 

to set an appropriate standard for fuel 

tank ignition prevention. Therefore, in 

accordance with provisions of § 21.16, 

the FAA has determined that, instead of 

§ 25.981(a)(3), alternative fuel tank 

structural lightning protection 

requirements be applied to fuel tank 

lightning protection features that are 

integral to the airframe structure of the 

CSeries airplanes. These proposed 

alternative requirements are intended to 

provide the level of safety intended by 

§ 25.981(a)(3), based on our recognition, 

as discussed above, that a highly 

effective NGS for the fuel tanks makes 

it unnecessary to assume that the fuel 

tank is always flammable. As discussed 

previously, the assumption that the fuel 

tanks are always flammable was 

required when demonstrating 

compliance to the ignition prevention 

requirements of § 25.981(a)(3). 

One resulting difference between 

these proposed special conditions and 

the § 25.981(a)(3) provisions they are 

meant to replace is the outcome being 

prevented—fuel vapor ignition versus 

an ignition source. These proposed 

special conditions acknowledge that the 

application of fuel tank flammability 

performance standards will reduce fuel 

tank flammability to an extent that it is 

appropriate to consider the beneficial 

effects of flammability reduction when 

considering design areas where it is 

impractical to comply with 

§ 25.981(a)(3). 

One of the core requirements of these 

proposed special conditions is a 

prescriptive requirement that structural 

lightning protection design features 

must be fault tolerant. (An exception 

wherein Bombardier can show that 

providing fault tolerance is impractical, 

and associated requirements, is 

discussed below.) The other core 

requirement is that Bombardier must 

show that the design, manufacturing 

processes, and Airworthiness 

Limitations section of the Instructions 

for Continued Airworthiness include all 

practical measures to prevent, and 

detect and correct, failures of structural 

lightning protection features due to 

manufacturing variability, aging, wear, 

corrosion, and likely damage. The FAA 

has determined that, if these core 

requirements are met, a fuel tank vapor 

ignition event due to lightning is not 

anticipated to occur in the life of the 

airplane fleet. This conclusion is based 

on the fact that a critical lightning strike 

to any given airplane is itself a remote 

event, and on the fact that fuel tanks 

must be shown to be flammable for only 

a relatively small portion of the fleet 

operational life. 

For any non-fault-tolerant features 

proposed in the design, Bombardier 

must show that eliminating these 

features or making them fault tolerant is 

impractical. The requirements and 

considerations for showing it is 

impractical to provide fault tolerance 

are described in FAA Memorandum 

ANM–112–08–002. This requirement is 

intended to minimize the number of 

non-fault tolerant features in the design. 

For areas of the design where 

Bombardier shows that providing fault 

tolerant structural lightning protection 

features is impractical, non-faulttolerant features will be allowed 

provided Bombardier can show that a 

fuel tank vapor ignition event due to the 

non-fault-tolerant features is extremely 

improbable when the sum of 

probabilities of those events due to all 

non-fault-tolerant features is considered. 

Bombardier will be required to submit 

a structured, quantitative assessment of 

fleet average risk for a fuel tank vapor 

ignition event due to all non-faulttolerant design features included in the 

design. This will require determination 

of the number of non-fault tolerant 

design features, estimates of the 

probability of the failure of each nonfault-tolerant design feature, and 

estimates of the exposure time for those 

failures. This analysis must include 

failures due to manufacturing 

variability, aging, wear, corrosion, and 

likely damage. 

It is acceptable to consider the 

probability of fuel tank flammability, 

the probability of a lightning strike to 

the airplane, the probability of a 

lightning strike to specific zones of the 

airplane (for example, Zone 2 behind 

the nacelle, but not a specific location 

or feature), and a distribution of 

lightning strike amplitude in performing 


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the assessment provided the associated 

assumptions are acceptable to the FAA. 

The analysis must account for any 

dependencies among these factors, if 

they are used. The assessment must also 

account for operation with inoperative 

features and systems, including any 

proposed or anticipated dispatch relief. 

This risk assessment requirement is 

intended to ensure that an acceptable 

level of safety is provided given the 

non-fault-tolerant features in the 

proposed design. 

Part 25, Appendix N, as adopted in 

Amendment 25–125, in conjunction 

with these proposed special conditions, 

constitutes the standard for how to 

determine flammability probability. In 

performing the safety analysis required 

by these special conditions, relevant 

§ 25.981(a)(3) compliance guidance is 

still applicable. Appropriate credit for 

the conditional probability of 

environmental or operational conditions 

occurring is normally limited to those 

provisions involving multiple failures, 

and this type of credit is not normally 

allowed in evaluation of single failures. 

However, these special conditions 

would allow consideration of the 

probability of occurrence of lightning 

attachment and flammable conditions 

when assessing the probability of 

structural failures resulting in a fuel 

tank vapor ignition event. 

The FAA understands that lightning 

protection safety for airplane structure 

is inherently different from lightning 

protection for systems. We intend to 

apply these proposed special conditions 

only to structural lightning protection 

features of fuel systems. We do not 

intend to apply the alternative standards 

used under these proposed special 

conditions to other areas of the airplane 

design evaluation. 

Requirements Provide Equivalent Level 

of Safety 

In recognition of the unusual design 

feature discussed above, and the 

impracticality of requiring multiple 

fault tolerance for lightning protection 

of certain aspects of fuel tank structure, 

the FAA has determined that a level of 

safety that is equivalent to direct 

compliance with § 25.981(a)(3) will be 

achieved for the CSeries by applying 

these proposed requirements. The FAA 

considers that, instead of only 

concentrating on fault tolerance for 

ignition source prevention, significantly 

reducing fuel tank flammability 

exposure in addition to preventing 

ignition sources is a better approach to 

lightning protection for the fuel tanks. 

In addition, the level of average fuel 

tank flammability achieved by 

compliance with these proposed special 

conditions is low enough that it is not 

appropriate or accurate to assume in a 

safety analysis that the fuel tanks may 

always be flammable. 

Section 25.981(b), as amended by 

Amendment 25–125, sets limits on the 

allowable fuel tank flammability for the 

CSeries airplanes. Paragraph 2(a) of 

these proposed special conditions 

applies the more stringent standard for 

warm day flammability performance 

applicable to normally emptied tanks 

within the fuselage contour from 

§ 25.981(b) and part 25, Appendix M, to 

all of the fuel tanks of the CSeries 

airplanes. 

Because of the more stringent fuel 

tank flammability requirements in these 

proposed special conditions, and 

because the flammability state of a fuel 

tank is independent of the various 

failures of structural elements that could 

lead to an ignition source in the event 

of lightning attachment, the FAA has 

agreed that it is appropriate in this case 

to allow treatment of flammability as an 

independent factor in the safety 

analysis. The positive control of 

flammability and the lower flammability 

that is required by these proposed 

special conditions exceeds the 

minimum requirements of § 25.981(b). 

This offsets a reduction of the stringent 

standard for ignition source prevention 

in § 25.981(a)(3), which assumes that 

the fuel tank is flammable at all times. 

Given the stringent requirements for 

fuel tank flammability, the fuel vapor 

ignition prevention and the ignition 

source prevention requirements in these 

proposed special conditions will 

prevent ‘‘. . . catastrophic failure . . . 

due to ignition of fuel or vapors’’ as 

stated in § 25.981(a). Thus, the overall 

level of safety achieved by these 

proposed special conditions is 

considered equivalent to that which 

would be required by compliance with 

§ 25.981(a)(3) and (b). 

Applicability 

As discussed above, these special 

conditions are applicable to the Models 

BD–500–1A10 and BD–500–1A11 series 

airplanes. Should Bombardier 

Aerospace apply at a later date for a 

change to the type certificate to include 

another model incorporating the same 

novel or unusual design feature, the 

special conditions would apply to that 

model as well. 

Conclusion 

This action affects only certain novel 

or unusual design features on two 

model series of airplanes. It is not a rule 

of general applicability. 

List of Subjects in 14 CFR Part 25 

Aircraft, Aviation safety, Reporting 

and recordkeeping requirements. 

The authority citation for these 

special conditions is as follows: 

Authority: 49 U.S.C. 106(g), 40113, 44701, 

44702, 44704. 

The Proposed Special Conditions 

Accordingly, the Federal Aviation 

Administration (FAA) proposes the 

following special conditions as part of 

the type certification basis for 

Bombardier Aerospace Models BD–500– 

1A10 and BD–500–1A11 series 

airplanes. 

Alternate Fuel Tank Structural 

Lightning Protection Requirements 

1. Definitions 

Most of the terms used in these 

proposed special conditions either have 

the common dictionary meaning or are 

defined in Advisory Circular 25.1309– 

1A, System Design and Analysis, dated 

June 21, 1988. The following definitions 

are the only terms intended to have a 

specialized meaning when used in these 

proposed special conditions: 

(a) Basic Airframe Structure. Includes 

design elements such as structural 

members, structural joint features, and 

fastener systems including airplane 

skins, ribs, spars, stringers, etc., and 

associated fasteners, joints, coatings, 

and sealant. Basic airframe structure 

may also include those structural 

elements that are expected to be 

removed for maintenance, such as 

exterior fuel tank access panels and 

fairing attachment features, provided 

maintenance errors that could 

compromise associated lightning 

protection features would be evident 

upon an exterior preflight inspection of 

the airplane and would be corrected 

prior to flight. 

(b) Permanent Systems Supporting 

Structure. Includes static, permanently 

attached structural parts (such as 

brackets) that are used to support 

system elements. It does not include any 

part intended to be removed, or any 

joint intended to be separated, to 

maintain or replace system elements or 

other parts, unless that part removal or 

joint separation is accepted by the FAA 

as being extremely remote. 

(c) Manufacturing Variability. 

Includes tolerances and variability 

allowed by the design and production 

specifications as well as anticipated 

errors or escapes from the 

manufacturing and inspection 

processes. 

(d) Extremely Remote. Conditions that 

are not anticipated to occur to each 

airplane during its total life, but which 


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may occur a few times when 

considering the total operational life of 

all airplanes of one type. Extremely 

remote conditions are those having an 

average probability per flight hour on 

the order of 1 × 10¥7 or less, but greater 

than on the order of 1 × 10¥9. 

(e) Extremely Improbable. Conditions 

that are so unlikely that they are not 

anticipated to occur during the entire 

operational life of all airplanes of one 

type. Extremely improbable conditions 

are those having an average probability 

per flight hour of the order of 1 × 10¥9

or less. 

2. Alternative Fuel Tank Structural 

Lightning Protection Requirements 

For lightning protection features that 

are integral to fuel tank basic airframe 

structure or permanent systems 

supporting structure, as defined in 

Special Condition No. 1, ‘‘Definitions,’’ 

for which Bombardier shows and the 

FAA finds compliance with 

§ 25.981(a)(3) to be impractical, the 

following requirements may be applied 

in lieu of the requirements of 

§ 25.981(a)(3): 

(a) Bombardier must show that the 

airplane design meets the requirements 

of part 25, appendix M, as amended by 

Amendment 25–125, for all fuel tanks 

installed on the airplane. 

(b) Bombardier 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 provided for each area of the 

structural design proposed to be shown 

compliant with these special conditions 

in lieu of compliance with the 

requirements of § 25.981(a)(3). Fault 

tolerance is not required for any specific 

design feature if: 

(1) For that feature, providing fault 

tolerance is shown to be impractical, 

and 

(2) Fuel tank vapor ignition due to 

that feature and all other non-faulttolerant features, when their fuel tank 

vapor ignition event probabilities are 

summed, is shown to be extremely 

improbable. 

(c) Bombardier must perform an 

analysis to show that the design, 

manufacturing processes, and the 

airworthiness limitations section of the 

instructions for continued airworthiness 

include all practical measures to 

prevent, and detect and correct, failures 

of structural lightning protection 

features due to manufacturing 

variability, aging, wear, corrosion, and 

likely damage. 

Issued in Renton, Washington, on June 6, 

2014. 

Jeffrey E. Duven, 

Manager, Transport Airplane Directorate, 

Aircraft Certification Service. 

[FR Doc. 2014–17517 Filed 7–24–14; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2014–0483; Directorate 

Identifier 2014–NM–082–AD] 

RIN 2120–AA64 

Airworthiness Directives; Bombardier, 

Inc. Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed rulemaking 

(NPRM). 

SUMMARY: We propose to supersede 

Airworthiness Directive (AD) 2013–16– 

08 for certain Bombardier, Inc. Model 

CL–600–2C10 (Regional Jet Series 700, 

701, & 702) airplanes, Model CL–600– 

2D15 (Regional Jet Series 705) airplanes, 

and Model CL–600–2D24 (Regional Jet 

Series 900) airplanes. Since we issued 

AD 2013–16–08, we have determined 

that a certain part was incorrectly 

identified in a certain section of that 

AD. This proposed AD would continue 

to require inspection of the MLG 

retraction actuator components; 

corrective actions if necessary; and, for 

certain retraction actuators, installation 

of a new jam nut. We are proposing this 

AD to prevent disconnection of the MLG 

retraction actuator, which could result 

in extension of the MLG without 

damping, and consequent structural 

damage and collapse of the MLG during 

landing. 

DATES: We must receive comments on 

this proposed AD by September 8, 2014. 

ADDRESSES: You may send comments by 

any of the following methods: 

• Federal eRulemaking Portal: Go to 

http://www.regulations.gov. Follow the 

instructions for submitting comments. 

• Fax: 202–493–2251. 

• Mail: U.S. Department of 

Transportation, Docket Operations, 

M–30, West Building Ground Floor, 

Room W12–140, 1200 New Jersey 

Avenue SE., Washington, DC 20590. 

• Hand Delivery: U.S. Department of 

Transportation, Docket Operations, 

M–30, West Building Ground Floor, 

Room W12–140, 1200 New Jersey 

Avenue SE., Washington, DC, between 9 

a.m. and 5 p.m., Monday through 

Friday, except Federal holidays. 

For Bombardier service information 

identified in this proposed AD, contact 

Bombardier, Inc., 400 Coˆte-Vertu Road 

West, Dorval, Que ́bec H4S 1Y9, Canada; 

telephone 514–855–5000; fax 514–855– 

7401; email thd.crj@

aero.bombardier.com; Internet http://

www.bombardier.com. 

For Goodrich service information 

identified in this proposed AD, contact 

Goodrich Corporation, Landing Gear, 

1400 South Service Road, West Oakville 

L6L 5Y7, Ontario, Canada; telephone 

905–825–1568; email jean.breed@

goodrich.com; Internet http://

www.goodrich.com/TechPubs. 

You may view this referenced service 

information at the FAA, Transport 

Airplane Directorate, 1601 Lind Avenue 

SW., Renton, WA. For information on 

the availability of this material at the 

FAA, call 425–227–1221. 

Examining the AD Docket 

You may examine the AD docket on 

the Internet at http://

www.regulations.gov by searching for 

and locating Docket No. FAA–2014– 

0483; or in person at the Docket 

Management Facility between 9 a.m. 

and 5 p.m., Monday through Friday, 

except Federal holidays. The AD docket 

contains this proposed AD, the 

regulatory evaluation, any comments 

received, and other information. The 

street address for the Docket Operations 

office (telephone 800–647–5527) is in 

the ADDRESSES section. Comments will 

be available in the AD docket shortly 

after receipt. 

FOR FURTHER INFORMATION CONTACT: 

Cesar Gomez, Aerospace Engineer, 

Airframe and Mechanical Systems 

Branch, ANE–171, FAA, New York 

Aircraft Certification Office, 1600 

Stewart Avenue, Suite 410, Westbury, 

NY 11590; telephone 516–228–7318; fax 

516–794–5531. 

SUPPLEMENTARY INFORMATION: 

Comments Invited 

We invite you to send any written 

relevant data, views, or arguments about 

this proposed AD. Send your comments 

to an address listed under the 

ADDRESSES section. Include ‘‘Docket No. 

FAA–2014–0483; Directorate Identifier 

2014–NM–082–AD’’ at the beginning of 

your comments. We specifically invite 

comments on the overall regulatory, 

economic, environmental, and energy 

aspects of this proposed AD. We will 

consider all comments received by the 

closing date and may amend this 

proposed AD based on those comments. 

We will post all comments we 

receive, without change, to http://

www.regulations.gov, including any 


emcdonald on DSK67QTVN1PROD with PROPOSALS