75496 Federal Register / Vol. 79, No. 243 / Thursday, December 18, 2014 / Proposed Rules 

TABLE 5 

Component of short-term wholesale funding 

Remaining 

maturity of 30 

days of less or 

no maturity 

(percent) 

Remaining 

maturity of 31 

to 90 days 

(percent) 

Remaining 

maturity of 91 

to 180 days 

(percent) 

Remaining 

maturity of 181 

to 365 days 

(percent) 

Secured funding transaction secured by a level 1 liquid asset ....................... 25 10 0 0 

(1) Secured funding transaction secured by a level 2A liquid asset; (2) Unsecured wholesale funding where the customer or counterparty is not a financial sector entity or a consolidated subsidiary thereof; (3) Brokered 

deposits and brokered sweep deposits provided by a retail customer or 

counterparty; (4) Covered asset exchanges involving the future exchange 

of a Level 1 asset for a Level 2A asset; and (5) Short positions where the 

borrowed security is either a Level 1 or Level 2A asset ............................. 50 25 10 0 

(1) Secured funding transaction secured by a level 2B liquid asset (2) Covered asset exchanges and short positions (other than those described in 

the category above) ..................................................................................... 75 50 25 10 

(1) Unsecured wholesale funding where the customer or counterparty is a 

financial sector entity or a consolidated subsidiary thereof; and (2) Any 

other component of short-term wholesale funding ...................................... 100 75 50 25 

(iii) Short-term wholesale funding 

definitions. The following definitions 

apply for purposes of paragraph 

(c)(5)(ii)(B) of this section. 

(A) Brokered deposit means any 

deposit held at a bank holding company 

that is obtained, directly or indirectly, 

from or through the mediation or 

assistance of a deposit broker as that 

term is defined in section 29 of the 

Federal Deposit Insurance Act (12 

U.S.C. 1831f(g)), and includes a 

reciprocal brokered deposit and a 

brokered sweep deposit. 

(B) Brokered sweep deposit means a 

deposit held at a bank holding company 

by a customer or counterparty through 

a contractual feature that automatically 

transfers to the bank holding company 

from another regulated financial 

company at the close of each business 

day amounts identified under the 

agreement governing the account from 

which the amount is being transferred. 

(C) Covered asset exchange means a 

transaction in which a bank holding 

company has provided assets of a given 

liquidity category to a counterparty in 

exchange for assets of a higher liquidity 

category, and the bank holding company 

and the counterparty agreed to return 

such assets to each other at a future 

date. Categories of assets, in descending 

order of liquidity, are level 1 liquid 

assets, level 2A liquid assets, level 2B 

liquid assets, and assets that are not 

HQLA. Covered asset exchanges do not 

include secured funding transactions. 

(D) Consolidated subsidiary means a 

company that is consolidated on the 

balance sheet of a bank holding 

company or other company under 

GAAP. 

(E) Deposit insurance means deposit 

insurance provided by the Federal 

Deposit Insurance Corporation under 

the Federal Deposit Insurance Act (12 

U.S.C. 1811 et seq.). 

(F) Financial sector entity has the 

meaning set forth in 12 CFR 249.3. 

(G) GAAP means generally accepted 

accounting principles as used in the 

United States. 

(H) High-quality liquid asset (HQLA) 

has the meaning set forth in 12 CFR 

249.3. 

(I) Level 1 liquid asset is an asset that 

qualifies as a level 1 liquid asset 

pursuant to 12 CFR 249.20(a). 

(J) Level 2A liquid asset is an asset 

that qualifies as a level 2A liquid asset 

pursuant to 12 CFR 249.20(b). 

(K) Level 2B liquid asset is an asset 

that qualifies as a level 2B liquid asset 

pursuant to 12 CFR 249.20(c). 

(L) Operational deposit has the 

meaning set forth in 12 CFR 249.3. 

(M) Retail customer or counterparty 

has the meaning set forth in 12 CFR 

249.3. 

(N) Secured funding transaction 

means any funding transaction that is 

subject to a legally binding agreement 

and gives rise to a cash obligation of the 

bank holding company to a counterparty 

that is secured under applicable law by 

a lien on assets owned by the bank 

holding company, which gives the 

counterparty, as holder of the lien, 

priority over the assets in the event the 

bank holding company enters into 

receivership, bankruptcy, insolvency, 

liquidation, resolution, or similar 

proceeding. Secured funding 

transactions include repurchase 

transactions, loans of collateral to the 

bank holding company’s customers to 

effect short positions, other secured 

loans, and borrowings from a Federal 

Reserve Bank. 

(O) Short position means a transaction 

in which a bank holding company has 

borrowed or otherwise obtained a 

security from a counterparty and sold 

that security to sell to another 

counterparty, and the bank holding 

company must return the security to the 

initial counterparty in the future. 

(P) Unsecured wholesale funding 

means a liability or general obligation, 

including a wholesale deposit, of the 

bank holding company to a wholesale 

customer or counterparty that is not 

secured under applicable law by a lien 

on assets owned by the bank holding 

company. 

(Q) Wholesale customer or 

counterparty means a customer or 

counterparty that is not a retail 

customer or counterparty. 

By order of the Board of Governors of the 

Federal Reserve System, December 10, 2014. 

Robert deV. Frierson, 

Secretary of the Board. 

[FR Doc. 2014–29330 Filed 12–17–14; 8:45 am] 

BILLING CODE 6210–01–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 25 

[Docket No.: FAA–2014–1027; Notice No. 

14–09] 

RIN 2120–AK24 

Transport Airplane Fuel Tank and 

System Lightning Protection 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed rulemaking 

(NPRM). 

SUMMARY: The FAA proposes to amend 

certain airworthiness regulations for 

transport category airplanes regarding 

lightning protection of fuel tanks and 

mstockstill on DSK4VPTVN1PROD with PROPOSALS

Federal Register / Vol. 79, No. 243 / Thursday, December 18, 2014 / Proposed Rules 75497 

1Fuel system, in the context of this NPRM, 

includes any component within either the fuel tank 

structure or the fuel tank systems and any other 

airplane structure or system components that are 

penetrating, located within, or connected to the fuel 

tanks. 

2Fuel tank structure, in the context of this NPRM, 

includes structural members of the fuel tank such 

as airplane skins, access panels, joints, ribs, spars, 

stringers, and associated fasteners, brackets, 

coatings and sealant. 

3Fuel tank systems, or systems, in the context of 

this NPRM, include tubing, components, and wiring 

that are penetrating, located within, or connected to 

the fuel tanks. 

systems. This action would establish 

design requirements for both normal 

conditions and possible failures of fuel 

tank structure and systems that could 

lead to fuel tank explosions, add new 

maintenance requirements related to 

lightning protection features, and 

impose specific requirements for 

airworthiness limitations in the 

instructions for continued 

airworthiness. We would create 

performance-based standards for 

prevention of catastrophic fuel vapor 

ignition caused by lightning by 

regulating the risk due to both ignition 

sources and fuel tank flammability. This 

change would allow designers to take 

advantage of flammability reduction 

technologies whose effectiveness was 

not foreseen when earlier revisions to 

these rules were written. This change 

would also relieve some of the 

administrative burdens created by the 

current regulations. These proposed 

amendments are based on 

recommendations from the Large 

Airplane Fuel System Lightning 

Protection Aviation Rulemaking 

Committee (Lightning ARC). 

DATES: Send comments on or before 

March 18, 2015. 

ADDRESSES: Send comments identified 

by docket number FAA–2014–1027 

using any of the following methods: 

• Federal eRulemaking 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: For 

technical questions concerning this 

action, contact Massoud Sadeghi, 

Airplane and Flight Crew Interface 

Branch, ANM–111, Transport Airplane 

Directorate, Aircraft Certification 

Service, Federal Aviation 

Administration, 1601 Lind Avenue SW., 

Renton, WA 98057–3356; telephone 

(425) 227–2117; facsimile (425) 227– 

1149; email massoud.sadeghi@faa.gov. 

For legal questions concerning this 

action, contact Sean Howe, Office of the 

Regional Counsel, ANM–7, Federal 

Aviation Administration, 1601 Lind 

Avenue SW., Renton, Washington 

98057–3356; telephone (425) 227–2591; 

facsimile (425) 227–1007; email 

Sean.Howe@faa.gov. 

SUPPLEMENTARY INFORMATION: 

Authority for This Rulemaking 

The FAA’s authority to issue rules on 

aviation safety is found in Title 49 of the 

United States Code. Subtitle I, Section 

106 describes the authority of the FAA 

Administrator. Subtitle VII, Aviation 

Programs, describes in more detail the 

scope of the agency’s authority. 

This rulemaking is promulgated 

under the authority described in 

Subtitle VII, Part A, Subpart III, Section 

44701, ‘‘General Requirements.’’ Under 

that section, the FAA is charged with 

promoting safe flight of civil aircraft in 

air commerce by prescribing regulations 

and minimum standards for the design 

and performance of aircraft that the 

Administrator finds necessary for safety 

in air commerce. This regulation is 

within the scope of that authority. It 

prescribes new safety standards for the 

design and operation of transport 

category airplanes. 

I. Overview of Proposed Rule 

The FAA proposes to amend the 

airworthiness regulations in Title 14, 

Code of Federal Regulations (14 CFR) 

part 25 related to lightning protection 

for fuel systems 1 (including fuel tank 

structure 2 and systems.3) This action 

would remove the requirement for the 

prevention of lightning ignition sources 

from § 25.981(a)(3) at Amendment 25– 

102 and add a new requirement to 

§ 25.954 for the prevention of ignition 

due to lightning. 

We propose to revise § 25.954 to 

expand and clarify its objective and to 

modify it to meet current knowledge 

about lightning and state-of-the-art 

airplane design. This new requirement 

would reduce the risk of fuel tank 

ignition by requiring applicants to 

account for both ignition sources and 

fuel tank flammability limits established 

by existing regulations. The proposed 

amendments would adopt a 

performance-based standard to prevent 

catastrophic fuel tank vapor ignition 

due to lightning, rather than focus solely 

on the prevention of ignition sources. 

We propose to insert an exception 

into § 25.981(a)(3) to remove its 

applicability to lightning protection. 

Inclusion of lightning in that section has 

resulted in recurring cases where 

applicants showed that compliance was 

impractical, leading them to seek 

exemptions to compliance with § 25.981 

for fuel tank structural aspects. We have 

not issued exemptions for systemsrelated lightning protection, but we 

believe common treatment of structureand systems-related lightning protection 

in the fuel system is appropriate. 

To maintain the integrity of lightning 

protection features of airplanes 

certificated under the amended rules, 

we propose to amend part 25 appendix 

H to create a new requirement for 

applicants to establish airworthiness 

limitations specific to the airworthiness 

of fuel tank structure and systems 

lightning protection features. 

This proposed rule would affect 

manufacturers who apply for type 

certification of new or significantly 

modified transport category airplanes, 

specifically, the airplanes’ fuel tank 

structures and systems. It would also 

apply to applicants for supplemental 

type certificates for such modifications. 

This proposal would revise the part 25 

regulations for design and maintenance 

of lightning protection features for fuel 

tank structure and systems. 

mstockstill on DSK4VPTVN1PROD with PROPOSALS

75498 Federal Register / Vol. 79, No. 243 / Thursday, December 18, 2014 / Proposed Rules 

4ARP5412, Aircraft Lightning Environment and 

Related Test Waveforms, SAE International, 

November 1999. 

5ARP5414, Aircraft Lightning Zoning, SAE 

International, December 1999. 

6ARP5416, Aircraft Lightning Test Methods, SAE 

International, March 2005. 

II. Background 

A. Statement of the Problem 

We have found that compliance with 

§ 25.981(a)(3), as it is currently written, 

is not always practical. The 

impracticality has led applicants to 

petition for exemptions and the FAA to 

impose special conditions to achieve the 

intended level of safety of the rule, 

which has created an administrative 

burden on industry and the FAA. 

B. History of Lightning-Related Fuel 

Tank Explosion Events 

Lightning strikes to airplanes do 

occur, particularly when operating in 

instrument meteorological conditions. 

When lightning strikes an airplane, high 

transient current is conducted in the 

airplane structure. The transient current 

can melt, burn, and deform airplane 

parts and structure where the lightning 

attaches to the airplane. This current is 

also conducted through the airplane 

structure between the lightning 

attachment points on the airplane. The 

conducted lightning transient current 

can also induce voltage and current on 

airplane wiring, tubes, and control 

mechanisms. Melting, burning, arcing, 

or sparking due to conducted lightning 

current or voltage can result in fuel 

vapor ignition if they occur in a 

flammable environment. 

On June 26, 1959, a Lockheed L– 

1649A Constellation was struck by 

lightning, which caused explosions in 

two of its fuel tanks, resulting in a crash. 

This airplane was fueled with aviation 

gasoline. Prior to this accident, 

government and industry had 

conducted research into the possible 

effects of lightning on airplane fuel 

tanks, but the scope of this research had 

been limited to the melting of integral 

fuel tank skin, and hot-spot formation. 

Fuel vapor ignition due to lightning 

was the probable cause of a Boeing 707 

accident that occurred near Elkton, 

Maryland on December 8, 1963. At the 

time of its certification, the 707 was not 

required to demonstrate effective 

lightning protection for fuel systems. 

Following the 707 accident, government 

and industry performed substantial 

research to determine the factors that 

could result in lightning-related fuel 

vapor ignition. However, most of this 

research focused on lightning burnthrough for metal fuel tank structure, 

and lightning-related ignition of fuel 

vapor in fuel vents. 

On December 23, 1971, lightning 

struck a Lockheed L–188A Electra, 

which led to a fire and separation of the 

right wing. Since the L–188A was 

certified by the FAA in 1958, the type 

did not benefit from the additional 

attention given to airplane fuel tanks 

after § 25.954 was published in 1967. 

On May 9, 1976, a Boeing 747 crashed 

during descent into Madrid, Spain 

following a lightning strike to the 

airplane. The investigation of this 

accident found evidence that fuel vapor 

ignition could have been caused by 

lightning-induced sparking at a motordriven fuel valve. 

In three of the four accidents noted 

above, investigations found that the 

airplane fuel tanks contained either 

aviation gasoline or a mixture of Jet A 

kerosene-type fuels and higher volatility 

Jet B/JP–4 fuels. The fuel type involved 

in the 1971 Electra accident was not 

identified. The investigations for the 

other three accidents determined that 

the fuel mixtures would be flammable at 

the temperatures and altitudes that the 

airplanes were flying at the time of the 

lightning strikes. During the 1980s the 

use of Jet B/JP–4 fuels began to decline 

and those fuels became nearly obsolete 

in the 1990s. 

Since the last lightning-related 

airplane fuel tank explosion (1976), the 

understanding of lightning effects on 

airplane fuel tanks and systems has 

increased significantly, and no further 

events have occurred even though the 

number of flight hours since the 1976 

accident (approaching 1 billion) is more 

than 8 times that which preceded that 

event (less than 120 million). 

Methods for preventing ignition 

sources due to lightning strikes are 

mature and are based on years of 

research into natural lightning 

characteristics and effects on airplane 

structure and systems. The results have 

been documented in a large body of 

literature and formalized into SAE 

standards such as ARP5412,4 ARP5414,5

and ARP5416.6 The FAA has accepted 

use of these standards through Advisory 

Circulars (AC) 20–53B, Protection of 

Aircraft Fuel Systems Against Fuel 

Vapor Ignition Caused by Lightning, and 

AC 20–155, SAE Documents to Support 

Aircraft Lightning Protection 

Certifications. The International 

Conference on Lightning and Static 

Electricity (ICOLSE), National 

Aeronautics and Space Administration 

(NASA), the European Organization on 

Commercial Aircraft Equipment 

(EUROCAE), and other industry forums 

have published much of the supporting 

research. A high level of communication 

among airplane lightning specialists 

worldwide ensures that designers and 

certification authorities are continually 

informed of advances in lightning 

protection technology and application 

of this technology to new designs. 

C. Advancement of Current Regulations 

and Associated Guidance 

Following the 1963 Boeing 707 Elkton 

accident, the FAA adopted new fuel 

system lightning protection regulations. 

These regulations were implemented for 

transport category airplanes in § 25.954 

at Amendment 25–14, Fuel system 

lightning protection. Section 25.954 

states: 

The fuel system must be designed and 

arranged to prevent the ignition of fuel 

vapor within the system by— 

(a) Direct lightning strikes to areas 

having a high probability of stroke 

attachment; 

(b) Swept lightning strokes to areas 

where swept strokes are highly 

probable; and 

(c) Corona and streamering at fuel 

vent outlets. 

This regulation requires lightning 

protection regardless of the likelihood 

that lightning would strike the airplane. 

This regulation does not acknowledge 

that lightning protection features could 

fail or become ineffective. The 

regulation contains no requirement for 

fault-tolerant fuel system lightning 

protection or for any evaluation of 

probabilities of failures related to the 

lightning protection features. 

Following the 1976 Madrid Boeing 

747 accident, the FAA issued a number 

of airworthiness directives to address 

possible sources of ignition that were 

found during the investigation. The 

FAA subsequently developed further 

guidance for airplane fuel system 

lightning protection. Specifically, the 

FAA revised AC 20–53, Protection of 

Airplane Fuel Systems Against Fuel 

Vapor Ignition Due to Lightning. This 

AC has been revised twice since its 

original issue. These documents added 

emphasis regarding lightning protection 

of fuel system components such as fuel 

tubes, fuel quantity systems, and fuel 

filler caps. 

On July 17, 1996, a Boeing 747 

operating as TWA Flight 800 was 

involved in an in-flight breakup after 

takeoff. The ensuing investigation 

determined that the center wing fuel 

tank exploded due to an unknown 

ignition source. Following the Flight 

800 accident, the FAA reviewed the 

transport airplane fleet history and 

determined that fail-safe design 

principles had not been properly 

applied to prevent ignition sources in 

fuel tanks and application of the 

existing rules had not been adequate to 

mstockstill on DSK4VPTVN1PROD with PROPOSALS

Federal Register / Vol. 79, No. 243 / Thursday, December 18, 2014 / Proposed Rules 75499 

7Aviation Rulemaking Advisory Committee— 

New Task: ‘‘Prevention of Fuel Tank Explosions;’’ 

published in the Federal Register January 23, 1998 

(63 FR 3614–3615). 

8Aviation Rulemaking Advisory Committee: 

‘‘Fuel Tank Harmonization Working Group—Final 

Report;’’ July 1998. Available in the docket. 

9 DOT/FAA/CT–83/3. User’s manual for AC–20– 

53A Protection of Airplane Fuel Systems Against 

Fuel Vapor Ignition Due to Lightning; FAA 

Technical Center and SAE–AE4L Lightning 

Subcommittee, October 1984. 

prevent fuel tank explosions. The FAA 

also found that preventing ignition 

sources throughout the life cycle of a 

transport category airplane was an 

extremely difficult task and agreed with 

National Transportation Safety Board 

(NTSB) recommendations to also reduce 

or eliminate fuel tank flammability. 

1. Amendment 25–102 

In January 1998 the FAA tasked 7 an 

Aviation Rulemaking Advisory 

Committee (ARAC) to provide specific 

recommendations and propose 

regulatory text that would eliminate or 

significantly reduce the hazards 

associated with explosive vapors in 

transport category airplane fuel tanks. 

Under the tasking, the proposed 

regulatory text was to ensure that new 

type designs of transport category 

airplanes are designed and operated so 

that during normal operation (up to 

maximum certified operating 

temperatures) the presence of explosive 

fuel vapor in all tanks is eliminated, 

significantly reduced, or controlled to 

the extent that there could not be a 

catastrophic event. The ARAC 

concluded 8 it was not practical to 

eliminate fuel tank flammability. They 

determined that the safety level of 

unheated aluminum main fuel tanks on 

airplanes using Jet A type fuel was 

adequate, and recommended that fuel 

tank flammability be limited to that 

level. 

In May 2001 the FAA adopted 

Amendment 25–102 (66 FR 23086– 

23131) revising § 25.981, Fuel tank 

ignition prevention, which was intended 

to prevent future fuel tank explosions. 

This amendment adopted a new 

§ 25.981(a)(3), which eliminated 

ambiguity as to the necessary methods 

of compliance with the previously 

established requirements of §§ 25.901 

and 25.1309. As stated in AC 25.981– 

1C, ‘‘. . . in order to eliminate any 

ambiguity as to the restrictions on latent 

failures, § 25.981(a)(3) explicitly 

requires that any anticipated latent 

failure condition not result in the 

airplane being one failure away from a 

catastrophic fuel tank ignition.’’ 

This new paragraph added the 

requirement that the fuel tank design 

address potential failures that could 

cause ignition sources within the fuel 

system. Section 25.981(a)(3) requires 

consideration of factors such as aging, 

wear, and maintenance errors as well as 

the existence of single failures, 

combinations of failures not shown to 

be extremely improbable, and single 

failures in combination with latent 

failures to account for the cause of many 

ignition sources in fuel tanks and 

deficiencies in the existing regulations. 

Section 25.981(a)(3) states that 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 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. 

While lightning was not listed as a 

probable cause of the Flight 800 

accident, the FAA’s accident and 

incident historical review of fuel tank 

explosions resulted in our finding that 

improving fuel tank safety required 

preventing ignition from all sources, 

including lightning. Potential ignition 

sources due to lightning must be 

considered as part of compliance with 

this regulation, as discussed in the 

rulemaking preamble for § 25.981(a)(3) 

and the associated AC 25.981–1. This 

regulation effectively requires fail-safe 

ignition prevention means, like 

redundant features, or monitoring and 

indication of failures, be provided. 

However, in applying this rule to recent 

certification programs, we found that for 

the purpose of lightning protection, 

providing redundant features is not 

always practical. For example, failures 

of lightning protection features could 

remain latent for years between 

inspections, thereby exposing the fuel 

tank to the risk of ignition due to 

lightning. Typically these latent failures 

cannot be shown to be extremely remote 

considering the long inspection 

intervals. 

The preamble to Amendment 25–102 

stated the FAA’s assumption that 

environmental conditions such as 

lightning are present when failures of 

systems occur. Consistent with this 

approach, AC 25.981–1C also states that 

applicants should assume that a 

lightning attachment could occur at any 

time (probability of lightning = 1). In 

addition, industry and FAA practice 

had been to assume that a defined set of 

severe lightning current components 

would be associated with every 

lightning strike to the aircraft. AC 

25.981–1C, as well as the user’s 

manual 9 associated with AC 20–53 that 

defines guidance for compliance to 

§ 25.954, also states that applicants 

should assume that the fuel tank is 

always flammable (probability = 1). 

Amendment 25–102 also introduced 

§ 25.981(b) requirements to identify 

critical design configuration control 

limitations (CDCCLs) to prevent 

development of ignition sources within 

the fuel tank systems. 

When Amendment 25–102 was 

adopted, the FAA considered it 

practical to limit fuel tank flammability 

to that of an unheated aluminum fuel 

tank. As recommended by the ARAC, 

the amendment adopted § 25.981(c) that 

required minimizing the flammability of 

airplane fuel tanks, or mitigating the 

effects of an explosion such that any 

damage from a fire or explosion would 

not prevent continued safe flight and 

landing. The FAA considered 

flammability control, through the use of 

fuel tank designs that provided cooling 

of the tanks using ventilation, as well as 

locating heat sources away from fuel 

tanks, to be practical means of 

minimizing fuel tank flammability. The 

FAA explained in the preamble to the 

rule that the intent was to limit fuel tank 

flammability to that of an unheated 

aluminum wing fuel tank. This 

regulation did not specifically require 

fuel tank inerting, nor did the regulation 

state specific fuel tank flammability 

limits. The preamble to Amendment 25– 

102 stated: 

As noted previously in this preamble, we 

tasked the ARAC on July 14, 2000 (65 FR 

43800), to evaluate both on-board and 

ground-based fuel tank inerting systems. If 

further improvement is found to be 

practicable, we may consider initiating 

further rulemaking to address such 

improvements. 

At the time we developed 

Amendment 25–102 (i.e., 1998–2001), 

the FAA and industry were still 

exploring the dynamics of tank 

flammability and the fleet average 

flammability exposure for transport 

airplane fuel tanks. Evaluation of the 

technical and economic viability of fuel 

tank inerting systems for commercial 

transport airplanes was also in its early 

stages at that time. After promulgation 

of Amendment 25–102, the FAA and 

industry continued research and 

discussion of the measurement and 

modeling of fuel tank flammability and 

development of practical means to 

reduce or eliminate flammability in 

transport airplane fuel tanks. This 

mstockstill on DSK4VPTVN1PROD with PROPOSALS

75500 Federal Register / Vol. 79, No. 243 / Thursday, December 18, 2014 / Proposed Rules 

10 Inerting systems are approved for Boeing 

Models 737, 747, 757, 767, and 777 and for Airbus 

Models A320, A330, and A340. 

11FAA Large Airplane Fuel System Lightning 

Protection ARC, Final Report, May 2011. http://

www.faa.gov/regulations_policies/rulemaking/

committees/documents/media/LAFSLP.ARC.RR.

20110518.pdf. 

eventually led to the certification of 

practical retrofit designs for center wing 

fuel tank nitrogen generating systems on 

existing transport airplane models.10

Those systems use nitrogen-enriched air 

that is generated onboard the airplane to 

displace oxygen in the fuel tank. This 

results in inerting the fuel tank 

throughout most of the flight and 

ground operations. Some applicants for 

new type certificates involving 

composite wing structure have included 

flammability reduction means, such as 

an ullage inerting system, for all fuel 

tanks, including the main fuel tanks 

located in the wing. 

2. Amendment 25–125 

Amendment 25–125 (73 FR 42444– 

42504), which was part of the fuel tank 

flammability reduction (FTFR) rule 

adopted in 2008, revised § 25.981(b) and 

(c) to introduce specific performancebased standards for the maximum 

flammability allowed in various fuel 

tanks. Amendment 25–125 maintained 

the alternative adopted by Amendment 

25–102 allowing ignition mitigation 

means. Amendment 25–125 established 

a new fleet average flammability 

exposure limit of 3 percent for all fuel 

tanks, or that of an equivalent 

conventional unheated aluminum fuel 

tank. Fuel tanks that are not main fuel 

tanks and that have any portion located 

within the fuselage contour must be 

limited to 3 percent fleet average 

exposure and 3 percent warm day 

exposure. Amendment 25–125 did not 

change the ignition prevention 

standards of § 25.981(a), and it moved 

the CDCCL requirements created by 

Amendment 25–102 to § 25.981(d). 

Introduction of airplane designs with 

composite fuel tanks that cannot be 

shown to meet the flammability 

requirements of § 25.981 has resulted in 

the need to provide active fuel tank 

flammability control systems in all fuel 

tanks. For main tanks that were only 

required to be equivalent to unheated 

aluminum wing tanks, these systems 

reduce fuel tank flammability well 

below that required by § 25.981(c). The 

FAA has issued special conditions for 

new airplane designs that allow 

consideration of these fuel tank 

flammability control systems when 

showing that fuel tank ignition will not 

result from structural ignition sources 

following a lightning strike. 

D. Related Actions Following the 

Adoption of Amendment 25–102 

Several applicants found that it was 

impractical to achieve dual fault 

tolerance for fuel tank structure 

lightning protection. The FAA agreed 

that applying § 25.981(a)(3) for fuel tank 

structure was impractical in certain 

cases. The FAA required the safety 

assessment associated with the fuel tank 

system to include the assumptions that 

the fuel tank was always flammable and 

lightning was continuously present. 

However, when evaluating where 

lightning attaches to the airplane and 

considering the lightning protection 

features, the probability of strikes that 

could cause an ignition source is 

significantly less than the required 

assumptions. We have defined strikes 

that could cause an ignition source as 

‘‘critical lightning strikes.’’ Critical 

lightning strikes occur on the order of 

once every 100,000 hours of airplane 

operation. In addition, for airplanes 

with the fuel tank flammability 

reduction means required by § 25.981, 

the likelihood of a fuel tank being 

flammable is less than one hour for 

every hundred hours of operation. For 

airplanes without fuel tank flammability 

reduction means (i.e., with unheated 

aluminum wing tanks), the flammability 

range is one to five hours for every one 

hundred hours of operation. 

Consideration of these factors in 

combination with fail-safe ignition 

required by § 25.981, which typically 

resulted in the need for triple-redundant 

lightning ignition prevention features, 

led the FAA to conclude that the 

required assumptions were overly 

conservative. 

As a result, on May 26, 2009, the FAA 

issued a policy memorandum to 

standardize the process for granting 

exemptions and issuing special 

conditions for fuel tank structure 

lightning protection. FAA Policy 

Memorandum ANM–112–08–002, 

Policy on Issuance of Special Conditions 

and Exemptions Related to Lightning 

Protection of Fuel Tank Structure, 

defined requirements that were to be 

applied through special conditions or 

exemptions. This policy allowed the 

consideration of the likelihood of both 

the occurrence of a critical lightning 

strike and the tank being flammable. 

The policy contained detailed 

information that explained the design 

goal of § 25.981(a)(3) for fuel tank 

structure and provided guidance for 

alternatives to compliance that still 

achieved that design goal. 

In 2009 the FAA chartered the 

Lightning ARC to re-examine §§ 25.954 

and 25.981 at Amendments 25–102 and 

25–125 for fuel tank lightning 

protection. The Lightning ARC included 

industry members that were the leading 

aircraft lightning protection design 

experts in the world, along with the 

leading regulatory experts working in 

the lightning area. To address structurespecific issues, such as the occurrence 

of cracks and fastener failures, the 

Lightning ARC established a 

subcommittee made up of airplane 

manufacturer structural experts. The 

ARC also commissioned a specific study 

of lightning current distribution at 

structural cracks and fasteners, 

including the evaluation of lightningrelated sparks at these cracks and 

fasteners. In May 2011 the Lightning 

ARC issued a final report 11 that 

included the results of these special 

studies and their findings and 

recommendations. They proposed new 

rulemaking on the following topics: 

1. Lightning-specific requirements 

that focused on ignition source 

prevention; 

2. Inclusion of both structure and 

systems in the same fuel system 

lightning protection rule with the same 

requirements; 

3. Single fault-tolerant designs, or if 

impractical, a qualitative assessment to 

ensure the combination of non-faulttolerant failures resulting in an ignition 

source, is remote; 

4. Design, manufacturing processes, 

and instructions for continued 

airworthiness (ICA) to address 

manufacturing variability, aging, wear, 

corrosion, and likely damage; 

5. ICA to include caution information 

for critical lightning protection features 

to minimize accidental damage during 

maintenance, alteration, or repairs; 

6. Inclusion of inspections and 

procedures required for non-faulttolerant designs in the Airworthiness 

Limitations Section of the ICA; 

7. Addition of a new section in the 

ICA specific to fuel tank lightning 

protection; 

8. No requirement for lower 

flammability in the lightning regulations 

(i.e., retain existing flammability 

requirements); and 

9. Development of new guidance 

material and revision of existing 

guidance material to ensure a consistent 

approach to fuel system lightning 

protection. 

To address these recommendations, 

the FAA issued a new policy statement 

that superseded Policy Memorandum 

ANM–112–08–002 as an interim 

mstockstill on DSK4VPTVN1PROD with PROPOSALS

Federal Register / Vol. 79, No. 243 / Thursday, December 18, 2014 / Proposed Rules 75501 

approach until new rulemaking could 

be accomplished. Policy Statement PS– 

ANM–25.981–02, Policy on Issuance of 

Special Conditions and Exemptions 

Related to Lightning Protection of Fuel 

Tank Structure and Systems, issued 

June 24, 2014, expands the scope of the 

previous policy to include systems and 

provides guidance for special conditions 

and exemptions that are applicable to 

the design of lightning protection 

features in fuel tank structure and 

systems with respect to compliance 

with § 25.981(a)(3). 

The proposed revisions to 

§ 25.981(a)(3) would eliminate the need 

to issue special conditions and 

exemptions; however, the detailed 

information provided in that policy 

statement addresses the design goal of 

the proposed § 25.954 for fuel tank 

structure and systems and provides 

valuable information about means of 

compliance. Therefore, a copy of that 

policy statement has been added to the 

docket for this rule. 

III. Discussion of the Proposal 

A. General 

In order to comply with the latent 

failure criterion of § 25.981(a)(3), 

systems with potentially catastrophic 

failure conditions resulting from a 

lightning strike typically need at least 

triple-redundancy in their protective 

features, or dual-redundancy with 

continuous system monitoring to reduce 

the latency period. Dual-redundant 

designs could only be shown to comply 

with § 25.981(a)(3) when combined with 

either regular inspections at very short 

intervals or with a monitoring device to 

verify the functionality of the protective 

features. Inspection of the various 

design features might be difficult or 

impossible if, for example, the feature is 

covered by airframe structure. This level 

of redundancy has been shown to be 

impractical for certain areas of airplane 

structure, such as airplane skins, joints, 

ribs, spars, stringers, and associated 

fasteners, brackets, and coatings. 

Lightning protection features are 

typically an integral part of the fuel tank 

structure or inside the fuel tanks. Due to 

the frequency of inspections that would 

be required to sufficiently limit 

exposure to latent failures, it would be 

impractical to use inspections of 

lightning protection features by 

themselves to eliminate the requirement 

for triple redundancy. Therefore, the 

FAA proposes to amend the 

requirements of §§ 25.954 and 

25.981(a)(3) to address these and other 

issues related to fuel tank lightning 

protection design. The FAA’s intent is 

to establish a balanced approach to 

ensure that airplane designs provide an 

acceptable level of safety, while 

allowing manufacturers to develop an 

economically viable design, economical 

manufacturing methods, and effective 

maintenance programs considering the 

limitations in preventing or managing 

failures inside the fuel tanks. To 

preclude a catastrophic event, the 

proposed standards would require the 

applicant to develop structural and 

system component designs that are free 

of ignition sources. In addition, the 

applicant must still account for fuel 

vapor flammability as required in 

§ 25.981(b). This proposal would also 

allow applicants to take credit for 

providing reduced flammability 

exposure below what is required by 

§ 25.981(b). 

Practicality is a balance of available 

means, economic viability, and 

proportional benefit to safety. A means 

to provide fault tolerance against 

potential ignition sources that is 

possible with little economic impact is 

practical even if the potential ignition 

source conditions would be remote 

without them. In general, applicants 

have found fault tolerance to be 

practical for systems lightning 

protection features. However, in several 

cases, applicants found that providing 

fault tolerance was impractical because 

the means had a significant economic 

impact on production, operational, or 

maintenance costs. In these cases, it is 

not necessary that the applicants use 

these means if it can be determined that 

the probability of a potential ignition 

source, combined with a critical 

lightning strike and flammable fuel tank 

conditions is such that catastrophic 

failure is not anticipated over the life of 

the fleet. 

B. ‘‘Fuel System Lightning Protection’’ 

(§ 25.954) 

The current rule specifies the primary 

lightning threats to the fuel system and 

requires designs that prevent ignition of 

fuel vapor within the system. The 

original intent was to prevent ignition of 

fuel vapor in the fuel tank structure and 

system due to lightning. 

As written, the current rule does not 

address failures or deterioration of the 

lightning protection features. 

In lieu of regulating fuel tank 

lightning protection by §§ 25.954 and 

25.981, we propose to consolidate 

requirements for the prevention of fuel 

vapor ignition solely in § 25.954. We 

propose to retain (and renumber) the 

existing rule text of § 25.954, add a 

clarification of the existing requirements 

regarding lightning-induced or 

conducted electrical transients, and add 

two new performance-based 

requirements to regulate the risk of 

failures and to maintain the integrity of 

the lightning protection features during 

the airplane service life. 

The addition of a clarification 

regarding lightning-induced or 

conducted electrical transients is 

needed to make it clear that this 

regulation addresses these effects. 

Lightning strikes to airplanes result in 

significant current conducted through 

airplane structure and equipment, and 

can induce voltage and current on 

wires, tubes, and equipment. The use of 

composite structure can increase these 

induced and conducted electrical 

transients. Therefore, this proposed rule 

would require that the design and 

arrangement of the fuel system prevent 

the ignition of fuel vapor within the 

system by lightning-induced and 

conducted electrical transients. 

A new paragraph (b) would require 

that catastrophic ignition caused by 

lightning be extremely improbable, 

placing that risk in line with that of all 

other potentially catastrophic hazards. 

The proposed rule would require the 

type design to take into account the 

likelihood of a critical lightning strike, 

the fuel tank being flammable, and 

creation of an ignition source due to the 

failure of fuel system or structural 

lightning protection features. The 

purpose of the proposed rule is to 

ensure that a catastrophic fuel vapor 

ignition will not occur due to any single 

failure when lightning attaches to the 

airplane. In addition, the combination of 

the probabilities of a critical lightning 

strike, a flammable fuel tank condition, 

and the exposure time of all specified 

failures of structural features that are 

not fault-tolerant (and that can occur 

within the fuel tank) must, under the 

proposed rule, be such that catastrophic 

failure from ignition due to lightning 

would not be anticipated over the life of 

that airplane fleet. For example, for each 

structural discrepancy identified, the 

applicant would be required to 

demonstrate that mandated structural 

inspection procedures would reliably 

detect cracks or failed fasteners/capseals (where the gap size required to 

create arcing is exceeded) before the 

combined probability of the occurrence 

of a flammable fuel tank condition and 

a critical lightning strike was exceeded. 

The proposed rule would also require 

that the type design take into account 

the failure of other system components 

that may run into and/or through the 

fuel tank and can be an ignition source 

in the event of a critical lightning strike. 

Lightning-related ignition of flammable 

fluids and vapors due to leakage outside 

the fuel system and the resultant 

mstockstill on DSK4VPTVN1PROD with PROPOSALS

75502 Federal Register / Vol. 79, No. 243 / Thursday, December 18, 2014 / Proposed Rules 

12See Legal Interpretation to William Szendrey 

from Rebecca MacPherson (Apr. 28, 2005). 

hazards will continue to be covered in 

§ 25.863. 

The proposed rule would use ‘‘taking 

into account,’’ rather than ‘‘consider,’’ 12

a term the FAA has previously used. We 

intend no substantive effect by this 

change. 

We propose to add a new paragraph 

(c) that would require applicants to 

develop CDCCLs that identify lightning 

protection design features, instructions 

on how to protect them, and inspection 

and test procedures specific to lightning 

protection features within fuel tank 

structure and systems to detect and 

correct any anomalies or failures during 

the life of the airplane. Section 25.954 

as written in 1967 required applicants to 

design lightning protection features into 

fuel tank structure and systems, but it 

does not account for the deterioration of 

those features during the life of the 

airplane. During inspections and 

accident investigations, we found 

damage and deterioration of fuel tank 

lightning protection features such as 

bonding straps, brackets, and sealants 

that could present gaps or other 

electrical discontinuities that could 

become ignition sources in the presence 

of lightning strikes. 

CDCCLs are one type of fuel system 

airworthiness limitation that define 

critical features of the design that must 

be maintained. CDCCLs were originally 

required by the fuel tank explosion 

prevention standards of § 25.981 and 

appendix H to 14 CFR part 25 at 

Amendment 25–102. Fuel system 

airworthiness limitations include 

mandatory replacement times, 

inspection intervals, related inspection 

procedures, and CDCCLs. As explained 

in the FTFR final rule, Amendment 25– 

125, ‘‘The intent of the CDCCL 

requirement is to define the critical 

features of the design that could be 

unintentionally altered in a way that 

could cause reduction in fuel system 

safety.’’ CDCCLs are distinct from 

mandatory replacement times, 

inspection intervals, and inspections 

and other procedures. 

This proposed new paragraph will 

require applicants to identify the 

lightning protection design features of 

the airplane, as well as to prepare 

instructions on how to protect those 

features. Identification of a feature refers 

to listing the feature in the CDCCL. The 

FAA has determined that during 

airplane operations, modifications, and 

unrelated maintenance actions, these 

features can be unintentionally damaged 

or inappropriately repaired or altered. 

Instructions on protection are meant to 

address this safety concern. An example 

of a common design feature to prevent 

catastrophic ignition caused by 

lightning is wire separation so that 

wires cannot chafe against one another. 

An example of an instruction on how to 

protect this design feature would be, 

‘‘When performing maintenance or 

alterations in the vicinity of these wires, 

ensure a minimum of 6-inch wire 

separation is maintained.’’ 

Addressing the effects of aging, wear, 

and corrosion as both a design and 

continuing airworthiness consideration 

is necessary to ensure reliable 

protection over the life of the airplane. 

The proposed rule would require 

applicants to establish necessary 

inspection and test procedures to 

prevent development of lightningrelated ignition sources within the fuel 

tank structure and systems. One 

example of an inspection procedure 

would be to examine a structural 

element for cracks. An example of a test 

procedure would be a functional test to 

ensure a ground fault interrupter 

continues to function. The FAA would 

require these inspection and test 

procedures to include airworthiness 

limitations for non-fault-tolerant 

features and caution information for 

lightning protection features that may be 

altered by maintenance and repairs. For 

non-fault-tolerant lightning protection 

features that are identified in support of 

certification, the rule would require 

applicants to develop and identify 

inspection and test procedures as 

airworthiness limitations in the 

instructions for continued 

airworthiness, approved by the FAA, in 

order to preclude the development of 

unsafe conditions. 

We also propose to add a new 

paragraph (d) to define ‘‘critical 

lightning strike’’ and ‘‘fuel system’’ for 

the purpose of this section. 

C. ‘‘Fuel Tank Ignition Prevention’’ 

(§ 25.981(a)(3)) 

Section 25.954 provides requirements 

for protection from ignition due to 

lightning, and § 25.981 provides 

requirements for protection against 

ignition from all sources, including 

lightning. The redundancy of the rule 

coverage has caused confusion 

regarding which regulation applies to 

fuel tank lightning protection. 

To consolidate lightning protection 

requirements into one rule, § 25.954, we 

propose to add an exception to 

§ 25.981(a)(3) removing lightning as an 

ignition source from the scope of this 

section and referring applicants to 

§ 25.954 for lightning protection 

requirements. 

Section 25.981(d) at Amendment 25– 

125 requires CDCCLs, inspections, or 

other procedures to be established to 

ensure fuel tank safety. The FAA 

intended that CDCCLs would be 

required to identify critical design 

features, and that inspections or other 

procedures would also be provided 

where it was determined necessary. 

However, some have misunderstood the 

wording to allow inspections or other 

procedures, for example adhering to 

component maintenance manuals alone, 

instead of maintaining the original 

design details of the critical feature. We 

are proposing to revise this rule text to 

clarify that CDCCLs must be provided to 

identify critical design features, in 

addition to inspections or other 

procedures. 

Note: The title of § 25.981 would be 

corrected in this rulemaking from ‘‘Fuel Tank 

Ignition Prevention’’ to ‘‘Fuel Tank Explosion 

Prevention.’’ We intended this change with 

Amendment 25–125, but the change was not 

accomplished. 

D. Instructions for Continued 

Airworthiness (Appendix H to Part 25) 

1. Airworthiness Limitations Section 

(H25.4) 

Currently, section H25.4 does not 

expressly mention instructions about 

lightning protection features. We 

propose to add a new paragraph 

H25.4(5) that will make mandatory any 

inspection and test procedures that are 

needed to sustain the integrity of the 

lightning protection features that are 

used to show compliance with § 25.954. 

2. Lightning Protection Features 

Instructions for Continued 

Airworthiness (H25.X) 

We propose to add a new section to 

appendix H to require applicants to 

develop instructions for continued 

airworthiness that are approved by the 

FAA, and that are specific to the 

lightning protection features for fuel 

tank structure and systems required by 

§ 25.954. 

E. Advisory Circular 

The FAA would develop one new 

proposed AC and would propose 

revisions to two other ACs to be 

published concurrently with the 

proposed regulations contained in this 

NPRM. The proposed new AC would 

provide guidance material for 

acceptable means, but not the only 

means, of demonstrating compliance 

with proposed § 25.954. The revisions to 

the existing ACs would update them to 

reflect the revised rules. 

mstockstill on DSK4VPTVN1PROD with PROPOSALS

Federal Register / Vol. 79, No. 243 / Thursday, December 18, 2014 / Proposed Rules 75503 

13 Ibid. 

14 ‘‘Fleet Discovery’’ 2000–2004 Penton, provided 

by Aviation Week Intelligence Network, data 

through the end of April 2014 Ibid. 

15 Ibid. 

16 Ibid 1 and 2. 

IV. Regulatory Notices and Analyses 

A. Regulatory Evaluation 

Changes to Federal regulations must 

undergo several economic analyses. 

First, Executive Order 12866 and 

Executive Order 13563 direct that each 

Federal agency shall propose or adopt a 

regulation only upon a reasoned 

determination that the benefits of the 

intended regulation justify its costs. 

Second, the Regulatory Flexibility Act 

of 1980 (Pub. L. 96–354) requires 

agencies to analyze the economic 

impact of regulatory changes on small 

entities. Third, the Trade Agreements 

Act (Pub. L. 96–39) prohibits agencies 

from setting standards that create 

unnecessary obstacles to the foreign 

commerce of the United States. In 

developing U.S. standards, this Trade 

Act requires agencies to consider 

international standards and, where 

appropriate, that they be the basis of 

U.S. standards. Fourth, the Unfunded 

Mandates Reform Act of 1995 (Pub. L. 

104–4) requires agencies to prepare a 

written assessment of the costs, benefits, 

and other effects of proposed or final 

rules that include a Federal mandate 

likely to result in the expenditure by 

state, local, or tribal governments, in the 

aggregate, or by the private sector, of 

$100 million or more annually (adjusted 

for inflation with base year of 1995). 

This portion of the preamble 

summarizes the FAA’s analysis of the 

economic impacts of this proposed rule. 

We suggest readers seeking greater 

detail read the full regulatory 

evaluation, a copy of which we have 

placed in the docket for this rulemaking. 

In conducting these analyses, FAA 

has determined that this proposed rule: 

(1) Has benefits that justify its costs; (2) 

is not an economically ‘‘significant 

regulatory action’’ as defined in section 

3(f) of Executive Order 12866; (3) is not 

‘‘significant’’ as defined in DOT’s 

Regulatory Policies and Procedures; (4) 

would not have a significant economic 

impact on a substantial number of small 

entities; (5) would not create 

unnecessary obstacles to the foreign 

commerce of the United States; and (6) 

would not impose an unfunded 

mandate on state, local, or tribal 

governments, or on the private sector by 

exceeding the threshold identified 

above. These analyses are summarized 

below. 

1. Total Benefits and Costs of This Rule 

This rule is a retrospective regulatory 

review rulemaking under Executive 

Order 13563. This rule would be 

relieving for both government and 

industries with the estimated net 

benefits. We assess regulatory benefits 

based on resources saved for reducing 

regulatory burden on both industry and 

the FAA. The total combined savings 

would be about $610 million or $450 

million present value at a 7% discount 

rate. The lower and the higher estimates 

of the total combined regulatory savings 

range from $384 million to $836 million 

(see table). The proposed rule would 

maintain a level of safety for fuel tank 

structure and system lightning 

protection consistent with that provided 

for other airplane hazards. 

Benefits (1 × million dollar) 

Value in 2014 dollar Present value at 7% 

Average Lower bound Upper bound Average Lower bound Upper bound 

Government benefits (sub-total) .......................... $0 .1 $0 .1 $0 .2 $0 .1 $0 .1 $0 .1 

Industries benefits (sub-total) .............................. 610 384 836 450 283 618 

Exemptions and special conditions .............. 30 17 44 21 12 30 

Productions ................................................... 570 361 779 423 267 579 

Operations .................................................... 10 6 13 6 4 9 

Total Societal Benefits ........................... 610 384 836 451 283 618 

2. Parties Potentially Affected by This 

Rulemaking 

• Part 25 airplane manufacturers. 

• Operators of part 25 airplanes. 

• The Federal Aviation 

Administration. 

3. Assumptions and Data Sources 

• Data related to industry savings 

mainly come from airplane 

manufacturers. 

• Data related to requests for 

exemptions and special conditions 

come from FAA internal data source 

and the agency’s experts judgments. 

• The FAA would process four 

special conditions and seven 

exemptions in the next ten years in the 

absence of this rule. 

• Domestic airplane manufacturers 

would petition for two special 

conditions and three exemptions before 

reaching their cost-benefit steadystate.13

• Approximately 184 airplanes would 

be produced per year for ten years based 

on airplane models being approved for 

exemptions and special conditions for 

lightning protection.14

• Computational weights of 

composite wing airplanes would change 

from current approximate 15%–25% 

level linearly increasing to 50% level for 

a ten-year production cycle.15

• Airplanes have service life-span for 

30 years.16

• Projected impacts on manufacturers 

and the government are for a ten-year 

period from 2015 to 2024. 

• All monetary values are expressed 

in 2014 dollars. 

B. Regulatory Flexibility Determination 

The Regulatory Flexibility Act of 1980 

(Pub. L. 96–354) (RFA) establishes ‘‘as a 

principle of regulatory issuance that 

agencies shall endeavor, consistent with 

the objectives of the rule and of 

applicable statutes, to fit regulatory and 

informational requirements to the scale 

of the businesses, organizations, and 

governmental jurisdictions subject to 

regulation.’’ To achieve this principle, 

agencies are required to solicit and 

consider flexible regulatory proposals 

and to explain the rationale for their 

actions to assure that such proposals are 

given serious consideration.’’ The RFA 

covers a wide range of small entities, 

including small businesses, not-forprofit organizations, and small 

governmental jurisdictions. 

Agencies must perform a review to 

determine whether a rule will have a 

significant economic impact on a 

substantial number of small entities. If 

the agency determines that it will, the 

agency must prepare a regulatory 

flexibility analysis as described in the 

RFA. 

However, if an agency determines that 

a rule is not expected to have a 

significant economic impact on a 

substantial number of small entities, 

section 605(b) of the RFA provides that 

the head of the agency may so certify 

and a regulatory flexibility analysis is 

mstockstill on DSK4VPTVN1PROD with PROPOSALS

75504 Federal Register / Vol. 79, No. 243 / Thursday, December 18, 2014 / Proposed Rules 

not required. The certification must 

include a statement providing the 

factual basis for this determination, and 

the reasoning should be clear. 

The proposed rule would amend 

certain airworthiness regulations that 

are not always practical for transport 

category airplanes regarding lightning 

protection of fuel tanks and systems. 

While the largest benefiters of this 

proposed rule would be airplane 

manufacturers, who are large entities, 

many small airline operators would also 

benefit from this proposed rule due to 

fuel savings. Therefore, as provided in 

section 605(b), the Administrator of the 

FAA certifies that the proposed rule 

would not have a significant economic 

impact on a substantial number of small 

entities and also certify that a regulatory 

flexibility analysis is not required. 

C. International Trade Impact 

Assessment 

The Trade Agreements Act of 1979 

(Pub. L. 96–39), as amended by the 

Uruguay Round Agreements Act (Pub. 

L. 103–465), prohibits Federal agencies 

from establishing standards or engaging 

in related activities that create 

unnecessary obstacles to the foreign 

commerce of the United States. 

Pursuant to these Acts, the 

establishment of standards is not 

considered an unnecessary obstacle to 

the foreign commerce of the United 

States, so long as the standard has a 

legitimate domestic objective, such as 

the protection of safety, and does not 

operate in a manner that excludes 

imports that meet this objective. The 

statute also requires consideration of 

international standards, and where 

appropriate, that they be the basis for 

U.S. standards. The FAA has assessed 

the potential effect of this proposed rule 

and determined that it could result in 

the same benefits or costs to domestic 

and international entities in accord with 

the Trade Agreements Act. 

D. Unfunded Mandates Assessment 

Title II of the Unfunded Mandates 

Reform Act of 1995 (Pub. L. 104–4) 

requires each Federal agency to prepare 

a written statement assessing the effects 

of any Federal mandate in a proposed or 

final agency rule that may result in an 

expenditure of $100 million or more (in 

1995 dollars) in any one year by state, 

local, and tribal governments, in the 

aggregate, or by the private sector; such 

a mandate is deemed to be a ‘‘significant 

regulatory action.’’ The FAA currently 

uses an inflation-adjusted value of $151 

million in lieu of $100 million. This 

proposed rule does not contain such a 

mandate; therefore, the requirements of 

Title II of the Act do not apply. 

E. Paperwork Reduction Act 

The Paperwork Reduction Act of 1995 

(44 U.S.C. 3507(d)) requires that the 

FAA consider the impact of paperwork 

and other information collection 

burdens imposed on the public. The 

FAA has determined that there would 

be no new requirement for information 

collection associated with this proposed 

rule. 

F. International Compatibility and 

Cooperation 

In keeping with U.S. obligations 

under the Convention on International 

Civil Aviation, it is FAA policy to 

conform to International Civil Aviation 

Organization (ICAO) Standards and 

Recommended Practices to the 

maximum extent practicable. The FAA 

has reviewed the corresponding ICAO 

Standards and Recommended Practices 

and has identified no differences with 

these proposed regulations. 

G. Environmental Analysis 

FAA Order 1050.1E identifies FAA 

actions that are categorically excluded 

from preparation of an environmental 

assessment or environmental impact 

statement under the National 

Environmental Policy Act in the 

absence of extraordinary circumstances. 

The FAA has determined this 

rulemaking action qualifies for the 

categorical exclusion identified in 

Section 312f of Order 1050.1E and 

involves no extraordinary 

circumstances. 

V. Executive Order Determinations 

A. Executive Order 13132, Federalism 

The FAA has analyzed this proposed 

rule under the principles and criteria of 

Executive Order 13132, Federalism. The 

agency has determined that this action 

would not have a substantial direct 

effect on the States, or the relationship 

between the Federal government and 

the States, or on the distribution of 

power and responsibilities among the 

various levels of government, and 

therefore, would not have Federalism 

implications. 

B. Executive Order 13211, Regulations 

That Significantly Affect Energy Supply, 

Distribution, or Use 

The FAA analyzed this proposed rule 

under Executive Order 13211, Actions 

Concerning Regulations that 

Significantly Affect Energy Supply, 

Distribution, or Use (May 18, 2001). The 

agency has determined that it would not 

be a ‘‘significant energy action’’ under 

the executive order and would not be 

likely to have a significant adverse effect 

on the supply, distribution, or use of 

energy. 

VI. Additional Information 

A. Comments Invited 

The FAA invites interested persons to 

participate in this rulemaking by 

submitting written comments, data, or 

views. The agency also invites 

comments relating to the economic, 

environmental, energy, or federalism 

impacts that might result from adopting 

the proposals in this document. The 

most helpful comments reference a 

specific portion of the proposal, explain 

the reason for any recommended 

change, and include supporting data. To 

ensure the docket does not contain 

duplicate comments, commenters 

should send only one copy of written 

comments, or if comments are filed 

electronically, commenters should 

submit only one time. 

The FAA will file in the docket all 

comments it receives, as well as a report 

summarizing each substantive public 

contact with FAA personnel concerning 

this proposed rulemaking. Before acting 

on this proposal, the FAA will consider 

all comments it receives on or before the 

closing date for comments. The FAA 

will consider comments filed after the 

comment period has closed if it is 

possible to do so without incurring 

expense or delay. The agency may 

change this proposal in light of the 

comments it receives. 

Proprietary or Confidential Business 

Information: Commenters should not 

file proprietary or confidential business 

information in the docket. Such 

information must be sent or delivered 

directly to the person identified in the 

FOR FURTHER INFORMATION CONTACT

section of this document and marked as 

proprietary or confidential. If submitting 

information on a disk or CD ROM, mark 

the outside of the disk or CD ROM and 

identify electronically within the disk or 

CD ROM the specific information that is 

proprietary or confidential. 

Under 14 CFR 11.35(b), if the FAA is 

aware of proprietary information filed 

with a comment, the agency does not 

place it in the docket. It is held in a 

separate file to which the public does 

not have access, and the FAA places a 

note in the docket that it has received 

it. If the FAA receives a request to 

examine or copy this information, it 

treats it as any other request under the 

Freedom of Information Act (5 U.S.C. 

552). The FAA processes such a request 

under Department of Transportation 

procedures found in 49 CFR part 7. 

mstockstill on DSK4VPTVN1PROD with PROPOSALS

Federal Register / Vol. 79, No. 243 / Thursday, December 18, 2014 / Proposed Rules 75505 

B. Availability of Rulemaking 

Documents 

An electronic copy of rulemaking 

documents may be obtained from the 

Internet by— 

1. Searching the Federal eRulemaking 

Portal (http://www.regulations.gov); 

2. Visiting the FAA’s Regulations and 

Policies Web page at http://www.faa.

gov/regulations_policies or 

3. Accessing the Government Printing 

Office’s Web page at http:// 

www.gpo.gov/fdsys/. 

Copies may also be obtained by 

sending a request to the Federal 

Aviation Administration, Office of 

Rulemaking, ARM–1, 800 Independence 

Avenue SW., Washington, DC 20591, or 

by calling (202) 267–9680. Commenters 

must identify the docket or notice 

number of this rulemaking. 

All documents the FAA considered in 

developing this proposed rule, 

including economic analyses and 

technical reports, may be accessed from 

the Internet through the Federal 

eRulemaking Portal referenced in item 

(1) above. 

List of Subjects in 14 CFR Part 25 

Aircraft, Aviation safety, Life-limited 

parts, Reporting and record keeping 

requirements. 

The Proposed Amendment 

In consideration of the foregoing, the 

Federal Aviation Administration 

proposes to amend chapter I of title 14, 

Code of Federal Regulations as follows: 

PART 25—AIRWORTHINESS 

STANDARDS: TRANSPORT 

CATEGORY AIRPLANES 

■ 1. The authority citation for part 25 

continues to read as follows: 

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

44702 and 44704. 

■ 2. Revise § 25.954 to read as follows: 

§ 25.954 Fuel system lightning protection. 

(a) The design and arrangement of a 

fuel system must prevent the ignition of 

fuel vapor within the system by— 

(1) Direct lightning strikes to areas 

having a high probability of stroke 

attachment; 

(2) Swept lightning strokes to areas 

where swept strokes are highly 

probable; 

(3) Lightning-induced or conducted 

electrical transients; and 

(4) Corona and streamering at fuel 

vent outlets. 

(b) The design and arrangement of a 

fuel system must ensure that 

catastrophic fuel vapor ignition is 

extremely improbable, taking into 

account flammability, critical lightning 

strikes, and failures within the fuel 

system. 

(c) To protect design features that 

prevent catastrophic fuel vapor ignition 

caused by lightning, the type design 

must include critical design 

configuration control limitations 

(CDCCLs) identifying those features and 

providing information on how to protect 

them. To ensure the continued 

effectiveness of those design features, 

the type design must also include 

inspection and test procedures, intervals 

between repetitive inspections and tests, 

and mandatory replacement times for 

those design features. The applicant 

must include the information required 

by this paragraph in the Airworthiness 

Limitations section of the instructions 

for continued airworthiness required by 

§§ 25.1529 and 25.1729. 

(d) For purposes of this section, a 

critical lightning strike is a lightning 

strike that attaches to the airplane in a 

location that affects a failed feature or a 

structural failure, and the amplitude of 

the strike is sufficient to create an 

ignition source when combined with 

that failure. A fuel system includes any 

component within either the fuel tank 

structure or the fuel tank systems, and 

any other airplane structure or system 

components that penetrate, connect to, 

or are located within a fuel tank. 

■ 3. Amend § 25.981 by revising the title 

of the section and paragraphs (a)(3) and 

(d) to read as follows: 

§ 25.981 Fuel tank explosion prevention. 

(a) * * * 

* * * * * 

(3) Except for ignition sources due to 

lightning addressed by § 25.954, 

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, taking into 

account the effects of manufacturing 

variability, aging, wear, corrosion, and 

likely damage. 

* * * * * 

(d) To protect design features that 

prevent catastrophic ignition sources 

within the fuel tank, and to prevent 

increasing the flammability exposure of 

the tanks above that permitted in 

paragraph (b) of this section, the type 

design must include critical design 

configuration control limitations 

(CDCCLs) identifying those features and 

providing instructions on how to protect 

them. To ensure the continued 

effectiveness of those features, and 

prevent degradation of the performance 

and reliability of any means provided 

according to paragraphs (a) or (c) of this 

section, the type design must also 

include necessary inspection and test 

procedures, intervals between repetitive 

inspections and tests, and mandatory 

replacement times for those features. 

The applicant must include information 

required by this paragraph in the 

Airworthiness Limitations section of the 

Instructions for Continued 

Airworthiness required by §§ 25.1529 

and 25.1729. The type design must also 

include the placement of visible means 

of identifying critical features of the 

design in areas of the airplane where 

foreseeable maintenance actions, 

repairs, or alterations may compromise 

the CDCCLs (e.g., color-coding of wire to 

identify separation limitation). The type 

design must identify these visible means 

as CDCCLs. 

■ 4. In appendix H to part 25, section 

H25.4, add new paragraph (a)(5) and 

new section H25.X to read as follows: 

Appendix H to Part 25—Instructions for 

Continued Airworthiness 

H25.4 Airworthiness Limitations section. 

(a) * * * 

* * * * * 

(5) Mandatory replacement times, 

inspection intervals, and related inspection 

and test procedures for each lightning 

protection feature approved under § 25.954. 

* * * * * 

H25.X Lightning Protection Features 

Instructions for Continued Airworthiness. 

The applicant must prepare instructions 

for continued airworthiness (ICA) applicable 

to lightning protection features for fuel tank 

structure and systems as required by § 25.954 

that are approved by the FAA and include 

sampling programs, maintenance, or 

inspections necessary for lightning protection 

features. 

Issued under authority provided by 49 

U.S.C. 106(f) and 44701(a) in Washington, 

DC, on December 9, 2014. 

Chris Carter, 

Acting Deputy Director, Aircraft Certification 

Office. 

[FR Doc. 2014–29385 Filed 12–17–14; 8:45 am] 

BILLING CODE 4910–13–P 

mstockstill on DSK4VPTVN1PROD with PROPOSALS