Electrical and Electronic Systems Lightning Protection

[Docket No. 25912; Amdt No. 25-80]

RIN 2120-AC81

Electrical and Electronic Systems Lightning Protection

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: This amendment adds a new standard for electrical and

electronic systems installed in transport category airplanes. It is the

result of increasing concern for the vulnerability of these systems to

the indirect effects of lightning, and is intended to enhance safety by

providing specific lightning protection requirements for electrical and

electronic systems that perform essential or critical functions.

EFFECTIVE DATE: May 31, 1994.

FOR FURTHER INFORMATION CONTACT: Gene Vandermolen, FAA, Flight Test &

Systems Branch, ANM-111, Transport Airplane Directorate, Aircraft

Certification Service, 1601 Lind Avenue SW., Renton, Washington 98055-

4056; telephone (206) 227-2135.

SUPPLEMENTARY INFORMATION:

Background

This amendment is based on Notice of Proposed Rulemaking (NPRM) No.

89-15, which was published in the Federal Register on May 30, 1989 (54

FR 23164).

As discussed in the notice, concern for the vulnerability of

airplane electronic systems to the effects of lightning has increased

substantially over the past few years. The use of solid-state

components in the design of electronic control systems in airplanes has

made such systems potentially susceptible to transient effects of

induced electrical current and voltage caused by a direct lightning

strike to the airplane. These induced transient currents and voltages

can degrade electronic system performance by damaging components or

upsetting system functions. Component damage means a permanently

altered electrical characteristic that can include dielectric

breakdowns and effects from heat in semiconductor junctions, resistors,

and component interconnections. Function upset refers to an impairment

of system operation, either permanent or momentary (e.g., a change of

digital or analog state), that includes logic changes in computer and

processing systems, electronic engine and flight controls, and power

generating and distribution systems.

Another factor that has contributed to this increased concern is

the reduced electromagnetic shielding afforded airplane electronic

systems by advanced technology airframe materials. Some of these

materials have no electrical conductivity and lightning strikes often

puncture them, resulting in extensive damage and allowing lightning to

attach to vulnerable electronic systems or components located within

the airframe. Other materials, such as graphite-reinforced composites,

have some electrical conductivity. Voltages induced by lightning

current that flows in airframe components made of these composite

materials are much higher than those in aluminum materials because the

electrical resistance of composites is higher; therefore, such

composites provide much less protection to the circuits and electronic

systems in the airplane.

There are two sections in 14 CFR part 25 that specifically pertain

to lightning protection: one for the airframe in general (Sec. 25.581),

and the other for the fuel system (Sec. 25.954). There are no

regulations dealing specifically with lightning protection of

electrical and electronic systems. The advent of advanced electronic

systems in airplane designs submitted for FAA approval requires that

additional consideration be given to protecting these systems from the

effects of lighting strikes. Although Sec. 25.581(a) (structures

subpart) requires that an airplane be protected against catastrophic

effects of lighting, and Sec. 25.1309(a) states that required systems

must operate properly in all environmental conditions, it has been

determined that the existing lightning protection requirements are not

adequate for advanced electronic systems.

In recent type certification programs involving advanced electronic

systems, such as those used in the Airbus A320, Boeing 747-400, and

Douglas MD-11 airplanes, the FAA has adopted special conditions to

provide an adequate level of safety.

Since trends indicate that future airplane designs will incorporate

similar systems, the FAA has determined that a change in the design

standards of part 25 is necessary.

Discussion of Comments

The following discussion summarizes the comments received from the

public, industry, foreign authorities, and manufacturers in response to

Notice 89-15.

Several commenters request clarification as to what constitutes

critical and essential functions.

The terms ``critical'' and ``essential'' originated when attempts

were made to classify failure conditions in accordance with

Sec. 25.1309. This regulation requires that systems be designed so that

the occurrence of any failure condition that would prevent the

continued safe flight and landing of the airplane is extremely

improbable. The function affected by such a failure condition is deemed

``critical.'' Additionally, Sec. 25.1309 requires that systems be

designed so that the occurrence of any other failure condition that

would reduce the capability of the airplane or the ability of the crew

to cope with adverse operating conditions is improbable. The function

affected by such a failure condition is deemed ``essential.'' The

combination of systems or system redundancy required to meet these

reliability requirements is determined by conducting a preliminary

hazard analysis or criticality assessment. Examples of systems that

perform critical functions are full authority electronic engine

controls, electronic primary flight controls, primary flight displays,

and electronic stability augmentation. Examples of systems that perform

essential functions are communications systems, navigation systems, and

flight management systems.

One commenter considers the lightning protection requirements to be

unclear when applied to individual subsystems prior to installation in

the airplane, and recommends that the relationship between the airframe

manufacturer and the subsystem supplier to clarified. The commenter

contends that the proposed rule appears to suggest that all systems

that perform critical functions would be required to withstand the full

direct strike currents, without taking into account any reduction in

these currents due to the shielding provided by the airframe.

As discussed in the NPRM, the purpose of the proposed regulation is

to require lightning protection for electrical and electronic systems

that perform critical and essential functions when installed in an

airplane. Protection may be provided by the airplane structure,

shielding of the wiring, and enclosures of the individual subsystems.

The level of protection needed for subsystems is generally specified by

the airframe manufacturer. In the past, when the airframe manufacturer

did not specify the level of protection needed, Radio Technical

Commission for Aeronautics (RTCA) Document DO-160, Section 22,

``Lightning Induced Transient Susceptibility,'' was used to provide

guidance. While Section 22 of DO-160 is incomplete, it is currently

being revised to include the effects of multiple burst and multiple

stroke test waveforms so as to be in agreement with FAA Advisory

Circular 20-136, ``Protection of Aircraft Electrical/Electronic Systems

Against the Indirect Effects of Lightning,'' dated March 5, 1990, and

Society of Automotive Engineers (SAE Committee Report AE4L-87-3,

Revision B, dated January 1989. Until the DO-160 revision has been

completed, the test and analyses described in the advisory circular

should be used to qualify subsystems. The test waveforms presented in

Appendix III of the advisory circular represent a severe natural

lightning environment, including the multiple stroke and multiple burst

criteria, that is external to the airplane and that may be used by

certification purposes in accessing the induced effects of lightning.

The equipment should be protected to the appropriate test level, as

specified in Appendix IV of the advisory circular, for the proposed

airplane installations so that the subsystems are able to continue to

perform their intended functions after the tests are conducted.

Two commenters suggest that the definitions of the terms

``critical'' and ``essential'' functions be removed from the proposed

rule and placed in 14 CFR part 1 of the FAR, Definitions and

abbreviations.

The FAA does not concur with this suggestion. The terms

``critical'' and ``essential,'' as used in the proposed rule, have a

unique definition based on Secs. 25.1309 (b)(1) and (b)(2) that may be

inappropriate when used in other rules. Commenters have expressed

confusion over the use of these terms; therefore, the definitions of

``critical'' and ``essential'' functions have been integrated into the

wording of the rule so as not to require separate definitions.

One commenter suggests that the words ``contribute to or'' be

removed from the definitions for critical and essential functions given

in proposed Secs. 25.1315 (c)(1) and (c)(2) because this terminology is

undefined and can be subject to broad interpretation.

The FAA does not concur. This terminology is consistent with that

used in existing regulations and is generally understood by the

aviation industry. It is used in this rule to convey that although a

failure by itself may not be catastrophic or major, it may be a

contributing factor when combinations of failures are considered. For

example, a latent or undetected failure could contribute to a hazardous

failure condition when combined with one or more specific failures or

events. Also, systems that perform only non-essential functions could

contribute to a failure condition involving an non-essential or

critical function.

The same commenter also suggests that the words ``significantly

impact the safety,'' in proposed Sec. 25.1315(c)(2), be changed to

``reduce the capability'' for consistency with Sec. 25.1309(b)(2).

The FAA concurs with this recommendation, and Sec. 25.1315(c)(2),

now designated as Sec. 25.1315(b), has been revised accordingly.

Several commenters request clarification as to exactly what is

meant by the statement that critical functions are ``not affected'' by

the lightning encounter.

The FAA concurs that clarification of ``not affected'' is needed;

therefore, the final rule has been revised to read, ``not adversely

affected'' in an attempt to convey this intent. Although the words

``not affected'' were used in the proposed rule, the FAA did not intend

that the requirement be rigidly applied. The intent of the regulation

is to require lightning protection for systems that perform critical

functions to the extent that the critical functions are not adversely

affected by the lightning event. Determination of when functions are

adversely affected would be made by the cognizant FAA Aircraft

Certification Office based on rational engineering judgment on a case-

by-case evaluation of the specified function and the ``effect''

presented. Literally applying a standard of ``no effect'' would not be

reasonable. In determining compliance with special conditions in past

certification programs, the FAA has accepted upsets of a minor nature

that do not result in significant fluctuations of control surface

position or engine thrust. Any effect perceived by the flightcrew would

need to be evaluated to ensure that it would not lead to a hazardous

condition. For example, some full authority digital engine control

(FADEC) systems are designed with two fully redundant channels, either

of which can control the engine independently. In addition, the logic

within the FADEC will monitor each channel and, by design, switch

channels if an anomaly appears on the selected channel. This does not

necessarily mean that the channel is no longer functional or has

degraded, because if the backup channel were not functional, the

selected channel would continue in control. Therefore, it would not be

considered an adverse effect if a channel transfer in such a system

occurred in accordance with its accepted design when the airplane is

exposed to the lightning test waveforms. However, additional tests may

be required to demonstrate that neither channel would be adversely

affected when tested individually. For example, a mode change within a

given channel that could result in the loss of a primary thrust setting

parameter, resulting in the possibility of a change in thrust level,

would not be acceptable. Internal monitors that indicate normal

operation of critical systems must not be damaged by the effects of

lightning.

Other examples of adversely affected critical functions are

hazardously misleading primary flight information, uncommanded flap

motion and, of course, loss of primary flight controls in a fly-by-wire

airplane.

Determination of adverse effects will be handled on a case-by-case

basis subject to the explanation given above. Perturbations or

deviations that exceed tolerances agreed upon in the test plan must be

reported to the FAA for evaluation.

The same commenters also suggest that adequate lightning protection

is provided if the airplane is still capable of continued safe flight

and landing after the lightning encounter.

The FAA does not agree that the concept of continued safe flight

and landing is sufficient. The FAA has concluded that a higher level of

safety is required for systems that perform critical functions when

exposed to adverse environmental conditions. This concept would be

violated, for example, if engine failure from an expected environmental

condition, such as a lightning strike, were allowed because any

environmental condition that may adversely affect an engine design must

be assumed to affect all the engines on the airplane. For this reason,

engines, as installed, must be able to tolerate these conditions

without damage or serious loss of thrust. This same line of reasoning

applies to other systems that perform critical functions. Lightning

strikes to airplanes are unpredictable as to their strength, duration,

and number. Therefore, continued safe flight and landing of the

airplane after multiple lightning strikes could not be assured unless

systems that perform critical functions have a high degree of tolerance

to the expected lightning strike environment. This basic environmental

requirement also applies to other environmental conditions, such as

icing, hail, heavy rain, bird flocks, etc.

One commenter proposes new wording for Sec. 25.1315(a) that would

allow crew action to restore critical systems that have been disrupted

by lightning induced transients.

The FAA does not concur. Critical function disruption must be

automatically restored after the lightning encounter. Under certain

flight conditions, such as during takeoff or landing in instrument

meteorological conditions when the crew workload is high, the crew may

not be able to restore the critical function in time to prevent a

catastrophic even from occurring. The FAA allows crew action to restore

systems that perform essential functions; however, systems that perform

critical functions must recover automatically.

The majority of commenters do not agree that the test waveforms

should be contained in an appendix to part 25, as proposed in the

notice. They contend that this information should be presented in an

advisory circular. Several commenters believe that there will be

additional adjustments to the description of the lightning environment

as knowledge of the phenomena increases, and that an advisory circular

would be easier to revise than an appendix to the FAR. In addition,

they argue that the FAA should not be legally bound by the criteria in

an appendix if a change to the description of the environment is

appropriate.

The FAA concurs that the proposed appendix should not be adopted.

As noted by several commenters, the information contained in the

proposed appendix was taken from SAE Report AE4L-87-3, Revision A,

entitled ``Protection of Aircraft Electrical/Electronic Systems Against

the Indirect Effects of Lightning,'' dated October 1988. After the

notice was published, the AE4L Committee added clarifications of the

environment definition, including some boundaries on pulse spacing in

the multiple burst and multiple stroke environments. These have been

incorporated in Revision B of the SAE document issued in January 1989.

Because of the potential for further adjustments in the environment

definition, and because use of the description of the environment set

forth in the proposed Appendix J is only one means of showing

compliance with this rule, the FAA concurs that it would be more

appropriate to present this information in an advisory circular. This

is also consistent with the FAA's practice of publishing technical

guidance/procedures for implementing a particular regulation in an

advisory circular. As noted earlier, the idealized waveforms are

currently covered in AC 20-136. Accordingly, proposed Appendix J to

part 25 has been removed from the final rule. However, to provide

guidelines as to what is involved in showing compliance with the rule,

general criteria are added to Sec. 25.1315 as paragraph (c). A detailed

discussion of these criteria is provided in AC 20-136.

Two commenters consider the definition of the environment given in

the proposed Appendix to be unrealistic and propose several changes to

the idealized test waveforms.

The FAA does not concur that this definition is unrealistic. The

FAA has worked closely with SAE Committee AE4L in developing the

idealized test waveforms that are presented in Revision B of Report

AE4L-87-3. The FAA has adopted these waveforms as acceptable

representations of a severe natural lightning environment for

certification purposes and has included them in AC 20-136. The proposed

changes submitted by the commenters have been forwarded to the AE4L

Committee for consideration. The FAA will consider appropriate changes

to the definition of the waveforms in the AC if the Committee

recommends them.

Two commenters object to statements in the background and

discussion of the NPRM that new generation systems and airframes are

more vulnerable to the indirect effects of lightning than previous

designs.

The FAA agrees that new generation systems are not necessarily more

vulnerable to the indirect effects of lightning if proper design,

shielding, and grounding techniques are used. However, the use of

sensitive electronics that respond to low level voltage commands makes

these systems potentially more vulnerable if they are not properly

designed and shielded. Reduced electromagnetic shielding provided by

nonmetallic airframe materials also raises the potential for system

interference from lightning. The intent of these new lightning

protection requirements is to maintain the level of safety that is

inherent in the older airplane designs.

Two commenters point out that preamble statements are vital to

defining logical, usable, and economically feasible rules, and suggest

that specific technologies, system architectures, and function

susceptibility criteria must be provided instead of generalities if the

FAA desires to justify the rule on a sound technical basis.

The FAA does not concur. In order to avoid stifling innovation, the

FAA specifies the required safety objective in a regulation rather than

dictating specific design details, whenever possible. In accordance

with long-standing certification practice, system technologies and

architectures are proposed by the applicant, allowable function

susceptibility is determined on a case-by-case basis by the local

cognizant FAA certification office using published FAA policy and

engineering judgment.

One commenter expresses concern that application of the proposed

rule to existing airplanes could present problems for supplemental type

certification (STC) applicants when new systems are installed. Many

airlines, for example, do not have the capability to demonstrate

compliance.

The FAA considers lightning to be an environmental condition that

must be taken into consideration to assure confidence of safe operation

when a new system is installed in an airplane. Equipment manufacturers

have historically used the test procedures in RTCA Document DO-160 to

qualify their equipment to environmental conditions. The capability of

the equipment to meet the tests described in this document establishes

a minimum level of protection for system components. Additional

protection may be provided by the airframe materials, shielding of wire

bundles, proper equipment grounding, etc. In addition to bench tests, a

determination should be made that systems that perform critical and

essential functions, as installed in a given airplane, are provided

with adequate protection, including margins, and that installation

level testing and/or verified analysis is adequate. This determination

is made by the cognizant FAA Aircraft Certification Office, based on

guidance contained in AC 20-136, and sound engineering judgment. In

addition, the FAA has issued special conditions for new systems in

existing airplanes under the provisions of Sec. 21.101(b)(2). The

extent of review required for a system installed in existing airplanes

will depend on the type of system, installation considerations such as

type of airplane, airframe materials (metallic or composite), service

experience in ``similar'' airplanes, and other factors. These

evaluations should be reviewed with the cognizant FAA Aircraft

Certification Office so that the FAA and the applicant can agree on a

certification plan.

One commenter states that the proposed requirement for lightning

protection of essential systems is not justified and should not be

adopted.

The FAA disagrees with this comment. Lightning encounters, even

though infrequent , do occur. Therefore, a degree of protection is

required commensurate with the criticalness of the function that the

system performs. Protection requirements are much less stringent for

systems that perform essential functions than for those that perform

critical functions. System components may be damaged as long as the

function can be recovered after the lightning encounter. The

justification for imposing requirements for systems that perform

essential functions is that loss of function would unacceptably

decrease the inherent level of safety of the airplane.

One commenter questions whether manufacturers would be responsible

for testing and recertifying critical electronic control systems now in

service.

The new lightning protection requirements apply to systems that

perform critical and essential functions of which design approval is

sought after the effective date of the rule. Recertificating in-service

units is not required. If an in-service problem that affects the safety

of the airplane were discovered, an airworthiness directive would be

issued requiring corrective action.

One commenter does not consider that the imposition of additional

lightning protection requirements on systems of conventional design is

justified if service history has shown that they are insensitive to

lightning transients.

The FAA does not intend to impose additional lightning protections

requirements on systems using standard designs and installation that

can be shown to have an inherent history of acceptability. It is FAA

policy to accept similarity with previously proven installation

designs, simulated lightning tests, or acceptable analysis. Individual

designs should be reviewed by the cognizant FAA Aircraft Certification

Office.

Several commenters disagree that the incremental cost of

implementing the new rule will be zero. These comments and the FAA's

response are addressed in the Regulatory Evaluation discussion that

follows.

Notice 89-15 proposed that the lightning protection standard be

adopted as Sec. 25.1315 of the FAR. The paragraph used for the final

rule was changed to Sec. 25.1316 so that a future conflict could be

avoided in the event the FAA determines that JAR 25.1315, ``Negative

Acceleration,'' should be adopted.

Regulatory Evaluation

This section summarizes the full regulatory evaluation prepared by

the FAA that provides detailed estimates of the economic consequences

of this regulatory action. This summary and the full evaluation

quantify, to the extent practicable, estimated costs and anticipated

benefits to the private sector, consumers, and Federal, state, and

local governments.

Proposed changes to Federal regulations must undergo several

economic analyses. First, Executive Order 12866 directs 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 requires agencies

to analyze the economic impact of regulatory changes on small entities.

Finally, the Office of Management and Budget directs agencies to assess

the effects of regulatory changes on international trade. In conducting

these analyses, the FAA has determined that this rule: (1) will

generate benefits that justify its costs and is not a ``significant

regulatory action'' as defined in the Executive Order; (2) is not

significant as defined in Department of Transportation Regulatory

Policies and Procedures; (3) will not have a significant economic

impact on a substantial number of small entities; and (4) will not have

a negative impact on international trade. These analyses, available in

the docket, are summarized below.

Costs

The costs of the rule will essentially equal the costs that would

have been incurred by manufacturers in complying with requirements

imposed as special conditions in the absence of this rule. The new

standards will be no more stringent than those imposed through recent

special conditions, which are consistent with FAA Advisory Circular 20-

136, ``Protection of Aircraft Electrical/Electronic Systems Against the

Indirect Effects of Lightning,'' dated March 1990, and SAE Committee

Report AE4L-87-3, Revision B, dated January 1989. Given the novel

design features of advanced electronic systems and their susceptibility

to lightning strikes, the FAA would have continued to require adequate

lightning protection for all new certifications through imposition of

special conditions; consequently, this rule imposes no new incremental

costs.

Notwithstanding this cost perspective, the FAA has evaluated the

costs of the rule apart from the existence of special conditions, i.e.,

under the assumption that the reference level of costs prior to this

rule is zero.

The relative costs of the final rule are summarized below for two

type-certifications--a representative part 25 large transport category

airplane (i.e., air carrier), and a representative part 25 small

transport category airplane (i.e., a business or commuter jet).

Based on manufacturers' experiences with special condition

requirements and other relevant data, nonrecurring testing costs for a

representative large transport category airplane are estimated to total

$6,300,000, consisting of $2,000,000 for avionics equipment, $200,000

for engine controls, and $4,100,000 for airframes. Recurring

modification costs for each airplane produced are estimated to average

$50,000 for avionics, $35,000 for engine controls, and $12,600 for the

airframes, totalling $97,600 per airplane. Assuming 50 airplanes are

produced each year over a 10 year period (1995-2004), recurring

modification costs total $48,800,000. Thus, the costs to meet the

lightning protection requirements for certification of a representative

large transport category airplane total $55.1 million in nondiscounted

1990 dollars, or $27.7 million when discounted to 1991 present value.

For a representative small transport category airplane,

nonrecurring testing costs are estimated to total $980,000, consisting

of $630,000 for avionics, $150,000 for engine controls, and $200,000

for airframes. Recurring modification costs for each airplane produced

are estimated to average $25,000 for avionics, $8,000 for engine

controls, and $9,000 for airframes. Assuming production of 50 airplanes

per year for 10 years (1995-2004), recurring modification costs total

$21.0 million. Thus, the costs to meet the lightning protection

requirements for certification of a part 25 small transport category

airplane total approximately $22.0 million in nondiscounted 1990

dollars, or $10.5 million when discounted to 1991 present value.

Benefits

The benefits attributable to the rule are the prevented fatalities,

injuries, and airplane damage that might otherwise be caused by the

adverse indirect effects of lightning strikes on airplane electronic

systems. Information from the FAA Accident/Incident Data System

indicates that, from 1985 through 1990, there were two incidents

involving part 25 airplanes (both were large transport category

airplanes) in which the indirect effects of lightning strikes adversely

affected electronic systems. In each case, the airplane landed safely

with minimum damage. In one incident, the first officer's flight

instruments were lost, and in the second a partial electrical failure

occurred. Neither of the two airplanes affected were certificated

within the last five years, and therefore few sophisticated electronic

systems were involved. Lightning protection requirements imposed

through special conditions (since 1986) have substantially reduced the

probability that indirect effects of lightning would disrupt electronic

systems. Consequently, incidents involving more recent certifications

that include advanced electronic systems have not occurred. Given the

complexities of the more advanced electronic systems and their

increased vulnerability to lightning impacts, inadequate protection of

the systems would result in increased risks of operational failure.

As the number of flights increases through normal growth in air

traffic, the overall number of potential lightning strikes increases

accordingly. Each transport category airplane experiences, on average,

1.25 lightning strikes during each year of operation. Thus, between

15,000 and 16,000 lightning strikes could be expected during the

operating lives of the airplanes produced under one typical part 25

certification (i.e., 500 airplanes x 1.25 x 25 years). Since two

incidents affecting less advanced systems occurred over a recent five

year period, it is not unreasonable to postulate that at least this

number could occur during a future five year period. Given the advanced

systems' lower tolerance thresholds for disruptions and the

criticalness of their effect on safe flight and operation, events that

were incidents in the past could be accidents in the future.

The FAA has estimated the minimum levels of averted losses (in

terms of avoided fatalities and airplane damage) that would be

necessary to offset the expected costs of complying with the rule. For

a representative part 25 large transport category airplane

certification, the requirements will be cost-beneficial if one averted

accident prevents 91 fatalities and the destruction of the airplane.

For a representative part 25 small transport category airplane

certification, the rule will be cost-beneficial if 2 averted accidents

prevent 36 fatalities and 2 destroyed airplanes. For the reasons

outlined above, the FAA expects that the new requirements will prevent

at least the minimum number of accidents specified and therefore

considers the rule to be cost beneficial.

Regulatory Flexibility Determination

The Regulatory Flexibility Act of 1980 (RFA) was enacted by

Congress to ensure that small entities are not unnecessarily and

disproportionately burdened by government regulations. The RFA requires

agencies to review rules that may have ``a significant economic impact

on a substantial number of small entities.''

The rule will affect transport category airplane manufacturers.

None of these manufacturers is considered to be a small entity in

accordance with FAA criteria which states that a small manufacturer is

one with 75 employees or less. Therefore, this rule will not have a

significant economic impact on a substantial number of small entities.

International Trade Impact Assessment

The rule will have little or no impact on trade for either American

firms doing business in foreign countries or foreign firms doing

business in the United States. In the U.S., foreign manufacturers will

have to meet U.S. requirements, and thus will gain no competitive

advantage. In foreign countries, American manufacturers need not comply

with these requirements if the foreign country does not require them

and, therefore, will not be placed at a competitive disadvantage

relative to foreign manufacturers.

Federalism Implications

The regulations adopted herein will not have substantial direct

effects on the States, on the relationship between the national

government and the States, or on the distribution of power and

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this

regulation does not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment.

Conclusion

For the reasons given above, the FAA has determined that this

regulation is not significant under Executive Order 12866. In addition,

the FAA has determined that this action is not significant as defined

in Department of Transportation Regulatory Policies and Procedures (44

FR 11034, February 26, 1979). Since the aircraft involved are not

manufactured by small entities, the FAA certifies, under the criteria

of the Regulatory Flexibility Act, that this regulation will not have a

significant economic impact, positive or negative, on a substantial

number of small entities. A copy of the regulatory evaluation prepared

for this regulation may be examined in the public docket or obtained

from the person identified under the caption, FOR FURTHER INFORMATION

CONTACT.

List of Subjects in 14 CFR Part 25

Aircraft, Aviation safety, Federal Aviation Administration,

Reporting and recordkeeping requirements.

The Amendment

In consideration of the foregoing, the Federal Aviation

Administration amends 14 CFR part 25 of the Federal Aviation

Regulations (FAR) 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. 1344, 1354(a), 1355, 1421, 1423, 1425,

1428, 1429, 1430); 49 U.S.C. 106(g); and 49 CFR 1.47(a).

2. A new Sec. 25.1316 is added under the undesignated center

heading ``General'' to read as follows:

Sec. 25.1316 System lightning protection.

(a) For functions whose failure would contribute to or cause a

condition that would prevent the continued safe flight and landing of

the airplane, each electrical and electronic system that performs these

functions must be designed and installed to ensure that the operation

and operational capabilities of the systems to perform these functions

are not adversely affected when the airplane is exposed to lightning.

(b) For functions whose failure would contribute to or cause a

condition that would reduce the capability of the airplane or the

ability of the flightcrew to cope with adverse operating conditions,

each electrical and electronic system that performs these functions

must be designed and installed to ensure that these functions can be

recovered in a timely manner after the airplane is exposed to

lightning.

(c) Compliance with the lightning protection criteria prescribed in

paragraphs (a) and (b) of this section must be shown for exposure to a

severe lightning environment. The applicant must design for and verify

that aircraft electrical/electronic systems are protected against the

effects of lightning by:

(1) Determining the lightning strike zones for the airplane;

(2) Establishing the external lightning environment for the zones;

(3) Establishing the internal environment;

(4) Identifying all the electrical and electronic systems that are

subject to the requirements of this section, and their locations on or

within the airplane;

(5) Establishing the susceptibility of the systems to the internal

and external lightning environment;

(6) Designing protection; and

(7) Verifying that the protection is adequate.

Issued in Washington, DC, on April 20, 1994.

David R. Hinson,

Administrator.

[FR Doc. 94-10169 Filed 4-26-94; 8:45 am]

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