[Federal Register Volume 59, Number 81 (Thursday, April 28, 1994)]
[Unknown Section]
[Page ]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-10169]
[Federal Register: April 28, 1994]
_______________________________________________________________________
Part X
Department of Transportation
_______________________________________________________________________
Federal Aviation Administration
_______________________________________________________________________
14 CFR Part 25
Electrical and Electronic Systems Lightning Protection; Final Rule
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[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]
BILLING CODE 4910-13-M