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14 CFR Ch. I (1–1–19 Edition)
§ 25.1705
(3) Perform the function for which it
was intended without degrading the
airworthiness of the airplane.
(4) Be designed and installed in a way
that will minimize mechanical strain.
(b) Selection of wires must take into
account known characteristics of the
wire in relation to each installation
and application to minimize the risk of
wire damage, including any arc track-
ing phenomena.
(c) The design and installation of the
main power cables (including generator
cables) in the fuselage must allow for a
reasonable degree of deformation and
stretching without failure.
(d) EWIS components located in
areas of known moisture accumulation
must be protected to minimize any
hazardous effects due to moisture.
§ 25.1705
Systems and functions: EWIS.
(a) EWIS associated with any system
required for type certification or by op-
erating rules must be considered an in-
tegral part of that system and must be
considered in showing compliance with
the applicable requirements for that
system.
(b) For systems to which the fol-
lowing rules apply, the components of
EWIS associated with those systems
must be considered an integral part of
that system or systems and must be
considered in showing compliance with
the applicable requirements for that
system.
(1) § 25.773(b)(2)
Pilot compartment
view.
(2) § 25.981
Fuel tank ignition pre-
vention.
(3) § 25.1165
Engine ignition systems.
(4) § 25.1310
Power source capacity
and distribution.
(5) § 25.1316
System lightning protec-
tion.
(6) § 25.1331(a)(2)
Instruments using a
power supply.
(7) § 25.1351
General.
(8) § 25.1355
Distribution system.
(9) § 25.1360
Precautions against in-
jury.
(10) § 25.1362
Electrical supplies for
emergency conditions.
(11) § 25.1365
Electrical appliances,
motors, and transformers.
(12) § 25.1431(c) and (d)
Electronic
equipment.
§ 25.1707
System separation: EWIS.
(a) Each EWIS must be designed and
installed with adequate physical sepa-
ration from other EWIS and airplane
systems so that an EWIS component
failure will not create a hazardous con-
dition. Unless otherwise stated, for the
purposes of this section, adequate
physical separation must be achieved
by separation distance or by a barrier
that provides protection equivalent to
that separation distance.
(b) Each EWIS must be designed and
installed so that any electrical inter-
ference likely to be present in the air-
plane will not result in hazardous ef-
fects upon the airplane or its systems.
(c) Wires and cables carrying heavy
current, and their associated EWIS
components, must be designed and in-
stalled to ensure adequate physical
separation and electrical isolation so
that damage to circuits associated
with essential functions will be mini-
mized under fault conditions.
(d) Each EWIS associated with inde-
pendent airplane power sources or
power sources connected in combina-
tion must be designed and installed to
ensure adequate physical separation
and electrical isolation so that a fault
in any one airplane power source EWIS
will not adversely affect any other
independent power sources. In addition:
(1) Airplane independent electrical
power sources must not share a com-
mon ground terminating location.
(2) Airplane system static grounds
must not share a common ground ter-
minating location with any of the air-
plane’s independent electrical power
sources.
(e) Except to the extent necessary to
provide electrical connection to the
fuel systems components, the EWIS
must be designed and installed with
adequate physical separation from fuel
lines and other fuel system compo-
nents, so that:
(1) An EWIS component failure will
not create a hazardous condition.
(2) Any fuel leakage onto EWIS com-
ponents will not create a hazardous
condition.
(f) Except to the extent necessary to
provide electrical connection to the
hydraulic systems components, EWIS
must be designed and installed with
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