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373 

Federal Aviation Administration, DOT 

§ 25.1707 

(1) Electrical equipment or avionics 

that are qualified to environmental 
conditions and testing procedures when 
those conditions and procedures are— 

(i) Appropriate for the intended func-

tion and operating environment, and 

(ii) Acceptable to the FAA. 
(2) Portable electrical devices that 

are not part of the type design of the 
airplane. This includes personal enter-
tainment devices and laptop com-
puters. 

(3) Fiber optics. 

§ 25.1703

Function and installation: 

EWIS. 

(a) Each EWIS component installed 

in any area of the aircraft must: 

(1) Be of a kind and design appro-

priate to its intended function. 

(2) Be installed according to limita-

tions specified for the EWIS compo-
nents. 

(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: 

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374 

14 CFR Ch. I (1–1–24 Edition) 

§ 25.1709 

(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 
adequate physical separation from hy-
draulic lines and other hydraulic sys-
tem components, so that: 

(1) An EWIS component failure will 

not create a hazardous condition. 

(2) Any hydraulic fluid leakage onto 

EWIS components will not create a 
hazardous condition. 

(g) Except to the extent necessary to 

provide electrical connection to the ox-
ygen systems components, EWIS must 
be designed and installed with ade-
quate physical separation from oxygen 
lines and other oxygen system compo-
nents, so that an EWIS component fail-
ure will not create a hazardous condi-
tion. 

(h) Except to the extent necessary to 

provide electrical connection to the 
water/waste systems components, 
EWIS must be designed and installed 
with adequate physical separation from 
water/waste lines and other water/ 
waste system components, so that: 

(1) An EWIS component failure will 

not create a hazardous condition. 

(2) Any water/waste leakage onto 

EWIS components will not create a 
hazardous condition. 

(i) EWIS must be designed and in-

stalled with adequate physical separa-
tion between the EWIS and flight or 
other mechanical control systems ca-
bles and associated system compo-
nents, so that: 

(1) Chafing, jamming, or other inter-

ference are prevented. 

(2) An EWIS component failure will 

not create a hazardous condition. 

(3) Failure of any flight or other me-

chanical control systems cables or sys-
tems components will not damage the 
EWIS and create a hazardous condi-
tion. 

(j) EWIS must be designed and in-

stalled with adequate physical separa-
tion between the EWIS components 
and heated equipment, hot air ducts, 
and lines, so that: 

(1) An EWIS component failure will 

not create a hazardous condition. 

(2) Any hot air leakage or heat gen-

erated onto EWIS components will not 
create a hazardous condition. 

(k) For systems for which redun-

dancy is required, by certification 
rules, by operating rules, or as a result 
of the assessment required by § 25.1709, 
EWIS components associated with 
those systems must be designed and in-
stalled with adequate physical separa-
tion. 

(l) Each EWIS must be designed and 

installed so there is adequate physical 
separation between it and other air-
craft components and aircraft struc-
ture, and so that the EWIS is protected 
from sharp edges and corners, to mini-
mize potential for abrasion/chafing, vi-
bration damage, and other types of me-
chanical damage. 

§ 25.1709

System safety: EWIS. 

Each EWIS must be designed and in-

stalled so that: 

(a) Each catastrophic failure condi-

tion— 

(1) Is extremely improbable; and 
(2) Does not result from a single fail-

ure. 

(b) Each hazardous failure condition 

is extremely remote. 

§ 25.1711

Component identification: 

EWIS. 

(a) EWIS components must be labeled 

or otherwise identified using a con-
sistent method that facilitates identi-
fication of the EWIS component, its 
function, and its design limitations, if 
any. 

(b) For systems for which redundancy 

is required, by certification rules, by 

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