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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