Cessna 170 Service Manual
Electrical System
15
or in long, open runs in the airframe, is designed to withstand normal
aircraft environment without
sleaving, jacketing, or other protection. Care must be taken in making all installations because no
wire insulation or jacketing will withstand continuous scuffing or abrasion.
Authors Note: The following wire sizes information is based upon wire meeting MIL -W-22759/16 (tin-
plated copper with ETFE insulation) in lengths of 25 feet or less for non-intermittent circuits at 14
volts.
Battery cables
are used for starting only intermittently and therefore may be somewhat smaller gauge than
the 300 Amp and greater currents sometimes generated during start. Therefore, to save weight and costs
Cessna originally provided battery cables of 4 gauge. It is recommended that larger gauges be considered
for replacement purposes. Sizes 1 or 1/O is recommended for the short runs from battery to solenoid to
starter terminal lug, and from battery negative terminal to aircraft ground as well as from the Ground
receptacle to the battery solenoid.
SPLICES IN ELECTRIC WIRE
. Splicing of electric wire should be kept to a minimum and avoided entirely in
locations subject to extreme vibrations. Individual wires in a group or bundle may be spliced provided the
completed splice is located so it can be periodically inspected. Stagger splices so the bundle does not
become excessively enlarged. Many types of aircraft splice connectors are available for use when splicing
individual wires. Use of the self -insulated splice connector is preferred; however, a noninsulated splice
connector may be used provided the splice is covered with plastic sleaving (or heat –shrink) which is
secured at both ends. Sold er splices may be used; however, they are particularly brittle and not
recommended.
a.
There should be not more than one splice in any one wire segment between any two
connectors or other disconnect points, except as allowed by c and g below.
b.
Splices in bundles should be staggered and shall not increase the size of the bundle so as
to prevent the bundle from fitting in its designated space or cause congestion which will
adversely affect maintenance.
c.
Splices shall not be used to salvage scrap lengths of wire.
d.
Splices shall not be used within 12 inches of a termination device, except for e below.
e.
Splices may be used within 12 inches of a termination device when attaching to the pigtail
spare lead of a potted termination device, or to splice multiple wires to a single wire, or to
adjust the wire sizes so that they are compatible with the contact crimp barrel sizes.
f.
The application of splices shall be under design control and shall be authorized by engineering
drawings.
g.
Splices may be used to repair manufactured harnesses or installed wiring when approved by
engineering.
AMPS
2 Amps or less
3 Amps
4 Amps
5 Amps
7 Amps
10 Amps
15 Amps
20 Amps
30 Amps
50 Amps
70 Amps
WIRE GAUGE (SIZE)
20 Gauge
18 Gauge
16 Gauge
14 Gauge
14 Gauge
10 Gauge
10 Gauge
10 Gauge
8 Gauge
6 Gauge
4 Gauge
Summary of Contents for 170
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Page 25: ...Cessna 170 Service Manual Electrical System ELECTRICAL SCHEMATIC SNs 20267 THRU 25372 ...
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Page 27: ...Cessna 170 Service Manual Electrical System ELECTRICAL SCHEMATIC SNs 26996 AND ON ...
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