Specifications

AC 43.13-1B CHG 1 9/27/01
Page 11-98 Par 11-235
nonpressurized areas. Derating of the con-
nectors should be covered in the specifications.
11-234. SPARE CONTACTS (Future
Wiring). To accommodate future wiring ad-
ditions, spare contacts are normally provided.
Locating the unwired contacts along the outer
part of the connector facilitates future access.
A good practice is to provide: Two spares on
connectors with 25 or less contacts; 4 spares
on connectors with 26 to 100 contacts; and
6 spares on connectors with more than
100 contacts. Spare contacts are not normally
provided on receptacles of components that are
unlikely to have added wiring. Connectors
must have all available contact cavities filled
with wired or unwired contacts. Unwired
contacts should be provided with a plastic
grommet sealing plug.
11-235. INSTALLATION.
a. Redundancy. Wires that perform the
same function in redundant systems must be
routed through separate connectors. On sys-
tems critical to flight safety, system operation
wiring should be routed through separate con-
nectors from the wiring used for system failure
warning. It is also good practice to route a
system’s indication wiring in separate con-
nectors from its failure warning circuits to the
extent practicable. These steps can reduce an
aircraft’s susceptibility to incidents that might
result from connector failures.
b. Adjacent Locations. Mating of adja-
cent connectors should not be possible. In or-
der to ensure this, adjacent connector pairs
must be different in shell size, coupling means,
insert arrangement, or keying arrangement.
When such means are impractical, wires
should be routed and clamped so that incor-
rectly mated pairs cannot reach each other.
Reliance on markings or color stripes is not
recommended as they are likely to deteriorate
with age.
c. Sealing. Connectors must be of a type
that exclude moisture entry through the use of
peripheral and interfacial seal that are com-
pressed when the connector is mated. Mois-
ture entry through the rear of the connector
must be avoided by correctly matching the
wire’s outside diameter with the connector’s
rear grommet sealing range. It is recom-
mended that no more than one wire be termi-
nated in any crimp style contact. The use of
heat-shrinkable tubing to build up the wire di-
ameter, or the application of potting to the wire
entry area as additional means of providing a
rear compatibility with the rear grommet is
recommended. These extra means have inher-
ent penalties and should be considered only
where other means cannot be used. Unwired
spare contacts should have a correctly sized
plastic plug installed. (See section 19.)
d. Drainage. Connectors must be in-
stalled in a manner which ensures that mois-
ture and fluids will drain out of and not into
the connector when unmated. Wiring must be
routed so that moisture accumulated on the
bundle will drain away from connectors.
When connectors must be mounted in a verti-
cal position, as through a shelf or floor, the
connectors must be potted or environmentally
sealed. In this situation it is better to have the
receptacle faced downward so that it will be
less susceptible to collecting moisture when
unmated.
e. Wire Support. A rear accessory back-
shell must be used on connectors that are not
enclosed. Connectors having very small size
wiring, or are subject to frequent maintenance
activity, or located in high-vibration areas
must be provided with a strain-relief-type
backshell. The wire bundle should be pro-
tected from mechanical damage with suitable
cushion material where it is secured by the
clamp. Connectors that are potted or have
molded rear adapters do not normally use a