applications are for covering soldered connec-
Q4. List the three types of safety wire.
tions, open bus bars, and permanent splices.
For general-purpose wiring, use either clear
or opaque flexible vinyl sleeving. For high-
temperature applications (160°F to 400°F), you
Q5. What is the purpose of bonding?
should use silicone rubber or fiber glass sleeving.
other solvents is necessary, use nylon sleeving,
either clear or opaque.
MAINTENANCE OF MOTORS
Bus bars normally have panels or junction
boxes to protect them against shorting. If the bus
bars aren't enclosed, use of protective coating is
Learning Objective: Recognize electrical
desirable. You can use sleeving by slitting a piece
of vinyl tubing and wrapping it around the bar
motor and generator maintenance proce-
after making all connections. Be careful to choose
a tubing that has a large enough diameter to
Since most motors and generators are not
permit a generous overlap when tied in place
accessible during flight, the first sign of motor
trouble in many instances is complete failure.
You can temporarily protect a wire with
damaged insulation by using a sleeve of flexible
so the preventive maintenance you perform is
basically the same. You should be sure that the
diameter of the wire. The length should be at least
motor and/or generator mount is secure. Inspect
2 inches longer than the damaged portion of the
the mechanical linkage for proper alignment and
insulation. Split the sleeve lengthwise and wrap
security. Check that the electrical connections are
it around the wire at the damaged section. Then,
secure and clean. Check for signs of corrosion.
tie the sleeve with nylon braid at each end and
Make sure of proper voltage.
at 1-inch intervals over the entire length. Since you
must replace the damaged wire, use this procedure
You should inspect the exposed portion of the
as an emergency measure.
windings for evidence of overheating. If the
C), slip the sleeving on the wire before the splicing
insulation on the windings or leads is cracked and
brittle, replace it. If, you smell burning insulation,
operation. After completing the splice, move the
or notice smoke or excessive noise, replace the
sleeving to cover the finished splice, and then tie
it at each end with nylon braid.
You will use a slightly different arrangement
When dismantling a motor, you should
carefully remove the bearings and wipe them
this application you use two pieces of sleeving,
clean. Be sure to wrap the bearings in clean oil
one for the braid and one for the wire itself.
paper until needed during reassembly. Replace
bearings showing pronounced stickiness or
bumpy operation. During inspection of bearing
REVIEW SUBSET NUMBER 5
assemblies, check for the presence of cracks and
pitted surfaces. Also, check for any physical
damage present in the bearing elements.
Q1. What publication contains information on
mounting hardware for aircraft parts?
Most ac motors are prelubricated at the time
of manufacture and have sealed bearings. The
bearings require a visual inspection only. If the
Q2. When substituting hardware, what should
bearings are damaged, turn the motor in for
you consider before making the substi-
overhaul. Before reassembling the motor, wipe
the rotor and stator clean with a lint-free cloth.
During all cleaning operations, use the correct
cleaning solvents. As a final check, conduct an
operational inspection of the motor, using the
Q3. What is the ONLY reason for clamping a
wire bundle to a plumbing line?