Piper Navajo PA-31 Service Manual page 91

114
1. MOTOR
1.2.
FLEX DRIVE ADAPTER
3. NUT
3
4
4. SHAFT ASSEMBLY
Figure 3-4. Wing Flap Motor
3-11 WING FLAP MOTOR NO LOAD RPM CHECK. (Dukes System)(Refer to Figure 3-4.) This check
for demagnetization of the flap actuating motor should be accomplished along with friction reduction per
Paragraph 3-10 if flap motor circuit breaker popping has been or remains a problem.
a.
With the wing flap motor (1) installed in the aircraft, disconnect both of the flexible drive shafts
(4) and remove one of the flex drive adapters (2) from the motor.
b.
On the exposed motor splines, paint a white strip on one of the spline teeth.
c.
Energize the flap motor with the flap selector switch.
d.
With the aid of a Simpson 410 Photo Tachometer or equivalent, hold the probe within one-half
of an inch of the painted rotating spline shaft and observe the RPM reading on the meter. RPM in excess of
11,000 will indicate a demagnetized motor which should be replaced.
e.
In the event that the above meter cannot be obtained, another method can be used to make the
check. This would require the removal of the motor from the aircraft and using a hand held tachometer and
24-volt D.C. power source. (Refer to Section V, Paragraphs 5-58 and 5-59 for removal and installation of
flap actuator motor.) If this cannot be accomplished, remove the motor and take it to a local electric motor
overhaul facility for the RPM check.
f.
Reassemble and insure proper spline shaft engagement per Paragraph 3-9.
NOTE
Do not perform no load RPM check unless a problem of circuit
breaker popping exists or has existed with the flap motor that is
still in the system.
Revised: 1/29/82
INSPECTION
PIPER NAVAJO SERVICE MANUAL
1D19