Checking For Suction Air Leakage; Checking Landing Gear Cycle Time - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
6-15. CHECKING FOR SUCTION AIR LEAKAGE.
a. Remove engine cowling for access.
b. Disconnect hydraulic pump suction (larger) hose from the pump and connect test unit suction
hose to airplane suction hose, using a suitable fitting.
c.
Disconnect hydraulic pump pressure (smaller) hose from pump and connect test unit pressure
hose to airplane pressure hose, using a suitable fitting.
d. Connect test unit electrical cable to appropriate electrical power source.
e.
Jack the airplane and cycle the landing gear through five complete cycles.
f. Observe the test unit reservoir for any air bubbles which would indicate leakage in suction line,
hose, or fittings. Replace defective parts.
NOTE
If replacement of parts stops any visible air in test unit reservoir,
but air still enters hydraulic system, engine driven pump may have
a suction leak.
g.
Ascertain that the landing gear selector handle is in the down neutral position, and that the
landing gear is down and locked.
h. Remove the airplane from jacks and disconnect the test unit in accordance with Paragraph 6-17.
6-16. CHECKING LANDING GEAR CYCLE TIME. When the hydraulic system on the airplane is
suspected of malfunction because gear cycle time is slow, it could be caused by low fluid in airplane
reservoir causing system to be full of air. The following procedure will purge air from system and fill the
reservoir:
a.
Place the airplane on jacks in accordance with Jacking, Section II.
b.
Cycle the landing gear through two complete cycles in accordance with Paragraph 6-9.
c.
With landing gear extended, place gear handle in full up position and record time required for
gear to retract and doors to close. Time should not exceed 9 seconds + .5 seconds plus the time required for
the time-delay valve to operate. (Refer to Paragraph 6-10.)
d.
With landing gear retracted, place gear handle in full down position and record time required for
gear to extend and doors to close. Time should not exceed 8 seconds + .5 seconds plus the time required for
the time-delay valve to operate. (Refer to Paragraph 6-10.)
NOTE
These times are taken using a single test unit. These times can be
reduced considerable with the use of two test units, one hooked to
each fire wall fitting.
NOTE
If time is within limit when operated by test unit, but exceeds
limit when operated by engine driven pump, there is internal
leakage in the pump. Repair or replace the pump. If time exceeds
the limit when operated either by the test unit or engine driven
pump, internal leakage is in the hydraulic system. Check actuators
for internal leakage. Repair or replace actuators as required. If
actuators are not defective, Power Pack internal leakage is
indicated. Repair or replace Power Pack. (Refer to Paragraph 6-21
or 6-56 for repair of hydraulic components.)
Reissued: 9/23/80
HYDRAULIC SYSTEM
2A22