Checking Priority Valve; Checking Main Relief Valve; Checking Hand Pump Relief Valve - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
6-12. CHECKING PRIORITY VALVE.
a. Connect hydraulic test unit in accordance with Paragraph 6-8 and place airplane on jacks, in
accordance with Jacking, Section II.
b.
Cycle landing gear through two complete cycles in accordance with Paragraph 6-9.
c. With gear down and locked and test unit operating, turn the master switch off to open gear
doors. Leave the switch off to permit the doors to remain open, thereby making it easier and faster to
complete this check.
d. Open hydraulic test unit bypass valve.
e. Place landing gear selector handle full up. Very slowly close bypass valve, observing pressure
gauge of test unit and noting pressure at which priority valve opens. Priority valve should open at a pressure
of (refer to Table VI-I or VI-II).
NOTE
As the priority valve opens, the nose gear downlock starts to
release. Read the pressure gauge at this point.
f. Refer to Paragraph 6-49 or 6-90 for priority valve adjustment.
g. Ascertain that the landing gear selector handle is in the down neutral position, and that the
landing gear is down and locked.
h.
Disconnect the test unit in accordance with Paragraph 6-17, and remove the airplane from jacks.
6-13. CHECKING MAIN RELIEF VALVE.
a. Connect test unit in accordance with Paragraph 6-8.
b. Open test unit bypass valve.
c. Hold the landing gear selector handle in the full down position.
d. Slowly close bypass valve, observing pressure build-up and point at which pressure stabilizes on
test unit gauge. Stabilization indicates relief valve setting. The relief valve pressure and flow rate are given in
Tables VI-I and VI-II.
e.
The Ozone power pack must be removed and partially disassembled to adjust the main relief
valve setting. (Refer to Paragraph 6-48.) The Wiebel Tool power pack main relief valve adjustment is
accomplished with the power pack installed in the airplane. Remove the cover to gain access to adjusting
screw. (Refer to Paragraph 6-89.)
f. Disconnect the hydraulic test unit in accordance with Paragraph 6-17.
6-14. CHECKING HAND PUMP RELIEF VALVE.
a. Place landing gear selector handle in the full down position. With master switch off, operate
emergency hand pump to open landing gear doors.
b. Disconnect door open line (upper fitting) from main gear door cylinder and connect hydraulic
test unit pressure hose to door open line. Cap actuator fitting.
c. Close bypass valve on hydraulic test unit.
d. Operate emergency hand pump in airplane, observing hydraulic test unit pressure gauge for
pressure at which hand pump relief valve opens. This pressure should be as indicated in Table VI-I or VI-II.
e. The Ozone power pack must be removed and partially disassembled to adjust hand pump relief
valve setting. (Refer to Paragraph 6-47.) The Wiebel Tool power pack hand pump relief valve adjustment is
accomplished with the power pack installed in the airplane. Remove the cover to gain access to adjusting
screw. (Refer to Paragraph 6-88.)
f. Open bypass valve on test unit to release the pressure, disconnect the test unit pressure hose from
door open line. Remove cap from actuator fitting and reconnect door open line to main gear door actuator.
g. Replenish hydraulic reservoir fluid as required.
Reissued: 9/23/80
HYDRAULIC SYSTEM
2A21