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Afterthe charge is blown, compressed dry nitrogen is released throughits own system of tubing
and into the workingactuators. Each individual system uses a gas supply bottle,shuttle valve, and
up lock-unlocking actuator,all of which are gas operated.
Besidesthe emergency blowdownsystem, the gear can also be pumped down. A hand pump found under a floor access panel between the pilot's and copilot's seat can be used to extend the gearif the hydraulic pump system fails. If a problem doesdevelop,and time permits, use the hand pump first because once the emergency extension system is activated, the affected mechanism and hydraulic system must be purged and serviced.
An anti-retraction system is installed to guard againstinadvertent retraction of the landing gear when the airplane is on the ground, a solenoid latch is positioned just above the control lever. A squat switch on the landing gear and a dynamic pressureq sensor must operate this latch before the landing gearselector control can be moved upward. The landing gearcontrol knob is in the shape of a wheel to differentiate it from the flap control, which has a knob in the shaft of an airfoil.
EFFECTIVITY:
040-999
32-30-00Jan 10/90

PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL

A. ExtensionandRetraction(continued)
4

NOTE: See Following Page For Callouts.
EmergencyExtensionSystemInstallation
Figure 1 (Sheet 1 of 2)

EFFECTIVITY:

Jan10/90 32-30-00
PIPER AIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL

A. ExtensionandRetraction(continued)
1.
Pump -Engine Driven

2.
Filter

3.
CheckValves

4.
HandPump

5.
SelectorHandle

6.
RestrictorValve

7.
Actuator,Nose Gear

8.
Actuator,Main Gear

9.
Actuator,MainGear Door

10.
PowerPackAssembly

A.
Main Relief Valve

B.
Engine Pump Check Valve

C.
PriorityValve

D.
DoorSolenoidValve

E.
VentValve

F.
TimeDelayCheck Valve

G.
Time Delay Valve

H.
Hand Pump Relief Valve

J.K.M.
Filter

N.
Reservoir

P.
LandingGear Selector Valve

Q.
Selector Valve Detent

R.
SelectorValveSpringReturn

S.
ElectricalSwitch

T.
Electrical Connector

11.
PressurePort Valve

12.
SuctionPort Toggle Valve

13.
HandPumpCheckValve AA. Cylinder BB.ExplosiveValve

CC.Fill Valve DD.BurstDisc EE.Gauge
15.
UnlockActuator

16.
ShuttleValve, Main Gear

17.
ShuttleValve,NoseGear

BOTTLEFILL PRESSURES

FILL PORT -DRY NITROGEN ONLY SEE SERVICE MANUAL FOR INSTRUCTIONS TEMP. -PRESSURE RANGE 
F  -40  -20  0  +20  +40 
PSIG  1585  1560  1735  1815  1890 
F  +60  +70  +80  +100  +120 
PSIG  1960  2000  2035  2110  2185 

EmergencyExtensionSystem Installation Figure 1 (Sheet 2 of 2) 
EFFECTIVITY: 040-999  32-30-00 PAGE3Jan 10/90 

PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL

A. Extensionand Retraction (continued)
2. FaultIsolation-Extension and Retraction
NOTE:  Place airplane on jacks before attempting fault isolation of landing gear system (refer to 7-10-00).
CHART 1 FAULT ISOLATION (EXTENSION AND RETRACTION) (Sheet 1 of 2)
Fault  Cause  Remedy 
Landing gear selector  Selector lever cannot be  Ensurethatthe LEFT maingear 
handle fails to operate  movedto the gear up  strut is extended and that the 
to gear up position.  positionwhile the LEFT maingearstrut is com- poweris on. 
pressedor with the power 
off. 
Faulty safety switch on  Adjustor replace safety 
leftmaingear.  switch. 
Gear retracts or extends  Priorityvalveleaksin  Check priority valve 
beforethe doors open.  powerpack.  cracking pressure. 
Solenoid valve stuck in  Turnoff power and hand 
closedposition.  pump doors open. 
Microswitchon power  Check for bent bracketor loose 
packout of adjustment.  mountingor wire and adjust. 
Doors come open in  Micro switch on power  Adjust micro switch. 
flight.  pack out of adjustment. 
Doors fail to close.  Circuit breaker out.  Checkcircuitbreaker. 
(refer to 32-60-00) 
Lightswitchout of  Adjustlimit switch. 
　
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