-
two pilot valves

 -a spool valve, which contains a spool, a sleeve and two springs.
 Each solenoid, A and B, has two coil windings. Each coil winding is independently connected to two electrical connectors identified SYSTEM 1 and SYSTEM 2. Usually only one circuit is used, but either circuit operates the solenoids if the other is not available.
 When energized, each solenoid moves a plunger which operates a spool-type pilot valve. The pilot valve opens or closes a hole that connects to one end of the spool valve.
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 The spool valve has a sleeve in which a spool moves. Two springs keep the spool in the center position of the sleeve when there is no pressure in the valve.
 The sequence of operation of the two selector valves during retraction and extension are as follows:
 -Landing gear UP selection
 -------------------------------------------------------------------------------ACTION EFFECT RESULT -------------------------------------------------------------------------------
The door solenoid 'A' is de-energized, and the door solenoid 'B' is energized.  The pressure port is connected to the ports C and K. The ports D and L are connected to the return port.  The doors open, whichcompletes the electricalcircuit to energize thegear solenoid 'B'. Thedoor solenoid 'B' stays energized until all the gears are locked in the selected position.
 The gear solenoid 'B' is energized.  The pressure port is connected to the ports E and M. The ports F and N are connected to the return port.  The gear retractsand locks up which,completes the electricalcircuit to energize thedoor solenoid 'A'.
 The gear solenoid 'A' stays energized until all of the doors are
 locked in the closed
 position.
 The door solenoid 'A' is energized.  The pressure port is connected to the ports D and L. The ports C and K are connected to the return port.  The doors close andlock. The doorsolenoid 'A' staysenergized and thegear solenoid 'B' de-energizes.

 -Landing gear DOWN selection

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The door solenoid 'A' is de-energized, the door solenoid 'B' is energized.
The gear solenoid 'A' is energized.
The door solenoid 'A' is energized.
The pressure port is  The doors open, which
connected to the ports  completes the electrical
C and K. The ports D  circuit to energize the
and L are connected  gear solenoid 'A'. The
 to the return port.  door solenoid 'B'
 stays energized until
 all the gears are locked
 in the selected position.
The pressure port is  The gear extends and
connected to the ports  locks down, which completes
 F and N. The ports E  the electrical circuit to
 and M are connected to  energize the door solenoid
 the return port.  'A'. The door solenoid 'B'
 de-energizes.
The pressure port is  The doors close and
connected to the ports  lock. The door solenoid
 D and L. The ports C  'A' stays energized
 and K are connected to  whenever electrical
 the return port.  power is applied.
 The gear solenoid 'A'
 de-energizes as soon
 as the first door
 moves away from the
 fully open position.

 D. NLG Door Closing/Opening Safety Valves (2629GM, 2630GM)
 (Ref. Fig. 010) **ON A/C 301-399,
 (Ref. Fig. 020) **ON A/C ALL
 (Ref. Fig. 021)
 The safety valve is installed in the open and close lines between the NLG door-actuator and the L/G door selector-valves. The safety valve closes the line if there is a hydraulic leak.
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 NLG Door Closing/Opening Safety Valve (2629GM, 2630GM)
 Figure 020

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 Safety Valve (2629GM,2630GM) - Schematic Figure 021 
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 The safety valve will only operate at a flow rate equal to or greater than 11 ltr/min.
 (1) Valve Body
 The valve has a body with two hydraulic ports B and C. The body is machined and holds the slide valve and valve seat. The end fitting (installed in the upper end of the body) holds:
 -
the jet

 -
the spring