Boeing 777 Thrust Reverser operation schematic

Extend
To extend the T/R sleeves you put the reverse thrust
lever in the reverse thrust interlock position. This
causes three control signals to go to the TRAS. These
are the effects of the control signals:
The SLV opens and supplies hydraulic control
pressure to release the sync locks.
The directional control solenoid valve opens and
supplies hydraulic control pressure to the DCV.
This moves the DCV to permit hydraulic power to go
to the extend and retract sides of the actuators.
The isolation valve opens and supplies hydraulic
pressure through the DCV to the actuators.
Hydraulic pressure to the actuators releases the
locking actuators and moves the sleeves to the aft
(extended) position.
Retract
To retract the T/R sleeves you put the reverse thrust
levers in the forward thrust position. This causes two
control signals to go to the TRAS. These are the
effects of the control signals:
The signal to open the SLV is removed. A time delay
circuit in the ELMS keeps the sync lock solenoid
valve energized. This keeps the SLV open and the
sync lock unlocked. The sync locks stay unlocked
until the time delay is complete.- The directional control solenoid valve closes and removes the hydraulic control pressure to the DCV.
This moves the DCV to permit hydraulic power to go
to the retract side of the actuators.
The EEC begins a time delay before closing the
isolation valve. The isolation valve stays open
and supplies hydraulic power through the DCV to
the actuators. The isolation valve closes when the
time delay is complete
Hydraulic power to the retract side of the actuators
moves the T/R sleeves to the forward (retracted)
position.