(2)
Three electronic sets, one to control each motor. The electronic sets also control the signal from the ELAC/SEC computers.
(3)
An override mechanism with three microswitches. It is installed downstream of the reduction gearbox. The override mechanism is connected mechanically to the input shaft.
G. Position Transducer
The THS actuator has two inductive position transducer packages. They are the command position transducer and the monitor position transducer. The command position transducer is used to find the position of the override mechanism output/input control sequence to the control system of the THS actuator. The monitor position transducer is used to find the position of the ball screw.
H. Structural Components
The structural components include:
-
The attachments to the horizontal stabilizer,
-
The attachments to the THS actuator and to the structure.
-
The ball screw and the ball nut.
The THS actuator is connected to the horizontal stabilizer through the dual concentric axles, the attachment plates and the fail safe plates. These are installed to the trunnions of the ball nut.
A primary ring gimbal attaches the THS actuator to the structure. The primary ring gimbal is installed on the two linking axles of the no-back housing spigots. The structural components are of a two-path configuration. On the secondary load path there is usually no load.
J. Line Replaceable Units (LRU)
The Line Replaceable Units (LRU) connected to the THS actuator are as follows:
-electronic control module of each of the electric motors,
-pitch trim actuator,
-position transducer packs,
-filter,
-hydraulic motors.
K. Technical Data
(1) Mechanical
---------------------------------------------------------------------
-THS actuator travel with a total
THS angular movement 17.5 degrees
-Operation travel 513.75 mm (20.23 in.)
-Stop-to-stop travel 531.75 mm (20.94 in.)
-
Used travel of the electrical inputs 2105 rev
-
Used travel of the mechanical inputs 6.13 rev
-Limit load
-Tensile 12.700 daN (28.550 lbf.)
-Compressive 19.000 daN (46.086 lbf.)
-Weight (when filled with fluid) 47.9 kg (105.4 lb.)
(2) Hydraulic
---------------------------------------------------------------------
-
Maximum flow for each circuit 27 l/min (7.02 USgal.mn)
-
Maximum internal leakage 1 to 1.5 l/min
(0.264 to 0.396 USgal.mn)
-
Maximum external leakage Nil
-Operation pressure of pressure-off
brake 100 bar (1450 psi)
6. Operation
_________
(Ref. Fig. 004, 005, 006)
A. Normal Operation
The Green and Yellow hydraulic systems send hydraulic power through the valve blocks to the POB of the hydraulic motors. When the POB receive the hydraulic power, they release the shafts of the hydraulic motors. The two hydraulic motors are ready for operation. The electrical pitch trim signal of the PTA operates the servomotor No.
1. This servomotor operates both control valves in the open configuration
while the other two servomotors are in stand-by. The servomotor No. 1
operates through a path that has:
-
a PTA reduction gear,
-
a mechanical override mechanism.
Then two separate gear paths which are connected by an idler are moved.
Each of the separate gear paths have:
-
a primary detent,
-an epicyclic control differential,
-
a control gear train, which has an eccentric device,
-
a control valve detent,
-
a control valve command shaft.
The hydraulic fluid is so supplied to both hydraulic motors referred to
the control valve opening.
The epicyclic control differential output moves the control valve. With the control valves open, the hydraulic fluid flows to the hydraulic motors.Both hydraulic motors operate at the same time and move the ball screw through:
-
the power differential,
-
the power gear train.
As the PTA output continues to rotate, it keeps the control valve open and so the hydraulic motors operate to move the ball screw. When the PTA output gets to the position specified by the signal given on the servomotor, the control differential input is stopped. The feedback gears moves the control differential output which decreases the opening of the control valve. The control valve closes and the hydraulic flow to the motors stop. The ball screw-jack then stops at the specified position. Interval stops attached to the mechanical input keep the travel of the ball screw-jack shaft to a limit. The ball screw has claw-type stops attached at each end. The stops prevent any mechanical overrun if the internal stops do not operate.
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