10 Questions
What provides the electronic drive for one electric motor and control of the two motor brakes in the HSCU?
Each channel of the HSCU
Where does the HSCU take its commands from if there is a failure in the two FCC to HSCU buses?
BACKUP PITCH trim switches located on the pedestal
How is the horizontal stabilizer displaced in the system?
By a dual load path electromechanical actuator driven by two identical and independent electric motors in a torque-summed arrangement
What provides the actuation of the HSTA in the system?
Motor brake assemblies
How do the motor brakes operate in the system?
In active / standby configuration
How many independent load paths does the HSTA have?
Two
During normal operation, which load path carries the HSTA operating and static loads?
Primary path
What provides HSTA irreversibility under application of the defined limit load?
No-back device or motor brakes
How is the gear train connected to the ballscrew in the system?
Through an inertial slip clutch
How many electric motors drive the dual load path electromechanical actuator for the horizontal stabilizer?
Two
Study Notes
Horizontal Stabilizer Trim Actuator (HSTA)
- The HSTA incorporates a fail-safe design with two independent dual channel sensors that provide stabilizer position data.
Actuator Design
- The actuator has two fully independent load paths: primary load (normal) and secondary load.
- The dual load path design ensures that no single failure will prevent the actuator's ability to react to load.
Safety Features
- The HSTA has extend and retract stops to limit actuator motion in the event of control loop failure.
- A torque limiting slip clutch limits the load imparted to aircraft structure.
- A tie rod lock assembly prevents motion following a primary load path failure.
Operation Modes
- In normal conditions, only the primary load path carries the actuator operating and static loads, while the secondary load path remains unloaded.
- If a failure occurs in the primary load path, the secondary load path immediately engages.
Failure Response
- After a failure, the actuator locks, holding the horizontal stabilizer in the last commanded position for the remainder of the flight.
- When the locked actuator is commanded to move, the stabilizer system detects and annunciates the failure.
Actuator Irreversibility
- Actuator irreversibility is provided by a mechanical no-back device mounted on the actuator ballscrew.
- Electromechanical brakes on each motor brake assembly also provide actuator irreversibility.
Horizontal Stabilizer Actuator Motor
- The horizontal stabilizer actuator motor is a 270 Vdc brushless motor with an integral electromechanical brake and brushless resolver.
CAS Messages
- Stabilizer Rigging Complete: Blue message indicates that rigging is valid for the current aircraft.
- Stabilizer Maintenance Required: Blue message indicates that the HSCU has flagged a maintenance item.
- Stabilizer Failed: Amber message indicates that the horizontal stabilizer is not responding to movement commands or surface position information is unreliable or unavailable.
- Stabilizer Channel Fail: Amber message indicates that a horizontal stabilizer control channel has failed.
- Stabilizer Primary Trim Fail: Amber message indicates a loss of valid pitch trim communication from the FCCs to the HSCU.
Test your knowledge on the Hydraulic Flight Control System (HSTA) which incorporates a fail-safe design with dual sensors, dual load paths, and a torque limiting slip clutch for aircraft structure protection.
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