Hi vilas,
The A380 has three types of servocontrols:
• Conventional servocontrols that include:
An actuator
A hydraulic block connected to one hydraulic power supply of the aircraft
A servovalve that receives orders from the flight control computers and controls the translation direction of the actuator rod.
A conventional servocontrol cannot operate if there is no hydraulic supply.
• Electro-Hydrostatic Actuators (EHAs) that include:
An actuator
A hydraulic block
An electro-hydraulic generation system that receives orders from the fight control computers. The rotation direction and the speed of the electro-hydraulic generation system determine the translation direction and speed of the actuator rod.
EHAs are fully isolated from the hydraulic power supplies of the aircraft.
An EHA can operate when there is no hydraulic supply, but needs an electrical supply.
• Electrical Backup Hydraulic Actuators (EBHAs) that are a combination of a conventional servo-control and an EHA.
In normal mode, they operate as conventional servocontrols.
If there is a hydraulic failure, they operate as EHAs.
