What are Electro-Hydrostatic Actuators (EHAs) and why are they used?

What are Electro-Hydrostatic Actuators (EHAs) and why are they used?

• A. They supply hydraulic force to primary flight controls powered by engine bleed air.
• B. They supply hydraulic force to primary flight controls powered by electrical systems, reducing traditional bleed air needs.
• C. They replace electrical systems with hydraulic-only controls.
• D. They are backup hydraulic pumps for landing gear.

Answer: (B)

EHAs are a way to turn electrical power directly into hydraulic actuation for the primary flight controls. In the 787’s more-electric architecture, each actuator contains its own electric motor-driven pump that pressurizes hydraulic fluid to move a control surface. This eliminates the need to run bleed air to power the hydraulic pumps for those controls, reducing bleed-air use, simplifying plumbing, and enabling precise electronic control with good redundancy. That’s why the best choice is that EHAs supply hydraulic force to primary flight controls powered by electrical systems, reducing traditional bleed air needs. They aren’t replacing electrical systems with hydraulics, they aren’t simply backup pumps for landing gear, and they aren’t powered by bleed air.

EHAs are a way to turn electrical power directly into hydraulic actuation for the primary flight controls. In the 787’s more-electric architecture, each actuator contains its own electric motor-driven pump that pressurizes hydraulic fluid to move a control surface. This eliminates the need to run bleed air to power the hydraulic pumps for those controls, reducing bleed-air use, simplifying plumbing, and enabling precise electronic control with good redundancy.

That’s why the best choice is that EHAs supply hydraulic force to primary flight controls powered by electrical systems, reducing traditional bleed air needs. They aren’t replacing electrical systems with hydraulics, they aren’t simply backup pumps for landing gear, and they aren’t powered by bleed air.