CRJ-550 Hydraulic System

How many hydraulic systems does the CRJ-550 have?

Three completely independent systems (no fluid exchange).

What powers Hydraulic System 1?

EDP 1A (Primary) and ACMP 1B (Backup).

What powers Hydraulic System 2?

EDP 2A (Primary) and ACMP 2B (Backup).

What powers Hydraulic System 3?

ACMP 3A (Primary) and ACMP 3B (Backup).

Which hydraulic system is the most critical and why?

Hydraulic System 3, because it powers all primary flight controls.

What components are powered by Hydraulic System 1?

Left aileron, left elevator, left spoilers, outboard brakes.

What components are powered by Hydraulic System 2?

Right aileron, right elevator, right spoilers, nose wheel steering, inboard brakes.

What components are powered by Hydraulic System 3?

Rudder, elevators, landing gear, all primary flight controls.

What happens if Hydraulic System 3 fails?

The ADG (Air-Driven Generator) automatically powers Pump 3B to maintain flight control operation.

What happens if an engine-driven hydraulic pump (EDP) fails?

The backup AC motor pump (ACMP) does not automatically activate, it must be turned on manually.

When do AC motor pumps (ACMPs) 1B, 2B, and 3B activate automatically?

When their switch is in AUTO, at least one generator is operating, and when flaps are out of zero.

Does external AC power activate the hydraulic pumps?

No, external AC does not power ACMPs when in AUTO.

How is hydraulic fluid cooled?

Systems 1 & 2 use a heat exchanger cooled by ram air

System 3 does not require cooling.

What are the hydraulic temperature and pressure limits?

• Normal pressure is 3,000 PSI

• low pressure warning is below 1,800 PSI

• High pressure is above 3,200 PSI

• normal temperature is below 96°C

• overheat warning is above 96°C.

What happens if hydraulic pressure is lost?

The affected system loses function, and manual backup pumps must be activated.

How are hydraulic reservoirs pressurized?

By bleed air to ensure consistent fluid flow to pumps.

What does the HYD SOV (Shutoff Valve) do?

Shuts off fluid flow to the engine-driven pump (EDP) when ENG FIRE PUSH is pressed.

How does the Air-Driven Generator (ADG) impact the hydraulic system?

If deployed, ADG automatically powers Pump 3B to maintain primary flight controls.

What happens if both hydraulic pumps in a system fail?

That system loses functionality, and backup systems must be used for critical components.

What does 'HYD PRESS LOW' mean?

Hydraulic pressure has dropped below operational limits.

What does 'HYD TEMP HIGH' mean?

Hydraulic fluid temperature is above 96°C, indicating overheating.

What does 'HYD PUMP FAIL' mean?

A hydraulic pump has failed.

What does 'HYD SOV FAIL' mean?

The hydraulic shutoff valve did not close properly.

What ACMP is powered by the ADG?

3B

What is the normal percentage of hydraulic fluid in the system?

45-85%

What type of hydraulic fluid is used?

Sky drop

What color is hydraulic fluid?

Purple