Fault Message:

HYD RAT PUMP FAIL

Fault Code:

00HRATFL

Associated CAS:

HYD RAT PUMP FAIL
(Caution)

Data Acquisition Unit (DAU) 4 (A31) is reporting Hydraulic System 3B pressure below 2400 psi when the Ram Air Turbine (RAT) is deployed.

• AC Power Center (ACPC) Secondary Logic Card
• AC Motor Pump (ACMP) 3B Pressure Switch (S40)
• Data Acquisition Unit (DAU) 4 (A31)
• Hydraulic System 3 Accumulator Pressure Circuit
• Ram Air Turbine (RAT)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

1. Carry out a quantity check of the hydraulic system.
   NOTE: Low accumulator service pressure at RAT extension can cause a RAT pump start-up failure.
2. Pressurize the hydraulic system 3 with the ACMP 3B. Verify the pressure of the hydraulic system 3.

   1. If the pressure is below 2400 psi, replace the valve manifold and do close out.
   2. If the pressure is above 2400 psi and the message HYD PUMP 3B FAIL message is not shown, go to step 8.
   3. If the pressure is above 2400 psi and the message HYD PUMP 3B FAIL message is shown, continue with next step.

3. Disconnect the hydraulic system 3B pressure switch connector S40P1 and perform a continuity check between the connectors.

   1. If there is no continuity, repair defective wiring as required and do close out.
   2. If there is continuity, continue with next step.

4. Install a jumper between S40P1-A and S40P1-B and check if message goes away.

   1. If the message goes away, replace the hydraulic system 3B pressure switch (S40) and do close out.
   2. If the message is still shown, continue with next step.

5. Swap DAU 4 with DAU 3.

   1. If system checks are good, replace DAU 4 and do close out.
   2. If fault remains, continue with next step.

6. Is the message still present?

   1. If the message goes away, swap back the DAUs and replace DAU 4 and do close out.
   2. If message is still present, continue with next step.

7. Swap back the DAUs and perform a wiring check between pressure switch S40 and DAU 4.

   1. If wiring checks are not good, repair defective wiring as required and do close out.
   2. If wiring checks are good, continue with next step.

8. Do a functional test of the hydraulic system 3 accumulator pressure circuit as follows:

   1. In the flight compartment, on the HYDRAULIC control panel, set the selection of the ACMP 3B switch to OFF.
   2. In the hydraulic service compartment 3, do a check of the pressure gauge on the accumulator.
   3. Record the time (in seconds) for the accumulator pressure indication to reach the service pressure.
      NOTE: The time for the pressure to decrease must be 43 seconds or more.

9. If the bleed down time is less than 43 seconds, replace the valve manifold and do the functional test of the hydraulic system 3 accumulator pressure circuit as follows:

   1. In the flight compartment, on the HYDRAULIC control panel, set the selection of the ACMP 3B switch to OFF.
   2. In the hydraulic service compartment 3, do a check of the pressure gauge on the accumulator.
   3. Record the time (in seconds) for the accumulator pressure indication to reach the service pressure.
   4. If the bleed down time is more than 43 seconds, do close out.
   5. If the time for the pressure to decrease is 43 seconds or more, carry out the hydraulic system 3 (internal leakage check).
      NOTE: Too much internal leakage can cause the hydraulic output pressure from the RAT to be low.
   6. If the internal leakage of the hydraulic system 3 is satisfactory, replace the RAT.

10. Do close out.