RUDDER LIMITER FAIL
(Caution)

The amber 'RUDDER LIMITER FAIL' caution CAS message indicates the rudder limiter has failed. Complete loss of RTL function (failure of both channels). Can either be failure of the RARV, total loss of power, total loss of ADC or total loss of HSTECU, or a disagreement between the rudder limiter RVDT and command position indicating a component failure by disengagement.

On the flight controls synoptic page, the color of the Rudder Travel Limit tick marks shall be Amber when the RUDDER LIMITER FAIL (Caution) message is annunciated.

• Rudder Travel Limiter Actuator (RTLA)
• Air Data Computer (ADC)
• Rotary Variable Differential Transformer (RVDT)
• Rudder Limiter
• Horizontal Stabilizer Electronic Control Unit (HST ECU)
• Associated Wiring

Advisory Wire/Service Bulletin:

• AW300-27-0037 - Spoiler Electronic Control Unit (SECU) - Circuit Breaker Reset Procedure
• AW300-27-0077 - Troubleshooting Guide for Spoiler Electronic Control Unit and Horizontal Stabilizer Trim Electronic Control Unit
• AW300-27-0081 - Spoiler Electronic Control Unit (SECU) and Horizontal Stabilizer Electronic Control Unit (HSTECU) - Cold Temperature Circuit Breaker Reset Procedure

Forum Articles/Infoservice/Newsletter: None
NOTE:

1. Some faults can be cleared by re-rigging the HST ECU. The HST ECU stores the specific rig values for the HSTA and RTLA. Any changes to these units CAN cause faults.
2. Check the top of the HST ECU for status LEDs.

• The HST ECU has a number of LEDs that are visible when the unit is powered up. There are basically three sets; Right, Middle, and Left. The main ones of concern are the Right and Left lights.
• If there are no lights present on the right or left side of the unit this means either the command or monitor side is not getting power.
• If this happens, re-apply power and monitor unit. There should be a fault present on the EICAS.
• If this does not clear the fault, try to re-rig the unit.
• If this still does not clear the fault, return the unit as loss of either Command or Monitor Power.

For the HST ECU, wait 10 to 15 minutes after initial power-up then perform the following:

1. Pull the two C/B for the HST ECU, RCBP-B13 (SEC STAB TRIM/RUD LIM) and RCBP-B15 (PRI STAB TRIM/RUD LIM). Wait 10 seconds and push-in both circuit breakers.
2. Perform the Operational Test of the RTLA.

   1. The Stall Test runs the RTL preflight check. You must let it finish the test before selecting the switch to OFF. If it is not run in 10 flights it will post a CAS message and not clear until it is ran.
   2. The SPC ties directly to the RTL. If there is an SPC issue the RTL will show a fault. Check the SPC when dealing with RTL faults.
   3. Water build-up in the pitot tube has caused RTL faults to be displayed.

3. Check MDC for ADC/IOC faults, verify that the ADC system is indicating on the Primary Flight Displays. Troubleshoot any ADC/IOC issues first.
4. If the system does not pass the test procedure, perform rigging of the RTLA, and Rudder Travel Limiter (RVDT).
5. Possibly the rigging will not work, if the rigging does not work, or the fault still exists, gain access to and inspect the rudder travel limiter actuator (MPE79), Rudder Travel Limiter Rotary Variable Differential Transformer (RVDT, MPE20) and wiring. Check wiring between the HSTECU and RTL actuator.
6. If the wiring is good, power and grounds are available, suspect the Rudder Travel Limiter, remove and replace.
7. If the fault still exists, suspect the HST ECU, remove and replace.