Troubleshooting ENG Anti-Ice On The G200

January 2025

While Duncan Aviation Airframe technicians performed routine maintenance engine runs on a G200, the R ENG NAC ANTI ICE (A/I) CAS message appeared as the RH engine was started and the engine anti-ice switch in the OFF position. 

In this scenario, the CAS message indicates that pressure is sensed with the A/I switch off, or one of the A/I valves has failed to close. Both internal and external valves are failed safe open (Powered Close).

Troubleshooting Steps:

1. Swap the pressure transmitters from LH to RH engine.
   1. Results: The squawk remained with the RH ENG.
2. Swap the external NAC A/I valve from LH to RH engine.
   1. Results: The squawk remained with the RH ENG.
3. Verify power and ground at NAC A/I valve, ENG A/I valve, and pressure transmitter
   1. Power and ground checks were good.
4. Verify the integrity of the wiring from the pressure transmitter to DCU.
   1. Wiring integrity checks were good.

After the above troubleshooting steps failed to correct the issue, technicians’ attention moved to the internal A/I valve. They gained access to and replaced the internal RH ENG A/I valve.  This corrected the issue. 

When troubleshooting ENG/NAC Anti-Ice issues on G200 engines, remember that the engine does have an internal anti-ice valve in addition to the external anti-ice valve.  Both valves are failed safe open and operate in a similar manner.