All GPS 500W TAWS, GNS 530W TAWS, and GNS 530AW TAWS Units’ meeting both of the following conditions:
- Main Software Version 3.30 (or earlier)
- Installed in an aircraft with an external TAWS annuniciator
When TAWS is inhibited on the GPS 500W TAWS, GNS 530W TAWS or GNS 530AW TAWS Unit, the GPWS visual alerts (Excessive Descent Rate and Negative Climb Rate) are inhibited on the external annunciator. Visual alerts and aural alerts are NOT inhibited on the GNS Unit.
This issue was corrected in GNS Main Software Version 4.01. For more information, refer to Software Service Bulletin 1006, Revision C.
Pilots should be aware of the following condition: when an aural GPWS alert is heard – i.e., an Excessive Descent Rate or Negative Climb Rate alert, and TAWS is inhibited, the visual alert will be displayed on the GNS unit but it will not be displayed on the external annunciator.
Upgrade the GPS 500W TAWS, GNS 530W TAWS, or GNS 530AW TAWS Unit to Main Software Version 4.01 or later.