What does the message KEY NOT VER indicate on the NAV ACCUR page?

What does the message KEY NOT VER indicate on the NAV ACCUR page?

• A. Key validation failed
• B. GUK in use with MSN DUR at 0
• C. Key not available for use
• D. Key is too old for use

Answer: (B)

The message "KEY NOT VER" on the NAV ACCUR page indicates that the Ground User Key (GUK) is currently in use while the measured duration (MSN DUR) is at 0. This means that the system is set to use a key, but it is not appropriate or valid for the current operation since the duration indicates that the key is not live for the navigation computations that require it. This situation typically arises in avionics systems where keys are necessary for secure communication and operation, and it highlights a scenario where the expected key functionality is not active. Therefore, it’s important for operators to ensure that the navigation system has a valid and active key that meets the required criteria to function properly. Understanding the context of the other options helps clarify why they do not apply. For instance, key validation failure would signify a different set of issues, such as the key not meeting specific safety or functionality checks, while the key being unavailable means it cannot be used at all. Similarly, a key being too old would indicate that its operational validity has expired, rather than it simply not having a duration that can be measured in the current context.

The message "KEY NOT VER" on the NAV ACCUR page indicates that the Ground User Key (GUK) is currently in use while the measured duration (MSN DUR) is at 0. This means that the system is set to use a key, but it is not appropriate or valid for the current operation since the duration indicates that the key is not live for the navigation computations that require it.

This situation typically arises in avionics systems where keys are necessary for secure communication and operation, and it highlights a scenario where the expected key functionality is not active. Therefore, it’s important for operators to ensure that the navigation system has a valid and active key that meets the required criteria to function properly.

Understanding the context of the other options helps clarify why they do not apply. For instance, key validation failure would signify a different set of issues, such as the key not meeting specific safety or functionality checks, while the key being unavailable means it cannot be used at all. Similarly, a key being too old would indicate that its operational validity has expired, rather than it simply not having a duration that can be measured in the current context.