When addressing a "Sour" response, what feature check is typically invalid?

In the context of addressing a "Sour" response, the focus is on identifying which feature checks are relevant or relevantly invalid. A "Sour" response indicates a problem with the identification process, often suggesting that the aircraft's response is inconsistent with expectations. In this scenario, the validity of the checks becomes crucial in troubleshooting.

The administrative IFF check and the selective ID feature check are considered both invalid in this situation because "Sour" responses do not necessarily provide reliable data for either of these checks. Administrative IFF checks involve verifying the Identity, Friend or Foe status and may rely on the accuracy of the displayed information, which can be compromised during a "Sour" response. Selective ID checks, typically used to filter or distinguish between identified aircraft, also cannot provide reliable results when the response is not correct.

Flight path verification, however, is a different aspect that checks the actual trajectory of the aircraft against expected patterns. Since it does not depend on the response to IFF interrogations, it remains a valid check even during a "Sour" response.

Thus, stating that both the administrative IFF check and the selective ID feature check are invalid aligns with the understanding that "Sour" responses make the data