missing evidence Negative mode 4 reply

[Dragon1-1]

I saw that in the latest Wags video, the Mode 4 interrogation gives a negative reply. This is not correct unless the target being interrogated has its parrot bent or the A/B code switch is set wrong in either aircraft. Mode 4 encrypts both interrogation and reply, and an incorrect interrogation (such as one from a hostile aircraft) would not return any reply. This is precisely so you can't use IFF to locate enemy aircraft. 

[Arctic Fox]

The yellow square Mode 4 reply ED has implemented as a "negative" reply is described as an unknown reply, and publicly available manuals like the Greek and Chilean -34s state that they should not normally happen at all. IE normally the only reason such a reply would be produced is as a result of some fault in the transmission. It should not appear on any track that does not produce a reply like it does in Wags' video.

I feel like ED has had some misunderstanding of the fundamental concepts of AIFF functionality in the F-16 at this point. In a previous video Wags talked about a negative IFF reply contributing to track classification, something which documents (for example M3) explicitly state is not a feature of the jet, and now it seems like we're getting symbology for radar targets that fail to reply to IFF (I am assuming ED doesn't think that hostile aircraft will actually send out a "negative" reply).

In reality the manuals essentially paint AIFF functionality as largely disconnected from the fire control radar itself. AIFF interrogation can happen with the radar in A-G mode or even with the radar off, replies can come from undetected friendlies (but of course not hostiles, at least in Mode 4) and replies are explicitly not correlated with tracks to provide classification. It is essentially a separate system using the same display, and it's up to the pilot to correlate the information.

Edited November 16, 2022 by Arctic Fox

[amalahama]

9 hours ago, Arctic Fox said:

The yellow square Mode 4 reply ED has implemented as a "negative" reply is described as an unknown reply, and publicly available manuals like the Greek and Chilean -34s state that they should not normally happen at all. IE normally the only reason such a reply would be produced is as a result of some fault in the transmission. It should not appear on any track that does not produce a reply like it does in Wags' video.

I feel like ED has had some misunderstanding of the fundamental concepts of AIFF functionality in the F-16 at this point. In a previous video Wags talked about a negative IFF reply contributing to track classification, something which documents (for example M3) explicitly state is not a feature of the jet, and now it seems like we're getting symbology for radar targets that fail to reply to IFF (I am assuming ED doesn't think that hostile aircraft will actually send out a "negative" reply).

In reality the manuals essentially paint AIFF functionality as largely disconnected from the fire control radar itself. AIFF interrogation can happen with the radar in A-G mode or even with the radar off, replies can come from undetected friendlies (but of course not hostiles, at least in Mode 4) and replies are explicitly not correlated with tracks to provide classification. It is essentially a separate system using the same display, and it's up to the pilot to correlate the information.

 

This might have changed in recent tapes however, providing a more correlated display of AIFF and FCR

[Frederf]

It doesn't. If there's no reply in any mode then there's no symbol. IFF is completely independent as an info overlay. There's no correlation.