MPRF/Pursuit not able to lock over 1100 kmh head on

[AeriaGloria]

Hello, I could swear we had a nice thread about this topic here recently with a track and everything. I’ve looked everywhere and it seems to be gone. 
 

Anyways I’ve done some testing, takes 10-15 degree angle to lock a target flying at 1200 kmh. Or a 45-60 degree angle to lock a target at 1500 kmh. 
 

I would love to hear from ED why the radar does this. I saw it in the manual so I know it’s valid, but it also never stated if it was a “no lock or detection” kind of limit or something else. Anyways cheers