investigating R-27ER Goes Active After Dropped Lock

[sleestak]

Attached is a quick clip of an admittedly sloppy BVR engagement where my R-27ER appears to go active on the opposing F-15E. My radar dropped lock after maneuvering to avoid the AIM-120C headed my way. You can watch the R-27ER go dumb, and then appear to reacquire the F-15E and start to lead the target like it has an active seeker and ultimately impact the target (my basic understanding of HOJ is that it would be a pure pursuit intercept and simply fly directly at the emitting source which doesn't appear to be the case here as you can see the missile successfully fly an intercept course on the target).

Ultimately, it looks like my R-27ER went active on the target, even though it should have been trashed after my lock dropped. I fly this simple BVR scenario frequently and this is the first time I've seen this behavior, just updated to 2.8.8.43489 OB FYI.

230816_r27er_active.trk

[Northstar98]

8 hours ago, sleestak said:

(my basic understanding of HOJ is that it would be a pure pursuit intercept and simply fly directly at the emitting source which doesn't appear to be the case here as you can see the missile successfully fly an intercept course on the target).

This isn't necessarily correct - so long as the seeker can measure LOS rate, proportional navigation can be used.

[okopanja]

9 hours ago, sleestak said:

My radar dropped lock after maneuvering to avoid the AIM-120C headed my way.

Actually, F-15E did notch your aircraft radar, hence the lock got dropped.

9 hours ago, sleestak said:

You can watch the R-27ER go dumb, and then appear to reacquire the F-15E and start to lead the target like it has an active seeker and ultimately impact the target (my basic understanding of HOJ is that it would be a pure pursuit intercept and simply fly directly at the emitting source which doesn't appear to be the case here as you can see the missile successfully fly an intercept course on the target).

In HOJ ER will use proportional navigation. In your case I believe it was never in HOJ mode. In fact, I believe that your R-27ER started guiding from the moment R-77 became active at ~ 22km or 12nm, which is exact distance where R-77 goes active.

The interesting thing is that R-77 was actually dumb all the time.

[GGTharos]

This is too funny, it's like the R-77 is datalinking/illuminating for the R-27. 
 

HoJ shouldn't work if you're not illuminating your target either.

[Flappie]

Thanks for the track, @sleestak. I've just replayed it. Then I took control over at different times to try and understand:

1. I ejected a few seconds after the R77 is launched: R-27ER is lost forever.
2. I ejected a few seconds after the R-27ER reacquires and the R-77 is still flying: R-27ER keeps manoeuvring and hits the target.
3. I ejected a few seconds before the R-27ER reacquires and the R-77 is still flying: R-27ER does not reacquire.

I'm not sure what happens. I'll aks devs.

Edited September 21, 2023 by Flappie