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Radar Slaved AIM-9X Seeker


serpent64

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Ok, riddle me this - I noticed quite a few times when dog-fighting, usually on multiplayer, that the 9X seeker will not always slave to the radar locked target. Example, approaching the merge with two separate adversaries head on at about 3 miles, AIM-9s already selected. Switch to ACM Bore-sight mode and maneuver aircraft to place one bandit within the bore-sight circle on the HUD. 3 out of 5 times radar locks up intended target while seeker head tracks the other non-intended target. Unlock target and try again (bandits are now uncomfortably close now), usually same result. Maintain radar lock and re-cage and uncage seeker (bandits are now ridiculously close as I watch THEIR missiles come off THEIR rails :cry:), again usually same result.

 

Now before anyone says,"the seeker is tracking the hotter target." Slaved means Slaved, the seeker head should follow the radar target in slaved mode. What gives? :helpsmilie:

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How close are the targets if they are both in the missiles field if view it could be pot luck as to which one it locks.

 

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This isn't just me then! I try to use off-boresight with the 9X and HMD, but the seeker doesn't always track with the HMD.

 

It should be boresight mode, uncage, look at target. Nada.

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You have to hold the cage/uncage button until you get a lock when using the JHMCS. Are you holding the button?

 

 

The problem of not slaving to the radar lock is puzzling. If you have Tacview, have you checked to see if there is some counter measure activity that you can see?

 

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It's not exactly an absolute. All the radar does is point the direction for the Sidewinder to look in for a target. Neither the Sidewinder nor the Radar makes any real attempt to correlate their data. It's left to the pilot.

 

 

Sidewinders are relatively simple creatures. They see a heat signature, they lock onto it. Consider the scenario of two targets in close formation, one behind the other, the one in back on afterburner. The radar would have no trouble spotting the cold one and would likely be the one it targets. The Sidewinder looks there and may not even see the intended target, but would see the afterburner flare where it expects a target to be. It would signal the pilot that it has acquired a target, because that's what it does.

 

 

I mean the damn things will lock onto the sun for crying out loud.

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Congratulations, you've discovered the reason for the seeker uncage procedure :)

 

 

I don't know how faithfully it is modeled in DCS with the hornet, but basically the seeker is always looking for a signature to lock onto, even when slaved. If there's something tastier in the missile's seeker scan FoV, it will pick the tastier thing. When and how the missile locks onto target is a matter of programming, and it's not quite the same for all aircraft - in some aircraft, you have to deliberately uncage - in others, once there's a strong enough signal, the missile uncages by itself.

 

Thus why you'd uncage the missile to check the seeker track first, even when slaved.

 

This is also why generally you shouldn't shoot with flares or the sun inside the FoV - the missile will lock onto a target as part of the launch process, and it will probably not be your intended target.

 

 

 

Now before anyone says,"the seeker is tracking the hotter target." Slaved means Slaved, the seeker head should follow the radar target in slaved mode. What gives? :helpsmilie:

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I’ve also noticed it can be difficult to get the 9X seeker to slave to radar when using JHMCS. It almost seems like the seeker isn’t sure whether to follow the JHMCS circle or the radar cueing.

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Where’s the track file!?

Wasn't reporting a definite bug, just wanted feedback from others. Next occurrence, I'll post the file.

 

The problem of not slaving to the radar lock is puzzling. If you have Tacview, have you checked to see if there is some counter measure activity that you can see?

Checked Tacview, no countermeasures deployed by either bandit on approach to the merge.

 

It's not exactly an absolute. All the radar does is point the direction for the Sidewinder to look in for a target. Neither the Sidewinder nor the Radar makes any real attempt to correlate their data. It's left to the pilot.

 

 

Sidewinders are relatively simple creatures. They see a heat signature, they lock onto it. Consider the scenario of two targets in close formation, one behind the other, the one in back on afterburner. The radar would have no trouble spotting the cold one and would likely be the one it targets. The Sidewinder looks there and may not even see the intended target, but would see the afterburner flare where it expects a target to be. It would signal the pilot that it has acquired a target, because that's what it does.

 

 

Congratulations, you've discovered the reason for the seeker uncage procedure :)

 

 

I don't know how faithfully it is modeled in DCS with the hornet, but basically the seeker is always looking for a signature to lock onto, even when slaved. If there's something tastier in the missile's seeker scan FoV, it will pick the tastier thing. When and how the missile locks onto target is a matter of programming, and it's not quite the same for all aircraft - in some aircraft, you have to deliberately uncage - in others, once there's a strong enough signal, the missile uncages by itself.

 

Thus why you'd uncage the missile to check the seeker track first, even when slaved.

 

This is also why generally you shouldn't shoot with flares or the sun inside the FoV - the missile will lock onto a target as part of the launch process, and it will probably not be your intended target.

 

@Lancel & GGTharos, what both of you are saying is true for the early versions of the AIM-9, but with the introduction of the "G" model with SEAM (Sidewinder Extended Acquisition Mode), the system is a bit more intelligent and provided the AIM-9 seeker head with 2 search options. The first allowed slaving the seeker head to the radar when locked when the missile is in the Caged/Slaved mode. The seeker would look in the direction of the radar for a heat source. If it detects the target, the pilot uncages the seeker to confirm a good lock and then launches. If the seeker does not detect a good signature, it would still continue "look" in the direction of the locked target while caged. If the pilot uncages the seeker, it is free to lock on to any target within it's FOV. The second option is Caged/Uncaged Bore-sight where the seeker is fixed to a bore-sight view when caged(our current capability) or when uncaged the seeker will mechanically sweep through a wide area for a suitable signature/target to lock on. I don't know how it functions IRL F/A -18C but that's how it works for IRL for the F-16C/D and F-15C.

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There should be some method for deciding which pointing source is used to cue missile: radar, helmet, or neither. It's a priority sequence, hands on control, menu selection or some combination. Who is steering the missile head around is not an ambiguous thing.

 

Slaved is not a state the missile should be in prior to firing. It's best practice for missile to self-track on the rail (although this isn't a strict requirement). When the missile is slaved, it's slaved and no amount of signal from the missile means anything. It's going to look where it is told to point signal or no signal.

 

At some point, usually before firing, the missile is allowed to self-track. This isn't slaved and absolutely the radar or HMCS or whatever source of pointing information can and will disagree with the reported direction. When not slaved the missile is "on its own."

 

The in between state is a "cocked" state with consent to uncage but is still slaved until TD saturates to allow self-track. This is useful for helmet cueing as the diamond will "stick" to a target but be slaved prior.

 

When and how this transition from slaved pointing to non-slaved self-track pointing depends on the design of the system. Possibly the F/A-18C requires that the pilot manually uncage (set not slaved) the missile. For AIM-9M/L that's usually in combination with threshold detect circuitry which inhibits uncaging until there's a saturated detection signal. Older AIM-9P have "auto uncage" which could uncage by saturated detection signal. AIM-9X? No idea as it has dramatically different concept of seeker. Probably it would be made in a way that functioned similarly to AIM-9M/L.

 

Anyway I expect that procedure for radar-cued AIM-9 is, track radar to target, AIM-9 symbol slews very close to overlaid, pilot commands uncage, AIM-9 symbol self-tracks onto target with a small angular shift. There's always a small difference between radar and missile LOS. Wings flex, the radar and heat center of gravity are different, etc.

 

Uncaging AIM-9 slaved to radar and having it jump to another source should be exceptionally rare especially with AIM-9X. Like if MiG-25 was in formation with Tu-95 and you're behind and you're using a heat-signal (not X) missile, yeah one is going to be hugely hotter and tend to pull the seeker over.

 

But AIM-9X? It's not even a heat-seeker. It's an imaging sensor like a Maverick. Unless the bodies of the targets are physically overlapping it's going to pick out the same thing your radar is telling it to point at every time.

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Yep ... and what I said is true of modern sidewinders. You don't know what it's going to lock onto until you check. 'Good signature' could be sun glare from the ocean. The missile has no clue.

 

 

This is why you shoot with flares and sun and other distractions out of the FoV - to ensure it picks the target you intend to shoot at. ECCM intelligence comes in after you're locked on, at which point it's easier to reject flares.

 

 

This is precisely why pre-emptive flares are used in all sort of engagements that involve heaters.

 

 

 

In any case, Frederf has given a much better treatment of how the details work out.

 

 

 

I don't know how it functions IRL F/A -18C but that's how it works for IRL for the F-16C/D and F-15C.

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Reminder: SAM = Speed Bump :D

I used to play flight sims like you, but then I took a slammer to the knee - Yoda

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