Help me understand the realism of Aim-7 Sparrows modeling in this game

Machinery of War Discussion
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I always found very weird how the Sparrows behave so differently from any other SARH, in some situations resulting in worse performance than even R-3R and Aim-9C, even when launched from an aircraft with good radar.

From my understanding, the sparrows from C to M have no way of receiving data from the mothership. Relying solely on return strength, closure rate (doppler shift) and proportional navigation to meet with its target.

From that, I assume such a seeker would have no way of distinguishing if a target is hot with a certain closure rate, or cold with the same exact closure rate. After all the doppler shift would result in the exact same return frequency, and as long as the target is not against the terrain, the return would be very distinct.

So why does in this following example, in the Right approach the missile can perfectly see the target, while in the Left it can’t? In both cases the target is against clear sky, at about the same distance and closure rate.

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Not only that, but in the Left example the missile doesn’t even try to stay its course scanning its original launch direction in case it find something. It immediately starts steering left, with the seeker just pointing in a random direction, resulting in no chance of ever finding the target along the flight path.

There are many other SARH’s without IOG and DL in the game, still the Sparrows are the only ones behaving like this. Is there a particular functionality these have in real life to justify this? Or is it another case of Gaijin having more documentation on it, thus modeling weaknesses other less documented missiles don’t clearly state?

EDIT: Another extra question. Why does Betty says “Lock!” when the missile clearly is not “locked”? No way “Lock!” means the missile’s seeker has just been slaved to radar, right?

EDIT 2: Another another question. Why other SARH missiles get the fictitious sidewinder noise to tell the player when they have proper lock (red circle), but the Sparrow doesn’t?

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One of the targets is coming head-on, the other one is flying to the side.
Generally, 90% of SARH missiles like head-on and sometimes tail-on shots, but are otherwise allergic to side shots.

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I dunno how true it is, so take it with a grain of salt, but I have heard that Sparrows HATE shooting down for some reason, and early versions did have horrid shoot to kill rates (like under 10%) although to be fair it was a new weapons system, it takes time to learn how to best deploy it, but even in the Gulf war with M&P variants it was still about 3 missiles per kill.

I think it just means the seeker is hot (or maybe tracking a target), although see says it when I hit the button again to turn the seeker off, so I assume its just to warn pilots they have activated their weapons.

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I think I haven’t stressed enough how this behaviour is UNIQUE to the sparrow and other missiles that are on paper even worse than it, have no problems. Look at this example with the R530, one of the worst SARH in the game, still manages to track a perfect side-aspect, as long as there is no terrain behind the target. Meanwhile the Aim-7F/M can only do it from significantly closer ranges.

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In fact, why should any radar missile be unable to track a target when there is absolutely no clutter behind it? Regardless of being hot or cold, there is only one clear radar return. Almost all SARH’s follow this logic, but not the Sparrows.

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None of them play a noise…

You have to use the radar in sim to know if the missile will intersect your target.

On the other side of this, the AIM-7 is artificially nerfed in the head on aspect because of a single early phantom manual stated that large tight formations would mess with the radars tracking.

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the R530 for example literally does the lock noise of the Aim-9’s. Many others do. Go into the game and try it.

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There are two types of ARH seekers in WT: CW or Pulse. In this case I think all the other missiles you’ve compared to the sparrow here are pulse ones (R-3R, AIM-9C, R530 non D version?), with the sparrow the only CW here.

CW only is able to resolve velocity. So from the missile’s point of view, every return signal can only be characterized by its radial velocity. A notching target (radial velocity close to 0 m/s) therefore is able to blend in ground clutter returns from sidelobes (these sidelobes are in direction off broadside from the antenna, so radial velocity of these returns may clutter up near 0 m/s). In your example in the first image, with same radial velocity of the target, it’s still different. Because ground clutter radial velocity in the left case is high (hard to distinguish between ground and target velocity), whereas ground clutter radial velocity in the right case is low (easily discernable from high radial velocity of target).

Pulse radar, in this case it’s a low PRF one, and perhaps likely also incoherent with the older radars, are only able to resolve distance. In this case a far away target can easily be separated from close ranged ground clutter, so a notching target can be tracked. It will have issues though in the situation where the target is similar range to another/ground clutter inside the receive pattern, which in a near horizontal case is only a small moments of its flight, which it passes quickly enough usually to matter.

At closer ranges in both cases, target return is significantly higher than clutter return, so it is able to ‘ignore’ clutter. In look-up cases (where sidelobe returns do not return ground clutter), both should work against notching targets by virtue of having just no clutter.

Anyways it’s important to understand that radiation patterns (either in receive or transmit) are not just a single beam, but form extra (weaker) beams in other directions at the same time. So in all of these cases, there is still some clutter potentially. Idk how in depth WT goes into simulating radiation patterns and target returns (which produce sidelobes themselves too when analyzed through an fourier transform). But it’s pretty certain at least that WT does simulate sidelobes in some way.

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Is it the R530E? If it, maybe it’s because it’s a Thermal seeker.

I have never had any radar missile give a tone.

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I believe TRK MEM is a result of that.
Not to mention some plane’s radars giving launch/track pings while you’re behind them
F-14 does this most frequently

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My brother in Christ. Go into the game, pick any plane with the R530 (not the E), and hear it with your own ears.

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Now go play sim

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Interesting. But would that effect be so significant even when pursuing a target flying at 10.000m altitude, from below? Because from my experience the missile lose the lock at about 8km away, which isn’t much more compared to the 3 to 6km when locking at targets below 3000m.

Also, when measuring the lock against the targets in test range, the missile is able to lock easier when looking down (with your aircraft higher than the target) than looking up (with your aircraft lower than the target). Which would imply the side lobes reflected from ground cause much more interference than the ground clutter of the main lobe. The R-23R behave like that too (and I imagine the R530D too).

Maybe Gaijin coded this interference to be a function of the difference in altitude between both aircraft instead of absolute altitude. Thats why it seem to produce the same effect at low and high altitudes?

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That sounds like a bug more than anything else. To my knowledge no SARH should give tone and no other SARH i’ve tested so far does.

You can bug report it here (just search a bit first so that you don’t report something that is already reported and known about): (Gaijin.net // Issues)

A guide on how to report bugs can be found here: ([Navigation] Technical Knowledge Base | War Thunder Wiki)

Also, SARH missiles depend heavily on the aircrafts radar and it’s ability to track the target, i recommend looking at server replays with the sensor view on to see how the missiles tracker is acting and how your planes radar is acting, it can give a lot of insight.

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and all of them are early SARH missiles that are carried on jets without proper symbologies for them

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R-3R does for example bc the Mig-21 didnt have any indication of showing the quality of a lock thats why they “reused” the IR lock tone

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Well. Most Sparrow carriers also have no way of knowing quality of lock. And different from the others that simply refuse to shoot if there there is no lock, the sparrows don’t care, they shoot anyway, which I think is one of the biggest reasons people complain so much about it. Its like the other early missiles have a lot of guard rails to help players, while sparrow doesn’t.

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might be the case for the front cockpit
but the guy in the back probably had some way of telling

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I am not sure how Gaijin coded this all, so I can only really answer from the physics itself.

Idk if you’re referring in the first case about CW or pulse. So idk how to answer it.

Okay so this is about CW seekers. This makes sense depending on what the target aspect was. In look-down, against a single target against ground: the target has doppler shift of own movement + target speed, ground clutter only has doppler shift caused by own movement. Because the missile is far from the ground, sidelobe return is very weak, so only mainlobe return is of concern. And as metnioned, ground has quite a different doppler shift from the target, so easily separable: target can easily be locked. If the target is notching however (target closure rate is similar to that of the ground), then the target can not be detected.

In look-up, where the missile is close to the ground at least, sidelobe return from the ground is significant (because it’s close nearby). Target doppler shift = own movement + target speed, mainlobe ground clutter = own movement only (in look up, this is pretty much zero because there’s no ground in the sky), but sidelobe clutter closure rate = ~0 m/s (distance to the ground underneath stays constant). Which means in cases where target closure rate = ~0 m/s, because own movement and target speed work out to be near 0 closure rate, that sidelobe clutter from the ground and target blend together. This is why if you fly at similar speed as the target in a chase, CW SARH seekers will not lock well when sidelobe clutter plays a role. Notching targets should maybe on the other hand be able to get locked in look-up, while close to the ground, but actually sidelobes may still cause returns from the ground at ~own velocity, which may obscure notching targets still.

Idk still how sidelobes are modelled, but they do cover many angles, so you can kinda think of it as a sphere almost when it comes to the ground.

Example of radiation pattern:

Spoiler

This is for a theoretical antenna array of isotropic elements and approximated dipoles. Only the front hemisphere, but rear is just a mirrored version. In reality the rear side would be heavily attenuated in most cases as there will be things blocking it.
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With larger antennas, we have a finer spread of sidelobes and also more. So you can kinda just imagine they are everywhere.
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WT often uses -20 dB sidelobe attenuation value as per the datamines for most SARH missiles. This means the sidelobes are 100x weaker than the mainlobe. But power scales with range to the fourth power. So if the target is only ~3.16x further than the ground, the ground return is at the same level if you assume the ground RCS is the same as the target, which it isn’t.

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You can see how much of the outer ring is filled.

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Sorry, I meant from inside the cockpit in Sim mode. The only thing we get is Betty saying “Lock”, which she says at whatever distance and not when there is an actual lock.