need track replay Is the sparrow affected by flares and chaff?

[Indianajon]

Hi all, I've recently noted in my tacview replays that the sparrow appears to have become more susceptible to counter measures which has got me confused. My understanding is that the Aim-7 was basically slaved to the aircraft radar so as long as there is a good lock then it shouldn't matter.

I had a good solid STT-PD lock throughout the intercept from about 12 miles through to the merge and fired 2x sparrows, both of which tracked most of the way and then when for the C/M. 

Is this correct or is it a recent bug? It might be because it's happened repeatedly recently that I'm more conscious of it but it does appear to have only been an issue recently. 

[twistking]

34 minutes ago, Indianajon said:

My understanding is that the Aim-7 was basically slaved to the aircraft radar so as long as there is a good lock then it shouldn't matter.

I think you have a missunderstanding on how the Sparrow works. The Sparrow is not so much guided by the launching aircraft's radar, but homes in on the radar's return. It may home on chaff released by the target as long as the chaff gets illuminated by the launching aircraft.

[Dragon1-1]

Countermeasure modeling is currently rather simplistic, it will go for chaff because each chaff is a "dice roll" that determines if the missile is decoyed or not. Chaff does work on Fox 1s, but it should probably be more complex. IRL, it can also disrupt the radar lock on older radars.

[Indianajon]

51 minutes ago, Dragon1-1 said:

Countermeasure modeling is currently rather simplistic, it will go for chaff because each chaff is a "dice roll" that determines if the missile is decoyed or not. Chaff does work on Fox 1s, but it should probably be more complex. IRL, it can also disrupt the radar lock on older radars.

Thanks. If it had disrupted the lock I would have understood more but as I had a solid lock throughout and thought that is all the Sparrow looked for i was a little confused. I guess as you say it might be due to a more simplistic model. Thanks

[twistking]

1 hour ago, Dragon1-1 said:

Chaff does work on Fox 1s

What? Are you sure?

[Dragon1-1]

IRL it does. It can both disrupt the lock and provide false reflections to the missile. How effective that is depends on how advanced ECCM is on that particular missile.

[Northstar98]

8 hours ago, Indianajon said:

Hi all, I've recently noted in my tacview replays that the sparrow appears to have become more susceptible to counter measures which has got me confused. My understanding is that the Aim-7 was basically slaved to the aircraft radar so as long as there is a good lock then it shouldn't matter.

Not exactly.

The Sparrow is a semi-active homing missile - what happens is that your radar illuminates the target and the Sparrow tracks the reflection. Think of it kinda like a cat chasing a laser spot - the laser (radar) emits radiation (which will be visible light for the laser and microwaves for our radars) which reflects off of the target and into the cat's eyes.

8 hours ago, Indianajon said:

I had a good solid STT-PD lock throughout the intercept from about 12 miles through to the merge and fired 2x sparrows, both of which tracked most of the way and then when for the C/M. 

Is this correct or is it a recent bug? It might be because it's happened repeatedly recently that I'm more conscious of it but it does appear to have only been an issue recently. 

As Dragon1-1 said, countermeasures are just probability. Each missile has a coefficient that determines how likely it is be decoyed or not.

I believe the coefficients can be found under ccm_k0 = x in the respective .luas of the missiles (can be found here).

Here are the ccm_k0 values for all Sparrows in DCS:

• AIM-7E: 2
• AIM-7F: 1
• AIM-7M: 0.5
• AIM-7M(H): 0.5
• AIM-7P Block I (II, as per hoggit?): 0.5

Edited July 3, 2022 by Northstar98

[nighthawk2174]

The spparow's also home in on doppler, they track using a speedgate.  This should provide good resistance against chaff considering how quickly they loose speed. 

[BIGNEWY]

Hi 

if you think there is a bug please include track replay examples and any evidence that something is wrong. 

thank you

[Indianajon]

16 minutes ago, BIGNEWY said:

Hi 

if you think there is a bug please include track replay examples and any evidence that something is wrong. 

thank you

Hi Bignewy, I put it up here in the first instance as I wasn't sure if it was a bug or my not understanding how the Sparrow worked. As has been shown above its my knowledge at fault rather than the modelling.

Ta

[Northstar98]

1 hour ago, nighthawk2174 said:

The spparow's also home in on doppler, they track using a speedgate.  This should provide good resistance against chaff considering how quickly they loose speed. 

Yeah, AFAIK it has is 2 antennas; the seeker in the nose that receives a reflection from the target and another in the rear that receives the illumination directly.

The Sparrow does a comparison which allows it to determine speed (which I guess will be a sum of the target's and missile closing speed) and it then uses a speed gate to track that (with angle being tracked via receive only conical scanning (up to F), or inverse monopulse (M and onwards)).

Edited July 3, 2022 by Northstar98

[Cmptohocah]

In DCS you can think of chaff as basically flares for SARH. They don't influence the targeting radar but rather the missile.

[Northstar98]

9 hours ago, Cmptohocah said:

In DCS you can think of chaff as basically flares for SARH. They don't influence the targeting radar but rather the missile.

Yeah and ARH, only a few modules (namely the Mirage 2000C and Tomcat) factor them at all it seems (or at least in a way that's obvious).

Edited July 4, 2022 by Northstar98