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AIM-7F/P/M


Chizh

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GG, you used the term "english bias" several times - what does that mean, I never heared that before?

 

Or is it just a mistype and you meant "angle bias" (which, in my non-english-native-speaking ears, would make at least some sense in the given context)?

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GG, you used the term "english bias" several times - what does that mean, I never heared that before?

 

I'm not him, but I learned that word as a non-native speaker when playing virtual pool games where it is how much off center you'd hit the ball, forcing it to rotate while it travels (e.g. for getting curved shots). That's how I understand what GG describes, the missile will get a general direction to steer to and how much until it picks up the radar reflection for guidance.

dcsdashie-hb-ed.jpg

 

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^^^^

 

That is correct. English bias is the steering command loaded into the missile by the WCS, and it is one of the first things that the missile executes. English bias is removed some time after the missile's seeker locks on (ie. switches to whatever guidance method) or after some other condition is met.

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  • 1 year later...

GGTharos,

 

have you ever seen any evidence about AIM-7E/F/M maneuverability?

I found only datasheet for AIM-7C and I know that AIM-7E-2 was the first version of AIM-7 which maneuverability was increased, but no idea how much.

 

15 G of AIM-7C look much better than 10 G of AIM-9B/E

But 20 G of AIM-7M from some references don't look like a great improvement in comparision with 22 G of AIM-9J/P/L/M

 

http://alternatewars.com/SAC/SAC.htm

http://alternatewars.com/SAC/AAM-N-6_Sparrow_III_SAC_-_30_July_1960.pdf

853907667_AIM-7Cmanuverability.png.4f736655f5f22ee033adbb060fde00c0.png


Edited by Святой
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Hello,

 

 

I can look through my sources but I haven't kept track of what information is where :(

 

 

For AIM-9L we have a maximum structural loading of 40g, and the control surfaces are able to exceed this at low altitude and high speed. At higher altitudes g becomes limited.

 

 

AIM-7E upgrade included change of fin shape to reduce the amount of power required to pull 25g, IIRC - here the limitation is hydraulic power required to move the control surfaces. So the AIM-7E will be 25g capable, which is not very surprising.

 

 

I don't remember seeing missiles in DCS pull maximum g. This may be because of interaction of lift, drag, and permitted AoA for the missile.

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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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Hello,

For AIM-9L we have a maximum structural loading of 40g, and the control surfaces are able to exceed this at low altitude and high speed. At higher altitudes g becomes limited.

Structural limit may be really far from value of maximal lateral capability.

For example for AIM-9J only 20 G is available. This modification was specially developed to increase its ability against maneuvering targets. I haven't read that the AIM-9L is so much capable than AIM-9J.

Fully deflected control surfaces may really make missile to maneuver with increadible load factor, but there are other limitations: actuators, seeker, gyro and other components, which may work not good enough with high load factors, missile stability, autopilot limitations.

 

AIM-7E upgrade included change of fin shape to reduce the amount of power required to pull 25g, IIRC - here the limitation is hydraulic power required to move the control surfaces. So the AIM-7E will be 25g capable, which is not very surprising.

For AIM-7C it is written that fully deflected fins allow the missile to reach 15 G. No idea if I must understand it as a lateral capability given for AIM-9J or different. For AIM-7E/F I would like to read docs if they are available somewhere in the Internet.

 

https://archive.org/details/DTIC_ADA486826/page/n35

1132410378_AIM-9EandJ.png.fa01b1976adae99fe185da99a2435498.png

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Structural limit may be really far from value of maximal lateral capability.

For example for AIM-9J only 20 G is available. This modification was specially developed to increase its ability against maneuvering targets. I haven't read that the AIM-9L is so much capable than AIM-9J.

Fully deflected control surfaces may really make missile to maneuver with increadible load factor, but there are other limitations: actuators, seeker, gyro and other components, which may work not good enough with high load factors, missile stability, autopilot limitations.

 

 

For AIM-7C it is written that fully deflected fins allow the missile to reach 15 G. No idea if I must understand it as a lateral capability given for AIM-9J or different. For AIM-7E/F I would like to read docs if they are available somewhere in the Internet.

 

https://archive.org/details/DTIC_ADA486826/page/n35

 

 

AIM-9L has structural capability of 40g. Control surfaces are able to generate higher load factors (the graph is cut off at 40g). There is good information for 9L.

 

 

I will see if I can find relevant information for you for AIM-7. I know 7E had modifications to the fins to allow up to 25g load factor, and the reason was that with the unmodified finds the actuators could not create enough toque to reach 25g.

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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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  • 1 year later...
On 10/16/2018 at 4:08 PM, GGTharos said:

To answer your question without you having to read the rest of this, maneuver restriction is stated to be accomplished by reducing the PN constant. In some cases (such as loft) there are additional restrictions to prevent the missile from maneuvering much while it is gaining altitude and speed.

 

 

Pure PN-guidance is not optimal for long range launch due the missile decceleraton after engine burn-out.

To achieve the maximal possible launch range the PN-constant must be adjusted in-flight to keep the missile trajectory as straight as possible. With the proper launch leading of course.

For short-range launches it is not needed

 

PN.png

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Welcome back 🙂

 

Yes, there are many ways to deal with restricting PN, as well as new research into DG algorithms, mid-course guidance algorithms etc.

[sIGPIC][/sIGPIC]

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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  • 1 year later...
On 10/16/2018 at 3:10 PM, Chizh said:

Do AIM-7 sort of adaptive proportional navigation or changing params of navigation in the flight?

Maybe late models M/H?

From what I found, proportional navigation was implemented to not only "late" models, but "F" version also:

AIM-7F_Sparrow_CS_-_January_1976.pdf

AIM-7F_Sparrow_III_SMC_-_January_1977.pdf

image.png

@GGTharos Please, I have a question about Autopilot of "M" version (source https://www.designation-systems.net/dusrm/m-7.html):
The autopilot enables the AIM-7M to fly optimized trajectories, with target illumination necessary only for mid-course and terminal guidance.
And also about radar uplink of "P" version:
The AIM-7P features improved guidance electronics and on-board computer, has a new radar fuze, and has an uplink to the autopilot for mid-course guidance updates.
Which I guess resulted in "P" ability of target necessary illumination only for terminal guidance. (I think that I have red somewhere, that R-27ER have something simillar.)

These two major improvements make totally sense to me, and actually this can be an answer how the designers of the missile make late models deadlier in comparison with early models - shining on enemy RWR just from the moment of leaving the rail. The 1976 Kub-M3 (SA-6) with its 3M9M3 missile have also this ability required CW ilumination only on terminal phase. ("M" become operational at 1982 and "P" at 1987 as per Wiki)


Edited by GumidekCZ
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What is the question?  Is it 'can I launch this SARH missile without causing an RWR warning?' then I would say no.  Not for the R-27, and very likely not for the 7P.  There are things that must happen in the WCS and the missile that require STT.   While these things are subject to change (tm), there's no indication that such a change has occurred.

The data-link allows launching the sparrow beyond the dynamic radar cue estimate among other things; it's not a means to achieve stealth.

[sIGPIC][/sIGPIC]

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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  • 2 weeks later...
On 6/28/2022 at 4:06 PM, GumidekCZ said:

@GGTharos Please, I have a question about Autopilot of "M" version (source https://www.designation-systems.net/dusrm/m-7.html):
The autopilot enables the AIM-7M to fly optimized trajectories, with target illumination necessary only for mid-course and terminal guidance.
And also about radar uplink of "P" version:
The AIM-7P features improved guidance electronics and on-board computer, has a new radar fuze, and has an uplink to the autopilot for mid-course guidance updates.
Which I guess resulted in "P" ability of target necessary illumination only for terminal guidance. (I think that I have red somewhere, that R-27ER have something simillar.)

These two major improvements make totally sense to me, and actually this can be an answer how the designers of the missile make late models deadlier in comparison with early models - shining on enemy RWR just from the moment of leaving the rail. The 1976 Kub-M3 (SA-6) with its 3M9M3 missile have also this ability required CW ilumination only on terminal phase. ("M" become operational at 1982 and "P" at 1987 as per Wiki)

 

One major factor in launching missiles is seeker sensitivity. This was a limiting factor for the 7F which could barely see past 20 nm. New seeker on 7M is not just more sensitive and can pick up targets from much higher distances, it also does not (itself) need to see the target. This would imply lock on after launch capability, but you still require STT lock for the missile to go in the right direction.

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The F,M require lock right after launch.   The P may not.   The F was indeed limited to ~20nm, for a 2m^2 target.  Don't count on it not seeing your fighter armed with 50 of everything 😄

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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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