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Alternate launches of AIM-7 and AIM-120 under STT


EcceHomo

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Before discussing, please make two points clear:

 

1. AIM-7 is a semi-active guided missile (radar must be in PDI);

 

2. AIM-120 is terminal active guidance missile (radar can be MED/Hi PRF under STT/TWS).

 

 

 

Based on the above two points. Under STT, alternate launches of AIM-7 and AIM-120 may occur as follows:

 

1. AIM-7 launches first and AIM-120 launches later.

 

(1) Assuming that after launching AIM-7, switching AIM-120 (weapon switching button), the radar will maintain PDI. Then, the subsequent AIM-120 launch conditions may not be constituted, because the launch data need to be written to the missile before launching. In PDI, radar can't have ranging and can't get data. If the saved target data is used, AIM-120 will be launched under inertial navigation (without data link, it will not be able to update the target data), or will search for the target directly using the missile-borne seeker.

 

(2) Assuming that after launching AIM-7, switching AIM-120 (weapon switching button), the radar will not maintain PDI. Then, after switching to AIM-120, AIM-7 will lose its guidance illumination immediately ( switches to MED/HI PRF,the radar exits PDI ). AIM-120 operates normally (data link works normally).

 

2. AIM-120 launches first and AIM-7 launches later.

 

(1) Suppose that after launching the AIM-120, the AIM-7 (weapon switching button) is switched, and the radar will be switched to PDI. Because there is no ranging, after switching AIM-7, AIM-120 immediately loses its data link, and AIM-120 guides itself (inertia, monopulse, active seeker). If the memory trackfile is used in the data link, AIM-120 will get the updated data of the memory trackfile (radar calculation) in up to 8 seconds.

 

(2) Assuming that after launching AIM-120, switching AIM-7 (weapon switching button), radar will not switch to PDI. Then the normal launching conditions of AIM-7 will not be constituted. If AIM-7 is launched forcibly, it will enter the flood mode. AIM-120 lost data link updates and AIM-7 entered flood mode.

 

These are all possible scenarios. I don't have enough information to prove which one is right. I hope someone can come to the right conclusion.

In the game, AIM-120 and AIM-7 can be guided at the same time without any conflict. I don't think it's right.It is hoped that these discussions will be of some benefit to future improvements in guidance systems.

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[...] In PDI, radar can't have ranging and can't get data. [...]

 

 

Can you be a bit more specific at what you mean with PDI? Pulse-Doppler Illumination?

A question that follows from the first one is: Why is it not possible to have range information during SARH guidance? When using very simple CW illumination, this may not be possible but I was thinking that the target is illuminated at least in a pulsed mode. At least in DCS you still have range information after a sparrow launch

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in the real world would the aircraft ever have both AIM7 and 120?

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in the real world would the aircraft ever have both AIM7 and 120?

I doubt it or at least I've never seen it.

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Can you be a bit more specific at what you mean with PDI? Pulse-Doppler Illumination?

A question that follows from the first one is: Why is it not possible to have range information during SARH guidance? When using very simple CW illumination, this may not be possible but I was thinking that the target is illuminated at least in a pulsed mode. At least in DCS you still have range information after a sparrow launch

 

Right. There are two kinds of PDI for F-18, one is compatible (with burst ranging) and the other is full (without burst ranging). The latter only appeared after the launch of AIM-7.


Edited by EcceHomo
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Can you be a bit more specific at what you mean with PDI? Pulse-Doppler Illumination?

A question that follows from the first one is: Why is it not possible to have range information during SARH guidance? When using very simple CW illumination, this may not be possible but I was thinking that the target is illuminated at least in a pulsed mode. At least in DCS you still have range information after a sparrow launch

 

For HIGH PULSE-REPETITION FREQUENCY TRACK MODE without burst ranging, its value is flase. Burst ranging is a more accurate numerical value. Burst ranging occurs occasionally. PDI is a special HPRF mode, which may use FMR (FREQUENCY MODULATION RANGING).

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Does this mean that a less accurate range is provided during AIM7 launch, which is updated occasionally to a precise value by using burst ranging?

 

yep. But that's not the point of discussion. The point is that AIM-120 and AIM-7 cannot be guided simultaneously.

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  • 3 years later...
On 6/18/2019 at 7:25 AM, EcceHomo said:

These are all possible scenarios. I don't have enough information to prove which one is right. I hope someone can come to the right conclusion.

Sounds like OP is just speculating here based on public descriptions of the modes of the APG-73. I don't think that's enough for ED to change how its simmed.

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On 12/20/2022 at 5:11 PM, Hazardpro said:

Sounds like OP is just speculating here based on public descriptions of the modes of the APG-73. I don't think that's enough for ED to change how its simmed.

Anyways I've uploaded the evidence and there's two things that can be deducted from the manual:

1. AIM-7 guidance requires PDI waveform, while switching to PDI requires no AMRAAM inflight.

2. Using weapon selector switch to select AMRAAM would return radar PRF to interleaved, thus effectively exits PDI if AIM-7 is inflight.

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