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Old 03-16-2019, 04:21 AM   #11
IronMike
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Hi guys,

this is not a bug, but simply how realistic RWR works (not talking about the bug where 1 radar triggers lock for everyone, this seems to be a separate issue within DCS and not related to the Tomcat). It only knows there is a launch and it does not know whether this launch is on you or not. That it picks off launches from so far, is due to how these launches are being emitted in DCS: if they paint you, the RWR will respond to it, and with some radars that can be very far.

That other RWRs "know" which launch is on you and which not is rather not realistic. Also note that the F14s RWR coverage does not have dead zones, its inaccuracies come from other reasons.

This is not necessarily in direct reply to your question anymore, but please check out this overview written by our Grover, who designed the RWR:

The procedures/logic:

- Four sensors/antennas for the radar bands of tracking radars and airborne radars.
- Each antenna FOV is ~180° (or slightly more), and almost a perfect cone.
- The sensitivity at the edges of the cone is significantly lower than in the centre.
- When we get a message from DCS about being radiated, we simulate the signal it produces in each sensor. This includes factors such as the distance from the emitter (attenuation), the angle of arrival for each antenna, noise and other random signal amplitude fluctuations.
- From this moment we treat the signal as if we didn't know about the true parameters of the emitter and we only use the information from the emulated sensors (the previous step).
- We take the amplitude of the signal from each sensor, apply signal to noise cuts, combine and reconstruct the threat direction.
- Then, the reconstructed direction together with the signal signature is compared with the list of threats already being displayed. If we find one that correlates, we update its direction. Otherwise, we create a new threat and inform about it with the 'new guy' sound.

Some consequences of the procedure described above and a bunch of other features:
- No blind spots. However, if directly above or below, the threat has to be significantly closer (compared to the horizontal plane) to pass the SNR threshold.
- The direction is reconstructed in the 2D plane (the local aircraft frame of reference). For threats significantly outside that plane, their reconstructed direction may be inaccurate, and it usually shifts towards the 12, 3, 6, or 9 o'clock from the true position.
- The direction reconstruction accuracy improves as the distance from the emitter decreases. For the scan modes of the emitter (RWS/TWS), it's somewhere around 10-15° RMS.
- For the emitters in scan modes, a misassociation of a known-threat with a new signal can happen, and it occurs quite often, especially at long ranges. It can result in:
a) ghosts (fake threats) appearing on the display - more probable if you or the threat do some manoeuvres;
b) merging a group of two or more threats of the same type into one threat. For example, a group of two Su-27 flying in close formation, both scanning with their radars, can appear on the screen as one '29' until they get closer.
- A malfunction/damage of one antenna/sensor doesn't make you completely blind in that direction, as the two adjacent antennas should still cover that area. However, the lack of that sensor makes the direction reconstruction procedure very innacurate, and it's very likely that some threats will be displaced by more than 90°.

Compared with the default RWR from DCS:
- An entirely new dedicated code, written from the grounds up.
- Antenna/electronics emulation.
- Threat reconstruction using the emulated signals.
- Enhance information obtained from the engine with more details (radar modes, missile guidance, noise etc.).
- No blind spots.
- Imperfect like a real device should be, and not a god's eye.
a) Some weak radars can appear late.
b) The directions will be inaccurate.
c) It will be harder to estimate the number of threats of one type when they form a group.
d) You'll receive launch warnings not only when you are the target of the missile. For example when flying in a close formation with your buddy; if an enemy launches a weapon such as AIM-7 or SA-6 at your buddy, you may receive a launch warning from that threat as well.
- Detailed failures/damages.

Another thing to consider with the RWR is that the antennas move with the control surfaces, which means that this will roll your RWR picture, just as when you are maneuvering the aicraft, the RWR picture will roll with it (and might display erronous contacts). This requires additional pilot skill to take RWR readings at the proper (level) moment in the maneuver in order to keep up an accurate SA as well as an eye to spot wrong readings in between.

I hope this helps with understanding the RWR better.

Best regards, IronMike
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Last edited by IronMike; 03-16-2019 at 04:27 AM.
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