FCR to Detect and Track at 0 Closure Rate?
-
Hello guys,
Does F-16’s FCR in BMS see/show AA targets when @Zero closure rate? Say you’re flying behind a target 20nm out with exactly the same speed? (0 Doppler effect situation)
Also what does FCR see/show in Look Up and Look Down situations at 0 closure? Particularly in Look Down (when there is a lot of ground clutter)?
Is it implemented realistically in BMS?
Thanks!
-
You are flying at 300+ kts … and the FCR computer knows this … so a return with doppler-shift of 0 means it reflected off something in front of you also flying 300+ kts
The clutter on the ground will be blue-shifted +300 kts. But the plane flying along in front of you won’t be. So, easy to spot.
The hard case to consider is a plane flying 90° aspect … down low with ground clutter – both plane and background will be blueshifted +300 kts
I don’t know the answer to how realistically BMS models this, but want to clarify the problem statement
-
For what it’s worth in DCS FCR can’t see targets in front unless closure rate is over +/-150kmh in Su-27 and Mig-29, being r/w limitation.
-
I don’t know how it is in the Viper, but the F-14 does have a filter at zero closure rate, which they say is used to reject returns from the ground directly below the aircraft. Other aircraft using similar radar tech presumably have it, too, but I don’t know, maybe it’s different in the Viper.
-
BMS does replicate a ground return Doppler notch filter for our F16. In the game, you may notice that when a contact “notches” (turns 90 deg to your flight path), they disappear from your RADAR.
-
That is the typical situation when beaming……the target in that case must have a positive closure rate because it is getting closer to you at a closure rate similar to the ground.
The question asked is somewhat different…when an aircraft is flying away from you at the same speed…the target might have a closing velocity of zero to you… but the ground doesn’t thus the reply from airtex sounds on point.
As to whether the ancient AWG-9 could deal with that I expect you need the radar supplement marked Secret.
-
As to whether the ancient AWG-9 could deal with that I expect you need the radar supplement marked Secret.
Fair point, at least we could learn how it is modelled in BMS?
-
That is the typical situation when beaming……the target in that case must have a positive closure rate because it is getting closer to you at a closure rate similar to the ground.
The question asked is somewhat different…when an aircraft is flying away from you at the same speed…the target might have a closing velocity of zero to you… but the ground doesn’t thus the reply from airtex sounds on point.
Its quite possible to get sidelobe returns which do have zero closure. MTR setting adjusts how wide the zero velocity notch is, I forget the numbers exactly. MTR HI, its a wide notch, MTR LO, its a thinner notch (possible to pick up cars on highway as “contacts” in A-A mode).
-
Fair point, at least we could learn how it is modelled in BMS?
I know how was modeled in the past but I have 0 data about what could happened in BMS4 code.
If you wish to know what I know I can post it but I have to say there are things which is better to not known by players because it can ruin the immersion and the “pretended environment”.
-
I know how was modeled in the past but I have 0 data about what could happened in BMS4 code.
If you wish to know what I know I can post it but I have to say there are things which is better to not known by players because it can ruin the immersion and the “pretended environment”.
If you don’t mind sharing - shoot a PM, molni
Thanks!
-
Its quite possible to get sidelobe returns which do have zero closure. MTR setting adjusts how wide the zero velocity notch is, I forget the numbers exactly. MTR HI, its a wide notch, MTR LO, its a thinner notch (possible to pick up cars on highway as “contacts” in A-A mode).
Yes, these sidelobe returns can mess up Dopler filter.
-
Its quite possible to get sidelobe returns which do have zero closure. MTR setting adjusts how wide the zero velocity notch is, I forget the numbers exactly. MTR HI, its a wide notch, MTR LO, its a thinner notch (possible to pick up cars on highway as “contacts” in A-A mode).
Pass on how well sidelobe clutter is handled in that situation.
If both have to be at the same speed for this scenario then both are likely to be above the F-16s stall speed, which is above the selectable MTR values (for the 66……no eyed deer on the 68 ).
Sabre what exactly are you doing?..formation flying at distance? can you expand on why this is such a problem for you and no one else?
Does DCS:Radar drop the track for the one second you are at the same speed and then reacquire when the speeds change? (or do they all work like the MiG-29 you mentioned? historical 1980s Soviet Radars ?? ) Assume you are talking about other jets.
-
Does DCS:Radar drop the track for the one second you are at the same speed and then reacquire when the speeds change? (or do they all work like the MiG-29 you mentioned? historical 1980s Soviet Radars ?? ) Assume you are talking about other jets.
No, in DCS actually it is +/- 150km/h closure rate behind a contact that your MIG/SU27 FCR can’t see it to replicate rw behavior. Fascinating isn’t it? Well, became curious comparing apples to oranges.
Thanks.
-
Interesting. Do you get a line of contacts at the range corresponding to your altitude? This is what the ALT TRK blanker is supposed to suppress for the F-16.
-
Do you get a line of contacts at the range corresponding to your altitude?
Could you elaborate or rephrase?
Thanks
-
Say you are flying at an altitude of 5km, do you get a line of radar returns 5km away?
In the F-16, you can get sidelobe returns at the range corresponding to your altitude. If you are flying at 18,000 ft, you can get a line of returns at 3 miles range, with 0 closure rate (not sure if this is modelled in BMS - it wasnt in the past). The ALT TRK tracker blanker inhibits display of contacts at the range corresponding to your altitude, so you dont get a line of contacts at the bottom of the FCR (potentially hiding real returns from aircraft at the same distance as your altitude).
-
Got you, sounds like just a special case in respect to the soviet FCR. Doppler filter is much more coarse in the soviet jets then (no surprise here), which is simulated in DCS as I mentioned. But there is Interleaved/HPRF/MPRF control that can help to somewhat fine-tune Doppler’s filtering in Mig-29 and Su-27.
Thanks!