|Weekend Project| Spent some time over the weekend doing a basic mapping of the DCS F-16 Viper maximum “buggable” ranges against a hot aspect, fighter-sized target.
Intention to open discussion about DCS F-16 FCR data with the community and invite others with similar data to share their own.
Topics particularly interesting: look-up penalty, low-altitude penalty, static ranges in large areas of radar testing.
Information and M.O.
Please take a look at the full test here (Google Sheets viewer link). It includes Conditions, Methodology, Data, and Graph representation of results (this to focus on).
OBJECTIVE
Familiarize with DCS AN/APG-68 useful ranges, find optimal ranges and altitudes for long-range bug and target, observe any altitude combinations (ownship/target) where look-down, look-up, or low altitude penalty is exacerbated and avoid. Intention to record MAXIMUM BUGGABLE RANGES for hot aspect, fighter-sized targets under changing altitude conditions.
CONDITIONS
RWS Situational Awareness Mode, Azimuth 1, 2-Bar, ATA/TA = 0, Attacking Aircraft F-16CM at Mach 0.8, Target Aircraft F-16CM at Mach 0.8, Varying Altitudes AGL for test, Over Flat Land (Syria map, vicinity of H3), Standard Atmosphere and “None” weather.
METHODOLOGY
Single Player missions with ownship and/or target altitude adjusted, target is AI set to “Do Nothing”, maintaining the stipulated AGL value with speed of Mach 0.8 flying direct into ownship aircraft with waypoint placed directly over tester spawn. Tester spawns and engages autopilot altitude hold (verifying radar altimeter shows intended AGL value of test) and steering select direct to waypoint placed over AI spawn (creates TA and ATA value of zero). Tester configures air-to-air master mode and selects A1 and 2B in RWS, with antenna elevation adjusted to illuminate target in radar scan zone. Throttle setting selected to maintain Mach 0.8. When FCR displays target return, time is slowed to play at 0.25x speed. Tester rapidly depresses TMS Up until target symbology changes to show a bugged track in Situational-Awareness Mode, immediate pause, then record mileage (SR) shown in HUD to the bugged target. Repeat until data set complete.
Disclaimer: Data is only relevant under the specific conditions of over-land hot aspect fighter and target (ATA/TA both zero) against a target with the RCS of the DCS F-16CM Viper (4m2), with closure created by both ownship and target both maintaining Mach 0.8
Data Charts
The collected data points are represented in the following charts… (See Google Sheets Viewer link above for more details and raw data)
Grey Region: Extreme Low Altitude Penalty Zone – very closely clustered with average of 13.4 nm (exactly 1/3 max range)
Orange Region: Gradient Low Altitude Penalty Zone – gradient and smooth transition from 34.6 nm to 20 nm as ownship altitude decreases and low altitude penalty is incurred. Rate about 6 nm range loss per 1,000′ ownship descent
Blue Region: Look-Up Penalty Zone – very closely clustered with average of 36.6 nm (91.5% max range)
Green Region: Full Range Zone – very closely clustered with average of 40 nm (max range)
Purple Region: Look-Down Penalty Zone – very closely clustered with average of 26.4 nm (exactly 2/3 max range)
Graph shown with data points plotted:
Graph shown with data points removed and co-altitude reference line:
Credit to Jacob ‘Nerf’ Thomas of Digital Coalition Air Force (DCAF) for graphs created from this data set.
Observations and Commentary
It seems that the DCS Viper’s implementation of the AN/APG-68 pulse Doppler radar contains several static zones in which maximum track SR remains constant despite large changes in altitude for both ownship and target. Mapping these zones has shed light into the build and implementation of the system.
There absolutely is a look-up penalty. When in the Blue Region of the data set, a user will attain a maximum track range of an averaged SR of 36.6nm (8.5% range loss for look-up appears to be static with ownship at or above 5,000′ AGL).
Look-down penalty appears static as well, with an averaged SR of 26.4nm for the entirety of the Purple Region, even with target altitude below 5,000′ AGL. In fact, the data appears to show that with ownship at or above 5,000′ AGL and in look-down, there is no dynamic change in track range outcome from target altitude at 23,000′ down to 1,000′.
Most noteworthy are the results from ownship operating below 5,000′ AGL, as this sheds light into the Eagle Dynamics modeling of the sidelobe effects on MPRF radar at low altitude.
With ownship at or below 1,000′ AGL, the data shows a static maximum track range of an averaged 13.4nm SR regardless of target altitude (again all average track ranges seem to be the same value, and within the margin of tester error, suspect static values). At ownship AGL of 2,000′, the value increases to 20nm, which begins the Orange Region, in which there is a near-linear observation of about 6nm range gain per 1,000′ climbed (to max out at 34.6nm). This region is the only observed dynamic region modeled in the AN/APG-68 in this test.
Image formatted for DCS kneeboard file.
More data and variables (TA or RCS in example) are welcome and I encourage anyone interested in this topic to replicate the conditions, or create their own and share their findings.
Brody
For questions, comments, or collaboration I am available by DM at Discord: Brody Zachary#1944
This guest article was written in association with DCAF (Digital Coalition Air Force). Interested in flying with us? Check us out on our squadron page and Discord.
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