Ka-50 A-10C – Sharing Data IV: Bearing & Distance and Final Thoughts

The last part of the guide covers an alternative method of sharing a target (or, more precisely, any point) location. The reference point must be known by both parties (it can be the bullseye or an IP, just to name a couple). This method is not precises as latlong coordinates but it’s worth knowing nevertheless.


Bearing and distance

Lat/long coordinates actually are not the only way to provide the location of a target to another aircraft. As you can see in the picture regarding the ERBL, both bearing and distance are displayed besides lat/long coordinates. However those data are referred to your position, which usually changes often. Fortunately we can choose a different reference point, pressing the “MARKER” FSK. This point can be, e.g. the Bullseye used by A-10s or an IP, previously communicated and inserted with the PVI-800 (as the picture below shows).
The “MARKER” function can be activated only when the ABRIS is in ERBL mode. First of all place the ERBL cross over the Bullseye or the reference point. Now press the “MARKER” FSK. The cross will turn in a triangle, a new one will appear and all you have to do is just move it over the target. Distance and bearing to target (as well as other data) are real-time calculated.

Providing bearing and distance can be useful sometimes, but is not an accurate method. Each step you follow adds an error, which increases considerably over long distances. Moreover, bullseye coordinates saved via PVI-800 aren’t precise and the approximation introduced rounding heading values can result in an error that can be calculated as:

Position_Error = Range * Bearing_Error [in radians]

Therefore ½ degree of bearing measurement error would result in ~8.7m position error per kilometer of range from the reference point.

Moreover remember that Ka-50s use True bearing, but A-10s use Magnetic bearing. Therefore you have to subtract the magnetic declination value (MVR) every time you provide a bearing. Also remember that default unit of measurement for distance is in metric system (km).

However bearings and distance combination can be useful, especially to provide an approximated indication of target’s position. For this purpose a distinctive geographical element close to the target can be efficiently used as the reference point.

sharing-data-4-bearing-distance
Bearing & Distance from the ABRIS

Final considerations

Even if A-10s and Ka-50s haven’t a common system which should allow them to share data directly, there is more than a way to move around the problem. Summing up, the Ka-50 can use:
1. ABRIS to provide lat/long coordinates;
2. ABRIS to provide distance and bearing;
3. PVI-800 to provide lat/long coordinates;
All you have to do is choose the most performing way, basing your evaluation on your task and the situation around you.


Additional final thoughts

This guide is definitely old; there are so many new aircraft in the DCS’ skies compared to when I wrote it. Nevertheless we lack a real attack helicopter besides the Ka-50 and that makes this platform a niche yet a still relevant module.
I plan to write a similar guide for the Mi-24P and the AH-1S, depending on the capabilities of their simulated avionics.

Aye, it will take a decade 🙂

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