The radar fix is a tricky procedure depending on the map in use. It uses the ground returns in Pulse radar mode to identify a peculiar and recognizable geographical spot. On such position a waypoint is also created, and the difference, in terms of Δ latlong, is the correction we are looking for.
Besides finding the geographical reference, the procedure is straightforward:
- TID CURSOR/CAP – Hook Desired Navigation Point for Update.
- PULSE SRCH button – Depress.
- On sensor control panel: STAB switch – IN. EL BARS switch – 1. AZ SCAN switch – As Desired.
- RDR FIX button – Depress.
- DDD CURSOR button – Depress.
- Action switch – Half Action (first detent).
- Cursor is displayed on DDD.
- Manipulate hand control DDD cursor over desired ground map point.
- Action switch – Full Action and Release. (This will cause the DDD cursor to remain at the selected position.
- Observe the delta for LAT and LONG on TID.
- If readouts are unsatisfactory, deselect RDR FIX and repeat steps 4 through 12.
- FIX ENABLE button – Depress.
It is important to set the full details of the waypoint (the latlong can be taken from the F10 map).
Setup: the F-14 is flying at 15,000ft, the waypoint was created over the small island of Arward, just a couple of kilometres from Tartus, in the Syria map.
Radar is set to Pulse Search, 1 Bar. If the INS is not completely off the chart, using the distance from the waypoint can be a useful tool to pre-set the antenna elevation angle at a meaningful angle. This helps the process as 1 Bar is quite narrow, depending on the range.
In this case, I used my in-game Kneeboard page to find the angle: the range from the waypoint is approximately 25nm, and the F-14 is flying at 15,000, so the angle is ~5.6°.
Now we can slew the antenna and focus of the returns on the DDD.
The figure below shows the DDD in Pulse mode returning the coast. The little return under the HCU DDD-mode pointer is the island. Remember that the DDD provides a “bent” representation of the topography, in this case, the coasts. This makes working using hills or peaks much harder than islands or coast-line peculiar shapes.
The next step is checking the delta:
- the left value is the ΔLATITUDE, it displays “LN” or “LS” depending on whether the delta is more to the North or South;
- the value on the right is the ΔLONGITUDE. Similarly to the ΔLATITUDE, it adjusts from the “side”, displaying “LE” and “LW”.
The closer the delta values are to zero, the less the INS has drifted. The next figure shows the deltas for this example.
When the suggested delta is deemed satisfactory, pressing FIX ENABLE updates the INS and the position of the F-14 is updated.
Compared to other INS Fix Update techniques, this is one of the less precise. However, if nothing else is available, then it is still a valid solution.
Unfortunately, due to how Pulse radar works and the lack of a proper air-to-ground radar, finding a recognisable point may not be an easy task. Luckily, water tends to not providing any return, so it is very easy to highlight a lonely island, a coastal feature (or even a ship!) in Pulse Search.