Ground Mapping & Navigation: Some Tests

Old topic I wanted to discuss awhile ago but never found enough time to do so. It is one of those marginal/niche but are so interesting because are fundamentally never used, but can turn a dire situation and save your skin.

I briefly mentioned the Ground Mapping capabilities of the F-14 here. This article goes deeper into this topic and, hopefully, helps to understand the limits and the possibilities of the AWG-9 in this vest.

The Pulse Search mode of the AWG-9 can map the terrain. Unlike Pulse Doppler, it returns everything that reflects energy back to the antenna, terrain included, and displays those signals on the DDD (in AZM vs RNG). The resolution of the DDD is not great when compared to modern or dedicated radars (e.g. there are no “shades” depending on distance/altitude, it is either black or white) but it can be used with some success, especially when pointed towards the coastline or a ship.
The image I posted in the article I linked above gives a good idea of what the RIO sees in such situation:

rio-24-AWG9-WCS-Advanced-p4-ground-mapping

The DDD stretches the image a bit, contrary to the TID, but the features are still quite recognizable and the ship is very easy to spot (it can also be locked to provide an additional reference for the pilot).

F-14 != Tornado IDS

As long as we stick to basic employments, such as the one describe above, everything is quite easy and, at the end of the day, the results are quite acceptable. When we talk about doing the same job as an ad hoc radar, well, not much so.

DDD Repeater?

The biggest issue the crew faces is the lack of a DDD repeater in the front. The Pilot is blind and when I say blind, I mean literally: when travelling low in a valley and through fog or clouds, the Pilot can count of a short list of friends: namely the RIO, the Radar Altimeter and a couple more indicators. No equipment help him to follow and avoid the terrain. Therefore, the RIO has to literally micromanage the Pilot, even the slightest corrections can be important when flying in such conditions. Good crew coordination is paramount.

Staring at the whiteness

The second issue in terms of impact on the workflow is the lack of depth: the DDD displays only the returns as a bistable, and not, for instance, in shades depending on the distance or altitude. Therefore, it all comes down to the skills of the RIO and his ability to build a mental picture of the surroundings.

The lack of depth also comes with another big issue: understanding if an opening on the DDD is a curve in a valley or the radar simply can’t see behind a crest is not immediate and requires some work. A solution is asking the pilot to turn a few degrees to a side or another or slew the antenna to wider angles.

ground-mapping-pilot-view
The nice view from the pilot’s seat..

Making your life easier

The AWG-9 WCS has a number of tools that can come very handy when trying to emulate a Tornado IDS (ED, F4 and Tornado pls!).

STAB

The stabilization of the antenna can be deactivated in Pulse mode and this allows the RIO to see the terrain where the aircraft is pointing, rather than having the antenna stabilized with the horizon. This sounds like a nice feature, on the other hand, human pilots tend to adjust the altitude and the attitude quite often and this can drive off the picture of the RIO. It is certainly a good option though, especially when descending.

Bars

The radar can scan up to 8 Bars. As we may remember from the BVR Sanitization discussion, a full sweep can take a lot of time. Moreover, due to the lack of depth and distance indicators (in the vertical plane), the result would be a DDD showing lots of returns all over the place. Therefore, it is better to scan the area where the F-14 is going to fly, and this is best achieved by means of a single Bar.

The height of the Bars is not proportional because they overlap slightly. Quoting the manual:

1 bar being 2.3°, 2 bars 3.6°, 4 bars 6.3° and 8 bars 11.5°

Recalling the Antenna Elevation study, we can approximate the height in feet at a certain distance using again some simple maths (yep trigonometry again!):

HEIGHT/2 [ft]
BARS HGT[°] 5nm 10nm 20nm 50nm
1 2.3° 1220 2440 4881 12202
2 3.6° 1911 3823 7646 19114
4 6.3° 3354 6708 13416 33540
8 11.5° 6181 12362 24724 61810

Anticipating the dive

Since the RIO can hardly see what is exactly under the belly of the aircraft (and it would probably result in a pitch-black DDD), the best way to descend is anticipating the dive itself by lowering the antenna and focusing on the next few miles of terrain ahead. I suggest changing the angle often to get “a feeling” of where the terrain is (a sonar would be handy here 🙂 ).

Raising antenna when flying level

As we have seen, the cone of the antenna can be quite wide as the distance increases (when seen from the side). Left in the default position (elevation 0°), it will illuminate a good chunk of terrain in front and below the aircraft. Due to the lack of depth, the RIO can’t easily understand the altitude of such returns. Therefore, when flying at constant altitude, raising the antenna a bit is a very effective workaround for the problem. The angle depends on how far you want to scan the terrain: 2° seems to be working quite well as a general setting but eventually it depends on the terrain itself.
That being said, the RIO should never fossilize on a single value and keep moving the antenna to understand the terrain ahead.

A simple test

The following is an improvised experiment we put together, we had other plans so it started as a joke, but we actually enjoyed this flight.

As this test proves, flying in these conditions require some preparations.

  1. Pilot with life insurance: in other words, a pilot crazy enough to trust and happy to rely entirely on you.
  2. Flightplan: I placed 4 WP in the most critical areas of the flightpath: entrance of the valley, first crest, second crest, exit (although I decided to use only 3 of them eventually). Those WP have to be carefully placed (and also make sure that the INS is accurate). Getting lost is so easy with zero visibility.
  3. Maps. I realized this immediately as we started our flight through the valley: Maps are desperately needed. For instance, it makes understanding if an opening on the DDD is a curve in the valley or the radar is getting blocked by a crest a much easier task.
  4. NS430: maps works, but the GPS works even better due to the possibility of zooming, on top of following the aircraft automatically. The NS430 proves again to be a nice little module (if you are a VR user, check if it works now). Although real life crews used portable GPS (e.g. Garmin Pilot III) as they became available, you will very rarely use the NS430 in the F-14.

I plan to fly something similar again at some point, using either a detailed map or the NS430 to follow the progress. This is by no means something the F-14 is meant to do but it is a lot of fun (for the RIO, at least 😛 ) and who knows, perhaps it can come handy at some point.

ground-mapping-NS430
NS430 and DDD

As usual, I hope you enjoyed. Feedback and comments are always more than welcome 🙂

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