Airborne Operations Manual - Sensors

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Acoustics Station (P-3C - Key “F2” / MH-60R - Key “F3”)

P-3C Accoustics Station

The P-3C Acoustics station is the larger brother of the MH-60R Acoustics station shown on the next page. It will serve as an example for the handling of both stations. However I will present the Acoustics station of the MH-60R later on and go into the differences between them.

Grams

The Acoustics Station gives you access to your most important sensors, the sonobuoys. As you can see on the image, you have 16 Grams (2x8) available, which means you can monitor up to 16 buoys in OMNI Mode (marked green) or eight buoys in DIRECTIONAL Mode (marked blue) or five buoys in ACTIVE Mode (marked red). You will soon learn to appreciate the NAV map feature, where sonobuoys with a contact within range, will go “hot” (means they display a red dot in them). That is very helpful, especially when you have to cover a lot of ground with them or you have a lot of buoys out. To be honest, this is far from reality, because in real life you need to monitor the buoy to notice it going “hot”, plus tactics that spread the buoys out, like this manual suggests sometimes (if not all the time), wouldn’t work in real life either. But then, this is just a game. A good idea is, to try and keep the number of buoys dialed in as low as possible, that way you can easily switch modes or call up a buoy fast, without having to switch around a lot. Just keep those buoys that show “hot” and which you suspect have a submarine nearby, dialed in. If you select channel 00 (marked white) the Gram will show NO SIGNAL and can either be used as a supporting Gram for Directional/Active Mode or you can dial in a buoy of your choice.  

Frequency Alerts

I recommend printing out the Appendix A, as you will need that information during a mission. The frequency alerts (you have four available – one of them is marked black) basically just notifies you, that one of your buoys (only dialed in ones) has a line in the Frequency Range you have set as alarm. It won’t tell you which Gram though. That’s something you have to find out for yourself. Frequency alerts work even when you don’t have Autocrew enabled. However, assume you are hunting an Akula-II submarine in a moderate density Environment, means you have a couple of Freighters, maybe a Tanker or a Trawler and the occasional military ship around. The Akula-II has 5 frequencies: 50, 125, 320, 1125 & 1886, and you have only four possible frequency alarms available. Means you can select up to four frequencies to dial in, if you are only hunting for the Akula-II. You will notice that you can’t dial in anything over 1200Hz, because that’s the max range of the buoys, therefore you are limited to 1200Hz. That’s no biggie though, since to see those high frequencies (given that the buoys could display them), you would have to be practically on top of the submarine. So all you can use are the first four frequencies anyway. And here comes the other big problem: The Akula-II isn’t the only platform with the combination of 50 & 125 Hz in its Profile, no Sir – the Fishing Boat, Powerboat, other submarines and surface ships have them too. And if you are in the above mentioned environment, chances are good, that your alarms will go off, but not because you have found the Akula.

Then there is the problem of getting more than one or two frequency lines. You see, most of the subs are pretty sneaky and if you are lucky you will get the first or even the second frequency line. If you are good, you will track him and place your buoys accordingly, that will let you classify him with lines three and four. Anyway, if you use your frequency alarms, you have to take a look at your tactical situation first. Sometimes you can dial in the lower frequencies and it’ll work, and sometimes you better start with the 3rd or even 4th frequency as alarm, or otherwise you end up with a lot of false alarms.

MH-60R Accoustics Station

The Acoustics station on the MH-60R is both in DW and the real life a lot more cramped than the P-3C Acoustics station. Space doesn’t matter for us, but the reduced capabilities do. Let’s see where the differences are.

The Acoustics station of the MH-60R has only two Frequency Alerts instead of four on the P-3C, however the handling is the same. The more important restriction is the number of displayable grams. Unlike the P-3C the MH-60R only has 4 displayable grams – no more and no less. This means that you can only monitor one DICASS in ACTIVE mode (remember, you need three grams for that – one for the actual display and two as support) or two buoys in DIRECTIONAL mode (you need two grams for that – one for the display and one as support) or four buoys in OMNI (or four BT buoys at the same time) mode.

While this might sound like a hefty problem at first glance, you have to realize that the buoys are only your secondary sensors on the MH-60R. The primary sensor for the MH-60R is his dipping sonar, which is nearly as capable as a towed array from a submarine or the FFG and can actually reach much farther down then the VLAD Deep, your deepest diving sonobuoy. Sure, you can use the sonobuoys just like in the P-3C, but you have a lot less of them and as you have already seen, it’s a lot harder to keep track of them in the MH-60R. So be patient the dipping sonar station on the MH-60R will be discussed shortly. 

Sound Gradients and Propagation Paths

In this game there are 3 distinct Sound Speed Profiles (SSP) modeled, Positive, Negative and Isothermal. To find out what the actual SSP in your Operating Area is, you need to drop a BT buoy (P-3C, MH-60R, FFG) or a XBT Probe (All Submarines).

The image above shows the return of a BT buoy in deep water. As you can see, the layer at the place where the buoy was dropped is at 462ft which is marked graphically (red) and displayed in numbers (blue). Important here is not only to know where the layer exactly is (in this case 462ft), but what general conditions you are operating in – which you can see in the graphical display - to determine probable distances to target. As you can see later in this chapter, depending on the SSP in the operating area you might discover contacts out to 30+ nm (pending some patches to the game).

Layer depth is defined as max sound speed at max depth above the thermocline. The important thing to remember about sound is that it is lazy and will seek an area of low sound speed. In the above example, sound originating above the layer will tend to be trapped in that area or duct. If your sonobuoy is shallow (above layer) and your target is deep (below layer), the chances of a detection are minimal.

Along with this chapter consult Section 5-Training, pages 5-3 to 5-19 in the Dangerous Waters manual to learn about things not mentioned in here but necessary for game play.

Sound Velocity Gradients

Positive Image 1-1

Negative Image 1-2

Gradient consists of sound speed either decreasing (image 1-2) or increasing (image 1-1) at a constant rate with growing depth. In regard to the sound waves this means they either bend toward the bottom or toward the surface. In the case of an isothermal environment, the sound speed is constant from the surface to the bottom with little or no change. An example of isothermal would be the Persian Gulf. The entire water column acts as a duct with sound propagating in all directions. Sound will primarily be bounded by the two physical barriers of the surface and the bottom experiencing loss at all interactions.

Surface Duct

Image 2-1

Image 2-2

Surface Duct means that there is a thermal layer present. Because of this layer the majority of the sound waves will be reflected towards the surface (assuming the sound emitter is above the layer), while the rest will pass through the layer, but will bend like light rays when going through glass (Image 2-1). As a result you will have problems detecting submarines that are below the layer from above.

Convergence Zone

Image 3-1

Convergence Zone means that the Sound waves will be refracted or bent due to increasing pressure. In order for CZ to exist, sufficient depth excess must exist. Generally, a minimum of 200 fathoms (1200 feet) below the sound channel must be present for reliable CZ to exist. The effect of this is, that you will be able to detect Ships/Submarines out to 30 or 40nm or more. Imagine the whole thing as donut-shaped rings centered on your buoy. There may be one, two or more convergence zones available.

In contrast, Bottom limited is defined as a sound channel without sufficient depth excess to support CZ. In most cases this will result in a Bottom Bounce (BB) propagation path being formed. BB can also extend detection ranges. However, each interaction with the surface or bottom will result in signal loss.

Sonobuoys

Sonobuoys are small, self-contained sonar systems. They are dropped into the water by aircraft at which point they deploy themselves. The information from the sonobuoy is transmitted to the aircraft by VHF radio link. The information can also be relayed to ships. Signal processing and analysis is performed by equipment in the aircraft, or ship. After some period of operation, the sonobuoy will scuttle itself.

Most sonobuoys can operate at several preset depth settings. The shallow setting is used for surface duct propagation, and the deep setting for sound channel propagation. Sonobuoys have poor directivity indices, mostly because of their limited size. Their figure-of-merit is not always low, however, because sonobuoys also have very low selfnoise. Depending on the environment, and whether or not self-noise is dominant, sonobuoys can actually outperform some larger hull-mounted systems (Principles of Naval Weapons System, p. 222).

Sonobuoy Deployment (Source: Principles of Naval Weapons Systems)

The game models five distinct buoy types: LOFAR, DIFAR, DICASS, VLAD and BT. The player can employ all with the exception of LOFAR buoys, which can be used in game though, if the Mission Designer has put them in. With the exception of the BT buoys you can set the buoys either to Shallow or Deep (Depth is dependent on the actual buoy - more on this later). To make the right decision you have to balance the deployment time and the sensor range of the buoy against your current needs, and of course the available depth. Shallow buoys take roughly 2 minutes to deploy and send data from the moment they hit the water and deep buoys take roughly 4 minutes to deploy and send data. To make your life easier in finding the right distance from the targets datum to the deployment position of your buoy of choice, you can either use the 3-Minute Rule

Distance (traveled in yards) in 3 minutes = Speed (in kts) x 100

or take a look at the chart in Appendix D : Close in Buoy Chart. The Chart in Appendix D shows the distances for two and four minutes. With some training and a bit of luck you will be able to place your buoys right on top of your target when they start sending data. For more information on the individual buoys check the Dangerous Waters™ manual, Section 5: Training. Keep in mind that buoys will go “hot” if something is within its detection distance which in turn is based on the current acoustic conditions at the spot, i.e. SSP, water depth and so on. This of course doesn’t mean they will show any lines in Omni or a dot in Directional right away. They just go hot in the NAV Map. This is a very useful feature and will be discussed in the Tactics section later on.

Further, buoys have a Lifespan of two hours, they lose power and sink to the bottom (and drop from the NAV map) after the time is up. Additionally, the contact to your buoys depends on Line of Sight communication, means if you are beyond the visual horizon the connection to your buoy will be lost, and you will get an “Out of Range” in the gram of the respective buoy.

BT (Bathythermograph) Buoy

The BT buoy is your tool to gain the actual SSP of the operating area. No depth preset - it drops to the bottom regardless of the depth.

DICASS (Directional Command Activated Sonobuoy System) Buoy

The DICASS buoy is your most important buoy in the game against SSKs. It doesn’t have a greater detection range then the VLAD, but it is the only buoy in the game to have an Active as well as Passive Mode which is especially helpful against slow moving Diesel Submarines. Shallow = 90ft / Deep = 800ft

DIFAR (Directional Frequency and Ranging) Buoy

The DIFAR buoy is your buoy of choice when it comes to Littoral waters (or simply shallow waters). It has similar capabilities to the VLAD, though due to the Environment it works in, the detection range is shorter compared to the VLAD. Expect a max. of roughly 6nm in optimal conditions. Shallow = 90ft / Deep = 400ft

VLAD (Vertical thin-Line Array Directional Frequency Analysis and Recording) Buoy

The VLAD is your buoy of choice for the deep blue. It works best in depths exceeding 1500ft and has the greatest passive detection range among the available buoys. If you are on a deep water hunt, this is your buoy of choice, the deep version should be able to go beneath most of the layers you will encounter and help finding the lurking subs there. Take note, if you try to use it in shallow waters you won’t hear anything as the buoys will be buried in the mud. Shallow = 600ft / Deep = 1200ft

LOFAR (Low Frequency Analysis and Recording) Buoy

This buoy offers only Omni Directional Mode. Aside from that you can’t choose it as load out. The only time when you will use a LOFAR buoy, will be, when the Mission Designer places them in the mission.

Marking contacts with your buoys …

You can only mark contacts in Active or Directional mode. To mark a contact you have to click on one of the points or at the same level in the Gram (in Directional mode), so a horizontal line goes through the point which represents one of the frequency lines of your contact of interest. Then click “Mark”. If it’s a new contact, this action generates a bearing line with an Unknown Contact marker at the end. If that contact was already established on this buoy, the bearing line on that contact will shift to represent the bearing change, assumed there was one.

If you want to mark a contact using an Active buoy you have to transmit first. Then wait till you see a spot (might be big and bright or even small and hard to see) that looks different than the normal background. Click that spot and hit “Mark”. If it’s a valid (new) contact, then the contact will get a new number and will be placed in the NAV map with a bearing line and an Unknown contact marker. The Active buoy gives you both bearing and range; the bearing line will vary in length according to the distance of the contact to the buoy.

On top of this, even when you have marked a contact, you have to update him manually – all the time, unless you have Autocrew activated (They will updated every 2 minutes). That’s where a 2nd player comes very handy, because together, one guy can concentrate on hunting and shooting, while the other one can concentrate on keeping the contacts up-to-date.

Dipping Sonar (MH-60R – Key “F7”)

MH-60 Dipping Sonar Station - Passive

As I mentioned already, when you are driving the MH-60R your primary sensor is your dipping sonar. It has its own station which you can see on the image above. You can switch between Active and Passive mode by pressing one of the two buttons at the top of the screen. The Passive mode works more or less like the Narrowband station in a sub. The bottom half of the display shows signal strength of the sound received by the dipping sonar. Even without any contacts you still see the “Background Sound” of the ocean. Draw your mouse from left to right and vice versa to look for discrete frequencies which (if they exist) will be displayed in the top half of the display. For a further description of this part of the station read page 8-35 and following in the Dangerous Waters™ manual.

Take Note : Always come to a hover before starting to dip as well as reel the sonar in full before flying onwards. While you can fly within limits with the sonar in the water as well as when the sonar is out of the waters it is quite risky and if you screw it up you just lost your most important ASW sensor.

Tip : Use headphones when working at this station, that way you might be able to distinguish the type of your contacts more easily as well as find them in the first place.

MH-60 Dipping Sonar Station - Active

For a full description of the functions of the active dipping sonar see page 8-36 in the Dangerous Waters™ manual.

The same rules that apply for use of the DICASS buoy (in active mode) do apply to the active mode of the dipping sonar as well. The advantage of turning it on is that you more or less immediately get a good fix on your target including bearing and range. The drawback to this is that your target is now aware of your presence (at least the direction where to look for you) and if it’s an aggressive skipper (who is rather close to the surface) he might decide to pop up and shoot a SAM towards you (given that he is within range).

Therefore you have to carefully weight your choices … are you desperate and can’t find your target but out of whatever reason you have to … and now, well then you might be compelled to use the active mode. Or maybe you are on your final attack run and need that last fix to nail him for sure, again this might be a reason to turn on active. Be aware that once you pinged your target he will most likely start evasive maneuvers and thus screw up your solution (on which you worked for the better part of the last 30 minutes).

This should guide you in carefully deciding upon your course of action and not to act in an unplanned manner. You have only three torps at max. (before you have to go for a reload) so better make em count. And don’t forget the subs are able to shoot back (within limitations) and can ruin your day in a heartbeat especially if you are hovering 50ft of the deck a mile away from your target.

Last but not least, remember this is a game … some of the tools the airborne units have are exceedingly powerful (the DICASS and Hydrophone) and if you wanna ruin the game by employing gamey tactics … so be it – but don’t expect to have many people to play with if you do that.

MAD/ESM (P-3C – Key “F4” / MH-60R – Key “F6”)

P-3C MAD/ESM Station

ESM

The ESM is a passive Sensor. It relies entirely on your distance to the emitter and the signal strength. Plus, just like with Radar beams, you are limited by the horizon, means the higher you are the more you can “see”. If the signal is too weak you will only see that there is something, but not what emitter it belongs to. Next to the size of the Wedge you can gain the strength of the signal from the Signal Strength Indicator below the ESM monitor. Basically, the more colorful it gets the bigger is the signal you receive (and the closer is probably the transmitting platform). You will get the info about what Transmitter it is (in this case an AN/SPS-55) and which classes of platforms have such a transmitter. Sometimes it’s just one, but more often then not, you will get a bigger list of platforms and have to choose for yourself the appropriate one. Once you hit “Mark”, the contact will appear on the NAV Map with a LOB. If you classified him, he will have the classification marked in the list “Known Classes”.

If you think you have found a sub, then you can fly down the bearing and maybe catch the sub on the surface (or eat a SAM). Be careful when you try something like this. It’s pretty dangerous and you should have a Maverick ready. But without anything that gives you the distance to the sub and therefore a location, better stay away and try to localize him. Once that’s done, send him a greeting, by way of a Maverick or two - if he is still on the surface. Otherwise he will most certainly welcome your torpedoes. You could use your Radar to pinpoint his location; however that gives away your position as well. Either way, be very careful.

Illustration of the MAD Limits in the game.

The MAD/SAD Sensor (see manual page 9-15 for details) in the game works up to an altitude of 1000ft (Ownship). Best employment altitude is 300ft at which you have roughly 1000ft coverage below the surface (see above left). Further you are in the middle of a 1000ft Corridor, so you can detect submarines up to 500ft to either side of your Aircraft (above right). The SAD has less range then the MAD. SAD coverage will be down to roughly 750ft depth.

Since this sensor is located on your tail, you have to actually fly past the submarine before you get a reading. You don’t have to turn on Autocrew to be notified of a MAD detection. If you get a MAD hit you will hear “MAD!, MAD!, MAD!” from your crew and it will show in the chat/messages window as “Mad!, Mad!, Mad!”. On top of that you will see a new Unknown mark on the NAV Map. If you have already detected that particular contact with your MAD sensor, then the old marker will be moved to the new location. Therefore it’s advisable to immediately mark the location of a MAD return (as described in the tactics chapter) and classify the contact as good as possible.

Since this sensor reacts to large chunks of metal in or on the ocean, you will get hits when you fly over or fly close to surface ships as well. Surface ships will only generate a MAD return, while submarines generally give you a MAD and a SAD return. The exception to this rule happens, when a submarine dives below the maximum SAD Range. Example for that would be a Seawolf diving at Max Operating Depth. Even if you fly at 300ft or lower you won’t get a SAD return. Remember, whenever you get a MAD call, check the MAD readout for SAD and compare with your tactical picture. If you get a return and nothing can be found on the surface, chances are pretty good that you stumbled upon a submarine, even if you don’t get a SAD return (that only means it’s pretty deep).

If a submarine is trying a “Down Periscope” and hiding beneath a surface ship, you will get two Unknown Contact markers in close proximity along with a SAD reading for one of them.

--OneShot Jan. 2008 (EDT)