Using the Towed array in the FFG

[Sirkam]

I started my training with the FFG, and i dont know very well how to use the towed array (and of course, i take a look to the manual and i confused with the information). My problem is with the Actual/mirrored contact. How i know what is the mirrored and the actual contact?

[BobbyZero]

Originally Posted by Sirkam

I started my training with the FFG, and i dont know very well how to use the towed array (and of course, i take a look to the manual and i confused with the information). My problem is with the Actual/mirrored contact. How i know what is the mirrored and the actual contact?

Here is an excerpt form Landlubbers Survival Guide by Smaragdadler, it's an excellent PDF manual which can be found at www.subguru.com and I highly recommend it.

It deals with various platforms, but the following excerpt is about towed array on FFG and true contact resolving:

"Towed Array on FFG Perry:
First, as you likely know, the Perry's array is passive sonar detection only and shows half the
signal, because the other half is mirrored. You also might know, that the top of the waterfall is
the array's front, and the bottom is the rear. Simple ehough. Now, if you turn the array (by
turning the ship, obviously), your contact is going to move up or down the array. This is
regardless of it being the real or ambiguous, as, like I mentioned, the waterfall is oriented to
the array, and not to north like on a sub. So, what likely gives the headache, is how to tell real
from fake when the signal always moves? Well, like I said, the display orients to the array.
And, like a sub, you turn the ship, and thus the array, to resolve. Now, a simple thing is, if you
turn towards an object, the object gets closer to the front of you, and if you turn away, the
object gets closer to the back, correct? So, if you turn the array, and the target starts creeping
downward, you are turning away from the true contact. If the contact starts creeping upwards,
you are turning towards it. So, to make it simple: Turn to resolve. Contact goes up,
resolve in the direction of the turn. Contact goes down, resolve opposite the turn.
There is an exception if you actually cross its bearing line - by then it *was* the same as the
turn, but it *is* not."

[Sirkam]

Now, i understand it. For example: If i turn ownship to port and the line go up... the active contact is the same direction (port), but, if the line go down, the active contact is in the opposite side (starboard). Is it correct?

[goldorak]

Originally Posted by Sirkam

Now, i understand it. For example: If i turn ownship to port and the line go up... the active contact is the same direction (port), but, if the line go down, the active contact is in the opposite side (starboard). Is it correct?

Yes its absolutely correct. On the frigates sonar station, 0 (relative bearing) means the bow of the frigate, 180 means the stern of the frigate. So if you have a contact whose bearing line tends to 0 it means it is closing on the bow of the frigate.
Whereas if its bearing line were increasing towards 180 it would mean it is closing on the stern of the frigate.
By using a manouver (to port or starboard) and those 2 facts above you can infer on which side of the turn the different contacts are.

One thing has to be clear, the frigates sonar station is the only station in DW that uses relative bearings, all other stations (navmap, etc..) and all other sub units (and air units) when using sensors measure absolute (true) bearing.

A relative bearing of 0 always points to the bow of the frigate.
A true bearing of 0 always points to north (in one spefic case relative and absolute bearing coincide but in general they don't).

[Sirkam]

I know the difference between relative (the direction of the FFG's course, the bow) and true (the magnetic north) bearings.
I think i should start practicing.... Maybe the kilos mission in the Iranian gulf? :hmm:

[goldorak]

Originally Posted by Sirkam

I know the difference between relative (the direction of the FFG's course, the bow) and true (the magnetic north) bearings.
I think i should start practicing.... Maybe the kilos mission in the Iranian gulf? :hmm:

Create your own training mission (for the frigate). Something simple.
Or go to subguru and download one of the many scenarios, there is a training scenario made by Molon Labe...(but this one is for subs)

[Sirkam]

Ok, i'll try it.