Thanks for the link, now let's see if I interpreted it correctly.
My thinking is total speed across LOS=OSSpeedAcrossLOS+TgtSpeedAcrossLOS . And bearing rate is just the rate of degress per minute change you observe in the sonar station.
So, I'm calculating ekelund doing this:
sinLA+[TgtSpdXsin(90-AspctAng)]/BrgRate
That X is me multiplying, not a variable BTW. And LA=Lead Angle.
My head hurts.
Got my definitions from this page
http://www.tpub.com/content/combat/1.../14308_170.htm