When I started flight training in the US Navy, if you wanted to see a US Navy VP crew really start sweating, you needed to go aboard and watch a JULITREX (JULIE TRaining EXercise).

Before nuclear submarines became the norm and launched thirty years of blue-water, deep-ocean, passive submarine tracking, there were the diesel boats. Lots and lots of diesel boats, such as the Soviet Whiskey Class. Propulsion limitations meant that early diesel boats snorkeled often, presenting two detection opportunities to the MPA crew. Snorkeling was very noisy and very dirty. This permitted the luxury of dropping sonobouys and then listening to what sounded like a freight train with a frozen wheel as the typical Kaloma 37D diesel engines pounded away. Another detection and tracking option was Sniffer, a neat device that literally tracked a submarine by noting when the airplane cut across the sub's diesel exhaust. However, whether located acoustically or aromatically, once the sub realized that you were overhead, snorkeling ended and things got much trickier.

Running only on battery now, the sub would beat feet and try to lose the airplane. A sub's electric motors are very quiet. Sniffer immediately was useless, as was any passive sonobouy in the area, unless by blind luck the sub ran over it. This reduced the crew to active tracking, and this is where the story gets really interested, and where it loops up to the present day.

To track a fleeing submarine that is not producing much noise, you have to make your own noise. At the time, this required "Julie" -- active acoustic tracking. As soon as the crew realized that the sub had been alerted and was bugging-out, the PPTC (TACCO) would tell the PPC (PILOT) to wrap the plane around in a 2-G, 60-degree angle of bank turn, more bouys would be dropped, and a series of gut-wrenching racetracks at low altitude would begin. Coming back across the bouys as quickly and as frequently as possible, the TACCO would drop a SUS -- a Sound Underwater Source (a fancy name for a stick of dynamite with fins on it) -- NAV would mark the drop point on his Dead Reckoning Trace, and the acoustic operators would listen and watch for the results. If the sub was approaching the bouy, an up-doppler range circle would be generated; if opening the distance, the range circle would be down-doppler. If two bouys were being used, the detonation would be heard first at the master bouy, and subsequently at the slave bouy, generating an elliptical range. Where two ranges intersected, you had an ambiguous fix -- two locations, one of which was the location of the sub at the time of the last detonation. Another set of bouys and more fish-bombing might resolve the ambiguity. Of course, while you were busy doing this, the sub was running at top battery speed and zigging all over the ocean, trying to get away, so your unambiguous fix most often gave you some idea where the target was some minutes ago. If the crew could get a tentative course and speed on the sub, confirmation might be made with the magnetic anomaly detector ("MADMAN!" MADMAN!") so that a weapons drop could be accomplished. Not an ideal situation for weapon delivery, and few other events could more quickly reduce a cocky, experienced crew to sweating, lock-jawed intensity than Julie.

Well, the joy is back. With the switch from the USSR's deep-water nuclear submarine force, requiring almost purely passive acoustic tracking, to today's gaggle of countries each with one or more modern diesel submarines, active tracking is again important. Just one enemy submarine can ruin your entire carrier task force's day. Littoral ASW against a diesel-electric sub is ASW at its most difficult. Today's diesel subs are even quieter than their earlier counterparts. The older diesel subs commonly used a diesel-reduction drive when surfaced or snorkeling, which linked the diesels directly to the propellers through a transmission and generated a fair amount of noise. Today's diesel subs, even when running their diesels, use almost exclusively diesel-electric drive, whether snorkeling or deeply submerged, in which the shafts and propellers are driven by electric motors rather than by noisy mechanical transmissions hooked to the diesels themselves. Further aggravating the job of the MPA crew, ASW in shallow water adds additional challenges due to bottom-bounce, ducting, sound absorption, and other factors. The good news is that Julie is gone, replaced by "pingers," sonobouys that generate their own sound source and can be reprogrammed from the air. This allows for quick deployment of multiple active sound sources, and where three of more range circles from pingers converge, the crew has an unambiguous fix on the sub. Of course, the sub is still beating feet, trying to escape, but pingers are so superior to the old Julie system that the MPA crew has a much better chance of converting to a MADMAN or other sensor track and subsequently killing the target. That's the good news. The bad news is that it is increasingly difficult for the modern MPA crew to stay ASW proficient with ASW having become just one of a dozen or so current missions for which the crew must train. Sniffer is gone and JULIE was a bear, but in the "old days," a bear well known. – gps333@charter.net