In a previous post I talked about the Sensor 1 & 2 Acoustic positions. The other AW aboard is the Sensor-3 Operator. His job is to monitor and analyze the data from the non-acoustic sensors. These include the Radar, ESM system, MAD system, LLLTV, and FLIR systems. In addition he collects and passes along the data from the BT buoy, as it’s recorder is located at his station.
His primary job, or at least the one which occupies most of his time is using the APS-80(P-3a/b); or, for the P-3c, etc, the APS-134/135 (or other) Surface Search Radar. This system has two antennas, one in the nose, and one in the aft compartment, which have a coordinated 180-degree sweep. There is shielding between the two to protect the crew and instruments, etc from the radiated energy. Although it is more complex, having to use two separate magnetrons, and calibrated gear systems to maintain a 360-degree sweep, the design has a couple of advantages. For one, the radar is internal and doesn’t require a dome or protrusion, which means less drag. Secondly, if the forward radar should fail inflight, the aft system can be physically swapped out and the crew continue with at least a forward-sweeping system.
The ESM system allows the Sensor-3 operator to detect electronic emissions from other radars. It gives the crew a head’s up that someone else is radiating, and, based upon the pulse width, pulse strength, sweep, etc, the Sensor-3 can tell what type of radar it is, and likely who is operating it. The P-3’s that I flew on did NOT have any jamming capability. The ESM system was a passive system designed to provide warning of potential threats so the crew could take appropriate actions.
The MAD system stands for Magnetic Anomaly Detection. This is a sensor designed to detect variations in the Earth’s magnetic fields caused by large ferrous objects, such as a ship or submarine, moving through them. Remember how, as a kid, you learned to magnetize a screwdriver or other object by stroking it against a magnet? Well the Earth is a huge magnet, and every vessel that moves through those fields develops a magnetic field as well. Once a year or so, in fact, Navy ships and submarines are “degaussed” in order to remove that built-up field.
Anyway, the MAD system is located in the tail of the P-3, in that long “stinger” sticking out the back. That’s so it can be placed as far away as possible from the Orion’s own magnetic signature. In fact, it is so sensitive that special tools made from beryllium are used when working on it so as not to impart and magnetic distortion during maintenance. The actual readout consists of a backlit scrolling paper with a small metal wand and an ink pen. It looks and acts exactly like a seismograph. The system is reasonably short-ranged, and as such is used as a final fixing system before dropping a weapon. This system is used in conjunction with a smoke marker dropped from the rear of the aircraft.
When the target’s position course and speed have been developed, the crew will begin to fly in a race-track patter over the contact, called MAD-trapping. Every time the plane passes over the contact, the Sensor-3, when he sees the needle swinging will call out “MADMAN!” to the TACCO. A smoke marker will be dropped (it is launched straight back, at a speed matching the A/C airspeed, in order for the marker to drop straight down), and after a few such passes, the pilots can see the path of the submarine by the smoke markers floating in the water and can align their flight pattern to be more accurate.
One the fix is in, as it were, the TACCO will clear for weapon release, the bomb bay doors will swing open, and when the Sensor-3 calls out “MADMAN!” the weapon will be dropped. This is usually a M-46 Torpedo, but there are a variety of expendable stores available, which I’ll get to in another post.
Other systems operated by the Sensor-3 are the LLTV and the FLIR system, both of which are primarily used for surface search and identification. The P-3 is an all-weather aircraft and can patrol in almost any condition, day or night. Thus, the LLTV and FLIR allows the crew to see at night, and record it to video or digital medium for later analysis. This system has been used, along with others, to allow the P-3 to provide both recon as well as supply (and other) convoy support in the Middle East while remaining above most AAA weapons, and it’s long loiter time makes it an ideal support platform for these duties.
The two images below are both Official USN photos. The top one shows the SS-3 position in the P-3a/b models, and the bottom one shows the SS-3 Position in the P-3C and later variants.