How We Hunted Submarines

About the Diesel-Electric Submarines

My name is Lawrence F. Rodrigues. My friends call me Larry now, but when I was flying in the Navy airships I was called "Rod". After Navy "Boot Camp" my next 2 years in the Navy were spent in the excellent Navy schools at the Navy Aviation School (Norman, OK), and Electronics "A" school (Memphis, TN). I was top man academically in my "A" School class so I had 1st choice of 100 duty assignments worldwide. I picked Airship Squadron 3 at Lakehurst Naval Air Station, New Jersey

This was me about 1953. The "Cold War" was going on then and the U.S. Navy submarine service had just completed upgrading their subs using a lot of German WWII submarine technologies and concepts. These newest subs were called Guppy type. (GUPPY: "Greater Underwater Propulsive Power")

Deck guns were removed, the outer hull was streamlined, the conning tower replaced by a sail, propellers were redesigned, more air conditioning added, and the battery capacity was doubled.

Most significantly a snorkel was added to enable the diesel engines to take in air while operating at periscope depth, thereby reducing the radar target area to only the periscope, exhaust pipe, and snorkel air intake.

These innovations allowed underwater speeds to exceed surface speeds. Submarine commanders normally used the diesel engines with the snorkel to make their attack on a ship quickly then after the attack they would switch to battery powered electric motors to escape quiet and deep.

At the same time the Navy anti-submarine forces were infused with many new weapons to hunt and kill the latest "enemy" diesel-electric "guppy" type subs. One of the U.S. Navy's new anti-submarine weapons was the ZPG-2N airship made by Goodyear Aircraft Corporation. It was the end design containing all the latest electronic equipments and airship best innovations learned from earlier blimps.

AIRSHIP LENGTH: 343 feet long (104.57 m)

TOTAL HELIUM: 975,000 cubic feet

CAR LENGTH: Approximately 80 feet

POWER PLANT: Two 800 horsepower gasoline radial air-cooled Wright R-1300 engines inside the car.

MAXIMUM SPEED: 80 mph (128 km/h)

Our Mission: Train and Learn to Use Full Capabilities of the ZPG-2N for Anti-submarine Warfare

The training and practice exercises each lasted several hours as the submarine used different tactics simulating attacking the ships starting from approximately 20 miles away. Our mission was to use our electronics equipment to search for and find the submarine, then use various tactics to stop the sub attack with different simulated weapons such as a rubber nosed torpedo or small explosive depth charges.

Our Electronic Equipment

At "Zero hour" (start of the exercise) the sub would submerge to periscope depth and speed in some direction using the diesel engines and the air-intake snorkel sticking a few feet out of the water. The snorkel was a very small radar target 15 to 20 miles away! It was extremely difficult to pick out the snorkel target in the rough seas where the waves also made radar targets appear. The trick was to watch for a target that appeared consistently in nearly the same place, since wave targets were scattered randomly on the scope.

We flew a few miles behind or ahead of the ships so their targets were easily visible out of the "sea clutter" radar echos bouncing up from directly below us.

When we detected the sub snorkel or periscope on the radar, it was reported to our Combat Information Center (CIC) officer and the plotter. In those days our high tech plotting board consisted of a round horizontal Plexiglas covered table with a light underneath, and tracing paper on the Plexiglas. The table was set up like the radar scope with range marks on the Plexiglas that showed through the paper. By marking time and position of sub and ships on the paper, a record of the exercise was maintained and kept for later review. With this crude setup at least we never had to stop the "war" because the "computer was down". Once, though, I had to make an emergency light bulb replacement just before the exercise started. What a panic! My years of electronics schooling was paying off! I changed the light bulb in record time. ;-)

When the sub's snorkel or periscope was identified on the radar scope, we headed for the sub at top speed - about 65 knots. That is about 75 mph or 120 kmh. When the sub detected us approaching, the sub would shut down the diesel engines, dive well below the surface, and operate on battery motors. Of course the sub would take evasive maneuvers below the surface and we would not know exactly where it was headed, but we had a good idea within a half mile or so, if we went there fast.

After we arrived in the general area of the sub's last sighting, we dropped a circle of sonobuoys in the water where we thought the sub might be. The sonobuoys were about 3-foot long by 6 inches in diameter, and floated upright in the water. When they hit the water, an antenna popped up (it was like a steel tape measure), a hydrophone (an underwater microphone) dropped down on a cable, and the saltwater batteries activated a radio transmitter. We could tune a special sonobuoy FM receiver to each sonobuoy frequency and hear the underwater sounds from the hydrophone. Usually one or more of the hydrophones could pickup the sounds of the sub's screws. Using the known location of the loudest sonobuoys, we could determine the sub's approximate location. If needed, we dropped more sonobuoys to get a better "fix" on the sub. This required the pilot to fly low and make very tight turns. It was scary but exciting as we raced against time.

When we detected a magnetic signal from the sub on our MAD equipment, we dropped a bright yellow dye marker and white smoke-float on the water. We made a few more high speed, low altitude, tight turns and passes over the sub, and tried to get three good MAD contacts. On the third positive MAD contact we dropped a homing torpedo or depth charge. Of course they were nondestructive types. If we were close enough for a real "kill", the sub would release a big bubble of air. We usually were successful in intercepting the GUPPY type submarines before they targeted a ship in the task force and were very proud of our team efforts.

Here is what the MAD chart recorder would show when we made a pass over a sub. The magnetic anomaly detection equipment was originally designed for geological studies, finding mineral deposits, and locating oil fields. It also worked very well for pinpointing the location of a submarine. On this recording the small needle swings are noise and the big needle swing is a definite change in the Earth's magnetic field caused by the mass of the metal submarine. Airships were an excellent platform for carrying the MAD equipment because there was very little metal close to the magnetic detector out on the bow (front) of the airship. One time I was just messing around with the MAD gear as we were flying low across the New Jersey pines and I noticed a pretty good size signal. I thought at first that I had found oil in New Jersey! When I looked out the window to see what it was, it turned out that I had picked up railroad tracks and a train.
We practiced variations of this hunt and kill scenario for days at a time. Our missions were 30 to 40 hours long usually. Each crew member would be on duty 4 hours and then off for 4 hours. Sometimes I got really burned out but the excitement kept me going. Sometimes our airship crew operated as a pure combat information center (CIC) to direct the operations. Then we would radio the aircraft carrier to launch some aircraft and we would use our radar to guide them to where we thought the submarine was running submerged. The aircraft would drop the sonobuoys and use MAD gear, but they could not do nearly as well as a blimp. Sometimes blimps worked in pairs, with one operating as the CIC and the other blimp intercepting the sub and making the "kill". That worked better than using the aircraft from the carrier. The most fun was when our single airship and crew would do both the search and the "kill". Airships really are a better platform for that type work. Our unofficial motto was, "We fly low and slow!" With all things considered, our airships and crews were the best weapon against the diesel/battery subs of that time.

This picture is of me at the radar scope. In the air I was both the electronics equipment operator and maintenance technician. Years later after I was in the Air Force I only did the maintenance work and "operators" did the long hours of searching. Everyone is a "specialist" in the Air Force! In the Navy I worked my butt off but I got a lot of satisfaction out of making a significant difference in the end results of our operations. I worked on that radar so often that I had major parts of the schematic memorized. It had a million watts of peak power and was the best airborne radar available at that time. However, often it was either arcing and sparking where it shouldn't be or it was completely dead from a massive burn out. Because of all that power concentrated in a small area, heat and arcing were a constant problem. Some components had to be changed about every 12 to 24 hours from burnout. Most of the radar equipment was under the deck. I spent a large part of my flying time down in the airship bilges working on --and cursing-- that contrary radar. However, it was a most exciting adventure for a young guy like me then!

© 2007 Larry Rodrigues. All rights reserved.