"What? Do you know the answer?"

After hearing this, Cunning's eyes lit up immediately.

At the same time, Okinlek, Ritchie, Patton, Stilwell and others also looked at Yang Fan in one go, their eyes full of curiosity and curiosity.

As Yang Fan said just now, this problem has troubled them for a long time.

If a German submarine wants to enter and exit the Mediterranean from the Atlantic Ocean, it must pass through the Strait of Gibraltar.

The Strait of Gibraltar is the dividing line between Europe and Africa, and is the throat of the Mediterranean. It is about 58 kilometers long. The narrowest point is between Cape Marocio in Spain and Cape Cires in Morocco, with a width of only 14 kilometers.

Currently, both sides of the Strait of Gibraltar are under the control of the Allied Forces, and lightning monitoring stations are arranged.

Logically speaking, in such a narrow strait, as long as the Allies defended here, German submarines would have no chance to enter and exit the Mediterranean.

But in fact, the German submarine force was as if he was in a no-man's land, and could always easily avoid radar monitoring of the British and French Allied forces in the Strait of Gibraltar, and quietly entered and exited the Mediterranean many times, making the British and French navy dizzy.

They simply couldn't figure out where the German submarine came from and where they hid?

"In fact, the answer is very simple. The important factor that helps German submarines enter and exit the Strait of Gibraltar without being discovered is the currents that exist in the strait."

Facing the curious eyes of everyone, Yang Fan talked freely and began to popularize common sense of marine science to everyone.

The Mediterranean Sea east of the Strait of Gibraltar is a land sea with a closed surrounding land. The climate belongs to the Mediterranean climate. It is hot and dry in summer and the sea water evaporates vigorously. Therefore, the salinity of the sea water in the Mediterranean Sea is higher than that of the Atlantic Ocean west of the Strait of Gibraltar, and the natural sea level is lower.

On the contrary, the Atlantic Ocean is wide, with large rainfall and small evaporation, so the sea water has a lower salt content and a smaller density, so the natural sea level is high.

Therefore, two uneven ocean surfaces formed near the Strait of Gibraltar. The sea water at the bottom of the strait flows westward from the Mediterranean side with a denser density to the Atlantic Ocean, and the upper sea water will flow from the Atlantic Ocean to the Mediterranean.

The Germans took advantage of this seawater flow pattern. When entering and leaving the Mediterranean, the submarine shuts down the engine and drops to a deeper area below the sea surface, and flows out of the Mediterranean to the Atlantic Ocean along the ocean current.

When he came back, he raised the submarine to a shallower area, turned off the engine, and followed the surface currents and then returned to the Mediterranean.

The submarine cannot be discovered by sonar without engine noise, and the submarine does not surface to sail or sail in a snorkel state, so it can avoid the sight and radar reconnaissance of the British and French Allied forces.

"What? That's OK!"

"Oh my God, these German guys are so cunning!"

"No wonder we can't monitor these damn German submarines, so that's how it is!"

"General Yang Fan is indeed powerful. You can get such information!"

"Yes, it's not simple. This problem has been bothering me for so long, and now I finally figured it out."

After listening to Yang Fan's commentary, Cunningham, O'Ginleak, Ritchie, Patton and others were all enlightened, with wonderful expressions, and they kept nodding and admiring Yang Fan.

"That's right, there's nothing in this world that our chief executive can't handle!"

"You should be convinced now."

Lu Shengfeng, Meng Wuan and others were smiling, full of pride and joy.

After a while, Cunningham started to make noise again and asked Yang Fan loudly: "I admit that this discovery has solved a mystery that has troubled us for a long time, but what specific effect does this have?

Even if we know that German submarines enter and exit the Mediterranean in this way, what can we do with them? We are still helpless!"

Cunningham is not simply arguing with Yang Fan, but he is indeed pointing out the current anti-submarine problem.

In addition to visual inspection, the current anti-submarine methods mainly include two methods: sonar anti-submarine and radar anti-submarine.

Sonar and radar are two completely different reconnaissance equipment.

Sonar is a water reconnaissance equipment that has both active and passive functions. It can accurately locate the short-distance submarine distance. Under good sea conditions, submarines of about 1.5 kilometers can be monitored.

For the Allied large rapid transport fleets, the main form of transportation in the Atlantic, it is basically meaningless to use sonar to search submarines, because of the fast speed, too loud noise, and the current sonar technology level is not good and the action distance is limited, so it is impossible to effectively search submarines.

Therefore, currently sonar is mainly used to attack submarines rather than search submarines. The main thing that restricts submarines is radar, not sonar.

The radar is a reconnaissance of air to sea above the sea surface, with a relatively long distance.

The conventional powered submarines in the world are not equipped with an AIP system (i.e., air-free propulsion system). They use diesel engines to power the battery while sailing on the water surface and charge the battery at the same time; they use batteries to power the battery when sailing underwater.

Therefore, the submarine must often surface for charging, and the radar can detect the snorkel exposed to the water when the battery is charged regularly.

The main method of the Allied forces to use long-range patrol aircraft to repeatedly patrol, use visual and radar search methods to search for submarines sailing on the water surface or snorkel states, and then attack after discovering them.

Usually, submarines do not surface during the day, so most of the time it is only useful at night radar. It is enough to use patrol aircraft and visual reconnaissance during the day.

However, the reduction in wavelength also shortens the radar's action distance, and the part of the submarine exposed to the water surface is very small.

The 286 sea search radar currently used by the British Navy, the effective detection distance of U-boats in water surface state is only 3-5 kilometers depending on the sea conditions.

It will also be completely unaware of the Metox alarm receiver on the German U-boat used to listen to the meter-pole radar. Therefore, even if the German submarine surfaces to charge, the anti-submarine efficiency will be very low.

In addition, there is also an auxiliary anti-submarine method, which is the radio detection of destroyers and frigates.

Everyone knows that the main function of destroyers and frigates is to escort the transport ship, block the submarine when it attacks, reduce fleet losses, and destroy the attacking submarines as much as possible.

In fact, they also have a very important role in radio detection.

Because the wolf pack tactics require frequent use of radio to contact other submarines, inform the target location, and then wait for other submarines to arrive before launching a cluster attack.

This radio communication process can be detected and listened to. Once the escort ship discovers frequent radio communications at close range, it can confirm that a U-boat has discovered itself and can actively search or summon the plane to search.
Chapter completed!