This article is the 688th original article of the "Burning Island Group", author: The Group Lord Flying Dragon.
The full text is 4942 words, with 12 pictures, it takes 14 minutes to read, and it was first published on December 17, 2021.
In November 1914, the German Navy and naval aviation established submarine bases and aviation bases in the Belgian port of Zeebrugge, respectively, and the aviation was tasked with exploring the use of FF.29a seaplanes loaded with 12 kg bombs to attack enemy surface ships. Due to the limited range of the aircraft, the initial attempts failed.
At this time, the captain of the "U-12" submarine stationed here, Voert. Walter Forstmann came up with a simple but novel idea of using submarines to load aircraft and launch attacks in the waters as close to the target as possible.
Figure 1. German submarines carrying FF.29a biplane seaplanes, at this time the submarine can only carry the aircraft simply, can not provide a take-off and landing platform
On 6 January 1915, a German submarine carrying an FF.29a aircraft left the dock and dropped it into the sea less than 15 miles off the coast of Britain. After taking off from the sea, the aircraft crashed directly into the naval port in Kent, England, and the raid was a success, and both the submarine and the aircraft returned safely to the port of Zeebrugge. In this regard, the Germans took the lead in creating the concept of "diving aircraft carrier" and put it into practice, integrating various military science and technology and strategic and tactical innovations, germans are the real "fighting nation".
Due to tonnage restrictions, the aircraft on submarines are mainly used to perform special operations missions and aerial reconnaissance. Beginning in 1916, Britain, Germany, the United States, Italy and France successively carried out research and experiments on aircraft submarines, and the Germans designed a variety of seaplanes for submarines, and had many sorties recorded in World War I.
In 1919, Dr. Ernst Heinkel, who had worked at the Hansa Brandenburg Aircraft Plant, moved to the Casper Aircraft Factory in Trafford, where he designed the Casper "U-1" and "U-2", which could be disassembled and loaded into a barrel container about 7 meters long and 1.8 meters in diameter. The aircraft is made of wooden splints and is compact. When disassembling, first use the small boom on the deck to lift the aircraft, remove the pontoon, open a small hatch at the tail, pull the inside handle, and the locking device of the wing will be detached; The wings and pontoons are then placed on the cart against the fuselage and slid into the container to seal the lid tightly, without any tools.
Figure 2. Specially designed for the U-1 aircraft to be carried on submarines, the following is the dismantled state, which is convenient for loading and transporting in the submarine
The "U-1" uses Siemens' star Halske Sh 4 engine, which is 62 hp and produces three in total; The U-2 was powered by an 80 hp Oberursel U0 engine, but was never produced. Karl Casper, the factory owner at the time, was a naval pilot in World War I, so both models were named after him.
It is worth mentioning that the engine's rocking crank is located in the cockpit, and the driver can start it himself without climbing to the shaky pontoon to pull the propeller. However, in the process of testing and use, it was found that the on-board aircraft had to be deployed on the surface of the water, losing the maximum characteristics of the submarine's concealment and being greatly affected by sea conditions. After the end of World War I, Germany was in ruins, and the army greatly reduced its personnel and military expenditure, and even had difficulties in maintaining its original size and equipment, let alone being unable to equip new equipment. As a result, the German military showed no interest, and of the three U-1 aircraft produced, two were sold to the U.S. Navy and one to the Japanese Navy. I have to say that this is the sadness of the weakening of the country's national strength.
The Japanese, who were very concerned about german military power and attached importance to copycats, did not let go of the new thing of submarine carriers. Although the Japanese took part in the Allies' side during World War I, after the war, the plundered German military technology was copied and imitated immediately.
In the fourteenth year of Taisho (1926), through the purchase of the "U-1" type of boat-based aircraft, the Japanese copied their own original shipboard "Yokosho 1-Go" water reconnaissance aircraft (Yokosho 1-Go), which made its first flight in 1927, and then carried out a 18-month test on the I-21 (completed in March 1927), a submersible submarine also imitated from Germany, which was an early practice of the Japanese Navy's concept of "submersible aircraft carrier".
Figure 3. The Japanese imitation of the "Horizontal One" small boat submarine is a reconnaissance aircraft on the water, which can be seen to be very similar to the German prototype
Further improvements were followed by the development of the Yokosho 2-Go. The wooden testing machine, made to its actual size, was carried by the Haidai-1 submarine "I-51" (completed in June 1924) and tested.
In 1929, the I-51 took part in fleet exercises for the first time with a small reconnaissance aircraft on the water. In the same year, the fleet mentioned in a report to the base camp: "Submarines enter enemy-controlled waters to carry out surveillance tasks, risk great dangers, and must be supported by shore-based aviation." However, shore-based aircraft have a small combat radius and are difficult to complete. Even if the submarine ventures into the submarine, it is difficult to complete the surveillance task with the periscope alone. Therefore, there is no other way but to use submarines to carry reconnaissance aircraft. ”
At this point, several major patterns of using submarines for surveillance, tracking, and maintaining contact have been formed, and since the Navy's bigwigs generally believe that this trick works, the continuous optimization and improvement of the carrier aircraft is on the agenda. In January 1932, the "Type 91" small water reconnaissance aircraft was officially adopted by the Navy, and in 1934, the "Type 96" small two-seat biplane water reconnaissance aircraft was successfully developed, which was equipped on the "I-7" and "I-8" and participated in the actual combat of the War of Aggression against China and the Pacific War.
On the issue of the use of submarine-borne aircraft, although there are many risks, in the Toei Navy, which does not attach much importance to human life, the majority of people's opinions are considered applicable, especially after the 1939 naval exercise, it is believed that "the carrier aircraft can take off from the sea in a timely manner, or use the island shore to take off covertly, and use it skillfully to make up for the lack of submarine surveillance capabilities." Moreover, the on-board aircraft should make the best use of the moon and night activities. ”
Through the 1941 long-distance special operation, the following experience was gained: "It is extremely difficult to carry out covert surveillance activities with submarines alone, and it is difficult to successfully complete the task, so it is necessary to make extensive use of on-board aircraft to improve surveillance capabilities." Since then, the Japanese Navy has determined the use of submarines carrying submarine-borne aircraft to carry out long-distance reconnaissance, especially aviation reconnaissance. This conclusion cushioned the Japanese Navy's unique use strategy and military building ideas for carrier aircraft during World War II.
However, because onboard aircraft may take off and land in turbulent oceans, and the take-off and landing platform is a submarine with small displacement and sharp swing, the risks during take-off and landing are high. In the vast ocean, whether the two-seat Zero small water detection can successfully find the location of the submarine and be successfully recovered by the submarine is also a headache. For any pilot, it is very likely that the submarine will take off and land without going back.
Figure 4. The Ar231 small submarine of the German Navy Submarine Force is a reconnaissance aircraft on water, and the bottom picture is the folded state
It is precisely because of the high danger of shipboard aircraft that the naval powers of Europe and the United States have successively terminated similar research programs. It was not until the beginning of World War II that the German Navy began to consider the possibility of submarine reconnaissance aircraft again. In 1940, the Arado Aircraft Factory received a contract to produce six "U-Bootsaugens", which literally translate to "Eye of the Submarine". The aircraft was the single-wing, single-seat reconnaissance aircraft Ar231, which used an air-cooled six-cylinder in-line Hess HN501 engine with a power of 160 horsepower.
The Ar231's wing folding method is more special, you can stack one side of the wing on the other side of the wing, and then close above the fuselage, the diameter of the hangar is also controlled at about 1.8 meters. After the test flight, it was found that when the surface wind speed was greater than 20 knots, the Ar231 could not take off safely. In addition, the Germans never tried to use catapults to take off a carrier-based aircraft.
Figure 5. In 1928, the British conducted a carrier test on the M-class submarine Ii, but then abandoned it
The Japanese were most fascinated by the carrier aircraft. In January 1934, in response to the demand for the newly built Cruise-3 large ocean-going submarine, the Japanese Navy proposed to design a two-seat small seaplane, which was eventually undertaken by Watanabe Steel, and in February 1935, the first prototypes were test-flown. Watanabe's scheme meets the requirements of the Navy: single-engine, two-seat, double-float, biplane, can be folded into the submarine's narrow hangar, can be assembled into a flight state within 2 minutes and 30 seconds, and folded into a storage state within 1 minute and 30 seconds. The airborne armament consisted of only a 7.7 mm rear-facing aircraft gun, operated by a resembrander observer, and acting only to embolden himself. After the prototype was successfully tested by the I-5 submarine, the Japanese Navy placed an order for 32 aircraft.
Figure 5. A small biplane submarine designed and produced by Watanabe Steel is a reconnaissance aircraft on water
In 1938, the mass production aircraft was given the official name of the "Navy Type 96 Small Water Reconnaissance Aircraft" (Watanabe E9W1), and production continued until 1940. Embarrassingly, at the same time that the "Type 96 Small Water Detective" was produced and put into service, his competitor, a small water reconnaissance aircraft with single-engine two-seater and double pontoons developed by the Air Technology Factory, was also introduced. Therefore, the two submarines are in service with small water detection in the Navy's submarine force almost at the same time.
The reason why the production of type 96 small water detection is very low is obviously affected by the fact that the biplanes of that era are rapidly being replaced by monoplanes, and similar situations also appear in the navy's ship warfare (biplane ninety-five ships to single-wing ninety-six ship battles), ship attack (biplane ninety-two ships attack to single-wing ninety-seven ship attack), ship explosion (biplane ninety-five ships explode to single-wing ninety-nine ship explosion), ship detection (biplane ninety-five water detection single-wing zero-type water detection) and other models.
However, the Type 96 Small Water Reconnaissance was still in service in the front-line forces until July 1942. From 1938 to 1942, the Type 96 small water detective participated in the operations of Japanese submarines in Southern China in the early days of the invasion of China, as well as the aerial reconnaissance of Pearl Harbor by Japanese submarines. In 1942, the Allies gave the small biplane reconnaissance aircraft a more apt nickname "Slim" (meaning "Skinny").
Figure 6. Type 96 small water reconnaissance aircraft, two-seat double-float design, the size of the aircraft has been significantly larger than the German counterpart
At the end of 1936, according to the "03 Ship Supplementary Plan", the Japanese Navy began to build type A and type B ocean-going submarines, both of which were large submarines of 3,000 tons and could carry one onboard aircraft. At this time, the Japanese Navy was no longer satisfied with the Type 96 small water detection, they needed more advanced boat-borne seaplanes. Design requirements for the new carrier aircraft were issued in 1937 to three developers — the Naval Aviation Technology Factory (Kugisho), yokoshi and Watanabe — both of which had a bit of a base on the carrier aircraft.
In 1939, the Air Technology Factory and watanabe Iron Works came up with their own prototypes, and after military comparisons, the Air Technology Plant's plan won, and poor Watanabe Did not get any decent orders throughout World War II, but after the company changed its name to Kyushu, it came up with a refreshing "shock" local fighter program.
Figure 7. In 1939, the E14Y1, a small one-winged small water reconnaissance aircraft of the air technology plant in the test flight, was still a semi-enclosed cockpit at this time, and it is worth mentioning that the vertical tail of the aircraft adopted an elongated and low-height design, also for convenient storage
The air technology plant solution is a single-engine twin-float, power system is a 340 hp Hitachi nine-cylinder star-cooled engine, wooden two-blade constant pitch propeller. The fuselage is a power frame made of metal tubes, the fuselage is equipped with duralumin film, and the tail is equipped with thin sheets. The wing and tail components feature a hybrid structure and linen housing. Used to place in the submarine of the oval aviation hangar, the length of the whole aircraft is only 8.5 meters, the width is 2.4 meters, and the height is only 1.4 meters after folding. In the Gner state, the tail horizontal wing can also be folded downwards. The all-metal pontoon is also removed in the Gnar state and stored in the space under the fuselage.
Figure 8. In the Gner state stored in the submarine hangar, note that the wings are folded backwards, the horizontal tail is folded downwards, the pontoons are removed and stored in the space under the fuselage
Figure 9. The E14Y1 small water reconnaissance aircraft of the Air Technology Plant, noting that there were two 30 kg bombs under the wings
Figure 10. Model painted, a small zero-type water detection in blue-green livery, took off from the submarine patrol submarine Type B "I-29" and flew around the boat. There are two bomb pylons under the wings of the Zero small water detection, and by reducing the amount of fuel carried, dismantling self-defense weapons, and in extreme cases of reducing the number of passengers, two 76 kg bombs can also be loaded, which is equivalent to leaving a 90 kg load to the bomb
Compared with the open cockpit's Type 96 small water detection, the air technology plant's scheme initially adopted a semi-enclosed glass cockpit design. The cabin could accommodate two people – a pilot in the front seat and an observer and machine gunner in the rear seat. In order to communicate with the submarine, the observer position is equipped with a radio station and a Type 92 7.7 mm aircraft machine gun for self-defense.
In terms of weapons, two bomb pylons were designed under the wings, and the standard mount was two 30 kg bombs. In extreme cases, by reducing fuel stocks, dismantling machine guns, and even reducing resembrander observers, two 76-kilogram bombs could be mounted when carrying only one pilot.
At the time of the test flight, the maximum flight speed of the prototype of the air technology plant reached 239 kilometers per hour, but the cruising speed at an altitude of 1000 meters was only 157 kilometers per hour, and the prototype also had the problem of overweight and the range could not reach the design indicators. In addition, during the flight, unsatisfactory travel stability emerged.
In the production version, the fuel capacity was increased to 340 liters, the fuselage was also improved, stability was submitted, and the glass cockpit was changed to a fully enclosed one to reduce wind resistance. The maximum speed of horizontal flight is increased to 246 km/h and can cruise at a speed of 167 km/h. The normal flight distance has been increased to 822 km, the maximum range is 1074 km, and the practical ceiling is 5420 m.
Figure 11. In 1940, the first batch of mass production of air technology plant small water detection E14Y1
Figure 12. The 1941 Zero Mini-Water Detective, with the number on the tail indicating that it belonged to the I-7 submarine
- To be continued, stay tuned! -