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Aichi AB-2 Experimental Catapult-Launched Reconnaissance Seaplane

Aichi AB-2 Experimental Catapult-Launched Reconnaissance Seaplane

Aichi AB-2 Experimental Catapult-Launched Reconnaissance Seaplane

The Aichi AB-2 Experimental Catapult-Launched Reconnaissance Seaplane was the first aircraft of its type to have been designed in Japan without any foreign assistance, but the aircraft wasn't a success and only two prototypes were built.

The Japanese aircraft industry had been founded with help from a variety of European companies - many early Aichi designs were produced by Heinkel, or based on Heinkel designs and other Japanese companies also established overseas links. This had been the case for the Aichi Type 90-1 Reconnaissance Seaplane (E3A1), which had been designed by Heinkel as the HD 56. Work on that design began in 1928, and the aircraft was accepted for production in 1931.

In 1929 Aichi began work on their own design for a reconnaissance seaplane, working without any assistance from Heinkel. The design team, led by Tetsuo Miki, produced a twin-float biplane, with a welded steel tube fuselage and wooden wings, both of which were fabric covered. The wings folded backwards.

The AB-2 was powered by a new Aichi AC-1 nine cylinder air-cooled radial engine. As was so often the case the choice of an experimental engine turned out to be a mistake. The AC-1 failed to produce as much power as expected, reducing the performance of the AB-2. The basic design also needed modifying, hardy surprising in such an ambitious project. The project came to an end soon after a fire destroyed one of the two prototypes. However the effort wasn't wasted, and many features from the AB-2 were used in the AB-3 experimental single-seat reconnaissance seaplane, which was designed for China.

Engine: Aichi AC-1 nine cylinder air-cooled radial engine
Power: 300-330hp
Crew: 2
Span: 36ft 1in
Length: 27ft 0.5in
Height: 11ft 3.5in
Empty weight: 2,458lb
Loaded weight: 3,648lb
Max speed: 112mph at sea level
Cruising speed: 81mph
Climb Rate: 20min to 9,843ft
Endurance: 5.9 hours
Armament: One fixed forward firing 7.7mm machine gun, one 7.7mm flexibly mounted dorsal machine gun
Bomb load: Two 66lb bombs

Design and development [ edit | edit source ]

In 1929, Tetsuo Miki, a designer at Aichi Tokei Denki Kabushiki Kaisha (Aichi Watch and Electrical Machinery Company) started the design of a catapult launched reconnaissance floatplane with the aim of replacing the Nakajima E2N aboard the Imperial Japanese Navy's warships. Miki's design was a small single-engined biplane. Its fuselage was of steel tube construction with fabric covering, while it had wooden wings that folded to the rear for storage aboard ship. Powerplant was a 330 hp (246 kW) Aichi AC-1, an experimental radial engine. The two-man crew sat in open cockpits, while the aircraft's undercarriage consisted of twin floats. Ώ]

The two prototypes were completed and flown in 1930. Ώ] The AC-1 engine was not successful, however, and the project was abandoned after one of the prototypes was destroyed when an exhaust fire spread to the fuselage. The type did form the basis of the later Aichi AB-3 floatplane, of which a single example was built in 1932 for China. Ώ]

Development and design [ edit | edit source ]

In 1928, the Republic of China Navy, keen to modernise its obsolete fleet, placed orders for a class of two light cruisers, the Ning Hai class, to be designed in Japan, with the lead ship to be built at the Harima shipyard in Japan, and the second ship, with Japanese help, in China. The ships were designed to carry two small seaplanes each, with a small hangar being provided for a folded aircraft, and the Japanese Navy placed an order with Aichi for a single seat floatplane to equip these ships. Ώ] ΐ]

Aichi's designer, Tetsuo Miki based his design on his Aichi AB-2 two seat floatplane which was under design for the Imperial Japanese Navy, producing a small single-seat biplane of mixed wood and metal construction with single-bay wings, powered by a 130 hp (97 kW) Gasuden Jimpu radial engine. It had twin floats, and had detachable wings to aid storage aboard ship. Α] The prototype AB-3 was completed in January 1932, and when flown for the first time in February that year proved to have excellent performance, exceeding the specification in all ways. ΐ]


In 1929, Tetsuo Miki, a designer at Aichi Tokei Denki Kabushiki Kaisha (Aichi Watch and Electrical Machinery Company) started the design of a catapult launched reconnaissance floatplane with the aim of replacing the Nakajima E2N aboard the Imperial Japanese Navy's warships. Miki's design was a small single-engined biplane. Its fuselage was of steel tube construction with fabric covering, while it had wooden wings that folded to the rear for storage aboard ship. Powerplant was a 330 hp (246 kW) Aichi AC-1, an experimental radial engine. The two-man crew sat in open cockpits, while the aircraft's undercarriage consisted of twin floats. Ώ]

The two prototypes were completed and flown in 1930. Ώ] The AC-1 engine was not successful, however, and the project was abandoned after one of the prototypes was destroyed when an exhaust fire spread to the fuselage. The type did form the basis of the later Aichi AB-3 floatplane, of which a single example was built in 1932 for China. Ώ]


In 1931, the Imperial Japanese Navy instructed the Aichi Tokei Denki Seizo KK. (Aichi Watch and Electric Machinery Company, Ltd), who had been involved in aircraft manufacture, particularly for the Navy, since 1920, to design a small catapult-launched night reconnaissance aircraft, intended to observe nocturnal shipping movements, spot naval gunfire during night engagements and to direct friendly submarines. Ώ] The resulting design, designated AB-4 ("Aichi Biplane") by Aichi was a single-engined pusher biplane flying boat of all-metal construction. Its single-bay wings folded backwards for storage aboard ship, while its crew of three were housed in open cockpits. It was powered by a single Gasuden Urakaze water-cooled six-cylinder inline engine driving a two blade propellor. ΐ]

The first prototype flew in May 1932, and while handling was generally good, it had poor control during take-off and landing, and a poor view for the pilot. Despite this, a further five prototypes were ordered for evaluation. ΐ]

Japan’s Floatplane Dive Bomber

The vast open seas and multitude of small islands over which World War II was fought in the Pacific Ocean made both sides unwilling to rely exclusively on land-based or even carrier-based aircraft. Consequently, the Pacific War saw the last widespread use of floatplanes and flying boats, which could operate from lagoons and sheltered bays where airfields might not be within easy reach.

Of all the combatants, Japan made the most imaginative use of its waterborne air assets. Its Kawanishi H8K2 (code -named “Emily” by the Allies) was among the best flying boats of the war. The fast, long-range Aichi E13A1 (“Jake”) became a scouting mainstay for the Imperial fleet. The shorter-range Mitsubishi F1M2 (“Pete”) two-seat biplane was sometimes flown as aggressively as a fighter. The Japanese even produced a floatplane version of Mitsubishi’s famed Zero fighter, the Nakajima A6M2-N (“Rufe”), as well as a floatplane fighter built from scratch, the Kawanishi N1K1 (“Rex”). The Yokosuka E14Y1 (“Glen”) could be flown from submarines, and at the end of the war a submarine-launched floatplane bomber, the unique Aichi M6A1 Seiran, was slated to attack the Panama Canal.

With so many specialized roles assigned to an aircraft type that most other countries used only for reconnaissance and bombing targets of opportunity, it’s not surprising the Japanese developed a floatplane dive bomber. And it should also come as no surprise that Aichi, designer of the superb E13A1 floatplane and D3A1 “Val” carrier-based dive bomber, was responsible for its development.

The E13A1 had barely been accepted for production in 1940 when Aichi’s design team began work on a successor that October, under the company designation AM-22. As with its predecessor, this would be a twin-float monoplane, but sturdier, more powerful, faster and longer ranged. The E13A1’s puny defensive armament of one rear-mounted 7.7mm machine gun would be increased, with two 7.7mm Type 97 machine guns in the wings and a 7.7mm Type 92 weapon for the observer. With a view to the more aggressive role envisioned for the AM-22, hydraulically operated dive brakes were installed in the front float support struts, making it capable of dive bombing.

This captured Aichi E16A1, shows the ingenious folding dive brakes mounted on the forward struts that attach the aircraft to its floats. (U.S. Navy)

The Japanese navy, reflecting its satisfaction with the E13A1, drew up a new specification based on Aichi’s design early in 1941. Work proceeded apace, and in May 1942 the first of three prototypes made its maiden test flight. At that point, the AM-22 hit its first snag when its test pilot reported instability in flight and buffeting from the dive brakes. It took the Aichi team 15 months of redesigning to resolve those problems, but in August 1943 the navy finally accepted the plane for production as the E16A1 reconnaissance seaplane Model 11, nicknamed Zuiun, or “auspicious cloud.” The Allies code-named it “Paul.”

The E16A1 was all metal, save for the tail-plane and wingtips, which were made of wood, and fabric-covered control surfaces. In addition to the strut-mounted dive brakes— which were solid on early aircraft but perforated with multiple holes or quintuple slots in later models—the wings had conventional Fowler-type trailing-edge flaps and could be folded for shipboard storage. Each of the single-step floats featured a rudder.

The prototypes and early production Zuiuns were powered by a Mitsubishi MK8A Kinsei 51 14-cylinder, twin-row radial air-cooled engine, with a takeoff rating of 1,300 hp, driving a three-bladed, constant-speed metal propeller. The MH8D Kinsei 54 powered later production aircraft.

The E16A1’s secondary dive bomber role inspired Aichi to significantly upgrade the armament on production aircraft to two wing-mounted 20mm Type 99 cannons and a 13mm Type 2 machine gun for the observer. It could carry up to 250 kilograms (551 pounds) of bombs or depth charges under the wings. In spite of its improved ordnance and overall superior performance to that of the E13A1, veteran crews complained that the E16A1 was harder to fly and more fatiguing to handle than its predecessor, which they still preferred.

Aichi built 193 E16A1s at its Eitoku factory between January 1944 and August 1945, and an additional 59 were built by Nipon Hikoki K.K. at Tomioka from August 1944 to the end of the war. That grand total of 256 E16As (counting the three prototypes and a single experimental E16A2, powered by a 1,560-hp MK8P Kinsei 62 engine), compared with the 1,418 E13A1s built, showed how priorities for Japan’s increasingly beleaguered air industry were changing as the war turned against it.

Among the first units allotted E16A1s were the Yokosuka and 634th Kokutais (air groups). Formed on May 1, 1944, and commanded by Captain Takahisa Amagai, the 634th was attached to the Third Air Fleet and had a total of 130 aircraft, of which 24 were E16A1s. By then, however, the floatplane’s shipboard use had become as problematic as its dive brakes.

In an attempt to make up for the six aircraft carriers they had lost in 1942, the Japanese supplemented the new ones they were building by converting two seaplane tenders into light carriers and, in an even more drastic move, installing flight decks on the sterns of the battleships Ise and Hyuga. The latter, sometimes called “hermaphrodite battleships,” were intended to carry Yokosuka D4Y2 Suisei land-based dive bombers (Allied code-name “Judy”) and E16A1 Zuiuns. Both plane types would be catapult-launched, and after they had carried out their missions, the Suisei crews would fly to the nearest island air base or ditch and be rescued by accompanying destroyers. The Zuiuns, on the other hand, could land on the water and be retrieved by the battleships’ cranes. At least that was the theory.

But the October 23-26, 1944, Battle of Leyte Gulf ended in a crushing defeat that cost the Japanese 24 major warships. Thereafter, the 634th Kokutai flew its E16A1s from Cavite in the Philippines.

One Zuiun crew that distinguished itself at that time consisted of pilot Heijiro Miyamoto and observer Hiroshi Nakajima. The latter was awarded a rare medal for distinguished service while carrying out night bombing attacks on American-occupied Tacloban airfield on November 22 and 23. When the Japanese cruisers Ashigara and Oyodo, three destroyers and three escort vessels made a hitand-run attack on the American beachhead at Mindoro on the night of December 26, Miyamoto shot down a Fifth Air Force night fighter over San José airfield and bombed four patrol torpedo boats, damaging PT-77. He followed that exploit by damaging a medium transport with a 250-kilogram bomb on the 30th. For the most part, though, the E16A1’s effectiveness was limited by the air superiority the Americans had established over Leyte, and attrition was high. On January 8, 1945, what remained of the 634th was withdrawn from the Philippines and reorganized as a float reconnaissance unit.

As the Allies closed in on the Home Islands, and especially after the Americans landed at Okinawa on April 1, 1945, a desperate Japan found a new use for its Zuiuns. In this role their dive brakes were irrelevant, since kamikaze pilots were not expected to pull out of their dives. Even with a 273-mph speed and 20mm cannon armament, however, the float-encumbered suicide planes had scant chance of reaching the U.S. Fifth Fleet if they encountered defending fighters or the wall of anti-aircraft fire thrown up by the ships themselves. The only ace known to include a Paul in his score, Lt. j.g. Robert J. Humphrey of the carrier Hornet’s VF-17, was flying a Grumman F6F-5N night fighter when he spotted and shot down the floatplane 20 miles northwest of Tokumo Shima at 7:45 p.m. on May 24.

Heijiro Miyamoto of the 634th Kokutai continued to distinguish himself over Okinawa, being cited for dropping two 60- kilogram bombs on a “battleship” on March 29 (more likely the assault transport Wyandot, which suffered minor damage), hitting a destroyer with a 250-kg bomb on April 20 and sinking a transport on May 20. No Allied loss matches the destroyer Miyamoto claimed to have sunk on May 30, but during the attack anti-aircraft fire badly wounded his observer, Nakajima. Miyamoto’s own luck finally ran out on June 26, when his E16A1 failed to return from a patrol in the Okinawa area.

When not being expended on futile suicide missions, Zuiuns of the Yokosuka Kokutai served in the training role. Few Pauls remained when Japan surrendered on September 2, 1945, and although some were evaluated by the victorious Allies, none are known to exist intact today. In spite of its hopeful name, the cloud under which the Zuiun flew was less than auspicious.

Originally published in the November 2008 issue of Aviation History. To subscribe, click here.

Submarine Reconnaissance Missions

One of the lesser known aspects of the air war in the Pacific is the extent to which the Japanese made use of submarine-launched aircraft. Although several navies had experimented with submarine aircraft carriers between the world wars, only the Imperial Japanese Navy seriously pursued the concept. The French Navy developed the large cruiser submarine Surcouf, whilst the British modified their submarine M2 to carry small seaplanes which could be partially disassembled and stored in waterproof hangars built into the vessel’s hull. Both of these experimental ships were one-offs and neither the French nor the British took the concept further. The German Kriegsmarine and the US Navy both examined the idea but never progressed to the point of deploying prototypes. The Japanese Navy meanwhile developed an extensive fleet of 42 large submarines which were capable of carrying aircraft.

The first of these was a modification of the Junsen Type submarine. The fifth vessel of this class, I-5, was the first Japanese submarine to be completed with storage for a single tiny E6Y floatplane, which could be partially disassembled. To launch, the plane was assembled on deck and floated off, before it took to the air under its own power. However, this method proved inadequate and I-5 was fitted with an air-power catapult. Follow on Junsen Type, Mod II and III submarines included this addition as part of their standard design as completed. This was very useful given the lack of engine power available to the tiny floatplanes carried aboard – the Yokosuka E6Y had just 160hp available at full power. I-5 entered service in 1932 and served as the test-bed for later aircraft-carrying submarines which were commissioned from 1935 onwards. Several of the Junsens supported the Japanese war in China from 1937 onwards, flying reconnaissance sorties in support of the blockade of that country.

The Junsen Types were followed by four Type A submarines, which were slightly larger and had better aircraft carrying capabilities. This allowed the Type As to carry the larger and more powerful Watanabe E9W, which greatly increased the capability of the submarine-aircraft tandem. The Type As were commissioned in the year leading up to the start of the Pacific War. It was immediately after the Pearl Harbor attack, on the 16 th of December, that the submarine I-7 launched her E9W to reconnoitre the damage done to the Pacific Fleet. The pilot reported seeing several damaged battleships, as well as a carrier, five cruisers and 30 other vessels. Upon return to the mother ship, the E9W was damaged and the crew had to swim to I-7, which then scuttled the plane and soon made good her escape.

The largest single class of submarine aircraft carriers were the Type Bs, 29 of which were completed with aviation facilities. These saw extensive service across the Pacific and were perhaps the most successful Japanese submarine design of the war. By the time they entered service they could take advantage of the latest model of small reconnaissance seaplane, the Yokosuka E14Y Type 0, which was slightly faster and longer-legged than the E9W whilst also being able to carry a modest bomb load. Many of the Type Bs were converted to act as motherships to midget submarines, in which role they participated in the attack on Pearl Harbor. I-19’s E14Y reconnoitred Pearl Harbor on the 4 th of January, 1942, and reported on the progress of repairs. I-9’s E9W then made a repeat visit on the 23 rd of February.

Perhaps the most famous, and certainly the most experienced, of the submarine aircraft carriers was the Type B I-25. She had been part of the Pearl Harbor attack force, and had been ordered to hunt for the American carriers that escaped destruction. Immediately afterwards she was ordered to the US coast, where she attacked a tanker during an otherwise fruitless patrol, before returning to Kwajalein. Here she replaced her E9W with an E14Y and survived a strafing by American aircraft during the raid of the 1 st of February.

On the 8 th of February, I-25 departed Kwajalein with orders to patrol and reconnoitre various locations in Australia and New Zealand. She arrived off Sydney on the 15 th , but rough weather delayed the launch and it wasn’t until the 17 th that pilot CPO Nobuo Fujita and observer PO2c Shoji Okuda could take off in their floatplane. They overflew the capital’s Botany Bay and counted a total of 23 ships in the harbour, before returning safely to the I-25. Nine days later, the same crew flew over Melbourne and attracted the attention of RAAF fighters and anti-aircraft crews, before again returning safely. A flight over Hobart followed on the 1 st of March, before I-25 headed for New Zealand. Wellington was scouted on the 8 th of March, and Auckland on the 13 th , before Fujita and Okuda attempted to find a cruiser and merchant ship that had been briefly spotted by lookouts. Finally, I-25 sailed to Fiji for a final overflight, before ending her patrol at Truk.

Sydney Harbour Midget Sub Attack

I-25’s patrol to Australian waters served as a prelude to an attack planned for late May. With the Japanese in the planning stages for Operation MI, the attack on Midway, two separate attacks by submarines were planned as distractions – one on the recently captured port of Diego Suarez on Madagascar, the other on Sydney Harbour. The 8 th Submarine Squadron was tasked with carrying out both of these widely separated locales. The Eastern Attack Unit consisted of I-21 and I-29 carrying E14Ys, and I-22, I-24, I-27 and I-28 with midget subs. I-24 suffered battery explosion and was scrubbed from the mission soon after leaving Kwajalein. First to arrive off Australia was I-29, which launched its E14Y on the 23 rd of May. This flight was detected by an RAAF radar unit, but dismissed as a glitch. The day of the raid, on the 29 th , I-21 launched her own floatplane for a final reconnaissance which mapped the locations of Allied ships, noting that the battleship Warspite was not present, but that the American cruiser Chicago was. Upon landing the E14Y was damaged and had to be scuttled, but the mission was a success.

The three midget submarines launched on the 31 st of May. M-14, launched from I-27, became tangled in the harbour’s anti-submarine nets and was depth charged by one of the patrol craft, before the crew of the sub set off scuttling charges. This destroyed the vessel and killed the two crew. M-24 penetrated the defences and was not spotted until it was close to the Chicago, which spotted the midget and opened fire. Backing off and waiting for the situation to calm down, M-24 later fired both of her torpedoes towards the cruiser. Both missed and instead hit a nearby quay, but the concussion from those impacts sank the stores ship HMAS Kuttabul and damaged the Dutch submarine K-IX. M-24 then escaped from the harbour but never made it back to its mothership – the wreck was discovered in 2006. The final midget submarine, M-21, was depth charged by three Australian patrol boats and sunk. The five large submarines stayed in the area for several days, with I-21 and I-24 shelling positions at Newcastle and Sydney on the 8 th of June.

Operation MI and Operation AL

Several other aircraft-carrying submarines were involved in Operation AL, the invasion of the Aleutian Islands of Attu and Kiska timed to coincide with the Midway operation. Amongst these was I-25, which carried out a floatplane overflight of Dutch Harbour on May 27 th , and I-9 which performed similar flights over Adak and Kodiak islands. However the most important reconnaissance flight was one to investigate Pearl Harbor itself. In a reprise of Operation K, the bombing of Oahu in March 1942, several submarines arrived near the French Frigate Shoals in anticipation of the arrival of a Kawanishi H8K flying boat. However, American ships were stationed in the area and the mission was cancelled. One wonders if the subs used to attack Sydney and Diego Suarez might have been better utilised in reconnoitring Pearl, given subsequent events.

Flight operations for these reconnaissance missions were often very difficult. Aircraft handling facilities on board the submarines were primitive, and it was only after extensive drilling that crews were able to extract the aircraft parts from their watertight containers and assemble the machine on the exposed deck. Poor weather or a rough sea-state could make aircraft launches difficult or impossible – several missions had to be cancelled or postponed until conditions improved. Finding the mothership at the end of each mission was challenging, with submarines forced to use a system of smoke floats to highlight their position – a risky proposition close to Allied bases. Likewise, landing on the ocean at the end of the flight was also a difficult proposition – several aircraft were damaged on landing, many of them beyond the limited repair facilities aboard such small vessels. Many floatplanes had to be abandoned or scuttled after their missions.

The Solomons Campaign

Submarines saw extensive service during the Guadalcanal campaign, during which they carried out several reconnaissance missions to keep tabs on the Allied bases on New Caledonia and in the New Hebrides islands. The Japanese were initially slow to react to the American invasion of Guadalcanal, and the submarine force was no exception. Submarines played only a limited role during the Battle of the Eastern Solomons in August, but in September the effort improved with several boats being deployed to meet the threat. Submarine reconnaissance played a role in this effort. I-31 bombarded an Allied seaplane base on San Cristobal, before sailing to the New Hebrides. Her E14Y overflew Vanikoro on the 11 th and 13 th of September, and in early October I-21’s floatplane discovered an Allied airfield under construction on Espiritu Santo.

Other submarines acted as refuelers for seaplanes, as a ‘mini Operation K’ was instituted. Several boats lurked near the Indispensable Reef, south of Rennell Island and Guadalcanal itself. E13A Type 0s from the seaplane carrier Chitose, which was based at Shortland Island, flew to the reef, refuelled from the submarines, then flew further to search the waters southeast of the Solomons hoping to discover Allied movements. The non-seaplane carrying I-122 initiated the service, followed by I-17 and I-26. The duty was hazardous, as I-26 discovered when she was attacked by American B-17s. although the bombs missed, the submarine grounded and damaged her torpedo tubes.

The End of the Reconnaissance Effort

With Allied air power making itself a nuisance to the submarines, further flights by seaplanes became increasingly hazardous. Many of the submarines were converted so that the aircraft compartments could be used to carry cargo, and the I-boats were used to ferry supplies and ammunition to the beleaguered Japanese garrison on Guadalcanal in much the same way that American submarines had attempted to supply bases in the Philippines. Other submarines served in the same capacity in the Aleutians, where the contributed to the successful evacuation of Kiska before the Americans re-occupied the island in 1943.

With the close of the Guadalcanal campaign, the aircraft-carrying submarine fleet greatly reduced its operations. Although overflights of Allied bases in the South Pacific were occasionally conducted during 1943, the effort was not as sustained as it had been during 1943 – a situation not helped by the loss of several of the boats to anti-submarine units. Two further missions to reconnoitre Pearl Harbor were flown in October, by I-36, and November, by I-9, 1943. The E14Y launched by I-36 failed to return from the mission and it may have been shot down by anti-aircraft fire. The last reconnaissance flight appears to have been that flown by an E14Y from I-10 on the 12 th of June, 1944. This aircraft flew over the new American base at Majuro, and discovered that the American carrier fleet had departed – it was at that time attacking the Marianas.

Hydroaviation of the Japanese submarine fleet in World War II. Part III

In the Land of the Rising Sun, they closely followed the course of experiments conducted in Europe and the United States to create aircraft for submarines. Practical work in this direction took place in the 1923 year, when two Caspar U-1 floated seaplanes arrived in Germany.

After a thorough study of the acquired seaplanes at the Yokosuka Marine Arsenal in 1925, the creation of the first Japanese submarine aircraft, the Yokoshi 1-Go, began. The plane looked similar to the German Caspar U-1, but had a more powerful 80-strong 9-cylinder radial engine of the French company Renault and a four-bladed wooden propeller. The maximum flight speed of the Japanese hydroplane was 154 km per hour (versus 145 km per hour U-1).

Experimental seaplane "Yokoshi" 1-Go (the only photo that has survived)

The Yokoshi 1-Go had a mixed construction: a metal tubular frame, wooden wings, duralumin hood and floats (everything else had a plain skin). For placement in a cylindrical hangar with a length of 7.4 meter and a diameter of 1.7 meter wings and floats undocked. The project stipulated that a team of five people would take four minutes to assemble an 1-Go and an additional 10 – 12 minutes to prepare for the launch, and the disassembly would take about two minutes.

The first prototype of the Yokoshi 1-Go was built in the 1927 year. For sea trials, the Japanese fleet allocated an underwater mine layer I-21 with a surface displacement of 1380 tons (submerged 1768 tons) and a travel speed in the surface position of 14.5 nodes. To accommodate the seaplane behind the fencing of the cabin, a waterproof cylindrical hangar of a “heavy” type was mounted. The launch of the 1-Go into the water and its rise from the water was carried out using a special crane.

1-Go Experimental Yokoshi seaplane reconnaissance aircraft

Intensive testing of the Yokoshi 1-Go was carried out for 18 months in the years 1927-1928. The real time it took to prepare the seaplane for departure was as much as 40 minutes (instead of 16 under the project)! The low speed of the flight and its short duration (only two hours) were also unsatisfactory. In passing, it turned out that the submarine with aviation the hangar should have a large displacement.

The Japanese fleet refused to accept the Yokoshi 1-Go as an underwater-based reconnaissance seaplane. Only one prototype was built. To continue the work in this direction, before the end of the Yokoshi 1-Go test, in 1928, the Japanese fleet purchased the English Parnol double float seaplane Pato.

Experimental English seaplane “Parnol” “Pato”, 1928 year

At its base in Yokosuka Naval Arsenal, Japanese engineers developed a new seaplane project, the Yokoshi 2-Go, which outwardly resembled its progenitor, but was smaller and became single-seater. The metal tubular frame of the fuselage and wooden wings were covered with canvas. The tail fin is placed under the fuselage, and the horizontal tail is in its upper part. For placement in the hangar of the submarine wings and floats made removable. The power plant "Yokoshi" 2-Go was a licensed copy of the English radial five-cylinder 130-strong engine "Mongoose".

The first prototype of Yokoshi 2-Go is lifted with a special crane aboard the I-21 submarine.

Built in May 1929, the first 2-Go prototype passed the fleet for carrying out tests on the underwater mine layer I-21, which lasted until September 1931. Based on the test results, it was decided to put on a seaplane a more powerful seven-cylinder radial Japanese engine "Gasuden Jimpu" with a capacity of 160 horsepower. With the new power plant, the maximum speed of the Yokoshi 2-Go-Kai (the second prototype received the name) increased to 168 km per hour. The flight duration remained the same - 4 hours 24 minutes.

In flight, the second prototype "Yokoshi" 2-Go-Kai

The design of 2-Go-Kai made small changes - the tail fin has acquired a more traditional form. Wing racks biplane received N-view. The Yokoshi 2-Go-Kai tests were first performed on the same I-21, and in the final stage on the I-52 submarine, which had a surface displacement of 1500 tons (underwater - 2500 tons). At the end of 1931, the tests ended and were found to be satisfactory.

In the hangar hydroplane reconnaissance "Yokoshi" E6Y1 based on a submarine I-5

In 1932, a single float reconnaissance biplane under the designation "Yokoshi" E6Y1 (Type 91 model 1) was adopted. The fleet ordered a total of eight hydroplanes, which were built in 1933 – 1934 by Kavanishi (under the factory designation type N). Such a small number of ordered aircraft due to the weakness of the design, low flight performance and lack of weapons.

"Yokoshi" E6Y1 was the first serial reconnaissance seaplane to base on submarines. In the 1932 year, during the “Shanghai incident,” the E6Y1 (2-Go-Kai) seaplane performed several reconnaissance flights in the Shanghai area. In 1933, an experimental pneumatic catapult was installed on the submarine I-52 and the E6Y1 (2-Go-Kai) actively participated in its testing and fine-tuning. During 1937 – 1938, they were based on the I-5, I-6, I-7 and I-8 submarines, until they were replaced by the more advanced Watnabe E9W seaplanes. Flight Service "Yokoshi" E6Y1 ended in May 1943 year.

"Yokoshi" E6Y1 - the first serial seaplane for submarines

In 1932, the Aichi company commissioned the Chinese Navy to build a prototype of the Aichi AB-3 ship-based reconnaissance seaplane, similar in size and capabilities to the Yokoshi E6Y1. The plane had a folding outer wing console. The tests were successful, but no orders for mass production from China followed. The command of the Japanese fleet did not show interest in this development, since such a plane had already been put into service.

The prototype of the reconnaissance hydroplane "Aychi" AB-3, 1932 year

Basic tactical and technical characteristics of the first Japanese submarine aircraft (1927 – 1932 years)

Aichi AB-2 Experimental Catapult-Launched Reconnaissance Seaplane - History

By Gary Mcintosh

The Fletcher-class destroyer was one of the finest, most versatile warships of World War II. More than 170 of them were built, a figure that far exceeds the total of any other type of warship of the era. From 1943 until the end of the war, Fletchers participated in virtually ever campaign in the Pacific.

The U.S. Navy was justifiably proud of the design even its replacement, the Sumner-class, was visually similar. The Navy was not averse to experimenting with the design, however, and chose it as the experimental platform for one of the most unusual modifications ever made to a destroyer when it added a seaplane to a handful of ships that were under construction.

The Idea to Equip Destroyers With Sea Planes

The idea was not entirely new. The U.S. Navy had toyed with the idea of mounting a seaplane aboard a destroyer as early as 1923, and chose the USS Charles Ausburn as the experimental platform. On August 29, 1923, at Hampton Roads, Virginia, and with assistance of the Naval Air Station and a crew from the aircraft carrier USS Langley, the plane was mounted aboard the destroyer.

On September 1, 1923, the Charles Ausburn steamed from Hampton Roads for experimental operations and battle practice. The plane would be lowered to the surface for takeoff and then hoisted back to its perch near the bow. The experiment was short-lived, and the plane was soon removed.

The idea apparently lay dormant for a few years but was never completely forgotten. In 1940, the four-piper destroyer Noa was fitted with a boom and an XSOC-1 seaplane. The airplane was lowered into the water, where it would make a conventional run to become airborne. During 1940, the Noa conducted several operations with the floatplane, apparently satisfactorily enough that the Navy Department decided to mount seaplanes with more sophisticated launching methods aboard some of the its other destroyers.

On May 27, 1940, Secretary of the Navy Charles Edison directed that six destroyers of the new Fletcher class be equipped with a catapult-launched floatplane and all necessary components to make it operable. An official Navy document, BuShips Drawing 305055, approved on September 12, 1940, was drawn to include the modifications necessary to mount the plane aft of the superstructure between gun mounts 53 and 54. The plane and its equipment would replace a 5-inch gun mount, a torpedo tube mount capable of launching five torpedoes, two twin 40mm guns and their fire directors, and three 20mm guns. Concerned about the possible consequences of “dive bombers approaching from astern” created by the loss of most of its aft armament, the Bureau of Ordnance requested that “the maximum number of machine guns also be mounted aft for protection.”

The Bureau of Ordnance was not the only department that viewed the proposal with a lack of enthusiasm. Admiral Ernest J. King, Commander in Chief, United States Fleet, also was concerned about the loss of gun and torpedo firepower and suggested the design order be rescinded. The Bureau of Aeronautics voiced its opinion that “the advantages to be gained from the necessarily limited operation of the aircraft do not warrant the necessary sacrifice of other features.” Finally, the Bureau of War Planning added, “The price necessarily paid in loss of other valuable military characteristics is unjustifiably great.” Despite their objections and concerns, construction was begun on the first of the catapult-equipped destroyers.

Converting the Destroyers

The ships chosen for the modifications were the USS Hutchins, Pringle, Stanly, Stevens, Halford, and Leutze. The Pringle, Stanly, and Stevens were all built at Charleston, South Carolina. The Hutchins was built at the Boston Navy Yard, and the Halford and Leutze were built at the Puget Sound Navy Yard at Bremerton, Washington. There is some disagreement about how many of these ships were actually built with the modifications with some historians stating that only three of the ships were built and others insisting that five were. All agree that modifications to the Leutze were cancelled before the conversion began. There is no doubt that the Pringle, Halford, and Stevens were built with the modifications and references mention that the Stanly’s seaplane catapult was removed around December 30, 1942. There is no record of the Stanly ever using the catapult. Evidence is even less convincing that the Hutchins was constructed with the equipment the ship’s official history does not mention the catapult or floatplane at all.

The plans called for a rotating catapult similar to those aboard cruisers and battleships. The catapult was rotated to the ship’s starboard side to launch the plane and a derrick-hoist mounted on the port side was used to recover the plane. When not in use, the hoist was stowed on the deck.

A 1,780-gallon tank for aviation fuel was placed below deck aft of the superstructure. The huge tank was surrounded by a cofferdam filled with carbon dioxide as a safety measure. A fuel line ran from the tank along the port side of the ship to the plane for fueling. A compartment aboard the ships provided storage for tools and spare parts.

The magazine normally used for the 5-inch gun was used to store the bombs and depth charges carried by the plane. The 5-inch gun mount base and the ammunition hoists were left in place, apparently to facilitate the conversion to the conventional Fletcher design in the event the seaplane idea did not work.

The Vought OS2U Kingfisher Scout Plane

The plane selected for use aboard the Fletchers was the Vought OS2U Kingfisher scout/ observation plane with a top speed of only 125 knots. In theory, it was to be used for scouting, spotting, and antisubmarine warfare when the destroyers were operating without heavier units that would normally provide air support. In addition to its regular crew, each destroyer would carry a pilot, a radioman/gunner, an aviation ordnanceman, and an aviation mechanic.

In its theoretical role of scout plane, the pilot would fly out of sight of the ship searching for enemy shipping. As a spotting plane for shore bombardment, it would circle between the ship and the beach, relay information about the target, and assist in directing the ship’s fire. The plane could also carry depth charges and bombs to be used against enemy submarines, but this was considered a secondary role. Because it lacked tracking gear, the plane could only be used against submarines if its crew spotted a periscope or a Japanese submarine running on the surface. The plane could also be used for mail runs when the ship had been at sea for extended periods of time, and on at least one occasion aboard the Stevens it was used for towing target sleeves for gunnery practice.

Commissioning the New Destroyers

The Hutchins, Pringle, and Stanly were all commissioned in 1942, and the Stevens and Halford in 1943. The Pringle was the first of the destroyers to actually have the catapult and related equipment aboard, and in January 1943 it became the first destroyer to launch an airplane from its own deck. However, during the recovery process a design flaw was found in the hoisting equipment and the ship was unable to recover the airplane as planned. The catapult, hoist, and related equipment were removed shortly thereafter. The equipment was also removed from the Stanly about the same time.

Recovering the catapult-launched Kingfisher aircraft while at sea was a perilous task for the crews of Fletcher-class destroyers, and this particular attempt by sailors aboard the USS Stevens reveals some of the difficulties encountered in the open sea.

The Stevens and the Halford were launched after the catapult equipment had been removed from the other three ships. Fitted with a redesigned hoist, the Stevens was commissioned on February 1, 1943 the Halford was commissioned on April 10, 1943. Of the six ships originally selected for the modification, only these two ships went into combat with planes aboard.

48 Launches and Recoveries

At 8:30 am on Tuesday, April 6, 1943, at Guantanamo Bay, Cuba, Rear Admiral Morton Deyo, Commander of Destroyers, Atlantic Fleet, came aboard the Stevens to watch the first launching of its Kingfisher. Shortly after 9 am, Lieutenant H.W. Smith, the pilot, climbed into the cockpit and fired the engine. He brought the engine to full throttle, set the trim on the plane so that it would fly even if he were to black out from the force exerted on him by the launch, and signaled to Leroy Fadem, the torpedo/catapult officer, that he was ready. Ensign Fadem gave the order to fire the catapult, and at 9:14 the plane roared down its length and into the air. The plane was back aboard by 11:25, making Stevens the first destroyer to successfully launch and recover an airplane, thereby carving a niche for itself in U.S. Navy history. The crew would eventually conduct a total of 48 successful launches and recoveries. While the hoist performed without a problem, a recommendation was made that additional bracing be added to strengthen it, which was done upon the Stevens’ return to the states.

Following shakedown cruises in the Atlantic, where she steamed from Guantanamo Bay to Portland, Maine, the Stevens passed through the Panama Canal on July 26, 1943, on the way to Pearl Harbor. There she met up with the Halford, which had departed from San Diego on July 5 and arrived in Pearl Harbor five days later. In the early stages of their tours the two ships operated with each other as they tested the feasibility of carrying the scout planes on smaller vessels. Both ships participated in the Marcus Island raid on August 31, 1943, and returned to Pearl Harbor on September 7. During the return from Marcus Island, both destroyers launched and recovered their aircraft. Both conducted patrol duty near Hawaii until they temporarily parted company, with the Stevens participating in the Tarawa attack on November 19, 1943, and the Halford in the Wake Island attack on October 6, 1943. That same day the Stevens began its return voyage to Mare Island, California, near San Francisco, to have its forward 20mm guns replaced with Bofors 40mm guns.The Halford followed shortly thereafter. Following reconfiguration of the standard Fletcher design, both left Mare Island on December 6, 1943, and arrived in Pearl Harbor on December 10.

Troubles With the Sea Plane

Living with the seaplane was not easy, and the sailors aboard the Stevens did not like having it aboard. Although the plane itself was more than capable of doing its job when in the air, its presence aboard the Stevens created a number of problems for the ship and its crew. The installation of the catapult and subsequent removal of the guns that would normally have been there caused a significant loss in firepower vital to the ship’s defense. The presence of the plane also made the destroyer appear to be a light cruiser and cultivated the fear among the Stevens crew that the ship might be mistaken for one and consequently draw additional enemy fire or air attack. Finally, the huge fuel tank presented a potential catastrophe should it be hit by enemy fire. These thoughts may also have crossed the minds of Navy brass, for following the Tarawa attack the Stevens remained in the vicinity of Pearl Harbor conducting antisubmarine warfare exercises until its departure for Mare Island to be refitted. Immediately following the Wake Island raid, the Halford was also ordered to Mare Island.

Repairing the airplane when the ship was at sea was also a problem. Replacement parts stored aboard ship were not always sufficient to make repairs to the plane, necessitating a return to port and reducing the amount of time actually spent at sea. The alternative was for the plane to be inoperable for a period of time. A related problem, albeit minor, was of special concern to the aircrews. They were paid a premium for logging a specified number of hours in the air. If they did not fly, they did not get paid the premium. Naturally, the air crews wanted to log as many hours as possible.

Difficult Recoveries

Perhaps the biggest problem created by the plane, however, was recovering it while at sea. The placement of the catapult and airplane amidships, rather than at the stern as on most cruisers and battleships, created a number of problems. In heavy seas, the destroyers would roll, and if the plane was suspended from the hoist, it would alternately bang into the side of the ship when it rolled to starboard or crash into the ocean on the port roll, damaging both the plane and the ship. This was less of a problem on cruisers and battleships because the larger ships tended to be more stable and the scout plane was launched and recovered from the stern of the ship. The destroyers did not have the luxury of the extra room the stern was reserved for depth charges and smoke screen generators.

Standard recovery procedures for shipboard planes included a turn by the ship, thus smoothing the water behind the ship and creating a place for the plane to land. Battleships and cruisers had no problem creating this “slick.” The two destroyers, because they were much smaller, were not always successful in this endeavor, especially in heavy seas.

Finally, while the plane would land behind the ship it had to taxi to the side of the moving destroyer and onto a rope “sled” to be hoisted aboard. Because the ship was normally moving faster than the plane could taxi, the ship itself would have to slow down considerably, coming to a virtual standstill.

A barely moving American warship at sea made an excellent target for Japanese submarines. While neither ship was actually attacked while recovering the plane, the sailors aboard the two ships nonetheless were relieved when the plane was back aboard and the ship was underway once more.

A Disastrous Demonstration

First Lieutenant Stan Lappen, damage control officer of the Stevens, recounted an incident that occurred during the recovery of the airplane. “We were returning from a raid on Tarawa Island when the Task Force Commander [Rear Admiral Charles Pownall] wanted to see how the plane operated off a destroyer. We launched the plane, and it made a few runs around the Task Force before coming in. The sea was choppy and the plane was having trouble making much headway on the water after it had landed, and we couldn’t make much of a slick to smooth the water for it. We had to slow down to almost a stop so the plane could catch up to us.

“We finally got the winch cable attached to the plane, but we were moving so slowly that we were rolling heavily from side to side. Since we had to pick the plane up off the port quarter, the roll was a problem. It was necessary to get the plane up rather quickly once it was hooked onto the cable. Just as we got the plane out of the water, the power temporarily failed on the crane, leaving the plane dangling on the end of the cable. As we rolled to port the plane hit the water, and as we rolled to starboard it swung into the ship. The pilot, my roommate [Lieutenant (j.g.) Hal Smith], jumped from the plane and caught the life rail. We grabbed him and pulled him on board. His radioman-mechanic jumped or fell into the water and had to be picked up by the motor whaleboat. The plane hit the side of the ship a few times, demolishing its wing. It looked AWFUL!”

Electrician’s Mate 1/C William Wickham recalled that the pilot had extricated himself from the plane and had managed to get out onto the wing, where he made a perfectly timed leap toward the destroyer as it began another roll and just before the airplane smashed into the ship again. Smith, the pilot, was grabbed by a “big, brawny machinist’s mate who just happened to be standing there watching the operation” and pulled aboard. According to Wickham, cheers erupted from the onlookers. Wickham also recalled that the radio operator who had taken the unexpected dip into the Pacific had several comments that he shared with the crew, mostly about the intelligence of the their ancestors.

A Vought OS2U Kingfisher scout/observation plane takes off with the assistance of a catapult installed aboard a U.S. Navy Fletcher-class destroyer.

Launching the Kingfisher

Launching the plane could be equally difficult. Lappen also provided this interesting insight into the launching process, as well as to what the crew of the airplane was thinking during the launch. “When I first went on board the Stevens, the pilot was my roommate. During the night he would have nightmares, yelling, “Now! Now!” I asked him about this, and he explained. Since the catapult was about amidships, it had to be swung out at a right angle to the ship’s progress for the launch. This meant that the ship’s headway did not provide any headwind for the plane as it traveled down the catapult. The OS2U needed 90 knots to become airborne. The short catapult plus no headwind meant that it would just barely make the 90 knots at the end of its catapult run. With the catapult out at right angles to the ship’s heading, the roll of the ship would be increased and could be used to help the plane’s launch. However, the catapult charge had to be fired when the catapult was at its lowest point, so that the roll toward the opposite side would raise the catapult end, flipping the plane into the air as it left the catapult. The pilot’s nightmare was that the torpedo officer might not fire the catapult charge at the right time and the plane would arrive at the catapult end on the down roll, driving the plane directly into the drink.”

The Stevens made many successful launches, never sending the plane into a 90-knot dive into the ocean, but it was always a harrowing experience for the pilot and radio man, as well as the Stevens crew.

Ending the Experiment

Life with the seaplane was not easy, even when it was not being launched or recovered. Seaman 2/C William E. Wenger was aboard the Stevens from its commissioning in Charleston until just before it returned to Mare Island. He was transferred to another ship at Pearl Harbor. He recalled this incident aboard the Stevens. “We went on a shakedown cruise to Cuba and the surrounding waters. Of course, there were German subs in the area, so the plane was always swung out on the catapult during morning and evening General Quarters. One day we were shooting at towed targets from land-based planes for antiaircraft practice as well as for making adjustments on the firing arcs of our shipboard 20mm and 40mm guns. The guns were fitted with ‘stops’ to prevent them from rotating and firing past a certain point. However, during one practice session, the stops failed on one of the 20mm and the gunners shot the tail off the OS2U. I never saw two guys abandon an aircraft so quickly! The skipper and the gunnery officer were ticked off, and we wound up with a bunch of junk on our catapult.” The damaged airplane was replaced upon the ship’s return to the United States.

In July 1943, just prior to the Stevens’ departure for the Pacific Theater, Rear Admiral G.J. Rowcliff came aboard. Admiral Rowcliff conducted interviews with the ship’s officers and came to the same conclusion that everyone aboard the Stevens already had: an airplane aboard a destroyer was not a practical idea. In a letter to the general board, he wrote, “This installation would be of extremely limited usefulness on account of the difficulties of stowage, handling, service, launching, and recovery. It would appear that the use would be limited to messenger or quick reconnaissance work of a special nature under favorable conditions of use, operating by stealth or without much opposition.” Nonetheless, the Stevens steamed for the Pacific still carrying her albatross.

While the Stevens was performing its duties in the Pacific, the conversation regarding the catapult and the airplane continued back in the States. The Bureau of Ships (BuShips) requested that the Norfolk Navy Yard submit plans and a cost analysis for widening Stevens’ deck around the catapult. The plans were submitted on September 8. Convinced of the uselessness of the catapult-equipped destroyer, Admiral Chester Nimitz, Commander in Chief, Pacific Fleet, had seen enough. On October 13, he requested authorization from BuShips to have the equipment removed from the Stevens and the Halford, and Admiral King, who had opposed the idea from its inception, concurred. On October 15, 1943, the order was issued directing the removal of the equipment from the two ships. The Stevens was already at Mare Island for installation of the 40mm guns when the order was issued. After conversion to conventional Fletchers, the two departed Mare Island for the Pacific in December.

From Kingfishers to Helicopters

The Stevens’ experiment with the seaplane lasted slightly more than a year, but it certainly provided memorable experiences for the crew. During the time the plane was on the Stevens, the ship participated in two engagements with the Japanese, the raid on Marcus Island on August 31, 1943, and the attack on Tarawa on November 19, 1943. During both actions, the Stevens was part of a carrier group that provided the air cover for the task group, and its Kingfisher was never used for antisubmarine warfare or fire direction. It was used occasionally in its role as a scout plane, but it never spotted any Japanese shipping or encountered any Japanese airplanes.

In retrospect, the idea of mounting an airplane aboard a destroyer may have seemed like a good idea in 1940, when there were fewer ships with the capacity to launch aircraft. However, with the massive buildup of the American fleet by 1943, the destroyer-mounted observation plane was an idea whose time had passed. Due to their greater size, the newer battleships and cruisers could more easily handle the problems associated with the airplane. It should be noted, however, that aviation did eventually return to the decks of destroyers, when the Navy began equipping a much later generation with helicopters.

The Stevens and its sister ships were ahead of their time, but they proved that aircraft could successfully operate from smaller naval vessels.

Operational history [ edit ]

Two prototypes of the AB-13, designated Experimental 10-Shi [a] Observation Aircraft and with the short system designation F1A were built, the first a floatplane and the second with wheeled undercarriage, both being completed in 1936. Α] Although Mitsubishi's competing F1M1 prototypes had poor stability both on the water and in the air, they had superior performance to Aichi's design. Mitsubishi redesigned its aircraft as the F1M2, eliminating its handling problems, Β] and it was selected for production in 1940. Γ]

Watch the video: In-Box Review - 172 Hasegawa - Aichi E13A1 Type-Zero Jake wCatapult (January 2022).