When the USS Tunny launched its first Regulus missile on July 15, 1953, the world entered a new era. Yet the concept of launching missiles or aircraft from aboard a submarine, it turns out, was far from new. As far back as WWI, attempts were made to convert submarines into floating aircraft carriers, and during WWII the Imperial Japanese Navy boasted a fleet of such craft. Here author Terry Treadwell, the world's pre-eminent expert on submarine-launched aircraft, shares some of this fascinating history. For more information, you can purchase his one of his two books on the subject, Submarines with Wings and Strike from Beneath the Sea. Just click on the book cover on the right.

SUBMARINE AVIATION 1914-1964

By Terry C. Treadwell

Reprinted with permission from Naval Aviation News, February, 1983

World War II was brought to the West Coast of the United States early one morning in September 1942 , when a Japanese I-25 submarine surfaced about six miles off Cape Blanco, Oregon. Members of the crew scrambled onto the deck and proceeded to remove from a watertight hangar a small seaplane ­ a Yokosuka E14Y1 - called a Glen by the Allies. They quickly assembled the aircraft and hung two incendiary bombs on its under wing racks. The aircraft normally carried an observer but, due to its attack payload, he had to be left behind for this mission.

The pilot, Warrant Officer Fujita, took off, penetrated the forest belt of Oregon and dropped his two bombs causing, it is thought, some serious fires. A second attack was carried out a week later with similar results. These attacks showed that it was possible to carry out raids from submarines, although the range and bomb loads were very restricted.

The very first aircraft launched from a submarine is attributed to the German Imperial Navy during WWI. The German Army had advanced into Belgium and occupied the Port of Zeebrugge, famous for its giant breakwater. The German Navy then moved its U-boats into the port. One of the first to arrive was the U-12 commanded by Kapitanleutnant Walter Forstmann. A month later, the first contingent of the Imperial Navy's Air Service arrived, commanded by Oberleutnant zur See Friedrich von Arnauld de la Perriere. His unit consisted of three other officers, 55 enlisted men and two aircraft. The aircraft, Friedrichshafen FF-29s, were twin-float biplanes, powered by 120-hp engines.

The mission of the U-boats was simple, to sink enemy shipping. However, the role of the German Navy's air army had still not been clearly defined. It had been created at the very beginning of the war, but what it could or should do had yet to be established.

Friedrich von Arnauld, having received no instructions, decided to develop his own missions. He reconfigured the unarmed FF -29s to carry 26.5 pound bombs, and on Christmas Day one of his seaplanes flew across the English Channel, up the River Thames and dropped the bombs harmlessly on the outskirts of London. Although it was chased by three British aircraft, it returned safely. The aircraft themselves suffered more from fuel problems and faulty ignitions than they did from the British.

Forstmann and van Arnauld decided that if they took an aircraft to sea on the deck of a submarine and placed it in a takeoff position, they could launch the plane by partially submerging. This would effectively increase the range of the seaplanes. On January 6, 1915, the FF -29 was placed across the deck of the U-12 and lashed down. The submarine left the harbor, seemingly dwarfed by the 53-foot 2-inch wingspan, that stretched almost one-third of the submarine's 188-~foot length.

No sooner had the U-12 left the safety of the breakwater than the captain realized that the heavy swell they were encountering might possibly endanger the operation. After less than an hour, it was decided to launch the seaplane. Captain Forstmann flooded the forward tanks and, despite the pitching of the vessel, von Arnauld's aircraft floated off the deck and took off without difficulty. He had intended to rendezvous with the submarine but decided against it. It is not known how close to the English coast the submarine was when it launched the FF-29, but von Arnault flew along the Kent coast undetected and then made his way back to Zebrugge.

The experiment had been partially successful inasmuch as the aircraft had been carried and floated off, but it was realized that calmer seas and more secure lashing of the aircraft were required.

Von Arnauld and Forstmann were eager to try the experiment again but the German High Command vetoed it. The idea lay dormant until 1917, when it was revived by the High Command so that the striking power of submarines could be increased. Some of the long-range, cruise type of submarines were to be equipped with aircraft for scouting purposes. Although plans were drawn up and designs prepared for the quick assembly and dismantling of seaplanes on board ship, the ideas were eventually abandoned.

While the idea was given up by the Germans, in 1927 the British submarine M-2 was commissioned as an aircraft carrier. She was ideal for such an assignment because of the 12-1nch gun that was housed in a turret forward of the conning tower.

The gun was removed and the turret modified to take a specially designed reconnaissance seaplane. Many designs were considered, but the one selected was a two-seat, unarmed, wireless equipped Peto, designed and constructed by George Parnall and Company.

The Peto was not the first British aircraft designed for use on a submarine. In 1916, two Sopwith Schneider seaplanes were carried aboard the E22 submarine, lashed down on the deck. Even earlier, well before 1914, an aircraft called the Bristol Burnley X was built. It was designed to collapse and pack away on surface vessels and on submarines.

The Peto was mated with the ill-fated M-2. The little twin-floated biplane was locked onto a carriage that rested on two rails inside the hangar o~ the forward deck. The hangar crew of 10 found the room inside the hangar very cramped when standing by to get the seaplane launched.

The launch procedure went as follows: The pilot would ascertain from the captain when the boat was likely to surface. As it was impossible to start the engine while submerged, the lubricating oil in the tank and engine was heated up so as to shorten the running-up time once the aircraft was on the catapult.

As soon as the boat surfaced, the launch crew opened the hangar door and lowered it to form part of the launching platform. The airplane was quickly run out on its rails and locked into position at the end of the catapult, after which the wings were unfolded and locked in position.

The captain then turned the submarine into the wind and moved at such a speed as to show sufficient wind on his indicator in the conning tower, which ensured a safe takeoff. After opening the throttles wide and making sure that his engine was running correctly, the pilot raised his hand to indicate that he was ready to take off. The captain gave the order for the catapult lever to be pulled. The aircraft shot forward, slamming the pilot and his observer back into their seats, and was launched into the air. After the seaplane had carried out its objective, it returned to the submarine, landed and taxied alongside. It was then hoisted back on board by means of a small lifting crane on top of the hangar. Of course, all of this was possible only if the weather was calm.

The idea was never a complete success and on the night of January 26, 1933, an announcement from the Admiralty said that the submarine M-2 had dived at about 1030 hours off Portland, Dorset, and had not been heard of since. Destroyers and submarines searched the area and later the same night came the news that an object had been located three miles off Portland; lying in 17 fathoms on a sandy bottom. Salvage craft and divers were sent from Portsmouth and it was confirmed that it was indeed the M-2.

After days of frustration, the Peto was recovered from the submarine's hangar. Badly damaged, she was taken ashore for inspection. She was not preserved. The salvage work was initially abandoned in September, although at one point the M-2 was raised to within 18 feet of the surface before a gale sprang up and the boat sank again. How the accident happened is still a mystery, but it is probable that the inner hatch to the hangar was open at the same time that the hangar doors were, perhaps through a misunderstood order.

While the British were having their problems, across the Atlantic the American Navy had shifted its interest from submarine aircraft to small scouting aircraft carried aboard the airships USS Akron and Macon. The U.S. Navy's interest in submarine aircraft had started way back in 1922. Two Heinkel-Caspar type U-1 submarine aircraft were received at NAS Anacostia towards the end of 1922. One was lost during an exhibition flight the following year and was used for spares for the other. The flight tests were completed by the end of 1923 and, although the aircraft didn't fly off a submarine, it did supply useful information for future designs.

The Navy accepted delivery of 12 additional submarine-based aircraft and, although built by two manufacturers, the design was the same. Six were constructed by the Cox-Klemin Aircraft Corporation of New York and were made of wood and fabric. The other six were manufactured by the Glenn Martin Aircraft Corporation of Baltimore and were largely made of metal. This enabled the Navy to compare the new techniques using metal rather than wood.

During October and November of 1923, tests with the Glenn Martin MS-1 were carried out aboard USS S-1. The S-1 had a complement of aircraft specialists from USS Langley aboard. Their duty was to erect and dismantle the aircraft and stow it away in the pressure-resistant tank aft of the conning tower. Unfortunately, it took nearly four hours to assemble the aircraft. This obviously was unacceptable and so modifications had to be made to cut down the assembly time. The modifications were carried out by the Naval Aircraft Factory at Philadelphia and, although the aircraft was delivered to them late in 1923, it was nearly two years before the modifications were completed.

In the summer of 1926, the complete cycle of assembly, launching, recovery and stowage of the modified Cox-Klemin XS-1, now designated XS-2, was assigned to the S-1. By the end of October, the launching crew had become so proficient with the modified aircraft that they could have the machine assembled, launched, afloat and with engine turning in 12 minutes. It took them only 13 minutes to recover, dismantle and stowaway, which was a truly remarkable feat when compared with four hours on the original aircraft. The XS-2 had an effective scouting radius of approximately 130 miles.

Up to 1931, a number of tiny, foldaway aircraft were designed and submitted to the Navy, but none were adopted. In 1931, the Navy did purchase a Loening XSL-1 amphibian for submarine trials, but a number of modifications had to be carried out to improve its all-around performance. Although it was tested aboard the S-1, it was not accepted by the submarine service. Many reasons were given, including one which rumored that Naval Aviators did not relish the double hazardous duty aboard the old S boats!

The French had attempted to use aircraft on board submarines but met with very limited success. Their one and only attempt was on the 2,800 ton Surcouf, the pride of the French Submarine Services. Built in 1929, Surcouf was the second largest submarine in the world, the first being the British X-1 at 3,050 tons. A match for many surface warships, Surcouf had twin turret-mounted, eight-inch guns and formidable torpedo armament. The biggest drawback was that she was too large and too slow at diving. This meant that she was only at her best when on convoy duty and when her scout seaplane was ahead looking for enemy warships and submarines.

Surcouf had its hangar built as an integral part of the conning tower, and launch and recovery were achieved by using a crane after the submarine had stopped her engines. Tests continued until 1942 when, on the night of February 19, Surcouf was involved in a collision with an American freighter while en route to the Panama Canal. There were no aircraft on board and there were no survivors.

To go back to the Japanese contribution to the submarine aircraft era, it all started for them at the end of the First World War. They acquired seven war-prize U-boats from the German Navy and adopted the best features into the design of their own submarines. The Japanese had always had great interest in the use of submarine scouting aircraft and purchased two Heinkel Caspar U-1 aircraft from the Germans in 1921.

The first operational trials of the aircraft aboard a submarine did not take place until 1927 and, as with the American trials, launching operations were conducted by trimming down the stern and floating the aircraft off. The Japanese by this time had their own design available, very similar to the U-1 but with modifications such as a more powerful rotary engine. Although it was designed in 1925, the aircraft wasn't built until 1927 and operated from submarine I 21 for about 18 months.

The I 21 was too slow and too small for serious operations, so a larger boat was selected and, in 1930, the 1,400-ton I 51 had a compressed air catapult fitted to her after deck together with a hangar capable of taking two aircraft. Also at this time, the Japanese introduced a new aircraft, a 6-shi E6Y1 type 91 small reconnaissance seaplane. It was a miniature copy of the British Parnall Peto and used the same engine, the Mitsubishi Mongoose. By 1932, eight more models were built by Kawanishi and were known as the E6Y1-N. After aeroplanes were tested for three years aboard the I 51, the catapult was removed and the submarine was reassigned to general service.

The early 1930s produced a number of giant submarines based on the design of the huge German U-142 of 1918. Two of these were built with hangars capable of taking two aircraft. Two of these were built with hangars capable of taking two aircraft, a compressed air catapult and a small crane for retrieving the aircraft. Work was completed on these giant submarines in the mid-thirties, and later ones were built so that the aircraft could be launched without the submarine having to stop its engines.

At this time, the Japanese were still at war with the Chinese and these submarines with their aircraft were used in the China Sea as a deterrent against Chinese blockade runners. They appear to have been quite successful and were still in use up to 1941. It was in 1941 that the first submarine-borne operational monoplane came into service - the E14Y1 or, as it was known to the Allies, the Glen. It became the eyes of the Japanese submarine fleet when it set sail to challenge the United States fleet in December 1941. It carried out reconnaissance over Pearl Harbor before and after the attack. Other submarines cruised the South Pacific and their aircraft scouted the harbors of Sydney and Melbourne, Australia, and Hobart, Tasmania. There were a number of kamikaze-type missions carried out by the Glens -- long-range reconnaissance flights that gave the pilot no chance of getting back to his submarine. One example was when submarine I 36 launched her aircraft from 300 miles off the Hawaiian Islands and, although the pilot was able to radio back shipping information, it is presumed that he crashed into the sea and was lost. At the end of 1941, the Japanese had 11 submarines capable of carrying scouting aircraft and, by the end of 1945, this number had increased to 27.

Meanwhile in Japan, work was progressing on their secret weapon and kept so well under wraps that the United States did not find out until after the Japanese had surrendered. The weapon they had been working on was a giant submarine, described as I 400 class, an undersea aircraft carrier with hangar space for three aircraft. It was 400 feet long, displaced 3,900 short tons on the surface and capable of cruising for 31,500 miles without refueling. Originally, 18 were planned but as the war deteriorated material shortages caused the plans to be revised and only five were actually started. By 1945, three had been completed, one was dismantled while still on the slipway and one was destroyed in an air raid. Of three of the original five left -- the I 400, I 401 and I 402 -- two were completed as carriers and one as a supply boat.

Due to the cutbacks of the I 400 class in 1943, smaller, 2,900-ton, I 13 class submarines were converted to carry two aircraft. Of the four converted, two were completed, while the other two were still undergoing construction when the war ended. The I 13 class submarines had heavy-duty catapults fitted on their forward decks, with 12-ton, electric cranes for recovering aircraft.

While the I 400 class submarines were under construction, plans were made to use the submarines and their aircraft for a raid on the Panama Canal. The normal scouting aircraft would be of no use, so a light submarine bomber was needed. The Japanese Navy asked the Aichi Aircraft Company to provide them with a suitable design. One of the requirements was that the aircraft could be catapult launched without landing gear. The reason for this was that the saving in weight would allow for a larger bomb load and a larger fuel supply. After the raid had been carried out, the aircraft would return to the submarine, ditch close by, and the crew would be recovered.

Training for the Canal raids did not progress well. The crews practiced their bombing runs on large scale models of the Canal locks, but were often interrupted by attacks from U.S. Navy carrier aircraft. The beginning of July 1945 brought the first submarine flotilla together, consisting of the I 400, I 401, I 13 and I 14. The task force was equipped with 10 aircraft and, although the two smaller boats did not have the fuel capacity for the round trip to Panama, they were to refuel from the bigger boats.

They were provisioned for a four-month cruise but time had run out. They were diverted to attack Ulithi Atoll where U.S. carriers were anchored. On July 16, 1945, the task force was attacked by carrier aircraft and the I 13 was sunk. The other boats did not press home their attack on Ulithi and all the other submarines were still at sea when the war ended. Not one of the giant submarines saw action in spite of all the time and money spent on them.

The post-war progression in the use of submarines in aviation warfare came when in March 1946 U.S. Navy Secretary James Forrestal approved the converting of two Gato-class submarines to guided missile launchers. The submarines that were converted were USS Carbonero (SS337) and USS Cusk (SS348) . The weapon they were to launch was an improved version of the German V-1 called the Loon. The Loon was later to provide crucial experience and encouragement in the cruise missile program.

The first launch from Cusk was carried out on February 12, 1941, while surfaced off Point Mugu, California. This was the first time a submarine had launched a missile. Earlier tests of the Loon had been carried out at the Naval Air Missile Test Station at Point Mugu. In these tests, Lockheed P-80 Shooting Stars had flown alongside the missiles in case they turned off their course and threatened populated areas. The same idea had been used during WII, when Spitfires and Hurricanes of the Royal Air Force flew alongside the German V-1s and turned them around by using their wingtips.

The submarines had a launching ramp installed on the deck behind the conning tower. The missile was contained in a 10-foot by 30-foot steel, watertight capsule. When the submarine surfaced, the crew would open the capsule, assemble the Loon into a firing position, launch it and return below, leaving the submarine free to submerge. Over the next few years, many test were undertaken, culminating on May 3, 1950, when Cusk surfaced, launched a Loon, then tracked and controlled the missile over a range of 105 miles.

The American version of the V-1 disappeared soon afterwards, as the Regulus submarines came to the fore. These boats, capable of carrying up to five Regulus cruise missiles, seemed to herald the start of a new form of warfare (see the main page). At one time, a series of jet aircraft designs, capable of JATO launch from a Regulus boat, were put forward. None would ever leave the drawing board and, when the last Regulus SSG left commission in 1964, the era of the "submarine with wings" came to a close.

POSTSCRIPT: The "Might Have Beens" of the Modern Era

The presence of the Regulus missile -- essentially a small remote-controlled plane with a nuclear warhead -- in the fleet led to some interesting proposals. Ed Heinemann of the Douglas Aircraft Co. demonstrated that a Douglas 640 (top) or a modified A4D Corsair could fit into a lengthened Regulus missile hangar (center). He also designed a smaller, jet-propelled seaplane which fit the standard specifications (top). Either plane would be lifted off the sub's deck by JATO rocket. The design went nowhere although the compact little craft's lines bear a striking resemblence to the A-4 Skyhawk leading some to call it "Heinemann's Hot Rod."

The drawing shown below of the USS Grayback, SSG-574 are of course purely speculative and come from an article in Mechanic's Illustrated. Grayback was actually a diesel submarine, not a nuke boat as shown in these drawings (which seem more likely to have been inspired by the atom-powered USS Halibut). In this arrangement aircraft would be stowed in a massive sliding-door hangar and launched either by JATO or, if the sea was calm enough, via ocean takeoff. Like all other designs, this one had a flaw in that rough seas would make launch and/or recovery of aircraft difficult.

Experience in varying sea conditions launching Regulus I and II missiles showed that launches were possible in foul weather. During an arctic operational readiness test in the 1950s, a missile aboard USS Tunny dislodged from the launcher due to heavy seas, causing a JATO misalignment that resulted in loss of the bird. One can only speculate about the wisdom of launching manned aircraft in this fashion.

Other bold designs did crop up during the 1960s, including plans to pair the Convair "Skate" seaplane with a submarine, primarily to extend the aircraft's range. The Navy also developed a VSTOL aircraft with Grumman called the "Nutcracker" which could be captured by a boom. The idea never gained much momentum.

About the same time, the British designed a "skyhook" for use with their VTOL Harrier jet. The hook, which operates a bit like the trapeze used aboard American aircraft-carrying dirigibles of the 1930's, would allow Harriers to be recovered by surface ships or submarines. The concept has been tested using a prototype hook on a crane, but no plans for deployment ever developed.

The guided missile and aircraft carrying submarine however is one craft which the world is certain to see more of in the near future. The U.S. Navy is on the verge of commissioning several new SSG boats, and the Chinese (see photo below) and Russians maintain boats capable of launching missiles. Almost certainly in the future these boats will launch not just missiles, but remotely-operated-vehicles for surveillance and, perhaps, manned aircraft for tactical strikes.

Text and photographs copyright Terry C. Treadwell and the Naval Aviation News. This text and accompanying photos may not be reproduced, reposted on the internet, published or edited without permission.

ABOUT THE AUTHOR

Terry C. Treadwell is formerly the European Correspondent for the U.S. Navy's Naval Aviation News and a frequent contributor to magazines. He is the author of two books, Submarines with Wings and Strike from Beneath the Sea, both of which chronicle the use of aircraft and missiles from submarines. Born in Bournemouth, England, he lived for a short time in Australia but now lives in his home town.