SS class airship
SS (Submarine Scout or Sea Scout) class airships were simple, cheap and easily assembled small non-rigid airships or "blimps" that were developed as a matter of some urgency to counter the German U-boat threat to British shipping during World War I. A secondary purpose was to detect and destroy mines. The class proved to be versatile and effective, with a total of 158 being built in several versions. Requirement. Soon after the outbreak of World War I, the threat to British shipping from German submarines became increasingly apparent, with numerous losses occurring during October and  November 1914. Then, on 4 February 1915, a communiqué issued by the Imperial German Admiralty declared that: "All the waters surrounding Great Britain and Ireland, are hereby declared to be a war zone. From 18 February onwards every enemy merchant vessel found within this war zone will be destroyed." The situation had become critical and the Admiralty recognised that airships would be effective at spotting submarines and useful for Fleet observations, but at that time Britain's airship fleet consisted of just seven craft – four RNAS airships (HMA 17, 18, 19, and 20), two continental ships and a small Willows  training craft – with only four airfields existing that possessed hangars capable of housing them. Consequently, on 28 February the First Sea Lord, Admiral Lord Fisher, called a meeting with Commander E. A. D. Masterman (Officer Commanding the Naval Airship Section) and representatives from Vickers and the London-based firm of Airships Limited to discuss the possibilities of creating a fleet of suitable patrol airships, sometimes referred to as "scouts". Design and development. The type was to have a speed of , carry a crew of two, of bombs, wireless equipment, fuel for eight hours flying, and capable of reaching an altitude  of . Most importantly the design had to be simple, in order to ease production and to facilitate training of the crews, since the new airships, designated the "Submarine Scout" or "Sea Scout" (SS) class, needed to be operational within weeks rather than months. Prototype. The prototype SS craft was created at RNAS Kingsnorth on the Hoo Peninsula, and was effectively a B.E.2c aeroplane fuselage and engine minus wings, tailfin and elevators, slung below the disused envelope from airship HMA No. 2 (Willows No. 4) that had been lying deflated at the Royal Aircraft Establishment (RAE), Farnborough Airfield. It was ready  for evaluation trials within a fortnight of approval being granted for the scheme, and on 18 March 1915 the first SS class airship entered service. The whole process had taken less than three weeks, and voicing his approval, Admiral Fisher made the famous comment: "Now I must have forty!" The officer commanding the Kingsnorth facility was Wing-Commander N. F. Usborne, who also assisted in the design of the airship. In recognition of his contributions the following comment was made: "Admiral Sueter desires to place on record his high appreciation of the hard work and devotion to the airship cause  displayed by Commander Usborne. Far into the night and the early hours of the morning this scientific officer worked to make these airships a success and due to him in large part their wonderful success was due." Two private firms, Armstrong Whitworth and Airships Ltd., were also invited to submit designs and consequently three versions of the SS class blimp were produced: the SS "B.E.2c", the SS "Armstrong Whitworth" and the SS "Maurice Farman" (thus named because the car designed by Airships Ltd. resembled a Farman aeroplane body). Envelope. The envelope of the experimental prototype had a volume of of  hydrogen gas, but production models used a envelope of similar shape that provided a typical gross lift of , a net lift of and a disposable lift of with full fuel tanks and a crew of two on board. Each of the SS versions used similar envelopes that were composed of four layers: two of rubber-proofed fabric with a layer of rubber between them, and a further rubber layer on the inner, or gas surface. The external surface had five coats of dope applied to it to protect it from the elements and to render the envelope completely gastight. The  first two coats were of "Delta dope" (a flexible dope used for the first time in 1913 on the British Army semi-rigid airship "Delta"), followed by two of aluminium dope and finally one of aluminium varnish. To stiffen the nose of the envelope and to prevent it blowing in, 24 canes were arranged radially from its centre and covered with an aluminium cap. The envelope contained two ballonets of each instead of just one as used on the prototype. These were supplied with air from the propeller draught via a scoop and a slanting aluminium tube to the underside  of the envelope, and then via horizontal fabric hoses containing non-return fabric valves known as "crab-pots". Planes. The original design featured four fins (or planes) and rudders set radially to the envelope: two horizontal fins, and two below the envelope in an inverted V-tail configuration; however, in some cases the two lower fins were replaced with a single central fin that carried a larger rudder. The fins were identical in size and shape, and were constructed of spruce, aluminium, and steel tubing, braced with wire and covered with doped fabric. Versions. SS B.E.2c. Similar to the prototype , the production car was a wingless B.E.2c fuselage stripped of various fittings, and equipped with two ash skids in place of the wheeled undercarriage. Mounted at the front of the car was an air-cooled Renault engine driving a diameter four-bladed propeller. The pilot was seated behind the observer, who also served as the wireless operator. A camera was fitted, and the armament consisted of bombs carried in frames suspended about the centre of the undercarriage and a Lewis Gun mounted on a post adjacent to the pilot's seat. The bomb sight and release mechanism were located on  the outside of the car on the starboard side of the pilot's position. SS Maurice Farman. The Airships Ltd. design initially used , and later envelopes. Dual controls were fitted for the pilot and the observer/wireless operator. Occasionally a third seat was fitted to carry a passenger or an engineer. Renault engines were normally fitted, mounted at the rear of the car in pusher configuration, but a Rolls-Royce Hawk proved effective in one instance. The type was slightly slower than the SS B.E.2c, but the cars were roomier and more comfortable. SS Armstrong Whitworth. The version fitted with  the Armstrong Whitworth F.K. car was similar in many respects to the B.E.2c type, but had a single-skid landing gear with buffers, and required the larger envelope to maintain a reasonable margin of lift. A water-cooled Green engine was fitted in tractor configuration, and fuel was carried in two aluminium tanks supported in fabric slings suspended from the envelope, saving in weight compared to the internal tanks fitted to the B.E.2c. Airship stations. At the same time a number of new air stations were set up as well as a training station at Cranwell. The rigid airship programme  was also gathering momentum, and these stations were later joined by several more that together formed a chain all around the UK coast. Production. Initially undertaken by the Royal Aircraft Factory at Farnborough, production was soon transferred to Kingsnorth, and in addition shortly afterwards to Vickers' works at Barrow-in-Furness and to the Wormwood Scrubs Naval Air Station in London. However, construction at each of the facilities was hampered by aeroplane orders affecting the supply of envelopes. In total, some 60 examples of the three versions of SS class blimp were assembled, costing around £2,500 each (equivalent to  £ in , when adjusted for inflation). Service history and legacy. During the final 15 months of the war SS type airships carried out over 10,000 patrols, flying nearly one-and-a-half million miles in more than 50,000 hours. A total of 49 U-boats were sighted, 27 of which were attacked from the air or by ships. In all, there was only one instance of a ship being sunk whilst being escorted by an airship. An SS B.E.2c set the current altitude record for a British airship when it reached in the summer of 1916, and the sole Hawk -engined SS Maurice Farman on one occasion carried out an extended patrol of 18 hours 20 minutes. Also in the summer of 1916, an Armstrong Whitworth model coated with black dope carried out night-time operations over France, proving that airships could be of value when operating with military forces over land. The SS type was further developed with purpose-built cars to create the SSP (Pusher), SSZ (Zero), SST (Twin) and SSE (Experimental SST) types. Demand for the versatile "Sea Scouts" was so great that a grand total of 158 of all versions and variants were constructed, some of  which were acquired by France, Italy and the United States. Although the SS class types proved invaluable, their use was restricted to coastal patrols in reasonably fair weather owing to their low engine power and comparatively small size. For work farther out at sea and in all weathers, three further classes were developed: the "Coastal", the "C*" and "North Sea"-class ships. Each had larger engines and envelopes, carried more crew, and had greater patrol duration than the previous class ships.