SS class airship

The prototype SS craft was created at RNAS Kingsnorth on the Hoo Peninsula,[6] 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.[7] It was ready for evaluation trials within a fortnight of approval being granted for the scheme,[8] 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!"[2]

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."[4]

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).[8]

The envelope of the experimental prototype had a volume of 20,500 cu ft (580 m³) of hydrogen gas, but production models used a 60,000 cu ft (1,700 m³) envelope of similar shape that provided a typical gross lift of 4,180 lb (1,900 kg),[8] a net lift of 1,434 lb (650 kg) and a disposable lift of 659 lb (299 kg) with full fuel tanks and a crew of two on board.[9] 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[10]), 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.[9]

The envelope contained two ballonets of 6,375 cu ft (180.5 m³) 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".[11]

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.[12][13] 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.[12]

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 75 hp (56 kW) Renault engine driving a 9 ft (2.7 m) diameter four-bladed propeller.[2][12]

The pilot was seated behind the observer, who also served as the wireless operator. A camera was fitted,[14] 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.[15] The bomb sight and release mechanism were located on the outside of the car on the starboard side of the pilot's position.[16]

The Airships Ltd. design initially used 60,000 cu ft (1,700 m³), and later 70,000 cu ft (2,000 m³) 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.[17]

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 70,000 cu ft envelope to maintain a reasonable margin of lift. A water-cooled 100 hp (75 kW) Green engine was fitted in tractor configuration, and fuel was carried in two aluminium tanks supported in fabric slings suspended from the envelope, saving 100 lb (45 kg) in weight compared to the internal tanks fitted to the B.E.2c.[18]

An SS airship lands after a patrol, showing the large crew required for handling on the ground. Another SS airship can be seen in the air.

At the same time a number of new air stations were set up as well as a training station at Cranwell.[19] 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.[2][20]

_{Notes: · [BE] B.E.2c car · [MF] Farman car · [AW] Armstrong Whitworth car}