H.M. Balloon Factory NS (North Sea)
Another trefoil-section vessel, the 'North Sea or 'NS' class was the last non-rigid airship type to be built for the Royal Navy, the first being ordered in January 1916 and delivered to the naval air station at Pulham in February 1917. The original idea had been for an airship which could carry out convoy duties and also co-operate with naval surface vessels, a concept that was never put into practice, the whole 'NS' fleet being used for patrol duties. One reason for this decision was the trouble that was experienced with the Rolls-Royce engines first fitted, the problem lying with the over-long shafting, about 3.05 m (10 ft) in length. It was only when this complicated transmiss-ion and the engines had been exchanged for direct-drive Fiats, that the type was able to prove its usefulness; previously only 18 were delivered, a mere 12 being with operational units.
Although a variety of car configurations was encountered, all of them were of similar lines, with the powerplant mounted in a separate nacelle joined to the crew quarters by a wooden catwalk. This forward part of the car had been designed with some consideration to the comfort of its occupants. Such additions as a chart table and bunks were now essential, since the 10 men aboard were expected to operate as two watches, five being on duty while the remainder rested.
From July 1917 the small number of North Sea airships then in use were all based on the Firth of Forth at East Fortune, but by the end of the war over 100 had seen service. An early example (NS14) had gone to the United States and become A5580, while NS6 became a familiar sight to Londoners as a result of its frequent appearances over the capital; and in 1919 NS11 established an endurance record for a non-stop cruise of 6437 km (4,000 miles) in 101 hours.
Although its primary duty was to attack U-boats with its cargo of bombs, an historic use for NS7 and NS8 was to make up the aerial force with the Brit-ish fleet sent to accept the surrender of the German naval forces on 21 Novem-ber 1918. All convoy protection and coastal patrol airships carried about 181 kg (400 lb) of bombs with which to attack U-boats, but the useful load varied with the water ballast carried. Earlier models of the 'NS' class were powered by a pair of 186.4-kW (250-hp) Rolls-Royce engines, while latterly NS12 to NS18 received 223.7-kW (300-hp) Fiats.
Type: convoy escort airship.
Powerplant: two 186.4-kW (250-hp) Rolls-Royce Eagle III V-12 or 193.9-kW (260-hp) Fiat A.12 six-cylinder water-cooled piston engines
Maximum speed 93 kph (55 mph)
Service ceiling about 7010 m (23,000 ft)
Range 4828 km (3,000 miles)
Useful lift 3810 kg (8,400 lb)
Width 17.30 m(56 ft 9 in)
Length 79.86 m (262 ft 0 in)
Volume 10194 cu.m (360,000 cu ft)
Armament: four or five 7.7-mm (0.303-in) Lewis machine-guns on free mountings, plus bombs