SSZ-class blimp

The SSZ (Sea Scout Zero) blimps were developed in United Kingdom during World War I from the earlier SS ("Sea Scout") class. The main role of these craft was to escort convoys and scout or search for German U-Boats.

Design and development
The SSZ was built at the Royal Naval Air Service (RNAS) airship station at Capel-le-Ferne near Folkestone to the design of three officers that were serving there as a successor to the SS class.

Similar to other SS class types, the SSZs had an envelope of 70000 ft3 capacity containing two ballonets of 6375 ft3 each; and like the SSPs, the fuel was contained in aluminium tanks slung on the axis of the envelope.

The design of the car was a departure from that of other SS types. It was streamlined, boat-shaped and watertight, was floored from end-to-end, and was enclosed with sides of fabric-covered 8-ply wood or aluminium. The car was comfortable and accommodated a 3-man crew – the forward position being occupied by the wireless operator/gunner with the pilot seated amidships, and the engineer was stationed at the rear.

A single water-cooled 75 hp Rolls-Royce Hawk engine was mounted on bearers above the level of the rear of the car, and drove a 9 ft diameter four-bladed propeller in pusher configuration.

The SSZ design was judged superior to the SSP, which had been developed at RNAS Kingsnorth at the same time, and so the SSP was cancelled.

Operational history
The average patrol lasted eight hours, but there were instances of flights of much greater duration – three of 25–26 hours; one of 30 h 20 min; and a record of 50 h 55 min held by SSZ.39 in the summer of 1918.

On 16 August 1918, a makeshift SSZ ship was being assembled from a disused envelope and a spare SS Zero car at RNAS Howden airship station. Petrol fumes from a spillage in the car were ignited some time later by a spark when the radio equipment was being tested; and the ensuing fireball, fed by fuel and gas, completely enveloped and destroyed both the SSZ and R23X class airship R27 with which it was sharing a hangar. Although the hangar itself survived, one airman lost his life, and two further blimps that were moored nearby, SSZ.38 and SSZ.54, were also destroyed. The SSZ's greater stability in flight and longer hours of endurance enabled them to operate in worse weather conditions than had previously been attempted, and early in 1917 all existing SS types were superseded by the SS Zero. They were turned out as fast as they could be built, and a total of 77 SSZs were produced between 1916 and 1918, two of which were acquired by France and two by the United States.

Operators

 * Royal Navy
 * US Navy
 * Royal Navy
 * US Navy
 * US Navy