Schwimmweste Model 10-30 B-2
Initially, the carbon dioxide cartridge-operated inflatable life preserver used by the German Luftwaffe appeared in the form of the Model 10-30 (FL30154), a rubberized canvas fabric waistcoat providing buoyancy at the front as well as at the back by filling a contunuous inflatable envelope. This design unfortunately resulted in a tendency to rotate the injured or unconscious airman in the water, the latter ending up face-down. The vest was inflated by operating a twist open valve on a cartridge located at the lower left front flap. In case of need an additional mouthpiece served to top up the level of air. Three strap and buckle fasteners (collar, chest, waist) assisted by an under-leg strap provided a snug fit.
An inflatable life preserver has some distinct advantages over design using kapok as a floating aid. Much more comfortable to wear and less bulky, it also needs less space for storage. On the negative side definitely is to be mentioned the potential leakage due to tears or other damage caused by shrapnel, bullets, or other sharp edged objects and shapes.
During the Battle of Britain the Luftwaffe didn't remain unaware of the flaws of the design, thus the improved Model 10-30 B-1 appeared in late 1940. A bladder type chamber now provided buoyancy behind the head, around the shoulders and on the chest, resulting in a much more stable face-up attitude of a floating airman. Furthermore the waist strap was significantly enlarged. In 1941 the B-2 variant was introduced, which now featured plastic fittings instead of metal for the cartridge and mouthpiece, thus reducing the risk of frostbite while saving precious material.
With a few more alterations in materials used for its production, the design remained in use throughout the remainder of the war. It is interesting to note that various RAF pilots - for example Battle of Britain top ace Eric Stanley Lock and "Dambuster" legend Guy Penrose Gibson - wore "liberated" 10-30 vests, as the auto-inflation feature of the German design was considered superior to the oral inflation method used by early RAF life preservers.