Ever ran a kite out as a kid? Ever tried it from the back of a boat moving at 20 mph? Ever done it with a sailor hanging off of it with a phone and a pair of binoculars? Well the Germans did it in World War II.!
Before the age of radar and sonar, the only way two ships would discover each other was if they could visually see one another. The curvature of the earth means that the higher up you are the further over the horizon you can see, hence ships having a elevated observation platform ("crows-nest") for centuries. Submarines are very low in the water so to gain a visual advantage over their prey, an idea was hatched in Hitler's Kriegsmarine to get a man in an observation post as far as 700 feet above the boat. While some large experimental Japanese and British submarines of the same time period carried and used small seaplanes, the German U-boats were too small to accommodate aircraft. Taking up less space was a kite, specifically a very large kite capable of carrying an intrepid lookout high into the air where he would be able to greatly extend the visual range of the warship.
The kite, constructed by the German firm of Focke-Achgelis was designated the Fa-330 Bachstelze (Wagtail). Focke-Achgelis was dedicated to early helicopter development and the Fa-330 looks more like a very small motor-less whirlybird than any kite. The craft, also referred to as a 'rotor kite' or 'gyro-glider' was 14 feet long and weighed some 180 pound unloaded. Three rotors with a combined diameter of 24 feet provided lift. Every part was sized so it could pass through the U-boats hatches. It was carried in two watertight storage compartments and took about twenty minutes to assemble. Operation was very simple, with the 'pilot' strapping himself in and waiting for the surfaced U-boat to achieve a forward speed of at least 15 knots, thus rotating the blades and rising from the stern of the submarine. The craft was tethered to the ship via a 1000-foot long steel tow cable which was reeled out and back in by a winch. When the 'pilot' achieved altitude he would commence his observation of the horizon with a pair of binoculars and communicate back to the U-boat via a closed circuit phone. He had simple controls to adjust pitch. If the craft was spotted, developed problems, became unstable, or the submarine had to crash dive it was considered expendable and the pilot jettisoned the aircraft, returning to the sea in a parachute. Parachute openings under such conditions with the primitive chutes of the day would certainly be hazardous.
It is thought that some 200 of the craft were built during the war. They were not common issue to the more than 1100 German U-boats that took to the water, being designed for use primarily in the larger Type IX U-boats. Due to the heavy Allied anti-submarine assets in the North Atlantic the kite could only be used in the more remote parts of the globe, such as the Indian Ocean and South Atlantic, etc. They were also very dangerous to use and exposed the U-boat to a window of nearly and hour to surface, assemble, launch, recover, disassemble and stow the craft before the U-boat could surface again. A number of the primitive craft were captured after the war and they are well represented in no less than 20 collections around the world. The US Navy's more successful DSN-1/QH-50A DASH drone helicopters of the 1950s, which were of a similar size to the Fa-330 but much heavier due to being powered are an direct evolution of the craft.
Sources
U-Boat.net Technical Pages.
National Air and Space Museum Collections Database
Ford, Roger Germany's Secret Weapons in World War Two, 2000 - Brown Books
Ruffin, Steven A Aviation's Most Wanted 2005 - Technology & Engineering
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