Dornier Spähplattform

The Dornier Spähplattform, German for reconnaissance platform, was a small unmanned tethered helicopter without a drive of its own, developed by Dornier. Before launch the rotor was spun up to high speed and a swirl ring of 20 kilograms stored the energy, so that the device could climb to 50 metres and hover there for about a minute, carrying optical or electronic sensors for close reconnaissance with a range of sight of up to 3,000 metres. It had a four-blade rotor of 1.2 metres diameter with the blades joined at their tips to the ring, a second lighter non-rotating ring below as a landing frame, four stabilising control surfaces and cyclic control that pulled it back when it drifted on the 50 metre cable. The payload of 5 kilograms was first an infrared film camera whose film was developed after landing. The ground station was a trailer with a hydraulic winch and a motor needing about 25 kilowatts to bring the rotor to 4,000 revolutions per minute in a minute. The system met strong interest in 1979 and 1980, but after Daimler-Benz took over Dornier in 1985 the order outlook was too small, the programme ended and the device went to the Deutsches Museum in Munich.