Could be a hazard for all the offshore helicopter traffic.
From the Skysail website:
HELICOPTER REPORTS SKYSAILS ON NORTH SEA
Ships fitted with SkySails propulsion have been plying the North and Baltic Seas since early 2006. Since that time, the crews and SkySails testing engineers aboard these ships have reported seeing dozens of helicopters and aircraft, none of which have so far led to any changes in regular flight operations.
On 15 September 2009 at 12:15 UTC, a helicopter deployed to supply a drilling platform sighted the MV “Theseus”, which was located 34 nautical miles from the coast at coordinates 53°37`0 N 04°10`05 E.
In conditions of good visibility, the MV “Theseus” was flying a 160m2 towing kite on a 280-meter-long rope. The towing kite was undergoing routine operations and performing its standard flight maneuvers in the form of a “horizontal figure-eight” at an altitude of 150 to 200 meters off the vessel’s leeward side.
A flight pattern such as this normally covers a width of 250 meters and a height of 50 meters.
The helicopter pilot who spotted the MV “Theseus” was irritated by the SkySails-System and reported a “near miss incident” to Dutch air traffic control.
According to the report of the captain of the MV “Theseus,” the helicopter first flew past the ship’s stern at a great distance and then circled the ship several times. The helicopter maintained adequate distance from the vessel while doing so. No radio contact was established.
SkySails-Systems operate outside the 12-mile limit, i.e. beyond the limits of national jurisdiction under the United Nations Convention on the Law of the Sea (UNCLOS). It is here that the SkySails operate in Class G airspace below 2500 feet (800 m). This is recognized as uncontrolled airspace where visual flight rules (VFR) apply. The SkySails-System is easily recognizable during daylight because of its size and has lighting when flown at night. The system operates within the ship’s safety zone, which low-flying aircraft – including military aircraft – must avoid pursuant to regulations.
