Israeli ducted-fan sky-jeep in flight trials

Published 13 January 2010

Fancraft technology is different from hovercraft technology, because hovercrafts cannot actually fly; fancraft technology involves the use of a basic idea: ducted fans, which are essentially enclosed helicopter rotor discs; until now, the technology faced two problems: small thrust discs mean very low efficiency, leading to aircraft with unacceptably poor fuel endurance and payload even in the context of helicopters; secondly, in the past, the ducted-fan machines were almost impossible to control; an Israeli company says it has solved at least the second problem

Good news for first responders, law enforcement, and soldiers in urban areas. The Israeli designers of a radical flying jeep style VTOL (vertical-take-off-and-landing) “fancraft” have announced flight tests for the invention. The trials of the pilotless AirMule have so far seen the aircraft tethered and restricted to just two feet off the ground.

Fancraft technology – the term is used to distinguish it from hovercraft technology, because hovercrafts cannot actually fly — involves the use of a basic idea: ducted fans, which are essentially enclosed helicopter rotor discs.

Lewis Page writes that it was once thought that ducted-fan aircraft would soon become wide-spread, perhaps serving as military air-jeeps able to flit about easily in urban areas or other restricted terrain which helicopters find tricky to navigate. In the event it was found that small thrust discs mean very low efficiency, leading to aircraft with unacceptably poor fuel endurance and payload even in the context of helicopters. Secondly, in the past, when most of the tests took place, the ducted-fan machines were almost impossible to control.

Engineers at Urban Aeronautics of Israel believe they have solved the second problem. Their fan ducts feature Venetian-blind style arrays of tilting slats, allowing air flow to be redirected without any need to tilt the thrust disc as a normal rotorcraft must. The company’s designers believe that one of their fancraft will be able to hover accurately even in strong, gusty winds while remaining entirely stable and level.

Combining the proprietary slats with modern fly-by-wire automated controls, the Urban Aero researchers contend that their machines will not only be easy to fly, but actually able to fly themselves. The initial AirMule is a crewless design (Page notes that this may be a case of necessity being mother to invention: Urban Aero lacks major backing and unmanned aircraft are seen as cheaper and quicker to develop than manned ones).

A turbine-powered, unmanned AirMule prototype was assembled last year, and Urban Aero executives told Page at last summer’s Paris air show that flight tests could be expected “within two months.” That expectation was not met, but the AirMule, according to an Urban Aero release, has now completed the “first phase of flight testing.”