Israel’s Urban Aeronautics is ground-testing its unmanned Mule fancraft, an unconventional rotorcraft featuring two shrouded main rotors in tandem configuration that should one day have a manned version for rescue missions in cities. The first untethered flight of the Mule, originally scheduled to take place in the spring, has been postponed until September or October. The company plans to eventually build a larger, 11-passenger fancraft, dubbed the X-Hawk.

The first engine run of the Mule’s Turbomeca Arriel 1D1 turboshaft engine took place in June, with all systems on. Urban Aeronautics previously performed static load tests to check structural integrity and has run powered tests of the rotorcraft’s gearboxes, drive shafts and lift rotors at full speed, using an electric motor. To test the flight control system, the company is flying a smaller, electrically powered Panda Fancraft demonstrator, also remote controlled.

The Mule’s fore and aft six-foot-diameter lift rotors each have five blades. Two smaller shrouded rotors act as thrusters. The aircraft’s architecture enables it to fly in confined areas without the dangers usually associated with open rotors. The fancraft can, for example, operate safely right up to the side of a building.

Urban Aeronautics plans to market the Mule as a logistics-support UAV. “The main interest of such an aircraft is using it on the last leg of a [military] support mission,” chief engineer Mike Turgeman told AIN. He said the most difficult part of such a mission is often the last 10 miles. Although the first applications for the aircraft will be in the military sector, Turgeman believes the civil market will eventually become the main market.

The main drawback of the design is its high fuel burn. “We cannot fight physics,” Turgeman said. “A smaller-diameter rotor translates into a lower efficiency.” The Mule therefore requires 500 pounds of fuel to carry a 500-pound payload on a two-hour mission. Maximum airspeed is 100 knots.

The company’s future plans include the possible development of a manned version of the Mule, so the current design is said to comply with FAR Part 27 rules.