Flying ambulance: UAV will extract wounded soldiers from the battlefield

side force or a rolling movement. Front and rear ducts are deflected differentially for yaw. “The VCS generates six degrees of freedom independent of one another. For the first time we have a vehicle that moves sideways without the need to roll,” Rafi Yoeli, founder and CEO of Urban Aeronautics told Eshel.

The company successfully completed the first phase of tethered flight trials, which consisted of autonomous hovers in which the vehicle maintained stable height and attitude. An onboard fly-by-wire system controls pitch, roll, and yaw. The next series of tests will evaluate the AirMule’s position-keeping capability, and the vehicle will fly untethered for the first time.

Eshel offers these details about the craft:

  • The UAV is powered by a 730-shp. Turbomeca Arriel 1D1 turboshaft engine, which drives the fore and aft ducted rotors and aft thrusters through gearboxes and shafts. These propulsion capabilities enable safe flight through areas of dense vegetation, in urban areas, over rough terrain, and at high temperatures.
  • The flight-control developed by Urban Aeronautics is a four-channel redundant system that relies almost entirely on inertial measurements and is augmented by GPS for translational position and velocity readings. Two laser altimeters indicate the vehicle’s height above ground.
  • According to Yoeli, data show that the AirMule will hover with high precision even in gusty wind.
  • The vehicle carries a useful payload of 227 kg. (500 lb.).
  • It has a maximum takeoff weight of 1 ton, and is designed to fly missions of 2-4 hr. at up to 100 kt.
  • Its maximum ceiling is 12,000 ft.
  • An operational version is expected to be available by 2012.

Eshel notes that the concept of ducted-fan technology was popular among aircraft designers in the late 1950s and early 1960s when Piasecki Co. developed ducted-fan vehicles known as “flying jeeps” for the U.S. Army (we used the term “sky jeep” in our 13 January 2010 HSNW article). The configuration was similar to the design used by Urban Aeronautics — two ducts, fore and aft, with a cabin in the middle. That concept, though, was ahead of the technology needed to develop a viable aircraft. The flying jeeps were difficult to control and had little endurance — only about 20 minutes. Eshel writes that because of this, vertical takeoff and landing (VTOL) remained a feature exclusive to helicopters. “An array of technologies that have evolved since — efficient, lightweight engines, composite materials, and flight-control computers — solved most of the problems associated with ducted-fan vehicles,” he writes. “What remained were aerodynamic challenges, notably in the areas of drag and controllability.” Urban Aeronautics patented a package of innovations that reportedly resolves these problems.

 

The company is working on two other unmanned applications of the Fancraft technology — Panda, a small, electrically powered surveillance UAV, and Mule, a mid-sized UAV with a 500-lb. payload capacity.