Urban Aeronautics of Tel Aviv, Isreal has been developing and experimenting with a vertical take-off and landing aircraft called the Cityhawk, their concept demonstrator (shown below-right).

In December 2004 they completed the flight tests of this machine. A total of 10 hover tests were performed, and the data measurements were recorded in real-time for analysis and evaluation. The craft was tested in free flight, without a tether, and performed well in this mode.

They have now completed their analysis of the data, putting special emphasis on control capability in roll. In particular, they wanted to review the performance numbers on their patented vane control system, and were pleased to find a very high degree of effectiveness. Having confirmed their initial estimates, they are now moving forward with the development of their X-Hawk prototype vehicle (above).

The X-Hawk is configured as a tandem-fan, turbine powered vehicle with a center section to house the crew compartment and payload bay. Maximum payload is 1700 lbs including the pilot and 9 seated passengers (calculated at 175 lbs per person). The payload bay can also be configured to serve as a medical rescue cabin.

The lift fans will operate using variable pitch rotors and a rather complex system of vanes. The multiple-vane control system has a U.S. patent and will consist of four separate layers of independently movable vanes in each duct. There will be two layers at the top and two layers at the bottom of each duct. These can be co-ordinated to provide effective lift or side forces. Fore and aft movement is controlled by fully reversible variable-pitch thrusters connected to the two turbine engines.

In addition, the pilot will use a "fly-by-wire" multi-channel flight control system as well as an automatic stabilization feature to help control the aircraft and maintain level flight without tilting the machine. These features will simplify the pilot's workload, allowing him to concentrate on the kind of precise piloting that is required in situations such as rescue missions at high-rise apartments and offices. The vehicle will be fully FAA certified. Even with a full payload, the X-Hawk can still come to a safe landing after the loss of one of the turbines.

Another interesting feature calls for the X-Hawk ducts to be acoustically treated to reduce noise levels. This will help overcome one of the major criticisms that have been made of some powered-lift VTOLs, namely excessive noise.