Detection of Forward Flight Limitations of Unmanned Helicopters

In this paper, a method is proposed to determine the flight envelope limitations for steady forward flight with the purpose of performing a flight envelope expansion. First, the rotary wing system is analyzed. In this paper, an intermeshing rotor configuration, a SwissDrones Dragon 50, is used to demonstrate the approach. Next, relevant limitations of the forward flight are reviewed and analyzed with the help of the Helicopter Overall Simulation Tool (HOST). From this analysis, relevant measurement concepts are derived and consequently measurement parameters are defined. Following, a flight test instrumentation is developed including a small-scale rotor telemetry. This instrumentation is tested in flight test. The corresponding flight test program is briefly discussed. It consists of tethered hover flight and a level flight performance test. The results of these flight tests are discussed and used to determine the flight performance limitations encountered.