Extension of the ACT/FHS Experimental Flight Envelope

Abstract

The experimental flight envelope in the low speed corner of the EC135 research helicopter ACT/FHS (Active Control Technology / Flying Helicopter Simulator) is restricted to a safety height of at minimum 15 feet above ground. Present and future research programs demand, however, an experimental operation at lower heights, including take-off and landing. The current experimental envelope is defined in dependence of certified control rate runaway limiters guaranteeing a safe operation when the experimental flight control computer is in the loop. Therefore, the existing runaway limiters have been tuned and in a common effort, the German Aerospace Center (DLR) and Eurocopter Deutschland (ECD), have conducted flight tests with the ACT/FHS helicopter in order to define and verify a new extended experimental flight envelope. Flight test results showed that the tuned runaway limiters, indeed, allow safe experimental operation below 15 feet, including take off and landing, without affecting pilot control authority. After final demonstration the new envelope is certified and approved by the German Aviation Authority (LBA).