Flight Path Reconstruction for a Coaxial Helicopter Equipped with Rotational Accelerometers

The flight trajectory of a coaxial rotorcraft during a flight test campaign with dynamic maneuvers has been reconstructed utilizing a Rauch-Tung-Striebel-smoothing and Estimation Before-Modeling approach. The latter also provides time histories for the external forces and moments as well as their time derivatives, which are valuable additional information for flight dynamics analysis, control design, and system identification. Besides the conventional sensors, the rotorcraft was also instrumented with angular accelerometers. The benefits of such sensors on the reconstructed aircraft states, and the external forces and moments are discussed. Sensor errors and model parameters are identified as a byproduct of the flight path reconstruction. A section of the reconstructed trajectory and the estimated sensor model parameters are provided as the basis for the validation and discussion of the applied methods. Furthermore, the paper summarizes the important implementation aspects and practical lessons learned, unique to rotorcraft flight path reconstruction.